# @deepseek-ai/dsh-subprocess-local

English | [中文](README.zh.md)

Local Service Provider for the [`@deepseek-ai/dsh-subprocess`](../subprocess/README.md) seam. `LocalSubprocessRuntime` resolves local executables, spawns ordinary detached process trees with explicit stdio, and implements terminal processes through `node-pty` plus platform process inspection. It has no config: every disposition, limit, terminal dimension, grace, and directory arrives from the calling capability seams ([`dsh-bash-local`](../../shell/bash-local/README.md), [`dsh-lsp-stdio`](../../lsp/lsp-stdio/README.md), and [`dsh-terminal-bash`](../../terminal/terminal-bash/README.md)).

## Behavior

- **Detached process trees with platform-correct signalling** — POSIX children are spawned `detached` (own process group) and signalled by negative pgid with a direct-child fallback; Windows terminates the tree via `taskkill /PID <pid> /T /F`. `terminate()` — the handle's only termination verb — sends SIGTERM then SIGKILL after the spec's grace (OpenCode's escalation; pipelines and subshells die with the parent) and is a no-op once the tree is gone; `waitForExit()` polls whole-tree liveness so consumer teardown confirms real quiescence. After the leader exits, still-open pipes receive the same bounded drain grace so a surviving descendant cannot hold the outcome open indefinitely. ESRCH is tolerated; daemons that re-parent away from the group can still survive.
- **Per-stream dispositions** — `'pipe'` hands the raw stream to the caller untouched (protocol framing stays consumer-owned); `'inherit'` passes the parent descriptor through; collect mode keeps the in-memory TAIL beyond its cap (errors and results cluster at the end — pi/OpenCode rationale) while the FULL stream is appended to a private temp file when a spill cap is configured — omitting `spill` keeps only the tail, the diagnostic shape. A stream larger than the spill cap discards its now-incomplete spill and returns only the marked truncated tail; spill fds are sealed at settlement, and a failed final close withholds the path rather than advertising an incomplete file. Spill files are `0600` with random names under a lazily-created `0700` per-process directory.
- **Credential scrub + explicit merge** — `process.env` minus credential-shaped vars (`*KEY*`/`*PASSWORD*`/`*SECRET*`/`*TOKEN*`) and all ambient `DSH_*` names; the spec's explicit `env` merges after that scrub with no namespace validation, so a deliberately supplied credential or current `DSH_*` fact wins while stale nested-harness identity cannot leak in ambiently. Supplied stdin is written and closed; otherwise fd 0 is `/dev/null`. See the [stdin/env Agent Note](../../../.agents/notes/implemented/architecture/2026-06-30-bash-stdin-env-trusted-plugin-api.md) and [managed environment Agent Note](../../../.agents/notes/implemented/feature/2026-07-10-agent-session-identity-and-log-location.md).
- **Offset-based reads** — collect-mode readers return deltas in whole-stream byte coordinates; the service never holds a cursor, so consumer-owned cursors (the bash background read path) and full-stream re-reads coexist, before and after settlement.
- **Executable lookup** — `resolveExecutable` checks absolute files or searches the scrubbed effective PATH with platform-aware executable extensions; relative paths containing separators are rejected at the seam, and relative PATH entries resolve from the host process cwd.
- **Terminal-process ownership** — `spawnTerminal` allocates `node-pty`, bridges UTF-8 terminal text, inspects and signals the current foreground process group, and exposes one awaited termination operation that sweeps descendants before and after terminating the top-level shell. Each foreground inspection retains exact identities from the rooted tree; Linux also enumerates the POSIX session after its leader exits. A previously observed macOS descendant and any same-session Linux member therefore remain fenced after reparenting, while pid/start identity prevents cleanup from following PID reuse. The higher PTY backend owns prompt readiness, buffers, and model-facing operations.
- **Terminate-and-join disposal** — the service retains live handles so its own disposal can escalate every running tree and await its exit; quiescent and spawn-failed handles leave the live set after whole-tree or terminal-session cleanup finishes.
- **Synchronous host-exit finalization** — while the service effect is active, a Node `exit` listener force-terminates every ordinary tree and observable terminal session still in the same live sets. The local-only operations send POSIX SIGKILL to the managed group, run Windows `taskkill /T /F`, and synchronously signal captured/current terminal identities around the PTY root kill; they create no promise or timer, preserve the host's exit code and diagnostic, contain each target's failure, and do not claim quiescence. Normal disposal keeps the awaited graceful path above. See the [host-exit cleanup decision](../../../.agents/notes/implemented/bug-fix/2026-08-11-synchronous-subprocess-exit-cleanup.md).

## Model Experience

Indirectly, through Consumers (today the bash executor family behind `dsh-tool-bash`), which own all model-facing rendering of process output and lifecycle.

#### KV Cache effect

No direct invalidation; the named consumers own any request-prefix changes.

## Known Limitations and Deferred Work

- **Windows tree support is best-effort** — termination routes through `taskkill /PID <pid> /T /F` with all outcomes contained (absent tree, races, missing binary), and liveness falls back to the direct-child boundary.
- **Terminal process inspection is Linux/macOS only** — the terminal primitive fails when its inspector has no supported platform implementation; Linux exact probes cover x64 and arm64, while macOS uses `ps` snapshots.
- **A daemonized terminal descendant can still escape the observable boundary** — on macOS, a child that reparents before any foreground-inspection snapshot is no longer discoverable from the `node-pty` root; on Linux, a child that calls `setsid` leaves both the tree and owned terminal session. The local provider does not add a continuous process-table monitor.
- **In-process cleanup requires a JavaScript-observable exit** — direct `process.exit()`, default uncaught exceptions, and default unhandled rejections emit Node's synchronous `exit` event. The default OS disposition for an unhandled `SIGTERM`, `SIGINT`, or `SIGHUP` bypasses that event; an application covers those signals only by installing a handler that performs normal disposal or calls `process.exit()`. `SIGKILL`, fatal OOM, `process.abort()`, native crashes, power loss, and any failure that cannot run JavaScript require an external supervisor, container init, or equivalent OS owner.
- **The credential scrub is a name heuristic** — `*KEY*`/`*PASSWORD*`/`*SECRET*`/`*TOKEN*` only; differently-named secrets (e.g. `*PASSPHRASE*`) pass through, and a whitelist for over-scrubbed vars is noted future work.
- **Completed spill files are not deleted** — bounded full-output recovery files (and the private per-process spill dir) accumulate under the OS tmpdir until something external cleans them; oversize incomplete spills are discarded and deletion is attempted immediately, but a cleanup failure can leave a bounded file behind.

The raw process handling lives in `src/spawn.ts`; `src/index.ts` is the service wiring.
