deepseek-harness/packages/shell/pwsh-local/README.md

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description: "The local PowerShell executor for deployments and maintainers choosing, configuring, or debugging unconfined PowerShell command execution over the shell seam."

kind: "package-reference"

@deepseek-ai/dsh-pwsh-local

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Summary

dsh-pwsh-local is the PowerShell executor: every command runs as a fresh, non-interactive pwsh -Command process with no profile files, so no shell state survives between calls. It mirrors dsh-bash-local's semantics call-for-call and adds PowerShell-shaped concerns: executable resolution, UTF-8 output pinning, and the model-friendly terminal environment. Commands run with the harness process's own authority — this executor confines nothing; compose dsh-pwsh-sandbox when commands need the sandbox capability. The model-facing pwsh tool talks to it once it is mounted.

Table of Contents

• Use this package
• Understand the implementation
• Further Exploration
• Model Experience
• Known Limitations and Deferred Work
• Dev Note

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Use this package

Mount this executor when a composition needs PowerShell command execution — typically on Windows — without confinement. It registers as ctx.shell, and the model-facing pwsh tool works over it immediately: an agent calls the tool, and the command runs as a fresh pwsh -Command process with the budgets below.

When to choose it

It is the Windows counterpart of dsh-bash-local: choose it where pwsh is the platform shell, so a composition can swap the POSIX rows for the pwsh rows and keep the same semantics. The executor resolves the pwsh executable from an explicit pwshPath, well-known Windows install locations, PATH entries, or Windows PowerShell 5.1 as a last resort. For unconfined execution it is the default; compose dsh-pwsh-sandbox when commands need the sandbox capability.

Minimal configuration

Load the executor with the budgets you want; every field has a default, so the smallest composition is the plugin entry alone. The settings provider (when composed) layers a user section over this entry, so budgets can change at runtime without a reload (see Adjusting budgets at runtime).

- id: bash
  name: '@deepseek-ai/dsh-pwsh-local'
  config:
    cwd: C:\path\to\workspace
    timeoutMs: 120000

Field	Default	Meaning
cwd	process.cwd()	Default working directory for commands
timeoutMs	120,000	Default foreground timeout, in milliseconds
maxTimeoutMs	600,000	Cap for per-call timeout overrides
maxOutputBytes	64,000	Per-stream in-memory output cap; overflow spills to a temp file
maxSpillBytes	67,108,864	Per-stream full-output spill cap
graceMs	3,000	Grace period for kill escalation and post-exit pipe draining
pwshPath	resolved	Explicit pwsh executable; else well-known locations, then PATH

The generated configuration catalog is the exhaustive source for every accepted field and its JSDoc.

Running commands

Run a command with run and read its output from the result; a nonzero exit, a timeout, or a cancellation resolves descriptively, and only infrastructure failures reject. The command string rides as one argument to -Command: PowerShell parses the text itself and no intermediate shell exists, so there is no shell-quoting layer to escape and native Win32 paths pass through unchanged. Every command pins UTF-8 output first, so non-ASCII output is not garbled even on the Windows PowerShell 5.1 fallback. The environment is model-friendly: NO_COLOR=1 PAGER=cat GIT_PAGER=cat (no TERM=dumb — a POSIX concept), with explicit caller-provided entries still winning.

const result = await ctx.shell.run(ctx.shell.resolve({ command: 'Get-ChildItem' }))
if (result.timedOut) console.log('timed out after', result.timeoutMs)

Background processes

Await start to run a command in the background; it resolves with the prepared process handle and no execution timeout applies. Cancellation or preparation failure rejects before a handle is published. readOutput() merges the stream deltas into one consuming read, marking stderr under a [stderr] section; kill() terminates the provider-managed range; done settles when the direct command closes and never rejects. Job ids, ownership, polling, and notices belong to the generic ctx.jobs runtime, which the tool layer registers the handle with.

Adjusting budgets at runtime

When a settings provider is composed, this executor registers the capability's shared shell settings namespace — the same one the POSIX family uses, because a host composes exactly one provider of ctx.shell — so a user section in settings.yaml layers over the composition entry and the next command runs with the new budgets. Values the schema cannot judge — positive and finite numbers, and the graceMs timer bound — are refused at the write, leaving the running executor on its last good section.

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Understand the implementation

Implementation internals — click to expand

This section explains the design of the executor and points at the code that realizes it; the observable behavior is fully covered in [Use this package](#use-this-package). ### Design concept The executor is the PowerShell Service Provider for the `ctx.shell` seam built on the subprocess capability: it owns everything pwsh-shaped — executable resolution, command defaulting and caps, deadline fusion and cause classification, UTF-8 output pinning, the model-friendly terminal environment, and the background read merge — while managed-range mechanics (bounded spill-backed output, credential scrub, termination escalation, quiescence, and disposal) belong to the subprocess service. Every call spawns a fresh non-interactive `pwsh -Command` with `-NoLogo -NoProfile -NonInteractive`, so commands are deterministic and profile state never leaks between calls. ### Source map | File | Role | |---|---| | [`src/index.ts`](src/index.ts) | Plugin entry: `PwshLocalExecutor`, `Config`, settings wiring, argv seam | | [`src/resolve.ts`](src/resolve.ts) | Pure `resolvePwshPath`/`candidatePwshPaths` executable resolution | | — | No runtime invariant companion is published; this package exposes no independent event sequence or mutable data relation beyond contracts enforced at its owning seam. | | `tests/` | Exercised behavior: budgets, classification, resolution, background handles | ### Main flow A call runs through three steps: `resolve()` fills `workdir`/`timeoutMs`/`stdoutMaxBytes` from config (capping the per-call `timeoutMs` override); the executor builds the pwsh argv — `pwsh -NoLogo -NoProfile -NonInteractive -Command ` — fuses the config-clamped timeout with the caller's abort signal into one deadline, and spawns through `ctx.subprocess` with explicit byte caps and the `graceMs`; the settled outcome is classified and projected into a `ShellRunResult`. Windows reports forced termination as exit 1 without a signal, so signal-stamped facts are POSIX-only there; the timeout/abort classification is platform-independent. The foreground deadline starts before argv preparation and retains the same signal and remaining budget through execution. Preparation timeout returns empty output, `timedOut: true`, and null `exitCode` and `signal`; caller cancellation before process publication still rejects. Late preparation success or failure cannot trigger a spawn. ### Invariants and ownership - The `graceMs` budget must be positive, finite, and no greater than `MAX_TIMER_DELAY_MS` so Node can represent it with one timer; invalid values are refused where they are written. - Environment layering is fixed: terminal overrides first, then the caller's `env`, then the trusted `dshEnv` snapshot last; the subprocess service scrubs ambient credentials and inherited `DSH_*` names independently. - Executable resolution is a pure function of `(configured, env, platform)` and re-probes the filesystem only when the stored `pwshPath` differs from the one the current executable was resolved from. - A background process belongs to the subprocess service: it survives an executor-only reload and is killed and joined when the service disposes.

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Further Exploration

Read these pages when the executor contract is not enough. They move from the seam to the confining sibling and the PowerShell tool.

• shell seam — the executor contract this provider implements, including the request/spec split.
• bash-local — the POSIX counterpart this executor mirrors call-for-call.
• pwsh-sandbox — the confining executor to compose instead when commands need the sandbox capability.
• tool-pwsh — the model-facing pwsh tool over this executor.
• Bash executor subsystem — request/spec vocabulary, results, and the service contract in full.

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Model Experience

Indirectly, through dsh-tool-pwsh, which renders this executor's bounded stdout/stderr tails, background-process deltas (through the generic job runtime), spill-file paths, and infrastructure failures.

KV Cache effect

No direct invalidation; the named consumer owns any request-prefix changes.

Known Limitations and Deferred Work

These limits define when this executor is a poor fit. They are current package constraints, not a roadmap.

• Unconfined by itself — commands run with the harness process's authority; deployments needing confinement compose a sandboxing executor or policy instead.
• No persistent shell or PTY — every call starts a fresh pwsh -Command.
• The command string is PowerShell text — the -Command domain has no shell-quoting layer, but a model-facing command is parsed by PowerShell itself, so PowerShell syntax errors are command failures, not launch failures.
• A background provider-failure note is single-delivery — SubprocessHandle.done can reject before or after target execution begins, so the executor injects the stage-neutral subprocess failed before reporting an outcome: … into exactly one readOutput() delta; a reader that discards that delta cannot recover it.
• Windows termination reports no signal — a force-killed process settles as exit 1 with signal: null, so signal-based status classification does not apply on Windows; kill()-initiated stops still stamp killed directly.
• The encoding preamble precedes the command — PowerShell requires param(...), #requires, and using statements at the very top of a script, so a command whose first statement is one of those cannot run under the UTF-8 output preamble; wrap a param(...) script in & { … }, and run using/#requires scripts from a file instead.
• Non-ASCII stdin under Windows PowerShell 5.1 may be mis-decoded — the preamble pins output encoding only; [Console]::InputEncoding stays at the host default because setting it under redirected stdin throws; pwsh 7 defaults to UTF-8 and is unaffected.

Dev Note

Working context for maintainers — click to expand

None.