docs(bash): reframe stdin/env — the scrub is the security control, not a trust boundary

Address review: the "trusted-plugin surface" framing overstated the security
story. A model driving the `bash` tool already has equivalent power to set env
vars and feed stdin through ordinary shell syntax (`FOO=bar cmd`, heredocs), so
the `env`/`stdin` seam fields grant it no new capability — and they cannot
exfiltrate the harness's ambient credentials, because the credential SCRUB in
dsh-bash-local (which strips *KEY*/*SECRET*/*TOKEN* from process.env before the
child sees it) is the actual control, and it works regardless of these fields
(tool-call args are static JSON, never shell-evaluated).

So drop the "dangerous / trusted-plugin boundary" language across the RFC, the
three bash-package READMEs, the bash/src/types.ts JSDoc, and docs/bash.md (both
the type-equiv blocks — kept 1:1 with source — and the prose). The reality that
remains: the `bash` tool doesn't EXPOSE env/stdin as parameters because they'd
be redundant with shell syntax; the fields exist for in-process plugins (the
hooks bridges) to pass a JSON payload + CLAUDE_* vars cleanly. The guard test is
kept but reframed: it catches a future `...args` spread that would silently
forward model input into the post-scrub env merge, NOT a trust wall. No code or
behavior change.

packages/bash/bash-local/README.md

@@ -21,7 +21,7 @@ Design surveyed against the bash tools of Claude Code, OpenCode, Codex, and pi;
 - **Spawn per call, no shell state** — every call is a fresh non-login `bash -c` (deterministic; no rc files). All four surveyed tools spawn per call. `XXX(stateful-shell)` in `src/run.ts` records the two proven stateful designs (Claude Code's cwd-only persistence; Codex's PTY exec sessions) for when real workflows demand them.
 - **Process-group kills with escalation** — children are spawned `detached` (own process group); kills send SIGTERM to the group, then SIGKILL after a 3s grace (OpenCode's escalation; pipelines and subshells die with the parent). ESRCH is tolerated; daemons that re-parent away from the group can still survive — same caveat as the surveyed tools.
 - **Tail-keep truncation + spill files** — output beyond `maxOutputBytes` keeps the in-memory TAIL (errors/results cluster at the end — pi/OpenCode rationale) while the FULL stream is appended to a temp file whose path is reported when available. If the final spill close reports a delayed writeback failure, the executor still returns the tail but withholds the path rather than advertising a possibly incomplete file.
-- **Model-friendly env + credential scrub** — `process.env` minus credential-shaped vars (`*KEY*`/`*SECRET*`/`*TOKEN*`), then `NO_COLOR=1 TERM=dumb PAGER=cat GIT_PAGER=cat` (Codex's hardcoded set) so pagers and ANSI color don't garble results. A spec's **trusted-plugin** `env` is merged LAST (after the scrub), so an in-process plugin's explicit entry wins even on a credential-shaped name — the scrub guards the harness's *ambient* credentials from *model-driven* commands, not a trusted caller. The spec's `stdin` (also trusted-plugin) is written to the child and closed; with none supplied, stdin is an immediately-closed empty pipe (EOF, as before). See [the trusted-plugin RFC](../../../docs/rfc/implemented/architecture/2026-06-30-bash-stdin-env-trusted-plugin-surface.md).
+- **Model-friendly env + credential scrub** — `process.env` minus credential-shaped vars (`*KEY*`/`*SECRET*`/`*TOKEN*`), then `NO_COLOR=1 TERM=dumb PAGER=cat GIT_PAGER=cat` (Codex's hardcoded set) so pagers and ANSI color don't garble results. This scrub is the security control that keeps the harness's *ambient* credentials out of a spawned command. A spec's `env` is merged LAST (after the scrub), so a caller's explicit entry — a value it already holds — wins even on a credential-shaped name. The spec's `stdin` is written to the child and closed; with none supplied, stdin is an immediately-closed empty pipe (EOF, as before). Both `env`/`stdin` are set by in-process plugins (the hooks bridges); the model-facing tool doesn't expose them. See [the bash-stdin-env RFC](../../../docs/rfc/implemented/architecture/2026-06-30-bash-stdin-env-trusted-plugin-surface.md).
 - **Background tasks** — `start()` returns immediately, no timeout applies (Claude Code detaches timeouts when backgrounding), `readOutput()` is incremental with whole-stream byte offsets, and disposal kills everything. The spec's opaque `owner` token is stored on the tracked task and returned by `ownerOf(id)` — the executor never interprets it (the consumer's access policy does), and because it lives with the task here it survives a `tool-bash` HMR reload.
 
 ## Sandboxing

packages/bash/bash/README.md

@@ -30,4 +30,4 @@ Implementations subclass `BashExecutor`, implement the abstract methods, and cal
 
 `BashExecRequest` (command, workdir?, timeoutMs?, signal?, stdin?, env?, owner?) resolves to `BashExecSpec` (command, workdir, timeoutMs, signal?, stdin?, env?, owner) before execution; `owner` is optional on the request and **required-but-nullable** (`OwnerToken | undefined`) on the resolved spec, so a forgotten owner is a visible `undefined` rather than a silently-absent property. The task id (`BashTaskId`) and the `owner` token (`OwnerToken`) are [branded](../../util/brand) — `OwnerToken` is a DISTINCT brand from `SessionId` (the seam never imports `dsh-session`; the `dsh-tool-bash` consumer is the single boundary that casts its `SessionId` into one). `run()` returns `BashRunResult` (exitCode, signal, timedOut, aborted, timeoutMs, stdout/stderr as `CollectedOutput`) and `start()`/`readOutput()` use `BashTask`/`BashTaskRead` for the background side. See `src/types.ts` for the full contracts.
 
-`stdin` and `env` are a **trusted-plugin surface**: an in-process plugin (the hooks bridges, native plugins) sets them to feed a hook command its JSON payload on stdin and its `CLAUDE_PROJECT_DIR`/`CLAUDE_PLUGIN_ROOT` env. The model-facing `dsh-tool-bash` tool deliberately never forwards model input into either — so a model cannot smuggle an env var or stdin payload past the implementation's credential scrub. They are plain optionals on the resolved spec (unlike `owner`'s required-but-nullable): a missing one means "none", the safe default, not a security footgun. See [the trusted-plugin RFC](../../../docs/rfc/implemented/architecture/2026-06-30-bash-stdin-env-trusted-plugin-surface.md).
+`stdin` and `env` are set by in-process plugins (the hooks bridges, native plugins) to feed a hook command its JSON payload on stdin and its `CLAUDE_PROJECT_DIR`/`CLAUDE_PLUGIN_ROOT` env. The model-facing `dsh-tool-bash` tool does not expose them as parameters — a model already has equivalent power through shell syntax (`FOO=bar cmd`, a heredoc), so they would be redundant tool params. This is not a security boundary: the implementation's credential scrub (not these fields) is what keeps the harness's ambient secrets out of a spawned command. They are plain optionals on the resolved spec (unlike `owner`'s required-but-nullable): a missing one means "none", the safe default. See [the bash-stdin-env RFC](../../../docs/rfc/implemented/architecture/2026-06-30-bash-stdin-env-trusted-plugin-surface.md).

packages/bash/bash/src/types.ts

@@ -47,19 +47,20 @@ export interface BashExecRequest {
   signal?: AbortSignal | undefined
   /**
    * Bytes to write to the command's stdin, then close it. Absent leaves stdin
-   * closed/empty (the default for model-driven tool calls). A TRUSTED-PLUGIN
-   * surface: the model-facing bash tool does NOT thread model-supplied input
-   * here — it is set by in-process plugins (e.g. the hooks bridges, which write
-   * a hook command's JSON payload to its stdin).
+   * closed/empty (the default for model-driven tool calls). Set by in-process
+   * plugins (e.g. the hooks bridges, which write a hook command's JSON payload
+   * to its stdin); the model-facing bash tool does not expose it as a parameter
+   * (a model that needs stdin uses shell syntax like a heredoc or a pipe).
    */
   stdin?: string | undefined
   /**
    * Extra environment entries for the command, merged AFTER the
    * implementation's credential scrub (so an explicit entry here is honored even
-   * when its name matches the scrub pattern — the caller takes responsibility).
-   * Like {@link stdin}, a TRUSTED-PLUGIN surface: the model-facing bash tool
-   * never forwards model-supplied env; in-process plugins (the hooks bridges)
-   * set hook env vars (`CLAUDE_PROJECT_DIR`, `CLAUDE_PLUGIN_ROOT`, …) here.
+   * when its name matches the scrub pattern — the caller named a value it holds,
+   * not the harness's ambient secret). Set by in-process plugins (the hooks
+   * bridges set `CLAUDE_PROJECT_DIR`, `CLAUDE_PLUGIN_ROOT`, …); the model-facing
+   * bash tool does not expose it as a parameter (a model that needs an env var
+   * uses shell syntax like `FOO=bar cmd`).
    */
   env?: Record<string, string> | undefined
   /**
@@ -92,8 +93,7 @@ export interface BashExecSpec {
    * verbatim from {@link BashExecRequest.stdin}. OPTIONAL on the resolved spec
    * (unlike `owner`): it has no config default, so a missing one means "no
    * stdin" — the safe, ordinary case — not a silent footgun, so it stays a
-   * plain optional rather than required-but-nullable. A TRUSTED-PLUGIN surface
-   * (see the request field).
+   * plain optional rather than required-but-nullable (see the request field).
    */
   stdin?: string | undefined
   /**
@@ -101,7 +101,7 @@ export interface BashExecSpec {
    * {@link BashExecRequest.env} and merged by the implementation AFTER its
    * credential scrub (an explicit entry wins even when its name matches the
    * scrub pattern). OPTIONAL on the spec for the same reason as `stdin` — no
-   * config default, absent means "no extra env". A TRUSTED-PLUGIN surface.
+   * config default, absent means "no extra env".
    */
   env?: Record<string, string> | undefined
   /**

packages/bash/tool-bash/README.md

@@ -40,9 +40,9 @@ These tools own how their calls render in a UI (an editor's tool-call card) via
 
 When a background task finishes, a short notice is injected into the owning agent's session (`agent.inject()`, source `{kind: 'plugin', plugin: 'tool-bash'}`). The owning agent is found by its session token: the listener reads `ctx.bash.ownerOf(task.id)` and scans `ctx.get('agents')?.list()` for an agent whose `session.header.id` matches (read via `ctx.get` — `onTaskDone` runs on the bash fiber, a foreign fiber, so the `ctx.agents` proxy would throw). If no live agent carries that token — e.g. the owning session disconnected and its agent was disposed while the task ran on — the notice is dropped cleanly. Injection is **durable context for the next model request, not a wake-up** — an idle agent stays idle until something sends a message. That's why the tool descriptions tell the model to poll with `bash_output`.
 
-## Trusted-plugin boundary: env / stdin are never model-driven
+## The tool builds its request from named args only
 
-The `BashExecRequest` seam carries optional `stdin` and `env` (a **trusted-plugin surface** used by the hooks bridges to feed a hook command its JSON payload and `CLAUDE_*` env). This tool deliberately **never** threads model input into either: its request is built from `command`/`workdir`/`timeoutMs`/`signal`/`owner` only, so a model that includes `env` or `stdin` keys in its tool arguments has them ignored — it cannot smuggle an environment variable or stdin payload past `dsh-bash-local`'s credential scrub. A regression guard (the "trusted-plugin boundary" tests) drives the real tool with adversarial args and asserts the resulting request carries neither field. See [the trusted-plugin RFC](../../../docs/rfc/implemented/architecture/2026-06-30-bash-stdin-env-trusted-plugin-surface.md).
+The `BashExecRequest` seam carries optional `stdin` and `env`, used by the hooks bridges to feed a hook command its JSON payload and `CLAUDE_*` env. This tool does **not** expose them as parameters: its request is built from `command`/`workdir`/`timeoutMs`/`signal`/`owner` only, so a model that includes `env` or `stdin` keys in its tool arguments has them ignored. This is not a trust boundary — a model already has equivalent power through shell syntax (`FOO=bar cmd`, a heredoc), and the real defense against leaking the harness's ambient secrets is `dsh-bash-local`'s credential scrub, which works regardless. A regression guard drives the real tool with those extra args and asserts the resulting request carries neither field — its job is to catch a future refactor that blindly spreads `...args` into the request (which would silently forward model input into the post-scrub `env` merge), not to defend a wall. See [the bash-stdin-env RFC](../../../docs/rfc/implemented/architecture/2026-06-30-bash-stdin-env-trusted-plugin-surface.md).
 
 ## Permissions
 

packages/bash/tool-bash/tests/tools.spec.ts

@@ -864,14 +864,18 @@ describe('tool-owned UI presentation (presentCall / presentResult)', () => {
   })
 })
 
-describe('trusted-plugin boundary: the model-facing bash tool never sets env/stdin', () => {
+describe('the model-facing bash tool builds its request from named args only (no {...args} forward)', () => {
   /**
    * Records every {@link BashExecRequest} the consumer hands to `resolve()`, so a
-   * test can assert what the model-facing tool DID and DID NOT forward. `stdin`
-   * and `env` are a TRUSTED-PLUGIN surface (in-process plugins only); the `bash`
-   * tool must never thread model-supplied input into them, even when the model
-   * smuggles extra keys into the tool arguments. Foreground `run()` returns a
-   * canned result; `start()` is unused here.
+   * test can assert what the model-facing tool DID and DID NOT forward. The `bash`
+   * tool does not expose `stdin`/`env` as parameters (bash syntax already gives a
+   * model that power), so it must build its request from named args only and
+   * never spread unknown tool-call keys into it. This guard's job is to catch a
+   * future refactor that blindly forwards `...args` — which would silently thread
+   * model input into the post-scrub `env` merge — NOT to defend a trust boundary
+   * (the credential scrub in dsh-bash-local is the security control; see the
+   * bash-stdin-env RFC). Foreground `run()` returns a canned result; `start()` is
+   * unused here.
    */
   class RecordingBashExecutor extends BashExecutor {
     readonly requests: BashExecRequest[] = []
@@ -911,12 +915,14 @@ describe('trusted-plugin boundary: the model-facing bash tool never sets env/std
     return { ctx, bash: ctx.bash as RecordingBashExecutor }
   }
 
-  it('does not forward env/stdin even when the model smuggles them as extra arguments', async () => {
+  it('does not forward env/stdin even when the model includes them as extra arguments', async () => {
     const { ctx, bash } = await setupRecording()
-    // Adversarial args: the model includes `env` and `stdin` keys (and a
-    // credential-shaped value) hoping they reach the executor. The bash tool's
-    // schema ignores unknown keys, and execute() builds the request from only
-    // command/workdir/timeoutMs/signal — so the recorded request carries NEITHER.
+    // Extra args: the model includes `env` and `stdin` keys hoping they reach the
+    // executor. The bash tool's schema ignores unknown keys, and execute() builds
+    // the request from only command/workdir/timeoutMs/signal — so the recorded
+    // request carries NEITHER. (Not a security wall — the model could set an env
+    // var or feed stdin via shell syntax anyway; this just keeps the request
+    // shape honest so a future `...args` spread can't silently forward input.)
     await ctx.tools.execute({
       callId: CallId('boundary-1'),
       name: 'bash',