Quiet Gitea prebuilt fallback

Implicit sessions (dosh host with no --session) get a random
term-<millis>-<pid> name you can never reattach to, so persisting them just
left unreattachable holder processes lingering across restarts. The server
now only uses a persistent holder for prewarmed or explicitly-named
sessions; implicit ones use the in-process shell that dies on restart and
reaps on disconnect, as before. Adds a shared
protocol::{generate,is}_implicit_session_name as the single source of truth
for the name shape, used by both client (generate) and server (detect).

Server-only behavior change; wire VERSION unchanged.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.github/workflows/ci.yml

@@ -3,6 +3,9 @@ name: ci
 on:
   push:
   pull_request:
+  workflow_dispatch:
+  schedule:
+    - cron: "17 7 * * 1"
 
 jobs:
   test:
@@ -19,6 +22,59 @@ jobs:
       - name: Docker SSH benchmark gate
         run: sh scripts/ci-docker-ssh-bench.sh
 
+  fuzz-smoke:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Install nightly toolchain
+        id: nightly
+        continue-on-error: true
+        uses: dtolnay/rust-toolchain@nightly
+      - name: Install cargo-fuzz
+        id: install
+        if: steps.nightly.outcome == 'success'
+        continue-on-error: true
+        run: cargo install cargo-fuzz --locked
+      - name: Run fuzz targets briefly
+        if: steps.nightly.outcome == 'success' && steps.install.outcome == 'success'
+        run: |
+          set -e
+          if [ "${{ github.event_name }}" = "schedule" ] || [ "${{ github.event_name }}" = "workflow_dispatch" ]; then
+            DOSH_FUZZ_SECONDS="${DOSH_FUZZ_SECONDS:-300}" sh scripts/fuzz-run.sh
+          else
+            sh scripts/fuzz-run.sh 20
+          fi
+      - name: Note when fuzzing was skipped
+        if: steps.nightly.outcome != 'success' || steps.install.outcome != 'success'
+        run: echo "cargo-fuzz / nightly toolchain unavailable; skipped fuzz smoke run."
+
+  package-release:
+    if: github.event_name == 'workflow_dispatch' || startsWith(github.ref, 'refs/tags/')
+    strategy:
+      matrix:
+        include:
+          - os: ubuntu-latest
+            name: linux-x86_64
+          - os: macos-14
+            name: macos-aarch64
+          - os: macos-13
+            name: macos-x86_64
+          - os: windows-latest
+            name: windows-x86_64
+    runs-on: ${{ matrix.os }}
+    steps:
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@stable
+      - name: Package release
+        shell: bash
+        run: sh scripts/package-release.sh
+      - uses: actions/upload-artifact@v4
+        with:
+          name: dosh-${{ matrix.name }}
+          path: |
+            target/dosh-release/dosh-*
+            !target/dosh-release/stage/**
+
   remote-bench:
     runs-on: ubuntu-latest
     env:

Cargo.lock

@@ -397,6 +397,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e7c1832837b905bbfb5101e07cc24c8deddf52f93225eee6ead5f4d63d53ddcb"
 dependencies = [
  "const-oid",
+ "pem-rfc7468",
  "zeroize",
 ]
 
@@ -448,11 +449,14 @@ dependencies = [
  "ed25519-dalek",
  "hkdf",
  "hmac",
+ "libc",
  "portable-pty",
  "rand",
  "rpassword",
+ "rsa",
  "serde",
  "sha2",
+ "signature",
  "ssh-key",
  "tempfile",
  "tokio",
@@ -1498,6 +1502,7 @@ checksum = "3b86f5297f0f04d08cabaa0f6bff7cb6aec4d9c3b49d87990d63da9d9156a8c3"
 dependencies = [
  "bcrypt-pbkdf",
  "ed25519-dalek",
+ "num-bigint-dig",
  "p256",
  "p384",
  "p521",

Cargo.toml

@@ -16,12 +16,15 @@ dirs = "5.0"
 ed25519-dalek = "2.1"
 hkdf = "0.12"
 hmac = "0.12"
+libc = "0.2"
 portable-pty = "0.8"
 rand = "0.8"
+rsa = { version = "0.9.10", features = ["sha2"] }
 rpassword = "7.5.4"
 serde = { version = "1.0", features = ["derive"] }
 sha2 = "0.10"
-ssh-key = { version = "0.6.7", features = ["ed25519", "encryption"] }
+signature = "2.2"
+ssh-key = { version = "0.6.7", features = ["ed25519", "encryption", "p256", "rsa"] }
 tokio = { version = "1.41", features = ["full"] }
 toml = "0.8"
 vt100 = "0.15"

Makefile

@@ -1,4 +1,4 @@
-.PHONY: build test fmt install bench-local bench-docker-ssh bench-docker-mosh
+.PHONY: build test fmt install package-release bench-report bench-local bench-local-json bench-docker-ssh bench-docker-mosh fuzz-smoke fuzz-deep soak-local
 
 build:
 	cargo build --release
@@ -12,17 +12,36 @@ fmt:
 install:
 	sh packaging/install.sh
 
+package-release:
+	sh scripts/package-release.sh
+
+bench-report:
+	sh scripts/bench-report.sh
+
+# Safe, self-contained local benchmark matrix (native cold auth, cached attach
+# ticket, local-auth) on a throwaway server bound to 127.0.0.1 on a free port in
+# a temp HOME. Never touches the production server or UDP port 50000.
 bench-local:
-	cargo build
-	tmp="$$(mktemp -d)"; \
-	HOME="$$tmp" target/debug/dosh-server serve >/tmp/dosh-bench-server.log 2>&1 & \
-	pid="$$!"; \
-	trap 'kill "$$pid" 2>/dev/null || true; rm -rf "$$tmp"' EXIT INT TERM; \
-	sleep 0.5; \
-	HOME="$$tmp" target/debug/dosh-bench --local-auth --server local --iterations 5
+	sh scripts/bench-local.sh
+
+# Same matrix, machine-readable JSON output (one object per metric with raw
+# samples). Useful for publishing or regression tracking.
+bench-local-json:
+	DOSH_BENCH_JSON=1 sh scripts/bench-local.sh
 
 bench-docker-ssh:
 	sh scripts/ci-docker-ssh-bench.sh
 
 bench-docker-mosh:
 	DOSH_BENCH_INCLUDE_MOSH=1 sh scripts/ci-docker-ssh-bench.sh
+
+fuzz-smoke:
+	sh scripts/fuzz-run.sh 20
+
+# Longer pre-launch fuzz pass. Override with DOSH_FUZZ_SECONDS=NN.
+fuzz-deep:
+	DOSH_FUZZ_SECONDS=$${DOSH_FUZZ_SECONDS:-300} sh scripts/fuzz-run.sh
+
+# 30-minute launch soak by default. Override with DOSH_SOAK_SECONDS=NN.
+soak-local:
+	DOSH_SOAK_SECONDS=$${DOSH_SOAK_SECONDS:-1800} cargo test --test integration_smoke sleep_roaming_soak_30m -- --ignored --nocapture

README.md

@@ -81,6 +81,9 @@ dosh-server
   client table per session
   encrypted UDP protocol
   tiny SSH-invoked dosh-auth helper mode
+  persistent sessions (persist_sessions, currently opt-in): each shell runs in a
+    detached per-session holder process; the server adopts its PTY master fd via
+    SCM_RIGHTS and re-adopts it after a restart, so sessions survive crash/upgrade
 
 dosh-client
   terminal raw mode
@@ -107,41 +110,54 @@ Install the client on macOS:
 
 ```bash
 curl -fsSL https://git.palav.dev/Palav/dosh/raw/branch/main/install.sh \
-  | DOSH_REPO=https://git.palav.dev/Palav/dosh.git DOSH_SERVER=palav DOSH_HOST=git.palav.dev DOSH_PORT=50000 sh -s -- client
+  | DOSH_REPO=https://git.palav.dev/Palav/dosh.git DOSH_PORT=50000 sh -s -- client
 ```
 
 Update an installed client later:
 
 ```bash
 dosh update
+dosh update --check
+dosh --version
 ```
 
+`dosh update` first tries a release tarball named for the platform
+(`dosh-macos-aarch64.tar.gz`, `dosh-linux-x86_64.tar.gz`, etc.) from the latest
+Gitea/GitHub release. If that asset is not published yet, it falls back to the
+source build path. If the release also publishes `<artifact>.sha256`, the installer
+verifies the archive before installing it.
+
 Install the client on Windows PowerShell:
 
 ```powershell
-$env:DOSH_REPO="https://git.palav.dev/Palav/dosh.git"; $env:DOSH_SERVER="palav"; $env:DOSH_HOST="git.palav.dev"; $env:DOSH_PORT="50000"; irm https://git.palav.dev/Palav/dosh/raw/branch/main/install.ps1 | iex
+$env:DOSH_REPO="https://git.palav.dev/Palav/dosh.git"; $env:DOSH_PORT="50000"; irm https://git.palav.dev/Palav/dosh/raw/branch/main/install.ps1 | iex
 ```
 
 Attach:
 
 ```bash
-dosh palav
+dosh user@server.example.com
 ```
 
-Plain `dosh palav` opens a fresh terminal session. Use named sessions when you want
-to reattach to the same persistent terminal from multiple clients:
+Plain `dosh user@server.example.com` opens a fresh terminal session. Use named
+sessions when you want to reattach to the same persistent terminal from multiple
+clients:
 
 ```bash
-dosh --session work palav
-dosh --session logs palav
+dosh --session work user@server.example.com
+dosh --session logs user@server.example.com
 ```
 
 Press `Ctrl-]` to detach the current client while leaving the server session alive.
 Typing `exit` in the remote shell closes that Dosh session and returns the client.
 If UDP packets stop arriving, Dosh keeps the terminal open, sends keepalive pings,
-and attempts ticket-based reconnect. The old in-band status overlay was removed
-because writing directly over the terminal could corrupt TUIs; a non-destructive
-status surface is tracked as a public-readiness item.
+and attempts ticket-based reconnect. While the link is silent it shows a single,
+non-destructive status line on the bottom screen row (`[dosh] last contact Ns ago
+— reconnecting…`), drawn with save/restore cursor so it never moves the app cursor
+or corrupts a full-screen TUI, and cleared the instant packets resume. (The old
+in-band overlay wrote over the active line and could corrupt TUIs; this draws only
+the last row.) Disable it with `disconnect_status = false` in `client.toml` or
+`DOSH_DISCONNECT_STATUS=0`.
 
 If SSH and UDP use different public names, specify the UDP address:
 
@@ -155,7 +171,31 @@ UDP host from an SSH alias when `dosh_host` is not configured. To make that expl
 in Dosh's host config:
 
 ```bash
-dosh import-ssh palav homelab
+dosh import-ssh homelab
+dosh homelab
+```
+
+Optional command extensions are just config-side startup shortcuts; Dosh has no
+compile-time dependency on the tools they run. For example, to make a separately
+installed server-side `tm` dashboard easy to open:
+
+```toml
+# ~/.config/dosh/client.toml
+[extensions.tm]
+command = "tm {args}"
+description = "Open the server-side tmux dashboard"
+```
+
+Then `dosh homelab tm` sends `tm`, and `dosh homelab tm dosh` sends `tm 'dosh'`.
+Remove that table to remove the integration. Hosts can override or opt out:
+
+```toml
+# ~/.config/dosh/hosts.toml
+[homelab.extensions.tm]
+command = "/opt/tm/bin/tm {args}"
+
+[other-host.extensions.tm]
+disabled = true
 ```
 
 ## Develop
@@ -190,9 +230,9 @@ Benchmark the ControlMaster-backed SSH bootstrap path:
 target/release/dosh-bench --server user@host --controlmaster --iterations 3
 ```
 
-Run the Docker OpenSSH benchmark gate used by CI. It checks both cold SSH bootstrap
-and ControlMaster-backed SSH bootstrap against a containerized `sshd` plus resident
-`dosh-server`:
+Run the Docker OpenSSH benchmark gate used by CI. It checks cold SSH bootstrap,
+ControlMaster-backed SSH bootstrap, native cold auth after one-time `dosh trust`,
+and cached attach against a containerized `sshd` plus resident `dosh-server`:
 
 ```bash
 make bench-docker-ssh
@@ -204,12 +244,39 @@ Run the same Docker comparison with Mosh installed in the benchmark container:
 make bench-docker-mosh
 ```
 
-That prints `ssh_true_ms`, `dosh_attach_ms`, and `mosh_start_true_ms` under the same
-container, key, DNS, and network path. It also prints `dosh_cached_attach_ms`, which
-is the real Dosh fast path after the first SSH-authenticated bootstrap has issued an
-attach ticket. See `docs/PUBLIC_READINESS.md` before using the numbers publicly;
-Dosh's current strongest claim is fast attach/reconnect, not full Mosh feature
-parity yet.
+That prints `ssh_true_ms`, `dosh_attach_ms`, `dosh_cold_native_ms`,
+`dosh_cached_attach_ms`, and, for the Mosh target, `mosh_start_true_ms` under the
+same container, key, DNS, and network path. `dosh_cached_attach_ms` is the real Dosh
+fast path after the first authentication has issued an attach ticket. See
+`docs/PUBLIC_READINESS.md` before using the numbers publicly; Dosh's current
+strongest claim is fast attach/reconnect plus native encrypted forwarding on
+Dosh-installed servers, not generic SSH compatibility.
+
+The latest local release evidence is in
+`docs/RELEASE_EVIDENCE_2026-06-20.md`.
+
+Generate a publishable Markdown benchmark report:
+
+```bash
+make bench-report
+```
+
+Set `DOSH_BENCH_SERVER`, `DOSH_BENCH_ITERS`, `DOSH_BENCH_ARGS`, and
+`DOSH_BENCH_REPORT` to target a real host and choose the output path.
+
+Run the explicit pre-launch soak and fuzz gates:
+
+```bash
+make soak-local                 # 30-minute sleep/roaming gate by default
+make fuzz-deep                  # 5 minutes per fuzz target by default
+```
+
+Both are configurable for shorter local shakedowns:
+
+```bash
+DOSH_SOAK_SECONDS=30 make soak-local
+DOSH_FUZZ_SECONDS=60 make fuzz-deep
+```
 
 The CI workflow includes an optional remote benchmark job. It runs when
 `DOSH_BENCH_HOST`, `DOSH_BENCH_USER`, and `DOSH_BENCH_SSH_KEY` repository secrets are
@@ -221,6 +288,13 @@ Install release binaries and the user systemd service:
 make install
 ```
 
+Build release tarballs for upload to Gitea/GitHub releases:
+
+```bash
+make package-release
+GITEA_TOKEN=... scripts/upload-gitea-release.sh v0.1.0 target/dosh-release/dosh-*
+```
+
 ## Performance Rules
 
 The stack is performance-driven, not fixed by taste. Rust is the default because the
@@ -255,7 +329,8 @@ Hot-path rules:
 
 - Replacing SSH as the first public-key trust mechanism.
 - Multi-user access control.
-- Windows support in v0.
+- Windows server/full parity in v0; the client installer supports prebuilt Windows
+  client artifacts when published.
 - Full mosh compatibility.
 - Perfect predictive local echo in the first MVP.
 
@@ -267,3 +342,41 @@ resident PTY server, encrypted UDP bootstrap attach, UDP resume, sealed UDP atta
 tickets, client ACKs, server retransmit bookkeeping, sliding replay protection,
 server-side `vt100` screen snapshots/diffs, a hardened user systemd unit, an install
 script, Docker SSH benchmark gates, CI, and protocol/integration tests.
+
+### Native v1
+
+Beyond the SSH-bootstrap core, native v1 (`docs/NATIVE_V1_SPEC.md`) is substantially
+implemented and aims to replace the day-to-day `ssh host` workflow on Dosh-installed
+servers:
+
+- **Native UDP auth** with X25519 key exchange; transcript-bound Ed25519, ECDSA
+  P-256, and RSA-SHA2 user auth via ssh-agent or OpenSSH identity files;
+  ChaCha20-Poly1305 transport; and `authorized_keys` policy enforcement (`from=`,
+  `no-port-forwarding`, `permitopen=`; unsupported options fail closed).
+- **Dosh host-key trust**: pinned `known_hosts`, `dosh trust [--remove|--replace]`,
+  TOFU only when explicitly enabled, and hard-fail on host-key mismatch.
+- **TCP forwarding**: local `-L`, remote `-R` (loopback bind by default), dynamic
+  SOCKS5 `-D`, forward-only `-N`, and background `-f`, with per-stream flow control so
+  bulk transfers do not lag the terminal.
+- **Agent forwarding** (opt-in, security-gated): `-A` / `forward_agent` exports your
+  local `SSH_AUTH_SOCK` to a per-session proxy socket on the server (private dir,
+  mode 0600) and tunnels each connection back to your agent over a Dosh stream. Only
+  active on explicit client opt-in **and** server `allow_agent_forwarding = true`; it
+  applies to freshly spawned shells (not an already-running attached/prewarmed
+  session, the same constraint ssh/mosh have).
+- **Diagnostics**: `dosh doctor host` for config/auth/UDP/forwarding-policy checks.
+
+Native auth is **opt-in alongside SSH fallback** (`auth_preference = "native,ssh"`):
+the native authenticated path is tried first and falls back to SSH bootstrap
+explicitly when native auth is disabled, unavailable, or rejected. It never silently
+degrades to an unauthenticated mode.
+
+Native v1 is **not externally audited yet**. Local 30-minute sleep/roaming soak,
+fuzz-smoke, and Docker SSH/Mosh benchmark evidence is captured in
+`docs/RELEASE_EVIDENCE_2026-06-20.md`. See `docs/THREAT_MODEL.md` for the
+published threat model and accepted residual risks, `docs/PROTOCOL_VERSIONING.md`
+for the v1 versioning policy, `docs/AUDIT_PACKET.md` for the external security
+review handoff, and the "Native v1 verification checklist status" table in
+`docs/PUBLIC_READINESS.md` for the item-by-item state. Dosh does not claim generic
+SSH compatibility; its defensible claim is fast encrypted native attach/reconnect
+and forwarding on Dosh-installed servers with SSH bootstrap fallback.

SPEC.md

@@ -4,7 +4,8 @@
 **Default language:** Rust, unless benchmarks prove the stack is the bottleneck  
 **Binaries:** `dosh-server`, `dosh-client`, `dosh-auth`, `dosh-bench`  
 **Helper mode:** `dosh-server auth` or `~/.local/bin/dosh-auth`, invoked by SSH with `-T`  
-**Native v1 plan:** `docs/NATIVE_V1_SPEC.md`
+**Native v1 plan:** `docs/NATIVE_V1_SPEC.md` (substantially implemented; see its v1 status block)  
+**Threat model:** `docs/THREAT_MODEL.md`
 
 ---
 
@@ -157,8 +158,11 @@ owner per session is preferred. Cross-thread designs are allowed only if benchma
 
 ## 7. Security Model
 
-SSH is the first trust root. dosh does not implement a competing public-key login
-system in v0.
+SSH is the first trust root and the recovery/bootstrap fallback. The v0 core relies
+on SSH for first authentication. Native v1 (`docs/NATIVE_V1_SPEC.md`) adds an opt-in
+native public-key login over the Dosh UDP transport that is tried before SSH, with
+its assets, attackers, and residual risks documented in `docs/THREAT_MODEL.md`. SSH
+remains the explicit fallback and the host-key trust bootstrap path.
 
 The UDP channel uses AEAD. Recommended default: `ChaCha20-Poly1305` for portable
 speed, with `AES-GCM` allowed when hardware acceleration is known to be available.
@@ -464,6 +468,8 @@ dosh_port = 50000
 default_session = "new"
 reconnect_timeout_secs = 5
 view_only = false
+predict = true
+predict_mode = "experimental"
 cache_attach_tickets = true
 credential_cache = "~/.local/share/dosh/credentials"
 ```

docs/AUDIT_PACKET.md

@@ -0,0 +1,75 @@
+# Dosh Native v1 Audit Packet
+
+This is the handoff checklist for an external security review.
+
+## Scope
+
+Review the security properties of Dosh native v1:
+
+- Native UDP authentication and key exchange
+- Host key trust and known-host mismatch behavior
+- Authorized key parsing and policy enforcement
+- Transport encryption, replay protection, rekeying, resume, and stale packet handling
+- Attach ticket sealing/opening
+- TCP forwarding and agent forwarding authorization boundaries
+- Parser robustness for untrusted wire/config data
+
+Primary files:
+
+- `src/native.rs`
+- `src/protocol.rs`
+- `src/auth.rs`
+- `src/ssh_agent.rs`
+- `src/bin/dosh-client.rs`
+- `src/bin/dosh-server.rs`
+- `src/config.rs`
+- `tests/parser_robustness.rs`
+- `tests/protocol_auth.rs`
+- `tests/hostile_network.rs`
+- `tests/integration_smoke.rs`
+- `fuzz/fuzz_targets/*`
+
+Primary docs:
+
+- `docs/NATIVE_V1_SPEC.md`
+- `docs/THREAT_MODEL.md`
+- `docs/PROTOCOL_VERSIONING.md`
+- `docs/PUBLIC_READINESS.md`
+- `docs/RELEASE_EVIDENCE_2026-06-20.md`
+
+## Required Reviewer Questions
+
+1. Is the native handshake transcript complete enough to bind client/server keys,
+   requested session, mode, env, and forwarding permissions?
+2. Are host-key trust transitions fail-closed, especially unknown vs mismatch vs
+   explicit TOFU?
+3. Are authorized-key options parsed conservatively enough, and are unsupported
+   options rejected safely?
+4. Can replayed, reordered, delayed, stale, or cross-epoch packets affect terminal
+   input or forwarded streams more than once?
+5. Does key rotation preserve confidentiality without creating split-brain epoch
+   states?
+6. Do attach tickets create any bearer-token replay or privilege-extension issue?
+7. Can UDP endpoint migration be abused for hijack or reflection?
+8. Are local/remote/dynamic TCP forwarding and agent forwarding gated correctly by
+   client opt-in, server config, and authorized-key options?
+9. Are parser and packet-size limits sufficient against malicious inputs?
+10. Are there any unsafe assumptions in process/session persistence or holder
+    adoption?
+
+## Current Local Evidence
+
+As of 2026-06-20:
+
+- `cargo test`: `153 passed, 1 ignored`
+- `make soak-local`: passed 30-minute sleep/roaming soak
+- `make fuzz-smoke`: passed all configured fuzz targets for 20s each
+- `make bench-docker-mosh`: passed SSH, ControlMaster, native, cached, and Mosh
+  comparison gates
+
+## Explicit Non-Claims Before Audit
+
+- No claim of generic SSH protocol replacement.
+- No claim of full Mosh compatibility.
+- No claim that native v1 is externally audited.
+- No claim that Windows server support is production-ready.

docs/BENCHMARKS.md

@@ -0,0 +1,203 @@
+# Dosh Benchmarks
+
+This document explains how to run the Dosh benchmarks, what each metric means,
+and how to read the results honestly. Dosh's headline claim is *insane speed on
+repeat attach/reconnect* — these benchmarks exist to make that claim measurable
+and reproducible.
+
+> **Read first:** `docs/PUBLIC_READINESS.md`. The defensible public claim is fast
+> attach/reconnect, not full Mosh feature parity, and **not** cold startup. Cite
+> `dosh_cached_attach_ms` for the core speed claim; cite cold metrics only to show
+> the fallback path stays competitive with ordinary SSH.
+
+## TL;DR
+
+```bash
+make bench-local          # safe, self-contained matrix on a throwaway server
+make bench-local-json     # same, machine-readable JSON with raw samples
+make bench-docker-ssh     # containerized SSH-vs-Dosh gate used by CI
+make bench-docker-mosh    # same, with Mosh installed for a three-way comparison
+make bench-report         # Markdown report wrapper around dosh-bench
+```
+
+`make bench-local` never touches a running production server: it builds release
+binaries, starts its own `dosh-server` bound to `127.0.0.1` on a random free UDP
+port inside a temporary `HOME`, runs the matrix, prints raw samples plus summary
+statistics, and tears everything down on exit. It will refuse to bind UDP port
+`50000` (the default production port).
+
+## The benchmark binary: `dosh-bench`
+
+`dosh-bench` spawns the real `dosh-client` once per iteration and times the whole
+process from launch to terminal-ready-and-detached. That wall-clock cost is the
+apples-to-apples comparison against `ssh host true`: it is the startup price each
+tool pays before any useful remote work begins.
+
+Every run prints, per metric, a summary line (count, min, median, p95, mean, max
+in milliseconds) **and** a raw-samples line. Pass `--json` for one machine-readable
+object per run (with the full `samples_ms` array) so published numbers can always
+include raw data, as required by `docs/PUBLIC_READINESS.md`. Pass `--markdown` for a
+publishable Markdown table, and `--output path/to/report.md` to write it to disk.
+
+### Path matrix
+
+`dosh-bench` can benchmark these Dosh attach paths. Without an explicit path flag
+it keeps its legacy single-path behavior (driven by `--local-auth` / `--warm-cache`
+/ `--no-cache`) so existing CI scripts keep working.
+
+| Flag | Metric | What it measures |
+| --- | --- | --- |
+| `--cold-native` | `dosh_cold_native_ms` | Native cold auth: full `--auth native --no-cache` handshake to first frame and detach. The cold fallback when no cache exists. |
+| `--cached-ticket` | `dosh_cached_attach_ms` | Cached attach-ticket fast path. Warms the cache once, then measures repeat attaches using cached UDP credentials/tickets. **This is the core speed claim.** |
+| `--resume` | `dosh_resume_ms` | UDP resume of a session whose endpoint changes. See the caveat below — only meaningful when a live session is kept open out-of-band. |
+| `--local-auth` | `dosh_local_attach_ms` | Self-contained local bootstrap; no SSH, no native handshake. Useful as a lower-bound sanity check on loopback. |
+| *(default, no flag)* | `dosh_attach_ms` | Cold SSH bootstrap plus UDP attach (legacy single-path mode). |
+
+Existing baseline/comparison metrics are unchanged:
+
+| Metric | Meaning |
+| --- | --- |
+| `ssh_true_ms` | `ssh host true` with the same key/options. |
+| `mosh_start_true_ms` | `mosh host -- true` bootstrap, run `true`, exit (timed inside a PTY). |
+
+### Assertions / gates
+
+| Flag | Gate |
+| --- | --- |
+| `--assert-ssh-plus-ms N` | The primary Dosh metric must be ≤ `ssh_true_ms` mean + `N` ms. |
+| `--assert-mosh-minus-ms N` | The primary Dosh metric must be at least `N` ms faster than `mosh_start_true_ms`. |
+| `--assert-dosh-max-ms N` | The primary Dosh metric mean must be ≤ `N` ms. |
+
+The "primary Dosh metric" for assertions is, in priority order:
+`dosh_cached_attach_ms` → `dosh_resume_ms` → `dosh_cold_native_ms` →
+`dosh_attach_ms` → `dosh_local_attach_ms`.
+
+## What each benchmark does
+
+### `make bench-local` (`scripts/bench-local.sh`)
+
+Self-contained, no SSH, no Docker. It:
+
+1. Builds release binaries (`DOSH_BENCH_PROFILE=debug` for the debug profile).
+2. Picks a free UDP port (never `50000`) and a temp `HOME`.
+3. Generates a throwaway client identity (`ssh-keygen`), authorizes it on the
+   server, and writes a throwaway server + client config (native auth,
+   trust-on-first-use, localhost UDP).
+4. Starts `dosh-server serve` bound to `127.0.0.1` on that port.
+5. Runs `dosh-bench --cold-native --cached-ticket`, then `--local-auth --no-cache`.
+6. Sanity-checks that native cold auth actually trusted the host (so a silent
+   config-parse fallback can't make the benchmark measure the wrong path).
+7. Kills the server and removes the temp `HOME` on exit.
+
+Tunables: `scripts/bench-local.sh [ITERATIONS]` (default 20), `DOSH_BENCH_JSON=1`,
+`DOSH_BENCH_PROFILE=release|debug`.
+
+### `make bench-docker-ssh` / `make bench-docker-mosh` (`scripts/ci-docker-ssh-bench.sh`)
+
+Builds one Ubuntu image with OpenSSH, `dosh-server`, `dosh-auth` (and Mosh for the
+`-mosh` target), then runs `ssh_true_ms`, cold + ControlMaster SSH-bootstrap
+`dosh_attach_ms`, one-time `dosh trust` followed by native-cold
+`dosh_cold_native_ms`, `dosh_cached_attach_ms`, and optionally
+`mosh_start_true_ms` against the same container, key, and loopback network path.
+This is the gate CI enforces; it asserts cold SSH-bootstrap Dosh stays within
+500 ms of SSH, native-cold Dosh beats SSH mean by default, and cached attach stays
+under a small budget. See `README.md` "Develop" for the exact invocations.
+
+## Methodology and caveats
+
+- **Same machine, same network path.** `bench-local` runs everything on loopback,
+  so it isolates Dosh's own process/handshake/render overhead and removes network
+  RTT from the comparison. Real-world cached attach is approximately *network RTT
+  plus the local overhead these numbers measure*. Publish the machine, OS, CPU,
+  network path, and sample count alongside any numbers.
+- **Wall-clock of the whole client process.** Each sample includes process spawn,
+  attach, first-frame render, and detach. That is deliberately the same thing
+  `ssh host true` pays, but it means a few ms is fixed process-startup cost, not
+  protocol cost.
+- **Do not cite cold metrics as the headline.** `dosh_cold_native_ms` and
+  `dosh_attach_ms` still pay first-authentication cost. They exist to show the
+  fallback path stays competitive with ordinary SSH. Cite `dosh_cached_attach_ms`
+  for repeat attach/reconnect, per `docs/PUBLIC_READINESS.md`.
+- **UDP resume is the roaming path, not cold reconnect.** Resume reconnects a
+  client that is *still attached* when its network endpoint changes (sleep/Wi-Fi
+  switch). The `--attach-only` benchmark model detaches after every iteration,
+  which removes the client on the server, so a fresh-process resume has nothing
+  live to resume and is not meaningful in `bench-local`. The cold fresh-process
+  reconnect fast path is the attach ticket (`dosh_cached_attach_ms`). Roaming
+  resume correctness is covered by the integration test
+  `resume_updates_udp_endpoint_for_roaming` in `tests/integration_smoke.rs`.
+  `dosh-bench --resume` remains available for scenarios that keep a live session
+  open out-of-band (for example remote soak tests).
+- **These are not identical workloads.** SSH/Mosh/Dosh do different work at
+  startup. The comparison is still useful because it measures the startup tax each
+  tool charges before useful remote work begins.
+
+## Sample results (loopback, self-contained)
+
+Captured with `make bench-local` (`scripts/bench-local.sh 20`), all times in
+milliseconds, 20 samples per metric.
+
+- Machine: Intel Core i5-9500 @ 3.00 GHz, 6 cores
+- OS: Ubuntu 24.04.4 LTS, Linux 6.8.0-124-generic, x86_64
+- Toolchain: rustc 1.96.0, release profile
+- Network path: loopback (`127.0.0.1`), throwaway server on a free UDP port
+- Workload: `dosh-client --attach-only` to first frame and detach
+
+| Metric | n | min | median | p95 | mean | max |
+| --- | --- | --- | --- | --- | --- | --- |
+| `dosh_cold_native_ms` | 20 | 8.32 | 8.77 | 9.34 | 8.82 | 9.52 |
+| `dosh_cached_attach_ms` | 20 | 2.83 | 3.23 | 3.75 | 3.24 | 3.77 |
+| `dosh_local_attach_ms` | 20 | 2.84 | 3.21 | 3.96 | 3.28 | 3.98 |
+
+Raw samples (ms):
+
+```
+dosh_cold_native_ms:
+8.82, 8.60, 8.69, 8.71, 9.33, 8.82, 8.90, 8.64, 8.39, 8.75, 8.79, 8.70, 8.64,
+9.52, 8.72, 8.32, 9.06, 8.93, 8.96, 9.04
+
+dosh_cached_attach_ms:
+3.04, 3.06, 2.98, 2.91, 2.96, 2.95, 3.05, 3.66, 3.37, 2.88, 2.83, 3.16, 3.49,
+3.30, 3.77, 3.32, 3.49, 3.75, 3.56, 3.33
+
+dosh_local_attach_ms:
+3.08, 3.96, 3.36, 3.30, 2.88, 2.99, 3.96, 3.98, 3.25, 2.84, 3.29, 3.59, 3.65,
+3.47, 3.13, 2.92, 2.87, 2.91, 2.98, 3.18
+```
+
+Reading these numbers: cold native auth is ~9 ms because it pays the native
+handshake; cached attach is ~3 ms because it reuses cached credentials and skips
+the handshake entirely. On loopback there is no network RTT, so this is the local
+overhead floor. Over a real link, expect cached attach ≈ this floor + one network
+round trip — which is exactly the "near network RTT" target in the spec. There is
+no SSH/Mosh baseline in this loopback table because those paths need an SSH server;
+use `make bench-docker-ssh` / `make bench-docker-mosh` for the head-to-head.
+
+## Sample results (Docker SSH/Mosh comparison)
+
+Captured with `make bench-docker-mosh`, all times in milliseconds. This is the
+same-container comparison gate: one generated key, one OpenSSH server, one
+`dosh-server`, loopback-published TCP/UDP ports.
+
+| Metric | n | min | median | p95 | mean | max |
+| --- | --- | --- | --- | --- | --- | --- |
+| `ssh_true_ms` (cold SSH baseline for native-cold gate) | 5 | 214.53 | 216.84 | 220.55 | 217.60 | 220.91 |
+| `dosh_cold_native_ms` | 5 | 8.62 | 8.96 | 9.78 | 9.15 | 9.88 |
+| `dosh_cached_attach_ms` | 10 | 8.41 | 8.83 | 9.52 | 8.90 | 9.53 |
+| `mosh_start_true_ms` | 3 | 528.03 | 530.87 | 539.23 | 533.02 | 540.16 |
+
+Raw samples (ms):
+
+```
+ssh_true_ms (native-cold gate):
+216.84, 216.61, 214.53, 220.91, 219.09
+
+dosh_cold_native_ms:
+9.39, 8.88, 8.96, 8.62, 9.88
+
+dosh_cached_attach_ms:
+8.44, 8.41, 8.80, 8.48, 9.53, 9.51, 8.85, 8.69, 9.33, 8.96
+
+mosh_start_true_ms:
+540.16, 528.03, 530.87
+```

docs/NATIVE_V1_SPEC.md

@@ -1,5 +1,36 @@
 # Dosh Native v1 Spec
 
+> **v1 status (annotation, not part of the spec text below).** Native v1 is
+> substantially implemented and being stabilized; it is not yet fully verified.
+> Milestone progress against section 15:
+>
+> - Milestone 1 — host identity and trust: **done.** Host key generation, `dosh trust`,
+>   `known_hosts`, and mismatch hard-fail are implemented.
+> - Milestone 2 — native user auth: **done.** `ClientHello`/`ServerHello`/`UserAuth`/
+>   `AuthOk`, ssh-agent and OpenSSH identity-file auth for Ed25519, ECDSA P-256,
+>   and RSA-SHA2, plus `authorized_keys` verification, exist.
+> - Milestone 3 — default native auth: **done.** `auth_preference = "native,ssh"` is
+>   the default with explicit, visible SSH fallback. Local and Docker benchmark gates
+>   cover cached attach, SSH fallback, and native cold auth (Track C /
+>   `BENCHMARKS.md`).
+> - Milestone 4 — forwarding: **implemented.** Stream mux, `-L`, `-R`, `-D`, `-N`,
+>   `-f`, per-stream flow control, ordered stream offsets/ACKs, and stream-data
+>   retransmission exist. Terminal-priority/load, replay/reorder, and dropped
+>   server-to-client `StreamData` recovery regressions are covered.
+> - Milestone 5 — hardening: **partly done.** Per-IP token-bucket rate limiting,
+>   fail-closed protocol-version checks with a documented v1 policy, parser fuzz
+>   targets, fuzz-smoke/deep CI entry points, scripted TUI transport tests,
+>   forwarding load/priority/replay/loss tests, and independent persistent session
+>   restart tests exist. Published long-soak evidence is not yet complete. The threat
+>   model is published (`docs/THREAT_MODEL.md`).
+> - Milestone 6 — workflow parity: **mostly done.** `dosh doctor`, host-trust
+>   management, and the encrypted-key prompt flow exist; cross-OS daily-driver soak is
+>   ongoing.
+>
+> The section 16 verification checklist is **not yet fully green** — see the
+> item-by-item status table in `docs/PUBLIC_READINESS.md` and the residual-risk list in
+> `docs/THREAT_MODEL.md`. The section 17 public-claim gate is therefore **not met**.
+
 Native Dosh is a remote-login protocol for Dosh-installed servers. It is intended to
 replace the user's day-to-day `ssh host` workflow for terminals and forwarding while
 keeping SSH as a compatibility and recovery fallback.
@@ -20,6 +51,7 @@ dosh -L 8080:127.0.0.1:80 host
 dosh -R 9000:127.0.0.1:9000 host
 dosh --session work host
 dosh --view-only --session work host
+dosh host tm
 ```
 
 Compatibility expectations:
@@ -76,6 +108,8 @@ Must work in v1:
 - `dosh update`.
 - `dosh doctor host` for config/auth/UDP reachability diagnostics.
 - `dosh sessions host` for session visibility.
+- Optional command extensions such as `dosh host tm` for companion tools that are
+  installed separately from Dosh.
 
 Should work in v1 if it does not compromise the transport schedule:
 
@@ -98,8 +132,14 @@ Native v1 must be boring under real use:
 
 - A closed laptop must not kill the remote session.
 - A client crash must not kill the remote session.
-- Server restart may drop live PTYs in v1 unless session persistence is implemented,
-  but the client must fail clearly and reconnect cleanly afterward.
+- A server restart must not kill the remote session when `persist_sessions` is on
+  (currently opt-in until stress-tested): each session's shell runs in a detached
+  per-session *holder*
+  process whose PTY master fd the server passes back to itself via SCM_RIGHTS, so
+  the shell + scrollback survive a server crash/upgrade/`systemctl restart` and a
+  reattaching client lands on the same shell with its screen restored. With
+  `persist_sessions = false` the old behavior applies: live PTYs drop on restart,
+  but the client must still fail clearly and reconnect cleanly afterward.
 - Decrypt failures from stale packets must be ignored or trigger reconnect, never
   terminate the terminal by themselves.
 - Terminal cleanup must restore cursor, mouse mode, bracketed paste, alternate
@@ -419,6 +459,7 @@ CLI:
 dosh -L [bind_host:]listen_port:target_host:target_port host
 dosh -R [bind_host:]listen_port:target_host:target_port host
 dosh -D [bind_host:]listen_port host
+dosh -A host   # forward the local ssh-agent (opt-in, server-gated)
 ```
 
 Stream packet types:
@@ -435,6 +476,12 @@ Forwarding rules:
 
 - Terminal traffic has priority over stream bulk data.
 - Each stream has independent flow control.
+- `StreamData` carries a per-stream byte offset and is delivered to TCP in order.
+- `StreamWindowAdjust` carries a cumulative received byte offset; peers free
+  retransmit buffers and replenish send credit only for acknowledged contiguous
+  bytes.
+- Unacknowledged stream bytes are retransmitted as newly encrypted transport packets
+  with fresh packet sequence numbers/nonces.
 - Backpressure must not block PTY input or output.
 - Server enforces `no-port-forwarding` and `permitopen=`.
 - Remote listeners bind to loopback by default.
@@ -448,6 +495,24 @@ Forwarding rules:
 - Stream packet scheduling must enforce terminal priority; a large port-forward copy
   cannot make shell keystrokes lag.
 
+### 12.1 SSH-Agent Forwarding (opt-in, security-gated)
+
+- Activated only on explicit client opt-in (`-A` / `forward_agent = true`) **and**
+  server `allow_agent_forwarding = true`. Off by default on both ends.
+- The client requests a `ForwardingKind::Agent` entry during auth. If the server
+  policy allows it, the server binds a per-session proxy unix socket in a
+  process-private directory (dir 0700, socket 0600) and exports its path as the
+  spawned shell's `SSH_AUTH_SOCK`.
+- Each connection from a remote process to that proxy socket is tunneled to the
+  client over a server-initiated `StreamOpen` carrying the reserved target sentinel
+  `@dosh-agent` (port 0). The client splices it into its local `SSH_AUTH_SOCK`
+  (a unix socket, not a TCP target). Data/window/close reuse the existing stream
+  packets unchanged.
+- Only applies to a freshly spawned shell; an already-running attached/prewarmed
+  session keeps its existing environment (same constraint as ssh/mosh).
+- SECURITY: forwarding exposes the local agent to the remote host for the session's
+  lifetime, which is why it is double-gated and never the default.
+
 ## 13. Diagnostics And Operations
 
 Native v1 must include operations commands:
@@ -494,6 +559,10 @@ forward_agent = false
 send_env = ["LANG", "LC_*", "TERM", "COLORTERM"]
 set_env = {}
 forwardings = []
+
+[extensions.tm]
+command = "tm {args}"
+description = "Open an optional server-side tmux dashboard"
 ```
 
 Server:
@@ -544,7 +613,7 @@ Milestone 5: hardening
 
 - Fuzz packet parsing, authorized-key parsing, known-host parsing, and handshake state.
 - Add hostile-network integration tests.
-- Add external review checklist before public security claims.
+- Keep a public hardening checklist and threat model before public security claims.
 
 Milestone 6: workflow parity
 

docs/PROTOCOL_VERSIONING.md

@@ -0,0 +1,40 @@
+# Dosh Protocol Versioning
+
+Dosh v1 uses a deliberately simple compatibility policy: **single-version,
+fail-closed, explicit error**.
+
+The wire header carries `protocol::VERSION`. The native handshake carries
+`native::NATIVE_PROTOCOL_VERSION`. A peer that speaks any other version is rejected
+before application data is accepted:
+
+- foreign wire `VERSION` packets get an `AttachReject` with
+  `protocol version mismatch - upgrade dosh`;
+- foreign native handshake `protocol_version` values get the same named upgrade
+  error with local/remote versions;
+- there is no silent downgrade, compatibility fallback, or best-effort decoding.
+
+## When To Bump
+
+Bump `protocol::VERSION` when a change affects packet framing, packet kind meaning,
+serialized protocol structs carried outside native handshake negotiation, or anything
+an older peer could misparse.
+
+Bump `native::NATIVE_PROTOCOL_VERSION` when a change affects native handshake
+transcripts, native auth semantics, algorithm negotiation, attach tickets, or any
+field that is signed or key-derived by native auth.
+
+If both layers are affected, bump both.
+
+## Compatibility Window
+
+Native v1 supports exactly the current version. That keeps the implementation small
+and makes security review tractable. Multi-version negotiation can be added later
+only with an explicit downgrade-resistance design:
+
+- negotiated version must be transcript-bound;
+- the selected version must be visible in diagnostics;
+- tests must prove an active attacker cannot force an older mutually supported
+  version;
+- unsupported peers must still get the same named upgrade error.
+
+Until that exists, the public policy is: upgrade both sides together.

docs/PUBLIC_READINESS.md

@@ -1,13 +1,21 @@
 # Dosh Public Readiness
 
-Dosh's defensible public claim is fast terminal attach and reconnect. It should not
-claim full Mosh replacement status until the feature matrix below is green and the
-comparison benchmark is reproducible outside the author's homelab.
+Dosh's defensible public claim is fast terminal attach/reconnect plus native
+encrypted forwarding on Dosh-installed servers. It should not claim generic SSH
+compatibility unless it implements the SSH protocol, and public benchmark claims
+must be reproducible outside the author's homelab.
 
 The plan for replacing the day-to-day SSH workflow with native Dosh authentication
-and forwarding is specified in `docs/NATIVE_V1_SPEC.md`. Until that spec is
-implemented and verified, Dosh's public security claim remains SSH-bootstrap plus
-encrypted Dosh transport.
+and forwarding is specified in `docs/NATIVE_V1_SPEC.md`, and the published threat
+model is in `docs/THREAT_MODEL.md`. Native v1 is now substantially implemented:
+native key-exchange + user auth, host-key pinning/trust, `-L`/`-R`/`-D` forwarding,
+`dosh doctor`, token-bucket auth rate limiting, and fuzz-smoke CI all exist (see the
+feature matrix and the verification-checklist status table below). It is **not yet
+fully verified**: long sleep/roaming soak and deeper fuzzing results are still open
+launch evidence. Until the verification checklist (`NATIVE_V1_SPEC.md` section 16)
+is green, Dosh's defensible public security claim remains fast encrypted native
+attach/reconnect and forwarding with SSH bootstrap fallback, not generic SSH
+compatibility.
 
 ## Objective Benchmarks
 
@@ -50,25 +58,31 @@ with ordinary SSH.
 | Feature | Mosh | Dosh now | Public status |
 | --- | --- | --- | --- |
 | SSH-based first authentication | yes | yes | ready |
+| Native UDP key auth (no SSH per attach) | no | yes, Ed25519, ECDSA P-256, and RSA-SHA2 via ssh-agent or OpenSSH identity files | implemented; pending full verification |
+| Dosh host-key pinning and trust | no | yes, `known_hosts` + `dosh trust` + mismatch hard-fail | implemented |
+| `authorized_keys` policy enforcement | no | yes, `from=`/`no-port-forwarding`/`permitopen=`, unsupported fail closed | implemented |
+| `dosh doctor` diagnostics | no | yes, config/auth/UDP/forwarding-policy check | implemented |
 | Encrypted UDP terminal data | yes | yes | ready |
-| Roaming by client address change | yes | yes | needs more hostile-network tests |
-| Survive sleep or network loss | yes | yes | needs long-running soak tests |
+| Roaming by client address change | yes | yes | implemented; hostile-network covered, 30-minute soak gate available |
+| Survive sleep or network loss | yes | yes | implemented; run `make soak-local` before public launch |
 | Fast repeat attach without SSH | no | yes, via attach tickets | core differentiator |
 | Resident server daemon | no | yes | core differentiator |
 | One UDP port for all sessions | port range by default | yes | ready |
 | Fresh session by default | yes | yes | ready |
-| Named persistent sessions | no built-in shared session model | yes | ready |
-| Multiple clients on one session | no | yes | needs conflict-policy docs |
+| Named persistent sessions | no built-in shared session model | yes, plus opt-in server-restart holders | implemented; holder mode needs stress-testing |
+| Multiple clients on one session | no | yes | implemented; needs conflict-policy docs |
 | View-only clients | no | yes | ready |
-| Full-screen TUI correctness | yes | improving | must stay green before public push |
+| Full-screen TUI correctness | yes | yes, scripted transport coverage for control sequences | implemented; needs broader app matrix |
 | Predictive local echo | mature | guarded printable-only opt-in | not parity |
-| Non-destructive disconnect UI | yes | not currently | needed |
+| Non-destructive disconnect UI | yes | yes, bottom-row save/restore status line | implemented |
 | Unicode edge-case handling | strong | basic terminal emulator dependent | not parity |
 | X11 forwarding | no | no | non-goal unless tunneled separately |
-| SSH agent forwarding | no | no | planned as forwarding channel |
-| Local TCP forwarding, `-L` | no | not implemented | planned |
-| Remote TCP forwarding, `-R` | no | not implemented | planned |
-| Dynamic SOCKS forwarding, `-D` | no | not implemented | later |
+| SSH agent forwarding | no | yes, explicit `-A` / `forward_agent` plus server allow-list | implemented; opt-in only |
+| Local TCP forwarding, `-L` | no | yes, native encrypted stream mux | implemented; load/priority, replay/reorder, and stream retransmit tested |
+| Remote TCP forwarding, `-R` | no | yes, loopback bind by default | implemented; policy and stream mux covered |
+| Dynamic SOCKS forwarding, `-D` | no | yes, SOCKS5 over native streams | implemented over the same reliable stream mux |
+| Forward-only / background forwarding, `-N` / `-f` | no | yes, `-f` requires `-N` | implemented |
+| Per-stream flow control / terminal priority | no | yes, windowed credit per stream | implemented; covered by blocked-stream and local-forward load tests |
 
 ## SSH Config Inheritance
 
@@ -81,41 +95,126 @@ Dosh also calls `ssh -G <alias>` to infer the UDP target host when no `dosh_host
 configured. To write explicit Dosh host entries from SSH aliases:
 
 ```bash
-dosh import-ssh palav homelab
+dosh import-ssh homelab
 ```
 
 This appends entries to `~/.config/dosh/hosts.toml` without trying to become an
 OpenSSH config parser.
 
-## Forwarding Plan
+## Optional Command Extensions
+
+Dosh can expose companion tools without taking a dependency on them. Command
+extensions live in client or host config and expand only the first trailing word:
+
+```toml
+[extensions.tm]
+command = "tm {args}"
+description = "Open the server-side tmux dashboard"
+```
+
+With that config, `dosh homelab tm` runs `tm` in the remote Dosh shell and
+`dosh homelab tm dosh` runs `tm 'dosh'`. Removing the table removes the integration.
+Host config can override a global extension, or disable it:
+
+```toml
+[homelab.extensions.tm]
+command = "/opt/tm/bin/tm {args}"
+
+[other-host.extensions.tm]
+disabled = true
+```
+
+## Forwarding (Implemented)
 
 SSH forwarding cannot be copied by keeping the bootstrap SSH connection open,
 because that would remove Dosh's fast reconnect advantage and would break after
-roaming. Dosh forwarding needs native encrypted channels over the Dosh transport.
-
-Minimum viable forwarding design:
+roaming. Dosh forwarding therefore runs as native encrypted stream channels over the
+Dosh transport, and is now implemented.
 
 | CLI | Meaning |
 | --- | --- |
 | `dosh -L 8080:127.0.0.1:80 host` | Local listener on the client; server connects to target. |
-| `dosh -R 8080:127.0.0.1:80 host` | Remote listener on the server; client connects to target. |
+| `dosh -R 8080:127.0.0.1:80 host` | Remote listener on the server (loopback by default); client connects to target. |
+| `dosh -D 1080 host` | SOCKS5 listener on the client; server connects to whatever the SOCKS request names. |
 
-Protocol work required:
+Implemented:
 
-- Add stream-open, stream-data, stream-ack, and stream-close packet types.
-- Use per-stream flow control separate from terminal frame ordering.
-- Never let bulk forwarding traffic delay terminal input/output packets.
-- Bind forwarding permissions to the same SSH-authenticated user as the terminal.
-- Add tests with dropped/reordered UDP packets.
+- `StreamOpen`/`StreamOpenOk`/`StreamOpenReject`/`StreamData`/`StreamWindowAdjust`/
+  `StreamEof`/`StreamClose` packet types.
+- Per-stream windowed flow control (initial 1 MiB credit) separate from terminal
+  frames, so bulk forwarding does not block PTY input/output.
+- Ordered reliable `StreamData` delivery with per-stream byte offsets, cumulative
+  received-offset ACKs, and retransmission re-encrypted as fresh transport packets.
+- Forwarding bound to the native-authenticated user; forwarding refuses to run under
+  `--local-auth` and requires the native auth path.
+- Server-side policy enforcement: `allow_tcp_forwarding`, `allow_remote_forwarding`,
+  loopback-only remote bind unless `allow_remote_non_loopback_bind`, plus per-key
+  `no-port-forwarding` and `permitopen=`.
+- `-N` forward-only (no PTY) and `-f` background (requires `-N`, backgrounds only
+  after listeners are ready).
 
-This is a publishable differentiator once implemented, but it should not be claimed
-until it exists.
+Still open before claiming forwarding parity:
+
+- More real-host load soak. The integration suite already covers terminal-priority
+  behavior while a local forward is under blocked-stream pressure, plus hostile
+  replay/reorder and server-to-client stream retransmission after UDP loss.
+
+## Native v1 Verification Checklist Status
+
+This maps each item in `NATIVE_V1_SPEC.md` section 16 to its status based on what the
+code in `src/` actually does. Done = implemented and exercised by tests or obvious
+from code; in progress = partially implemented; pending = not yet implemented.
+
+| Spec section 16 item | Status | Evidence / note |
+| --- | --- | --- |
+| Unknown host key fails unless TOFU explicitly enabled | done | Client refuses `KnownHostStatus::Unknown` unless `trust_on_first_use`. |
+| Known host-key mismatch hard fails | done | `KnownHostStatus::Mismatch` aborts; `trust_host` refuses overwrite without `--replace`. |
+| Native Ed25519 auth via ssh-agent | done | `src/ssh_agent.rs` signs the user-auth transcript. |
+| Native Ed25519 auth via encrypted key prompt | done | `load_ed25519_identity_with_passphrase` decrypts OpenSSH keys. |
+| Native ECDSA P-256 auth | done | ssh-agent and OpenSSH identity-file paths are wired; `native_user_auth_accepts_ecdsa_p256_private_key` verifies the direct key path. |
+| Native RSA-SHA2 auth | done | ssh-agent requests `rsa-sha2-512`; direct OpenSSH RSA identities sign with `rsa-sha2-512`; legacy SHA-1 `ssh-rsa` signatures are rejected. |
+| Removed authorized key can no longer authenticate | done | Covered by `native_user_auth_accepts_authorized_key_and_rejects_removed_key`. |
+| Unsupported authorized-key options fail closed | done | `ensure_native_allowed` bails on any unsupported option. |
+| Replayed handshake packets rejected | done | Handshake is transcript-bound and signature-verified; pending entries TTL-evicted. |
+| Replayed transport packets rejected | done | `ReplayWindow` (128-wide) over per-direction counter. |
+| Stale encrypted packets after reconnect ignored, not fatal | done | `session_key_id` mismatch drops the packet instead of erroring fatally. |
+| Client IP/port change preserves session | done | Server matches by `ClientId`/session key id, updates endpoint. |
+| Native cold auth beats cold `ssh host true` | done | Docker gate runs `dosh-bench --cold-native` after one-time `dosh trust` and requires Dosh mean <= SSH mean. |
+| Cached attach near network RTT | done | Local loopback samples are ~3 ms; Docker cached gate is under 25 ms. See `docs/BENCHMARKS.md`. |
+| `-L` works without delaying terminal input | done | Per-stream windowing plus `native_local_forward_bulk_load_does_not_delay_interactive_terminal` and blocked-stream priority regression. |
+| `-R` enforces bind and permission policy | done | `remote_bind_allowed` + `start_remote_forwards` policy checks. |
+| `-N -L` does not allocate a PTY | done | `forward-only` mode skips PTY allocation. |
+| `-f -N -L` backgrounds only after listener readiness | done | `spawn_background_forwarder` waits for a readiness token. |
+| Multiple forwards in one command | done | Forward lists parsed and started together. |
+| `dosh doctor` identifies UDP-blocked/auth-denied/mismatch/forwarding-denied | done | `run_doctor_command` reports each state. |
+| Closing laptop 30+ min does not kill session | done | `make soak-local` passed `sleep_roaming_soak_30m` for 1803.54s locally. Keep rerunning before tagged releases. |
+| Three concurrent terminals independent unless named | done | Generated session names per attach; named sessions shared on purpose. |
+| Large forwarded transfers add no visible input lag | done | Covered by the local-forward bulk-load integration test; still needs real-host soak before launch claims. |
+| Fuzz targets run in CI | done | `fuzz/` has parser/auth targets; CI runs 20s per target on push/PR and 300s per target on weekly/manual runs when cargo-fuzz is available. |
+| Threat model updated with accepted residual risks | done | `docs/THREAT_MODEL.md`. |
+
+Additional security hardening tracked outside the section 16 list:
+
+- Full per-IP token-bucket rate limiting: implemented for native auth and covered by
+  unit/integration tests. It still needs real-host tuning under abusive traffic.
+- Protocol VERSION handling: v1 policy is single-version, fail-closed reject at the
+  packet/header and native-handshake layers. See `docs/PROTOCOL_VERSIONING.md`.
+- ECDSA P-256 / SHA-2 RSA user keys: implemented for ssh-agent and OpenSSH
+  identity-file native auth. RSA is compatibility-only and uses SHA-2 signatures;
+  legacy SHA-1 `ssh-rsa` signatures are not accepted.
 
 ## Before Public Launch
 
 - Keep `cargo test`, `make bench-docker-ssh`, and `make bench-docker-mosh` green.
-- Add a non-destructive disconnect indicator.
-- Run scripted TUI tests for alternate-screen apps, arrow keys, resize, mouse mode,
-  bracketed paste, and terminal cleanup.
+- Run `make soak-local` before each tagged release to refresh 30-minute sleep/roaming evidence.
+- Run `make fuzz-deep` before launch, or use the scheduled/manual CI fuzz pass, and
+  publish the target durations.
+- Keep scripted TUI tests green and add a broader app matrix for real alternate-screen
+  tools.
 - Publish benchmark output with raw samples, not just averages.
 - Mark prediction as experimental until it has a real framebuffer model.
+- Stress-test `persist_sessions = true` before making restart-survivable holders the
+  default.
+- Tune the native auth token bucket under abusive real-host traffic.
+- Complete the native-v1 verification checklist above before making any "native SSH
+  replacement for Dosh-installed servers" claim (`NATIVE_V1_SPEC.md` section 17).

docs/RELEASE_EVIDENCE_2026-06-20.md

@@ -0,0 +1,127 @@
+# Dosh Release Evidence - 2026-06-20
+
+Runtime code benchmarked: `b44ff8e Improve release and benchmark tooling`
+
+Release docs/default cleanup after that benchmark removed personal host aliases from
+public examples and test fixtures; it did not change release runtime paths.
+
+Environment:
+
+- Host: local homelab runner
+- Benchmark harness: `make bench-docker-mosh`
+- Container SSH server: OpenSSH 9.6p1 on Ubuntu
+- Same container, key, DNS, loopback, and Dosh server path for all Docker samples
+
+## Release Artifacts
+
+Generated locally with:
+
+```bash
+sh scripts/package-release.sh
+```
+
+Artifacts:
+
+| artifact | sha256 |
+| --- | --- |
+| `dosh-linux-x86_64.tar.gz` | `9f586852a506cca3caf618743e12967265879ee10f5294d179cdcd668db1e808` |
+| `dosh-0.1.0-linux-x86_64.tar.gz` | `9f586852a506cca3caf618743e12967265879ee10f5294d179cdcd668db1e808` |
+| `dosh-macos-aarch64.tar.gz` | `dd1151aa2b40be37288dc19a07521b0ec72d1106439eb484cdff01cca3b891c6` |
+| `dosh-0.1.0-macos-aarch64.tar.gz` | `dd1151aa2b40be37288dc19a07521b0ec72d1106439eb484cdff01cca3b891c6` |
+
+The installer verifies `<artifact>.sha256` when the sidecar is published.
+
+## Docker SSH/Mosh Benchmark
+
+Command:
+
+```bash
+make bench-docker-mosh
+```
+
+### Cold SSH Bootstrap
+
+| metric | n | min ms | median ms | p95 ms | mean ms | max ms |
+| --- | ---: | ---: | ---: | ---: | ---: | ---: |
+| `ssh_true_ms` | 3 | 216.58 | 220.27 | 224.64 | 220.66 | 225.12 |
+| `dosh_attach_ms` | 3 | 232.37 | 235.56 | 239.13 | 235.82 | 239.53 |
+
+Raw samples:
+
+- `ssh_true_ms`: [216.58, 220.27, 225.12]
+- `dosh_attach_ms`: [235.56, 232.37, 239.53]
+
+Gate: `dosh_attach_ms avg 235.82ms <= ssh avg 220.66ms + 500.00ms`
+
+### ControlMaster SSH Bootstrap
+
+| metric | n | min ms | median ms | p95 ms | mean ms | max ms |
+| --- | ---: | ---: | ---: | ---: | ---: | ---: |
+| `ssh_true_ms` | 3 | 7.29 | 7.50 | 47.51 | 22.25 | 51.95 |
+| `dosh_attach_ms` | 3 | 16.62 | 17.01 | 17.77 | 17.16 | 17.85 |
+
+Raw samples:
+
+- `ssh_true_ms`: [51.95, 7.29, 7.50]
+- `dosh_attach_ms`: [17.01, 16.62, 17.85]
+
+Gate: `dosh_attach_ms avg 17.16ms <= ssh avg 22.25ms + 500.00ms`
+
+### Native Cold Auth
+
+| metric | n | min ms | median ms | p95 ms | mean ms | max ms |
+| --- | ---: | ---: | ---: | ---: | ---: | ---: |
+| `ssh_true_ms` | 5 | 215.72 | 222.68 | 227.05 | 221.32 | 227.82 |
+| `dosh_cold_native_ms` | 5 | 8.63 | 8.84 | 9.16 | 8.88 | 9.23 |
+
+Raw samples:
+
+- `ssh_true_ms`: [216.40, 223.99, 227.82, 222.68, 215.72]
+- `dosh_cold_native_ms`: [8.84, 8.63, 9.23, 8.88, 8.84]
+
+Gate: `dosh_cold_native_ms avg 8.88ms <= ssh avg 221.32ms + 0.00ms`
+
+### Cached Attach
+
+| metric | n | min ms | median ms | p95 ms | mean ms | max ms |
+| --- | ---: | ---: | ---: | ---: | ---: | ---: |
+| `dosh_cached_attach_ms` | 10 | 8.07 | 8.96 | 9.83 | 8.98 | 9.84 |
+
+Raw samples:
+
+- `dosh_cached_attach_ms`: [8.07, 9.09, 9.02, 8.66, 8.71, 8.90, 8.45, 9.84, 9.25, 9.82]
+
+Gate: `dosh_cached_attach_ms avg 8.98ms <= 25.00ms`
+
+### Mosh Comparison
+
+| metric | n | min ms | median ms | p95 ms | mean ms | max ms |
+| --- | ---: | ---: | ---: | ---: | ---: | ---: |
+| `ssh_true_ms` | 3 | 216.48 | 218.93 | 219.49 | 218.32 | 219.55 |
+| `dosh_attach_ms` | 3 | 229.59 | 233.00 | 233.31 | 231.98 | 233.35 |
+| `mosh_start_true_ms` | 3 | 527.13 | 563.34 | 573.09 | 554.89 | 574.18 |
+
+Raw samples:
+
+- `ssh_true_ms`: [219.55, 216.48, 218.93]
+- `dosh_attach_ms`: [233.00, 229.59, 233.35]
+- `mosh_start_true_ms`: [563.34, 527.13, 574.18]
+
+## Soak And Fuzz Evidence
+
+- `cargo test`: `153 passed, 1 ignored`
+- `make soak-local`: `sleep_roaming_soak_30m ... ok`, finished in `1803.54s`
+- `make fuzz-smoke`: passed all configured targets for 20s each:
+  `packet_decode`, `from_body`, `authorized_keys`, `known_hosts`,
+  `handshake_structs`, `attach_ticket`
+
+## Public Claim Boundary
+
+This evidence supports:
+
+- Dosh cached attach and native auth are much faster than cold SSH/Mosh startup in
+  this benchmark environment.
+- Dosh remains mosh-shaped, not mosh-compatible.
+- Dosh does not claim generic SSH replacement compatibility.
+- Native v1 security still needs external review before making hard public security
+  claims.

docs/THREAT_MODEL.md

@@ -0,0 +1,241 @@
+# Dosh Threat Model
+
+This is the published threat model for Dosh native v1, derived from
+`docs/NATIVE_V1_SPEC.md` sections 4-6. It states the assets Dosh protects, the
+attackers it does and does not defend against, the security properties Dosh claims
+relative to SSH, the cryptographic building blocks actually in use, and an honest
+list of accepted residual risks and known gaps.
+
+Dosh is a remote-login transport for Dosh-installed servers. It is intended to
+replace the day-to-day `ssh host` workflow for terminals and TCP forwarding while
+keeping OpenSSH as a recovery and bootstrap fallback. Dosh is **not** an
+RFC-compatible SSH implementation and does not claim SSH's entire protocol security
+surface. It claims security that is **equivalent to, and in some respects stronger
+than, SSH for the Dosh terminal and forwarding use case** on hosts running
+`dosh-server`.
+
+## 1. Assets
+
+Dosh protects:
+
+- **Terminal session contents.** Keystrokes, command output, and the authoritative
+  screen state for every named or generated session.
+- **Forwarded TCP streams.** Bytes carried over `-L`, `-R`, and `-D` channels.
+- **User authentication credentials.** The user's SSH/Dosh private keys and any
+  ssh-agent identities. Dosh never sees private key material in plaintext on the
+  wire; signatures are produced locally or by the agent.
+- **Server-issued credentials.** Session keys, `ClientId` association state,
+  server-sealed attach tickets, and the client-held attach-ticket PSK.
+- **Server identity.** The persistent Dosh host key (`~/.config/dosh/host_key`) and
+  the server secret used to seal attach tickets and derive bootstrap material.
+- **Host-trust state.** The client's pinned known-hosts file
+  (`~/.config/dosh/known_hosts`).
+- **Authorization policy.** `~/.ssh/authorized_keys` /
+  `~/.config/dosh/authorized_keys` and the forwarding policy they encode.
+
+## 2. Attackers
+
+### In scope (Dosh must defend against these)
+
+- **Passive network observer.** May record all UDP traffic between client and
+  server.
+- **Active network attacker.** May spoof, drop, replay, reorder, or modify any
+  packet, and may attempt to inject forged packets in either direction.
+- **NAT rebinding / roaming.** Client source IP and port may change mid-session,
+  including across sleep, network switch, and NAT timeout.
+- **Stolen attach-ticket cache without the user's private key.** An attacker who
+  reads a client cache copies a server-sealed ticket plus its PSK but does not have
+  the user's SSH private key.
+- **Server restart and key rotation.** Stale session keys, tickets, and replay
+  state must not be usable after the server rotates its secret or host key.
+- **Malicious unauthenticated client flooding auth attempts.** A peer that has no
+  authorized key tries to exhaust server resources or guess credentials.
+- **Compromised low-privilege local user on a shared client.** A different local
+  user attempts to read Dosh credential caches on the same machine.
+
+### Out of scope (explicitly not defended against)
+
+- **Compromised client machine.** If the endpoint running `dosh-client` is owned by
+  the attacker, the attacker has the user's keys and terminal.
+- **Compromised server account.** If the login account on the server is owned, the
+  attacker already has the shell Dosh would have given them.
+- **Malicious kernel, terminal emulator, or PTY implementation** on either side.
+- **A server that was legitimately authorized and later turns malicious.** Host-key
+  pinning detects a *substituted* server, not a trusted server that decides to
+  misbehave.
+
+These exclusions match SSH's own boundaries: SSH likewise cannot protect a
+compromised endpoint or a malicious authorized peer.
+
+## 3. Security Properties Claimed vs SSH
+
+| Property | SSH | Dosh native v1 | Notes |
+| --- | --- | --- | --- |
+| Server authentication before trusting session data | yes | yes | Host key signs the handshake transcript; client verifies before sending user auth or accepting terminal bytes. |
+| User authentication by private-key possession | yes | yes | Ed25519, ECDSA P-256, and RSA-SHA2 via ssh-agent or OpenSSH key; signature binds the full transcript. |
+| Forward secrecy | yes | yes | Ephemeral X25519 per connection; long-term host/user keys never derive the traffic key. |
+| AEAD on every post-handshake packet | yes | yes | ChaCha20-Poly1305 with per-direction, per-sequence nonces. |
+| Replay protection | yes | yes | Sliding replay window over the AEAD packet counter, plus transcript-bound handshake. |
+| Host-key pinning with explicit first use | TOFU, weakly tied to transport | yes, with explicit policy | Default refuses unknown host keys; TOFU only when `trust_on_first_use` is set; mismatch hard-fails and never auto-replaces. |
+| No plaintext terminal bytes after handshake | yes | yes | All `Frame`/`Input`/stream packets are AEAD-sealed. |
+| No custom cryptographic primitives | yes | yes | Standard X25519/HKDF-SHA256/ChaCha20-Poly1305/signature crates only. |
+| Fail-closed downgrade behavior | yes | yes | Native auth failure surfaces an explicit error and SSH fallback is explicit; it never silently drops to an unauthenticated mode. |
+| Fast resumption without re-auth | ControlMaster only | yes, native | Cached session/ticket attach skips a fresh round of public-key proof; this is a deliberate speed/security trade discussed in section 6. |
+
+### Where Dosh aims to *exceed* SSH for this use case
+
+- **Tighter transcript binding.** A user-auth signature binds both ephemeral keys,
+  both randoms, the server host key, requested user/session/mode/terminal size,
+  selected algorithms, and protocol version into one transcript. This forecloses
+  cross-protocol and partial-replay confusion classes for the narrow Dosh surface.
+- **Smaller attack surface.** Dosh deliberately omits the full SSH transport/channel
+  machinery, arbitrary subsystems, X11, SFTP/SCP, and forced-command subsystems.
+  Fewer features means fewer parsers and fewer reachable states.
+- **Explicit, file-pinned host trust.** Host trust is a first-class, inspectable
+  known-hosts entry with source provenance (`tofu`/`ssh`/`manual`) and a hard-fail
+  mismatch path, rather than the looser default TOFU behavior most SSH clients ship.
+- **Modern primitives only.** Ed25519 and X25519 by default; ECDSA P-256 and
+  RSA-SHA2 are accepted for SSH-key compatibility; no DSA, no SHA-1 signatures, no
+  CBC-and-MAC constructions.
+
+Dosh does **not** claim generic SSH compatibility and must not be described as an
+SSH-protocol implementation.
+
+## 4. Cryptographic Building Blocks (as implemented)
+
+These reflect the code in `src/crypto.rs`, `src/native.rs`, `src/auth.rs`, and
+`src/protocol.rs`, not just the spec.
+
+- **Key exchange:** X25519 ephemeral-ephemeral (`x25519-dalek`). The shared secret
+  is checked for contributory behaviour; a non-contributory result is rejected.
+- **Handshake/transport KDF:** HKDF-SHA256 (`hkdf`), salted with the SHA-256 of the
+  serialized `ClientHello` and `ServerHello`, binding traffic keys to the transcript.
+- **AEAD:** ChaCha20-Poly1305 (`chacha20poly1305`) for every encrypted packet and
+  for sealed attach tickets. Nonces are derived as `direction || sequence`, giving a
+  unique nonce per `(key, direction, sequence)`. AES-GCM is reserved for later and is
+  not selectable today.
+- **Host-key signatures:** Ed25519 (`ed25519-dalek`) over the handshake transcript.
+- **User-auth signatures:** Ed25519, ECDSA P-256, and RSA-SHA2, produced either by
+  ssh-agent over a Unix socket (`src/ssh_agent.rs`) or from an encrypted/plaintext
+  OpenSSH private key (`ssh-key`). The signature covers the user-auth transcript
+  described above. RSA public keys are matched as `ssh-rsa` authorized keys, but
+  native signatures must be `rsa-sha2-256` or `rsa-sha2-512`; legacy SHA-1
+  `ssh-rsa` signatures are rejected.
+- **Bootstrap auth (SSH fallback path):** HMAC-SHA256 attach tokens and HKDF-SHA256
+  derived session keys, with attach tickets sealed under an HKDF-derived
+  ticket key. Token comparison is constant-time.
+- **Hashing/transcript:** SHA-256 (`sha2`).
+- **Randomness:** OS CSPRNG via `rand::thread_rng()` / `OsRng`.
+
+No homegrown ciphers, MACs, padding schemes, or key derivation are used. No nonce or
+key pair is reused within a direction.
+
+## 5. How the Properties Are Enforced (handshake and transport)
+
+- **Server authentication.** `ServerHello` carries the host public key and an Ed25519
+  signature over `dosh/native/server-hello/v1 || ClientHello || ServerHello(unsigned)`.
+  The client verifies this signature *and* checks the host key against its pinned
+  known-hosts entry before sending user auth or accepting terminal bytes. Unknown
+  keys are refused unless TOFU is enabled; mismatches hard-fail with both
+  fingerprints and the file path.
+- **User authentication.** `UserAuth` carries an Ed25519 signature over
+  `dosh/native/user-auth/v1 || ClientHello || ServerHello || UserAuth(unsigned)`. The
+  server looks the public key up in `authorized_keys`, enforces authorized-key
+  options, then verifies the signature. A removed key can no longer authenticate.
+- **Authorization options.** `from=` (with CIDR, glob, and negation),
+  `no-port-forwarding`, and `permitopen=` are enforced. `command=` is rejected for
+  native terminal login. Any unrecognized restrictive option fails closed rather than
+  being silently ignored.
+- **Forwarding policy.** The server enforces `allow_tcp_forwarding`,
+  `allow_remote_forwarding`, and a loopback-only default for remote binds
+  (`allow_remote_non_loopback_bind`), in addition to per-key `permitopen=` /
+  `no-port-forwarding`.
+- **Replay protection.** A 128-wide sliding window over the per-direction packet
+  counter rejects duplicates and stale sequences. Sequence 0 is never accepted.
+- **Stale-key tolerance.** Each encrypted packet carries a `session_key_id`; packets
+  under an old key are dropped as "stale or wrong session key id" rather than treated
+  as fatal decrypt failures, so reconnect after rotation is non-destructive.
+- **Roaming.** The server keys clients by `ClientId` and session key id, not by
+  source address, and updates the endpoint after any valid encrypted packet from a
+  new address — without weakening authentication, because the packet must still
+  decrypt and verify.
+
+## 6. Accepted Residual Risks and Known Gaps
+
+These are stated openly so the public claim gate (`NATIVE_V1_SPEC.md` section 17) can
+be evaluated honestly. Items here are *not* yet "green".
+
+### Accepted residual risks (by design)
+
+- **Attach tickets prove recent server-issued possession, not fresh private-key
+  possession.** A stolen client cache containing both the sealed ticket and its PSK
+  can attach until the ticket expires (default TTL 24h, configurable down to zero) or
+  until the server rotates its secret/host key or the user key is removed. This is the
+  deliberate speed trade. It is bounded by TTL, scoped to host/user/session/mode, and
+  can be disabled. SSH ControlMaster has an analogous live-socket exposure.
+- **Local cache confidentiality relies on filesystem permissions.** Host keys,
+  server secret, known-hosts, and credential caches are written `0600`. A
+  same-machine attacker who can already read another user's `0600` files (e.g. via
+  root) is out of scope, as with SSH's `~/.ssh`.
+- **A trusted server that turns malicious is not detected.** Host-key pinning
+  detects substitution, not betrayal by an already-authorized server. This matches
+  SSH.
+
+### Known gaps / work in progress (must close before the public claim)
+
+- **Native-auth rate limiting needs tuning, not first implementation.** The server
+  enforces a per-source token bucket before expensive native-auth work, evicts
+  half-finished handshakes on a TTL, and reports remaining capacity in
+  `ServerHello`. It is covered by unit/integration tests, but still needs abusive
+  real-host tuning before public hardening claims.
+- **Protocol VERSION compatibility is intentionally single-version for v1.** The
+  packet header rejects any non-matching `VERSION` byte and the native handshake
+  rejects any non-matching `protocol_version`; peers get a named upgrade error, not
+  a silent downgrade. `docs/PROTOCOL_VERSIONING.md` defines the bump rules and the
+  post-v1 requirements for any future multi-version negotiation.
+- **Deep fuzzing still needs launch evidence.** CI runs parser/auth fuzz targets for
+  20 seconds per target on push/PR and 300 seconds per target on weekly/manual runs
+  when nightly/cargo-fuzz is available. That catches obvious panics and parser
+  robustness regressions; public security claims should cite a completed
+  `make fuzz-deep` or scheduled CI run with durations.
+- **User-key algorithm coverage now matches the v1 target.** Ed25519, ECDSA P-256,
+  and compatibility RSA-SHA2 native auth are implemented for ssh-agent and OpenSSH
+  identity files. RSA remains compatibility-only and deliberately rejects legacy
+  SHA-1 `ssh-rsa` signatures.
+- **Forwarded stream data uses ordered retransmission.** Streams carry byte offsets,
+  cumulative received-offset ACKs, and retransmit unacknowledged chunks as fresh
+  encrypted transport packets. Hostile-network tests cover replay/reorder and
+  server-to-client stream recovery after deliberate UDP loss; broader real-host load
+  soak remains launch evidence.
+- **Long-soak evidence is a launch gate.** Roaming, retransmit, resize, and
+  multi-client tests exist, and `sleep_roaming_soak_30m` / `make soak-local` provide
+  the 30-minute sleep/roaming gate. That gate should be run and published before
+  public security/reliability claims.
+- **No third-party audit claim.** Dosh maintains a public threat model and hardening
+  checklist, but should not market itself as externally audited unless that actually
+  happens.
+
+### Auth posture
+
+Native auth is **opt-in alongside SSH fallback**. `auth_preference` defaults to
+`native,ssh`: Dosh tries the native authenticated path first and falls back to SSH
+bootstrap explicitly and visibly when native auth is disabled, unavailable, or
+rejected. Native auth failure never silently degrades to an unauthenticated mode.
+Forwarding (`-L`/`-R`/`-D`) requires the native authenticated path and refuses to run
+under `--local-auth`.
+
+## 7. Verification and Public-Claim Status
+
+Dosh may claim "native SSH replacement for Dosh-installed servers" only after the
+conditions in `NATIVE_V1_SPEC.md` section 17 are met: native auth default on a real
+host, SSH fallback available, the section 16 checklist green, this threat model
+published, and benchmarks with raw samples for SSH cold, Dosh native cold, Dosh
+cached attach, and Mosh startup.
+
+Current status: this threat model is published (this document). The verification
+checklist is **not yet fully green** — see the item-by-item status table in
+`docs/PUBLIC_READINESS.md` ("Native v1 verification checklist status") and the known
+gaps in section 6 above. Until the gaps close, Dosh's defensible public claim remains
+**fast, encrypted native attach/reconnect and forwarding with SSH bootstrap
+fallback** on Dosh-installed servers, not generic SSH compatibility or a third-party
+audited security product.

fuzz/.gitignore

@@ -0,0 +1,5 @@
+/target
+/corpus
+/artifacts
+/coverage
+Cargo.lock

fuzz/Cargo.toml

@@ -0,0 +1,64 @@
+[package]
+name = "dosh-fuzz"
+version = "0.0.0"
+publish = false
+edition = "2021"
+
+# Standalone workspace so this crate is never absorbed by, and never affects,
+# the main `dosh` crate's `cargo build` / `cargo test` / `cargo fmt --check`.
+[workspace]
+
+[package.metadata]
+cargo-fuzz = true
+
+[dependencies]
+libfuzzer-sys = "0.4"
+
+[dependencies.dosh]
+path = ".."
+
+# cargo-fuzz needs unwinding to report panics; keep debug assertions on.
+[profile.release]
+debug = 1
+
+[[bin]]
+name = "packet_decode"
+path = "fuzz_targets/packet_decode.rs"
+test = false
+doc = false
+bench = false
+
+[[bin]]
+name = "from_body"
+path = "fuzz_targets/from_body.rs"
+test = false
+doc = false
+bench = false
+
+[[bin]]
+name = "authorized_keys"
+path = "fuzz_targets/authorized_keys.rs"
+test = false
+doc = false
+bench = false
+
+[[bin]]
+name = "known_hosts"
+path = "fuzz_targets/known_hosts.rs"
+test = false
+doc = false
+bench = false
+
+[[bin]]
+name = "handshake_structs"
+path = "fuzz_targets/handshake_structs.rs"
+test = false
+doc = false
+bench = false
+
+[[bin]]
+name = "attach_ticket"
+path = "fuzz_targets/attach_ticket.rs"
+test = false
+doc = false
+bench = false

fuzz/README.md

@@ -0,0 +1,67 @@
+# dosh fuzz targets
+
+cargo-fuzz / libFuzzer harnesses for the `dosh` parsers and handshake verifiers
+(spec milestone 5 / §16: "Fuzz packet parsing, authorized-key parsing,
+known-host parsing, and handshake state", "Fuzz targets run in CI").
+
+This is a **standalone crate** (its own `[workspace]`) so it never affects the
+main crate's `cargo build` / `cargo test` / `cargo fmt --check`.
+
+## Targets
+
+| Target | Parser(s) exercised |
+| --- | --- |
+| `packet_decode` | `protocol::Header::parse`, `protocol::decode`, `protocol::decrypt_body` |
+| `from_body` | `protocol::from_body::<T>` for every protocol & native wire struct |
+| `authorized_keys` | `native::parse_authorized_keys`, `native::parse_ssh_ed25519_public_blob` |
+| `known_hosts` | `native::parse_known_hosts`, `native::parse_host_public_key_line` |
+| `handshake_structs` | handshake struct decode + `verify_server_hello`, `user_auth_transcript`, `verify_native_user_auth` |
+| `attach_ticket` | `auth::open_attach_ticket`, `auth::verify_attach_ticket`, `auth::decode_bootstrap` |
+
+Every target's objective is the same: **no panics on any input** (a panic on
+untrusted bytes is a robustness/DoS bug per threat model §5).
+
+## Prerequisites
+
+```sh
+rustup toolchain install nightly
+cargo install cargo-fuzz
+```
+
+cargo-fuzz requires a nightly toolchain (it builds with `-Z sanitizer=address`).
+
+## Run
+
+From the repository root:
+
+```sh
+# Run all targets for a short smoke pass
+make fuzz-smoke
+
+# Run all targets for the pre-launch deep pass (default: 300s each)
+make fuzz-deep
+
+# List targets
+cargo +nightly fuzz list --fuzz-dir fuzz
+
+# Run a single target indefinitely
+cargo +nightly fuzz run --fuzz-dir fuzz packet_decode
+
+# Short, CI-style smoke run of one target (10 seconds)
+cargo +nightly fuzz run --fuzz-dir fuzz packet_decode -- -max_total_time=10
+```
+
+Or from inside `fuzz/`:
+
+```sh
+cd fuzz
+cargo +nightly fuzz run packet_decode -- -max_total_time=10
+```
+
+## CI
+
+`.github/workflows/ci.yml` has a `fuzz-smoke` job that installs nightly +
+cargo-fuzz and runs each target. Push/PR runs use a short 20-second-per-target
+smoke pass. Weekly scheduled and manual workflow runs use a 300-second-per-target
+deep pass by default. The job is tolerant if the toolchain/tooling is unavailable
+so it never blocks the main test gate.

fuzz/fuzz_targets/attach_ticket.rs

@@ -0,0 +1,20 @@
+#![no_main]
+//! Fuzz the attach-ticket and bootstrap decoders. These open server-sealed
+//! AEAD blobs and base64 bootstrap envelopes from cache / wire material that an
+//! attacker may corrupt; none may panic.
+
+use libfuzzer_sys::fuzz_target;
+
+use dosh::auth::{decode_bootstrap, open_attach_ticket, verify_attach_ticket};
+
+fuzz_target!(|data: &[u8]| {
+    let secret = [0x11u8; 32];
+    let psk = [0x22u8; 32];
+
+    let _ = open_attach_ticket(&secret, data);
+    let _ = verify_attach_ticket(&secret, data, &psk, "default", "read-write");
+
+    if let Ok(text) = std::str::from_utf8(data) {
+        let _ = decode_bootstrap(text);
+    }
+});

fuzz/fuzz_targets/authorized_keys.rs

@@ -0,0 +1,18 @@
+#![no_main]
+//! Fuzz the authorized_keys parser, including its option lexer and the
+//! ssh-ed25519 public-key blob parser it depends on. None may panic.
+
+use libfuzzer_sys::fuzz_target;
+
+use dosh::native::{parse_authorized_keys, parse_ssh_ed25519_public_blob};
+
+fuzz_target!(|data: &[u8]| {
+    // The blob parser operates directly on raw bytes.
+    let _ = parse_ssh_ed25519_public_blob(data);
+
+    // The line parser operates on text; only feed valid UTF-8 (lossless),
+    // matching how the file is read in production via read_to_string.
+    if let Ok(text) = std::str::from_utf8(data) {
+        let _ = parse_authorized_keys(text);
+    }
+});

fuzz/fuzz_targets/from_body.rs

@@ -0,0 +1,62 @@
+#![no_main]
+//! Fuzz `protocol::from_body` (bincode deserialization) for every protocol and
+//! native struct that is decoded from untrusted wire bytes. None may panic.
+
+use libfuzzer_sys::fuzz_target;
+
+use dosh::auth::{AttachTicketPlain, BootstrapResponse, SealedAttachTicket};
+use dosh::native::{
+    HostPublicKey, NativeAuthOk, NativeClientHello, NativeServerHello, NativeUserAuth,
+};
+use dosh::protocol::{
+    self, AttachOk, AttachReject, BootstrapAttachRequest, Frame, Input, NativeAuthCheckOkBody,
+    NativeAuthOkBody, NativeClientHelloBody, NativeServerHelloBody, NativeUserAuthBody, Resize,
+    ResumeRequest, StreamClose, StreamData, StreamEof, StreamOpen, StreamOpenOk, StreamOpenReject,
+    StreamWindowAdjust, TicketAttachBody, TicketAttachEnvelope, TicketAttachOkEnvelope,
+};
+
+macro_rules! try_body {
+    ($data:expr, $ty:ty) => {
+        let _ = protocol::from_body::<$ty>($data);
+    };
+}
+
+fuzz_target!(|data: &[u8]| {
+    // protocol.rs structs
+    try_body!(data, BootstrapAttachRequest);
+    try_body!(data, TicketAttachEnvelope);
+    try_body!(data, TicketAttachBody);
+    try_body!(data, TicketAttachOkEnvelope);
+    try_body!(data, AttachOk);
+    try_body!(data, AttachReject);
+    try_body!(data, ResumeRequest);
+    try_body!(data, Input);
+    try_body!(data, Resize);
+    try_body!(data, Frame);
+    try_body!(data, StreamOpen);
+    try_body!(data, StreamOpenOk);
+    try_body!(data, StreamOpenReject);
+    try_body!(data, StreamData);
+    try_body!(data, StreamWindowAdjust);
+    try_body!(data, StreamEof);
+    try_body!(data, StreamClose);
+
+    // native handshake wrapper bodies
+    try_body!(data, NativeClientHelloBody);
+    try_body!(data, NativeServerHelloBody);
+    try_body!(data, NativeUserAuthBody);
+    try_body!(data, NativeAuthOkBody);
+    try_body!(data, NativeAuthCheckOkBody);
+
+    // bare native handshake structs
+    try_body!(data, NativeClientHello);
+    try_body!(data, NativeServerHello);
+    try_body!(data, NativeUserAuth);
+    try_body!(data, NativeAuthOk);
+    try_body!(data, HostPublicKey);
+
+    // auth.rs structs
+    try_body!(data, BootstrapResponse);
+    try_body!(data, SealedAttachTicket);
+    try_body!(data, AttachTicketPlain);
+});

fuzz/fuzz_targets/handshake_structs.rs

@@ -0,0 +1,44 @@
+#![no_main]
+//! Fuzz the native handshake structs and their structural verifiers.
+//!
+//! Beyond plain deserialization (covered by the `from_body` target), this drives
+//! the verifier state machine: if the input happens to decode into the handshake
+//! structs, run `verify_server_hello`, `user_auth_transcript`, and
+//! `verify_native_user_auth` on them. These run on attacker-controlled material
+//! during the handshake and must reject (Err) without panicking.
+
+use libfuzzer_sys::fuzz_target;
+
+use dosh::native::{
+    NativeClientHello, NativeServerHello, NativeUserAuth, user_auth_transcript,
+    verify_native_user_auth, verify_server_hello,
+};
+use dosh::protocol;
+
+fuzz_target!(|data: &[u8]| {
+    // Split the input into three slices and try to decode each into a handshake
+    // struct. Use a length prefix scheme that is robust to short inputs.
+    if data.len() < 3 {
+        return;
+    }
+    let n = data.len();
+    let a = n / 3;
+    let b = 2 * n / 3;
+    let (chunk_client, chunk_server, chunk_auth) = (&data[..a], &data[a..b], &data[b..]);
+
+    let client: Option<NativeClientHello> = protocol::from_body(chunk_client).ok();
+    let server: Option<NativeServerHello> = protocol::from_body(chunk_server).ok();
+    let auth: Option<NativeUserAuth> = protocol::from_body(chunk_auth).ok();
+
+    if let (Some(client), Some(server)) = (&client, &server) {
+        // Host signature verification over the transcript must not panic.
+        let _ = verify_server_hello(client, server);
+
+        if let Some(auth) = &auth {
+            // Transcript construction and full user-auth verification (signature
+            // check + authorized-key matching) must not panic on garbage.
+            let _ = user_auth_transcript(client, server, auth);
+            let _ = verify_native_user_auth(client, server, auth, &[], None);
+        }
+    }
+});

fuzz/fuzz_targets/known_hosts.rs

@@ -0,0 +1,14 @@
+#![no_main]
+//! Fuzz the known_hosts parser and the host-public-key line parser. None may
+//! panic on arbitrary input.
+
+use libfuzzer_sys::fuzz_target;
+
+use dosh::native::{parse_host_public_key_line, parse_known_hosts};
+
+fuzz_target!(|data: &[u8]| {
+    if let Ok(text) = std::str::from_utf8(data) {
+        let _ = parse_known_hosts(text);
+        let _ = parse_host_public_key_line(text);
+    }
+});

fuzz/fuzz_targets/packet_decode.rs

@@ -0,0 +1,23 @@
+#![no_main]
+//! Fuzz the wire-packet decoder + decrypt path.
+//!
+//! Mirrors tests/parser_robustness.rs but driven by libFuzzer so the coverage
+//! engine can search for panics in `protocol::decode`, `Header::parse`, and the
+//! decode -> decrypt_body pipeline. The objective is: NO PANICS on any input.
+
+use libfuzzer_sys::fuzz_target;
+
+use dosh::protocol::{self, CLIENT_TO_SERVER, SERVER_TO_CLIENT};
+
+fuzz_target!(|data: &[u8]| {
+    // Header parsing must never panic.
+    let _ = protocol::Header::parse(data);
+
+    // Full decode, then attempt decryption with a fixed key in both directions.
+    // A real attacker controls these bytes; neither path may panic.
+    if let Ok(packet) = protocol::decode(data) {
+        let key = [0x42u8; 32];
+        let _ = protocol::decrypt_body(&packet, &key, CLIENT_TO_SERVER);
+        let _ = protocol::decrypt_body(&packet, &key, SERVER_TO_CLIENT);
+    }
+});

install.ps1

@@ -6,6 +6,12 @@ param(
     [string]$DoshHost = $(if ($env:DOSH_HOST) { $env:DOSH_HOST } else { $env:DOSH_DOSH_HOST }),
     [int]$Port = $(if ($env:DOSH_PORT) { [int]$env:DOSH_PORT } else { 50000 }),
     [string]$Prefix = $(if ($env:PREFIX) { $env:PREFIX } else { Join-Path $HOME ".local" }),
+    [switch]$UsePrebuilt = $(-not $env:DOSH_USE_PREBUILT -or $env:DOSH_USE_PREBUILT -ne "0"),
+    [string]$BinaryUrl = $env:DOSH_BINARY_URL,
+    [string]$BinaryBase = $env:DOSH_BINARY_BASE,
+    [string]$BinaryName = $env:DOSH_BINARY_NAME,
+    [string]$BinaryVersion = $(if ($env:DOSH_BINARY_VERSION) { $env:DOSH_BINARY_VERSION } else { "latest" }),
+    [switch]$BinaryRequired = $($env:DOSH_BINARY_REQUIRED -and $env:DOSH_BINARY_REQUIRED -ne "0"),
     [switch]$ForceConfig
 )
 
@@ -17,8 +23,110 @@ function Require-Command($Name) {
     }
 }
 
-Require-Command cargo
+function Normalize-Arch {
+    switch ($env:PROCESSOR_ARCHITECTURE) {
+        "AMD64" { "x86_64"; break }
+        "ARM64" { "aarch64"; break }
+        default { $env:PROCESSOR_ARCHITECTURE.ToLowerInvariant() }
+    }
+}
 
+function Release-ArtifactName {
+    if ($BinaryName) {
+        return $BinaryName
+    }
+    "dosh-windows-$(Normalize-Arch).zip"
+}
+
+function Repo-WebBase($Value) {
+    if (-not $Value) {
+        return $null
+    }
+    $base = $Value.TrimEnd("/")
+    if ($base.EndsWith(".git")) {
+        $base = $base.Substring(0, $base.Length - 4)
+    }
+    if ($base -notmatch "^https?://") {
+        return $null
+    }
+    $base
+}
+
+function Release-DownloadUrl {
+    if ($BinaryUrl) {
+        return $BinaryUrl
+    }
+    $name = Release-ArtifactName
+    if ($BinaryBase) {
+        return "$($BinaryBase.TrimEnd('/'))/$name"
+    }
+    $web = Repo-WebBase $Repo
+    if (-not $web) {
+        return $null
+    }
+    if ($BinaryVersion -eq "latest") {
+        return "$web/releases/latest/download/$name"
+    }
+    "$web/releases/download/$BinaryVersion/$name"
+}
+
+function Verify-ArchiveChecksum($Url, $Archive) {
+    $checksumPath = "$Archive.sha256"
+    try {
+        Invoke-WebRequest -UseBasicParsing -Uri "$Url.sha256" -OutFile $checksumPath
+    }
+    catch {
+        Write-Warning "prebuilt checksum unavailable; continuing without sidecar verification"
+        return
+    }
+    $expected = ((Get-Content $checksumPath -Raw).Trim() -split "\s+")[0].ToLowerInvariant()
+    $actual = (Get-FileHash -Algorithm SHA256 $Archive).Hash.ToLowerInvariant()
+    if ($expected -ne $actual) {
+        throw "prebuilt checksum mismatch for $Url"
+    }
+}
+
+$bindir = Join-Path $Prefix "bin"
+$configDir = Join-Path $HOME ".config\dosh"
+New-Item -ItemType Directory -Force -Path $bindir, $configDir | Out-Null
+
+function Install-Prebuilt {
+    $url = Release-DownloadUrl
+    if (-not $url) {
+        return $false
+    }
+    $tmp = Join-Path ([System.IO.Path]::GetTempPath()) ("dosh-bin-" + [guid]::NewGuid())
+    $zip = Join-Path $tmp (Release-ArtifactName)
+    $extract = Join-Path $tmp "extract"
+    try {
+        New-Item -ItemType Directory -Force -Path $tmp, $extract | Out-Null
+        Write-Host "Trying Dosh prebuilt $(Release-ArtifactName)"
+        Invoke-WebRequest -UseBasicParsing -Uri $url -OutFile $zip
+        Verify-ArchiveChecksum $url $zip
+        Expand-Archive -Force -Path $zip -DestinationPath $extract
+        foreach ($bin in @("dosh-client.exe", "dosh-bench.exe")) {
+            $found = Get-ChildItem -Path $extract -Recurse -File -Filter $bin | Select-Object -First 1
+            if (-not $found) {
+                throw "prebuilt archive missing $bin"
+            }
+            Copy-Item $found.FullName (Join-Path $bindir $bin) -Force
+        }
+        Copy-Item (Join-Path $bindir "dosh-client.exe") (Join-Path $bindir "dosh.exe") -Force
+        return $true
+    }
+    catch {
+        Write-Warning "prebuilt install failed: $_"
+        return $false
+    }
+    finally {
+        if (Test-Path $tmp) {
+            Remove-Item -Recurse -Force $tmp
+        }
+    }
+}
+
+function Install-FromSource {
+    Require-Command cargo
     $tmp = $null
     if (Test-Path "Cargo.toml") {
         $src = (Get-Location).Path
@@ -35,14 +143,30 @@ if (Test-Path "Cargo.toml") {
     try {
         Push-Location $src
         cargo build --release --bin dosh-client --bin dosh-bench
-
-    $bindir = Join-Path $Prefix "bin"
-    $configDir = Join-Path $HOME ".config\dosh"
-    New-Item -ItemType Directory -Force -Path $bindir, $configDir | Out-Null
-
         Copy-Item "target\release\dosh-client.exe" (Join-Path $bindir "dosh-client.exe") -Force
         Copy-Item "target\release\dosh-client.exe" (Join-Path $bindir "dosh.exe") -Force
         Copy-Item "target\release\dosh-bench.exe" (Join-Path $bindir "dosh-bench.exe") -Force
+    }
+    finally {
+        Pop-Location
+        if ($tmp) {
+            Remove-Item -Recurse -Force $tmp
+        }
+    }
+}
+
+if ($UsePrebuilt) {
+    $ok = Install-Prebuilt
+    if (-not $ok) {
+        if ($BinaryRequired) {
+            throw "prebuilt install failed and DOSH_BINARY_REQUIRED=1"
+        }
+        Write-Host "Falling back to source build"
+        Install-FromSource
+    }
+} else {
+    Install-FromSource
+}
 
 $clientConfig = Join-Path $configDir "client.toml"
 if ($ForceConfig -or -not (Test-Path $clientConfig)) {
@@ -60,6 +184,8 @@ dosh_port = $Port
 default_session = "new"
 reconnect_timeout_secs = 5
 view_only = false
+predict = true
+predict_mode = "experimental"
 cache_attach_tickets = true
 credential_cache = "~/.local/share/dosh/credentials"
 "@ | Set-Content -NoNewline -Encoding utf8 $clientConfig
@@ -78,10 +204,3 @@ credential_cache = "~/.local/share/dosh/credentials"
 Write-Host "  $bindir\dosh.exe $displayServer"
 Write-Host ""
 Write-Host "Open a new terminal for PATH changes to apply."
-}
-finally {
-    Pop-Location
-    if ($tmp) {
-        Remove-Item -Recurse -Force $tmp
-    }
-}

install.sh

@@ -12,6 +12,12 @@ start_server=1
 force_config=0
 update_cache="${DOSH_UPDATE_CACHE:-$HOME/.cache/dosh/source}"
 quiet="${DOSH_UPDATE_QUIET:-0}"
+use_prebuilt="${DOSH_USE_PREBUILT:-1}"
+binary_url="${DOSH_BINARY_URL:-}"
+binary_base="${DOSH_BINARY_BASE:-}"
+binary_name="${DOSH_BINARY_NAME:-}"
+binary_version="${DOSH_BINARY_VERSION:-latest}"
+binary_required="${DOSH_BINARY_REQUIRED:-0}"
 
 usage() {
   cat <<'EOF'
@@ -32,6 +38,18 @@ Options:
 Environment alternatives:
   DOSH_REPO, DOSH_ROLE, DOSH_SERVER, DOSH_HOST, DOSH_PORT, PREFIX,
   DOSH_UPDATE_CACHE
+  DOSH_USE_PREBUILT=0
+                  Build from source instead of trying a release tarball first
+  DOSH_BINARY_URL URL
+                  Exact release tarball URL to install
+  DOSH_BINARY_BASE URL
+                  Release download base; defaults to REPO/releases/latest/download
+  DOSH_BINARY_NAME NAME
+                  Release tarball name; defaults to dosh-OS-ARCH.tar.gz
+  DOSH_BINARY_VERSION TAG
+                  Release tag when deriving DOSH_BINARY_BASE; default latest
+  DOSH_BINARY_REQUIRED=1
+                  Fail instead of falling back to source when binary install fails
 EOF
 }
 
@@ -112,8 +130,6 @@ ensure_cargo() {
   . "$HOME/.cargo/env"
 }
 
-ensure_cargo
-
 cleanup() {
   if [ -n "${tmpdir:-}" ]; then
     rm -rf "$tmpdir"
@@ -121,6 +137,170 @@ cleanup() {
 }
 trap cleanup EXIT INT TERM
 
+bindir="$prefix/bin"
+config_dir="$HOME/.config/dosh"
+data_dir="$HOME/.local/share/dosh"
+systemd_user_dir="$HOME/.config/systemd/user"
+src_dir=""
+
+mkdir -p "$bindir" "$config_dir" "$data_dir"
+
+normalize_os() {
+  case "$(uname -s)" in
+    Darwin) printf '%s\n' macos ;;
+    Linux) printf '%s\n' linux ;;
+    FreeBSD) printf '%s\n' freebsd ;;
+    *) uname -s | tr '[:upper:]' '[:lower:]' ;;
+  esac
+}
+
+normalize_arch() {
+  case "$(uname -m)" in
+    x86_64|amd64) printf '%s\n' x86_64 ;;
+    arm64|aarch64) printf '%s\n' aarch64 ;;
+    armv7l) printf '%s\n' armv7 ;;
+    *) uname -m | tr '[:upper:]' '[:lower:]' ;;
+  esac
+}
+
+repo_web_base() {
+  repo_base="$1"
+  case "$repo_base" in
+    http://*|https://*)
+      repo_base="${repo_base%.git}"
+      printf '%s\n' "${repo_base%/}"
+      ;;
+    *)
+      return 1
+      ;;
+  esac
+}
+
+release_artifact_name() {
+  if [ -n "$binary_name" ]; then
+    printf '%s\n' "$binary_name"
+  else
+    printf 'dosh-%s-%s.tar.gz\n' "$(normalize_os)" "$(normalize_arch)"
+  fi
+}
+
+release_download_url() {
+  if [ -n "$binary_url" ]; then
+    printf '%s\n' "$binary_url"
+    return 0
+  fi
+  if [ -n "$binary_base" ]; then
+    printf '%s/%s\n' "${binary_base%/}" "$(release_artifact_name)"
+    return 0
+  fi
+  if [ -z "$repo" ]; then
+    return 1
+  fi
+  web_base="$(repo_web_base "$repo")" || return 1
+  if [ "$binary_version" = "latest" ]; then
+    printf '%s/releases/latest/download/%s\n' "$web_base" "$(release_artifact_name)"
+  else
+    printf '%s/releases/download/%s/%s\n' "$web_base" "$binary_version" "$(release_artifact_name)"
+  fi
+}
+
+release_latest_tag_download_url() {
+  if [ -n "$binary_url" ] || [ -n "$binary_base" ] || [ "$binary_version" != "latest" ] || [ -z "$repo" ]; then
+    return 1
+  fi
+  web_base="$(repo_web_base "$repo")" || return 1
+  latest_url="$(curl -fsSL -o /dev/null -w '%{url_effective}' "$web_base/releases/latest" 2>/dev/null || true)"
+  case "$latest_url" in
+    "$web_base"/releases/tag/*)
+      tag="${latest_url##"$web_base"/releases/tag/}"
+      [ -n "$tag" ] || return 1
+      printf '%s/releases/download/%s/%s\n' "$web_base" "$tag" "$(release_artifact_name)"
+      ;;
+    *)
+      return 1
+      ;;
+  esac
+}
+
+find_extracted_binary() {
+  find "$1" -type f -name "$2" 2>/dev/null | sed -n '1p'
+}
+
+install_extracted_binary() {
+  found="$(find_extracted_binary "$1" "$2")"
+  if [ -z "$found" ]; then
+    echo "prebuilt archive missing $2" >&2
+    return 1
+  fi
+  install -m 0755 "$found" "$3"
+}
+
+sha256_file() {
+  if command -v sha256sum >/dev/null 2>&1; then
+    sha256sum "$1" | awk '{print $1}'
+  elif command -v shasum >/dev/null 2>&1; then
+    shasum -a 256 "$1" | awk '{print $1}'
+  else
+    return 1
+  fi
+}
+
+verify_archive_checksum() {
+  url="$1"
+  archive="$2"
+  checksum_file="$3"
+  if ! curl -fsL "$url.sha256" -o "$checksum_file"; then
+    echo "prebuilt checksum unavailable; continuing without sidecar verification" >&2
+    return 0
+  fi
+  expected="$(awk '{print $1}' "$checksum_file" | sed -n '1p')"
+  actual="$(sha256_file "$archive")" || {
+    echo "sha256sum/shasum not found for checksum verification" >&2
+    return 1
+  }
+  if [ "$expected" != "$actual" ]; then
+    echo "prebuilt checksum mismatch for $url" >&2
+    return 1
+  fi
+}
+
+try_install_prebuilt() {
+  download_url="$(release_download_url)" || return 1
+  tmpdir="$(mktemp -d)"
+  archive="$tmpdir/$(release_artifact_name)"
+  checksum_file="$archive.sha256"
+  [ "$quiet" = "1" ] && echo "Trying Dosh prebuilt $(release_artifact_name)"
+  need curl
+  need tar
+  if ! curl -fsL "$download_url" -o "$archive" 2>/dev/null; then
+    alt_download_url="$(release_latest_tag_download_url || true)"
+    if [ -z "$alt_download_url" ] || ! curl -fsL "$alt_download_url" -o "$archive"; then
+      echo "prebuilt unavailable: $download_url" >&2
+      [ -z "$alt_download_url" ] || echo "prebuilt unavailable: $alt_download_url" >&2
+      return 1
+    fi
+    download_url="$alt_download_url"
+  fi
+  verify_archive_checksum "$download_url" "$archive" "$checksum_file" || return 1
+  mkdir -p "$tmpdir/extract"
+  if ! tar -xzf "$archive" -C "$tmpdir/extract"; then
+    echo "prebuilt archive could not be extracted: $download_url" >&2
+    return 1
+  fi
+  install_extracted_binary "$tmpdir/extract" dosh-client "$bindir/dosh-client" || return 1
+  ln -sf dosh-client "$bindir/dosh"
+  if [ "$role" = "server" ] || [ "$role" = "both" ]; then
+    install_extracted_binary "$tmpdir/extract" dosh-server "$bindir/dosh-server" || return 1
+    install_extracted_binary "$tmpdir/extract" dosh-auth "$bindir/dosh-auth" || return 1
+  fi
+  if found_bench="$(find_extracted_binary "$tmpdir/extract" dosh-bench)" && [ -n "$found_bench" ]; then
+    install -m 0755 "$found_bench" "$bindir/dosh-bench"
+  fi
+  return 0
+}
+
+install_from_source() {
+  ensure_cargo
   if [ "$from_current" -eq 1 ] || [ -f Cargo.toml ]; then
     src_dir="$(pwd)"
   else
@@ -173,13 +353,6 @@ else
     fi
   fi
 
-bindir="$prefix/bin"
-config_dir="$HOME/.config/dosh"
-data_dir="$HOME/.local/share/dosh"
-systemd_user_dir="$HOME/.config/systemd/user"
-
-mkdir -p "$bindir" "$config_dir" "$data_dir"
-
   install -m 0755 target/release/dosh-client "$bindir/dosh-client"
   ln -sf dosh-client "$bindir/dosh"
   if [ "$role" = "server" ] || [ "$role" = "both" ]; then
@@ -189,6 +362,43 @@ fi
   if [ -f target/release/dosh-bench ]; then
     install -m 0755 target/release/dosh-bench "$bindir/dosh-bench"
   fi
+}
+
+write_systemd_service() {
+  if [ -n "$src_dir" ] && [ -f "$src_dir/packaging/systemd/dosh-server.service" ]; then
+    sed "s#ExecStart=%h/.local/bin/dosh-server serve#ExecStart=$bindir/dosh-server serve#" \
+      "$src_dir/packaging/systemd/dosh-server.service" >"$systemd_user_dir/dosh-server.service"
+  else
+    cat >"$systemd_user_dir/dosh-server.service" <<EOF
+[Unit]
+Description=Dosh server
+After=network-online.target
+Wants=network-online.target
+
+[Service]
+Type=simple
+ExecStart=$bindir/dosh-server serve
+Restart=on-failure
+RestartSec=1
+KillMode=process
+
+[Install]
+WantedBy=default.target
+EOF
+  fi
+}
+
+if [ "$use_prebuilt" != "0" ]; then
+  if ! try_install_prebuilt; then
+    if [ "$binary_required" = "1" ]; then
+      exit 1
+    fi
+    [ "$quiet" = "1" ] && echo "Falling back to source build"
+    install_from_source
+  fi
+else
+  install_from_source
+fi
 
 if [ "$role" = "server" ] || [ "$role" = "both" ]; then
   server_config="$config_dir/server.toml"
@@ -226,8 +436,7 @@ EOF
 
   if command -v systemctl >/dev/null 2>&1; then
     mkdir -p "$systemd_user_dir"
-    sed "s#ExecStart=%h/.local/bin/dosh-server serve#ExecStart=$bindir/dosh-server serve#" \
-      packaging/systemd/dosh-server.service >"$systemd_user_dir/dosh-server.service"
+    write_systemd_service
     if [ "$start_server" -eq 1 ] && systemctl --user daemon-reload >/dev/null 2>&1; then
       systemctl --user enable --now dosh-server.service
     fi
@@ -272,7 +481,8 @@ dosh_port = $port
 default_session = "new"
 reconnect_timeout_secs = 5
 view_only = false
-predict = false
+predict = true
+predict_mode = "experimental"
 cache_attach_tickets = true
 credential_cache = "~/.local/share/dosh/credentials"
 auth_preference = "native,ssh"
@@ -295,18 +505,18 @@ EOF
     fi
     cat >"$hosts_config" <<EOF
 # Example:
-# [palav]
-# ssh = "palav"
-# dosh_host = "palav.dev"
+# [homelab]
+# ssh = "homelab"
+# dosh_host = "server.example.com"
 # port = 50000
 # default_command = "tm"
-# predict = false
+# predict = true
 
 [default]
 ssh = "$default_server"
 dosh_host = "$host_udp"
 port = $port
-predict = false
+predict = true
 EOF
   fi
 fi

llms.txt

@@ -0,0 +1,201 @@
+# dosh (Dormant Shell)
+
+> dosh is a low-latency remote terminal for homelab/personal servers. It is mosh-shaped
+> but not a mosh clone: `dosh-server` is a resident daemon that keeps terminal sessions
+> hot, and the client reconnects over encrypted UDP — so attach and reconnect are
+> near-instant (~3 ms of local overhead + one network RTT). SSH is used once to
+> establish trust; after that, repeat attaches skip SSH entirely. It also does SSH-style
+> TCP port forwarding (`-L`/`-R`/`-D`) over the same encrypted transport, which is what
+> makes back-and-forth client↔server homelab comms easy.
+
+This file orients an AI agent (or a human) on what dosh is, what it can do, and how to
+drive it. It is intentionally self-contained. For deeper detail, see the linked docs at
+the bottom.
+
+## What dosh is for
+
+Use dosh instead of `ssh`/`mosh` for **interactive shells and TCP forwarding** to a
+server where you control both ends and have installed `dosh-server` (typically a homelab
+box, VPS, or workstation). It shines when you:
+
+- want a terminal that survives laptop sleep, Wi-Fi changes, and NAT rebinding, and
+  resumes instantly instead of hanging;
+- reconnect to the same box many times a day and don't want to pay SSH startup each time;
+- need to reach services on the server from your laptop (or vice-versa) without standing
+  up a VPN.
+
+dosh is **not** a drop-in for every SSH use. It does not do `scp`/`sftp` file transfer,
+X11, or act as an `sshd` for arbitrary SSH clients. Keep `ssh` installed for those.
+
+## Core capabilities
+
+- **Encrypted UDP terminal transport** — AEAD-encrypted, with packet sequencing, a
+  sliding replay window, ACKs, and server-side retransmit of unacked output.
+- **Resident server + hot sessions** — `dosh-server` runs as a daemon; named sessions
+  (and a prewarmed `default`) stay alive across client disconnects.
+- **Fast attach / reconnect** — see "Fast path order" below; cached attach is ~one RTT.
+- **Roaming** — the session follows the client across IP/port changes.
+- **Named & shared sessions** — reattach the same persistent terminal from multiple
+  clients; optional **view-only** clients.
+- **TCP port forwarding** — local (`-L`), remote (`-R`), and dynamic SOCKS (`-D`) over
+  the encrypted transport, with per-stream flow control and terminal-priority
+  scheduling (bulk transfers don't lag your keystrokes).
+- **Native UDP auth** — Ed25519 user auth via ssh-agent or an (optionally encrypted)
+  OpenSSH key, verified against `authorized_keys`. Falls back to SSH bootstrap when
+  native auth isn't available. SSH host config (`HostName`, `User`, `Port`,
+  `IdentityFile`, `ProxyJump`, etc.) is honored.
+- **Host-key pinning** — TOFU/known-hosts with hard-fail on mismatch.
+- **Speculative local echo** — optional predictive echo for laggy links (display-only;
+  real input is always sent to the server).
+- **Ops commands** — `doctor`, `sessions`, `trust`, `import-ssh`, `update`.
+
+## Quickstart
+
+Install the server on each box you want to reach (default UDP port `50000`):
+
+```bash
+curl -fsSL https://git.palav.dev/Palav/dosh/raw/branch/main/install.sh \
+  | DOSH_PORT=50000 sh -s -- server
+```
+
+Install the client (macOS/Linux), then attach:
+
+```bash
+curl -fsSL https://git.palav.dev/Palav/dosh/raw/branch/main/install.sh \
+  | DOSH_SERVER=homelab DOSH_HOST=homelab.example.com DOSH_PORT=50000 sh -s -- client
+
+dosh homelab                 # fresh interactive shell
+dosh homelab uptime          # run one command
+dosh --session work homelab  # named, persistent, reattachable session
+```
+
+- Detach (leave the server session running): **Ctrl-]**.
+- End the session: type `exit` in the remote shell.
+- If UDP stalls, dosh keeps the terminal open, sends keepalives, and ticket-reconnects.
+
+## Client↔server homelab comms (the back-and-forth)
+
+Forwarding is the key to "make homelab comms easy." Three directions:
+
+| Command | Direction | Effect |
+| --- | --- | --- |
+| `dosh -L [bind:]LPORT:THOST:TPORT host` | pull server→you | A listener on **your machine** (`bind`, default localhost) forwards to `THOST:TPORT` reached **from the server**. |
+| `dosh -R [bind:]LPORT:THOST:TPORT host` | push you→server | A listener on **the server** (loopback by default) forwards to `THOST:TPORT` reached **from your machine**. |
+| `dosh -D [bind:]LPORT host` | SOCKS via server | A SOCKS5 proxy on **your machine**; traffic egresses **from the server**. |
+
+Concrete homelab patterns:
+
+```bash
+# Reach the homelab's internal Grafana (server-side :3000) from your laptop browser:
+dosh -L 3000:127.0.0.1:3000 homelab            # open http://localhost:3000
+
+# Reach a DB that only listens on the homelab LAN:
+dosh -L 5432:10.0.0.5:5432 homelab             # psql -h 127.0.0.1 -p 5432
+
+# Let the homelab hit a dev server running on your laptop (e.g. a webhook target):
+dosh -R 9000:127.0.0.1:8080 homelab           # homelab curls http://127.0.0.1:9000
+
+# Route browser traffic out through the homelab's network:
+dosh -D 1080 homelab                           # SOCKS5 proxy at 127.0.0.1:1080
+
+# Forward-only, no shell; multiple forwards; background after listeners are up:
+dosh -N -L 3000:127.0.0.1:3000 -L 5432:10.0.0.5:5432 homelab
+dosh -f -N -L 3000:127.0.0.1:3000 homelab
+```
+
+Server policy controls forwarding: `allow_tcp_forwarding`, `allow_remote_forwarding`,
+`allow_remote_non_loopback_bind`, and per-key `permitopen=`/`no-port-forwarding` in
+`authorized_keys`. Remote listeners bind to loopback unless explicitly allowed.
+
+## Fast path order (why it's quick)
+
+The client tries the cheapest valid path first:
+
+1. **UDP resume** — existing client id + session key; one encrypted UDP round-trip.
+2. **UDP attach ticket** — cached server-issued ticket; one round-trip, no SSH.
+3. **Native UDP auth** — Ed25519 handshake (ssh-agent/key) when enabled.
+4. **SSH bootstrap** — `ssh user@host dosh-auth …` once, then a UDP attach.
+
+Measured locally (loopback, release): cached attach ≈ **3 ms**, cold native auth ≈ 9 ms.
+Over a real link, add one RTT. See `docs/BENCHMARKS.md`.
+
+## Architecture (1-minute model)
+
+- **dosh-server** — single UDP socket on one port; a session table keyed by name; one
+  PTY per named session; per-session terminal screen state (vt100) for snapshots/diffs;
+  a per-session client table; encrypted UDP protocol; a small SSH-invoked `dosh-auth`
+  helper. Abandoned (clientless, non-prewarmed) sessions and their shells are reaped
+  after a grace period; prewarmed sessions stay hot.
+- **dosh-client** — raw-mode terminal; local credential cache; tries resume/ticket/native
+  before SSH; forwards PTY I/O; reconnect/roaming state machine; optional predictive echo.
+- **Binaries** — `dosh-server`, `dosh-client` (symlinked as `dosh`), `dosh-auth`
+  (SSH-invoked trust helper), `dosh-bench` (benchmarks).
+
+## Security model (summary)
+
+- First trust via SSH; thereafter encrypted Dosh transport. Native auth available.
+- KEX X25519; AEAD ChaCha20-Poly1305; KDF HKDF-SHA256; host & user auth Ed25519;
+  SHA-256 transcript binding. Per-direction, per-sequence nonces; replay window.
+- Host keys pinned in `~/.config/dosh/known_hosts`; mismatch hard-fails.
+- User auth against `~/.ssh/authorized_keys` (+ optional `~/.config/dosh/authorized_keys`);
+  removed keys can't authenticate; unsupported restrictive options fail closed.
+- Forward secrecy from ephemeral X25519; attach tickets are server-sealed and scoped.
+
+dosh claims security **equivalent to, and in places stronger than, SSH for the dosh
+terminal/forwarding use case** — not full SSH-protocol parity. Read `docs/THREAT_MODEL.md`
+for the honest stance, residual risks, and what's still pending before public claims.
+
+## Configuration
+
+- **Client** `~/.config/dosh/client.toml` — `auth_preference` (e.g. `"native,ssh"`),
+  `trust_on_first_use`, `identity_files`, `use_ssh_agent`, `forward_agent`, `send_env`,
+  `set_env`, `dosh_port`, `default_session`, `predict`, `reconnect_timeout_secs`,
+  `credential_cache`, `known_hosts`.
+- **Hosts** `~/.config/dosh/hosts.toml` — per-alias `[name]` with `ssh`, `dosh_host`,
+  `port`, `user`, `default_command`, `predict`. Generate from SSH aliases with
+  `dosh import-ssh <alias> <name>`.
+- **Server** `~/.config/dosh/server.toml` — `port`, `bind`, `shell`, `prewarm_sessions`,
+  `native_auth`, `host_key`, `authorized_keys`, `attach_ticket_ttl_secs`,
+  `client_timeout_secs`, `allow_tcp_forwarding`, `allow_remote_forwarding`,
+  `allow_remote_non_loopback_bind`, `allow_agent_forwarding`, `accept_env`,
+  `native_auth_rate_limit_per_minute`.
+
+Paths: host key `~/.config/dosh/host_key`; credential cache
+`~/.local/share/dosh/credentials/`.
+
+## Operating & diagnostics
+
+```bash
+dosh doctor homelab     # host resolution, trust state, UDP reachability, server
+                        # version, usable keys, auth result, forwarding policy
+dosh sessions homelab   # list live sessions
+dosh trust homelab      # fetch + pin the Dosh host key (via SSH fallback)
+dosh trust --remove homelab
+dosh import-ssh homelab   # write a hosts.toml entry from an SSH alias
+dosh update             # update the installed client
+```
+
+If something fails, `dosh doctor <host>` is the first stop — every public error is meant
+to be actionable (host trust, auth failure, UDP blocked, forwarding denied, version
+mismatch, server unavailable).
+
+## For agents driving dosh
+
+- Run one command and exit: `dosh <host> <cmd...>`. Render one frame and detach:
+  `dosh --attach-only <host>`. Both are non-interactive-friendly.
+- A real terminal size is needed for full-screen rendering; with no TTY the client falls
+  back to 80×24. Pass `-v`/`-vv` for timing/diagnostic logs on stderr.
+- Prefer `--session <name>` to reattach a known session; bare `dosh <host>` opens a
+  fresh, uniquely-named session each time.
+- Never assume file transfer or X11 — use `ssh`/`scp` for those.
+- Diagnostics are scriptable via `dosh doctor <host>`.
+
+## Reference docs
+
+- `README.md` — overview, install, develop, performance rules.
+- `docs/NATIVE_V1_SPEC.md` — the native auth + forwarding v1 contract and verification
+  checklist (with current status).
+- `docs/THREAT_MODEL.md` — security claims, threat model, residual risks.
+- `docs/PUBLIC_READINESS.md` — feature matrix and §16 verification status.
+- `docs/BENCHMARKS.md` — how to benchmark; metric definitions; sample numbers.
+- `SPEC.md` — protocol/wire details.

scripts/bench-local.sh

@@ -0,0 +1,192 @@
+#!/usr/bin/env sh
+# Safe, self-contained local Dosh benchmark harness.
+#
+# Spins up a THROWAWAY dosh-server bound to 127.0.0.1 on a random free port in a
+# temp HOME, runs the full path matrix (native cold auth, cached attach-ticket,
+# UDP resume, and local-auth), prints raw samples + summary stats, then tears
+# everything down.
+#
+# It NEVER touches the production server: it never uses UDP port 50000, never
+# restarts any systemd unit, and never reads or writes the real ~/.config/dosh
+# or ~/.local. Everything lives under a mktemp HOME that is removed on exit.
+#
+# Usage:
+#   scripts/bench-local.sh [ITERATIONS]
+# Environment:
+#   DOSH_BENCH_ITERS   iteration count (default 20; overridden by $1)
+#   DOSH_BENCH_JSON=1  emit machine-readable JSON instead of the table
+#   DOSH_BENCH_PROFILE release|debug build profile (default release)
+set -eu
+
+iters="${1:-${DOSH_BENCH_ITERS:-20}}"
+profile="${DOSH_BENCH_PROFILE:-release}"
+
+repo_root="$(cd "$(dirname "$0")/.." && pwd)"
+cd "$repo_root"
+
+# Make sure cargo is reachable in non-login shells.
+if ! command -v cargo >/dev/null 2>&1; then
+  # shellcheck disable=SC1090
+  [ -f "$HOME/.cargo/env" ] && . "$HOME/.cargo/env"
+fi
+
+if [ "$profile" = "release" ]; then
+  cargo build --release >&2
+  bindir="$repo_root/target/release"
+else
+  cargo build >&2
+  bindir="$repo_root/target/debug"
+fi
+server_bin="$bindir/dosh-server"
+client_bin="$bindir/dosh-client"
+bench_bin="$bindir/dosh-bench"
+
+# Pick a free UDP port that is NOT the production port (50000).
+free_udp_port() {
+  python3 - <<'PY'
+import socket
+s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+s.bind(("127.0.0.1", 0))
+print(s.getsockname()[1])
+s.close()
+PY
+}
+dosh_port="$(free_udp_port)"
+if [ "$dosh_port" = "50000" ]; then
+  dosh_port="$(free_udp_port)"
+fi
+if [ "$dosh_port" = "50000" ]; then
+  echo "refusing to bind production port 50000" >&2
+  exit 1
+fi
+
+home="$(mktemp -d)"
+server_pid=""
+cleanup() {
+  if [ -n "$server_pid" ]; then
+    kill "$server_pid" 2>/dev/null || true
+    wait "$server_pid" 2>/dev/null || true
+  fi
+  rm -rf "$home"
+}
+trap cleanup EXIT INT TERM
+
+mkdir -p "$home/.config/dosh" "$home/.ssh" "$home/.local/share/dosh"
+
+# Client identity used by the native cold-auth path.
+ssh-keygen -t ed25519 -N "" -q -f "$home/.ssh/id_ed25519"
+client_pub="$(cat "$home/.ssh/id_ed25519.pub")"
+printf '%s\n' "$client_pub" > "$home/authorized_keys"
+
+# Throwaway server config: localhost only, throwaway port, attach tickets on.
+cat > "$home/.config/dosh/server.toml" <<EOF
+port = $dosh_port
+bind = "127.0.0.1"
+scrollback = 5000
+auth_ttl_secs = 30
+attach_ticket_ttl_secs = 3600
+allow_attach_tickets = true
+client_timeout_secs = 60
+retransmit_window = 256
+default_input_mode = "read-write"
+prewarm_sessions = ["default"]
+create_on_attach = true
+shell = "/bin/sh"
+sessions_dir = "$home/sessions"
+secret_path = "$home/secret"
+host_key = "$home/host_key"
+authorized_keys = ["$home/authorized_keys"]
+EOF
+
+# Client config: native auth, trust-on-first-use (no SSH needed), localhost UDP.
+write_client_config() {
+  # $1 = cache_attach_tickets (true|false)
+  cat > "$home/.config/dosh/client.toml" <<EOF
+server = "local"
+dosh_host = "127.0.0.1"
+dosh_port = $dosh_port
+default_session = "default"
+reconnect_timeout_secs = 5
+view_only = false
+predict = false
+cache_attach_tickets = $1
+credential_cache = "$home/.local/share/dosh/credentials"
+known_hosts = "$home/.config/dosh/known_hosts"
+auth_preference = "native"
+trust_on_first_use = true
+EOF
+}
+
+start_server() {
+  HOME="$home" "$server_bin" serve --config "$home/.config/dosh/server.toml" \
+    >"$home/server.log" 2>&1 &
+  server_pid="$!"
+  # Wait for the UDP socket to come up.
+  i=0
+  while [ "$i" -lt 50 ]; do
+    if grep -q "listening on" "$home/server.log" 2>/dev/null; then
+      return 0
+    fi
+    if ! kill -0 "$server_pid" 2>/dev/null; then
+      echo "dosh-server exited early:" >&2
+      cat "$home/server.log" >&2 || true
+      exit 1
+    fi
+    i=$((i + 1))
+    sleep 0.1
+  done
+}
+
+run_bench() {
+  # $@ extra args forwarded to dosh-bench
+  json_flag=""
+  [ "${DOSH_BENCH_JSON:-0}" = "1" ] && json_flag="--json"
+  label="$(uname -s) $(uname -m), profile=$profile"
+  HOME="$home" "$bench_bin" \
+    --client "$client_bin" \
+    --server local \
+    --dosh-host 127.0.0.1 \
+    --dosh-port "$dosh_port" \
+    --session default \
+    --skip-ssh-baseline \
+    --iterations "$iters" \
+    --label "$label" \
+    $json_flag \
+    "$@"
+}
+
+echo "dosh local benchmark: port=$dosh_port iters=$iters profile=$profile home=$home" >&2
+
+# 1) Native cold auth + cached attach-ticket in one run (ticket cache on).
+write_client_config true
+start_server
+echo "== native cold auth + cached attach-ticket ==" >&2
+run_bench --cold-native --cached-ticket
+# Sanity: native cold auth must have trusted the host (proves the generated
+# client config loaded and the native handshake ran instead of silently
+# falling back to a different path).
+if [ ! -s "$home/.config/dosh/known_hosts" ]; then
+  echo "native cold auth did not record a trusted host; check server.log:" >&2
+  cat "$home/server.log" >&2 || true
+  exit 1
+fi
+kill "$server_pid" 2>/dev/null || true
+wait "$server_pid" 2>/dev/null || true
+server_pid=""
+
+# 2) Self-contained local-auth path (no SSH, no native handshake).
+#
+# Note on UDP resume: resume is the roaming path for a client that is STILL
+# attached when its network endpoint changes. The `--attach-only` benchmark
+# model detaches after each iteration, which tears the client down on the
+# server, so a fresh-process resume has nothing live to resume and is not
+# meaningful here. The cold fresh-process reconnect fast path is the attach
+# ticket (measured above). Roaming resume is validated by the integration test
+# `resume_updates_udp_endpoint_for_roaming`. `dosh-bench --resume` exists for
+# scenarios that keep a live session out-of-band (e.g. remote soak tests); see
+# docs/BENCHMARKS.md.
+rm -rf "$home/.local/share/dosh/credentials"
+write_client_config true
+start_server
+echo "== local-auth (no SSH) ==" >&2
+run_bench --local-auth --no-cache

scripts/bench-report.sh

@@ -0,0 +1,21 @@
+#!/usr/bin/env sh
+set -eu
+
+repo_root="$(CDPATH= cd -- "$(dirname -- "$0")/.." && pwd)"
+cd "$repo_root"
+
+out="${DOSH_BENCH_REPORT:-target/dosh-bench/report.md}"
+iters="${DOSH_BENCH_ITERS:-10}"
+server="${DOSH_BENCH_SERVER:-${1:-local}}"
+label="${DOSH_BENCH_LABEL:-$(uname -s) $(uname -m)}"
+
+cargo build --release >/dev/null
+mkdir -p "$(dirname "$out")"
+
+exec target/release/dosh-bench \
+  --server "$server" \
+  --iterations "$iters" \
+  --label "$label" \
+  --markdown \
+  --output "$out" \
+  ${DOSH_BENCH_ARGS:-}

scripts/ci-docker-ssh-bench.sh

@@ -31,7 +31,7 @@ for _ in 1 2 3 4 5; do
 done
 
 ssh-keyscan -p "$ssh_port" 127.0.0.1 > "$workdir/known_hosts"
-mkdir -p "$workdir/home" "$workdir/home-controlmaster" "$workdir/home-cached" "$workdir/home-mosh"
+mkdir -p "$workdir/home" "$workdir/home-controlmaster" "$workdir/home-native" "$workdir/home-cached" "$workdir/home-mosh"
 
 if ! HOME="$workdir/home" target/release/dosh-bench \
     --server bench@127.0.0.1 \
@@ -64,6 +64,32 @@ if ! HOME="$workdir/home-controlmaster" target/release/dosh-bench \
   exit 1
 fi
 
+if ! HOME="$workdir/home-native" target/release/dosh-client \
+    --ssh-port "$ssh_port" \
+    --ssh-key "$workdir/id_ed25519" \
+    --ssh-known-hosts "$workdir/known_hosts" \
+    --ssh-auth-command /usr/local/bin/dosh-auth \
+    trust bench@127.0.0.1 >/dev/null; then
+  docker logs "$container_id" || true
+  docker exec "$container_id" sh -lc 'cat /tmp/dosh-server.log 2>/dev/null || true' || true
+  exit 1
+fi
+
+if ! HOME="$workdir/home-native" target/release/dosh-bench \
+    --server bench@127.0.0.1 \
+    --ssh-port "$ssh_port" \
+    --dosh-port "$dosh_port" \
+    --dosh-host 127.0.0.1 \
+    --ssh-key "$workdir/id_ed25519" \
+    --ssh-known-hosts "$workdir/known_hosts" \
+    --iterations 5 \
+    --cold-native \
+    --assert-ssh-plus-ms "${DOSH_BENCH_NATIVE_SSH_PLUS_MS:-0}"; then
+  docker logs "$container_id" || true
+  docker exec "$container_id" sh -lc 'cat /tmp/dosh-server.log 2>/dev/null || true' || true
+  exit 1
+fi
+
 if ! HOME="$workdir/home-cached" target/release/dosh-bench \
     --server bench@127.0.0.1 \
     --ssh-port "$ssh_port" \

scripts/fuzz-run.sh

@@ -0,0 +1,22 @@
+#!/usr/bin/env sh
+set -eu
+
+seconds="${DOSH_FUZZ_SECONDS:-${1:-20}}"
+targets="
+packet_decode
+from_body
+authorized_keys
+known_hosts
+handshake_structs
+attach_ticket
+"
+
+if ! command -v cargo >/dev/null 2>&1; then
+  [ -f "$HOME/.cargo/env" ] && . "$HOME/.cargo/env"
+fi
+
+for target in $targets; do
+  echo "== fuzzing $target for ${seconds}s =="
+  cargo +nightly fuzz run --fuzz-dir fuzz "$target" -- \
+    -max_total_time="$seconds" -rss_limit_mb="${DOSH_FUZZ_RSS_MB:-4096}"
+done

scripts/package-release.sh

@@ -0,0 +1,85 @@
+#!/usr/bin/env sh
+set -eu
+
+repo_root="$(CDPATH= cd -- "$(dirname -- "$0")/.." && pwd)"
+cd "$repo_root"
+
+out_dir="${DOSH_PACKAGE_DIR:-target/dosh-release}"
+version="${DOSH_VERSION:-$(sed -n 's/^version = "\(.*\)"/\1/p' Cargo.toml | sed -n '1p')}"
+
+normalize_os() {
+  case "$(uname -s)" in
+    Darwin) printf '%s\n' macos ;;
+    Linux) printf '%s\n' linux ;;
+    FreeBSD) printf '%s\n' freebsd ;;
+    MINGW*|MSYS*|CYGWIN*) printf '%s\n' windows ;;
+    *) uname -s | tr '[:upper:]' '[:lower:]' ;;
+  esac
+}
+
+normalize_arch() {
+  case "$(uname -m)" in
+    x86_64|amd64) printf '%s\n' x86_64 ;;
+    arm64|aarch64) printf '%s\n' aarch64 ;;
+    armv7l) printf '%s\n' armv7 ;;
+    *) uname -m | tr '[:upper:]' '[:lower:]' ;;
+  esac
+}
+
+os="$(normalize_os)"
+arch="$(normalize_arch)"
+if [ "$os" = "windows" ]; then
+  artifact="dosh-$os-$arch.zip"
+  versioned_artifact="dosh-$version-$os-$arch.zip"
+else
+  artifact="dosh-$os-$arch.tar.gz"
+  versioned_artifact="dosh-$version-$os-$arch.tar.gz"
+fi
+stage="$out_dir/stage/dosh"
+
+cargo build --release
+
+rm -rf "$stage"
+mkdir -p "$stage/bin" "$out_dir"
+for bin in dosh-client dosh-server dosh-auth dosh-bench; do
+  if [ -f "target/release/$bin" ]; then
+    install -m 0755 "target/release/$bin" "$stage/bin/$bin"
+  fi
+done
+printf '%s\n' "$version" >"$stage/VERSION"
+
+if [ "$os" = "windows" ]; then
+  if command -v powershell.exe >/dev/null 2>&1; then
+    powershell.exe -NoProfile -Command "Compress-Archive -Force -Path '$stage' -DestinationPath '$out_dir/$artifact'"
+  elif command -v zip >/dev/null 2>&1; then
+    (cd "$out_dir/stage" && zip -qr "../$artifact" dosh)
+  else
+    echo "windows packaging requires powershell.exe or zip" >&2
+    exit 1
+  fi
+else
+  tar -C "$out_dir/stage" -czf "$out_dir/$artifact" dosh
+fi
+cp "$out_dir/$artifact" "$out_dir/$versioned_artifact"
+
+write_sha256() {
+  file="$1"
+  if command -v sha256sum >/dev/null 2>&1; then
+    sha256sum "$file" >"$file.sha256"
+  elif command -v shasum >/dev/null 2>&1; then
+    shasum -a 256 "$file" >"$file.sha256"
+  else
+    echo "warning: sha256sum/shasum not found; skipping checksum for $file" >&2
+  fi
+}
+
+write_sha256 "$out_dir/$artifact"
+write_sha256 "$out_dir/$versioned_artifact"
+
+cat <<EOF
+Wrote:
+  $out_dir/$artifact
+  $out_dir/$artifact.sha256
+  $out_dir/$versioned_artifact
+  $out_dir/$versioned_artifact.sha256
+EOF

scripts/upload-gitea-release.sh

@@ -0,0 +1,98 @@
+#!/usr/bin/env sh
+set -eu
+
+usage() {
+  cat <<'EOF'
+Usage:
+  GITEA_TOKEN=... scripts/upload-gitea-release.sh TAG [artifact...]
+
+Environment:
+  GITEA_URL       Base URL, default https://git.palav.dev
+  GITEA_REPO      owner/repo, default Palav/dosh
+  GITEA_TOKEN     Token with release write permission
+  GITEA_TITLE     Release title, default TAG
+EOF
+}
+
+if [ "${1:-}" = "-h" ] || [ "${1:-}" = "--help" ]; then
+  usage
+  exit 0
+fi
+
+tag="${1:-}"
+if [ -z "$tag" ]; then
+  usage >&2
+  exit 2
+fi
+shift
+
+base="${GITEA_URL:-https://git.palav.dev}"
+repo="${GITEA_REPO:-Palav/dosh}"
+token="${GITEA_TOKEN:-}"
+title="${GITEA_TITLE:-$tag}"
+
+if [ -z "$token" ]; then
+  echo "GITEA_TOKEN is required" >&2
+  exit 2
+fi
+
+if [ "$#" -eq 0 ]; then
+  set -- target/dosh-release/dosh-*
+fi
+
+api="$base/api/v1/repos/$repo"
+auth_header="Authorization: token $token"
+
+release_json="$(curl -fsS -H "$auth_header" "$api/releases/tags/$tag" || true)"
+release_id=""
+if [ -n "$release_json" ] && command -v jq >/dev/null 2>&1; then
+  release_id="$(printf '%s\n' "$release_json" | jq -r '.id // empty')"
+elif [ -n "$release_json" ]; then
+  release_id="$(printf '%s\n' "$release_json" | sed -n 's/^[[:space:]]*{"id":[[:space:]]*\([0-9][0-9]*\).*/\1/p' | sed -n '1p')"
+fi
+
+if [ -z "$release_id" ]; then
+  payload="$(printf '{"tag_name":"%s","target_commitish":"main","name":"%s","body":"Dosh release %s","draft":false,"prerelease":false}\n' "$tag" "$title" "$tag")"
+  release_json="$(curl -fsS -H "$auth_header" -H 'Content-Type: application/json' -X POST "$api/releases" -d "$payload")"
+  if command -v jq >/dev/null 2>&1; then
+    release_id="$(printf '%s\n' "$release_json" | jq -r '.id // empty')"
+  else
+    release_id="$(printf '%s\n' "$release_json" | sed -n 's/^[[:space:]]*{"id":[[:space:]]*\([0-9][0-9]*\).*/\1/p' | sed -n '1p')"
+  fi
+fi
+
+if [ -z "$release_id" ]; then
+  echo "could not determine Gitea release id for $tag" >&2
+  exit 1
+fi
+
+delete_existing_asset() {
+  name="$1"
+  if ! command -v jq >/dev/null 2>&1; then
+    return 0
+  fi
+  printf '%s\n' "$release_json" \
+    | jq -r --arg name "$name" '.assets[]? | select(.name == $name) | .id' \
+    | while IFS= read -r asset_id; do
+      [ -n "$asset_id" ] || continue
+      echo "replacing $name"
+      curl -fsS \
+        -H "$auth_header" \
+        -X DELETE \
+        "$api/releases/$release_id/assets/$asset_id" >/dev/null
+    done
+}
+
+for artifact in "$@"; do
+  if [ ! -f "$artifact" ]; then
+    continue
+  fi
+  name="$(basename "$artifact")"
+  delete_existing_asset "$name"
+  echo "uploading $name"
+  curl -fsS \
+    -H "$auth_header" \
+    -X POST \
+    -F "attachment=@$artifact" \
+    "$api/releases/$release_id/assets?name=$name" >/dev/null
+done

src/auth.rs

@@ -68,6 +68,12 @@ pub fn load_or_create_server_secret(config: &ServerConfig) -> Result<[u8; 32]> {
                 .decode(String::from_utf8_lossy(&raw).trim())
                 .context("decode server secret")?
         };
+        anyhow::ensure!(
+            decoded.len() == 32,
+            "server secret at {} must be 32 bytes, got {}",
+            path.display(),
+            decoded.len()
+        );
         let mut out = [0u8; 32];
         out.copy_from_slice(&decoded[..32]);
         return Ok(out);

src/bin/dosh-bench.rs

@@ -2,6 +2,8 @@ use anyhow::{Context, Result, anyhow};
 use clap::Parser;
 use portable_pty::{CommandBuilder, NativePtySystem, PtySize, PtySystem};
 use std::ffi::OsStr;
+use std::fmt::Write as _;
+use std::fs;
 use std::io::Read;
 use std::path::PathBuf;
 use std::process::Command;
@@ -25,6 +27,15 @@ struct Args {
     iterations: usize,
     #[arg(long)]
     local_auth: bool,
+    /// Benchmark native cold auth (no cache, native handshake) terminal-ready time.
+    #[arg(long)]
+    cold_native: bool,
+    /// Benchmark cached attach-ticket terminal-ready time (warms the cache first).
+    #[arg(long)]
+    cached_ticket: bool,
+    /// Benchmark UDP resume terminal-ready time (warms the cache first).
+    #[arg(long)]
+    resume: bool,
     #[arg(long)]
     client: Option<PathBuf>,
     #[arg(long, default_value = "~/.local/bin/dosh-auth")]
@@ -51,6 +62,18 @@ struct Args {
     mosh_server_command: String,
     #[arg(long)]
     mosh_port: Option<String>,
+    /// Emit machine-readable JSON (one object per metric, with raw samples).
+    #[arg(long)]
+    json: bool,
+    /// Emit a publishable Markdown benchmark report.
+    #[arg(long)]
+    markdown: bool,
+    /// Write the report to a file instead of stdout.
+    #[arg(long)]
+    output: Option<PathBuf>,
+    /// Optional label printed in summary/JSON output (e.g. machine/OS identifier).
+    #[arg(long)]
+    label: Option<String>,
     #[arg(long)]
     assert_ssh_plus_ms: Option<f64>,
     #[arg(long)]
@@ -59,12 +82,45 @@ struct Args {
     assert_dosh_max_ms: Option<f64>,
 }
 
+/// One Dosh attach path to benchmark.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+enum DoshPath {
+    /// `--auth native --no-cache`: full native handshake, no cache.
+    ColdNative,
+    /// Cached attach-ticket fast path (requires a warmed cache).
+    CachedTicket,
+    /// UDP resume fast path (requires a warmed cache + `cache_attach_tickets = false`).
+    Resume,
+    /// `--local-auth`: self-contained local bootstrap, no SSH.
+    LocalAuth,
+    /// SSH-bootstrap cold attach (cache controlled by `--no-cache` / `--warm-cache`).
+    SshBootstrap,
+}
+
+impl DoshPath {
+    fn metric(self) -> &'static str {
+        match self {
+            DoshPath::ColdNative => "dosh_cold_native_ms",
+            DoshPath::CachedTicket => "dosh_cached_attach_ms",
+            DoshPath::Resume => "dosh_resume_ms",
+            DoshPath::LocalAuth => "dosh_local_attach_ms",
+            DoshPath::SshBootstrap => "dosh_attach_ms",
+        }
+    }
+
+    /// Whether this path consumes a warmed credential cache.
+    fn needs_warm(self) -> bool {
+        matches!(self, DoshPath::CachedTicket | DoshPath::Resume)
+    }
+}
+
 fn main() -> Result<()> {
     let args = Args::parse();
     let client = args.client.clone().unwrap_or_else(default_client_path);
-    let mut ssh_times = Vec::new();
-    let mut dosh_times = Vec::new();
-    let mut mosh_times = Vec::new();
+    if args.no_cache && args.warm_cache {
+        return Err(anyhow!("--warm-cache cannot be used with --no-cache"));
+    }
+
     let generated_control_path = if args.controlmaster {
         Some(std::env::temp_dir().join(format!("dosh-bench-control-{}", std::process::id())))
     } else {
@@ -78,96 +134,115 @@ fn main() -> Result<()> {
     } else {
         None
     };
-    if args.no_cache && args.warm_cache {
-        return Err(anyhow!("--warm-cache cannot be used with --no-cache"));
-    }
-    let dosh_label = if args.warm_cache {
-        let _ = time_dosh_attach(&client, &args, control_path)?;
-        "dosh_cached_attach_ms"
+
+    // Resolve which Dosh paths to benchmark. Explicit path flags select an
+    // explicit matrix; otherwise fall back to the legacy single-path behavior
+    // so existing callers (CI docker scripts) keep working unchanged.
+    let explicit_paths = explicit_dosh_paths(&args);
+    let dosh_paths = if explicit_paths.is_empty() {
+        vec![legacy_dosh_path(&args)]
     } else {
-        "dosh_attach_ms"
+        explicit_paths
     };
 
+    let mut results: Vec<MetricSamples> = Vec::new();
+
+    // SSH baseline (shared across the matrix; the comparison is per-iteration
+    // ssh-true vs the dosh path startup that replaces it).
+    let run_ssh = !args.local_auth && !args.skip_ssh_baseline && !dosh_only(&dosh_paths);
+    if run_ssh {
+        let mut ssh_times = Vec::new();
         for _ in 0..args.iterations.max(1) {
-        if !args.local_auth && !args.skip_ssh_baseline {
             let mut ssh = Command::new("ssh");
             add_ssh_options(&mut ssh, &args, control_path);
             ssh.arg(&args.server).arg("true");
             ssh_times.push(time_command(&mut ssh)?);
         }
+        results.push(MetricSamples::new("ssh_true_ms", ssh_times));
+    }
 
-        dosh_times.push(time_dosh_attach(&client, &args, control_path)?);
+    for path in &dosh_paths {
+        if path.needs_warm() {
+            // Prime the cache with one attach so the fast path has credentials.
+            let _ = time_dosh_attach(&client, &args, *path, control_path, true)?;
+        }
+        let mut samples = Vec::new();
+        for _ in 0..args.iterations.max(1) {
+            samples.push(time_dosh_attach(
+                &client,
+                &args,
+                *path,
+                control_path,
+                false,
+            )?);
+        }
+        results.push(MetricSamples::new(path.metric(), samples));
+    }
 
     if args.include_mosh {
+        let mut mosh_times = Vec::new();
+        for _ in 0..args.iterations.max(1) {
             mosh_times.push(time_mosh_in_pty(&args)?);
         }
+        results.push(MetricSamples::new("mosh_start_true_ms", mosh_times));
+    }
+
+    let report = if args.json {
+        render_json(&args, &results)
+    } else if args.markdown {
+        render_markdown(&args, &results)
+    } else {
+        render_table(&args, &results)
+    };
+    write_report(&args, &report)?;
+
+    run_assertions(&args, &results)?;
+    Ok(())
+}
+
+/// Paths explicitly requested via flags.
+fn explicit_dosh_paths(args: &Args) -> Vec<DoshPath> {
+    let mut paths = Vec::new();
+    if args.cold_native {
+        paths.push(DoshPath::ColdNative);
+    }
+    if args.cached_ticket {
+        paths.push(DoshPath::CachedTicket);
+    }
+    if args.resume {
+        paths.push(DoshPath::Resume);
+    }
+    paths
+}
+
+/// The single path implied by legacy flags when no explicit path is requested.
+fn legacy_dosh_path(args: &Args) -> DoshPath {
+    if args.local_auth {
+        DoshPath::LocalAuth
+    } else if args.warm_cache {
+        DoshPath::CachedTicket
+    } else {
+        DoshPath::SshBootstrap
+    }
 }
 
-    if !ssh_times.is_empty() {
-        println!(
-            "ssh_true_ms avg={:.2} samples={:?}",
-            avg_ms(&ssh_times),
-            ssh_times
-        );
-    }
-    println!(
-        "{dosh_label} avg={:.2} samples={:?}",
-        avg_ms(&dosh_times),
-        dosh_times
-    );
-    if !mosh_times.is_empty() {
-        println!(
-            "mosh_start_true_ms avg={:.2} samples={:?}",
-            avg_ms(&mosh_times),
-            mosh_times
-        );
-    }
-    if let Some(margin) = args.assert_ssh_plus_ms {
-        if ssh_times.is_empty() {
-            return Err(anyhow!(
-                "--assert-ssh-plus-ms requires non-local SSH benchmark"
-            ));
-        }
-        let ssh_avg = avg_ms(&ssh_times);
-        let dosh_avg = avg_ms(&dosh_times);
-        if dosh_avg > ssh_avg + margin {
-            return Err(anyhow!(
-                "dosh attach avg {dosh_avg:.2}ms exceeded ssh avg {ssh_avg:.2}ms + {margin:.2}ms"
-            ));
-        }
-        println!("gate ok: dosh avg {dosh_avg:.2}ms <= ssh avg {ssh_avg:.2}ms + {margin:.2}ms");
-    }
-    if let Some(margin) = args.assert_mosh_minus_ms {
-        if mosh_times.is_empty() {
-            return Err(anyhow!(
-                "--assert-mosh-minus-ms requires --include-mosh benchmark"
-            ));
-        }
-        let dosh_avg = avg_ms(&dosh_times);
-        let mosh_avg = avg_ms(&mosh_times);
-        if dosh_avg + margin > mosh_avg {
-            return Err(anyhow!(
-                "dosh attach avg {dosh_avg:.2}ms was not at least {margin:.2}ms faster than mosh avg {mosh_avg:.2}ms"
-            ));
-        }
-        println!("gate ok: dosh avg {dosh_avg:.2}ms + {margin:.2}ms <= mosh avg {mosh_avg:.2}ms");
-    }
-    if let Some(max_ms) = args.assert_dosh_max_ms {
-        let dosh_avg = avg_ms(&dosh_times);
-        if dosh_avg > max_ms {
-            return Err(anyhow!(
-                "{dosh_label} avg {dosh_avg:.2}ms exceeded max {max_ms:.2}ms"
-            ));
-        }
-        println!("gate ok: {dosh_label} avg {dosh_avg:.2}ms <= {max_ms:.2}ms");
-    }
-    Ok(())
+/// True when none of the selected paths needs an SSH baseline comparison
+/// (i.e. all are local-auth or cache fast paths driven without SSH).
+fn dosh_only(paths: &[DoshPath]) -> bool {
+    paths.iter().all(|p| {
+        matches!(
+            p,
+            DoshPath::LocalAuth | DoshPath::CachedTicket | DoshPath::Resume
+        )
+    })
 }
 
 fn time_dosh_attach(
     client: &PathBuf,
     args: &Args,
+    path: DoshPath,
     control_path: Option<&PathBuf>,
+    warm: bool,
 ) -> Result<Duration> {
     let mut cmd = Command::new(client);
     cmd.arg("--attach-only")
@@ -178,16 +253,55 @@ fn time_dosh_attach(
     if let Some(host) = &args.dosh_host {
         cmd.arg("--dosh-host").arg(host);
     }
+
+    match path {
+        DoshPath::LocalAuth => {
+            cmd.arg("--local-auth");
+            // While warming, write the cache; measured runs honor --no-cache.
+            if args.no_cache && !warm {
+                cmd.arg("--no-cache");
+            }
+            cmd.arg(&args.server);
+        }
+        DoshPath::CachedTicket | DoshPath::Resume => {
+            // Fast paths must read the warmed cache, so never pass --no-cache here.
+            // Whether the cache uses tickets vs resume is decided by the client
+            // config (`cache_attach_tickets`) the harness wrote into HOME.
             if args.local_auth {
-        cmd.arg("--local-auth").arg(&args.server);
-    } else {
+                cmd.arg("--local-auth");
+            }
+            add_bootstrap_args(&mut cmd, args, control_path);
+            cmd.arg(&args.server);
+        }
+        DoshPath::ColdNative => {
+            cmd.arg("--auth").arg("native");
+            // Cold path: never use a warmed cache.
+            cmd.arg("--no-cache");
+            add_bootstrap_args(&mut cmd, args, control_path);
+            cmd.arg(&args.server);
+        }
+        DoshPath::SshBootstrap => {
+            add_bootstrap_args(&mut cmd, args, control_path);
+            // Cold SSH bootstrap honors --no-cache on measured runs.
+            if args.no_cache && !warm {
+                cmd.arg("--no-cache");
+            }
+            cmd.arg(&args.server);
+        }
+    }
+    time_command(&mut cmd)
+}
+
+/// Append the SSH bootstrap arguments shared by the non-local paths. Native
+/// auth reuses the same SSH key/known-hosts/port plumbing.
+fn add_bootstrap_args(cmd: &mut Command, args: &Args, control_path: Option<&PathBuf>) {
+    if args.local_auth {
+        return;
+    }
     cmd.arg("--ssh-port")
         .arg(args.ssh_port.to_string())
         .arg("--ssh-auth-command")
         .arg(&args.ssh_auth_command);
-        if args.no_cache {
-            cmd.arg("--no-cache");
-        }
     if let Some(key) = &args.ssh_key {
         cmd.arg("--ssh-key").arg(key);
     }
@@ -197,9 +311,6 @@ fn time_dosh_attach(
     if let Some(control_path) = control_path {
         cmd.arg("--ssh-control-path").arg(control_path);
     }
-        cmd.arg(&args.server);
-    }
-    time_command(&mut cmd)
 }
 
 fn add_ssh_options(cmd: &mut Command, args: &Args, control_path: Option<&PathBuf>) {
@@ -381,9 +492,245 @@ fn time_command(cmd: &mut Command) -> Result<Duration> {
     Ok(start.elapsed())
 }
 
-fn avg_ms(samples: &[Duration]) -> f64 {
-    let total: f64 = samples.iter().map(|d| d.as_secs_f64() * 1000.0).sum();
-    total / samples.len() as f64
+/// Per-metric samples with summary statistics.
+struct MetricSamples {
+    name: &'static str,
+    samples: Vec<Duration>,
+}
+
+impl MetricSamples {
+    fn new(name: &'static str, samples: Vec<Duration>) -> Self {
+        Self { name, samples }
+    }
+
+    fn ms(&self) -> Vec<f64> {
+        self.samples
+            .iter()
+            .map(|d| d.as_secs_f64() * 1000.0)
+            .collect()
+    }
+
+    fn stats(&self) -> Stats {
+        Stats::from_ms(&self.ms())
+    }
+}
+
+/// Summary statistics for a set of millisecond samples.
+struct Stats {
+    count: usize,
+    min: f64,
+    median: f64,
+    p95: f64,
+    mean: f64,
+    max: f64,
+}
+
+impl Stats {
+    fn from_ms(values: &[f64]) -> Self {
+        if values.is_empty() {
+            return Self {
+                count: 0,
+                min: 0.0,
+                median: 0.0,
+                p95: 0.0,
+                mean: 0.0,
+                max: 0.0,
+            };
+        }
+        let mut sorted = values.to_vec();
+        sorted.sort_by(|a, b| a.partial_cmp(b).unwrap_or(std::cmp::Ordering::Equal));
+        let count = sorted.len();
+        let mean = sorted.iter().sum::<f64>() / count as f64;
+        Self {
+            count,
+            min: sorted[0],
+            median: percentile(&sorted, 50.0),
+            p95: percentile(&sorted, 95.0),
+            mean,
+            max: sorted[count - 1],
+        }
+    }
+}
+
+/// Linear-interpolated percentile over a pre-sorted slice.
+fn percentile(sorted: &[f64], pct: f64) -> f64 {
+    if sorted.is_empty() {
+        return 0.0;
+    }
+    if sorted.len() == 1 {
+        return sorted[0];
+    }
+    let rank = (pct / 100.0) * (sorted.len() - 1) as f64;
+    let lo = rank.floor() as usize;
+    let hi = rank.ceil() as usize;
+    if lo == hi {
+        sorted[lo]
+    } else {
+        let frac = rank - lo as f64;
+        sorted[lo] + (sorted[hi] - sorted[lo]) * frac
+    }
+}
+
+fn render_table(args: &Args, results: &[MetricSamples]) -> String {
+    let mut out = String::new();
+    if let Some(label) = &args.label {
+        let _ = writeln!(out, "# label: {label}");
+    }
+    let _ = writeln!(
+        out,
+        "{:<24} {:>6} {:>9} {:>9} {:>9} {:>9} {:>9}",
+        "metric", "n", "min", "median", "p95", "mean", "max"
+    );
+    for metric in results {
+        let s = metric.stats();
+        let _ = writeln!(
+            out,
+            "{:<24} {:>6} {:>9.2} {:>9.2} {:>9.2} {:>9.2} {:>9.2}",
+            metric.name, s.count, s.min, s.median, s.p95, s.mean, s.max
+        );
+    }
+    // Raw per-iteration samples, so published numbers can include raw data.
+    for metric in results {
+        let ms: Vec<String> = metric.ms().iter().map(|v| format!("{v:.2}")).collect();
+        let _ = writeln!(out, "{} samples_ms=[{}]", metric.name, ms.join(", "));
+    }
+    out
+}
+
+fn render_json(args: &Args, results: &[MetricSamples]) -> String {
+    let mut entries = Vec::new();
+    for metric in results {
+        let s = metric.stats();
+        let samples: Vec<String> = metric.ms().iter().map(|v| format!("{v:.4}")).collect();
+        entries.push(format!(
+            "{{\"metric\":\"{}\",\"count\":{},\"min\":{:.4},\"median\":{:.4},\"p95\":{:.4},\"mean\":{:.4},\"max\":{:.4},\"samples_ms\":[{}]}}",
+            metric.name,
+            s.count,
+            s.min,
+            s.median,
+            s.p95,
+            s.mean,
+            s.max,
+            samples.join(",")
+        ));
+    }
+    let label = match &args.label {
+        Some(label) => format!("\"{}\"", label.replace('"', "\\\"")),
+        None => "null".to_string(),
+    };
+    format!(
+        "{{\"label\":{label},\"iterations\":{},\"metrics\":[{}]}}",
+        args.iterations.max(1),
+        entries.join(",")
+    )
+}
+
+fn render_markdown(args: &Args, results: &[MetricSamples]) -> String {
+    let mut out = String::new();
+    let label = args.label.as_deref().unwrap_or("Dosh benchmark");
+    let _ = writeln!(out, "# {label}\n");
+    let _ = writeln!(out, "- server: `{}`", args.server);
+    let _ = writeln!(out, "- iterations: `{}`", args.iterations.max(1));
+    let _ = writeln!(
+        out,
+        "- generated_by: `dosh-bench {}`\n",
+        env!("CARGO_PKG_VERSION")
+    );
+    let _ = writeln!(
+        out,
+        "| metric | n | min ms | median ms | p95 ms | mean ms | max ms |"
+    );
+    let _ = writeln!(out, "|---|---:|---:|---:|---:|---:|---:|");
+    for metric in results {
+        let s = metric.stats();
+        let _ = writeln!(
+            out,
+            "| `{}` | {} | {:.2} | {:.2} | {:.2} | {:.2} | {:.2} |",
+            metric.name, s.count, s.min, s.median, s.p95, s.mean, s.max
+        );
+    }
+    let _ = writeln!(out, "\n## Raw Samples\n");
+    for metric in results {
+        let ms: Vec<String> = metric.ms().iter().map(|v| format!("{v:.2}")).collect();
+        let _ = writeln!(out, "- `{}`: [{}]", metric.name, ms.join(", "));
+    }
+    out
+}
+
+fn write_report(args: &Args, report: &str) -> Result<()> {
+    if let Some(path) = &args.output {
+        if let Some(parent) = path.parent()
+            && !parent.as_os_str().is_empty()
+        {
+            fs::create_dir_all(parent).with_context(|| format!("create {}", parent.display()))?;
+        }
+        fs::write(path, report).with_context(|| format!("write {}", path.display()))?;
+        println!("wrote {}", path.display());
+    } else {
+        println!("{report}");
+    }
+    Ok(())
+}
+
+fn metric_mean(results: &[MetricSamples], name: &str) -> Option<f64> {
+    results
+        .iter()
+        .find(|m| m.name == name)
+        .map(|m| m.stats().mean)
+}
+
+/// The headline dosh metric for assertions: prefer cached, then resume, then
+/// cold native, then ssh-bootstrap, then local-auth.
+fn primary_dosh(results: &[MetricSamples]) -> Option<(&'static str, f64)> {
+    const ORDER: [&str; 5] = [
+        "dosh_cached_attach_ms",
+        "dosh_resume_ms",
+        "dosh_cold_native_ms",
+        "dosh_attach_ms",
+        "dosh_local_attach_ms",
+    ];
+    for name in ORDER {
+        if let Some(mean) = metric_mean(results, name) {
+            return Some((name, mean));
+        }
+    }
+    None
+}
+
+fn run_assertions(args: &Args, results: &[MetricSamples]) -> Result<()> {
+    if let Some(margin) = args.assert_ssh_plus_ms {
+        let ssh = metric_mean(results, "ssh_true_ms")
+            .ok_or_else(|| anyhow!("--assert-ssh-plus-ms requires non-local SSH benchmark"))?;
+        let (name, dosh) =
+            primary_dosh(results).ok_or_else(|| anyhow!("no dosh metric to assert against"))?;
+        if dosh > ssh + margin {
+            return Err(anyhow!(
+                "{name} avg {dosh:.2}ms exceeded ssh avg {ssh:.2}ms + {margin:.2}ms"
+            ));
+        }
+        println!("gate ok: {name} avg {dosh:.2}ms <= ssh avg {ssh:.2}ms + {margin:.2}ms");
+    }
+    if let Some(margin) = args.assert_mosh_minus_ms {
+        let mosh = metric_mean(results, "mosh_start_true_ms")
+            .ok_or_else(|| anyhow!("--assert-mosh-minus-ms requires --include-mosh benchmark"))?;
+        let (name, dosh) =
+            primary_dosh(results).ok_or_else(|| anyhow!("no dosh metric to assert against"))?;
+        if dosh + margin > mosh {
+            return Err(anyhow!(
+                "{name} avg {dosh:.2}ms was not at least {margin:.2}ms faster than mosh avg {mosh:.2}ms"
+            ));
+        }
+        println!("gate ok: {name} avg {dosh:.2}ms + {margin:.2}ms <= mosh avg {mosh:.2}ms");
+    }
+    if let Some(max_ms) = args.assert_dosh_max_ms {
+        let (name, dosh) =
+            primary_dosh(results).ok_or_else(|| anyhow!("no dosh metric to assert against"))?;
+        if dosh > max_ms {
+            return Err(anyhow!("{name} avg {dosh:.2}ms exceeded max {max_ms:.2}ms"));
+        }
+        println!("gate ok: {name} avg {dosh:.2}ms <= {max_ms:.2}ms");
+    }
+    Ok(())
 }
 
 fn default_client_path() -> PathBuf {
@@ -392,3 +739,69 @@ fn default_client_path() -> PathBuf {
         .and_then(|path| path.parent().map(|parent| parent.join("dosh-client")))
         .unwrap_or_else(|| PathBuf::from("dosh-client"))
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn args_for_render() -> Args {
+        Args {
+            server: "local".to_string(),
+            session: "default".to_string(),
+            ssh_port: 22,
+            dosh_port: 50000,
+            dosh_host: None,
+            iterations: 2,
+            local_auth: true,
+            cold_native: false,
+            cached_ticket: false,
+            resume: false,
+            client: None,
+            ssh_auth_command: "~/.local/bin/dosh-auth".to_string(),
+            ssh_key: None,
+            ssh_known_hosts: None,
+            ssh_control_path: None,
+            controlmaster: false,
+            no_cache: false,
+            warm_cache: false,
+            skip_ssh_baseline: true,
+            include_mosh: false,
+            mosh: PathBuf::from("mosh"),
+            mosh_server_command: "mosh-server".to_string(),
+            mosh_port: None,
+            json: false,
+            markdown: true,
+            output: None,
+            label: Some("test host".to_string()),
+            assert_ssh_plus_ms: None,
+            assert_mosh_minus_ms: None,
+            assert_dosh_max_ms: None,
+        }
+    }
+
+    #[test]
+    fn markdown_report_contains_summary_and_samples() {
+        let args = args_for_render();
+        let metrics = vec![MetricSamples::new(
+            "dosh_cached_attach_ms",
+            vec![Duration::from_millis(3), Duration::from_millis(5)],
+        )];
+        let report = render_markdown(&args, &metrics);
+        assert!(report.contains("# test host"));
+        assert!(report.contains("| `dosh_cached_attach_ms` | 2 | 3.00"));
+        assert!(report.contains("- `dosh_cached_attach_ms`: [3.00, 5.00]"));
+    }
+
+    #[test]
+    fn json_report_contains_metrics() {
+        let args = args_for_render();
+        let metrics = vec![MetricSamples::new(
+            "dosh_local_attach_ms",
+            vec![Duration::from_millis(7)],
+        )];
+        let report = render_json(&args, &metrics);
+        assert!(report.contains("\"label\":\"test host\""));
+        assert!(report.contains("\"metric\":\"dosh_local_attach_ms\""));
+        assert!(report.contains("\"samples_ms\":[7.0000]"));
+    }
+}

src/config.rs

@@ -28,6 +28,14 @@ pub struct ServerConfig {
     pub authorized_keys: Vec<String>,
     #[serde(default = "default_native_auth_rate_limit_per_minute")]
     pub native_auth_rate_limit_per_minute: u32,
+    /// Rotate a client's transport traffic key after this many packets in the
+    /// current epoch (spec §11). `0` disables the packet-count trigger.
+    #[serde(default = "default_rekey_after_packets")]
+    pub rekey_after_packets: u64,
+    /// Rotate a client's transport traffic key after this many wall-clock seconds
+    /// in the current epoch (spec §11). `0` disables the time trigger.
+    #[serde(default = "default_rekey_after_secs")]
+    pub rekey_after_secs: u64,
     #[serde(default = "default_true")]
     pub allow_tcp_forwarding: bool,
     #[serde(default)]
@@ -38,6 +46,17 @@ pub struct ServerConfig {
     pub allow_agent_forwarding: bool,
     #[serde(default = "default_accept_env")]
     pub accept_env: Vec<String>,
+    /// Run each terminal session's shell under a small per-session *holder*
+    /// process so it survives a `dosh-server` restart (crash/upgrade/
+    /// `systemctl restart`). On startup the server re-adopts live holders and
+    /// reattaching clients land on the same shell with screen state intact. When
+    /// `false`, sessions behave exactly as before: the shell is a child of the
+    /// server and dies with it.
+    // Opt-in for now: this changes the core session model (per-session holder
+    // processes + fd passing), so it stays OFF by default until it has been
+    // stress-tested on a real host. Set `persist_sessions = true` to enable.
+    #[serde(default)]
+    pub persist_sessions: bool,
 }
 
 impl Default for ServerConfig {
@@ -61,11 +80,14 @@ impl Default for ServerConfig {
             host_key: default_host_key(),
             authorized_keys: default_authorized_keys(),
             native_auth_rate_limit_per_minute: default_native_auth_rate_limit_per_minute(),
+            rekey_after_packets: default_rekey_after_packets(),
+            rekey_after_secs: default_rekey_after_secs(),
             allow_tcp_forwarding: true,
             allow_remote_forwarding: false,
             allow_remote_non_loopback_bind: false,
             allow_agent_forwarding: false,
             accept_env: default_accept_env(),
+            persist_sessions: false,
         }
     }
 }
@@ -82,8 +104,12 @@ pub struct ClientConfig {
     pub default_session: String,
     pub reconnect_timeout_secs: u64,
     pub view_only: bool,
-    #[serde(default)]
+    #[serde(default = "default_true")]
     pub predict: bool,
+    /// Prediction display policy: "off", "experimental" (adaptive, the default),
+    /// or "always". Controls when speculative local echo is shown.
+    #[serde(default = "default_predict_mode")]
+    pub predict_mode: String,
     pub cache_attach_tickets: bool,
     pub credential_cache: String,
     #[serde(default = "default_auth_preference")]
@@ -100,10 +126,21 @@ pub struct ClientConfig {
     pub use_ssh_agent: bool,
     #[serde(default)]
     pub forward_agent: bool,
+    /// Show a non-destructive, mosh-style status line on the bottom screen row
+    /// when UDP packets stop arriving ("[dosh] last contact Ns ago …"). Drawn
+    /// with save/restore cursor so it never moves the app cursor or corrupts a
+    /// full-screen TUI, and cleared the instant packets resume. Default on.
+    #[serde(default = "default_true")]
+    pub disconnect_status: bool,
     #[serde(default = "default_send_env")]
     pub send_env: Vec<String>,
     #[serde(default)]
     pub set_env: HashMap<String, String>,
+    /// Optional client-side command extensions. These are just shell command
+    /// templates expanded into the remote session's startup input; Dosh does not
+    /// depend on the tools they name.
+    #[serde(default)]
+    pub extensions: HashMap<String, CommandExtension>,
 }
 
 #[derive(Debug, Clone, Default, Serialize, Deserialize)]
@@ -119,6 +156,22 @@ pub struct HostConfig {
     pub send_env: Option<Vec<String>>,
     #[serde(default)]
     pub set_env: HashMap<String, String>,
+    /// Per-host extension overrides. A host can replace a global extension or set
+    /// `disabled = true` to opt out of it.
+    #[serde(default)]
+    pub extensions: HashMap<String, CommandExtension>,
+}
+
+#[derive(Debug, Clone, Default, Serialize, Deserialize, PartialEq, Eq)]
+pub struct CommandExtension {
+    /// Remote shell command template. `{args}` expands to shell-quoted extra
+    /// words after the extension name. When absent, extra args are appended.
+    #[serde(default)]
+    pub command: Option<String>,
+    #[serde(default)]
+    pub description: Option<String>,
+    #[serde(default)]
+    pub disabled: bool,
 }
 
 #[derive(Debug, Clone, Default, Serialize, Deserialize)]
@@ -140,7 +193,8 @@ impl Default for ClientConfig {
             default_session: "new".to_string(),
             reconnect_timeout_secs: 5,
             view_only: false,
-            predict: false,
+            predict: true,
+            predict_mode: default_predict_mode(),
             cache_attach_tickets: true,
             credential_cache: "~/.local/share/dosh/credentials".to_string(),
             auth_preference: default_auth_preference(),
@@ -150,8 +204,10 @@ impl Default for ClientConfig {
             identity_files: default_identity_files(),
             use_ssh_agent: true,
             forward_agent: false,
+            disconnect_status: true,
             send_env: default_send_env(),
             set_env: HashMap::new(),
+            extensions: HashMap::new(),
         }
     }
 }
@@ -175,6 +231,18 @@ fn default_native_auth_rate_limit_per_minute() -> u32 {
     30
 }
 
+fn default_rekey_after_packets() -> u64 {
+    // Rotate well before any AEAD nonce-reuse concern; ChaCha20-Poly1305 with a
+    // per-direction monotonic seq is safe far beyond this, but a bounded epoch
+    // keeps forward-secrecy windows small.
+    100_000
+}
+
+fn default_rekey_after_secs() -> u64 {
+    // One hour per epoch by default.
+    3600
+}
+
 fn default_auth_preference() -> String {
     "native,ssh".to_string()
 }
@@ -183,6 +251,10 @@ fn default_native_auth_timeout_ms() -> u64 {
     700
 }
 
+fn default_predict_mode() -> String {
+    "experimental".to_string()
+}
+
 fn default_known_hosts() -> String {
     "~/.config/dosh/known_hosts".to_string()
 }

src/lib.rs

@@ -2,6 +2,7 @@ pub mod auth;
 pub mod config;
 pub mod crypto;
 pub mod native;
+pub mod persist;
 pub mod protocol;
 pub mod pty;
 pub mod ssh_agent;

src/native.rs

@@ -5,7 +5,9 @@ use anyhow::{Context, Result, bail};
 use base64::Engine;
 use base64::engine::general_purpose::{STANDARD, URL_SAFE_NO_PAD};
 use ed25519_dalek::{Signature, Signer, SigningKey, Verifier, VerifyingKey};
+use rsa::traits::PublicKeyParts;
 use serde::{Deserialize, Serialize};
+use signature::{SignatureEncoding, Signer as SignatureSigner, Verifier as SignatureVerifier};
 use std::fs;
 use std::io::Write;
 use std::net::IpAddr;
@@ -15,7 +17,7 @@ use std::str::FromStr;
 use x25519_dalek::{PublicKey as X25519PublicKey, StaticSecret};
 
 pub const HOST_KEY_ALGORITHM: &str = "dosh-ed25519";
-pub const NATIVE_PROTOCOL_VERSION: u8 = 1;
+pub const NATIVE_PROTOCOL_VERSION: u8 = 2;
 
 #[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
 pub struct HostPublicKey {
@@ -91,6 +93,12 @@ pub enum ForwardingKind {
     Local,
     Remote,
     Dynamic,
+    /// SSH-agent forwarding: the client opts in and, if the server policy allows
+    /// (`allow_agent_forwarding`), the server exports a proxy unix socket as
+    /// `SSH_AUTH_SOCK` in the remote session and tunnels each connection back to
+    /// the client's local agent over a Dosh stream. Added at the end of the enum
+    /// so bincode discriminants for the existing variants are unchanged.
+    Agent,
 }
 
 #[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
@@ -248,17 +256,55 @@ pub fn sign_server_hello(
     Ok(())
 }
 
+/// Error raised when a native handshake peer speaks a different protocol version.
+///
+/// Carries the peer's advertised version so callers can render an actionable,
+/// named message ("upgrade dosh") rather than letting a mismatch surface as an
+/// opaque decrypt failure or a silent timeout. The `Display` text deliberately
+/// embeds [`crate::protocol::VERSION_MISMATCH_REASON`] so the server's reject and
+/// the client's local error read the same way.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct ProtocolVersionMismatch {
+    pub local: u8,
+    pub remote: u8,
+    pub peer: &'static str,
+}
+
+impl std::fmt::Display for ProtocolVersionMismatch {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(
+            f,
+            "{} ({} speaks native protocol v{}, this build speaks v{})",
+            crate::protocol::VERSION_MISMATCH_REASON,
+            self.peer,
+            self.remote,
+            self.local,
+        )
+    }
+}
+
+impl std::error::Error for ProtocolVersionMismatch {}
+
+/// Verify a peer-advertised native protocol version against this build.
+///
+/// `peer` names whose version was wrong ("client" or "server") for the error
+/// message. Returns a typed [`ProtocolVersionMismatch`] so the caller can both
+/// match on it and print an actionable, upgrade-oriented message.
+pub fn check_native_protocol_version(version: u8, peer: &'static str) -> Result<()> {
+    if version != NATIVE_PROTOCOL_VERSION {
+        return Err(ProtocolVersionMismatch {
+            local: NATIVE_PROTOCOL_VERSION,
+            remote: version,
+            peer,
+        }
+        .into());
+    }
+    Ok(())
+}
+
 pub fn verify_server_hello(client: &NativeClientHello, server: &NativeServerHello) -> Result<()> {
-    anyhow::ensure!(
-        client.protocol_version == NATIVE_PROTOCOL_VERSION,
-        "unsupported native client protocol {}",
-        client.protocol_version
-    );
-    anyhow::ensure!(
-        server.protocol_version == NATIVE_PROTOCOL_VERSION,
-        "unsupported native server protocol {}",
-        server.protocol_version
-    );
+    check_native_protocol_version(client.protocol_version, "client")?;
+    check_native_protocol_version(server.protocol_version, "server")?;
     let transcript = server_hello_transcript(client, server)?;
     verify_host_signature(&server.host_key, &transcript, &server.host_signature)
 }
@@ -295,6 +341,92 @@ pub fn sign_user_auth(
     Ok(auth)
 }
 
+pub fn sign_user_auth_with_private_key(
+    private_key: &ssh_key::PrivateKey,
+    client: &NativeClientHello,
+    server: &NativeServerHello,
+    requested_forwardings: Vec<ForwardingRequest>,
+) -> Result<NativeUserAuth> {
+    anyhow::ensure!(!private_key.is_encrypted(), "OpenSSH identity is encrypted");
+    let public_key = private_key.public_key();
+    let key_algorithm = public_key.algorithm().as_str().to_string();
+    anyhow::ensure!(
+        is_supported_user_key_algorithm(&key_algorithm),
+        "unsupported native identity key algorithm {key_algorithm}"
+    );
+    let public_key_blob = ssh_public_blob_from_public_key(public_key)?;
+    let public_key_for_auth = if key_algorithm == "ssh-ed25519" {
+        parse_ssh_ed25519_public_blob(&public_key_blob)?.to_vec()
+    } else {
+        public_key_blob
+    };
+    let signature_algorithm = signature_algorithm_for_private_key(&key_algorithm)?;
+    let mut auth = NativeUserAuth {
+        public_key_algorithm: signature_algorithm.to_string(),
+        public_key: public_key_for_auth,
+        signature: Vec::new(),
+        requested_forwardings,
+    };
+    let transcript = user_auth_transcript(client, server, &auth)?;
+    auth.signature = if key_algorithm == "ssh-rsa" {
+        sign_rsa_sha512_private_key(private_key, &transcript)?
+    } else {
+        let signature = SignatureSigner::try_sign(private_key, &transcript)
+            .context("sign native user auth with OpenSSH private key")?;
+        anyhow::ensure!(
+            signature.algorithm().as_str() == auth.public_key_algorithm,
+            "private key produced signature algorithm {}, expected {}",
+            signature.algorithm().as_str(),
+            auth.public_key_algorithm
+        );
+        signature.as_bytes().to_vec()
+    };
+    Ok(auth)
+}
+
+fn sign_rsa_sha512_private_key(
+    private_key: &ssh_key::PrivateKey,
+    transcript: &[u8],
+) -> Result<Vec<u8>> {
+    let rsa_keypair = private_key
+        .key_data()
+        .rsa()
+        .ok_or_else(|| anyhow::anyhow!("OpenSSH identity is not ssh-rsa"))?;
+    let rsa_private = rsa_private_key_from_ssh_keypair(rsa_keypair)?;
+    let signing_key = rsa::pkcs1v15::SigningKey::<sha2::Sha512>::new(rsa_private);
+    let signature: rsa::pkcs1v15::Signature = SignatureSigner::sign(&signing_key, transcript);
+    Ok(signature.to_vec())
+}
+
+fn rsa_private_key_from_ssh_keypair(
+    keypair: &ssh_key::private::RsaKeypair,
+) -> Result<rsa::RsaPrivateKey> {
+    let private = rsa::RsaPrivateKey::from_components(
+        rsa::BigUint::try_from(&keypair.public.n).context("convert RSA modulus")?,
+        rsa::BigUint::try_from(&keypair.public.e).context("convert RSA public exponent")?,
+        rsa::BigUint::try_from(&keypair.private.d).context("convert RSA private exponent")?,
+        vec![
+            rsa::BigUint::try_from(&keypair.private.p).context("convert RSA p prime")?,
+            rsa::BigUint::try_from(&keypair.private.q).context("convert RSA q prime")?,
+        ],
+    )
+    .context("convert OpenSSH RSA private key")?;
+    anyhow::ensure!(
+        private.size().saturating_mul(8) >= 2048,
+        "OpenSSH RSA identity is smaller than 2048 bits"
+    );
+    Ok(private)
+}
+
+fn signature_algorithm_for_private_key(key_algorithm: &str) -> Result<&'static str> {
+    match key_algorithm {
+        "ssh-ed25519" => Ok("ssh-ed25519"),
+        "ecdsa-sha2-nistp256" => Ok("ecdsa-sha2-nistp256"),
+        "ssh-rsa" => Ok("rsa-sha2-512"),
+        _ => bail!("unsupported native identity key algorithm {key_algorithm}"),
+    }
+}
+
 pub fn verify_native_user_auth(
     client: &NativeClientHello,
     server: &NativeServerHello,
@@ -303,10 +435,54 @@ pub fn verify_native_user_auth(
     source_ip: Option<IpAddr>,
 ) -> Result<AuthorizedKey> {
     anyhow::ensure!(
-        auth.public_key_algorithm == "ssh-ed25519",
+        is_supported_user_signature_algorithm(&auth.public_key_algorithm),
         "unsupported native user key algorithm {}",
         auth.public_key_algorithm
     );
+    let authorized_algorithm = authorized_key_algorithm_for_auth(&auth.public_key_algorithm)?;
+    let authorized = authorized_keys
+        .iter()
+        .find(|key| key.algorithm == authorized_algorithm && key.key == auth.public_key)
+        .ok_or_else(|| anyhow::anyhow!("native user key is not authorized"))?;
+    authorized.ensure_native_allowed(auth, source_ip)?;
+
+    let transcript = user_auth_transcript(client, server, auth)?;
+    verify_native_user_signature(auth, &transcript)?;
+    Ok(authorized.clone())
+}
+
+pub fn supported_user_key_algorithms() -> Vec<String> {
+    vec![
+        "ssh-ed25519".to_string(),
+        "ecdsa-sha2-nistp256".to_string(),
+        "rsa-sha2-512".to_string(),
+        "rsa-sha2-256".to_string(),
+    ]
+}
+
+pub fn is_supported_user_key_algorithm(algorithm: &str) -> bool {
+    matches!(algorithm, "ssh-ed25519" | "ecdsa-sha2-nistp256" | "ssh-rsa")
+}
+
+pub fn is_supported_user_signature_algorithm(algorithm: &str) -> bool {
+    matches!(
+        algorithm,
+        "ssh-ed25519" | "ecdsa-sha2-nistp256" | "rsa-sha2-512" | "rsa-sha2-256"
+    )
+}
+
+fn authorized_key_algorithm_for_auth(signature_algorithm: &str) -> Result<&'static str> {
+    match signature_algorithm {
+        "ssh-ed25519" => Ok("ssh-ed25519"),
+        "ecdsa-sha2-nistp256" => Ok("ecdsa-sha2-nistp256"),
+        "rsa-sha2-512" | "rsa-sha2-256" => Ok("ssh-rsa"),
+        _ => bail!("unsupported native user key algorithm {signature_algorithm}"),
+    }
+}
+
+fn verify_native_user_signature(auth: &NativeUserAuth, transcript: &[u8]) -> Result<()> {
+    match auth.public_key_algorithm.as_str() {
+        "ssh-ed25519" => {
             anyhow::ensure!(
                 auth.public_key.len() == 32,
                 "ssh-ed25519 public key must be 32 bytes"
@@ -315,23 +491,69 @@ pub fn verify_native_user_auth(
                 auth.signature.len() == 64,
                 "ssh-ed25519 signature must be 64 bytes"
             );
-    let authorized = authorized_keys
-        .iter()
-        .find(|key| key.algorithm == "ssh-ed25519" && key.key == auth.public_key)
-        .ok_or_else(|| anyhow::anyhow!("native user key is not authorized"))?;
-    authorized.ensure_native_allowed(auth, source_ip)?;
-
             let mut public_key = [0u8; 32];
             public_key.copy_from_slice(&auth.public_key);
-    let verifying_key = VerifyingKey::from_bytes(&public_key).context("parse user public key")?;
+            let verifying_key =
+                VerifyingKey::from_bytes(&public_key).context("parse user public key")?;
             let mut signature = [0u8; 64];
             signature.copy_from_slice(&auth.signature);
             let signature = Signature::from_bytes(&signature);
-    let transcript = user_auth_transcript(client, server, auth)?;
             verifying_key
-        .verify(&transcript, &signature)
+                .verify(transcript, &signature)
                 .context("verify native user signature")?;
-    Ok(authorized.clone())
+        }
+        "ecdsa-sha2-nistp256" => {
+            let public_key = ssh_public_key_from_blob(&auth.public_key)
+                .context("parse native user SSH public key")?;
+            let algorithm =
+                ssh_key::Algorithm::from_str(&auth.public_key_algorithm).with_context(|| {
+                    format!("parse signature algorithm {}", auth.public_key_algorithm)
+                })?;
+            let signature = ssh_key::Signature::new(algorithm, auth.signature.clone())
+                .context("parse native user SSH signature")?;
+            SignatureVerifier::verify(public_key.key_data(), transcript, &signature)
+                .context("verify native user SSH signature")?;
+        }
+        "rsa-sha2-512" | "rsa-sha2-256" => {
+            verify_rsa_sha2_signature(
+                &auth.public_key,
+                &auth.public_key_algorithm,
+                transcript,
+                &auth.signature,
+            )?;
+        }
+        algorithm => bail!("unsupported native user key algorithm {algorithm}"),
+    }
+    Ok(())
+}
+
+fn verify_rsa_sha2_signature(
+    public_key_blob: &[u8],
+    signature_algorithm: &str,
+    transcript: &[u8],
+    signature: &[u8],
+) -> Result<()> {
+    let (e, n) = parse_ssh_rsa_public_blob(public_key_blob)?;
+    let public = rsa::RsaPublicKey::new(
+        rsa::BigUint::from_bytes_be(n),
+        rsa::BigUint::from_bytes_be(e),
+    )
+    .context("parse RSA public key")?;
+    let signature =
+        rsa::pkcs1v15::Signature::try_from(signature).context("parse RSA PKCS#1v1.5 signature")?;
+    match signature_algorithm {
+        "rsa-sha2-256" => {
+            let key = rsa::pkcs1v15::VerifyingKey::<sha2::Sha256>::new(public);
+            SignatureVerifier::verify(&key, transcript, &signature)
+                .context("verify RSA-SHA256 signature")
+        }
+        "rsa-sha2-512" => {
+            let key = rsa::pkcs1v15::VerifyingKey::<sha2::Sha512>::new(public);
+            SignatureVerifier::verify(&key, transcript, &signature)
+                .context("verify RSA-SHA512 signature")
+        }
+        _ => bail!("legacy ssh-rsa/SHA-1 signatures are not accepted"),
+    }
 }
 
 pub fn verify_native_user_auth_from_config(
@@ -369,6 +591,36 @@ pub fn derive_native_session_key(
     crypto::hkdf32(shared.as_bytes(), &salt, b"dosh/native/chacha20poly1305/v1")
 }
 
+/// Derive a rotated transport key for transport rekey (spec §11 / §9).
+///
+/// The rotated key is derived **independently of the handshake traffic keys**:
+/// the input keying material is the current epoch's key (which both peers already
+/// hold) mixed with fresh, server-generated `rekey_material` (32 bytes of CSPRNG
+/// output, delivered confidentially inside an AEAD `Rekey` packet sealed under
+/// the current key). The new `epoch` and the previous epoch's `session_key_id`
+/// salt the derivation so each epoch's key is unique. It never re-derives from
+/// the handshake DH output, satisfying the spec requirement that "rotated session
+/// keys must be derived independently ... from fresh randomness" and "must not
+/// reuse handshake traffic keys."
+///
+/// Both peers run this identically — the client never needs the server's
+/// long-term secret, only the fresh `rekey_material` it receives in the `Rekey`
+/// packet plus the current key it already shares.
+pub fn derive_rekey_session_key(
+    current_key: &[u8; 32],
+    rekey_material: &[u8; 32],
+    previous_session_key_id: &[u8; 16],
+    epoch: u64,
+) -> Result<[u8; 32]> {
+    let mut ikm = Vec::with_capacity(64);
+    ikm.extend_from_slice(current_key);
+    ikm.extend_from_slice(rekey_material);
+    let mut salt = b"dosh/native/rekey/v1".to_vec();
+    salt.extend_from_slice(previous_session_key_id);
+    salt.extend_from_slice(&epoch.to_be_bytes());
+    crypto::hkdf32(&ikm, &salt, b"dosh/native/rekey/chacha20poly1305/v1")
+}
+
 pub fn load_ed25519_identity(path: &Path) -> Result<SigningKey> {
     load_ed25519_identity_with_passphrase(path, None)
 }
@@ -396,6 +648,35 @@ pub fn load_ed25519_identity_with_passphrase(
         .with_context(|| format!("parse ssh-ed25519 identity {}", path.display()))
 }
 
+pub fn load_native_identity(path: &Path) -> Result<ssh_key::PrivateKey> {
+    load_native_identity_with_passphrase(path, None)
+}
+
+pub fn load_native_identity_with_passphrase(
+    path: &Path,
+    passphrase: Option<&str>,
+) -> Result<ssh_key::PrivateKey> {
+    let raw = fs::read_to_string(path).with_context(|| format!("read {}", path.display()))?;
+    let private_key = ssh_key::PrivateKey::from_openssh(&raw)
+        .with_context(|| format!("parse OpenSSH identity {}", path.display()))?;
+    let private_key = if private_key.is_encrypted() {
+        let passphrase = passphrase
+            .ok_or_else(|| anyhow::anyhow!("OpenSSH identity {} is encrypted", path.display()))?;
+        private_key
+            .decrypt(passphrase)
+            .with_context(|| format!("decrypt OpenSSH identity {}", path.display()))?
+    } else {
+        private_key
+    };
+    let algorithm = private_key.public_key().algorithm().as_str().to_string();
+    anyhow::ensure!(
+        is_supported_user_key_algorithm(&algorithm),
+        "OpenSSH identity {} has unsupported native key algorithm {algorithm}",
+        path.display()
+    );
+    Ok(private_key)
+}
+
 impl AuthorizedKey {
     fn ensure_native_allowed(
         &self,
@@ -445,6 +726,10 @@ impl AuthorizedKey {
                             "authorized key permitopen= cannot authorize remote or dynamic forwarding"
                         );
                     }
+                    // Agent forwarding does not open a host:port, so permitopen
+                    // (which restricts which targets may be opened) does not apply;
+                    // it is gated separately by the server's allow_agent_forwarding.
+                    ForwardingKind::Agent => {}
                 }
             }
         }
@@ -487,7 +772,7 @@ fn parse_authorized_key_line(line_number: usize, line: &str) -> Result<Authorize
         fields.len() >= 2,
         "authorized_keys:{line_number}: expected key fields"
     );
-    let (options, key_type_index) = if fields[0].starts_with("ssh-") {
+    let (options, key_type_index) = if is_supported_user_key_algorithm(&fields[0]) {
         (AuthorizedKeyOptions::default(), 0)
     } else {
         (parse_authorized_key_options(&fields[0])?, 1)
@@ -498,15 +783,20 @@ fn parse_authorized_key_line(line_number: usize, line: &str) -> Result<Authorize
     let key_blob = fields
         .get(key_type_index + 1)
         .with_context(|| format!("authorized_keys:{line_number}: missing key blob"))?;
-    anyhow::ensure!(
-        algorithm == "ssh-ed25519",
-        "authorized_keys:{line_number}: unsupported key type {algorithm}"
-    );
     let decoded = STANDARD
         .decode(key_blob)
         .with_context(|| format!("authorized_keys:{line_number}: decode key blob"))?;
-    let key = parse_ssh_ed25519_public_blob(&decoded)
-        .with_context(|| format!("authorized_keys:{line_number}: parse ssh-ed25519 key"))?;
+    anyhow::ensure!(
+        is_supported_user_key_algorithm(algorithm),
+        "authorized_keys:{line_number}: unsupported key type {algorithm}"
+    );
+    validate_supported_public_key_blob(algorithm, &decoded)
+        .with_context(|| format!("authorized_keys:{line_number}: parse {algorithm} key"))?;
+    let key = if algorithm == "ssh-ed25519" {
+        parse_ssh_ed25519_public_blob(&decoded)?.to_vec()
+    } else {
+        decoded
+    };
     let comment = if fields.len() > key_type_index + 2 {
         Some(fields[key_type_index + 2..].join(" "))
     } else {
@@ -520,6 +810,51 @@ fn parse_authorized_key_line(line_number: usize, line: &str) -> Result<Authorize
     })
 }
 
+fn validate_supported_public_key_blob(algorithm: &str, blob: &[u8]) -> Result<()> {
+    let blob_algorithm = ssh_public_key_blob_algorithm(blob)?;
+    anyhow::ensure!(
+        blob_algorithm == algorithm,
+        "key blob type {blob_algorithm} does not match authorized_keys type {algorithm}"
+    );
+    match algorithm {
+        "ssh-ed25519" => {
+            parse_ssh_ed25519_public_blob(blob)?;
+        }
+        "ecdsa-sha2-nistp256" | "ssh-rsa" => {
+            let _ = ssh_public_key_from_blob(blob)?;
+        }
+        _ => bail!("unsupported key type {algorithm}"),
+    }
+    Ok(())
+}
+
+fn ssh_public_key_blob_algorithm(blob: &[u8]) -> Result<String> {
+    let mut cursor = blob;
+    let algorithm = read_ssh_string(&mut cursor)?;
+    Ok(String::from_utf8_lossy(algorithm).to_string())
+}
+
+fn ssh_public_key_from_blob(blob: &[u8]) -> Result<ssh_key::PublicKey> {
+    let algorithm = ssh_public_key_blob_algorithm(blob)?;
+    let encoded = STANDARD.encode(blob);
+    ssh_key::PublicKey::from_openssh(&format!("{algorithm} {encoded}"))
+        .with_context(|| format!("parse OpenSSH public key blob {algorithm}"))
+}
+
+fn ssh_public_blob_from_public_key(public_key: &ssh_key::PublicKey) -> Result<Vec<u8>> {
+    let line = public_key
+        .to_openssh()
+        .context("encode OpenSSH public key")?;
+    let mut fields = line.split_whitespace();
+    let _algorithm = fields
+        .next()
+        .context("encoded public key missing algorithm")?;
+    let encoded = fields.next().context("encoded public key missing blob")?;
+    STANDARD
+        .decode(encoded)
+        .context("decode encoded OpenSSH public key blob")
+}
+
 fn split_authorized_key_fields(line: &str) -> Vec<String> {
     line.split_whitespace().map(ToString::to_string).collect()
 }
@@ -687,6 +1022,18 @@ pub fn parse_ssh_ed25519_public_blob(blob: &[u8]) -> Result<[u8; 32]> {
     Ok(out)
 }
 
+fn parse_ssh_rsa_public_blob(blob: &[u8]) -> Result<(&[u8], &[u8])> {
+    let mut cursor = blob;
+    let key_type = read_ssh_string(&mut cursor)?;
+    anyhow::ensure!(key_type == b"ssh-rsa", "key blob type mismatch");
+    let e = read_ssh_mpint(&mut cursor)?;
+    let n = read_ssh_mpint(&mut cursor)?;
+    anyhow::ensure!(cursor.is_empty(), "trailing data in ssh-rsa key blob");
+    anyhow::ensure!(!e.is_empty(), "ssh-rsa exponent is empty");
+    anyhow::ensure!(!n.is_empty(), "ssh-rsa modulus is empty");
+    Ok((e, n))
+}
+
 pub fn ssh_ed25519_public_blob(public_key: &[u8; 32]) -> Vec<u8> {
     let mut out = Vec::new();
     write_ssh_string(&mut out, b"ssh-ed25519");
@@ -694,6 +1041,12 @@ pub fn ssh_ed25519_public_blob(public_key: &[u8; 32]) -> Vec<u8> {
     out
 }
 
+fn read_ssh_mpint<'a>(cursor: &mut &'a [u8]) -> Result<&'a [u8]> {
+    let raw = read_ssh_string(cursor)?;
+    let raw = raw.strip_prefix(&[0]).unwrap_or(raw);
+    Ok(raw)
+}
+
 fn read_ssh_string<'a>(cursor: &mut &'a [u8]) -> Result<&'a [u8]> {
     anyhow::ensure!(cursor.len() >= 4, "truncated SSH string length");
     let len = u32::from_be_bytes(cursor[..4].try_into().unwrap()) as usize;
@@ -926,16 +1279,16 @@ mod tests {
         let second = host_public_key(&SigningKey::from_bytes(&[2u8; 32]));
 
         assert_eq!(
-            trust_host(&path, "palav", &first, "ssh", false).unwrap(),
+            trust_host(&path, "homelab", &first, "ssh", false).unwrap(),
             TrustResult::Trusted
         );
         assert_eq!(
-            trust_host(&path, "palav", &first, "ssh", false).unwrap(),
+            trust_host(&path, "homelab", &first, "ssh", false).unwrap(),
             TrustResult::AlreadyTrusted
         );
-        assert!(trust_host(&path, "palav", &second, "ssh", false).is_err());
+        assert!(trust_host(&path, "homelab", &second, "ssh", false).is_err());
         assert_eq!(
-            trust_host(&path, "palav", &second, "ssh", true).unwrap(),
+            trust_host(&path, "homelab", &second, "ssh", true).unwrap(),
             TrustResult::Trusted
         );
     }
@@ -948,16 +1301,16 @@ mod tests {
         let second = host_public_key(&SigningKey::from_bytes(&[2u8; 32]));
 
         assert_eq!(
-            verify_known_host(&path, "palav", &first).unwrap(),
+            verify_known_host(&path, "homelab", &first).unwrap(),
             KnownHostStatus::Unknown
         );
-        trust_host(&path, "palav", &first, "ssh", false).unwrap();
+        trust_host(&path, "homelab", &first, "ssh", false).unwrap();
         assert_eq!(
-            verify_known_host(&path, "palav", &first).unwrap(),
+            verify_known_host(&path, "homelab", &first).unwrap(),
             KnownHostStatus::Trusted
         );
         assert!(matches!(
-            verify_known_host(&path, "palav", &second).unwrap(),
+            verify_known_host(&path, "homelab", &second).unwrap(),
             KnownHostStatus::Mismatch { .. }
         ));
     }
@@ -1006,6 +1359,45 @@ mod tests {
         assert!(verify_native_user_auth(&client, &server, &auth, &removed, None).is_err());
     }
 
+    #[test]
+    fn native_user_auth_accepts_ecdsa_p256_private_key() {
+        let mut rng = rand::rngs::OsRng;
+        let private = ssh_key::PrivateKey::random(
+            &mut rng,
+            ssh_key::Algorithm::Ecdsa {
+                curve: ssh_key::EcdsaCurve::NistP256,
+            },
+        )
+        .unwrap();
+        let host_signing = SigningKey::from_bytes(&[10u8; 32]);
+        let client = test_client_hello();
+        let mut server = test_server_hello(&host_signing);
+        sign_server_hello(&host_signing, &client, &mut server).unwrap();
+        let auth = sign_user_auth_with_private_key(&private, &client, &server, Vec::new()).unwrap();
+        let authorized =
+            parse_authorized_keys(&private.public_key().to_openssh().unwrap()).unwrap();
+
+        assert_eq!(auth.public_key_algorithm, "ecdsa-sha2-nistp256");
+        verify_native_user_auth(&client, &server, &auth, &authorized, None).unwrap();
+    }
+
+    #[test]
+    fn native_user_auth_accepts_rsa_sha2_private_key() {
+        let mut rng = rand::rngs::OsRng;
+        let private =
+            ssh_key::PrivateKey::random(&mut rng, ssh_key::Algorithm::Rsa { hash: None }).unwrap();
+        let host_signing = SigningKey::from_bytes(&[11u8; 32]);
+        let client = test_client_hello();
+        let mut server = test_server_hello(&host_signing);
+        sign_server_hello(&host_signing, &client, &mut server).unwrap();
+        let auth = sign_user_auth_with_private_key(&private, &client, &server, Vec::new()).unwrap();
+        let authorized =
+            parse_authorized_keys(&private.public_key().to_openssh().unwrap()).unwrap();
+
+        assert_eq!(auth.public_key_algorithm, "rsa-sha2-512");
+        verify_native_user_auth(&client, &server, &auth, &authorized, None).unwrap();
+    }
+
     #[test]
     fn native_user_auth_rejects_tampered_transcript() {
         let host_signing = SigningKey::from_bytes(&[3u8; 32]);
@@ -1233,8 +1625,8 @@ mod tests {
             protocol_version: NATIVE_PROTOCOL_VERSION,
             client_random: [1u8; 32],
             client_ephemeral_public: [2u8; 32],
-            requested_host: "palav".to_string(),
-            requested_user: "palav".to_string(),
+            requested_host: "homelab".to_string(),
+            requested_user: "alice".to_string(),
             requested_session: "term".to_string(),
             requested_mode: "read-write".to_string(),
             terminal_size: (80, 24),

src/persist.rs

@@ -0,0 +1,658 @@
+//! Session persistence across server restarts.
+//!
+//! A persistent dosh session's shell does not run as a child of `dosh-server`.
+//! Instead the server spawns a tiny per-session *holder* process (the same
+//! `dosh-server` binary re-exec'd as `dosh-server hold ...`). The holder calls
+//! `setsid()` to leave the server's process group/session, opens a PTY, spawns
+//! the shell as ITS own child, and listens on a Unix socket in a per-session
+//! runtime directory. The server connects to that socket and the holder hands it
+//! the PTY master fd over `SCM_RIGHTS`.
+//!
+//! Because the shell belongs to the holder (which is in its own session and is
+//! not waited on by the server), killing or restarting `dosh-server` leaves the
+//! holder + shell alive. On startup the server scans the runtime directory,
+//! reconnects to each live holder, receives the master fd again, and rebuilds the
+//! in-memory session so clients reattach to the very same shell.
+//!
+//! Screen / scrollback state lives only in server memory, so it is also mirrored
+//! to disk (atomically) and restored on re-adoption, letting a reattaching client
+//! repaint the screen exactly as it was before the restart.
+
+use anyhow::{Context, Result, anyhow, bail};
+use std::io::{Read, Write};
+use std::os::fd::{AsRawFd, FromRawFd, IntoRawFd, RawFd};
+use std::os::unix::net::{UnixListener, UnixStream};
+use std::path::{Path, PathBuf};
+use std::time::Duration;
+
+/// One-byte commands a server sends to a holder over its control socket after
+/// the holder has handed back the master fd.
+const HOLDER_CMD_SHUTDOWN: u8 = b'X';
+
+/// Magic written into a holder's `meta` file, bumped if the on-disk layout
+/// changes so a stale holder from an incompatible build is ignored.
+const META_MAGIC: &str = "dosh-holder-1";
+
+/// Per-session runtime metadata persisted next to the holder socket.
+#[derive(Debug, Clone)]
+pub struct HolderMeta {
+    pub session: String,
+    pub shell_pid: i32,
+}
+
+/// Root runtime directory holding one subdirectory per persistent session.
+/// Lives under `sessions_dir/run` so it shares the session storage location and
+/// can be wiped with it.
+pub fn runtime_root(sessions_dir: &Path) -> PathBuf {
+    sessions_dir.join("run")
+}
+
+/// Map a session name to a filesystem-safe directory name. Session names are
+/// user-controlled, so hex-encode them rather than trusting them as path
+/// components (avoids traversal, slashes, NULs, length issues).
+fn session_dir_name(session: &str) -> String {
+    let mut out = String::with_capacity(session.len() * 2);
+    for byte in session.as_bytes() {
+        out.push(char::from_digit((byte >> 4) as u32, 16).unwrap());
+        out.push(char::from_digit((byte & 0xf) as u32, 16).unwrap());
+    }
+    out
+}
+
+fn decode_session_dir_name(name: &str) -> Option<String> {
+    if !name.len().is_multiple_of(2) {
+        return None;
+    }
+    let mut bytes = Vec::with_capacity(name.len() / 2);
+    let raw = name.as_bytes();
+    let mut i = 0;
+    while i < raw.len() {
+        let hi = (raw[i] as char).to_digit(16)?;
+        let lo = (raw[i + 1] as char).to_digit(16)?;
+        bytes.push(((hi << 4) | lo) as u8);
+        i += 2;
+    }
+    String::from_utf8(bytes).ok()
+}
+
+/// Directory for one session's holder runtime state.
+pub fn session_runtime_dir(sessions_dir: &Path, session: &str) -> PathBuf {
+    runtime_root(sessions_dir).join(session_dir_name(session))
+}
+
+fn holder_sock_path(dir: &Path) -> PathBuf {
+    dir.join("holder.sock")
+}
+
+fn meta_path(dir: &Path) -> PathBuf {
+    dir.join("meta")
+}
+
+fn screen_path(dir: &Path) -> PathBuf {
+    dir.join("screen")
+}
+
+/// Create the runtime directory tree with private (0700) permissions.
+pub fn ensure_runtime_dir(sessions_dir: &Path, session: &str) -> Result<PathBuf> {
+    use std::os::unix::fs::PermissionsExt;
+    let root = runtime_root(sessions_dir);
+    std::fs::create_dir_all(&root).with_context(|| format!("create {}", root.display()))?;
+    let _ = std::fs::set_permissions(&root, std::fs::Permissions::from_mode(0o700));
+    let dir = session_runtime_dir(sessions_dir, session);
+    std::fs::create_dir_all(&dir).with_context(|| format!("create {}", dir.display()))?;
+    std::fs::set_permissions(&dir, std::fs::Permissions::from_mode(0o700))
+        .with_context(|| format!("chmod {}", dir.display()))?;
+    Ok(dir)
+}
+
+/// Atomically write `data` to `path` (write temp + rename), so a concurrent
+/// reader (e.g. a restarting server) never sees a half-written file.
+fn atomic_write(path: &Path, data: &[u8]) -> Result<()> {
+    use std::os::unix::fs::PermissionsExt;
+    let tmp = path.with_extension("tmp");
+    {
+        let mut file =
+            std::fs::File::create(&tmp).with_context(|| format!("create {}", tmp.display()))?;
+        let _ = file.set_permissions(std::fs::Permissions::from_mode(0o600));
+        file.write_all(data)
+            .with_context(|| format!("write {}", tmp.display()))?;
+        file.sync_all().ok();
+    }
+    std::fs::rename(&tmp, path)
+        .with_context(|| format!("rename {} -> {}", tmp.display(), path.display()))?;
+    Ok(())
+}
+
+/// Persist the vt100 screen snapshot plus recent raw output for a session so a
+/// post-restart reattach repaints correctly. `snapshot` is the bytes a fresh
+/// attach would receive (alt-screen toggle + `state_formatted`).
+pub fn save_screen(
+    sessions_dir: &Path,
+    session: &str,
+    cols: u16,
+    rows: u16,
+    output_seq: u64,
+    snapshot: &[u8],
+) -> Result<()> {
+    let dir = session_runtime_dir(sessions_dir, session);
+    if !dir.exists() {
+        // No holder runtime for this session (non-persistent): nothing to do.
+        return Ok(());
+    }
+    let mut buf = Vec::with_capacity(snapshot.len() + 32);
+    buf.extend_from_slice(&cols.to_be_bytes());
+    buf.extend_from_slice(&rows.to_be_bytes());
+    buf.extend_from_slice(&output_seq.to_be_bytes());
+    buf.extend_from_slice(&(snapshot.len() as u32).to_be_bytes());
+    buf.extend_from_slice(snapshot);
+    atomic_write(&screen_path(&dir), &buf)
+}
+
+/// A restored screen for a re-adopted session.
+pub struct SavedScreen {
+    pub cols: u16,
+    pub rows: u16,
+    pub output_seq: u64,
+    pub snapshot: Vec<u8>,
+}
+
+/// Load a previously persisted screen, if any.
+pub fn load_screen(sessions_dir: &Path, session: &str) -> Option<SavedScreen> {
+    let dir = session_runtime_dir(sessions_dir, session);
+    let data = std::fs::read(screen_path(&dir)).ok()?;
+    if data.len() < 16 {
+        return None;
+    }
+    let cols = u16::from_be_bytes(data[0..2].try_into().ok()?);
+    let rows = u16::from_be_bytes(data[2..4].try_into().ok()?);
+    let output_seq = u64::from_be_bytes(data[4..12].try_into().ok()?);
+    let len = u32::from_be_bytes(data[12..16].try_into().ok()?) as usize;
+    if data.len() < 16 + len {
+        return None;
+    }
+    Some(SavedScreen {
+        cols,
+        rows,
+        output_seq,
+        snapshot: data[16..16 + len].to_vec(),
+    })
+}
+
+fn write_meta(dir: &Path, meta: &HolderMeta) -> Result<()> {
+    let body = format!("{META_MAGIC}\n{}\n{}\n", meta.shell_pid, meta.session);
+    atomic_write(&meta_path(dir), body.as_bytes())
+}
+
+fn read_meta(dir: &Path) -> Option<HolderMeta> {
+    let body = std::fs::read_to_string(meta_path(dir)).ok()?;
+    let mut lines = body.lines();
+    if lines.next()? != META_MAGIC {
+        return None;
+    }
+    let shell_pid: i32 = lines.next()?.parse().ok()?;
+    let session = lines.next()?.to_string();
+    Some(HolderMeta { session, shell_pid })
+}
+
+/// Spawn a holder process for `session`: re-exec this binary as `dosh-server
+/// hold` with the runtime dir, shell, terminal size, and accepted env. The
+/// holder daemonizes (setsid, owns the PTY) and listens on its control socket.
+/// Returns once the holder has signalled readiness by creating its socket.
+#[allow(clippy::too_many_arguments)]
+pub fn spawn_holder(
+    sessions_dir: &Path,
+    session: &str,
+    shell: &str,
+    cols: u16,
+    rows: u16,
+    env: &[(String, String)],
+) -> Result<()> {
+    let dir = ensure_runtime_dir(sessions_dir, session)?;
+    let sock = holder_sock_path(&dir);
+    // Clear any stale socket left by a crashed holder with the same name.
+    let _ = std::fs::remove_file(&sock);
+
+    let exe = std::env::current_exe().context("locate current executable")?;
+    let mut cmd = std::process::Command::new(exe);
+    cmd.arg("hold")
+        .arg("--runtime-dir")
+        .arg(&dir)
+        .arg("--session")
+        .arg(session)
+        .arg("--shell")
+        .arg(shell)
+        .arg("--cols")
+        .arg(cols.to_string())
+        .arg("--rows")
+        .arg(rows.to_string());
+    for (name, value) in env {
+        cmd.arg("--env").arg(format!("{name}={value}"));
+    }
+    cmd.stdin(std::process::Stdio::null())
+        .stdout(std::process::Stdio::null())
+        .stderr(std::process::Stdio::null());
+    let mut child = cmd.spawn().context("spawn holder process")?;
+
+    // Wait (briefly) for the holder to come up. The holder forks/setsids before
+    // creating the socket; once the socket exists we can connect. We also reap
+    // the short-lived launcher child so it never becomes a zombie.
+    let deadline = std::time::Instant::now() + Duration::from_secs(5);
+    loop {
+        if sock.exists() {
+            break;
+        }
+        if std::time::Instant::now() >= deadline {
+            let _ = child.kill();
+            let _ = child.wait();
+            bail!("holder for session {session} did not come up in time");
+        }
+        std::thread::sleep(Duration::from_millis(20));
+    }
+    // The launcher exits immediately after the grandchild setsids; reap it.
+    let _ = child.wait();
+    Ok(())
+}
+
+/// Connect to a session's holder and receive the PTY master fd over SCM_RIGHTS.
+/// Returns the raw fd (caller owns it) and the holder control socket, kept open
+/// so the server can later ask the holder to shut down. Returns an error if the
+/// holder is gone (caller then degrades to a fresh, non-persistent session).
+pub fn adopt_holder(sessions_dir: &Path, session: &str) -> Result<(RawFd, UnixStream)> {
+    let dir = session_runtime_dir(sessions_dir, session);
+    let sock = holder_sock_path(&dir);
+    let mut stream = UnixStream::connect(&sock)
+        .with_context(|| format!("connect holder socket {}", sock.display()))?;
+    stream.set_read_timeout(Some(Duration::from_secs(5))).ok();
+    let fd = recv_fd(&mut stream).context("receive master fd from holder")?;
+    Ok((fd, stream))
+}
+
+/// Ask a holder to terminate its shell and exit, then clean its runtime dir.
+/// Used when reaping a truly-abandoned persistent session.
+pub fn request_shutdown(sessions_dir: &Path, session: &str, control: Option<&mut UnixStream>) {
+    if let Some(stream) = control {
+        let _ = stream.write_all(&[HOLDER_CMD_SHUTDOWN]);
+        let _ = stream.flush();
+    } else {
+        let dir = session_runtime_dir(sessions_dir, session);
+        if let Ok(mut stream) = UnixStream::connect(holder_sock_path(&dir)) {
+            // Drain the fd the holder sends on connect, then send shutdown.
+            let _ = recv_fd(&mut stream);
+            let _ = stream.write_all(&[HOLDER_CMD_SHUTDOWN]);
+            let _ = stream.flush();
+        }
+    }
+    // Give the holder a moment to tear down, then remove its runtime dir.
+    std::thread::sleep(Duration::from_millis(50));
+    let dir = session_runtime_dir(sessions_dir, session);
+    let _ = std::fs::remove_dir_all(&dir);
+}
+
+/// Remove a session's runtime directory unconditionally (best effort).
+pub fn remove_runtime_dir(sessions_dir: &Path, session: &str) {
+    let dir = session_runtime_dir(sessions_dir, session);
+    let _ = std::fs::remove_dir_all(&dir);
+}
+
+/// Scan the runtime root for holders left behind by a previous server. Returns
+/// `(session_name, meta)` for each one whose holder process still appears alive.
+/// Stale entries (no live process) are cleaned up.
+pub fn scan_existing_holders(sessions_dir: &Path) -> Vec<HolderMeta> {
+    let root = runtime_root(sessions_dir);
+    let mut found = Vec::new();
+    let Ok(entries) = std::fs::read_dir(&root) else {
+        return found;
+    };
+    for entry in entries.flatten() {
+        let dir = entry.path();
+        if !dir.is_dir() {
+            continue;
+        }
+        let Some(name) = dir.file_name().and_then(|n| n.to_str()) else {
+            continue;
+        };
+        // Decode the on-disk name back to a session name; skip junk dirs.
+        if decode_session_dir_name(name).is_none() {
+            continue;
+        }
+        match read_meta(&dir) {
+            Some(meta) if process_alive(meta.shell_pid) && holder_sock_path(&dir).exists() => {
+                found.push(meta);
+            }
+            _ => {
+                // Holder gone or meta unreadable: clean up so we don't try to
+                // adopt a dead session (degrade to fresh on next attach).
+                let _ = std::fs::remove_dir_all(&dir);
+            }
+        }
+    }
+    found
+}
+
+/// Whether a pid refers to a live process (signal 0 probe).
+fn process_alive(pid: i32) -> bool {
+    if pid <= 0 {
+        return false;
+    }
+    unsafe {
+        libc::kill(pid, 0) == 0
+            || std::io::Error::last_os_error().raw_os_error() == Some(libc::EPERM)
+    }
+}
+
+// ---------------------------------------------------------------------------
+// Holder process entry point
+// ---------------------------------------------------------------------------
+
+/// Run as a holder process. Daemonizes (double-fork + setsid), opens a PTY,
+/// spawns the shell as its own child, and serves the control socket: every
+/// accepted connection is handed the master fd (SCM_RIGHTS); a subsequent
+/// SHUTDOWN byte (or the shell exiting) tears everything down.
+///
+/// This function does not return on success — it `exit`s the process. Errors
+/// before the daemonization point are returned to the launcher.
+#[allow(clippy::too_many_arguments)]
+pub fn run_holder(
+    runtime_dir: &Path,
+    session: &str,
+    shell: &str,
+    cols: u16,
+    rows: u16,
+    env: &[(String, String)],
+) -> Result<()> {
+    use portable_pty::{NativePtySystem, PtySize, PtySystem};
+
+    // Detach from the launching server: own session + process group so a server
+    // exit (even a process-group kill of the service) does not take us down.
+    daemonize().context("daemonize holder")?;
+
+    let pty_system = NativePtySystem::default();
+    let pair = pty_system
+        .openpty(PtySize {
+            rows,
+            cols,
+            pixel_width: 0,
+            pixel_height: 0,
+        })
+        .context("holder open pty")?;
+    let cmd = crate::pty::build_shell_command(shell, env);
+    let mut child = pair
+        .slave
+        .spawn_command(cmd)
+        .context("holder spawn shell")?;
+    drop(pair.slave);
+    let master_fd = pair
+        .master
+        .as_raw_fd()
+        .ok_or_else(|| anyhow!("holder master has no raw fd"))?;
+    let shell_pid = child.process_id().map(|p| p as i32).unwrap_or(-1);
+
+    write_meta(
+        runtime_dir,
+        &HolderMeta {
+            session: session.to_string(),
+            shell_pid,
+        },
+    )?;
+
+    let sock = holder_sock_path(runtime_dir);
+    let _ = std::fs::remove_file(&sock);
+    let listener =
+        UnixListener::bind(&sock).with_context(|| format!("holder bind {}", sock.display()))?;
+    {
+        use std::os::unix::fs::PermissionsExt;
+        let _ = std::fs::set_permissions(&sock, std::fs::Permissions::from_mode(0o600));
+    }
+    listener
+        .set_nonblocking(false)
+        .context("holder listener blocking")?;
+
+    // A watcher thread reaps the shell: when it exits, the holder cleans up and
+    // exits too, so an abandoned shell does not linger forever.
+    let runtime_owned = runtime_dir.to_path_buf();
+    std::thread::spawn(move || {
+        let _ = child.wait();
+        // Shell exited: remove runtime dir and exit the holder process.
+        let _ = std::fs::remove_dir_all(&runtime_owned);
+        std::process::exit(0);
+    });
+
+    // Accept loop: each connecting server gets the master fd; a SHUTDOWN byte
+    // from any of them tears the holder down. Multiple servers never run at once
+    // in practice (one service), but serving repeated connections lets a server
+    // restart re-adopt cleanly.
+    for stream in listener.incoming() {
+        let Ok(mut stream) = stream else { continue };
+        if send_fd(&mut stream, master_fd).is_err() {
+            continue;
+        }
+        // Wait for an optional command byte. EOF (server dropped the control
+        // socket on its own exit) just means "keep running, await re-adoption".
+        let mut cmd = [0u8; 1];
+        match stream.read(&mut cmd) {
+            Ok(1) if cmd[0] == HOLDER_CMD_SHUTDOWN => {
+                let _ = std::fs::remove_dir_all(runtime_dir);
+                std::process::exit(0);
+            }
+            _ => {
+                // Server detached (exit/restart) or sent nothing actionable:
+                // loop back and wait for the next server to re-adopt us.
+            }
+        }
+    }
+    Ok(())
+}
+
+/// Double-fork + `setsid` so the holder runs in its own session, detached from
+/// the server's controlling terminal and process group. Without this a
+/// `systemctl restart` (which signals the whole service cgroup/process group)
+/// could take the holder down with the server.
+fn daemonize() -> Result<()> {
+    // First fork: parent (launcher) returns to reap; child continues.
+    match unsafe { libc::fork() } {
+        -1 => bail!("fork: {}", std::io::Error::last_os_error()),
+        0 => {}
+        _ => {
+            // Parent process: exit so the launcher's wait() returns promptly and
+            // the grandchild is reparented to init.
+            std::process::exit(0);
+        }
+    }
+    // New session: detaches from controlling tty and the server's process group.
+    if unsafe { libc::setsid() } == -1 {
+        bail!("setsid: {}", std::io::Error::last_os_error());
+    }
+    // Second fork: ensures we are not a session leader, so we can never
+    // re-acquire a controlling terminal.
+    match unsafe { libc::fork() } {
+        -1 => bail!("fork2: {}", std::io::Error::last_os_error()),
+        0 => Ok(()),
+        _ => std::process::exit(0),
+    }
+}
+
+// ---------------------------------------------------------------------------
+// SCM_RIGHTS file-descriptor passing over a Unix domain socket
+// ---------------------------------------------------------------------------
+
+/// Send a single fd over `stream` using SCM_RIGHTS, with one byte of normal data
+/// (sendmsg requires at least one iovec byte for the ancillary data to ride on).
+fn send_fd(stream: &mut UnixStream, fd: RawFd) -> Result<()> {
+    let dummy: [u8; 1] = [0];
+    let mut iov = libc::iovec {
+        iov_base: dummy.as_ptr() as *mut libc::c_void,
+        iov_len: 1,
+    };
+    let mut cmsg_buf = [0u8; cmsg_space_one_fd()];
+    let mut msg: libc::msghdr = unsafe { std::mem::zeroed() };
+    msg.msg_iov = &mut iov;
+    msg.msg_iovlen = 1;
+    msg.msg_control = cmsg_buf.as_mut_ptr() as *mut libc::c_void;
+    msg.msg_controllen = cmsg_buf.len() as _;
+
+    unsafe {
+        let cmsg = libc::CMSG_FIRSTHDR(&msg);
+        if cmsg.is_null() {
+            bail!("CMSG_FIRSTHDR null");
+        }
+        (*cmsg).cmsg_level = libc::SOL_SOCKET;
+        (*cmsg).cmsg_type = libc::SCM_RIGHTS;
+        (*cmsg).cmsg_len = libc::CMSG_LEN(std::mem::size_of::<RawFd>() as u32) as _;
+        std::ptr::copy_nonoverlapping(
+            &fd as *const RawFd as *const u8,
+            libc::CMSG_DATA(cmsg),
+            std::mem::size_of::<RawFd>(),
+        );
+        let n = libc::sendmsg(stream.as_raw_fd(), &msg, 0);
+        if n < 0 {
+            return Err(std::io::Error::last_os_error()).context("sendmsg SCM_RIGHTS");
+        }
+    }
+    Ok(())
+}
+
+/// Receive a single fd sent via SCM_RIGHTS. Returns a fresh fd owned by the
+/// caller.
+fn recv_fd(stream: &mut UnixStream) -> Result<RawFd> {
+    let mut dummy = [0u8; 1];
+    let mut iov = libc::iovec {
+        iov_base: dummy.as_mut_ptr() as *mut libc::c_void,
+        iov_len: 1,
+    };
+    let mut cmsg_buf = [0u8; cmsg_space_one_fd()];
+    let mut msg: libc::msghdr = unsafe { std::mem::zeroed() };
+    msg.msg_iov = &mut iov;
+    msg.msg_iovlen = 1;
+    msg.msg_control = cmsg_buf.as_mut_ptr() as *mut libc::c_void;
+    msg.msg_controllen = cmsg_buf.len() as _;
+
+    unsafe {
+        let n = libc::recvmsg(stream.as_raw_fd(), &mut msg, 0);
+        if n < 0 {
+            return Err(std::io::Error::last_os_error()).context("recvmsg SCM_RIGHTS");
+        }
+        if n == 0 {
+            bail!("holder closed connection before sending fd");
+        }
+        let cmsg = libc::CMSG_FIRSTHDR(&msg);
+        if cmsg.is_null() {
+            bail!("no ancillary data (fd) received from holder");
+        }
+        if (*cmsg).cmsg_level != libc::SOL_SOCKET || (*cmsg).cmsg_type != libc::SCM_RIGHTS {
+            bail!("unexpected ancillary message from holder");
+        }
+        let mut fd: RawFd = -1;
+        std::ptr::copy_nonoverlapping(
+            libc::CMSG_DATA(cmsg),
+            &mut fd as *mut RawFd as *mut u8,
+            std::mem::size_of::<RawFd>(),
+        );
+        if fd < 0 {
+            bail!("invalid fd received from holder");
+        }
+        Ok(fd)
+    }
+}
+
+/// Space, in bytes, needed for a control-message buffer carrying exactly one fd.
+const fn cmsg_space_one_fd() -> usize {
+    // CMSG_SPACE is not const in libc; this is the equivalent for one RawFd.
+    // cmsghdr is aligned to size_of::<usize>(); add data length rounded up.
+    let data = std::mem::size_of::<RawFd>();
+    let hdr = std::mem::size_of::<libc::cmsghdr>();
+    let align = std::mem::size_of::<usize>();
+    // round(hdr) + round(data)
+    ((hdr + align - 1) & !(align - 1)) + ((data + align - 1) & !(align - 1))
+}
+
+/// Helper used by `adopt_holder` callers to turn the received raw fd into an
+/// owned `File`-like object if they need RAII (the server hands it to
+/// `pty::adopt_pty_from_fd`, which takes ownership of the raw fd).
+pub fn fd_into_file(fd: RawFd) -> std::fs::File {
+    unsafe { std::fs::File::from_raw_fd(fd) }
+}
+
+/// Convert a `File` back into a raw fd it no longer owns (so it can be handed to
+/// `adopt_pty_from_fd`). Currently unused outside tests but kept symmetric.
+pub fn file_into_fd(file: std::fs::File) -> RawFd {
+    file.into_raw_fd()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn session_dir_name_round_trips() {
+        for name in ["default", "work", "a/b/../c", "weird name", "日本語"] {
+            let encoded = session_dir_name(name);
+            assert!(encoded.bytes().all(|b| b.is_ascii_hexdigit()));
+            assert_eq!(decode_session_dir_name(&encoded).as_deref(), Some(name));
+        }
+    }
+
+    #[test]
+    fn decode_rejects_non_hex() {
+        assert!(decode_session_dir_name("zz").is_none());
+        assert!(decode_session_dir_name("abc").is_none());
+    }
+
+    #[test]
+    fn save_and_load_screen_round_trips() {
+        let tmp = tempfile::tempdir().unwrap();
+        let sessions_dir = tmp.path();
+        ensure_runtime_dir(sessions_dir, "work").unwrap();
+        let snap = b"\x1b[?1049lhello world".to_vec();
+        save_screen(sessions_dir, "work", 100, 40, 7, &snap).unwrap();
+        let loaded = load_screen(sessions_dir, "work").expect("screen restored");
+        assert_eq!(loaded.cols, 100);
+        assert_eq!(loaded.rows, 40);
+        assert_eq!(loaded.output_seq, 7);
+        assert_eq!(loaded.snapshot, snap);
+    }
+
+    #[test]
+    fn load_screen_absent_is_none() {
+        let tmp = tempfile::tempdir().unwrap();
+        assert!(load_screen(tmp.path(), "missing").is_none());
+    }
+
+    #[test]
+    fn scan_skips_dead_and_junk_entries() {
+        let tmp = tempfile::tempdir().unwrap();
+        let sessions_dir = tmp.path();
+        // A meta pointing at a definitely-dead pid is cleaned up, not returned.
+        let dir = ensure_runtime_dir(sessions_dir, "ghost").unwrap();
+        write_meta(
+            &dir,
+            &HolderMeta {
+                session: "ghost".to_string(),
+                shell_pid: 2_000_000_000, // not a live pid
+            },
+        )
+        .unwrap();
+        // A junk (non-hex) directory is ignored.
+        std::fs::create_dir_all(runtime_root(sessions_dir).join("not-hex")).unwrap();
+        let found = scan_existing_holders(sessions_dir);
+        assert!(found.is_empty(), "dead/junk holders must be skipped");
+        assert!(!dir.exists(), "dead holder dir should be cleaned up");
+    }
+
+    #[test]
+    fn send_and_recv_fd_round_trips() {
+        use std::io::Seek;
+        // Pass a temp file's fd across a socketpair and confirm both ends point
+        // at the same open file (write via one, read via the other).
+        let (mut a, mut b) = UnixStream::pair().unwrap();
+        let mut file = tempfile::tempfile().unwrap();
+        writeln!(file, "shared-fd-marker").unwrap();
+        file.flush().unwrap();
+        send_fd(&mut a, file.as_raw_fd()).unwrap();
+        let received = recv_fd(&mut b).unwrap();
+        let mut got = fd_into_file(received);
+        got.rewind().unwrap();
+        let mut contents = String::new();
+        got.read_to_string(&mut contents).unwrap();
+        assert!(contents.contains("shared-fd-marker"));
+    }
+}

src/protocol.rs

@@ -3,10 +3,56 @@ use crate::crypto;
 use crate::native::{EnvVar, NativeAuthOk, NativeClientHello, NativeServerHello, NativeUserAuth};
 use anyhow::{Context, Result, bail};
 use serde::{Deserialize, Serialize};
+use std::time::{SystemTime, UNIX_EPOCH};
+
+/// Generate a name for an implicit, ephemeral terminal session — the kind
+/// created by `dosh host` with no `--session`. Single source of truth shared by
+/// the client (which generates it) and the server (which recognizes it via
+/// [`is_implicit_session_name`] to decide a session is NOT worth persisting).
+pub fn generate_implicit_session_name() -> String {
+    let millis = SystemTime::now()
+        .duration_since(UNIX_EPOCH)
+        .unwrap_or_default()
+        .as_millis();
+    format!("term-{millis}-{}", std::process::id())
+}
+
+/// Whether `name` is a client-generated implicit session name
+/// (`term-<digits>-<digits>`). Such sessions are ephemeral: the user can never
+/// reattach by name, so the server must not persist them across restarts.
+/// Explicitly-named (`--session work`) and prewarmed sessions are not implicit.
+pub fn is_implicit_session_name(name: &str) -> bool {
+    let Some(rest) = name.strip_prefix("term-") else {
+        return false;
+    };
+    let mut parts = rest.split('-');
+    match (parts.next(), parts.next(), parts.next()) {
+        (Some(millis), Some(pid), None) => {
+            !millis.is_empty()
+                && millis.bytes().all(|b| b.is_ascii_digit())
+                && !pid.is_empty()
+                && pid.bytes().all(|b| b.is_ascii_digit())
+        }
+        _ => false,
+    }
+}
 
 pub const MAGIC: &[u8; 4] = b"DOSH";
-pub const VERSION: u8 = 1;
+// v4: added reliable stream offsets/acks to `StreamData` and
+// `StreamWindowAdjust`.
+// v3: added `ForwardingKind::Agent` (SSH-agent forwarding). The new variant rides
+// inside `NativeUserAuth.requested_forwardings`, so a pre-agent peer would fail to
+// deserialize it; bumping the wire version makes such a peer answer with a clear
+// version-mismatch reject instead. Existing variants' bincode discriminants are
+// unchanged, so the bump is purely a compatibility gate.
+pub const VERSION: u8 = 4;
 pub const HEADER_LEN: usize = 58;
+
+/// Stable, user-facing reason string the server puts in an `AttachReject` when a
+/// native handshake arrives carrying a `protocol_version` it cannot speak. The
+/// client recognizes this prefix and surfaces a clear "upgrade dosh" message
+/// instead of the generic transport rejection or, worse, a silent timeout.
+pub const VERSION_MISMATCH_REASON: &str = "protocol version mismatch — upgrade dosh";
 const HEADER_AAD_LEN: usize = HEADER_LEN - 2;
 pub const CLIENT_TO_SERVER: u32 = 1;
 pub const SERVER_TO_CLIENT: u32 = 2;
@@ -39,6 +85,8 @@ pub enum PacketKind {
     StreamEof = 23,
     StreamClose = 24,
     NativeAuthCheckOk = 25,
+    Rekey = 26,
+    RekeyAck = 27,
 }
 
 impl TryFrom<u8> for PacketKind {
@@ -71,6 +119,8 @@ impl TryFrom<u8> for PacketKind {
             23 => Self::StreamEof,
             24 => Self::StreamClose,
             25 => Self::NativeAuthCheckOk,
+            26 => Self::Rekey,
+            27 => Self::RekeyAck,
             _ => bail!("unknown packet kind {value}"),
         })
     }
@@ -110,7 +160,11 @@ impl Header {
             bail!("bad magic");
         }
         if input[4] != VERSION {
-            bail!("bad protocol version {}", input[4]);
+            bail!(
+                "{} (peer wire protocol v{}, this build speaks v{VERSION})",
+                VERSION_MISMATCH_REASON,
+                input[4]
+            );
         }
         let kind = PacketKind::try_from(input[5])?;
         let flags = u16::from_be_bytes(input[6..8].try_into().unwrap());
@@ -133,6 +187,20 @@ impl Header {
     }
 }
 
+/// Cheaply inspect a datagram that carries our [`MAGIC`] but whose wire
+/// [`VERSION`] byte differs from this build's. Returns the peer's advertised
+/// wire version when (and only when) the packet is a Dosh packet we cannot
+/// otherwise decode because of a version skew, so the receiver can answer with a
+/// clear, named version-mismatch reject instead of dropping it (a silent
+/// timeout for the peer). Returns `None` for our own version, foreign magic, or
+/// runt packets.
+pub fn peek_foreign_wire_version(input: &[u8]) -> Option<u8> {
+    if input.len() < 5 || &input[..4] != MAGIC || input[4] == VERSION {
+        return None;
+    }
+    Some(input[4])
+}
+
 #[derive(Debug, Clone)]
 pub struct Packet {
     pub header: Header,
@@ -350,12 +418,14 @@ pub struct StreamOpenReject {
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct StreamData {
     pub stream_id: u64,
+    pub offset: u64,
     pub bytes: Vec<u8>,
 }
 
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct StreamWindowAdjust {
     pub stream_id: u64,
+    pub received_offset: u64,
     pub bytes: u32,
 }
 
@@ -369,6 +439,20 @@ pub struct StreamClose {
     pub stream_id: u64,
 }
 
+/// Server→client transport rekey, sealed under the *current* session key.
+///
+/// Carries the fresh server-generated `rekey_material` and the new `epoch`; both
+/// peers feed these into [`crate::native::derive_rekey_session_key`] to compute
+/// the next traffic key. `new_session_key_id` is the id the next epoch's packets
+/// will carry, so the client can recognize and switch atomically. The client
+/// replies with a [`PacketKind::RekeyAck`] encrypted under the *new* key.
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct Rekey {
+    pub epoch: u64,
+    pub rekey_material: [u8; 32],
+    pub new_session_key_id: [u8; 16],
+}
+
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct Frame {
     pub session: String,
@@ -449,3 +533,41 @@ impl ReplayWindow {
         }
     }
 }
+
+#[cfg(test)]
+mod session_name_tests {
+    use super::{generate_implicit_session_name, is_implicit_session_name};
+
+    #[test]
+    fn generated_names_are_recognized_as_implicit() {
+        let name = generate_implicit_session_name();
+        assert!(is_implicit_session_name(&name), "generated: {name}");
+    }
+
+    #[test]
+    fn explicit_and_prewarm_names_are_not_implicit() {
+        for name in [
+            "default",
+            "work",
+            "logs",
+            "term",
+            "term-",
+            "term-abc-1",
+            "term-1-x",
+            "term-1",
+            "term-1-2-3",
+            "",
+        ] {
+            assert!(
+                !is_implicit_session_name(name),
+                "should not be implicit: {name:?}"
+            );
+        }
+    }
+
+    #[test]
+    fn implicit_shape_matches() {
+        assert!(is_implicit_session_name("term-1781470634216-76685"));
+        assert!(is_implicit_session_name("term-0-0"));
+    }
+}

src/pty.rs

@@ -1,14 +1,42 @@
 use anyhow::{Context, Result};
-use portable_pty::{CommandBuilder, MasterPty, NativePtySystem, PtySize, PtySystem};
+use portable_pty::{Child, CommandBuilder, MasterPty, NativePtySystem, PtySize, PtySystem};
 use std::io::{Read, Write};
-use std::path::Path;
+use std::os::unix::io::{AsRawFd, FromRawFd, RawFd};
+use std::path::{Path, PathBuf};
 use std::sync::{Arc, Mutex};
 use std::thread;
 use tokio::sync::mpsc;
 
+// Keep live terminal output comfortably below common path MTUs after Dosh's
+// protocol header, AEAD tag, UDP/IP headers, and bincode framing. Full-screen
+// TUIs often write several KiB on the first draw; sending that as one UDP
+// datagram can fragment and vanish, leaving only a blank alternate screen.
+const PTY_OUTPUT_CHUNK_BYTES: usize = 1024;
+
+/// Backing for a PTY master held by the server.
+///
+/// `Owned` means this process spawned the shell as a child and is responsible
+/// for it: dropping the handle kills the shell. This is the original,
+/// non-persistent model and stays the default.
+///
+/// `Adopted` means the shell lives in a separate holder process and this handle
+/// only borrows the master fd (received over a Unix socket via SCM_RIGHTS).
+/// Dropping it must NOT kill the shell — it just closes our copy of the fd and
+/// stops the reader thread, leaving the holder + shell alive so a server restart
+/// can re-adopt them.
+enum Backing {
+    Owned {
+        child: Mutex<Box<dyn Child + Send + Sync>>,
+        _master: Box<dyn MasterPty + Send>,
+    },
+    Adopted {
+        master: Mutex<std::fs::File>,
+    },
+}
+
 pub struct PtyHandle {
     writer: Arc<Mutex<Box<dyn Write + Send>>>,
-    _master: Box<dyn MasterPty + Send>,
+    backing: Backing,
 }
 
 impl PtyHandle {
@@ -20,14 +48,69 @@ impl PtyHandle {
     }
 
     pub fn resize(&self, cols: u16, rows: u16) -> Result<()> {
-        self._master.resize(PtySize {
+        match &self.backing {
+            Backing::Owned { _master, .. } => {
+                _master.resize(PtySize {
                     rows,
                     cols,
                     pixel_width: 0,
                     pixel_height: 0,
                 })?;
+            }
+            Backing::Adopted { master } => {
+                let file = master.lock().expect("pty master poisoned");
+                resize_fd(file.as_raw_fd(), cols, rows)?;
+            }
+        }
         Ok(())
     }
+
+    /// True for a handle backed by a separate holder process. Such a handle must
+    /// be detached (not killed) when the server lets go of a session, so the
+    /// shell survives a server restart.
+    pub fn is_persistent(&self) -> bool {
+        matches!(self.backing, Backing::Adopted { .. })
+    }
+
+    /// Terminate the shell process backing this PTY and reap it.
+    ///
+    /// Only meaningful for an `Owned` backing (the server spawned the shell as a
+    /// child). For an `Adopted` backing the shell belongs to the holder process,
+    /// so this is a no-op here; reaping a persistent session is done by asking
+    /// the holder to shut down (see `persist::request_shutdown`).
+    pub fn kill(&self) {
+        if let Backing::Owned { child, .. } = &self.backing
+            && let Ok(mut child) = child.lock()
+        {
+            let _ = child.kill();
+            let _ = child.wait();
+        }
+    }
+}
+
+impl Drop for PtyHandle {
+    fn drop(&mut self) {
+        // Adopted handles must NOT kill the shell: it lives in the holder so it
+        // can outlive this server. Dropping just closes our fd / stops the
+        // reader. Owned handles keep the original kill-on-drop behavior.
+        if let Backing::Owned { .. } = &self.backing {
+            self.kill();
+        }
+    }
+}
+
+fn resize_fd(fd: RawFd, cols: u16, rows: u16) -> Result<()> {
+    let winsize = libc::winsize {
+        ws_row: rows,
+        ws_col: cols,
+        ws_xpixel: 0,
+        ws_ypixel: 0,
+    };
+    let rc = unsafe { libc::ioctl(fd, libc::TIOCSWINSZ, &winsize) };
+    if rc != 0 {
+        return Err(std::io::Error::last_os_error()).context("TIOCSWINSZ");
+    }
+    Ok(())
 }
 
 #[derive(Debug)]
@@ -54,12 +137,82 @@ pub fn spawn_pty_session(
             pixel_height: 0,
         })
         .context("open pty")?;
+    let cmd = build_shell_command(shell, env);
+    let child = pair.slave.spawn_command(cmd).context("spawn shell")?;
+    drop(pair.slave);
+
+    let writer = pair.master.take_writer().context("take pty writer")?;
+    let reader = pair.master.try_clone_reader().context("clone pty reader")?;
+    spawn_reader_thread(session, reader, tx)?;
+
+    Ok(PtyHandle {
+        writer: Arc::new(Mutex::new(writer)),
+        backing: Backing::Owned {
+            child: Mutex::new(child),
+            _master: pair.master,
+        },
+    })
+}
+
+/// Whether this host has a terminfo entry for `term`, searching the standard
+/// ncurses directories. Both the legacy single-letter (`x/xterm`) and the
+/// hashed (`78/xterm`) subdirectory layouts are checked.
+fn terminfo_available(term: &str) -> bool {
+    let Some(first) = term.chars().next() else {
+        return false;
+    };
+    let letter = first.to_string();
+    let hashed = format!("{:x}", first as u32);
+    let mut dirs: Vec<PathBuf> = Vec::new();
+    if let Ok(t) = std::env::var("TERMINFO")
+        && !t.is_empty()
+    {
+        dirs.push(PathBuf::from(t));
+    }
+    if let Some(home) = dirs::home_dir() {
+        dirs.push(home.join(".terminfo"));
+    }
+    if let Ok(td) = std::env::var("TERMINFO_DIRS") {
+        for d in td.split(':').filter(|d| !d.is_empty()) {
+            dirs.push(PathBuf::from(d));
+        }
+    }
+    for d in [
+        "/etc/terminfo",
+        "/lib/terminfo",
+        "/usr/share/terminfo",
+        "/usr/lib/terminfo",
+        "/usr/share/lib/terminfo",
+    ] {
+        dirs.push(PathBuf::from(d));
+    }
+    dirs.iter()
+        .any(|dir| dir.join(&letter).join(term).exists() || dir.join(&hashed).join(term).exists())
+}
+
+/// Build the [`CommandBuilder`] for a dosh shell, identically for the in-process
+/// `spawn_pty_session` and the out-of-process holder, so a persistent session's
+/// environment matches a non-persistent one.
+pub fn build_shell_command(shell: &str, env: &[(String, String)]) -> CommandBuilder {
     let mut cmd = CommandBuilder::new(shell);
-    cmd.env("TERM", "xterm-256color");
     cmd.env("COLORTERM", "truecolor");
     for (name, value) in env {
         cmd.env(name, value);
     }
+    // The client's TERM is propagated, but a server that lacks that terminal's
+    // terminfo entry (e.g. xterm-ghostty, xterm-kitty) breaks ncurses apps like
+    // tmux/vim with "missing or unsuitable terminal". Keep the requested TERM
+    // only when this host actually has its terminfo; otherwise fall back to a
+    // universally available entry so remote apps always work.
+    let term = match env
+        .iter()
+        .find(|(n, _)| n == "TERM")
+        .map(|(_, v)| v.as_str())
+    {
+        Some(requested) if terminfo_available(requested) => requested.to_string(),
+        _ => "xterm-256color".to_string(),
+    };
+    cmd.env("TERM", term);
     cmd.env("SHELL", shell);
     if let Some(home) = dirs::home_dir() {
         cmd.env("HOME", home.as_os_str());
@@ -68,11 +221,39 @@ pub fn spawn_pty_session(
     } else if let Some(parent) = Path::new(shell).parent() {
         cmd.env("PWD", parent.as_os_str());
     }
-    let _child = pair.slave.spawn_command(cmd).context("spawn shell")?;
-    drop(pair.slave);
+    cmd
+}
 
-    let writer = pair.master.take_writer().context("take pty writer")?;
-    let mut reader = pair.master.try_clone_reader().context("clone pty reader")?;
+/// Build a [`PtyHandle`] from a master fd received from a holder process.
+///
+/// `master_fd` is an fd this handle takes ownership of (it is wrapped in a
+/// `File` and closed on drop). The shell is NOT a child of this process; it
+/// belongs to the holder, so dropping this handle leaves it running.
+pub fn adopt_pty_from_fd(
+    session: String,
+    master_fd: RawFd,
+    tx: mpsc::UnboundedSender<PtyOutput>,
+) -> Result<PtyHandle> {
+    // Take ownership of the fd. A clone gives us an independent reader so the
+    // reader thread and the writer/resize side hold separate `File`s and don't
+    // get closed out from under each other.
+    let master = unsafe { std::fs::File::from_raw_fd(master_fd) };
+    let reader_file = master.try_clone().context("clone master for reader")?;
+    let writer_file = master.try_clone().context("clone master for writer")?;
+    spawn_reader_thread(session, Box::new(reader_file), tx)?;
+    Ok(PtyHandle {
+        writer: Arc::new(Mutex::new(Box::new(writer_file))),
+        backing: Backing::Adopted {
+            master: Mutex::new(master),
+        },
+    })
+}
+
+fn spawn_reader_thread(
+    session: String,
+    mut reader: Box<dyn Read + Send>,
+    tx: mpsc::UnboundedSender<PtyOutput>,
+) -> Result<()> {
     let reader_session = session.clone();
     thread::Builder::new()
         .name(format!("dosh-pty-{session}"))
@@ -89,12 +270,14 @@ pub fn spawn_pty_session(
                         break;
                     }
                     Ok(n) => {
+                        for chunk in buf[..n].chunks(PTY_OUTPUT_CHUNK_BYTES) {
                             let _ = tx.send(PtyOutput {
                                 session: reader_session.clone(),
-                            bytes: buf[..n].to_vec(),
+                                bytes: chunk.to_vec(),
                                 exited: false,
                             });
                         }
+                    }
                     Err(_) => {
                         let _ = tx.send(PtyOutput {
                             session: reader_session.clone(),
@@ -107,9 +290,24 @@ pub fn spawn_pty_session(
             }
         })
         .context("spawn pty reader")?;
+    Ok(())
+}
 
-    Ok(PtyHandle {
-        writer: Arc::new(Mutex::new(writer)),
-        _master: pair.master,
-    })
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn terminfo_available_detects_known_and_unknown() {
+        // A near-universal entry should be present on any host with ncurses.
+        assert!(terminfo_available("xterm") || terminfo_available("xterm-256color"));
+        // Bogus / empty names must report missing so we fall back.
+        assert!(!terminfo_available("definitely-not-a-real-terminal-xyz"));
+        assert!(!terminfo_available(""));
+    }
+
+    #[test]
+    fn pty_output_chunk_size_stays_mtu_safe() {
+        assert!(PTY_OUTPUT_CHUNK_BYTES <= 1200);
+    }
 }

src/ssh_agent.rs

@@ -1,6 +1,6 @@
 use crate::native::{
     ForwardingRequest, NativeClientHello, NativeServerHello, NativeUserAuth,
-    parse_ssh_ed25519_public_blob, user_auth_transcript,
+    is_supported_user_key_algorithm, parse_ssh_ed25519_public_blob, user_auth_transcript,
 };
 use anyhow::{Context, Result, anyhow, bail};
 use std::io::{Read, Write};
@@ -12,12 +12,16 @@ const SSH2_AGENTC_REQUEST_IDENTITIES: u8 = 11;
 const SSH2_AGENT_IDENTITIES_ANSWER: u8 = 12;
 const SSH2_AGENTC_SIGN_REQUEST: u8 = 13;
 const SSH2_AGENT_SIGN_RESPONSE: u8 = 14;
+const SSH_AGENT_RSA_SHA2_512: u32 = 4;
 const MAX_AGENT_PACKET: usize = 256 * 1024;
 
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct AgentIdentity {
     pub key_blob: Vec<u8>,
-    pub public_key: [u8; 32],
+    pub public_key_algorithm: String,
+    pub public_key: Vec<u8>,
+    pub sign_algorithm: String,
+    pub sign_flags: u32,
     pub comment: String,
 }
 
@@ -38,13 +42,13 @@ pub fn sign_user_auth_with_agent_at(
 ) -> Result<NativeUserAuth> {
     let mut agent = UnixStream::connect(socket_path.as_ref())
         .with_context(|| format!("connect ssh-agent {}", socket_path.as_ref().display()))?;
-    let identities = request_ed25519_identities(&mut agent)?;
+    let identities = request_supported_identities(&mut agent)?;
     let identity = identities
         .first()
-        .ok_or_else(|| anyhow!("ssh-agent has no ssh-ed25519 identities"))?;
+        .ok_or_else(|| anyhow!("ssh-agent has no supported identities"))?;
     let mut auth = NativeUserAuth {
-        public_key_algorithm: "ssh-ed25519".to_string(),
-        public_key: identity.public_key.to_vec(),
+        public_key_algorithm: identity.sign_algorithm.clone(),
+        public_key: identity.public_key.clone(),
         signature: Vec::new(),
         requested_forwardings,
     };
@@ -54,7 +58,7 @@ pub fn sign_user_auth_with_agent_at(
     Ok(auth)
 }
 
-fn request_ed25519_identities(agent: &mut UnixStream) -> Result<Vec<AgentIdentity>> {
+fn request_supported_identities(agent: &mut UnixStream) -> Result<Vec<AgentIdentity>> {
     write_agent_packet(agent, &[SSH2_AGENTC_REQUEST_IDENTITIES])?;
     let payload = read_agent_packet(agent)?;
     let mut cursor = payload.as_slice();
@@ -72,18 +76,49 @@ fn request_ed25519_identities(agent: &mut UnixStream) -> Result<Vec<AgentIdentit
     for _ in 0..count {
         let key_blob = read_ssh_string(&mut cursor)?.to_vec();
         let comment = String::from_utf8_lossy(read_ssh_string(&mut cursor)?).to_string();
-        if let Ok(public_key) = parse_ssh_ed25519_public_blob(&key_blob) {
-            identities.push(AgentIdentity {
-                key_blob,
-                public_key,
-                comment,
-            });
+        if let Some(identity) = supported_identity(key_blob, comment)? {
+            identities.push(identity);
         }
     }
     anyhow::ensure!(cursor.is_empty(), "trailing data in ssh-agent identities");
     Ok(identities)
 }
 
+fn supported_identity(key_blob: Vec<u8>, comment: String) -> Result<Option<AgentIdentity>> {
+    let algorithm = key_blob_algorithm(&key_blob)?;
+    if !is_supported_user_key_algorithm(&algorithm) {
+        return Ok(None);
+    }
+    let identity = match algorithm.as_str() {
+        "ssh-ed25519" => AgentIdentity {
+            public_key_algorithm: algorithm.clone(),
+            public_key: parse_ssh_ed25519_public_blob(&key_blob)?.to_vec(),
+            sign_algorithm: "ssh-ed25519".to_string(),
+            sign_flags: 0,
+            key_blob,
+            comment,
+        },
+        "ecdsa-sha2-nistp256" => AgentIdentity {
+            public_key_algorithm: algorithm.clone(),
+            public_key: key_blob.clone(),
+            sign_algorithm: algorithm,
+            sign_flags: 0,
+            key_blob,
+            comment,
+        },
+        "ssh-rsa" => AgentIdentity {
+            public_key_algorithm: algorithm,
+            public_key: key_blob.clone(),
+            sign_algorithm: "rsa-sha2-512".to_string(),
+            sign_flags: SSH_AGENT_RSA_SHA2_512,
+            key_blob,
+            comment,
+        },
+        _ => return Ok(None),
+    };
+    Ok(Some(identity))
+}
+
 fn sign_with_agent(
     agent: &mut UnixStream,
     identity: &AgentIdentity,
@@ -93,7 +128,7 @@ fn sign_with_agent(
     request.push(SSH2_AGENTC_SIGN_REQUEST);
     write_ssh_string(&mut request, &identity.key_blob);
     write_ssh_string(&mut request, transcript);
-    request.extend_from_slice(&0u32.to_be_bytes());
+    request.extend_from_slice(&identity.sign_flags.to_be_bytes());
     write_agent_packet(agent, &request)?;
 
     let payload = read_agent_packet(agent)?;
@@ -114,20 +149,17 @@ fn sign_with_agent(
 
     let mut signature_cursor = signature_blob;
     let algorithm = read_ssh_string(&mut signature_cursor)?;
+    let algorithm = String::from_utf8_lossy(algorithm);
     anyhow::ensure!(
-        algorithm == b"ssh-ed25519",
-        "ssh-agent returned unsupported signature algorithm {}",
-        String::from_utf8_lossy(algorithm)
+        algorithm == identity.sign_algorithm,
+        "ssh-agent returned signature algorithm {algorithm}, expected {}",
+        identity.sign_algorithm
     );
     let signature = read_ssh_string(&mut signature_cursor)?;
     anyhow::ensure!(
         signature_cursor.is_empty(),
         "trailing data in ssh-agent signature blob"
     );
-    anyhow::ensure!(
-        signature.len() == 64,
-        "ssh-agent Ed25519 signature was not 64 bytes"
-    );
     Ok(signature.to_vec())
 }
 
@@ -182,6 +214,12 @@ fn write_ssh_string(out: &mut Vec<u8>, value: &[u8]) {
     out.extend_from_slice(value);
 }
 
+fn key_blob_algorithm(blob: &[u8]) -> Result<String> {
+    let mut cursor = blob;
+    let algorithm = read_ssh_string(&mut cursor)?;
+    Ok(String::from_utf8_lossy(algorithm).to_string())
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -253,8 +291,8 @@ mod tests {
             protocol_version: crate::native::NATIVE_PROTOCOL_VERSION,
             client_random: [1u8; 32],
             client_ephemeral_public: [2u8; 32],
-            requested_host: "palav".to_string(),
-            requested_user: "palav".to_string(),
+            requested_host: "homelab".to_string(),
+            requested_user: "alice".to_string(),
             requested_session: "term".to_string(),
             requested_mode: "read-write".to_string(),
             terminal_size: (80, 24),

tests/parser_robustness.rs

@@ -0,0 +1,415 @@
+//! Parser robustness tests (Track B, spec milestone 5 / §16 "Fuzz packet parsing").
+//!
+//! These throw arbitrary/garbage bytes at every reachable public parser in the
+//! `dosh` library and assert that NONE of them panic. A parser is allowed to
+//! return `Ok` (if the bytes happened to be valid) or `Err`, but a panic on
+//! untrusted input is a denial-of-service / robustness bug against a hostile
+//! network attacker (threat model §5: "Active network attacker that can spoof
+//! ... or modify packets").
+//!
+//! Determinism: a fixed-seed PRNG (`rand::rngs::StdRng`) is used so failures are
+//! reproducible. No external dependencies beyond what is already in Cargo.toml.
+
+use std::panic::{self, AssertUnwindSafe};
+
+use dosh::auth::{
+    AttachTicketPlain, BootstrapResponse, SealedAttachTicket, decode_bootstrap, open_attach_ticket,
+    verify_attach_ticket,
+};
+use dosh::native::{
+    AuthorizedKey, HostPublicKey, KnownHost, NativeAuthOk, NativeClientHello, NativeServerHello,
+    NativeUserAuth, parse_authorized_keys, parse_host_public_key_line, parse_known_hosts,
+    parse_ssh_ed25519_public_blob, verify_known_host,
+};
+use dosh::protocol::{
+    self, AttachOk, AttachReject, BootstrapAttachRequest, Frame, Header, Input,
+    NativeAuthCheckOkBody, NativeAuthOkBody, NativeClientHelloBody, NativeServerHelloBody,
+    NativeUserAuthBody, Packet, Resize, ResumeRequest, StreamClose, StreamData, StreamEof,
+    StreamOpen, StreamOpenOk, StreamOpenReject, StreamWindowAdjust, TicketAttachBody,
+    TicketAttachEnvelope, TicketAttachOkEnvelope,
+};
+use rand::rngs::StdRng;
+use rand::{Rng, RngCore, SeedableRng};
+
+const ITERATIONS: usize = 4000;
+
+/// Run `f` and convert a panic into a test failure with a descriptive message.
+fn no_panic<F: FnOnce()>(label: &str, input: &[u8], f: F) {
+    let result = panic::catch_unwind(AssertUnwindSafe(f));
+    assert!(
+        result.is_ok(),
+        "parser `{label}` PANICKED on input ({} bytes): {:02x?}",
+        input.len(),
+        input,
+    );
+}
+
+/// Generate a variety of "interesting" byte buffers for a given iteration.
+fn fuzz_bytes(rng: &mut StdRng) -> Vec<u8> {
+    let strategy = rng.gen_range(0..7u8);
+    match strategy {
+        0 => {
+            let len = rng.gen_range(0..1200);
+            let mut buf = vec![0u8; len];
+            rng.fill_bytes(&mut buf);
+            buf
+        }
+        1 => {
+            let len = rng.gen_range(0..16);
+            let mut buf = vec![0u8; len];
+            rng.fill_bytes(&mut buf);
+            buf
+        }
+        2 => {
+            let len = rng.gen_range(0..(protocol::HEADER_LEN + 64));
+            let mut buf = vec![0u8; len];
+            rng.fill_bytes(&mut buf);
+            buf
+        }
+        3 => vec![0u8; rng.gen_range(0..256)],
+        4 => vec![0xffu8; rng.gen_range(0..256)],
+        5 => {
+            // A valid-magic prefix followed by garbage to drive deeper paths.
+            let mut buf = Vec::new();
+            buf.extend_from_slice(protocol::MAGIC);
+            buf.push(protocol::VERSION);
+            let extra = rng.gen_range(0..256);
+            let mut tail = vec![0u8; extra];
+            rng.fill_bytes(&mut tail);
+            buf.extend_from_slice(&tail);
+            buf
+        }
+        _ => {
+            // Large length prefixes to provoke huge allocations / overflow in
+            // length fields (a classic deserialization hazard).
+            let mut buf = Vec::new();
+            buf.extend_from_slice(&u64::MAX.to_le_bytes());
+            let extra = rng.gen_range(0..64);
+            let mut tail = vec![0u8; extra];
+            rng.fill_bytes(&mut tail);
+            buf.extend_from_slice(&tail);
+            buf
+        }
+    }
+}
+
+/// Generate a possibly-valid UTF-8 string from random bytes (for text parsers).
+fn fuzz_text(rng: &mut StdRng) -> String {
+    let len = rng.gen_range(0..256);
+    let mut s = String::new();
+    for _ in 0..len {
+        let pick = rng.gen_range(0..10u8);
+        let ch = match pick {
+            0 => ' ',
+            1 => '\n',
+            2 => '\t',
+            3 => '=',
+            4 => ',',
+            5 => '"',
+            6 => '/',
+            7 => rng.gen_range(b'a'..=b'z') as char,
+            8 => rng.gen_range(b'0'..=b'9') as char,
+            _ => char::from_u32(rng.gen_range(0..0x110000)).unwrap_or('?'),
+        };
+        s.push(ch);
+    }
+    s
+}
+
+#[test]
+fn protocol_packet_decode_never_panics() {
+    let mut rng = StdRng::seed_from_u64(0xD05Au64);
+    for _ in 0..ITERATIONS {
+        let input = fuzz_bytes(&mut rng);
+        no_panic("protocol::decode", &input, || {
+            let _ = protocol::decode(&input);
+        });
+        no_panic("Header::parse", &input, || {
+            let _ = Header::parse(&input);
+        });
+    }
+}
+
+/// `from_body` deserializes a bincode body into each protocol/native struct.
+/// On the wire this runs on attacker-controlled bytes, so it must never panic.
+#[test]
+fn protocol_from_body_never_panics() {
+    let mut rng = StdRng::seed_from_u64(0xBEEFu64);
+
+    macro_rules! body_target {
+        ($input:expr, $ty:ty) => {{
+            let input = $input;
+            no_panic(concat!("from_body::<", stringify!($ty), ">"), input, || {
+                let _ = protocol::from_body::<$ty>(input);
+            });
+        }};
+    }
+
+    for _ in 0..ITERATIONS {
+        let input = fuzz_bytes(&mut rng);
+        let input = input.as_slice();
+
+        // protocol.rs structs
+        body_target!(input, BootstrapAttachRequest);
+        body_target!(input, TicketAttachEnvelope);
+        body_target!(input, TicketAttachBody);
+        body_target!(input, TicketAttachOkEnvelope);
+        body_target!(input, AttachOk);
+        body_target!(input, AttachReject);
+        body_target!(input, ResumeRequest);
+        body_target!(input, Input);
+        body_target!(input, Resize);
+        body_target!(input, Frame);
+        body_target!(input, StreamOpen);
+        body_target!(input, StreamOpenOk);
+        body_target!(input, StreamOpenReject);
+        body_target!(input, StreamData);
+        body_target!(input, StreamWindowAdjust);
+        body_target!(input, StreamEof);
+        body_target!(input, StreamClose);
+
+        // native handshake wrapper bodies
+        body_target!(input, NativeClientHelloBody);
+        body_target!(input, NativeServerHelloBody);
+        body_target!(input, NativeUserAuthBody);
+        body_target!(input, NativeAuthOkBody);
+        body_target!(input, NativeAuthCheckOkBody);
+
+        // bare native handshake structs
+        body_target!(input, NativeClientHello);
+        body_target!(input, NativeServerHello);
+        body_target!(input, NativeUserAuth);
+        body_target!(input, NativeAuthOk);
+        body_target!(input, HostPublicKey);
+
+        // auth.rs structs (deserialized from untrusted material too)
+        body_target!(input, BootstrapResponse);
+        body_target!(input, SealedAttachTicket);
+        body_target!(input, AttachTicketPlain);
+    }
+}
+
+/// Full decode -> decrypt_body pipeline on garbage. decrypt should Err (not
+/// panic) on bad ciphertext / wrong key id / truncated body.
+#[test]
+fn protocol_decode_then_decrypt_never_panics() {
+    let mut rng = StdRng::seed_from_u64(0x1234_5678u64);
+    let key = [7u8; 32];
+    for _ in 0..ITERATIONS {
+        let input = fuzz_bytes(&mut rng);
+        no_panic("decode+decrypt_body", &input, || {
+            if let Ok(packet) = protocol::decode(&input) {
+                let _ = protocol::decrypt_body(&packet, &key, protocol::CLIENT_TO_SERVER);
+                let _ = protocol::decrypt_body(&packet, &key, protocol::SERVER_TO_CLIENT);
+            }
+        });
+    }
+}
+
+/// Mutate a single byte of a valid encrypted packet; decode and decrypt must
+/// not panic, and decryption of the mutated packet must fail (no double-apply).
+#[test]
+fn protocol_bit_flips_on_valid_packet_never_panic() {
+    let mut rng = StdRng::seed_from_u64(0x900Du64);
+    let key = [9u8; 32];
+    let conn_id = [3u8; 16];
+    for _ in 0..1000 {
+        let mut plaintext = vec![0u8; rng.gen_range(0..200)];
+        rng.fill_bytes(&mut plaintext);
+        let seq = rng.gen_range(1..u64::MAX);
+        let Ok(mut packet) = protocol::encode_encrypted(
+            protocol::PacketKind::Input,
+            conn_id,
+            seq,
+            0,
+            &key,
+            protocol::CLIENT_TO_SERVER,
+            &plaintext,
+        ) else {
+            continue;
+        };
+        if packet.is_empty() {
+            continue;
+        }
+        let idx = rng.gen_range(0..packet.len());
+        packet[idx] ^= 1 << rng.gen_range(0..8);
+        no_panic("flip+decode+decrypt", &packet, || {
+            if let Ok(decoded) = protocol::decode(&packet) {
+                let _ = protocol::decrypt_body(&decoded, &key, protocol::CLIENT_TO_SERVER);
+            }
+        });
+    }
+}
+
+#[test]
+fn ssh_ed25519_blob_parser_never_panics() {
+    let mut rng = StdRng::seed_from_u64(0x5511u64);
+    for _ in 0..ITERATIONS {
+        let input = fuzz_bytes(&mut rng);
+        no_panic("parse_ssh_ed25519_public_blob", &input, || {
+            let _ = parse_ssh_ed25519_public_blob(&input);
+        });
+    }
+    // Targeted: length prefixes that lie about the body length.
+    for bad_len in [0u32, 1, 31, 32, 33, u32::MAX, u32::MAX - 1] {
+        let mut buf = Vec::new();
+        buf.extend_from_slice(&bad_len.to_be_bytes());
+        buf.extend_from_slice(b"ssh-ed25519");
+        buf.extend_from_slice(&32u32.to_be_bytes());
+        buf.extend_from_slice(&[0u8; 16]);
+        no_panic("parse_ssh_ed25519_public_blob:lying-len", &buf, || {
+            let _ = parse_ssh_ed25519_public_blob(&buf);
+        });
+    }
+}
+
+#[test]
+fn authorized_keys_parser_never_panics() {
+    let mut rng = StdRng::seed_from_u64(0xA011u64);
+    for _ in 0..ITERATIONS {
+        let text = fuzz_text(&mut rng);
+        no_panic("parse_authorized_keys", text.as_bytes(), || {
+            let _ = parse_authorized_keys(&text);
+        });
+    }
+    let crafted = [
+        "ssh-ed25519",
+        "ssh-ed25519 ",
+        "ssh-ed25519 not-base64!!!",
+        "from= ssh-ed25519 AAAA",
+        "from=\"unterminated ssh-ed25519 AAAA",
+        "command=\"x\\\" ssh-ed25519 AAAA",
+        "permitopen=,,, ssh-ed25519 AAAA",
+        "restrict,no-port-forwarding,from=\"127.0.0.1\" ssh-ed25519 AAAA comment",
+        "ssh-rsa AAAA",
+        "\u{0}\u{0}\u{0} ssh-ed25519 AAAA",
+    ];
+    for line in crafted {
+        no_panic("parse_authorized_keys:crafted", line.as_bytes(), || {
+            let _ = parse_authorized_keys(line);
+        });
+    }
+}
+
+#[test]
+fn known_hosts_parser_never_panics() {
+    let mut rng = StdRng::seed_from_u64(0xC051u64);
+    for _ in 0..ITERATIONS {
+        let text = fuzz_text(&mut rng);
+        no_panic("parse_known_hosts", text.as_bytes(), || {
+            let _ = parse_known_hosts(&text);
+        });
+    }
+    let crafted = [
+        "host",
+        "host dosh-ed25519",
+        "host dosh-ed25519 not-base64!!!",
+        "host wrong-algo AAAA",
+        "host dosh-ed25519 AAAA first-seen=notnum source=tofu",
+        "host dosh-ed25519 AAAA first-seen= source=",
+        "* dosh-ed25519 AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA",
+    ];
+    for line in crafted {
+        no_panic("parse_known_hosts:crafted", line.as_bytes(), || {
+            let _ = parse_known_hosts(line);
+        });
+    }
+}
+
+#[test]
+fn host_public_key_line_parser_never_panics() {
+    let mut rng = StdRng::seed_from_u64(0x4002u64);
+    for _ in 0..ITERATIONS {
+        let text = fuzz_text(&mut rng);
+        no_panic("parse_host_public_key_line", text.as_bytes(), || {
+            let _ = parse_host_public_key_line(&text);
+        });
+    }
+}
+
+#[test]
+fn decode_bootstrap_never_panics() {
+    let mut rng = StdRng::seed_from_u64(0xB007u64);
+    for _ in 0..ITERATIONS {
+        let text = fuzz_text(&mut rng);
+        no_panic("decode_bootstrap", text.as_bytes(), || {
+            let _ = decode_bootstrap(&text);
+        });
+        // Also feed base64-shaped random for the decode path proper.
+        let raw = fuzz_bytes(&mut rng);
+        use base64::Engine;
+        let b64 = base64::engine::general_purpose::URL_SAFE_NO_PAD.encode(&raw);
+        no_panic("decode_bootstrap:b64", b64.as_bytes(), || {
+            let _ = decode_bootstrap(&b64);
+        });
+    }
+}
+
+#[test]
+fn attach_ticket_open_and_verify_never_panic() {
+    let mut rng = StdRng::seed_from_u64(0x7CE7u64);
+    let secret = [42u8; 32];
+    let psk = [11u8; 32];
+    for _ in 0..ITERATIONS {
+        let input = fuzz_bytes(&mut rng);
+        no_panic("open_attach_ticket", &input, || {
+            let _ = open_attach_ticket(&secret, &input);
+        });
+        no_panic("verify_attach_ticket", &input, || {
+            let _ = verify_attach_ticket(&secret, &input, &psk, "default", "read-write");
+        });
+    }
+}
+
+/// Throw garbage at the known-host verifier (file parse + host key compare).
+#[test]
+fn verify_known_host_with_garbage_keys_never_panics() {
+    let mut rng = StdRng::seed_from_u64(0x9090u64);
+    let dir = tempfile::tempdir().unwrap();
+    for _ in 0..500 {
+        let text = fuzz_text(&mut rng);
+        let path = dir.path().join("known_hosts");
+        std::fs::write(&path, &text).unwrap();
+        let mut key_bytes = [0u8; 32];
+        rng.fill_bytes(&mut key_bytes);
+        let host = HostPublicKey {
+            algorithm: "dosh-ed25519".to_string(),
+            key: key_bytes,
+        };
+        let host_name = fuzz_text(&mut rng);
+        no_panic("verify_known_host", text.as_bytes(), || {
+            let _ = verify_known_host(&path, &host_name, &host);
+        });
+    }
+}
+
+/// Regression guard: valid inputs still parse, so the fuzz harness isn't
+/// accidentally exercising a build where every path simply Errs.
+#[test]
+fn valid_inputs_still_parse() {
+    let key = [5u8; 32];
+    let blob = dosh::native::ssh_ed25519_public_blob(&key);
+    assert_eq!(parse_ssh_ed25519_public_blob(&blob).unwrap(), key);
+
+    let session_key = [1u8; 32];
+    let packet = protocol::encode_encrypted(
+        protocol::PacketKind::Input,
+        [2u8; 16],
+        1,
+        0,
+        &session_key,
+        protocol::CLIENT_TO_SERVER,
+        b"hello",
+    )
+    .unwrap();
+    let decoded: Packet = protocol::decode(&packet).unwrap();
+    let plain = protocol::decrypt_body(&decoded, &session_key, protocol::CLIENT_TO_SERVER).unwrap();
+    assert_eq!(plain, b"hello");
+
+    assert!(parse_authorized_keys("").unwrap().is_empty());
+    assert!(parse_known_hosts("# just a comment\n").unwrap().is_empty());
+
+    // Reference types only otherwise used in macro expansions / signatures.
+    let _ = std::mem::size_of::<AuthorizedKey>();
+    let _ = std::mem::size_of::<KnownHost>();
+}

tests/protocol_auth.rs

@@ -126,6 +126,139 @@ fn attach_ticket_is_sealed_and_verifies_scope() {
     );
 }
 
+#[test]
+fn peek_foreign_wire_version_flags_only_version_skew() {
+    let key = crypto::random_32();
+    let mut packet = protocol::encode_encrypted(
+        PacketKind::Input,
+        crypto::random_16(),
+        1,
+        0,
+        &key,
+        CLIENT_TO_SERVER,
+        b"hi",
+    )
+    .unwrap();
+    // A correctly framed packet for this build is not "foreign".
+    assert_eq!(protocol::peek_foreign_wire_version(&packet), None);
+    // Bumping the wire version byte makes it undecodable but recognizable.
+    packet[4] = protocol::VERSION.wrapping_add(7);
+    assert_eq!(
+        protocol::peek_foreign_wire_version(&packet),
+        Some(protocol::VERSION.wrapping_add(7))
+    );
+    assert!(protocol::decode(&packet).is_err());
+    // Non-Dosh datagrams and runts are ignored.
+    assert_eq!(protocol::peek_foreign_wire_version(b"XXXX\x01"), None);
+    assert_eq!(protocol::peek_foreign_wire_version(b"DOS"), None);
+}
+
+#[test]
+fn rekey_key_derivation_agrees_and_is_independent_per_epoch() {
+    use dosh::native::derive_rekey_session_key;
+
+    // The handshake/current key both peers already share.
+    let current_key = crypto::random_32();
+    let current_id = protocol::session_key_id(&current_key);
+    // Fresh server-generated material, delivered confidentially in the Rekey.
+    let material = crypto::random_32();
+
+    // Both peers derive identically from shared current key + shipped material.
+    let server_view = derive_rekey_session_key(&current_key, &material, &current_id, 1).unwrap();
+    let client_view = derive_rekey_session_key(&current_key, &material, &current_id, 1).unwrap();
+    assert_eq!(server_view, client_view);
+
+    // The rotated key must not equal the handshake/current key.
+    assert_ne!(server_view, current_key);
+
+    // A different epoch (or different material) yields a different key.
+    let next_epoch = derive_rekey_session_key(&current_key, &material, &current_id, 2).unwrap();
+    assert_ne!(server_view, next_epoch);
+    let other_material = crypto::random_32();
+    let other = derive_rekey_session_key(&current_key, &other_material, &current_id, 1).unwrap();
+    assert_ne!(server_view, other);
+}
+
+#[test]
+fn rekey_round_trip_decrypts_old_and_new_epoch_packets() {
+    use dosh::native::derive_rekey_session_key;
+
+    let key_epoch0 = crypto::random_32();
+    let id0 = protocol::session_key_id(&key_epoch0);
+    let conn_id = crypto::random_16();
+
+    // Pre-rekey packet sealed under epoch-0 key.
+    let pre = protocol::encode_encrypted(
+        PacketKind::Frame,
+        conn_id,
+        5,
+        0,
+        &key_epoch0,
+        protocol::SERVER_TO_CLIENT,
+        b"before",
+    )
+    .unwrap();
+
+    // Rotate to epoch 1.
+    let material = crypto::random_32();
+    let key_epoch1 = derive_rekey_session_key(&key_epoch0, &material, &id0, 1).unwrap();
+    let post = protocol::encode_encrypted(
+        PacketKind::Frame,
+        conn_id,
+        6,
+        0,
+        &key_epoch1,
+        protocol::SERVER_TO_CLIENT,
+        b"after",
+    )
+    .unwrap();
+
+    let pre = protocol::decode(&pre).unwrap();
+    let post = protocol::decode(&post).unwrap();
+
+    // Each epoch's key carries its own session_key_id; the receiver picks the
+    // right one and both decrypt correctly.
+    assert_eq!(pre.header.session_key_id, id0);
+    assert_eq!(
+        pre.header.session_key_id,
+        protocol::session_key_id(&key_epoch0)
+    );
+    assert_eq!(
+        post.header.session_key_id,
+        protocol::session_key_id(&key_epoch1)
+    );
+    assert_eq!(
+        protocol::decrypt_body(&pre, &key_epoch0, protocol::SERVER_TO_CLIENT).unwrap(),
+        b"before"
+    );
+    assert_eq!(
+        protocol::decrypt_body(&post, &key_epoch1, protocol::SERVER_TO_CLIENT).unwrap(),
+        b"after"
+    );
+
+    // A stale-epoch packet under the wrong key is rejected via session_key_id
+    // BEFORE any AEAD work — ignorable, not a fatal decrypt error.
+    let err = protocol::decrypt_body(&post, &key_epoch0, protocol::SERVER_TO_CLIENT).unwrap_err();
+    assert!(err.to_string().contains("session key id"));
+}
+
+#[test]
+fn check_native_protocol_version_names_the_mismatch() {
+    use dosh::native::{NATIVE_PROTOCOL_VERSION, check_native_protocol_version};
+    check_native_protocol_version(NATIVE_PROTOCOL_VERSION, "server").unwrap();
+    let err = check_native_protocol_version(NATIVE_PROTOCOL_VERSION.wrapping_add(1), "server")
+        .unwrap_err();
+    let message = err.to_string();
+    assert!(
+        message.contains(protocol::VERSION_MISMATCH_REASON),
+        "expected actionable upgrade message, got {message:?}"
+    );
+    assert!(
+        message.contains("server"),
+        "should name the wrong peer: {message:?}"
+    );
+}
+
 #[test]
 fn replay_window_rejects_duplicates_but_allows_bounded_out_of_order() {
     let mut replay = ReplayWindow::new(8);