pi-pwsh

Route pi's shell, directory listing, and search tasks through PowerShell 7 (pwsh) on Windows.

Why

• Windows has no reliable bash implementation (Git Bash hangs on background processes, path translation is flaky).
• A tool named bash primes the model to emit POSIX syntax (&&, grep, $VAR), which fails under PowerShell.

This extension disables bash, ls, find, and grep, then registers a pwsh tool instead.

What it does

• Registers a pwsh tool that reuses pi's built-in bash tool definition — tail truncation (last 2000 lines / 50KB), full output saved to a temp file, non-zero exit codes surfaced as tool errors, streaming preview, and the built-in renderer all come for free. Only the spawn layer is replaced.
• Disables pi's built-in ls, find, and grep tools so filesystem discovery and search are routed through pwsh; prompt guidance prefers available cross-platform tools such as rg and fd and bounds native recursive cmdlets.
• Spawns pwsh -NoProfile -NonInteractive -ExecutionPolicy Bypass -Command <cmd>.
• Forces plain UTF-8 output without a BOM (non-ASCII output is not mangled, PowerShell formatting does not leak ANSI escapes, and piped native-command input is not prefixed with EF BB BF).
• Defaults Python subprocesses to PYTHONIOENCODING=utf-8, PYTHONUTF8=1, and PYTHONUNBUFFERED=1 so stdio and implicit text-file reads use UTF-8 and long-running logs stream promptly. Existing environment values are respected, and the defaults are scoped to processes launched by the tool.
• Preserves real native exit codes: pwsh -Command would otherwise flatten them to 0/1, which breaks rg (1 = no match vs 2 = error) and git diff --quiet-style semantics. An exit-code epilogue restores them — identically for foreground commands and background jobs.
• Auto-retries with cmd /c when a command fails with "not a valid Win32 application" (npm/yarn/pnpm are .cmd batch files on Windows). Skipped for commands rewritten to background jobs, where cmd's & semantics would be wrong.
• Kills the whole process tree (taskkill /T /F) on timeout or abort — no orphaned npm run dev processes.
• No default timeout; the model can pass timeout (seconds) per call.
• Probes Windows Sudo once per session; when available in inline mode, the tool description tells the model it can prefix a command with sudo to run it as administrator (each call still requires the user to approve the UAC prompt).

Background jobs

Every pwsh tool call spawns a fresh pwsh process, so native PowerShell jobs (Start-Job, the & background operator) die when the tool call ends. This extension fixes that from inside the shell — no extra tools:

• Every call dot-sources src/prelude.ps1, which overrides the job cmdlets (Start-Job, Get-Job, Receive-Job, Stop-Job, Remove-Job, Wait-Job) with implementations backed by real detached OS processes. Pipeline forms work: Get-Job | Stop-Job, Start-Job { npm run build } -Name build | Wait-Job | Receive-Job.
• Jobs are launched detached via double-spawn: a short-lived launcher process starts the job and exits immediately, breaking the parent chain that taskkill /T walks — aborting or timing out the tool call that started a job does not kill it. Jobs inherit the calling session's full environment (PATH, proxies, VIRTUAL_ENV, ...) through the launcher; Start-Job -Environment @{ NAME = 'value' } overrides or adds variables (stored in the job's wrap script under %TEMP%\pi-pwsh-jobs until Remove-Job).
• A trailing & (npm run dev &) is rewritten to Start-Job before execution, using PowerShell's own parser (src/background.ts) — strings, comments, the & { } call operator and && are never mistaken for it. Only single-pipeline commands are rewritten; anything else runs as-is.
• Job state lives in %TEMP%\pi-pwsh-jobs\ (one .meta.json + log/exit/script files per job), so it survives /reload and pi restarts and is inspectable by hand.
• Receive-Job consumes output like the native cmdlet (each read returns what arrived since the last one; -Keep re-reads, -Tail N peeks). Exit codes are captured (Get-Job shows Completed/Failed + ExitCode); Stop-Job kills the whole process tree (taskkill /T /F).
• Suspend-Job/Resume-Job/Debug-Job throw actionable guidance. Get-JobHelp prints the full reference in the shell.

Requirements

• PowerShell 7+ (pwsh on PATH). There is no fallback: if pwsh is not found, the extension shows an error notification and leaves the built-in bash tool active.

Installation

With pi:

pi install npm:@4fu/pi-pwsh

Or try it for a single run without installing:

pi -e npm:@4fu/pi-pwsh

From source

Symlink or copy into pi's extensions directory:

New-Item -ItemType Junction -Path "$HOME\.pi\agent\extensions\pi-pwsh" -Target "<this-repo>"

Or add the path to ~/.pi/agent/settings.json:

{
  "extensions": ["C:/path/to/pi-pwsh"]
}

Run npm install once in this directory, then /reload in pi.

Development

npm install
npm run typecheck

Tests:

# Runtime defaults (UTF-8 without BOM, plain errors, Python environment)
node scripts/smoke-runtime.mjs
# Job prelude end-to-end (each case is a fresh pwsh process, like a real tool call)
pwsh -NoProfile -ExecutionPolicy Bypass -File scripts/smoke-jobs.ps1
# Trailing-& interception (PowerShell parser based)
node scripts/smoke-background.mjs
# Foreground exit-code fidelity (native codes survive the pwsh -Command flattening)
node scripts/smoke-exitcode.mjs

License

MIT