deepseek-harness/packages/subprocess/subprocess/README.md

@deepseek-ai/dsh-subprocess

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The subprocess seam (ctx.subprocess). The abstract SubprocessService exposes one method — spawn(spec): SubprocessHandle — plus the vocabulary shared by every consumer: the fully-explicit SubprocessSpawnSpec, SubprocessHandle with its non-consuming offset-based output readers, SubprocessOutcome, CollectedOutput, and the managed DSH_* environment namespace (DSH_ENV_PREFIX, DshEnvironment). The local implementation lives in dsh-subprocess-local.

Contract

• spawn(spec) returns immediately with a live handle; done resolves at process close with exit facts (SubprocessOutcome carries no output and no cause classification) and rejects only for spawn-level failures.
• The spec is fully explicit — argv, cwd, per-stream stdio dispositions, grace — because deployment-varying defaults belong to the calling seam's config, not to a hidden subprocess-service default (the dsh-bash request/spec split is the owning template). argv is never shell-interpreted; a consumer that wants a shell passes ['bash', '-c', command] itself.
• Stdio is Node-shaped per stream: 'pipe' hands the caller the raw stream for its own protocol framing (LSP JSON-RPC, ACP ndjson), 'inherit' passes the parent descriptor through for diagnostics, and collect mode ({ maxBytes, spill? }) buffers a bounded tail with an optional full-stream spill file. Collect readers take whole-stream byte offsets and never consume, so independent readers cannot steal one another's deltas; a read whose offset slid out of the in-memory tail is lossy and points at the spill file when one exists. Collected output stays readable after settlement.
• Termination is tree-scoped on every platform (POSIX detached groups with direct-child fallback; Windows taskkill /T): kill(signal) sends one signal Node-style and is a no-op after settlement, terminate() (and the spec's abort signal) escalates SIGTERM→grace→SIGKILL, waitForExit() observes the whole tree, and dispose(graces) runs the cooperative stdin-EOF→SIGTERM→SIGKILL ladder out-of-process children need — the manager reacts but never classifies why (callers own deadlines and cause classification).
• scrubbedParentEnv() / SENSITIVE_ENV_PATTERN are the one shared scrub definition: ambient credential-shaped and DSH_* names are dropped, explicit env merges after the scrub (a deliberately forwarded key survives), and dshEnv carries current harness facts on its own validated channel. Spawners that cannot route through the service (node-pty backends, SDK-managed transports) import the function.
• Disposal of the service terminates all still-running managed processes and awaits their exit.

See the subprocess data-structure catalog and the seam Agent Note.

Model Experience

Indirectly, through consumer seams (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

• node-pty and SDK-managed spawns share only the scrub — the PTY backend's terminal fork and the MCP SDK's own stdio transport cannot route their spawns through this seam (the library owns the fork/spawn call); they import scrubbedParentEnv so the environment policy stays single-sourced.
• The dispose ladder assumes stdin-EOF cooperation — a child that quiesces on a different signal (SIGHUP conventions, control sockets) needs its own tier-1 before the generic ladder fits.