Windows terminal host: BlitzOS agents run via conpty-host (supermux session-host)

electron-builder.yml

@@ -74,6 +74,13 @@ win:
   extraResources:
     - from: native/computer-use-helper/build/blitz-cu-helper.exe
       to: blitz-cu-helper.exe
+    # The supermux ConPTY session-host: the Windows terminal backend that conpty-host.mjs drives over
+    # host_rpc. resolveSessionHostBin looks for it at process.resourcesPath/bin/session-host.exe, so it
+    # maps to bin/session-host.exe here. Built by dist-win.ps1 (cargo --release, windows-gnu) into
+    # vendor/bin/session-host.exe. Self-contained: ldd shows only system DLLs (ucrtbase etc.), no MinGW
+    # runtime, so it runs on a clean Win10 1809+ box with no extra install.
+    - from: vendor/bin/session-host.exe
+      to: bin/session-host.exe
     # cross-platform analytics config; skipped when absent (local/fork builds)
     - from: build-config/activity-logging.json
       to: activity-logging.json

scripts/dist-win.ps1

@@ -22,6 +22,33 @@ Write-Host "[dist-win] building native CU helper"
 & (Join-Path $root 'native\computer-use-helper\build-win.ps1')
 if ($LASTEXITCODE -ne 0) { throw "[dist-win] helper build failed ($LASTEXITCODE)" }
 
+# The Windows terminal backend: the supermux ConPTY session-host (conpty-host.mjs drives it over host_rpc).
+# Bundled via win.extraResources at vendor/bin/session-host.exe (resolveSessionHostBin reads it at
+# process.resourcesPath/bin/session-host.exe). It is a VENDORED binary (like vendor/bin/tmux on mac): a
+# checkout already carries it, so a plain build just uses it. To REFRESH from source, set $env:SUPERMUX_REPO
+# to the supermux repo root and re-run. Self-contained (ldd: only system DLLs, no MinGW runtime).
+$sessionHost = Join-Path $root 'vendor\bin\session-host.exe'
+if ($env:SUPERMUX_REPO) {
+  Write-Host "[dist-win] building supermux session-host from $env:SUPERMUX_REPO"
+  Push-Location (Join-Path $env:SUPERMUX_REPO 'server')
+  cargo build --release --bin session-host --target x86_64-pc-windows-gnu
+  $built = Join-Path (Get-Location).Path 'target\x86_64-pc-windows-gnu\release\session-host.exe'
+  Pop-Location
+  if (-not (Test-Path $built)) { throw "[dist-win] session-host build produced no exe at $built" }
+  New-Item -ItemType Directory -Force (Split-Path $sessionHost) | Out-Null
+  Copy-Item $built $sessionHost -Force
+  Write-Host "[dist-win] vendored session-host.exe ($([math]::Round((Get-Item $sessionHost).Length/1MB,1)) MB)"
+} elseif (-not (Test-Path $sessionHost)) {
+  throw "[dist-win] vendor\bin\session-host.exe missing and SUPERMUX_REPO not set. Set `$env:SUPERMUX_REPO to the supermux repo root to build it."
+} else {
+  Write-Host "[dist-win] using vendored vendor\bin\session-host.exe (set `$env:SUPERMUX_REPO to refresh from source)"
+}
+
+# PREREQUISITE (Windows): Git for Windows must be installed on the END-USER machine. The agent runtime is
+# POSIX (claude runs wait.sh / curl / tail / cat via its Bash tool), and Claude Code makes Git Bash optional
+# (it falls back to the PowerShell tool, which cannot run that runtime). conpty-host pins the agent to Git
+# Bash (CLAUDE_CODE_GIT_BASH_PATH); document Git for Windows in the install instructions.
+
 Write-Host "[dist-win] electron-vite build"
 npm run build
 if ($LASTEXITCODE -ne 0) { throw "[dist-win] electron-vite build failed ($LASTEXITCODE)" }

src/main/agent-runtime.mjs

@@ -206,6 +206,48 @@ export function buildAgentCommand({ runtime = AGENT_RUNTIME_CLAUDE, cmd, claudeS
   return buildClaudeCommand({ cmd: cmd || 'claude', claudeSid, mode, bootstrapFile, effort, hooks })
 }
 
+/** Resolve a POSIX shell (Git Bash) on Windows. The agent command + runtime are POSIX-shaped, so on win32
+ *  the ConPTY terminal host (which runs a program directly, no shell) must launch them under bash. Order:
+ *  BLITZ_BASH_BIN, then the standard Git-for-Windows install paths. null = not found. Cached. */
+let resolvedBash
+function resolveBashBin() {
+  if (resolvedBash !== undefined) return resolvedBash
+  const cands = [
+    process.env.BLITZ_BASH_BIN,
+    'C:\\Program Files\\Git\\bin\\bash.exe',
+    'C:\\Program Files\\Git\\usr\\bin\\bash.exe',
+    'C:\\Program Files (x86)\\Git\\bin\\bash.exe'
+  ].filter(Boolean)
+  resolvedBash = cands.find((p) => { try { return existsSync(p) } catch { return false } }) || null
+  return resolvedBash
+}
+
+/** Windows: wrap a POSIX agent command so the ConPTY terminal host can run it. The command uses
+ *  "$(cat bootstrap)" substitution and the agent then runs bash/curl/tail/wait.sh, none of which the bare
+ *  CreateProcessW path provides. Write the command to a per-session launcher script and return a
+ *  `bash <script>` command (TWO clean tokens, so the host's whitespace/quote tokenizer can't mangle it);
+ *  `exec` makes the agent the pane process. Validated on Windows: MSYS `cat` reads the backslash bootstrap
+ *  path and claude.exe resolves under Git Bash. No-op off win32; if Git Bash is absent the command passes
+ *  through unchanged (it fails visibly rather than being silently mangled). */
+function wrapAgentCommandForPlatform(command, sessionsDir, id) {
+  if (process.platform !== 'win32') return command
+  const bash = resolveBashBin()
+  if (!bash) return command
+  // Git Bash treats backslashes as escapes in an unquoted token, so an absolute `exec C:\...\claude.exe`
+  // collapses to `C:...claude.exe: not found`. Convert the Windows paths in the command to forward slashes,
+  // which MSYS accepts everywhere (the exec target AND the $(cat <bootstrap>) path). The only backslashes
+  // in the command are Windows paths; the args (UUID, --settings JSON) have none.
+  const posix = command.replace(/\\/g, '/')
+  const launch = join(sessionDir(sessionsDir, id), 'launch.sh')
+  // Pin the agent's OWN Bash tool to Git Bash: claude makes Git for Windows optional (it falls back to
+  // the PowerShell tool, which can't run the POSIX agent runtime - wait.sh / bash / tail / cat). Exported
+  // here so the exec'd claude.exe inherits them. Single-quote the bash path so its backslashes survive.
+  // Source: code.claude.com/docs/en/setup (CLAUDE_CODE_GIT_BASH_PATH, CLAUDE_CODE_USE_POWERSHELL_TOOL).
+  const pin = `export CLAUDE_CODE_GIT_BASH_PATH='${bash}'\nexport CLAUDE_CODE_USE_POWERSHELL_TOOL=0\n`
+  try { writeFileSync(launch, `#!/usr/bin/env bash\n${pin}exec ${posix}\n`) } catch { return command }
+  return `"${bash}" "${launch.replace(/\\/g, '/')}"`
+}
+
 /** Has claude ALREADY created this conversation on disk? claude writes `<configDir>/projects/<encoded-cwd>/
  *  <session-id>.jsonl` (encoded-cwd = the workspace path with every `/` and `.` turned into `-`; we don't
  *  relocate CLAUDE_CONFIG_DIR, so configDir defaults to ~/.claude). The session-id is a UUID, so a hit is
@@ -283,14 +325,14 @@ export function prepareAgentLaunch({ sessionsDir, id, url, cmd, runtime = AGENT_
     agentSessionId,
     claudeSessionId: claudeState.claudeSessionId,
     established: claudeState.established, // surfaced so the re-exec path persists the (possibly rotated) id + correct established flag
-    command: buildAgentCommand({
+    command: wrapAgentCommandForPlatform(buildAgentCommand({
       runtime: agentRuntime,
       cmd: cmd || (agentRuntime === AGENT_RUNTIME_CODEX_SERVERLESS ? 'codex' : 'claude'),
       claudeSid: claudeState.claudeSessionId,
       mode: claudeState.established ? 'resume' : 'create',
       bootstrapFile: file,
       effort
-    })
+    }), sessionsDir, id)
   }
 }