Harden release artifact verification

.github/workflows/ci.yml

@@ -15,8 +15,14 @@ jobs:
       - uses: dtolnay/rust-toolchain@stable
       - name: Format check
         run: cargo fmt -- --check
+      - name: Shell syntax check
+        run: sh -n install.sh scripts/*.sh
+      - name: Clippy
+        run: cargo clippy --all-targets -- -D warnings
       - name: Test
-        run: cargo test
+        run: cargo test --all-targets
+      - name: TUI harness
+        run: sh scripts/tui-harness.sh
       - name: Build release
         run: cargo build --release
       - name: Docker SSH benchmark gate
@@ -86,6 +92,39 @@ jobs:
             target/dosh-release/dosh-*
             !target/dosh-release/stage/**
 
+  publish-gitea-release:
+    if: github.event_name == 'workflow_dispatch' || startsWith(github.ref, 'refs/tags/')
+    needs: package-release
+    runs-on: ubuntu-latest
+    env:
+      GITEA_TOKEN: ${{ secrets.GITEA_TOKEN }}
+      GITEA_URL: ${{ secrets.GITEA_URL || 'https://git.palav.dev' }}
+      GITEA_REPO: ${{ secrets.GITEA_REPO || 'Palav/dosh' }}
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/download-artifact@v4
+        with:
+          pattern: dosh-*
+          path: target/dosh-release
+          merge-multiple: true
+      - name: Verify release artifacts
+        run: sh scripts/verify-release-artifacts.sh
+      - name: Skip Gitea upload without token
+        if: env.GITEA_TOKEN == ''
+        run: echo "GITEA_TOKEN secret is not configured; release artifacts were verified but not uploaded."
+      - name: Upload Gitea release assets
+        if: env.GITEA_TOKEN != ''
+        run: |
+          set -eu
+          case "$GITHUB_REF" in
+            refs/tags/*) tag="${GITHUB_REF_NAME}" ;;
+            *)
+              version="$(sed -n 's/^version = "\(.*\)"/\1/p' Cargo.toml | sed -n '1p')"
+              tag="v$version"
+              ;;
+          esac
+          scripts/upload-gitea-release.sh "$tag"
+
   remote-bench:
     runs-on: ubuntu-latest
     env:

Cargo.lock

@@ -436,7 +436,7 @@ dependencies = [
 
 [[package]]
 name = "dosh"
-version = "1.0.0-rc1"
+version = "1.0.0-rc42"
 dependencies = [
  "anyhow",
  "base64",

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "dosh"
-version = "1.0.0-rc1"
+version = "1.0.0-rc42"
 edition = "2024"
 license = "MIT"
 

Makefile

@@ -4,7 +4,7 @@ build:
 	cargo build --release
 
 test:
-	cargo test
+	cargo test --all-targets
 
 fmt:
 	cargo fmt
@@ -16,18 +16,18 @@ release-check:
 	cargo fmt --check
 	sh -n install.sh scripts/*.sh
 	cargo clippy --all-targets -- -D warnings
-	cargo test
+	cargo test --all-targets
 	$(MAKE) tui-harness
 
 1.0-check: release-check reconnect-check hostile-network-check persistence-check package-check
 
 reconnect-check:
 	cargo test --test integration_smoke resume_updates_udp_endpoint_for_roaming -- --nocapture
-	DOSH_SOAK_SECONDS=$${DOSH_SOAK_SECONDS:-300} cargo test --test integration_smoke sleep_roaming_soak_30m -- --ignored --nocapture
+	DOSH_SOAK_SECONDS=$${DOSH_SOAK_SECONDS:-1800} cargo test --test integration_smoke sleep_roaming_soak_30m -- --ignored --nocapture
 
 hostile-network-check:
 	cargo test --test hostile_network -- --nocapture
-	DOSH_BADNET_SOAK_SECONDS=$${DOSH_BADNET_SOAK_SECONDS:-300} cargo test --test hostile_network bad_network_tui_work_soak_30m -- --ignored --nocapture
+	DOSH_BADNET_SOAK_SECONDS=$${DOSH_BADNET_SOAK_SECONDS:-1800} cargo test --test hostile_network bad_network_tui_work_soak_30m -- --ignored --nocapture
 
 persistence-check:
 	cargo test --test integration_smoke session_survives_server_restart_same_shell_and_screen -- --nocapture
@@ -36,7 +36,9 @@ persistence-check:
 package-check:
 	$(MAKE) package-release-linux
 	$(MAKE) package-release-windows
-	sh scripts/verify-release-artifacts.sh
+	sh scripts/verify-release-artifacts.sh \
+		target/dosh-release/dosh-linux-x86_64.tar.gz \
+		target/dosh-release/dosh-windows-x86_64.zip
 
 install:
 	sh install.sh --from-current

README.md

@@ -44,6 +44,7 @@ dosh setup HOST
 dosh HOST
 dosh HOST COMMAND
 dosh update
+dosh update --client|--server|--both
 ```
 
 Useful commands:
@@ -67,6 +68,32 @@ dosh restart HOST
 Agent forwarding is opt-in with `-A` and must also be enabled on the server.
 File copy must be enabled by the server config.
 
+## Tracing
+
+For terminal/reconnect bugs, run a client with:
+
+```sh
+dosh trace HOST
+```
+
+The client log path is printed before the session starts. To choose it:
+
+```sh
+dosh trace --client-log /tmp/dosh-client.log HOST
+```
+
+Summarize collected traces with:
+
+```sh
+dosh trace report HOST --client-log /tmp/dosh-client.log
+```
+
+When `HOST` is given, Dosh fetches `/tmp/dosh-server.log` over SSH before
+building the report. Set `DOSH_TRACE=/tmp/dosh-server.log` on `dosh-server` for
+matching server events. Reports default to the latest traced client/server
+process run; add `--all-runs` to include older appended log entries. Trace byte
+prefixes are enabled for `dosh trace`, so use it only for short reproductions.
+
 ## VS Code
 
 Dosh can carry VS Code Remote-SSH through its transport:
@@ -97,6 +124,20 @@ cache_attach_tickets = true
 disconnect_status = true
 ```
 
+Example host entry:
+
+```toml
+[prod]
+ssh = "prod"
+ssh_config = "prod" # OpenSSH alias for IdentityFile, ProxyJump, SendEnv, etc.
+dosh_host = "prod.example.com"
+port = 50000
+```
+
+`ProxyJump` and `ProxyCommand` can be used for SSH setup, but the Dosh UDP
+endpoint still has to be reachable directly from the client. Set `dosh_host` to
+the reachable UDP hostname or IP when it differs from the SSH alias target.
+
 ## Rust Library
 
 Dosh exposes a Rust transport for encrypted, reconnecting application streams.

build.rs

@@ -1,3 +1,4 @@
+use std::env;
 use std::process::Command;
 
 fn git(args: &[&str]) -> Option<String> {
@@ -12,14 +13,29 @@ fn git(args: &[&str]) -> Option<String> {
 fn main() {
     println!("cargo:rerun-if-changed=.git/HEAD");
     println!("cargo:rerun-if-changed=.git/index");
+    println!("cargo:rerun-if-env-changed=DOSH_BUILD_GIT_HASH");
+    println!("cargo:rerun-if-env-changed=DOSH_BUILD_COMMIT_DATE");
+    println!("cargo:rerun-if-env-changed=DOSH_BUILD_GIT_DIRTY");
 
-    let hash = git(&["rev-parse", "--short=12", "HEAD"]).unwrap_or_else(|| "unknown".into());
+    let hash = env::var("DOSH_BUILD_GIT_HASH")
-    let date = git(&["show", "-s", "--format=%cs", "HEAD"]).unwrap_or_else(|| "unknown".into());
+        .ok()
-    let dirty = Command::new("git")
+        .filter(|value| !value.is_empty())
+        .or_else(|| git(&["rev-parse", "--short=12", "HEAD"]))
+        .unwrap_or_else(|| "unknown".into());
+    let date = env::var("DOSH_BUILD_COMMIT_DATE")
+        .ok()
+        .filter(|value| !value.is_empty())
+        .or_else(|| git(&["show", "-s", "--format=%cs", "HEAD"]))
+        .unwrap_or_else(|| "unknown".into());
+    let dirty = match env::var("DOSH_BUILD_GIT_DIRTY").ok().as_deref() {
+        Some("1" | "true" | "yes" | "+dirty") => "+dirty",
+        Some(_) => "",
+        None => Command::new("git")
             .args(["diff", "--quiet", "--ignore-submodules", "--"])
             .status()
             .map(|status| if status.success() { "" } else { "+dirty" })
-        .unwrap_or("");
+            .unwrap_or(""),
+    };
 
     println!("cargo:rustc-env=DOSH_GIT_HASH={hash}{dirty}");
     println!("cargo:rustc-env=DOSH_COMMIT_DATE={date}");

install.ps1

@@ -11,6 +11,7 @@ param(
     [string]$BinaryBase = $env:DOSH_BINARY_BASE,
     [string]$BinaryName = $env:DOSH_BINARY_NAME,
     [string]$BinaryVersion = $(if ($env:DOSH_BINARY_VERSION) { $env:DOSH_BINARY_VERSION } else { "latest" }),
+    [string]$UpdateCache = $(if ($env:DOSH_UPDATE_CACHE) { $env:DOSH_UPDATE_CACHE } else { Join-Path $HOME ".cache\dosh\source" }),
     [switch]$BinaryRequired = $($env:DOSH_BINARY_REQUIRED -and $env:DOSH_BINARY_REQUIRED -ne "0"),
     [switch]$ForceConfig
 )
@@ -100,14 +101,127 @@ function Release-LatestTagDownloadUrl {
     return $null
 }
 
+function Version-Core($Value) {
+    $base = $Value.TrimStart("v").Split("+")[0]
+    $base.Split("-")[0]
+}
+
+function Version-Prerelease($Value) {
+    $base = $Value.TrimStart("v").Split("+")[0]
+    $dash = $base.IndexOf("-")
+    if ($dash -lt 0) {
+        return ""
+    }
+    $base.Substring($dash + 1).ToLowerInvariant()
+}
+
+function Version-Parts($Value) {
+    [regex]::Matches((Version-Core $Value), "\d+") | ForEach-Object { [int64]$_.Value }
+}
+
+function Compare-Prerelease($Left, $Right) {
+    if (-not $Left -and -not $Right) {
+        return 0
+    }
+    if (-not $Left) {
+        return 1
+    }
+    if (-not $Right) {
+        return -1
+    }
+    if ($Left -eq $Right) {
+        return 0
+    }
+    if ($Left -match "(?i)^rc(\d+)$" -and $Right -match "(?i)^rc(\d+)$") {
+        $leftRc = [int64]([regex]::Match($Left, "(?i)^rc(\d+)$").Groups[1].Value)
+        $rightRc = [int64]([regex]::Match($Right, "(?i)^rc(\d+)$").Groups[1].Value)
+        return $leftRc.CompareTo($rightRc)
+    }
+    return [string]::CompareOrdinal($Left, $Right)
+}
+
+function Compare-DoshVersion($Left, $Right) {
+    $leftParts = @(Version-Parts $Left)
+    $rightParts = @(Version-Parts $Right)
+    $width = [Math]::Max($leftParts.Count, $rightParts.Count)
+    for ($i = 0; $i -lt $width; $i++) {
+        $l = if ($i -lt $leftParts.Count) { $leftParts[$i] } else { 0 }
+        $r = if ($i -lt $rightParts.Count) { $rightParts[$i] } else { 0 }
+        if ($l -lt $r) { return -1 }
+        if ($l -gt $r) { return 1 }
+    }
+    return Compare-Prerelease (Version-Prerelease $Left) (Version-Prerelease $Right)
+}
+
+function Current-SourceVersion {
+    if (Test-Path "Cargo.toml") {
+        $raw = Get-Content "Cargo.toml" -Raw
+    } else {
+        $web = Repo-WebBase $Repo
+        if (-not $web) {
+            return $null
+        }
+        try {
+            $raw = (Invoke-WebRequest -UseBasicParsing -Uri "$web/raw/branch/main/Cargo.toml").Content
+        }
+        catch {
+            return $null
+        }
+    }
+    if ($raw -match '(?m)^version = "([^"]+)"') {
+        return $Matches[1]
+    }
+    return $null
+}
+
+function Latest-ReleaseTag {
+    $web = Repo-WebBase $Repo
+    if (-not $web) {
+        return $null
+    }
+    try {
+        $response = Invoke-WebRequest -UseBasicParsing -Uri "$web/releases/latest" -MaximumRedirection 5
+        $effective = $null
+        if ($response.BaseResponse.ResponseUri) {
+            $effective = $response.BaseResponse.ResponseUri.AbsoluteUri
+        } elseif ($response.BaseResponse.RequestMessage -and $response.BaseResponse.RequestMessage.RequestUri) {
+            $effective = $response.BaseResponse.RequestMessage.RequestUri.AbsoluteUri
+        }
+        $prefix = "$web/releases/tag/"
+        if ($effective -and $effective.StartsWith($prefix)) {
+            return $effective.Substring($prefix.Length)
+        }
+    }
+    catch {
+        return $null
+    }
+    return $null
+}
+
+function Latest-ReleaseIsStale {
+    if ($BinaryUrl -or $BinaryBase -or $BinaryVersion -ne "latest") {
+        return $false
+    }
+    $latest = Latest-ReleaseTag
+    $current = Current-SourceVersion
+    if (-not $latest -or -not $current) {
+        return $false
+    }
+    $latestVersion = $latest.TrimStart("v")
+    if ((Compare-DoshVersion $latestVersion $current) -lt 0) {
+        Write-Warning "latest release $latestVersion is older than source $current; skipping stale prebuilt"
+        return $true
+    }
+    return $false
+}
+
 function Verify-ArchiveChecksum($Url, $Archive) {
     $checksumPath = "$Archive.sha256"
     try {
         Invoke-WebRequest -UseBasicParsing -Uri "$Url.sha256" -OutFile $checksumPath
     }
     catch {
-        Write-Warning "prebuilt checksum unavailable; continuing without sidecar verification"
+        throw "prebuilt checksum unavailable; refusing unverified binary for $Url"
-        return
     }
     $expected = ((Get-Content $checksumPath -Raw).Trim() -split "\s+")[0].ToLowerInvariant()
     $actual = (Get-FileHash -Algorithm SHA256 $Archive).Hash.ToLowerInvariant()
@@ -155,11 +269,44 @@ function Install-Binary($Source, $Destination) {
     }
 }
 
+function Normalize-PathForCompare($Path) {
+    [System.IO.Path]::GetFullPath($Path).TrimEnd(
+        [System.IO.Path]::DirectorySeparatorChar,
+        [System.IO.Path]::AltDirectorySeparatorChar
+    )
+}
+
+function Assert-NoRelativePathSegments($Path) {
+    foreach ($segment in ($Path -split '[\\/]')) {
+        if ($segment -eq "." -or $segment -eq "..") {
+            throw "refusing unsafe update cache path: $Path"
+        }
+    }
+}
+
+function Assert-SafeUpdateCache($Path) {
+    if (-not $Path) {
+        throw "refusing unsafe update cache path: $Path"
+    }
+    Assert-NoRelativePathSegments $Path
+    $full = Normalize-PathForCompare $Path
+    $root = Normalize-PathForCompare ([System.IO.Path]::GetPathRoot($full))
+    $homePath = Normalize-PathForCompare $HOME
+    $homeCache = Normalize-PathForCompare (Join-Path $HOME ".cache")
+    if ($full -eq $root -or $full -eq $homePath -or $full -eq $homeCache) {
+        throw "refusing unsafe update cache path: $Path"
+    }
+    $full
+}
+
 $bindir = Join-Path $Prefix "bin"
 $configDir = Join-Path $HOME ".config\dosh"
 New-Item -ItemType Directory -Force -Path $bindir, $configDir | Out-Null
 
 function Install-Prebuilt {
+    if (Latest-ReleaseIsStale) {
+        return $false
+    }
     $url = Release-LatestTagDownloadUrl
     if (-not $url) {
         $url = Release-DownloadUrl
@@ -200,7 +347,6 @@ function Install-Prebuilt {
 
 function Install-FromSource {
     Require-Command cargo
-    $tmp = $null
     if (Test-Path "Cargo.toml") {
         $src = (Get-Location).Path
     } else {
@@ -208,9 +354,20 @@ function Install-FromSource {
             throw "DOSH_REPO is required when running the installer from irm/iex"
         }
         Require-Command git
-        $tmp = Join-Path ([System.IO.Path]::GetTempPath()) ("dosh-" + [guid]::NewGuid())
+        $sourceCache = Assert-SafeUpdateCache $UpdateCache
-        git clone --depth 1 $Repo $tmp | Out-Null
+        $parent = Split-Path -Parent $sourceCache
-        $src = $tmp
+        New-Item -ItemType Directory -Force -Path $parent | Out-Null
+        if (Test-Path (Join-Path $sourceCache ".git")) {
+            git -C $sourceCache remote set-url origin $Repo
+            git -C $sourceCache fetch --depth 1 origin main
+            git -C $sourceCache checkout -q -B main FETCH_HEAD
+        } else {
+            if (Test-Path $sourceCache) {
+                Remove-Item -Recurse -Force $sourceCache
+            }
+            git clone --depth 1 --branch main $Repo $sourceCache | Out-Null
+        }
+        $src = $sourceCache
     }
 
     try {
@@ -222,9 +379,6 @@ function Install-FromSource {
     }
     finally {
         Pop-Location
-        if ($tmp) {
-            Remove-Item -Recurse -Force $tmp
-        }
     }
 }
 
@@ -261,10 +415,38 @@ predict = true
 predict_mode = "experimental"
 cache_attach_tickets = true
 credential_cache = "~/.local/share/dosh/credentials"
+auth_preference = "native,ssh"
+trust_on_first_use = false
+native_auth_timeout_ms = 700
+known_hosts = "~/.config/dosh/known_hosts"
+identity_files = ["~/.ssh/id_ed25519"]
+use_ssh_agent = true
+forward_agent = false
 escape_key = "^]"
 "@ | Set-Content -NoNewline -Encoding utf8 $clientConfig
 }
 
+$hostsConfig = Join-Path $configDir "hosts.toml"
+if ($ForceConfig -or -not (Test-Path $hostsConfig)) {
+    $defaultServer = if ($Server) { $Server } else { "user@example.com" }
+    $hostUdp = if ($DoshHost) { $DoshHost } else { $defaultServer }
+    @"
+# Example:
+# [server]
+# ssh = "server"
+# dosh_host = "server.example.com"
+# port = 50000
+# default_command = "tm"
+# predict = true
+
+[default]
+ssh = "$defaultServer"
+dosh_host = "$hostUdp"
+port = $Port
+predict = true
+"@ | Set-Content -NoNewline -Encoding utf8 $hostsConfig
+}
+
 $userPath = [Environment]::GetEnvironmentVariable("Path", "User")
 if (-not (($userPath -split ';') -contains $bindir)) {
     [Environment]::SetEnvironmentVariable("Path", "$userPath;$bindir", "User")
@@ -281,5 +463,6 @@ Write-Host "  $bindir\dosh.exe update --check"
 Write-Host ""
 Write-Host "Client config:"
 Write-Host "  $configDir\client.toml"
+Write-Host "  $configDir\hosts.toml"
 Write-Host ""
 Write-Host "Open a new terminal for PATH changes to apply."

install.sh

@@ -119,6 +119,37 @@ need() {
   fi
 }
 
+normalize_update_cache_path() {
+  case "$1" in
+    /*) printf '%s\n' "$1" ;;
+    *) printf '%s\n' "$(pwd)/$1" ;;
+  esac | sed 's#//*#/#g; s#/$##'
+}
+
+safe_update_cache_path() {
+  raw="$1"
+  if [ -z "$raw" ]; then
+    echo "refusing unsafe update cache path: $raw" >&2
+    exit 2
+  fi
+  case "$raw" in
+    "."|".."|./*|../*|*/.|*/..|*/./*|*/../*)
+      echo "refusing unsafe update cache path: $raw" >&2
+      exit 2
+      ;;
+  esac
+  normalized="$(normalize_update_cache_path "$raw")"
+  home_norm="$(normalize_update_cache_path "$HOME")"
+  home_cache_norm="$(normalize_update_cache_path "$HOME/.cache")"
+  case "$normalized" in
+    ""|"/"|"$home_norm"|"$home_cache_norm")
+      echo "refusing unsafe update cache path: $raw" >&2
+      exit 2
+      ;;
+  esac
+  printf '%s\n' "$normalized"
+}
+
 ensure_cargo() {
   if command -v cargo >/dev/null 2>&1; then
     return
@@ -222,6 +253,113 @@ release_latest_tag_download_url() {
   esac
 }
 
+version_core() {
+  value="${1#v}"
+  value="${value%%+*}"
+  printf '%s\n' "${value%%-*}"
+}
+
+version_prerelease() {
+  value="${1#v}"
+  value="${value%%+*}"
+  case "$value" in
+    *-*) printf '%s\n' "${value#*-}" ;;
+    *) printf '\n' ;;
+  esac
+}
+
+version_core_part() {
+  version="$1"
+  index="$2"
+  version_core "$version" \
+    | sed 's/[^0-9][^0-9]*/ /g' \
+    | awk -v index="$index" '{ value=$index; if (value == "") value=0; print value }'
+}
+
+prerelease_less_than() {
+  left="$1"
+  right="$2"
+  if [ -z "$left" ] && [ -z "$right" ]; then
+    return 1
+  fi
+  if [ -z "$left" ]; then
+    return 1
+  fi
+  if [ -z "$right" ]; then
+    return 0
+  fi
+  if [ "$left" = "$right" ]; then
+    return 1
+  fi
+  left_rc="$(printf '%s\n' "$left" | sed -n 's/^[Rr][Cc]\([0-9][0-9]*\)$/\1/p')"
+  right_rc="$(printf '%s\n' "$right" | sed -n 's/^[Rr][Cc]\([0-9][0-9]*\)$/\1/p')"
+  if [ -n "$left_rc" ] && [ -n "$right_rc" ]; then
+    [ "$left_rc" -lt "$right_rc" ]
+    return
+  fi
+  first="$(printf '%s\n%s\n' "$left" "$right" | LC_ALL=C sort | sed -n '1p')"
+  [ "$first" = "$left" ]
+}
+
+version_less_than() {
+  left="$1"
+  right="$2"
+  for index in 1 2 3 4 5 6 7 8; do
+    lpart="$(version_core_part "$left" "$index")"
+    rpart="$(version_core_part "$right" "$index")"
+    if [ "$lpart" -lt "$rpart" ]; then
+      return 0
+    fi
+    if [ "$lpart" -gt "$rpart" ]; then
+      return 1
+    fi
+  done
+  prerelease_less_than "$(version_prerelease "$left")" "$(version_prerelease "$right")"
+}
+
+current_source_version() {
+  if [ -f Cargo.toml ]; then
+    sed -n 's/^version = "\(.*\)"/\1/p' Cargo.toml | sed -n '1p'
+    return 0
+  fi
+  [ -n "$repo" ] || return 1
+  web_base="$(repo_web_base "$repo")" || return 1
+  curl -fsSL "$web_base/raw/branch/main/Cargo.toml" 2>/dev/null \
+    | sed -n 's/^version = "\(.*\)"/\1/p' \
+    | sed -n '1p'
+}
+
+latest_release_tag() {
+  [ -n "$repo" ] || return 1
+  web_base="$(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\n' "$tag"
+      ;;
+    *)
+      return 1
+      ;;
+  esac
+}
+
+latest_release_is_stale() {
+  if [ -n "$binary_url" ] || [ -n "$binary_base" ] || [ "$binary_version" != "latest" ]; then
+    return 1
+  fi
+  latest="$(latest_release_tag || true)"
+  current="$(current_source_version || true)"
+  [ -n "$latest" ] && [ -n "$current" ] || return 1
+  latest="${latest#v}"
+  if version_less_than "$latest" "$current"; then
+    echo "latest release $latest is older than source $current; skipping stale prebuilt" >&2
+    return 0
+  fi
+  return 1
+}
+
 find_extracted_binary() {
   find "$1" -type f -name "$2" 2>/dev/null | sed -n '1p'
 }
@@ -263,8 +401,8 @@ verify_archive_checksum() {
   archive="$2"
   checksum_file="$3"
   if ! curl -fsL "$url.sha256" -o "$checksum_file"; then
-    echo "prebuilt checksum unavailable; continuing without sidecar verification" >&2
+    echo "prebuilt checksum unavailable; refusing unverified binary for $url" >&2
-    return 0
+    return 1
   fi
   expected="$(awk '{print $1}' "$checksum_file" | sed -n '1p')"
   actual="$(sha256_file "$archive")" || {
@@ -312,6 +450,9 @@ verify_archive_version() {
 }
 
 try_install_prebuilt() {
+  if latest_release_is_stale; then
+    return 1
+  fi
   download_url="$(release_latest_tag_download_url || release_download_url)" || return 1
   tmpdir="$(mktemp -d)"
   archive="$tmpdir/$(release_artifact_name)"
@@ -356,12 +497,7 @@ install_from_source() {
       echo "DOSH_REPO or --repo is required when running the installer from curl" >&2
       exit 2
     fi
-    case "$update_cache" in
+    update_cache="$(safe_update_cache_path "$update_cache")"
-      ""|"/"|"$HOME"|"$HOME/"|"$HOME/.cache")
-        echo "refusing unsafe update cache path: $update_cache" >&2
-        exit 2
-        ;;
-    esac
     need git
     mkdir -p "$(dirname "$update_cache")"
     if [ -d "$update_cache/.git" ]; then

scripts/bench-local.sh

@@ -67,6 +67,7 @@ cleanup() {
     kill "$server_pid" 2>/dev/null || true
     wait "$server_pid" 2>/dev/null || true
   fi
+  pkill -f "$server_bin hold --runtime-dir $home/sessions/run" 2>/dev/null || true
   rm -rf "$home"
 }
 trap cleanup EXIT INT TERM
@@ -86,6 +87,7 @@ scrollback = 5000
 auth_ttl_secs = 30
 attach_ticket_ttl_secs = 3600
 allow_attach_tickets = true
+persist_sessions = false
 client_timeout_secs = 60
 retransmit_window = 256
 default_input_mode = "read-write"

scripts/package-release.sh

@@ -52,6 +52,22 @@ else
   release_dir="target/release"
 fi
 
+if command -v git >/dev/null 2>&1 && git rev-parse --is-inside-work-tree >/dev/null 2>&1; then
+  if [ -z "${DOSH_BUILD_GIT_HASH:-}" ]; then
+    export DOSH_BUILD_GIT_HASH="$(git rev-parse --short=12 HEAD)"
+  fi
+  if [ -z "${DOSH_BUILD_COMMIT_DATE:-}" ]; then
+    export DOSH_BUILD_COMMIT_DATE="$(git show -s --format=%cs HEAD)"
+  fi
+  if [ -z "${DOSH_BUILD_GIT_DIRTY+x}" ]; then
+    if git diff --quiet --ignore-submodules --; then
+      export DOSH_BUILD_GIT_DIRTY=0
+    else
+      export DOSH_BUILD_GIT_DIRTY=1
+    fi
+  fi
+fi
+
 if [ "$os" = "windows" ]; then
   if [ -n "$target" ]; then
     cargo build --release --target "$target" --bin dosh-client --bin dosh-bench

scripts/upload-gitea-release.sh

@@ -11,6 +11,8 @@ Environment:
   GITEA_REPO      owner/repo, default Palav/dosh
   GITEA_TOKEN     Token with release write permission
   GITEA_TITLE     Release title, default TAG
+  DOSH_RELEASE_ALLOW_PARTIAL=1
+                  Allow uploading an incomplete platform set. Default: refuse.
 EOF
 }
 
@@ -31,6 +33,11 @@ repo="${GITEA_REPO:-Palav/dosh}"
 token="${GITEA_TOKEN:-}"
 title="${GITEA_TITLE:-$tag}"
 expected_version="${tag#v}"
+allow_partial="${DOSH_RELEASE_ALLOW_PARTIAL:-0}"
+release_prerelease=false
+case "$expected_version" in
+  *-*) release_prerelease=true ;;
+esac
 
 artifact_version() {
   artifact="$1"
@@ -80,6 +87,42 @@ if [ "$#" -eq 0 ]; then
   done
 fi
 
+require_complete_release_artifacts() {
+  [ "$allow_partial" = "1" ] && return 0
+  missing=0
+  for required in \
+    dosh-linux-x86_64.tar.gz \
+    dosh-macos-aarch64.tar.gz \
+    dosh-macos-x86_64.tar.gz \
+    dosh-windows-x86_64.zip; do
+    found=0
+    checksum_found=0
+    for artifact in "$@"; do
+      name="$(basename "$artifact")"
+      if [ "$name" = "$required" ]; then
+        found=1
+      fi
+      if [ "$name" = "$required.sha256" ]; then
+        checksum_found=1
+      fi
+    done
+    if [ "$found" -ne 1 ]; then
+      echo "missing required release artifact: $required" >&2
+      missing=1
+    fi
+    if [ "$checksum_found" -ne 1 ]; then
+      echo "missing required release checksum: $required.sha256" >&2
+      missing=1
+    fi
+  done
+  if [ "$missing" -ne 0 ]; then
+    echo "refusing partial release upload; set DOSH_RELEASE_ALLOW_PARTIAL=1 to override" >&2
+    exit 1
+  fi
+}
+
+require_complete_release_artifacts "$@"
+
 api="$base/api/v1/repos/$repo"
 auth_header="Authorization: token $token"
 
@@ -92,7 +135,7 @@ elif [ -n "$release_json" ]; then
 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" "$tag")"
+  payload="$(printf '{"tag_name":"%s","target_commitish":"main","name":"%s","body":"Dosh release %s","draft":false,"prerelease":%s}\n' "$tag" "$title" "$tag" "$release_prerelease")"
   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')"
@@ -106,6 +149,14 @@ if [ -z "$release_id" ]; then
   exit 1
 fi
 
+metadata_payload="$(printf '{"name":"%s","body":"Dosh release %s","draft":false,"prerelease":%s}\n' "$title" "$tag" "$release_prerelease")"
+curl -fsS \
+  -H "$auth_header" \
+  -H 'Content-Type: application/json' \
+  -X PATCH \
+  "$api/releases/$release_id" \
+  -d "$metadata_payload" >/dev/null
+
 delete_existing_asset() {
   name="$1"
   if ! command -v jq >/dev/null 2>&1; then

scripts/verify-release-artifacts.sh

@@ -22,11 +22,78 @@ artifact_version() {
   esac
 }
 
+archive_contains() {
+  artifact="$1"
+  member="$2"
+  case "$artifact" in
+    *.tar.gz)
+      tar -tzf "$artifact" "$member" >/dev/null 2>&1
+      ;;
+    *.zip)
+      unzip -Z1 "$artifact" 2>/dev/null | grep -Fx "$member" >/dev/null 2>&1
+      ;;
+    *)
+      return 1
+      ;;
+  esac
+}
+
+expected_members() {
+  artifact_name="$(basename -- "$1")"
+  case "$artifact_name" in
+    dosh-windows-*.zip)
+      cat <<EOF
+dosh/VERSION
+dosh/bin/dosh.exe
+dosh/bin/dosh-client.exe
+dosh/bin/dosh-bench.exe
+EOF
+      ;;
+    dosh-*.tar.gz)
+      cat <<EOF
+dosh/VERSION
+dosh/bin/dosh
+dosh/bin/dosh-client
+dosh/bin/dosh-server
+dosh/bin/dosh-auth
+dosh/bin/dosh-bench
+EOF
+      ;;
+    *)
+      cat <<EOF
+dosh/VERSION
+EOF
+      ;;
+  esac
+}
+
+checksum_value() {
+  artifact="$1"
+  if command -v sha256sum >/dev/null 2>&1; then
+    sha256sum "$artifact" | awk '{print $1}'
+  elif command -v shasum >/dev/null 2>&1; then
+    shasum -a 256 "$artifact" | awk '{print $1}'
+  else
+    return 1
+  fi
+}
+
+verify_checksum() {
+  artifact="$1"
+  checksum="$artifact.sha256"
+  expected="$(awk '{print $1; exit}' "$checksum")"
+  actual="$(checksum_value "$artifact" || true)"
+  [ -n "$actual" ] && [ "$actual" = "$expected" ]
+}
+
+if [ "$#" -gt 0 ]; then
+  artifacts="$*"
+else
+  artifacts="$out_dir/dosh-linux-x86_64.tar.gz $out_dir/dosh-macos-aarch64.tar.gz $out_dir/dosh-macos-x86_64.tar.gz $out_dir/dosh-windows-x86_64.zip"
+fi
+
 failed=0
-for artifact in \
+for artifact in $artifacts; do
-  "$out_dir/dosh-linux-x86_64.tar.gz" \
-  "$out_dir/dosh-macos-aarch64.tar.gz" \
-  "$out_dir/dosh-windows-x86_64.zip"; do
   if [ ! -f "$artifact" ]; then
     echo "missing release artifact: $artifact" >&2
     failed=1
@@ -35,12 +102,21 @@ for artifact in \
   if [ ! -f "$artifact.sha256" ]; then
     echo "missing release checksum: $artifact.sha256" >&2
     failed=1
+  elif ! verify_checksum "$artifact"; then
+    echo "release checksum mismatch: $artifact" >&2
+    failed=1
   fi
   actual="$(artifact_version "$artifact" || true)"
   if [ "$actual" != "$version" ]; then
     echo "artifact version mismatch: $artifact has ${actual:-unknown}, expected $version" >&2
     failed=1
   fi
+  for member in $(expected_members "$artifact"); do
+    if ! archive_contains "$artifact" "$member"; then
+      echo "artifact missing expected member: $artifact:$member" >&2
+      failed=1
+    fi
+  done
 done
 
 exit "$failed"

src/client.rs

@@ -13,6 +13,7 @@ use crate::protocol::{
 };
 use crate::ssh_agent;
 use crate::transport::{DoshTransport, SessionRole, SessionTransportConfig, TransportConfig};
+use crate::udp::{recv_udp_retrying_transient, send_udp_retrying_transient};
 use anyhow::{Context, Result, anyhow, bail};
 use std::net::{SocketAddr, ToSocketAddrs};
 use std::path::PathBuf;
@@ -214,10 +215,10 @@ impl DoshClientBuilder {
                 hello: hello.clone(),
             })?,
         )?;
-        socket.send_to(&packet, peer_addr).await?;
+        send_udp_retrying_transient(&socket, &packet, peer_addr, timeout).await?;
 
         let mut buf = vec![0u8; 65535];
-        let (n, _) = tokio::time::timeout(timeout, socket.recv_from(&mut buf)).await??;
+        let (n, _) = recv_udp_retrying_transient(&socket, &mut buf, timeout).await?;
         let packet = protocol::decode(&buf[..n])?;
         if packet.header.kind != PacketKind::NativeServerHello {
             if packet.header.kind == PacketKind::AttachReject {
@@ -261,8 +262,8 @@ impl DoshClientBuilder {
             CLIENT_TO_SERVER,
             &protocol::to_body(&NativeUserAuthBody { auth })?,
         )?;
-        socket.send_to(&auth_packet, peer_addr).await?;
+        send_udp_retrying_transient(&socket, &auth_packet, peer_addr, timeout).await?;
-        let (n, _) = tokio::time::timeout(timeout, socket.recv_from(&mut buf)).await??;
+        let (n, _) = recv_udp_retrying_transient(&socket, &mut buf, timeout).await?;
         let packet = protocol::decode(&buf[..n])?;
         if packet.header.kind != PacketKind::NativeAuthOk {
             if packet.header.kind == PacketKind::AttachReject {

src/config.rs

@@ -5,6 +5,7 @@ use std::fs;
 use std::path::PathBuf;
 
 #[derive(Debug, Clone, Serialize, Deserialize)]
+#[serde(default)]
 pub struct ServerConfig {
     pub port: u16,
     pub bind: String,
@@ -95,6 +96,7 @@ impl Default for ServerConfig {
 }
 
 #[derive(Debug, Clone, Serialize, Deserialize)]
+#[serde(default)]
 pub struct ClientConfig {
     pub update_repo: Option<String>,
     pub update_port: Option<u16>,
@@ -150,6 +152,12 @@ pub struct ClientConfig {
 #[derive(Debug, Clone, Default, Serialize, Deserialize)]
 pub struct HostConfig {
     pub ssh: Option<String>,
+    /// Optional OpenSSH config host name to use for SSH-backed bootstrap,
+    /// trust/setup/doctor checks, and native-auth identity selection. This lets
+    /// a Dosh host keep a separate UDP endpoint while still inheriting
+    /// alias-scoped OpenSSH settings like IdentityFile, ProxyJump, and SendEnv.
+    #[serde(default)]
+    pub ssh_config: Option<String>,
     pub user: Option<String>,
     pub dosh_host: Option<String>,
     pub port: Option<u16>,
@@ -324,3 +332,63 @@ pub fn expand_tilde(path: &str) -> PathBuf {
     }
     PathBuf::from(path)
 }
+
+#[cfg(test)]
+mod tests {
+    use super::{ClientConfig, ServerConfig};
+
+    #[test]
+    fn old_client_configs_fill_new_fields_from_defaults() {
+        let raw = r#"
+server = "palav"
+dosh_port = 50000
+"#;
+
+        let config: ClientConfig = toml::from_str(raw).expect("parse old client config");
+
+        assert_eq!(config.server, "palav");
+        assert!(config.predict);
+        assert_eq!(config.predict_mode, "experimental");
+        assert_eq!(config.auth_preference, "native,ssh");
+        assert_eq!(config.native_auth_timeout_ms, 700);
+        assert_eq!(config.known_hosts, "~/.config/dosh/known_hosts");
+        assert_eq!(config.identity_files, vec!["~/.ssh/id_ed25519"]);
+        assert!(config.use_ssh_agent);
+        assert!(!config.forward_agent);
+        assert!(config.disconnect_status);
+        assert_eq!(config.escape_key, "^]");
+        assert!(config.send_env.iter().any(|value| value == "TERM"));
+    }
+
+    #[test]
+    fn old_server_configs_fill_new_fields_from_defaults() {
+        let raw = r#"
+port = 50000
+"#;
+
+        let config: ServerConfig = toml::from_str(raw).expect("parse old server config");
+
+        assert_eq!(config.port, 50000);
+        assert_eq!(config.bind, "0.0.0.0");
+        assert_eq!(config.client_timeout_secs, 2_592_000);
+        assert_eq!(config.output_frame_interval_ms, 16);
+        assert!(config.native_auth);
+        assert_eq!(config.host_key, "~/.config/dosh/host_key");
+        assert!(
+            config
+                .authorized_keys
+                .iter()
+                .any(|path| path == "~/.ssh/authorized_keys")
+        );
+        assert_eq!(config.native_auth_rate_limit_per_minute, 30);
+        assert_eq!(config.rekey_after_packets, 100_000);
+        assert_eq!(config.rekey_after_secs, 3600);
+        assert!(config.allow_tcp_forwarding);
+        assert!(!config.allow_remote_forwarding);
+        assert!(!config.allow_agent_forwarding);
+        assert!(config.allow_file_transfer);
+        assert!(config.allow_exec_command);
+        assert!(config.persist_sessions);
+        assert!(config.accept_env.iter().any(|value| value == "TERM"));
+    }
+}

src/exec_service.rs

@@ -32,6 +32,7 @@ impl FrameDecoder {
             }
             let len = u32::from_be_bytes(self.buf[..4].try_into().unwrap()) as usize;
             if len > FRAME_MAX_LEN {
+                self.buf.clear();
                 bail!("exec protocol frame too large: {len} bytes");
             }
             if self.buf.len() < 4 + len {
@@ -69,3 +70,23 @@ fn encode_frame(payload: &[u8]) -> Result<Vec<u8>> {
     out.extend_from_slice(payload);
     Ok(out)
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn oversized_frame_clears_decoder_state() {
+        let mut decoder = FrameDecoder::default();
+        let too_large = ((FRAME_MAX_LEN + 1) as u32).to_be_bytes();
+        assert!(decoder.push(&too_large).is_err());
+
+        let valid = encode_response(&ExecResponse::Exit { code: Some(0) }).unwrap();
+        let frames = decoder.push(&valid).unwrap();
+        assert_eq!(frames.len(), 1);
+        assert_eq!(
+            decode_response(&frames[0]).unwrap(),
+            ExecResponse::Exit { code: Some(0) }
+        );
+    }
+}

src/file_transfer.rs

@@ -18,6 +18,14 @@ pub enum FileRequest {
         path: String,
         mode: Option<u32>,
     },
+    Readlink {
+        path: String,
+    },
+    Symlink {
+        path: String,
+        target: String,
+        overwrite: bool,
+    },
     Remove {
         path: String,
         recursive: bool,
@@ -46,13 +54,35 @@ pub enum FileRequest {
 #[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
 pub enum FileResponse {
     Ok,
-    Resume { offset: u64 },
+    Resume {
-    Stat { meta: FileMeta },
+        offset: u64,
-    List { entries: Vec<FileEntry> },
+        prefix_sha256: Option<[u8; 32]>,
-    Start { meta: FileMeta, offset: u64 },
+    },
-    Chunk { offset: u64, bytes: Vec<u8> },
+    Stat {
-    Done { sha256: [u8; 32], bytes: u64 },
+        meta: FileMeta,
-    Error { message: String },
+    },
+    List {
+        entries: Vec<FileEntry>,
+    },
+    LinkTarget {
+        target: String,
+    },
+    Start {
+        meta: FileMeta,
+        offset: u64,
+        prefix_sha256: Option<[u8; 32]>,
+    },
+    Chunk {
+        offset: u64,
+        bytes: Vec<u8>,
+    },
+    Done {
+        sha256: [u8; 32],
+        bytes: u64,
+    },
+    Error {
+        message: String,
+    },
 }
 
 #[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
@@ -93,6 +123,7 @@ impl FrameDecoder {
             }
             let len = u32::from_be_bytes(self.buf[..4].try_into().unwrap()) as usize;
             if len > FRAME_MAX_LEN {
+                self.buf.clear();
                 bail!("file protocol frame too large: {len} bytes");
             }
             if self.buf.len() < 4 + len {
@@ -135,6 +166,12 @@ pub fn parse_copy_endpoint(raw: &str) -> CopyEndpoint {
     if looks_like_windows_path(raw) {
         return CopyEndpoint::Local(PathBuf::from(raw));
     }
+    if let Some((host, path)) = parse_bracketed_remote_endpoint(raw) {
+        return CopyEndpoint::Remote { host, path };
+    }
+    if raw.starts_with('[') {
+        return CopyEndpoint::Local(PathBuf::from(raw));
+    }
     let Some(index) = raw.find(':') else {
         return CopyEndpoint::Local(PathBuf::from(raw));
     };
@@ -153,6 +190,25 @@ pub fn parse_copy_endpoint(raw: &str) -> CopyEndpoint {
     }
 }
 
+fn parse_bracketed_remote_endpoint(raw: &str) -> Option<(String, String)> {
+    let rest = raw.strip_prefix('[')?;
+    let close = rest.find(']')?;
+    let host = &rest[..close];
+    let suffix = &rest[close + 1..];
+    if host.is_empty() || host.contains('/') || host.contains('\\') || !suffix.starts_with(':') {
+        return None;
+    }
+    let path = &suffix[1..];
+    Some((
+        host.to_string(),
+        if path.is_empty() {
+            ".".to_string()
+        } else {
+            path.to_string()
+        },
+    ))
+}
+
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub enum CopyEndpoint {
     Local(PathBuf),
@@ -233,6 +289,18 @@ mod tests {
         assert_eq!(frames.len(), 1);
     }
 
+    #[test]
+    fn oversized_frame_clears_decoder_state() {
+        let mut decoder = FrameDecoder::default();
+        let too_large = ((FRAME_MAX_LEN + 1) as u32).to_be_bytes();
+        assert!(decoder.push(&too_large).is_err());
+
+        let valid = encode_response(&FileResponse::Ok).unwrap();
+        let frames = decoder.push(&valid).unwrap();
+        assert_eq!(frames.len(), 1);
+        assert_eq!(decode_response(&frames[0]).unwrap(), FileResponse::Ok);
+    }
+
     #[test]
     fn copy_endpoint_parses_scp_style_but_not_windows_drive() {
         assert_eq!(
@@ -247,4 +315,30 @@ mod tests {
             CopyEndpoint::Local(PathBuf::from("C:\\Users\\palav\\x"))
         );
     }
+
+    #[test]
+    fn copy_endpoint_parses_bracketed_ipv6_remote_paths() {
+        assert_eq!(
+            parse_copy_endpoint("[2001:db8::1]:/var/log/syslog"),
+            CopyEndpoint::Remote {
+                host: "2001:db8::1".to_string(),
+                path: "/var/log/syslog".to_string()
+            }
+        );
+        assert_eq!(
+            parse_copy_endpoint("[::1]:"),
+            CopyEndpoint::Remote {
+                host: "::1".to_string(),
+                path: ".".to_string()
+            }
+        );
+        assert_eq!(
+            parse_copy_endpoint("[bad/host]:path"),
+            CopyEndpoint::Local(PathBuf::from("[bad/host]:path"))
+        );
+        assert_eq!(
+            parse_copy_endpoint("[::1]"),
+            CopyEndpoint::Local(PathBuf::from("[::1]"))
+        );
+    }
 }

src/lib.rs

@@ -5,7 +5,9 @@
 //! handle native authentication, host key checks, roaming, keepalives, reliable
 //! streams, and service routing. Use [`transport::DoshTransport`] only when an
 //! application already owns session establishment and wants direct access to the
-//! encrypted stream transport.
+//! encrypted stream transport. The SDK receive loops drive retransmission and
+//! keepalives while waiting, so simple applications can call `recv().await`
+//! without building their own maintenance loop.
 
 pub mod auth;
 pub mod build_info;
@@ -22,4 +24,6 @@ pub mod protocol;
 pub mod pty;
 pub mod server;
 pub mod ssh_agent;
+pub mod trace;
 pub mod transport;
+pub mod udp;

src/persist.rs

@@ -23,12 +23,14 @@ 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::sync::Mutex;
 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';
 const HOLDER_STARTUP_TIMEOUT: Duration = Duration::from_millis(750);
+static SCREEN_WRITE_LOCK: Mutex<()> = Mutex::new(());
 
 /// 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.
@@ -140,13 +142,28 @@ pub fn save_screen(
         // No holder runtime for this session (non-persistent): nothing to do.
         return Ok(());
     }
+    let _guard = SCREEN_WRITE_LOCK
+        .lock()
+        .map_err(|_| anyhow!("screen persistence lock poisoned"))?;
+    let path = screen_path(&dir);
+    if existing_screen_output_seq(&path).is_some_and(|existing| existing >= output_seq) {
+        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)
+    atomic_write(&path, &buf)
+}
+
+fn existing_screen_output_seq(path: &Path) -> Option<u64> {
+    let data = std::fs::read(path).ok()?;
+    if data.len() < 12 {
+        return None;
+    }
+    Some(u64::from_be_bytes(data[4..12].try_into().ok()?))
 }
 
 /// A restored screen for a re-adopted session.
@@ -619,6 +636,20 @@ mod tests {
         assert_eq!(loaded.snapshot, snap);
     }
 
+    #[test]
+    fn save_screen_never_overwrites_newer_snapshot_with_older_seq() {
+        let tmp = tempfile::tempdir().unwrap();
+        let sessions_dir = tmp.path();
+        ensure_runtime_dir(sessions_dir, "work").unwrap();
+
+        save_screen(sessions_dir, "work", 80, 24, 10, b"new-screen").unwrap();
+        save_screen(sessions_dir, "work", 80, 24, 9, b"old-screen").unwrap();
+
+        let loaded = load_screen(sessions_dir, "work").expect("screen restored");
+        assert_eq!(loaded.output_seq, 10);
+        assert_eq!(loaded.snapshot, b"new-screen");
+    }
+
     #[test]
     fn load_screen_absent_is_none() {
         let tmp = tempfile::tempdir().unwrap();

src/protocol.rs

@@ -5,10 +5,11 @@ 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
+/// Generate a name for an implicit terminal session: the kind created by
-/// created by `dosh host` with no `--session`. Single source of truth shared by
+/// `dosh host` with no `--session`. Single source of truth shared by the client
-/// the client (which generates it) and the server (which recognizes it via
+/// (which generates it) and the server (which recognizes it via
-/// [`is_implicit_session_name`] to decide a session is NOT worth persisting).
+/// [`is_implicit_session_name`] to apply shorter cleanup grace than named
+/// sessions).
 pub fn generate_implicit_session_name() -> String {
     let millis = SystemTime::now()
         .duration_since(UNIX_EPOCH)
@@ -18,9 +19,9 @@ pub fn generate_implicit_session_name() -> String {
 }
 
 /// Whether `name` is a client-generated implicit session name
-/// (`term-<digits>-<digits>`). Such sessions are ephemeral: the user can never
+/// (`term-<digits>-<digits>`). Such sessions are update-survivable while the
-/// reattach by name, so the server must not persist them across restarts.
+/// original client can reconnect with its ticket, but they are reaped sooner
-/// Explicitly-named (`--session work`) and prewarmed sessions are not implicit.
+/// than explicitly-named sessions once no clients remain.
 pub fn is_implicit_session_name(name: &str) -> bool {
     let Some(rest) = name.strip_prefix("term-") else {
         return false;
@@ -272,6 +273,9 @@ pub fn decode(input: &[u8]) -> Result<Packet> {
     if input.len() < end {
         bail!("truncated packet body");
     }
+    if input.len() > end {
+        bail!("trailing packet bytes");
+    }
     Ok(Packet {
         header,
         body: input[HEADER_LEN..end].to_vec(),
@@ -280,7 +284,7 @@ pub fn decode(input: &[u8]) -> Result<Packet> {
 
 pub fn decrypt_body(packet: &Packet, key: &[u8; 32], direction: u32) -> Result<Vec<u8>> {
     if packet.header.flags & 1 == 0 {
-        return Ok(packet.body.clone());
+        bail!("packet body is not encrypted");
     }
     let nonce = crypto::nonce_from(direction, packet.header.seq);
     let aad = packet.header.aad();

src/server.rs

@@ -10,9 +10,10 @@ use crate::protocol::{
     NativeServerHelloBody, NativeUserAuthBody, PacketKind, SERVER_TO_CLIENT,
 };
 use crate::transport::{
-    DoshTransport, SessionEvent, SessionRole, SessionTransportConfig, TransportConfig,
+    ADAPTIVE_RETRANSMIT_MIN, DoshTransport, SessionEvent, SessionRole, SessionTransportConfig,
-    service_name_from_target,
+    TransportConfig, service_name_from_target,
 };
+use crate::udp::{is_transient_udp_error, is_transient_udp_send_error};
 use anyhow::{Context, Result, anyhow, bail};
 use ed25519_dalek::SigningKey;
 use std::collections::{HashMap, HashSet};
@@ -97,6 +98,7 @@ pub enum DoshServerEvent {
     Ignored,
 }
 
+#[derive(Debug, Clone)]
 struct PendingServerAuth {
     client: native::NativeClientHello,
     server: NativeServerHello,
@@ -167,29 +169,52 @@ impl DoshServer {
         let mut buf = vec![0u8; 65535];
         loop {
             self.expire_pending();
-            let (n, peer) = self.socket.recv_from(&mut buf).await?;
+            let (n, peer) = match tokio::time::timeout(
-            let packet = match protocol::decode(&buf[..n]) {
+                ADAPTIVE_RETRANSMIT_MIN,
+                self.socket.recv_from(&mut buf),
+            )
+            .await
+            {
+                Ok(Ok(value)) => value,
+                Ok(Err(err)) if is_transient_udp_error(&err) => continue,
+                Ok(Err(err)) => return Err(err.into()),
+                Err(_) => {
+                    self.maintenance().await?;
+                    continue;
+                }
+            };
+            if let Some(event) = self.handle_datagram(peer, &buf[..n]).await? {
+                return Ok(event);
+            }
+        }
+    }
+
+    async fn handle_datagram(
+        &mut self,
+        peer: SocketAddr,
+        datagram: &[u8],
+    ) -> Result<Option<DoshServerEvent>> {
+        let packet = match protocol::decode(datagram) {
             Ok(packet) => packet,
-                Err(_) => continue,
+            Err(_) => return Ok(None),
         };
         if packet.header.kind == PacketKind::NativeClientHello {
             self.handle_client_hello(peer, packet.body).await?;
-                return Ok(DoshServerEvent::Ignored);
+            return Ok(Some(DoshServerEvent::Ignored));
         }
         if packet.header.kind == PacketKind::NativeUserAuth {
-                return self.handle_user_auth(peer, &packet).await;
+            return self.handle_user_auth(peer, &packet).await.map(Some);
         }
         if let Some(transport) = self.transports.get_mut(&packet.header.conn_id) {
-                let event = transport.handle_datagram(&buf[..n], peer).await?;
+            let event = transport.handle_datagram(datagram, peer).await?;
-                return Ok(DoshServerEvent::Session {
+            return Ok(Some(DoshServerEvent::Session {
                 conn_id: packet.header.conn_id,
                 event,
-                });
+            }));
         }
         self.send_reject(peer, packet.header.conn_id, "unknown Dosh connection")
             .await?;
-            return Ok(DoshServerEvent::Ignored);
+        Ok(Some(DoshServerEvent::Ignored))
-        }
     }
 
     pub async fn accept_stream(&mut self, conn_id: [u8; 16], stream_id: u64) -> Result<()> {
@@ -255,7 +280,7 @@ impl DoshServer {
         };
         let body = protocol::to_body(&NativeServerHelloBody { hello })?;
         let out = protocol::encode_plain(PacketKind::NativeServerHello, pending_id, 1, 0, &body)?;
-        self.socket.send_to(&out, peer).await?;
+        let _ = send_udp(&self.socket, &out, peer).await?;
         Ok(())
     }
 
@@ -327,7 +352,7 @@ impl DoshServer {
         peer: SocketAddr,
         packet: &protocol::Packet,
     ) -> Result<DoshServerEvent> {
-        let Some(pending) = self.pending.remove(&packet.header.conn_id) else {
+        let Some(pending) = self.pending.get(&packet.header.conn_id).cloned() else {
             self.send_reject(peer, packet.header.conn_id, "unknown native auth")
                 .await?;
             return Ok(DoshServerEvent::Ignored);
@@ -338,13 +363,28 @@ impl DoshServer {
             return Ok(DoshServerEvent::Ignored);
         }
         if pending.created_at.elapsed() > self.config.auth_timeout {
+            self.pending.remove(&packet.header.conn_id);
             self.send_reject(peer, packet.header.conn_id, "native auth expired")
                 .await?;
             return Ok(DoshServerEvent::Ignored);
         }
 
-        let body = protocol::decrypt_body(packet, &pending.session_key, CLIENT_TO_SERVER)?;
+        let body = match protocol::decrypt_body(packet, &pending.session_key, CLIENT_TO_SERVER) {
-        let req: NativeUserAuthBody = protocol::from_body(&body)?;
+            Ok(body) => body,
+            Err(_) => {
+                self.send_reject(peer, packet.header.conn_id, "native auth decrypt failed")
+                    .await?;
+                return Ok(DoshServerEvent::Ignored);
+            }
+        };
+        let req: NativeUserAuthBody = match protocol::from_body(&body) {
+            Ok(req) => req,
+            Err(_) => {
+                self.send_reject(peer, packet.header.conn_id, "invalid native auth body")
+                    .await?;
+                return Ok(DoshServerEvent::Ignored);
+            }
+        };
         let services = match self.verify_auth_and_services(&pending, &req.auth) {
             Ok(services) => services,
             Err(err) => {
@@ -353,6 +393,7 @@ impl DoshServer {
                 return Ok(DoshServerEvent::Ignored);
             }
         };
+        self.pending.remove(&packet.header.conn_id);
 
         let conn_id = crypto::random_16();
         let key_id = protocol::session_key_id(&pending.session_key);
@@ -381,7 +422,7 @@ impl DoshServer {
             SERVER_TO_CLIENT,
             &body,
         )?;
-        self.socket.send_to(&out, peer).await?;
+        let _ = send_udp(&self.socket, &out, peer).await?;
 
         let transport = DoshTransport::new(
             Arc::clone(&self.socket),
@@ -428,7 +469,7 @@ impl DoshServer {
             reason: reason.to_string(),
         })?;
         let out = protocol::encode_plain(PacketKind::AttachReject, conn_id, 0, 0, &body)?;
-        self.socket.send_to(&out, peer).await?;
+        let _ = send_udp(&self.socket, &out, peer).await?;
         Ok(())
     }
 
@@ -439,6 +480,14 @@ impl DoshServer {
     }
 }
 
+async fn send_udp(socket: &UdpSocket, packet: &[u8], peer: SocketAddr) -> Result<bool> {
+    match socket.send_to(packet, peer).await {
+        Ok(_) => Ok(true),
+        Err(err) if is_transient_udp_send_error(&err) => Ok(false),
+        Err(err) => Err(err).with_context(|| format!("send UDP packet to {peer}")),
+    }
+}
+
 fn validate_requested_services(
     allowed_services: &HashSet<String>,
     requests: &[ForwardingRequest],
@@ -477,6 +526,7 @@ mod tests {
     use super::*;
     use crate::client::DoshClient;
     use crate::config::{ClientConfig, HostsConfig};
+    use crate::protocol::{CLIENT_TO_SERVER, NativeUserAuthBody};
     use crate::transport::TransportEvent;
     use ed25519_dalek::SigningKey;
 
@@ -588,4 +638,170 @@ mod tests {
             }
         }
     }
+
+    #[tokio::test]
+    async fn sdk_server_recv_drives_transport_maintenance_while_idle() {
+        let dir = tempfile::tempdir().unwrap();
+        let host_key = dir.path().join("host_key");
+        let authorized_keys = dir.path().join("authorized_keys");
+        let signing = SigningKey::from_bytes(&[94u8; 32]);
+        let keypair = ssh_key::private::Ed25519Keypair::from(&signing);
+        let private =
+            ssh_key::PrivateKey::new(ssh_key::private::KeypairData::from(keypair), "").unwrap();
+        std::fs::write(
+            &authorized_keys,
+            format!("{}\n", private.public_key().to_openssh().unwrap()),
+        )
+        .unwrap();
+
+        let server_config = ServerConfig {
+            host_key: host_key.to_string_lossy().to_string(),
+            authorized_keys: vec![authorized_keys.to_string_lossy().to_string()],
+            ..ServerConfig::default()
+        };
+        let server_config = DoshServerConfig::new(server_config)
+            .bind_addr("127.0.0.1:0".parse().unwrap())
+            .service("echo")
+            .unwrap()
+            .require_current_user(false)
+            .transport(TransportConfig {
+                retransmit_after: Duration::from_millis(20),
+                keepalive_after: Duration::from_secs(60),
+                ..TransportConfig::default()
+            });
+        let mut server = DoshServer::bind(server_config).await.unwrap();
+        let client_socket = UdpSocket::bind("127.0.0.1:0").await.unwrap();
+        let client_addr = client_socket.local_addr().unwrap();
+        let conn_id = [95u8; 16];
+        let session_key = [96u8; 32];
+        let transport = DoshTransport::new(
+            Arc::clone(&server.socket),
+            SessionTransportConfig {
+                role: SessionRole::Server,
+                conn_id,
+                session_key,
+                peer_addr: client_addr,
+                initial_send_seq: 1,
+                initial_ack: 0,
+                stream: server.config.transport.clone(),
+            },
+        );
+        server.transports.insert(conn_id, transport);
+        server
+            .transport_mut(&conn_id)
+            .unwrap()
+            .open_service("echo")
+            .await
+            .unwrap();
+
+        let mut buf = [0u8; 65535];
+        tokio::time::timeout(
+            Duration::from_millis(200),
+            client_socket.recv_from(&mut buf),
+        )
+        .await
+        .unwrap()
+        .unwrap();
+
+        let recv_task = tokio::spawn(async move { server.recv().await });
+        let (n, _) =
+            tokio::time::timeout(Duration::from_secs(1), client_socket.recv_from(&mut buf))
+                .await
+                .unwrap()
+                .unwrap();
+        recv_task.abort();
+
+        let packet = protocol::decode(&buf[..n]).unwrap();
+        assert_eq!(packet.header.kind, PacketKind::StreamOpen);
+        let plain = protocol::decrypt_body(&packet, &session_key, SERVER_TO_CLIENT).unwrap();
+        let open: protocol::StreamOpen = protocol::from_body(&plain).unwrap();
+        assert_eq!(open.target_host, "@dosh-echo");
+    }
+
+    #[tokio::test]
+    async fn bad_native_auth_does_not_consume_pending_challenge() {
+        let dir = tempfile::tempdir().unwrap();
+        let host_key = dir.path().join("host_key");
+        let authorized_keys = dir.path().join("authorized_keys");
+        let signing = SigningKey::from_bytes(&[93u8; 32]);
+        let keypair = ssh_key::private::Ed25519Keypair::from(&signing);
+        let private =
+            ssh_key::PrivateKey::new(ssh_key::private::KeypairData::from(keypair), "").unwrap();
+        std::fs::write(
+            &authorized_keys,
+            format!("{}\n", private.public_key().to_openssh().unwrap()),
+        )
+        .unwrap();
+
+        let server_config = ServerConfig {
+            host_key: host_key.to_string_lossy().to_string(),
+            authorized_keys: vec![authorized_keys.to_string_lossy().to_string()],
+            ..ServerConfig::default()
+        };
+        let server_config = DoshServerConfig::new(server_config)
+            .bind_addr("127.0.0.1:0".parse().unwrap())
+            .require_current_user(false);
+        let mut server = DoshServer::bind(server_config).await.unwrap();
+        let peer: SocketAddr = "127.0.0.1:9".parse().unwrap();
+        let (client_secret, client_public) = native::generate_native_ephemeral();
+        let hello = native::NativeClientHello {
+            protocol_version: native::NATIVE_PROTOCOL_VERSION,
+            client_random: crypto::random_32(),
+            client_ephemeral_public: client_public,
+            requested_host: "127.0.0.1".to_string(),
+            requested_user: "sdk-user".to_string(),
+            requested_session: "test".to_string(),
+            requested_mode: "forward-only".to_string(),
+            terminal_size: (80, 24),
+            supported_aead: vec!["chacha20poly1305".to_string()],
+            supported_user_key_algorithms: vec!["ssh-ed25519".to_string()],
+            cached_host_key_fingerprint: None,
+            attach_ticket_envelope: None,
+            requested_env: Vec::new(),
+        };
+        let (pending_id, server_hello) = server.build_server_hello(hello.clone(), peer).unwrap();
+        let session_key = native::derive_native_session_key(
+            &client_secret,
+            server_hello.server_ephemeral_public,
+            &hello,
+            &server_hello,
+        )
+        .unwrap();
+        let auth = native::sign_user_auth(&signing, &hello, &server_hello, Vec::new()).unwrap();
+        let body = protocol::to_body(&NativeUserAuthBody { auth }).unwrap();
+        let bad = protocol::encode_encrypted(
+            PacketKind::NativeUserAuth,
+            pending_id,
+            2,
+            1,
+            &[7u8; 32],
+            CLIENT_TO_SERVER,
+            &body,
+        )
+        .unwrap();
+        let bad = protocol::decode(&bad).unwrap();
+
+        assert!(matches!(
+            server.handle_user_auth(peer, &bad).await.unwrap(),
+            DoshServerEvent::Ignored
+        ));
+        assert!(server.pending.contains_key(&pending_id));
+
+        let valid = protocol::encode_encrypted(
+            PacketKind::NativeUserAuth,
+            pending_id,
+            2,
+            1,
+            &session_key,
+            CLIENT_TO_SERVER,
+            &body,
+        )
+        .unwrap();
+        let valid = protocol::decode(&valid).unwrap();
+        assert!(matches!(
+            server.handle_user_auth(peer, &valid).await.unwrap(),
+            DoshServerEvent::Accepted(_)
+        ));
+        assert!(!server.pending.contains_key(&pending_id));
+    }
 }

src/trace.rs

@@ -0,0 +1,223 @@
+use std::fs::{File, OpenOptions};
+use std::io::Write;
+use std::path::{Path, PathBuf};
+use std::sync::{Mutex, OnceLock};
+use std::time::{SystemTime, UNIX_EPOCH};
+
+static TRACE_FILE: OnceLock<Option<Mutex<File>>> = OnceLock::new();
+static HEALTH_FILE: OnceLock<Option<Mutex<File>>> = OnceLock::new();
+static TRACE_BYTES: OnceLock<bool> = OnceLock::new();
+const HEALTH_LOG_MAX_BYTES: u64 = 1024 * 1024;
+
+pub fn enabled() -> bool {
+    TRACE_FILE.get_or_init(open_trace_file).is_some()
+}
+
+pub fn bytes_enabled() -> bool {
+    *TRACE_BYTES.get_or_init(|| truthy_env("DOSH_TRACE_BYTES"))
+}
+
+pub fn event(name: &str, fields: &[(&str, String)]) {
+    let Some(file) = TRACE_FILE.get_or_init(open_trace_file) else {
+        return;
+    };
+    write_event(file, name, fields);
+}
+
+pub fn health_event(name: &str, fields: &[(&str, String)]) {
+    let Some(file) = HEALTH_FILE.get_or_init(open_health_file) else {
+        return;
+    };
+    write_event(file, name, fields);
+}
+
+pub fn default_health_log_path() -> PathBuf {
+    trace_root().join("health.log")
+}
+
+fn write_event(file: &Mutex<File>, name: &str, fields: &[(&str, String)]) {
+    let now = SystemTime::now()
+        .duration_since(UNIX_EPOCH)
+        .map(|duration| duration.as_millis())
+        .unwrap_or(0);
+    let mut line = format!(
+        "ts_ms={} pid={} event={}",
+        now,
+        std::process::id(),
+        shell_escape(name)
+    );
+    for (key, value) in fields {
+        line.push(' ');
+        line.push_str(key);
+        line.push('=');
+        line.push_str(&shell_escape(value));
+    }
+    line.push('\n');
+    if let Ok(mut file) = file.lock() {
+        let _ = file.write_all(line.as_bytes());
+        let _ = file.flush();
+    }
+}
+
+pub fn bytes_summary(bytes: &[u8]) -> String {
+    let mut parts = vec![
+        format!("len={}", bytes.len()),
+        format!(
+            "esc={}",
+            contains_byte(bytes, 0x1b) || contains_byte(bytes, 0x9b)
+        ),
+        format!("focus={}", has_focus_report(bytes)),
+        format!("mouseish={}", looks_mouseish(bytes)),
+        format!("printable={}", printable_count(bytes)),
+    ];
+    if bytes_enabled() {
+        parts.push(format!("hex={}", hex_prefix(bytes, 160)));
+    }
+    parts.join(",")
+}
+
+fn open_trace_file() -> Option<Mutex<File>> {
+    let raw = std::env::var_os("DOSH_TRACE")?;
+    let normalized = raw.to_string_lossy().to_ascii_lowercase();
+    if normalized.is_empty() || matches!(normalized.as_str(), "0" | "false" | "off") {
+        return None;
+    }
+    let path = if matches!(normalized.as_str(), "1" | "true" | "on") {
+        default_trace_path()
+    } else {
+        PathBuf::from(raw)
+    };
+    if let Some(parent) = path.parent() {
+        let _ = std::fs::create_dir_all(parent);
+    }
+    OpenOptions::new()
+        .create(true)
+        .append(true)
+        .open(&path)
+        .ok()
+        .map(Mutex::new)
+}
+
+fn open_health_file() -> Option<Mutex<File>> {
+    let path = health_log_path_from_env()?;
+    rotate_health_log_if_needed(&path);
+    if let Some(parent) = path.parent() {
+        let _ = std::fs::create_dir_all(parent);
+    }
+    OpenOptions::new()
+        .create(true)
+        .append(true)
+        .open(&path)
+        .ok()
+        .map(Mutex::new)
+}
+
+fn health_log_path_from_env() -> Option<PathBuf> {
+    match std::env::var_os("DOSH_HEALTH_LOG") {
+        Some(raw) => {
+            let normalized = raw.to_string_lossy().to_ascii_lowercase();
+            if normalized.is_empty() || matches!(normalized.as_str(), "0" | "false" | "off") {
+                None
+            } else if matches!(normalized.as_str(), "1" | "true" | "on") {
+                Some(default_health_log_path())
+            } else {
+                Some(PathBuf::from(raw))
+            }
+        }
+        None => Some(default_health_log_path()),
+    }
+}
+
+fn rotate_health_log_if_needed(path: &Path) {
+    let Ok(metadata) = std::fs::metadata(path) else {
+        return;
+    };
+    if metadata.len() <= HEALTH_LOG_MAX_BYTES {
+        return;
+    }
+    let rotated = path.with_extension("log.1");
+    let _ = std::fs::remove_file(&rotated);
+    let _ = std::fs::rename(path, rotated);
+}
+
+fn default_trace_path() -> PathBuf {
+    let exe = std::env::current_exe()
+        .ok()
+        .and_then(|path| {
+            path.file_stem()
+                .map(|stem| stem.to_string_lossy().to_string())
+        })
+        .unwrap_or_else(|| "dosh".to_string());
+    trace_root().join(format!("{}-{}.log", exe, std::process::id()))
+}
+
+fn trace_root() -> PathBuf {
+    dirs::cache_dir()
+        .unwrap_or_else(std::env::temp_dir)
+        .join("dosh")
+        .join("trace")
+}
+
+fn truthy_env(name: &str) -> bool {
+    std::env::var_os(name).is_some_and(|value| {
+        let normalized = value.to_string_lossy().to_ascii_lowercase();
+        !normalized.is_empty() && !matches!(normalized.as_str(), "0" | "false" | "off")
+    })
+}
+
+fn shell_escape(value: &str) -> String {
+    if value.bytes().all(|byte| {
+        byte.is_ascii_alphanumeric()
+            || matches!(byte, b'.' | b'-' | b'_' | b':' | b'/' | b',' | b'=')
+    }) {
+        return value.to_string();
+    }
+    let mut out = String::from("'");
+    for ch in value.chars() {
+        if ch == '\'' {
+            out.push_str("'\\''");
+        } else {
+            out.push(ch);
+        }
+    }
+    out.push('\'');
+    out
+}
+
+fn contains_byte(bytes: &[u8], needle: u8) -> bool {
+    bytes.contains(&needle)
+}
+
+fn has_focus_report(bytes: &[u8]) -> bool {
+    bytes
+        .windows(3)
+        .any(|window| matches!(window, b"\x1b[I" | b"\x1b[O"))
+        || bytes
+            .windows(2)
+            .any(|window| matches!(window, b"\x9bI" | b"\x9bO"))
+}
+
+fn looks_mouseish(bytes: &[u8]) -> bool {
+    bytes.windows(3).any(|window| window == b"\x1b[<")
+        || bytes.windows(2).any(|window| window == b"\x9b<")
+        || bytes.iter().filter(|byte| **byte == b';').take(3).count() >= 2
+}
+
+fn printable_count(bytes: &[u8]) -> usize {
+    bytes
+        .iter()
+        .filter(|byte| byte.is_ascii_graphic() || **byte == b' ')
+        .count()
+}
+
+fn hex_prefix(bytes: &[u8], max: usize) -> String {
+    let mut out = String::with_capacity(bytes.len().min(max) * 2);
+    for byte in bytes.iter().take(max) {
+        use std::fmt::Write as _;
+        let _ = write!(&mut out, "{byte:02x}");
+    }
+    if bytes.len() > max {
+        out.push_str("...");
+    }
+    out
+}

src/udp.rs

@@ -0,0 +1,190 @@
+//! UDP error classification shared by Dosh clients, servers, and embedders.
+
+use std::net::SocketAddr;
+use std::time::{Duration, Instant};
+use tokio::net::UdpSocket;
+
+pub fn is_transient_udp_error(err: &std::io::Error) -> bool {
+    matches!(
+        err.kind(),
+        std::io::ErrorKind::Interrupted
+            | std::io::ErrorKind::TimedOut
+            | std::io::ErrorKind::WouldBlock
+    ) || err.raw_os_error().is_some_and(is_transient_udp_os_error)
+}
+
+pub fn is_transient_udp_send_error(err: &std::io::Error) -> bool {
+    is_transient_udp_error(err)
+}
+
+pub async fn send_udp_retrying_transient(
+    socket: &UdpSocket,
+    packet: &[u8],
+    peer: SocketAddr,
+    wait: Duration,
+) -> std::io::Result<()> {
+    let deadline = Instant::now() + wait.max(Duration::from_millis(1));
+    loop {
+        match socket.send_to(packet, peer).await {
+            Ok(_) => return Ok(()),
+            Err(err) if is_transient_udp_send_error(&err) && Instant::now() < deadline => {
+                sleep_until_retry(deadline).await;
+            }
+            Err(err) => return Err(err),
+        }
+    }
+}
+
+pub async fn recv_udp_retrying_transient(
+    socket: &UdpSocket,
+    buf: &mut [u8],
+    wait: Duration,
+) -> std::io::Result<(usize, SocketAddr)> {
+    let deadline = Instant::now() + wait.max(Duration::from_millis(1));
+    loop {
+        let now = Instant::now();
+        if now >= deadline {
+            return Err(std::io::Error::from(std::io::ErrorKind::TimedOut));
+        }
+        match tokio::time::timeout(deadline - now, socket.recv_from(buf)).await {
+            Ok(Ok(value)) => return Ok(value),
+            Ok(Err(err)) if is_transient_udp_error(&err) && Instant::now() < deadline => {
+                sleep_until_retry(deadline).await;
+            }
+            Ok(Err(err)) => return Err(err),
+            Err(_) => return Err(std::io::Error::from(std::io::ErrorKind::TimedOut)),
+        }
+    }
+}
+
+async fn sleep_until_retry(deadline: Instant) {
+    let now = Instant::now();
+    if now >= deadline {
+        return;
+    }
+    tokio::time::sleep((deadline - now).min(Duration::from_millis(20))).await;
+}
+
+#[cfg(unix)]
+fn is_transient_udp_os_error(code: i32) -> bool {
+    matches!(
+        code,
+        libc::EADDRNOTAVAIL
+            | libc::ECONNREFUSED
+            | libc::ECONNRESET
+            | libc::EHOSTDOWN
+            | libc::EHOSTUNREACH
+            | libc::ENETDOWN
+            | libc::ENETRESET
+            | libc::ENETUNREACH
+            | libc::ETIMEDOUT
+    )
+}
+
+#[cfg(windows)]
+fn is_transient_udp_os_error(code: i32) -> bool {
+    matches!(
+        code,
+        10049  // WSAEADDRNOTAVAIL
+            | 10050 // WSAENETDOWN
+            | 10051 // WSAENETUNREACH
+            | 10052 // WSAENETRESET
+            | 10054 // WSAECONNRESET
+            | 10060 // WSAETIMEDOUT
+            | 10061 // WSAECONNREFUSED
+            | 10064 // WSAEHOSTDOWN
+            | 10065 // WSAEHOSTUNREACH
+    )
+}
+
+#[cfg(not(any(unix, windows)))]
+fn is_transient_udp_os_error(_code: i32) -> bool {
+    false
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{
+        is_transient_udp_error, is_transient_udp_send_error, recv_udp_retrying_transient,
+        send_udp_retrying_transient,
+    };
+    use std::time::Duration;
+    use tokio::net::UdpSocket;
+
+    #[test]
+    fn classifies_portable_transient_udp_errors() {
+        for kind in [
+            std::io::ErrorKind::Interrupted,
+            std::io::ErrorKind::TimedOut,
+            std::io::ErrorKind::WouldBlock,
+        ] {
+            let err = std::io::Error::from(kind);
+            assert!(is_transient_udp_error(&err));
+            assert!(is_transient_udp_send_error(&err));
+        }
+        let fatal = std::io::Error::from(std::io::ErrorKind::PermissionDenied);
+        assert!(!is_transient_udp_error(&fatal));
+        assert!(!is_transient_udp_send_error(&fatal));
+    }
+
+    #[tokio::test]
+    async fn retrying_udp_send_and_receive_round_trip() {
+        let receiver = UdpSocket::bind("127.0.0.1:0").await.unwrap();
+        let sender = UdpSocket::bind("127.0.0.1:0").await.unwrap();
+        let addr = receiver.local_addr().unwrap();
+
+        send_udp_retrying_transient(&sender, b"hello", addr, Duration::from_millis(50))
+            .await
+            .unwrap();
+        let mut buf = [0u8; 16];
+        let (n, peer) = recv_udp_retrying_transient(&receiver, &mut buf, Duration::from_millis(50))
+            .await
+            .unwrap();
+
+        assert_eq!(&buf[..n], b"hello");
+        assert_eq!(peer, sender.local_addr().unwrap());
+    }
+
+    #[tokio::test]
+    async fn retrying_udp_receive_times_out_cleanly() {
+        let receiver = UdpSocket::bind("127.0.0.1:0").await.unwrap();
+        let mut buf = [0u8; 16];
+        let err = recv_udp_retrying_transient(&receiver, &mut buf, Duration::from_millis(1))
+            .await
+            .unwrap_err();
+
+        assert_eq!(err.kind(), std::io::ErrorKind::TimedOut);
+    }
+
+    #[cfg(unix)]
+    #[test]
+    fn classifies_unix_network_churn_as_transient() {
+        for code in [
+            libc::EADDRNOTAVAIL,
+            libc::ECONNREFUSED,
+            libc::ECONNRESET,
+            libc::EHOSTDOWN,
+            libc::EHOSTUNREACH,
+            libc::ENETDOWN,
+            libc::ENETRESET,
+            libc::ENETUNREACH,
+            libc::ETIMEDOUT,
+        ] {
+            let err = std::io::Error::from_raw_os_error(code);
+            assert!(is_transient_udp_error(&err));
+            assert!(is_transient_udp_send_error(&err));
+        }
+    }
+
+    #[cfg(windows)]
+    #[test]
+    fn classifies_windows_network_churn_as_transient() {
+        for code in [
+            10049, 10050, 10051, 10052, 10054, 10060, 10061, 10064, 10065,
+        ] {
+            let err = std::io::Error::from_raw_os_error(code);
+            assert!(is_transient_udp_error(&err));
+            assert!(is_transient_udp_send_error(&err));
+        }
+    }
+}

tests/hostile_network.rs

@@ -29,7 +29,7 @@ use std::io::{Read, Write};
 use std::net::{SocketAddr, TcpListener, UdpSocket};
 use std::process::{Child, Command, Stdio};
 use std::sync::Arc;
-use std::sync::atomic::{AtomicBool, AtomicU64, Ordering};
+use std::sync::atomic::{AtomicBool, AtomicU32, AtomicU64, Ordering};
 use std::sync::mpsc::{Receiver, Sender, channel};
 use std::thread;
 use std::time::{Duration, Instant};
@@ -49,9 +49,20 @@ use ed25519_dalek::{SigningKey, VerifyingKey};
 use rand::rngs::StdRng;
 use rand::{Rng, SeedableRng};
 
+const TEST_UDP_PORT_START: u16 = 31_000;
+const TEST_UDP_PORT_END: u16 = 60_999;
+static NEXT_UDP_PORT: AtomicU32 = AtomicU32::new(TEST_UDP_PORT_START as u32);
+
 fn free_udp_port() -> u16 {
-    let socket = UdpSocket::bind("127.0.0.1:0").unwrap();
+    let span = u32::from(TEST_UDP_PORT_END - TEST_UDP_PORT_START) + 1;
-    socket.local_addr().unwrap().port()
+    for _ in TEST_UDP_PORT_START..=TEST_UDP_PORT_END {
+        let offset = NEXT_UDP_PORT.fetch_add(1, Ordering::SeqCst) % span;
+        let port = TEST_UDP_PORT_START + offset as u16;
+        if UdpSocket::bind(("127.0.0.1", port)).is_ok() {
+            return port;
+        }
+    }
+    panic!("no free UDP test port in {TEST_UDP_PORT_START}-{TEST_UDP_PORT_END}");
 }
 
 fn write_server_config(dir: &tempfile::TempDir, port: u16) -> std::path::PathBuf {

tests/integration_smoke.rs

@@ -3,9 +3,11 @@
 use std::fs;
 use std::io::{Read, Write};
 use std::net::{TcpListener, TcpStream, UdpSocket};
+use std::os::unix::fs::PermissionsExt;
 use std::os::unix::net::{UnixListener, UnixStream};
 use std::path::{Path, PathBuf};
 use std::process::{Child, Command, Stdio};
+use std::sync::atomic::{AtomicU32, Ordering};
 use std::sync::mpsc;
 use std::thread;
 use std::time::Duration;
@@ -18,18 +20,40 @@ use dosh::crypto;
 use dosh::native::{host_public_key, load_or_create_host_key, ssh_ed25519_public_blob, trust_host};
 use dosh::protocol::{
     self, AttachOk, AttachReject, BootstrapAttachRequest, CLIENT_TO_SERVER, Frame, Input,
-    PacketKind, Resize, ResumeRequest, SERVER_TO_CLIENT,
+    PacketKind, Resize, ResumeRequest, SERVER_TO_CLIENT, TicketAttachBody, TicketAttachEnvelope,
+    TicketAttachOkEnvelope,
 };
 use ed25519_dalek::{Signer, SigningKey, VerifyingKey};
 
+const TEST_PORT_START: u16 = 30_000;
+const TEST_PORT_END: u16 = 60_999;
+static NEXT_UDP_PORT: AtomicU32 = AtomicU32::new(TEST_PORT_START as u32);
+static NEXT_TCP_PORT: AtomicU32 = AtomicU32::new(TEST_PORT_START as u32);
+
+fn next_test_port(counter: &AtomicU32) -> u16 {
+    let span = u32::from(TEST_PORT_END - TEST_PORT_START) + 1;
+    let offset = counter.fetch_add(1, Ordering::SeqCst) % span;
+    TEST_PORT_START + offset as u16
+}
+
 fn free_udp_port() -> u16 {
-    let socket = UdpSocket::bind("127.0.0.1:0").unwrap();
+    for _ in TEST_PORT_START..=TEST_PORT_END {
-    socket.local_addr().unwrap().port()
+        let port = next_test_port(&NEXT_UDP_PORT);
+        if UdpSocket::bind(("127.0.0.1", port)).is_ok() {
+            return port;
+        }
+    }
+    panic!("no free UDP test port in {TEST_PORT_START}-{TEST_PORT_END}");
 }
 
 fn free_tcp_port() -> u16 {
-    let listener = TcpListener::bind("127.0.0.1:0").unwrap();
+    for _ in TEST_PORT_START..=TEST_PORT_END {
-    listener.local_addr().unwrap().port()
+        let port = next_test_port(&NEXT_TCP_PORT);
+        if TcpListener::bind(("127.0.0.1", port)).is_ok() {
+            return port;
+        }
+    }
+    panic!("no free TCP test port in {TEST_PORT_START}-{TEST_PORT_END}");
 }
 
 fn write_server_config(dir: &tempfile::TempDir, port: u16) -> std::path::PathBuf {
@@ -128,21 +152,41 @@ fn write_server_config_with_retransmit_window(
 }
 
 fn start_server(dir: &tempfile::TempDir, config: &std::path::Path) -> Child {
+    start_server_with_trace(dir, config, None)
+}
+
+fn start_server_with_trace(
+    dir: &tempfile::TempDir,
+    config: &std::path::Path,
+    trace: Option<&Path>,
+) -> Child {
     let server = env!("CARGO_BIN_EXE_dosh-server");
-    let child = Command::new(server)
+    let mut command = Command::new(server);
+    command
         .arg("serve")
         .arg("--config")
         .arg(config)
         .env("HOME", dir.path())
         .stdout(Stdio::null())
-        .stderr(Stdio::null())
+        .stderr(Stdio::null());
-        .spawn()
+    if let Some(trace) = trace {
-        .unwrap();
+        command.env("DOSH_TRACE", trace);
+    }
+    let child = command.spawn().unwrap();
     thread::sleep(Duration::from_millis(500));
     child
 }
 
 fn attach_once(dir: &tempfile::TempDir, port: u16, cache: bool) -> std::process::Output {
+    attach_once_with_trace(dir, port, cache, None)
+}
+
+fn attach_once_with_trace(
+    dir: &tempfile::TempDir,
+    port: u16,
+    cache: bool,
+    trace: Option<&Path>,
+) -> std::process::Output {
     let client = env!("CARGO_BIN_EXE_dosh-client");
     let mut cmd = Command::new(client);
     cmd.arg("--local-auth")
@@ -157,6 +201,9 @@ fn attach_once(dir: &tempfile::TempDir, port: u16, cache: bool) -> std::process:
     if !cache {
         cmd.arg("--no-cache");
     }
+    if let Some(trace) = trace {
+        cmd.env("DOSH_TRACE", trace);
+    }
     cmd.output().unwrap()
 }
 
@@ -530,6 +577,75 @@ fn direct_attach_session(
     (socket, bootstrap, ok)
 }
 
+fn ticket_attach_session(
+    socket: &UdpSocket,
+    port: u16,
+    bootstrap: &dosh::auth::BootstrapResponse,
+    session: &str,
+    mode: &str,
+) -> AttachOk {
+    let client_nonce = crypto::random_12();
+    let request_key = crypto::hkdf32(
+        &bootstrap.attach_ticket_psk,
+        &client_nonce,
+        b"dosh/ticket-attach-request/v1",
+    )
+    .unwrap();
+    let body = protocol::to_body(&TicketAttachBody {
+        session: session.to_string(),
+        mode: mode.to_string(),
+        cols: 80,
+        rows: 24,
+        requested_env: Vec::new(),
+    })
+    .unwrap();
+    let ciphertext = crypto::seal(
+        &request_key,
+        &client_nonce,
+        b"dosh-ticket-attach-request-v1",
+        &body,
+    )
+    .unwrap();
+    let envelope = TicketAttachEnvelope {
+        ticket: bootstrap.attach_ticket.clone(),
+        client_nonce,
+        ciphertext,
+    };
+    let packet = protocol::encode_plain(
+        PacketKind::TicketAttachRequest,
+        [0u8; 16],
+        1,
+        0,
+        &protocol::to_body(&envelope).unwrap(),
+    )
+    .unwrap();
+    socket
+        .send_to(&packet, format!("127.0.0.1:{port}"))
+        .unwrap();
+    let mut buf = [0u8; 65535];
+    let (n, _) = socket.recv_from(&mut buf).unwrap();
+    let packet = protocol::decode(&buf[..n]).unwrap();
+    assert_eq!(packet.header.kind, PacketKind::AttachOk);
+    let envelope: TicketAttachOkEnvelope = protocol::from_body(&packet.body).unwrap();
+    let mut salt = Vec::with_capacity(24);
+    salt.extend_from_slice(&client_nonce);
+    salt.extend_from_slice(&envelope.server_nonce);
+    let response_key = crypto::hkdf32(
+        &bootstrap.attach_ticket_psk,
+        &salt,
+        b"dosh/ticket-attach-ok/v1",
+    )
+    .unwrap();
+    let plain = crypto::open(
+        &response_key,
+        &envelope.server_nonce,
+        b"dosh-ticket-attach-ok-v1",
+        &envelope.ciphertext,
+    )
+    .unwrap();
+    protocol::from_body(&plain).unwrap()
+}
+
 #[allow(clippy::too_many_arguments)]
 fn send_encrypted(
     socket: &UdpSocket,
@@ -910,6 +1026,8 @@ fn native_file_copy_recursive_round_trip() {
     fs::create_dir_all(src.join("nested")).unwrap();
     fs::write(src.join("root.txt"), b"root file\n").unwrap();
     fs::write(src.join("nested/child.txt"), b"child file\n").unwrap();
+    std::os::unix::fs::symlink("root.txt", src.join("root-link")).unwrap();
+    std::os::unix::fs::symlink("nested/child.txt", src.join("child-link")).unwrap();
 
     let client_bin = env!("CARGO_BIN_EXE_dosh-client");
     let upload = Command::new(client_bin)
@@ -1015,6 +1133,14 @@ fn native_file_copy_recursive_round_trip() {
         fs::read_to_string(downloaded.join("nested/child.txt")).unwrap(),
         "child file\n"
     );
+    assert_eq!(
+        fs::read_link(downloaded.join("root-link")).unwrap(),
+        PathBuf::from("root.txt")
+    );
+    assert_eq!(
+        fs::read_link(downloaded.join("child-link")).unwrap(),
+        PathBuf::from("nested/child.txt")
+    );
 
     let remove = Command::new(client_bin)
         .arg("--dosh-host")
@@ -1038,6 +1164,191 @@ fn native_file_copy_recursive_round_trip() {
     let _ = server.wait();
 }
 
+#[test]
+fn native_file_copy_resume_truncates_oversized_destinations() {
+    let dir = tempfile::tempdir().unwrap();
+    let port = free_udp_port();
+    let config = write_server_config(&dir, port);
+    write_native_client_auth(&dir, &config);
+    let mut server = start_server(&dir, &config);
+    let client_bin = env!("CARGO_BIN_EXE_dosh-client");
+
+    let local_short = dir.path().join("short.txt");
+    fs::write(&local_short, b"short\n").unwrap();
+
+    let seed_remote = Command::new(client_bin)
+        .arg("--dosh-host")
+        .arg("127.0.0.1")
+        .arg("--dosh-port")
+        .arg(port.to_string())
+        .arg("exec")
+        .arg("local")
+        .arg("printf 'short\\nSTALE' > \"$HOME/resume-upload.txt\"")
+        .env("HOME", dir.path())
+        .output()
+        .unwrap();
+    assert!(
+        seed_remote.status.success(),
+        "seed remote failed: stdout={} stderr={}",
+        String::from_utf8_lossy(&seed_remote.stdout),
+        String::from_utf8_lossy(&seed_remote.stderr)
+    );
+
+    let resume_upload = Command::new(client_bin)
+        .arg("--dosh-host")
+        .arg("127.0.0.1")
+        .arg("--dosh-port")
+        .arg(port.to_string())
+        .arg("cp")
+        .arg("--resume")
+        .arg(&local_short)
+        .arg("local:resume-upload.txt")
+        .env("HOME", dir.path())
+        .output()
+        .unwrap();
+    assert!(
+        resume_upload.status.success(),
+        "resume upload failed: stdout={} stderr={}",
+        String::from_utf8_lossy(&resume_upload.stdout),
+        String::from_utf8_lossy(&resume_upload.stderr)
+    );
+
+    let cat_upload = Command::new(client_bin)
+        .arg("--dosh-host")
+        .arg("127.0.0.1")
+        .arg("--dosh-port")
+        .arg(port.to_string())
+        .arg("cat")
+        .arg("local:resume-upload.txt")
+        .env("HOME", dir.path())
+        .output()
+        .unwrap();
+    assert!(
+        cat_upload.status.success(),
+        "cat upload failed: stdout={} stderr={}",
+        String::from_utf8_lossy(&cat_upload.stdout),
+        String::from_utf8_lossy(&cat_upload.stderr)
+    );
+    assert_eq!(String::from_utf8_lossy(&cat_upload.stdout), "short\n");
+
+    let seed_download = Command::new(client_bin)
+        .arg("--dosh-host")
+        .arg("127.0.0.1")
+        .arg("--dosh-port")
+        .arg(port.to_string())
+        .arg("exec")
+        .arg("local")
+        .arg("printf 'tiny\\n' > \"$HOME/resume-download.txt\"")
+        .env("HOME", dir.path())
+        .output()
+        .unwrap();
+    assert!(
+        seed_download.status.success(),
+        "seed download failed: stdout={} stderr={}",
+        String::from_utf8_lossy(&seed_download.stdout),
+        String::from_utf8_lossy(&seed_download.stderr)
+    );
+
+    let local_download = dir.path().join("resume-download-local.txt");
+    fs::write(&local_download, b"tiny\nSTALE").unwrap();
+    let resume_download = Command::new(client_bin)
+        .arg("--dosh-host")
+        .arg("127.0.0.1")
+        .arg("--dosh-port")
+        .arg(port.to_string())
+        .arg("cp")
+        .arg("--resume")
+        .arg("local:resume-download.txt")
+        .arg(&local_download)
+        .env("HOME", dir.path())
+        .output()
+        .unwrap();
+    assert!(
+        resume_download.status.success(),
+        "resume download failed: stdout={} stderr={}",
+        String::from_utf8_lossy(&resume_download.stdout),
+        String::from_utf8_lossy(&resume_download.stderr)
+    );
+    assert_eq!(fs::read_to_string(&local_download).unwrap(), "tiny\n");
+
+    let _ = server.kill();
+    let _ = server.wait();
+}
+
+#[test]
+fn native_file_copy_resume_prefix_mismatch_preserves_destinations() {
+    let dir = tempfile::tempdir().unwrap();
+    let port = free_udp_port();
+    let config = write_server_config(&dir, port);
+    write_native_client_auth(&dir, &config);
+    let mut server = start_server(&dir, &config);
+    let client_bin = env!("CARGO_BIN_EXE_dosh-client");
+
+    let local_upload = dir.path().join("upload-prefix.txt");
+    let remote_upload = dir.path().join("remote-upload.txt");
+    fs::write(&local_upload, b"local-prefix\n").unwrap();
+    fs::write(&remote_upload, b"remote-prefix-with-tail\n").unwrap();
+    fs::set_permissions(&local_upload, fs::Permissions::from_mode(0o755)).unwrap();
+    fs::set_permissions(&remote_upload, fs::Permissions::from_mode(0o600)).unwrap();
+
+    let bad_upload_resume = Command::new(client_bin)
+        .arg("--dosh-host")
+        .arg("127.0.0.1")
+        .arg("--dosh-port")
+        .arg(port.to_string())
+        .arg("cp")
+        .arg("--resume")
+        .arg(&local_upload)
+        .arg("local:remote-upload.txt")
+        .env("HOME", dir.path())
+        .output()
+        .unwrap();
+    assert!(
+        !bad_upload_resume.status.success(),
+        "bad upload resume unexpectedly succeeded: stdout={} stderr={}",
+        String::from_utf8_lossy(&bad_upload_resume.stdout),
+        String::from_utf8_lossy(&bad_upload_resume.stderr)
+    );
+    assert_eq!(
+        fs::read_to_string(&remote_upload).unwrap(),
+        "remote-prefix-with-tail\n"
+    );
+    assert_eq!(
+        fs::metadata(&remote_upload).unwrap().permissions().mode() & 0o777,
+        0o600
+    );
+
+    fs::write(dir.path().join("remote-download.txt"), b"remote-download\n").unwrap();
+    let local_download = dir.path().join("download-prefix.txt");
+    fs::write(&local_download, b"local-download-with-tail\n").unwrap();
+
+    let bad_download_resume = Command::new(client_bin)
+        .arg("--dosh-host")
+        .arg("127.0.0.1")
+        .arg("--dosh-port")
+        .arg(port.to_string())
+        .arg("cp")
+        .arg("--resume")
+        .arg("local:remote-download.txt")
+        .arg(&local_download)
+        .env("HOME", dir.path())
+        .output()
+        .unwrap();
+    assert!(
+        !bad_download_resume.status.success(),
+        "bad download resume unexpectedly succeeded: stdout={} stderr={}",
+        String::from_utf8_lossy(&bad_download_resume.stdout),
+        String::from_utf8_lossy(&bad_download_resume.stderr)
+    );
+    assert_eq!(
+        fs::read_to_string(&local_download).unwrap(),
+        "local-download-with-tail\n"
+    );
+
+    let _ = server.kill();
+    let _ = server.wait();
+}
+
 #[test]
 fn native_exec_command_smoke() {
     let dir = tempfile::tempdir().unwrap();
@@ -1276,7 +1587,9 @@ fn ticket_attach_after_server_restart_smoke() {
     let dir = tempfile::tempdir().unwrap();
     let port = free_udp_port();
     let config = write_server_config(&dir, port);
-    let mut server = start_server(&dir, &config);
+    let server_trace = dir.path().join("server-trace.log");
+    let client_trace = dir.path().join("client-trace.log");
+    let mut server = start_server_with_trace(&dir, &config, Some(&server_trace));
     let first = attach_once(&dir, port, true);
     let _ = server.kill();
     let _ = server.wait();
@@ -1286,8 +1599,8 @@ fn ticket_attach_after_server_restart_smoke() {
         String::from_utf8_lossy(&first.stderr)
     );
 
-    let mut server = start_server(&dir, &config);
+    let mut server = start_server_with_trace(&dir, &config, Some(&server_trace));
-    let second = attach_once(&dir, port, true);
+    let second = attach_once_with_trace(&dir, port, true, Some(&client_trace));
     let _ = server.kill();
     let _ = server.wait();
     let stderr = String::from_utf8_lossy(&second.stderr);
@@ -1296,6 +1609,24 @@ fn ticket_attach_after_server_restart_smoke() {
         stderr.contains("udp_ticket_attach_ready"),
         "stderr={stderr}"
     );
+    let server_trace = fs::read_to_string(&server_trace).unwrap();
+    let client_trace = fs::read_to_string(&client_trace).unwrap();
+    assert!(
+        server_trace.contains("event=server.ticket_attach_start"),
+        "server trace={server_trace}"
+    );
+    assert!(
+        server_trace.contains("event=server.ticket_attach_ok"),
+        "server trace={server_trace}"
+    );
+    assert!(
+        client_trace.contains("event=client.ticket_attach_start"),
+        "client trace={client_trace}"
+    );
+    assert!(
+        client_trace.contains("event=client.ticket_attach_ok"),
+        "client trace={client_trace}"
+    );
 }
 
 #[test]
@@ -2733,7 +3064,7 @@ fn session_survives_server_restart_same_shell_and_screen() {
 }
 
 #[test]
-fn implicit_session_does_not_create_restart_holder() {
+fn implicit_session_survives_update_restart_via_ticket_reattach() {
     let dir = tempfile::tempdir().unwrap();
     let sessions_dir = dir.path().join("sessions");
     let port = free_udp_port();
@@ -2743,21 +3074,34 @@ fn implicit_session_does_not_create_restart_holder() {
     let mut server = start_server(&dir, &config);
     let (socket, bootstrap, ok) = direct_attach_session(&config, port, "read-write", &session);
     let key = bootstrap.session_key;
+    type_line(&socket, port, &ok, &key, 2, "cd /tmp\n");
     type_line(
         &socket,
         port,
         &ok,
         &key,
-        2,
+        3,
         "export IMPLICIT_MARK=implicit_restart_42\n",
     );
-    let _ = collect_frame_text(&socket, &key, 1000);
+    type_line(
+        &socket,
+        port,
+        &ok,
+        &key,
+        4,
+        "printf 'IMPLICIT_SCREEN_MARKER\\n'\n",
+    );
+    let pre = collect_frame_text(&socket, &key, 1500);
+    assert!(
+        pre.contains("IMPLICIT_SCREEN_MARKER"),
+        "implicit marker missing before restart: {pre:?}"
+    );
     thread::sleep(Duration::from_secs(3));
 
     let shell_pid_before = holder_shell_pid(&sessions_dir, &session);
     assert!(
-        shell_pid_before.is_none(),
+        shell_pid_before.is_some(),
-        "implicit sessions must not get persistent holders when persistence is enabled"
+        "implicit sessions must get temporary holders so active clients survive updates"
     );
 
     let _ = server.kill();
@@ -2765,34 +3109,78 @@ fn implicit_session_does_not_create_restart_holder() {
     thread::sleep(Duration::from_millis(300));
 
     let mut server = start_server(&dir, &config);
-    let (socket2, bootstrap2, ok2) = direct_attach_session(&config, port, "read-write", &session);
+
-    let key2 = bootstrap2.session_key;
+    let resume = ResumeRequest {
+        session: session.clone(),
+        last_rendered_seq: ok.initial_seq,
+        cols: 80,
+        rows: 24,
+    };
+    send_encrypted(
+        &socket,
+        port,
+        PacketKind::ResumeRequest,
+        ok.client_id,
+        5,
+        0,
+        &key,
+        &protocol::to_body(&resume).unwrap(),
+    );
+    let mut buf = [0u8; 65535];
+    let deadline = std::time::Instant::now() + Duration::from_secs(2);
+    loop {
+        assert!(
+            std::time::Instant::now() < deadline,
+            "old live resume did not receive unknown-client reject"
+        );
+        let (n, _) = socket.recv_from(&mut buf).unwrap();
+        let packet = protocol::decode(&buf[..n]).unwrap();
+        if packet.header.kind == PacketKind::Frame {
+            continue;
+        }
+        assert_eq!(packet.header.kind, PacketKind::AttachReject);
+        assert_eq!(packet.header.conn_id, ok.client_id);
+        break;
+    }
+
+    let ok2 = ticket_attach_session(&socket, port, &bootstrap, &session, "read-write");
+    let key2 = ok2.session_key;
+    let snapshot = String::from_utf8_lossy(&ok2.snapshot).to_string();
     type_line(
-        &socket2,
+        &socket,
         port,
         &ok2,
         &key2,
         2,
-        "printf 'IMPLICIT_MARK=%s\\n' \"$IMPLICIT_MARK\"\n",
+        "printf 'IMPLICIT_MARK=%s PWD=%s\\n' \"$IMPLICIT_MARK\" \"$PWD\"\n",
     );
-    let post = collect_frame_text(&socket2, &key2, 2000);
+    let post = collect_frame_text(&socket, &key2, 2000);
     let shell_pid_after = holder_shell_pid(&sessions_dir, &session);
 
     let _ = server.kill();
     let _ = server.wait();
+    kill_holder(&sessions_dir, &session);
 
     assert!(
-        shell_pid_after.is_none(),
+        snapshot.contains("IMPLICIT_SCREEN_MARKER"),
-        "implicit restart attach must stay ephemeral"
+        "ticket reattach snapshot must repaint the exact pre-update screen, got {snapshot:?}"
+    );
+    assert_eq!(
+        shell_pid_after, shell_pid_before,
+        "implicit update reconnect must use the same holder shell"
     );
     assert!(
-        post.contains("IMPLICIT_MARK=") && !post.contains("implicit_restart_42"),
+        post.contains("IMPLICIT_MARK=implicit_restart_42"),
-        "implicit session must start fresh after server restart, got {post:?}"
+        "implicit session env must survive update reconnect, got {post:?}"
+    );
+    assert!(
+        post.contains("PWD=/tmp"),
+        "implicit session cwd must survive update reconnect, got {post:?}"
     );
 }
 
 #[test]
-fn startup_discards_legacy_implicit_holders() {
+fn startup_readopts_implicit_holders_for_update_reconnect() {
     let dir = tempfile::tempdir().unwrap();
     let sessions_dir = dir.path().join("sessions");
     let port = free_udp_port();
@@ -2812,13 +3200,14 @@ fn startup_discards_legacy_implicit_holders() {
     let _ = server.kill();
     let _ = server.wait();
     assert!(
-        holder_shell_pid(&sessions_dir, &session).is_none(),
+        holder_shell_pid(&sessions_dir, &session).is_some(),
-        "startup must remove old implicit holder metadata"
+        "startup must keep live implicit holders so active update reconnects can reattach"
     );
     assert!(
-        unsafe { libc::kill(shell_pid, 0) } != 0,
+        unsafe { libc::kill(shell_pid, 0) } == 0,
-        "startup must shut down old implicit holder shell"
+        "startup must not shut down a live implicit holder before reconnect grace"
     );
+    kill_holder(&sessions_dir, &session);
 }
 
 #[test]

tests/protocol_auth.rs

@@ -58,6 +58,34 @@ fn encrypted_packet_round_trips() {
     assert_eq!(plain, b"hello");
 }
 
+#[test]
+fn packet_decode_rejects_truncated_or_trailing_datagrams() {
+    let packet =
+        protocol::encode_plain(PacketKind::Ping, crypto::random_16(), 1, 0, b"hello").unwrap();
+
+    let truncated = &packet[..packet.len() - 1];
+    let err = protocol::decode(truncated).unwrap_err();
+    assert!(err.to_string().contains("truncated packet body"));
+
+    let mut trailing = packet.clone();
+    trailing.extend_from_slice(b"junk");
+    let err = protocol::decode(&trailing).unwrap_err();
+    assert!(err.to_string().contains("trailing packet bytes"));
+}
+
+#[test]
+fn plaintext_packet_never_decrypts_as_authenticated_body() {
+    let key = crypto::random_32();
+    let mut decoded = protocol::decode(
+        &protocol::encode_plain(PacketKind::Input, crypto::random_16(), 1, 0, b"hello").unwrap(),
+    )
+    .unwrap();
+    decoded.header.session_key_id = protocol::session_key_id(&key);
+
+    let err = protocol::decrypt_body(&decoded, &key, CLIENT_TO_SERVER).unwrap_err();
+    assert!(err.to_string().contains("not encrypted"));
+}
+
 #[test]
 fn encrypted_packet_rejects_wrong_session_key_id_before_decrypt() {
     let key = crypto::random_32();

tests/release_scripts.rs

@@ -19,6 +19,271 @@ fn release_scripts_skip_stale_artifacts_when_auto_discovering() {
     assert!(publish.contains("actual=\"$(artifact_version \"$artifact\" || true)\""));
 }
 
+#[test]
+fn release_upload_refuses_partial_platform_sets_by_default() {
+    let upload = include_str!("../scripts/upload-gitea-release.sh");
+    assert!(upload.contains("require_complete_release_artifacts \"$@\""));
+    assert!(upload.contains("DOSH_RELEASE_ALLOW_PARTIAL=1"));
+    assert!(upload.contains("refusing partial release upload"));
+    for name in [
+        "dosh-linux-x86_64.tar.gz",
+        "dosh-macos-aarch64.tar.gz",
+        "dosh-macos-x86_64.tar.gz",
+        "dosh-windows-x86_64.zip",
+    ] {
+        assert!(
+            upload.contains(name),
+            "release upload completeness check must require {name}"
+        );
+    }
+}
+
+#[test]
+fn release_upload_marks_prerelease_tags_as_prereleases() {
+    let upload = include_str!("../scripts/upload-gitea-release.sh");
+    assert!(upload.contains("release_prerelease=false"));
+    assert!(upload.contains("*-*) release_prerelease=true"));
+    assert!(upload.contains("\"prerelease\":%s"));
+    assert!(upload.contains("metadata_payload="));
+    assert!(
+        upload.contains("-X PATCH"),
+        "existing Gitea releases must be corrected when prerelease metadata changes"
+    );
+}
+
+#[test]
+fn release_gates_test_all_targets() {
+    let makefile = include_str!("../Makefile");
+    let ci = include_str!("../.github/workflows/ci.yml");
+    assert!(makefile.contains("test:\n\tcargo test --all-targets"));
+    assert!(makefile.contains("cargo test --all-targets\n\t$(MAKE) tui-harness"));
+    assert!(ci.contains("run: sh -n install.sh scripts/*.sh"));
+    assert!(ci.contains("run: cargo clippy --all-targets -- -D warnings"));
+    assert!(ci.contains("run: cargo test --all-targets"));
+    assert!(ci.contains("run: sh scripts/tui-harness.sh"));
+}
+
+#[test]
+fn one_dot_zero_gates_default_to_full_length_soaks() {
+    let makefile = include_str!("../Makefile");
+    let reconnect_check = makefile
+        .split("reconnect-check:")
+        .nth(1)
+        .and_then(|tail| tail.split("\nhostile-network-check:").next())
+        .expect("reconnect-check target");
+    assert!(reconnect_check.contains("DOSH_SOAK_SECONDS=$${DOSH_SOAK_SECONDS:-1800}"));
+    assert!(!reconnect_check.contains("DOSH_SOAK_SECONDS=$${DOSH_SOAK_SECONDS:-300}"));
+
+    let hostile_check = makefile
+        .split("hostile-network-check:")
+        .nth(1)
+        .and_then(|tail| tail.split("\npersistence-check:").next())
+        .expect("hostile-network-check target");
+    assert!(hostile_check.contains("DOSH_BADNET_SOAK_SECONDS=$${DOSH_BADNET_SOAK_SECONDS:-1800}"));
+    assert!(!hostile_check.contains("DOSH_BADNET_SOAK_SECONDS=$${DOSH_BADNET_SOAK_SECONDS:-300}"));
+}
+
+#[test]
+fn installers_skip_stale_latest_release_prebuilts() {
+    let install = include_str!("../install.sh");
+    assert!(install.contains("latest_release_is_stale"));
+    assert!(install.contains("current_source_version"));
+    assert!(install.contains("latest release $latest is older than source $current"));
+    assert!(install.contains("version_prerelease"));
+    assert!(install.contains("prerelease_less_than"));
+    assert!(
+        install.contains("if latest_release_is_stale; then"),
+        "unix installer must skip stale latest before downloading a prebuilt"
+    );
+
+    let ps1 = include_str!("../install.ps1");
+    assert!(ps1.contains("Latest-ReleaseIsStale"));
+    assert!(ps1.contains("Current-SourceVersion"));
+    assert!(ps1.contains("latest release $latestVersion is older than source $current"));
+    assert!(ps1.contains("Version-Prerelease"));
+    assert!(ps1.contains("Compare-Prerelease"));
+    assert!(
+        ps1.contains("if (Latest-ReleaseIsStale)"),
+        "windows installer must skip stale latest before downloading a prebuilt"
+    );
+}
+
+#[test]
+fn installers_refuse_prebuilts_without_checksums() {
+    let install = include_str!("../install.sh");
+    assert!(install.contains("verify_archive_checksum"));
+    assert!(install.contains("refusing unverified binary for $url"));
+    assert!(
+        !install.contains("continuing without sidecar verification"),
+        "unix installer must not silently install an unverifiable prebuilt"
+    );
+
+    let ps1 = include_str!("../install.ps1");
+    assert!(ps1.contains("Verify-ArchiveChecksum"));
+    assert!(ps1.contains("refusing unverified binary for $Url"));
+    assert!(
+        !ps1.contains("continuing without sidecar verification"),
+        "windows installer must not silently install an unverifiable prebuilt"
+    );
+}
+
+#[test]
+fn windows_installer_reuses_persistent_source_update_cache() {
+    let ps1 = include_str!("../install.ps1");
+    assert!(ps1.contains("DOSH_UPDATE_CACHE"));
+    assert!(ps1.contains("Assert-NoRelativePathSegments($Path)"));
+    assert!(ps1.contains("Assert-NoRelativePathSegments $Path"));
+    assert!(ps1.contains("$segment -eq \".\" -or $segment -eq \"..\""));
+    assert!(ps1.contains("$sourceCache = Assert-SafeUpdateCache $UpdateCache"));
+    assert!(ps1.contains("git -C $sourceCache fetch --depth 1 origin main"));
+    assert!(ps1.contains("git -C $sourceCache checkout -q -B main FETCH_HEAD"));
+    assert!(ps1.contains("git clone --depth 1 --branch main $Repo $sourceCache"));
+    assert!(
+        !ps1.contains("git clone --depth 1 $Repo $tmp"),
+        "Windows source updates should reuse a persistent cache instead of recloning into temp"
+    );
+}
+
+#[test]
+fn unix_installer_rejects_unsafe_source_update_cache_paths() {
+    let install = include_str!("../install.sh");
+    assert!(install.contains("normalize_update_cache_path()"));
+    assert!(install.contains("safe_update_cache_path()"));
+    assert!(install.contains("update_cache=\"$(safe_update_cache_path \"$update_cache\")\""));
+    for pattern in [
+        "\"\"|\"/\"|\"$home_norm\"|\"$home_cache_norm\"",
+        "\".\"|\"..\"|./*|../*|*/.|*/..|*/./*|*/../*",
+    ] {
+        assert!(
+            install.contains(pattern),
+            "Unix installer must reject unsafe update cache pattern {pattern}"
+        );
+    }
+    assert!(
+        install.contains("rm -rf \"$update_cache\""),
+        "source cache replacement remains the destructive operation guarded by safe_update_cache_path"
+    );
+}
+
+#[test]
+fn installers_generate_same_native_auth_client_defaults() {
+    let install = include_str!("../install.sh");
+    let ps1 = include_str!("../install.ps1");
+    for setting in [
+        "auth_preference = \"native,ssh\"",
+        "trust_on_first_use = false",
+        "native_auth_timeout_ms = 700",
+        "known_hosts = \"~/.config/dosh/known_hosts\"",
+        "identity_files = [\"~/.ssh/id_ed25519\"]",
+        "use_ssh_agent = true",
+        "forward_agent = false",
+    ] {
+        assert!(
+            install.contains(setting),
+            "Unix installer missing client default {setting}"
+        );
+        assert!(
+            ps1.contains(setting),
+            "Windows installer missing client default {setting}"
+        );
+    }
+}
+
+#[test]
+fn windows_installer_generates_hosts_config_like_unix() {
+    let install = include_str!("../install.sh");
+    let ps1 = include_str!("../install.ps1");
+    for setting in [
+        "hosts.toml",
+        "# default_command = \"tm\"",
+        "[default]",
+        "predict = true",
+    ] {
+        assert!(
+            install.contains(setting),
+            "Unix installer missing host config setting {setting}"
+        );
+        assert!(
+            ps1.contains(setting),
+            "Windows installer missing host config setting {setting}"
+        );
+    }
+    assert!(ps1.contains("$hostUdp = if ($DoshHost) { $DoshHost } else { $defaultServer }"));
+    assert!(ps1.contains("Set-Content -NoNewline -Encoding utf8 $hostsConfig"));
+}
+
+#[test]
+fn package_check_verifies_only_artifacts_it_builds() {
+    let makefile = include_str!("../Makefile");
+    let verify = include_str!("../scripts/verify-release-artifacts.sh");
+    assert!(
+        verify.contains("if [ \"$#\" -gt 0 ]; then"),
+        "release verifier must accept an explicit artifact list"
+    );
+    let package_check = makefile
+        .split("package-check:")
+        .nth(1)
+        .and_then(|tail| tail.split("\ninstall:").next())
+        .expect("package-check target");
+    assert!(package_check.contains("package-release-linux"));
+    assert!(package_check.contains("package-release-windows"));
+    assert!(package_check.contains("dosh-linux-x86_64.tar.gz"));
+    assert!(package_check.contains("dosh-windows-x86_64.zip"));
+    assert!(
+        !package_check.contains("dosh-macos-aarch64.tar.gz"),
+        "Linux package-check does not build macOS artifacts, so it must not depend on one"
+    );
+}
+
+#[test]
+fn complete_release_verifier_requires_both_macos_architectures() {
+    let verify = include_str!("../scripts/verify-release-artifacts.sh");
+    assert!(verify.contains("dosh-linux-x86_64.tar.gz"));
+    assert!(verify.contains("dosh-macos-aarch64.tar.gz"));
+    assert!(verify.contains("dosh-macos-x86_64.tar.gz"));
+    assert!(verify.contains("dosh-windows-x86_64.zip"));
+}
+
+#[test]
+fn release_verifier_checks_checksums_and_expected_binaries() {
+    let verify = include_str!("../scripts/verify-release-artifacts.sh");
+    assert!(verify.contains("verify_checksum()"));
+    assert!(verify.contains("release checksum mismatch"));
+    for member in [
+        "dosh/bin/dosh",
+        "dosh/bin/dosh-client",
+        "dosh/bin/dosh-server",
+        "dosh/bin/dosh-auth",
+        "dosh/bin/dosh-bench",
+        "dosh/bin/dosh.exe",
+        "dosh/bin/dosh-client.exe",
+        "dosh/bin/dosh-bench.exe",
+    ] {
+        assert!(
+            verify.contains(member),
+            "release verifier must require archive member {member}"
+        );
+    }
+    assert!(verify.contains("artifact missing expected member"));
+}
+
+#[test]
+fn package_release_stamps_git_build_info() {
+    let package = include_str!("../scripts/package-release.sh");
+    let build = include_str!("../build.rs");
+    for name in [
+        "DOSH_BUILD_GIT_HASH",
+        "DOSH_BUILD_COMMIT_DATE",
+        "DOSH_BUILD_GIT_DIRTY",
+    ] {
+        assert!(package.contains(name), "package script must export {name}");
+        assert!(build.contains(name), "build.rs must consume {name}");
+    }
+    assert!(package.contains("git rev-parse --short=12 HEAD"));
+    assert!(package.contains("git show -s --format=%cs HEAD"));
+    assert!(build.contains("cargo:rerun-if-env-changed=DOSH_BUILD_GIT_HASH"));
+}
+
 #[test]
 fn systemd_service_does_not_sandbox_remote_shells() {
     let service = include_str!("../packaging/systemd/dosh-server.service");