Keep live TUI output raw under retransmit pressure

Cargo.lock

@@ -436,7 +436,7 @@ dependencies = [
 
 [[package]]
 name = "dosh"
-version = "0.1.8"
+version = "0.1.10"
 dependencies = [
  "anyhow",
  "base64",

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "dosh"
-version = "0.1.8"
+version = "0.1.10"
 edition = "2024"
 license = "MIT"
 

install.ps1

@@ -141,6 +141,20 @@ function Verify-ArchiveVersion($ExtractDir, $Url) {
     }
 }
 
+function Install-Binary($Source, $Destination) {
+    $dir = Split-Path -Parent $Destination
+    $name = Split-Path -Leaf $Destination
+    $tmp = Join-Path $dir ".$name.tmp.$PID"
+    Copy-Item $Source $tmp -Force
+    try {
+        Move-Item $tmp $Destination -Force
+    }
+    catch {
+        Remove-Item $tmp -Force -ErrorAction SilentlyContinue
+        throw
+    }
+}
+
 $bindir = Join-Path $Prefix "bin"
 $configDir = Join-Path $HOME ".config\dosh"
 New-Item -ItemType Directory -Force -Path $bindir, $configDir | Out-Null
@@ -168,9 +182,9 @@ function Install-Prebuilt {
             if (-not $found) {
                 throw "prebuilt archive missing $bin"
             }
-            Copy-Item $found.FullName (Join-Path $bindir $bin) -Force
+            Install-Binary $found.FullName (Join-Path $bindir $bin)
         }
-        Copy-Item (Join-Path $bindir "dosh-client.exe") (Join-Path $bindir "dosh.exe") -Force
+        Install-Binary (Join-Path $bindir "dosh-client.exe") (Join-Path $bindir "dosh.exe")
         return $true
     }
     catch {
@@ -202,9 +216,9 @@ function Install-FromSource {
     try {
         Push-Location $src
         cargo build --release --bin dosh-client --bin dosh-bench
-        Copy-Item "target\release\dosh-client.exe" (Join-Path $bindir "dosh-client.exe") -Force
-        Copy-Item "target\release\dosh-client.exe" (Join-Path $bindir "dosh.exe") -Force
-        Copy-Item "target\release\dosh-bench.exe" (Join-Path $bindir "dosh-bench.exe") -Force
+        Install-Binary "target\release\dosh-client.exe" (Join-Path $bindir "dosh-client.exe")
+        Install-Binary "target\release\dosh-client.exe" (Join-Path $bindir "dosh.exe")
+        Install-Binary "target\release\dosh-bench.exe" (Join-Path $bindir "dosh-bench.exe")
     }
     finally {
         Pop-Location

install.sh

@@ -226,13 +226,26 @@ find_extracted_binary() {
   find "$1" -type f -name "$2" 2>/dev/null | sed -n '1p'
 }
 
+install_binary() {
+  src="$1"
+  dst="$2"
+  dst_dir="$(dirname "$dst")"
+  dst_base="$(basename "$dst")"
+  tmp="$dst_dir/.$dst_base.tmp.$$"
+  install -m 0755 "$src" "$tmp"
+  if ! mv -f "$tmp" "$dst"; then
+    rm -f "$tmp"
+    return 1
+  fi
+}
+
 install_extracted_binary() {
   found="$(find_extracted_binary "$1" "$2")"
   if [ -z "$found" ]; then
     echo "prebuilt archive missing $2" >&2
     return 1
   fi
-  install -m 0755 "$found" "$3"
+  install_binary "$found" "$3"
 }
 
 sha256_file() {
@@ -329,7 +342,7 @@ try_install_prebuilt() {
     install_extracted_binary "$tmpdir/extract" dosh-auth "$bindir/dosh-auth" || return 1
   fi
   if found_bench="$(find_extracted_binary "$tmpdir/extract" dosh-bench)" && [ -n "$found_bench" ]; then
-    install -m 0755 "$found_bench" "$bindir/dosh-bench"
+    install_binary "$found_bench" "$bindir/dosh-bench"
   fi
   return 0
 }
@@ -388,14 +401,14 @@ install_from_source() {
     fi
   fi
 
-  install -m 0755 target/release/dosh-client "$bindir/dosh-client"
+  install_binary target/release/dosh-client "$bindir/dosh-client"
   ln -sf dosh-client "$bindir/dosh"
   if [ "$role" = "server" ] || [ "$role" = "both" ]; then
-    install -m 0755 target/release/dosh-server "$bindir/dosh-server"
-    install -m 0755 target/release/dosh-auth "$bindir/dosh-auth"
+    install_binary target/release/dosh-server "$bindir/dosh-server"
+    install_binary target/release/dosh-auth "$bindir/dosh-auth"
   fi
   if [ -f target/release/dosh-bench ]; then
-    install -m 0755 target/release/dosh-bench "$bindir/dosh-bench"
+    install_binary target/release/dosh-bench "$bindir/dosh-bench"
   fi
 }
 

scripts/tui-harness.sh

@@ -9,6 +9,7 @@ for test_name in \
   tui_control_sequences_survive_transport_verbatim \
   unicode_output_survives_transport \
   tui_graph_glyphs_survive_fast_repaints_without_snapshot_substitution \
+  btop_style_graph_output_stays_raw_when_retransmit_history_overflows \
   large_tui_paint_is_delivered_in_mtu_safe_frames \
   resume_snapshot_preserves_alternate_screen_mode
 do

src/bin/dosh-server.rs

@@ -3336,7 +3336,7 @@ async fn broadcast_output(
     let sends = {
         let mut locked = state.lock().expect("server state poisoned");
         let scrollback = locked.config.scrollback;
-        let retransmit_window = locked.config.retransmit_window;
+        let retransmit_window = locked.config.retransmit_window.max(1);
         let session = locked
             .sessions
             .get_mut(&output.session)
@@ -3374,20 +3374,18 @@ async fn broadcast_output(
             client.send_seq += 1;
             // Count traffic toward the packet-count rekey trigger (spec §11).
             client.epoch_packets = client.epoch_packets.saturating_add(1);
-            // Only materialize a screen snapshot when this client has fallen too
-            // far behind; the common case sends the raw output bytes and must not
-            // clone the whole vt100 grid per client per packet.
-            let (bytes, snapshot) = if client.pending.len() >= retransmit_window {
-                client.pending.clear();
-                (screen_snapshot(session.parser.screen()), true)
-            } else {
-                (output.bytes.clone(), false)
-            };
+            // Live terminal bytes are never rewritten into vt100 snapshots. A
+            // snapshot is useful for attach/resume, but substituting it during a
+            // running TUI can lose graph/background-cell details that apps like
+            // btop rely on. If retransmit history is full, prune only history.
+            while client.pending.len() >= retransmit_window {
+                client.pending.pop_front();
+            }
             let frame = Frame {
                 session: output.session.clone(),
                 output_seq,
-                bytes,
-                snapshot,
+                bytes: output.bytes.clone(),
+                snapshot: false,
                 closed: false,
             };
             let body = protocol::to_body(&frame)?;
@@ -3400,9 +3398,6 @@ async fn broadcast_output(
                 SERVER_TO_CLIENT,
                 &body,
             )?;
-            while client.pending.len() >= retransmit_window {
-                client.pending.pop_front();
-            }
             client.pending.push_back(PendingFrame {
                 output_seq,
                 packet: packet.clone(),

tests/integration_smoke.rs

@@ -112,6 +112,21 @@ fn write_server_config_with_output_interval(
     config
 }
 
+fn write_server_config_with_retransmit_window(
+    dir: &tempfile::TempDir,
+    port: u16,
+    retransmit_window: u64,
+) -> std::path::PathBuf {
+    let config = write_server_config(dir, port);
+    let mut raw = fs::read_to_string(&config).unwrap();
+    raw = raw.replace(
+        "retransmit_window = 256\n",
+        &format!("retransmit_window = {retransmit_window}\n"),
+    );
+    fs::write(&config, raw).unwrap();
+    config
+}
+
 fn start_server(dir: &tempfile::TempDir, config: &std::path::Path) -> Child {
     let server = env!("CARGO_BIN_EXE_dosh-server");
     let child = Command::new(server)
@@ -1694,6 +1709,69 @@ fn tui_graph_glyphs_survive_fast_repaints_without_snapshot_substitution() {
     );
 }
 
+#[test]
+fn btop_style_graph_output_stays_raw_when_retransmit_history_overflows() {
+    let dir = tempfile::tempdir().unwrap();
+    let port = free_udp_port();
+    let config = write_server_config_with_retransmit_window(&dir, port, 3);
+    let mut server = start_server(&dir, &config);
+    let (socket, bootstrap, ok) = direct_attach(&config, port, "read-write");
+
+    let graph = "DOSH_BTOP_NET ⠀⠁⠃⠇⡇⣇⣧⣷⣿";
+    let input = Input {
+        bytes: format!(
+            "stty -echo; \
+             printf '\\033[?1049h\\033[?2026h\\033[?25l'; \
+             for i in 1 2 3 4 5 6 7 8 9 10; do \
+               printf '\\033[6;4H\\033[38;2;80;220;140m{} %s\\033[0m' \"$i\"; \
+             done; \
+             printf '\\033[?25h\\033[?2026l\\033[?1049l'\n",
+            graph
+        )
+        .into_bytes(),
+    };
+    send_encrypted(
+        &socket,
+        port,
+        PacketKind::Input,
+        ok.client_id,
+        2,
+        0,
+        &bootstrap.session_key,
+        &protocol::to_body(&input).unwrap(),
+    );
+
+    let mut text = String::new();
+    let mut snapshots = 0usize;
+    let deadline = std::time::Instant::now() + Duration::from_secs(3);
+    while std::time::Instant::now() < deadline
+        && !(text.matches("DOSH_BTOP_NET").count() >= 10 && text.contains("\x1b[?2026l"))
+    {
+        if let Some((_header, frame)) = recv_frame(&socket, &bootstrap.session_key) {
+            if frame.snapshot {
+                snapshots += 1;
+            }
+            text.push_str(&String::from_utf8_lossy(&frame.bytes));
+        }
+    }
+
+    let _ = server.kill();
+    let _ = server.wait();
+
+    assert_eq!(
+        snapshots, 0,
+        "live btop-style graph output must not be replaced by snapshots; got {snapshots}"
+    );
+    assert!(
+        text.matches("DOSH_BTOP_NET").count() >= 10
+            && text.contains("⣿")
+            && text.contains("\x1b[38;2;80;220;140m")
+            && text.contains("\x1b[?2026h")
+            && text.contains("\x1b[?2026l"),
+        "expected raw btop-style graph output to survive under retransmit pressure, got {text:?}"
+    );
+}
+
 #[test]
 fn large_tui_paint_is_delivered_in_mtu_safe_frames() {
     let dir = tempfile::tempdir().unwrap();