feat(bash): generalize managed shell environment

packages/bash/bash-local/README.md

@@ -22,7 +22,7 @@ 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 the `graceMs` grace (default 3s — 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. 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`, when supplied, is written to the child and closed; with none supplied, fd 0 is `/dev/null` — the exact pre-seam default, so a command that probes stdin's file type is unaffected. 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).
+- **Model-friendly env + credential/namespace scrub** — start with `process.env` minus credential-shaped vars (`*KEY*`/`*SECRET*`/`*TOKEN*`) and every `DSH_*`, then apply `NO_COLOR=1 TERM=dumb PAGER=cat GIT_PAGER=cat`. Ordinary spec `env` is merged next and may restore caller-held credential-shaped values, but is rejected if it tries to set reserved `DSH_*`; the trusted spec `dshEnv` snapshot is merged last. This keeps ambient secrets out and prevents a nested/previous harness identity from surviving when the current registry omits it. The spec's `stdin`, when supplied, is written to the child and closed; with none supplied, fd 0 is `/dev/null`. See [the bash-stdin-env RFC](../../../docs/rfc/implemented/architecture/2026-06-30-bash-stdin-env-trusted-plugin-surface.md) and [the session environment RFC](../../../docs/rfc/implemented/feature/2026-07-10-agent-session-identity-and-log-location.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-local/src/index.ts

@@ -126,10 +126,11 @@ export class LocalBashExecutor extends BashExecutor {
       workdir: request.workdir ?? this.config.cwd ?? process.cwd(),
       timeoutMs,
       ...request.signal ? { signal: request.signal } : {},
-      // Carry stdin/env through verbatim — optional, no config default (absent
-      // means none). env merges AFTER the scrub in run.ts.
+      // Carry stdin/ordinary env/trusted dshEnv through verbatim — optional,
+      // no config default. run.ts owns the scrub and merge order.
       ...request.stdin !== undefined ? { stdin: request.stdin } : {},
       ...request.env !== undefined ? { env: request.env } : {},
+      ...request.dshEnv !== undefined ? { dshEnv: request.dshEnv } : {},
       // Carry the owner through verbatim (required-but-nullable on the spec):
       // the executor never interprets it — the consumer's access policy does.
       owner: request.owner,
@@ -153,6 +154,7 @@ export class LocalBashExecutor extends BashExecutor {
       signal: d.signal,
       stdin: spec.stdin,
       env: spec.env,
+      dshEnv: spec.dshEnv,
     }, this.internals).done
     // Classify the FIRST abort reason: a BASH_TIMEOUT TimeoutReason means our
     // timeout cut the command short; any other abort — an upstream cancel, or a
@@ -179,6 +181,7 @@ export class LocalBashExecutor extends BashExecutor {
       signal: spec.signal,
       stdin: spec.stdin,
       env: spec.env,
+      dshEnv: spec.dshEnv,
     }, this.internals)
 
     const id = BashTaskId(`bash-${this.nextTaskId++}`)

packages/bash/bash-local/src/run.ts

@@ -27,7 +27,7 @@ import { randomBytes } from 'node:crypto'
 import { closeSync, mkdtempSync, openSync, writeSync } from 'node:fs'
 import { tmpdir } from 'node:os'
 import { join } from 'node:path'
-import type { CollectedOutput } from '@deepseek-ai/dsh-bash'
+import type { CollectedOutput, DshEnvironment } from '@deepseek-ai/dsh-bash'
 
 /**
  * Model-friendly environment overrides: disable colors, pagers, and
@@ -50,27 +50,33 @@ export const ENV_OVERRIDES = {
 export const SENSITIVE_ENV_PATTERN = /KEY|SECRET|TOKEN/i
 
 /**
- * `process.env` minus credential-shaped vars, plus the model-friendly
- * overrides, plus any caller-supplied `extra` entries.
+ * Build a child environment from scrubbed ambient values, terminal overrides,
+ * ordinary caller entries, and a trusted managed `DSH_*` snapshot.
  *
- * Layering matters: the scrub drops `process.env` credentials, then
- * `ENV_OVERRIDES` forces the model-friendly terminal vars, then `extra` is
- * merged LAST so an explicit caller entry wins even when its name matches the
- * scrub pattern (the scrub is the control that stops the HARNESS's ambient
- * credentials leaking into a spawned command; a caller that explicitly sets a
- * var named a value it already holds, not that ambient secret). `extra` is set
- * by in-process plugins (the hooks bridges), not the model — `dsh-tool-bash`
- * builds its request from named fields only and does not forward model input
- * here (see its README, § "The tool builds its request from named args only").
- * @param extra - caller-supplied entries merged last; an explicit entry wins even against the scrub and the overrides.
+ * Ambient credentials and all ambient `DSH_*` are removed first;
+ * `ENV_OVERRIDES` then forces model-friendly terminal values, ordinary `extra`
+ * follows, and `dshEnv` merges last. Ordinary `extra` may restore a
+ * credential-shaped name whose value the caller already holds, but cannot set
+ * the managed namespace. `dsh-tool-bash` builds both channels from trusted
+ * named fields and never forwards model-provided environment objects.
+ * @param extra - ordinary caller-supplied entries; `DSH_*` names are rejected.
+ * @param dshEnv - trusted managed `DSH_*` entries for the current execution.
  * @returns the environment to hand to `spawn` for the child process.
  */
-export function childEnv(extra?: Record<string, string>): NodeJS.ProcessEnv {
+export function childEnv(
+  extra?: Readonly<Record<string, string>>,
+  dshEnv?: DshEnvironment,
+): NodeJS.ProcessEnv {
   const env: NodeJS.ProcessEnv = {}
   for (const [key, value] of Object.entries(process.env)) {
-    if (!SENSITIVE_ENV_PATTERN.test(key)) env[key] = value
+    if (!SENSITIVE_ENV_PATTERN.test(key) && !key.startsWith('DSH_')) env[key] = value
   }
-  return { ...env, ...ENV_OVERRIDES, ...extra }
+  for (const key of Object.keys(extra ?? {})) {
+    if (key.startsWith('DSH_')) {
+      throw new Error(`ordinary bash env cannot set reserved variable "${key}"; use dshEnv`)
+    }
+  }
+  return { ...env, ...ENV_OVERRIDES, ...extra, ...dshEnv }
 }
 
 /** What to run and under which limits (resolved — no defaults in here). */
@@ -96,12 +102,12 @@ export interface SpawnSpec {
    */
   stdin?: string | undefined
   /**
-   * Extra environment entries, merged onto the scrubbed env AFTER the
-   * credential scrub and the model-friendly overrides (so an explicit entry
-   * wins). Set by in-process plugins; the model-facing tool does not forward
-   * model input here.
+   * Ordinary environment entries merged after the credential scrub and
+   * terminal overrides. `DSH_*` names are rejected and belong in `dshEnv`.
    */
   env?: Record<string, string> | undefined
+  /** Harness-owned `DSH_*` entries merged after ambient `DSH_*` removal. */
+  dshEnv?: DshEnvironment | undefined
 }
 
 /**
@@ -346,7 +352,7 @@ export function runBash(spec: SpawnSpec, internals: RunInternals = {}): RunningB
   // typed `spawn` overload infer non-null stdout/stderr, which the
   // `ChildProcessByStdio` annotation captures (stdin `Writable | null`; stdout/
   // stderr the non-null `Readable` the collectors attach to without a cast).
-  const env = childEnv(spec.env)
+  const env = childEnv(spec.env, spec.dshEnv)
   const child: ChildProcessByStdio<Writable | null, Readable, Readable> = spec.stdin !== undefined
     ? spawn('bash', ['-c', spec.command], { cwd: spec.cwd, env, stdio: ['pipe', 'pipe', 'pipe'], detached: true })
     : spawn('bash', ['-c', spec.command], { cwd: spec.cwd, env, stdio: ['ignore', 'pipe', 'pipe'], detached: true })

packages/bash/bash-local/tests/executor.spec.ts

@@ -136,21 +136,28 @@ describe('LocalBashExecutor.run', () => {
     await expect(bash.run(bash.resolve({ command: 'true', workdir: '/nonexistent-dsh' }))).rejects.toThrow(/ENOENT/)
   })
 
-  it('resolve() carries stdin/env onto the spec, and run() threads them to the command', async () => {
+  it('resolve() carries stdin/env/dshEnv onto the spec, and run() threads them to the command', async () => {
     const { bash } = await setup()
-    const spec = bash.resolve({ command: 'cat; echo "[$DSH_SEAM_VAR]"', stdin: 'piped\n', env: { DSH_SEAM_VAR: 'env-ok' } })
-    // resolve() keeps the stdin/env fields verbatim (optional, no default).
+    const spec = bash.resolve({
+      command: 'cat; echo "[$SEAM_VAR][$DSH_SEAM_VAR]"',
+      stdin: 'piped\n',
+      env: { SEAM_VAR: 'env-ok' },
+      dshEnv: { DSH_SEAM_VAR: 'dsh-ok' },
+    })
+    // resolve() keeps the optional input/environment fields verbatim.
     expect(spec.stdin).toBe('piped\n')
-    expect(spec.env).toEqual({ DSH_SEAM_VAR: 'env-ok' })
+    expect(spec.env).toEqual({ SEAM_VAR: 'env-ok' })
+    expect(spec.dshEnv).toEqual({ DSH_SEAM_VAR: 'dsh-ok' })
     const result = await bash.run(spec)
-    expect(result.stdout.text).toBe('piped\n[env-ok]\n')
+    expect(result.stdout.text).toBe('piped\n[env-ok][dsh-ok]\n')
   })
 
-  it('resolve() omits stdin/env when the request supplies neither', async () => {
+  it('resolve() omits stdin/env/dshEnv when the request supplies none', async () => {
     const { bash } = await setup()
     const spec = bash.resolve({ command: 'true' })
     expect('stdin' in spec).toBe(false)
     expect('env' in spec).toBe(false)
+    expect('dshEnv' in spec).toBe(false)
   })
 })
 
@@ -177,14 +184,15 @@ describe('LocalBashExecutor background tasks', () => {
     await Promise.all([first.done, second.done])
   })
 
-  it('threads stdin and extra env into a background task', async () => {
+  it('threads stdin, ordinary env, and managed env into a background task', async () => {
     const { bash } = await setup()
     const task = bash.start(bash.resolve({
-      command: 'cat; echo "[$DSH_BG_VAR]"',
+      command: 'cat; echo "[$BG_VAR][$DSH_BG_VAR]"',
       stdin: 'bg-stdin\n',
-      env: { DSH_BG_VAR: 'bg-env' },
+      env: { BG_VAR: 'bg-env' },
+      dshEnv: { DSH_BG_VAR: 'bg-dsh-env' },
     }))
-    const read = await readUntil(bash, task.id, '[bg-env]')
+    const read = await readUntil(bash, task.id, '[bg-env][bg-dsh-env]')
     expect(read.delta).toContain('bg-stdin')
     await task.done
     expect(task.exitCode).toBe(0)

packages/bash/bash-local/tests/run.spec.ts

@@ -201,19 +201,19 @@ describe('stdin and extra env (set by in-process plugins)', () => {
     expect(piped.stdout.text).toBe('socket\n')
   })
 
-  it('merges extra env entries onto the scrubbed environment', async () => {
-    const result = await runBash(spec('echo "$DSH_EXTRA_ONE/$DSH_EXTRA_TWO"', {
-      env: { DSH_EXTRA_ONE: 'alpha', DSH_EXTRA_TWO: 'beta' },
+  it('merges ordinary extra env entries onto the scrubbed environment', async () => {
+    const result = await runBash(spec('echo "$EXTRA_ONE/$EXTRA_TWO"', {
+      env: { EXTRA_ONE: 'alpha', EXTRA_TWO: 'beta' },
     })).done
     expect(result.stdout.text).toBe('alpha/beta\n')
   })
 
   it('an explicit extra env entry overrides the model-friendly override and the scrub', async () => {
     // TERM is a model-friendly OVERRIDE (dumb); an explicit extra entry wins.
-    // DSH_OVERRIDE_KEY matches the credential scrub pattern, yet an explicit
+    // EXPLICIT_OVERRIDE_KEY matches the credential scrub pattern, yet an explicit
     // entry is still honored — the scrub only drops AMBIENT process.env creds.
-    const result = await runBash(spec('echo "$TERM/$DSH_OVERRIDE_KEY"', {
-      env: { TERM: 'xterm-256color', DSH_OVERRIDE_KEY: 'explicit-wins' },
+    const result = await runBash(spec('echo "$TERM/$EXPLICIT_OVERRIDE_KEY"', {
+      env: { TERM: 'xterm-256color', EXPLICIT_OVERRIDE_KEY: 'explicit-wins' },
     })).done
     expect(result.stdout.text).toBe('xterm-256color/explicit-wins\n')
   })
@@ -361,13 +361,13 @@ describe('abort edge cases', () => {
 })
 
 describe('review fixes: env scrubbing and spill hardening', () => {
-  it('scrubs credential-shaped env vars from child processes', async () => {
+  it('scrubs credential-shaped and ambient DSH env vars from child processes', async () => {
     process.env.DSH_TEST_API_KEY = 'super-secret'
     process.env.DSH_TEST_TOKEN = 'also-secret'
     process.env.DSH_TEST_PLAIN = 'visible'
     try {
       const result = await runBash(spec('echo "[${DSH_TEST_API_KEY:-absent}|${DSH_TEST_TOKEN:-absent}|${DSH_TEST_PLAIN:-absent}]"')).done
-      expect(result.stdout.text.trim()).toBe('[absent|absent|visible]')
+      expect(result.stdout.text.trim()).toBe('[absent|absent|absent]')
     } finally {
       delete process.env.DSH_TEST_API_KEY
       delete process.env.DSH_TEST_TOKEN
@@ -375,6 +375,23 @@ describe('review fixes: env scrubbing and spill hardening', () => {
     }
   })
 
+  it('injects only the current trusted DSH environment after scrubbing ambient values', async () => {
+    process.env.DSH_STALE = 'old-value'
+    try {
+      const result = await runBash(spec('echo "[${DSH_STALE:-absent}|$DSH_SHELL|$DSH_SESSION_ID]"', {
+        dshEnv: { DSH_SHELL: '1', DSH_SESSION_ID: 'current-session' },
+      })).done
+      expect(result.stdout.text.trim()).toBe('[absent|1|current-session]')
+    } finally {
+      delete process.env.DSH_STALE
+    }
+  })
+
+  it('rejects DSH variables on the ordinary env channel', () => {
+    expect(() => runBash(spec('true', { env: { DSH_WRONG_CHANNEL: 'bad' } })))
+      .toThrow(/DSH_WRONG_CHANNEL.*dshEnv/)
+  })
+
   it('creates spill files with owner-only permissions and random names', async () => {
     const result = await runBash(
       spec('for i in $(seq 1 200); do printf "line-%04d\\n" $i; done', { maxOutputBytes: 500 }),

packages/bash/bash/README.md

@@ -30,8 +30,8 @@ Implementations subclass `BashExecutor`, implement the abstract methods, and cal
 
 ## Vocabulary
 
-`BashExecRequest` (command, workdir?, timeoutMs?, signal?, stdin?, env?, owner?, sandboxMode?) resolves to `BashExecSpec` (command, workdir, timeoutMs, signal?, stdin?, env?, owner, sandboxMode) before execution; `owner` and `sandboxMode` are optional on the request and **required-but-nullable** on the resolved spec, so a forgotten one is a visible `undefined` rather than a silently-absent property. `sandboxMode` is the explicit per-call sandbox-policy input: an escalation grant a human just issued ([the sandbox RFC § Escalation](../../../docs/rfc/implemented/feature/2026-07-06-sandbox.md), which outranks) or the session's standing override ([the sandbox RFC § Per-session mode switching](../../../docs/rfc/implemented/feature/2026-07-06-sandbox.md)); a sandboxing executor's `resolve()` stamps its configured default when the request carries none, and a non-sandboxing executor carries the field verbatim and confines nothing.
+`BashExecRequest` (command, workdir?, timeoutMs?, signal?, stdin?, env?, dshEnv?, owner?, sandboxMode?) resolves to `BashExecSpec` (command, workdir, timeoutMs, signal?, stdin?, env?, dshEnv?, owner, sandboxMode) before execution; `owner` and `sandboxMode` are optional on the request and **required-but-nullable** on the resolved spec, so a forgotten one is a visible `undefined` rather than a silently-absent property. `sandboxMode` is the explicit per-call sandbox-policy input: an escalation grant a human just issued ([the sandbox RFC § Escalation](../../../docs/rfc/implemented/feature/2026-07-06-sandbox.md), which outranks) or the session's standing override ([the sandbox RFC § Per-session mode switching](../../../docs/rfc/implemented/feature/2026-07-06-sandbox.md)); a sandboxing executor's `resolve()` stamps its configured default when the request carries none, and a non-sandboxing executor carries the field verbatim and confines nothing.
 
 The seam also owns the per-session mode override vocabulary (the sandbox RFC § Per-session mode switching): the log-only `'bash/sandbox-mode'` session event, the pure fold `effectiveSandboxMode(events)` (last event wins; `undefined` means "apply the executor default"), and THE write path `setSandboxMode(session, mode)` — the session log is the store, so an override survives restart by replay and two sessions can never see each other's mode. Writers must respect turn-enclosure: the ACP bridge anchors an idle switch at the next turn rather than appending between turns. 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. A sandboxing executor additionally stamps `sandbox` result facts on results and settled tasks (`BashSandboxInfo`: the mode it executed under, the conservative `denied` classification, and — for confined modes — the backend's `enforcement` completeness); the mode/enforcement vocabulary is owned by the [`dsh-sandbox`](../../sandbox/sandbox/) seam, and the facts are documented in [core-data-structures/bash.md](../../../docs/core-data-structures/bash.md). See `src/types.ts` for the full contracts.
 
-`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).
+`stdin` and ordinary `env` are set by in-process plugins (the hooks bridges, native plugins) to feed a hook command its JSON payload and `CLAUDE_PROJECT_DIR`/`CLAUDE_PLUGIN_ROOT` values. `dshEnv` is a separate trusted overlay restricted by type to `DSH_*` keys; model bash uses it for the current snapshot collected by `ctx.bashEnv`. Implementations remove inherited `DSH_*`, reject those names in ordinary `env`, then merge `dshEnv`, so an omitted current fact cannot fall back to stale ambient state. The model-facing tool exposes none of these as parameters. All three remain optional on the resolved spec; absent means no input/overlay. See [the bash-stdin-env RFC](../../../docs/rfc/implemented/architecture/2026-06-30-bash-stdin-env-trusted-plugin-surface.md) and [the session environment RFC](../../../docs/rfc/implemented/feature/2026-07-10-agent-session-identity-and-log-location.md).

packages/bash/bash/src/index.ts

@@ -30,6 +30,7 @@ export type {
   BashTaskRead,
   BashTaskStatus,
   CollectedOutput,
+  DshEnvironment,
 } from './types.ts'
 
 declare module 'cordis' {

packages/bash/bash/src/types.ts

@@ -12,6 +12,9 @@ import type { SandboxEnforcement, SandboxMode } from '@deepseek-ai/dsh-sandbox'
 /** Identifies one background task within an executor (generated `bash-N`). */
 export type BashTaskId = Branded<'BashTaskId'>
 
+/** Trusted DeepSeek Harness variables for one bash execution. */
+export type DshEnvironment = Readonly<Record<`DSH_${string}`, string>>
+
 /**
  * Brand a string as a {@link BashTaskId}.
  * @param id - the raw task-id string (the executor generates `bash-N`).
@@ -106,15 +109,19 @@ export interface BashExecRequest {
    */
   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 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`).
+   * Ordinary environment entries for the command, merged after the credential
+   * scrub. `DSH_*` is reserved for {@link dshEnv} and implementations reject it
+   * here. 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.
    */
   env?: Record<string, string> | undefined
+  /**
+   * Harness-owned `DSH_*` variables for this execution. Executors discard
+   * ambient `DSH_*` entries before merging this snapshot, so an unavailable
+   * current fact cannot inherit a stale value from the harness process.
+   */
+  dshEnv?: DshEnvironment | undefined
   /**
    * Opaque OWNER token for a background task — the consumer's isolation key
    * (the tool layer passes the owning agent's `session.header.id`). The
@@ -163,13 +170,14 @@ export interface BashExecSpec {
    */
   stdin?: string | undefined
   /**
-   * Extra environment entries, carried through verbatim from
-   * {@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".
+   * Ordinary environment entries carried through from
+   * {@link BashExecRequest.env}. `DSH_*` remains reserved for {@link dshEnv}.
+   * OPTIONAL on the spec for the same reason as `stdin`: absent means no
+   * ordinary extra environment.
    */
   env?: Record<string, string> | undefined
+  /** Trusted `DSH_*` snapshot carried through from {@link BashExecRequest.dshEnv}. */
+  dshEnv?: DshEnvironment | undefined
   /**
    * Opaque owner token, REQUIRED-but-nullable (mirrors `workdir`/`timeoutMs`
    * being required on the resolved spec): {@link BashExecutor.resolve} carries

packages/bash/tool-bash/README.md

@@ -22,11 +22,26 @@ The plugin also contributes the `tool:bash` prompt section (order 105) — the c
 
 `command`, `workdir`, and `timeoutMs` are resolved against the executor's config defaults via `ctx.bash.resolve()` before execution, so the executor seam (`BashExecSpec`) receives explicit `workdir`/`timeoutMs` values. The workdir default is applied in the tool layer (from the calling agent's `session.header.cwd`) BEFORE `resolve()` — the per-session cwd must come from `exec.agent`, since N sessions share one executor; only when no session cwd is available does the executor fall back to its own config / `process.cwd()`.
 
-### Session identity environment
+### Managed shell environment
 
-Every foreground and background call made for an agent receives `DSH_SESSION_ID=agent.session.header.id`. When the active persistence backend locates a JSONL artifact, the call also receives `DSH_SESSION_JSONL=<absolute target path>`; absent persistence and non-file backends still provide the id but omit the JSONL variable. The path is a location hint: lazy materialization means it may not exist on the first turn, and during an open turn it can omit buffered events that have not reached `session/flush`. Neither value is an authorization credential.
+Every foreground and background model bash call receives a newly collected trusted `DSH_*` environment. `DSH_HOME` is the absolute Harness home (`dshHome` config, then ambient `$DSH_HOME`, then `~/.dsh`) and `DSH_SHELL=1` identifies the managed child. Agent calls additionally receive `DSH_SESSION_ID=agent.session.header.id`; when the active persistence seam locates a JSONL artifact they also receive `DSH_SESSION_JSONL=<absolute target path>`. The JSONL path is a location hint: it may not exist before the first flush or contain the current buffered turn, and it is not an authorization credential.
 
-The overlay is computed from `ToolExecution.agent` for each call and passed through `BashExecRequest.env`; `process.env` is never modified, so concurrent parent/child agents keep separate values. The tool description names both variables so the model can inspect them without a permanent system-prompt section.
+`ctx.bashEnv` owns collection. Other plugins can register an effect-scoped contributor with a stable name, declared keys/descriptions, and `resolve(execution: ToolExecution)`; duplicate ownership and undeclared runtime keys fail loudly, while `list()` enumerates declarations without executing providers. Harness built-ins reserve `DSH_HOME`, `DSH_SHELL`, and `DSH_SESSION_ID`; tool-bash's persistence translator owns `DSH_SESSION_JSONL` by reading the backend-neutral `sessionPersistence.locate()` seam.
+
+```ts
+import type { Context } from 'cordis'
+import type {} from '@deepseek-ai/dsh-tool-bash'
+
+export function apply(ctx: Context): void {
+  ctx.bashEnv.register({
+    name: 'deployment-region',
+    variables: { DSH_DEPLOYMENT_REGION: { description: 'Current deployment region.' } },
+    resolve: execution => execution.agent === undefined ? {} : { DSH_DEPLOYMENT_REGION: 'cn-north' },
+  })
+}
+```
+
+The overlay is computed from the current `ToolExecution` and passed through the dedicated `BashExecRequest.dshEnv` channel. The local executor removes all inherited `DSH_*` before merging that snapshot, so nested harnesses and concurrent parent/child agents cannot leak stale identities. `process.env` is never modified. The tool description teaches the generic `$DSH_*` convention rather than naming persistence-specific variables or adding a permanent system-prompt section.
 
 Result text: stdout, then a `[stderr]` section, then status markers — `[sandbox: file access denied under <mode> mode]` when a sandboxing executor classified the failure as a policy denial (reported first so `[exit code: N]` stays the last line; the static description tells the model a denial is policy, not a command bug, and forbids retrying around it), `[timed out after Nms]` whenever the executor's timer fired (reported independently of how the process ended, so a command that traps SIGTERM and exits 0 still shows it), `[killed by signal: …]` for a signal death, `[exit code: N]` for a non-zero exit (reported, **not** `isError`: the model decides how to react), and `[output truncated; full output: <path>]` when the tail was kept and a safe spill file is available. If the executor knows output was dropped but cannot safely advertise a complete spill file, the path is reported as `(unavailable)`. Only infrastructure failures (spawn errors, aborts) surface as `isError` results.
 
@@ -52,7 +67,7 @@ When a background task finishes, a short notice is injected into the owning agen
 
 ## The tool builds its request from named args only
 
-The `BashExecRequest` seam carries optional `stdin` and `env`, used by trusted consumers. This tool does **not** expose them as model parameters: it builds the request from named schema fields and adds only the session overlay above, so model-supplied `env`/`stdin` keys are ignored and cannot replace the trusted values. 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 ambient secrets is `dsh-bash-local`'s credential scrub. Regression guards assert extra model fields never enter the request while the trusted overlay still does. See [the bash-stdin-env RFC](../../../docs/rfc/implemented/architecture/2026-06-30-bash-stdin-env-trusted-plugin-surface.md).
+The `BashExecRequest` seam carries optional `stdin` and ordinary `env` for in-process consumers plus the harness-owned `dshEnv` channel above. This tool does **not** expose any of them as model parameters: it builds the request from named schema fields, so model-supplied `env`/`stdin` keys are ignored and cannot replace the managed values. A model already has equivalent command-local power through shell syntax (`FOO=bar cmd`, a heredoc); ambient-secret protection comes from `dsh-bash-local`'s credential scrub, while `dshEnv` ownership prevents stale or spoofed Harness context. See [the bash-stdin-env RFC](../../../docs/rfc/implemented/architecture/2026-06-30-bash-stdin-env-trusted-plugin-surface.md).
 
 ## Permissions and escalation
 

packages/bash/tool-bash/package.json

@@ -32,6 +32,9 @@
     "@deepseek-ai/dsh-tools": "^0.0.1",
     "cordis": "^4.0.0-rc.6"
   },
+  "dependencies": {
+    "schemastery": "^3.18.0"
+  },
   "devDependencies": {
     "@deepseek-ai/dsh-agent": "workspace:^",
     "@deepseek-ai/dsh-agent-loop": "workspace:^",

packages/bash/tool-bash/src/index.ts

@@ -55,8 +55,10 @@
  * @module @deepseek-ai/dsh-tool-bash
  */
 
-import type { Context } from 'cordis'
-import { isAbsolute, resolve as resolvePath } from 'node:path'
+import { Service, type Context } from 'cordis'
+import z from 'schemastery'
+import { homedir } from 'node:os'
+import { isAbsolute, join, resolve as resolvePath } from 'node:path'
 import { defineTool } from '@deepseek-ai/dsh-tools'
 import type { GenericCallView, TerminalCallView, ToolExecution, ToolResult, ToolResultView } from '@deepseek-ai/dsh-tools'
 import type { Agent } from '@deepseek-ai/dsh-agent'
@@ -69,11 +71,178 @@ import type {} from '@deepseek-ai/dsh-system-prompt'
 import type {} from '@deepseek-ai/dsh-user-approval'
 import type { SandboxMode } from '@deepseek-ai/dsh-sandbox'
 import { BashTaskId, OwnerToken, effectiveSandboxMode } from '@deepseek-ai/dsh-bash'
-import type { BashRunResult, BashTask, CollectedOutput } from '@deepseek-ai/dsh-bash'
+import type { BashRunResult, BashTask, CollectedOutput, DshEnvironment } from '@deepseek-ai/dsh-bash'
+
+declare module 'cordis' {
+  interface Context {
+    bashEnv: BashEnvRegistry
+  }
+}
 
 export const name = 'tool-bash'
 export const inject = ['tools', 'bash', 'systemPrompt']
 
+/** Configuration for the bash tool and its managed child environment. */
+export interface Config {
+  /** DeepSeek Harness home directory exposed as `DSH_HOME`; defaults to `$DSH_HOME` or `~/.dsh`. */
+  dshHome?: string
+}
+
+/** Runtime configuration schema for the bash tool plugin. */
+export const Config: z<Config> = z.object({
+  dshHome: z.string(),
+})
+
+/** Model-visible metadata for one managed `DSH_*` environment variable. */
+export interface BashEnvVariable {
+  /** Concise description of the environment fact represented by the variable. */
+  description: string
+}
+
+/**
+ * A plugin contribution to the managed environment of each model bash call.
+ * Declared keys make ownership conflicts detectable before the first command;
+ * `resolve` computes only the values available for the current execution.
+ */
+export interface BashEnvContributor {
+  /** Stable contributor name used in diagnostics and duplicate detection. */
+  name: string
+  /** Complete set of `DSH_*` keys this contributor may return. */
+  variables: Readonly<Record<`DSH_${string}`, BashEnvVariable>>
+  /**
+   * Resolve this contributor's available values for one tool execution.
+   * @param execution - the bash tool execution and its optional calling agent.
+   * @returns a partial map containing only keys declared in {@link variables}.
+   */
+  resolve(execution: ToolExecution): Readonly<Partial<Record<`DSH_${string}`, string>>>
+}
+
+/** An enumerable declaration returned by {@link BashEnvRegistry.list}. */
+export interface BashEnvVariableInfo extends BashEnvVariable {
+  /** Contributor that owns the variable. */
+  contributor: string
+  /** Declared `DSH_*` environment variable name. */
+  key: `DSH_${string}`
+}
+
+const RESERVED_BASH_ENV_KEYS = new Set<`DSH_${string}`>([
+  'DSH_HOME',
+  'DSH_SHELL',
+  'DSH_SESSION_ID',
+])
+const BASH_ENV_KEY = /^DSH_[A-Z][A-Z0-9_]*$/
+
+/**
+ * Registry (`ctx.bashEnv`) for trusted, per-execution `DSH_*` variables.
+ * The namespace is rebuilt for every model bash call: ambient `DSH_*` values
+ * are discarded by the executor, then the registry's current snapshot is
+ * injected. Built-in shell facts remain owned by the registry itself while
+ * plugins can register additional, enumerable facts with effect-scoped
+ * disposal.
+ */
+export class BashEnvRegistry extends Service {
+  private readonly contributors = new Map<string, BashEnvContributor>()
+  private readonly keyOwners = new Map<`DSH_${string}`, string>()
+  private readonly dshHome: string
+
+  /**
+   * Create and install the `ctx.bashEnv` service.
+   * @param ctx - Cordis context that owns the service and registrations.
+   * @param config - home-directory configuration for the built-in variables.
+   */
+  constructor(ctx: Context, config: Config = {}) {
+    super(ctx, 'bashEnv')
+    this.dshHome = resolvePath(config.dshHome ?? process.env.DSH_HOME ?? join(homedir(), '.dsh'))
+  }
+
+  /**
+   * Register one environment contributor. Names and keys are unique; built-in
+   * keys are reserved. Registration is disposed with the calling plugin fiber.
+   * @param contributor - declared key ownership and per-execution resolver.
+   * @returns the disposer that unregisters the contribution.
+   */
+  register(contributor: BashEnvContributor): () => void {
+    const dispose = this.ctx.effect(function* (this: BashEnvRegistry) {
+      if (contributor.name.trim().length === 0) {
+        throw new Error('bash env contributor name must be non-empty')
+      }
+      if (this.contributors.has(contributor.name)) {
+        throw new Error(`bash env contributor "${contributor.name}" is already registered`)
+      }
+
+      const variables = Object.entries(contributor.variables) as [`DSH_${string}`, BashEnvVariable][]
+      for (const [key, variable] of variables) {
+        if (!BASH_ENV_KEY.test(key)) {
+          throw new Error(`bash env contributor "${contributor.name}" declared invalid key "${key}"`)
+        }
+        if (RESERVED_BASH_ENV_KEYS.has(key)) {
+          throw new Error(`bash env contributor "${contributor.name}" cannot own reserved key "${key}"`)
+        }
+        if (variable.description.trim().length === 0) {
+          throw new Error(`bash env contributor "${contributor.name}" must describe "${key}"`)
+        }
+        const owner = this.keyOwners.get(key)
+        if (owner !== undefined) {
+          throw new Error(`bash env key "${key}" is already owned by contributor "${owner}"; contributor "${contributor.name}" cannot also own it`)
+        }
+      }
+
+      this.contributors.set(contributor.name, contributor)
+      for (const [key] of variables) this.keyOwners.set(key, contributor.name)
+      yield () => {
+        this.contributors.delete(contributor.name)
+        for (const [key] of variables) this.keyOwners.delete(key)
+      }
+    }.bind(this), 'bashEnv.register()')
+    return () => void dispose()
+  }
+
+  /**
+   * Build the trusted `DSH_*` snapshot for one bash tool execution.
+   * @param execution - the current tool execution.
+   * @returns an immutable environment overlay containing built-ins and current contributions.
+   */
+  collect(execution: ToolExecution): DshEnvironment {
+    const values: Record<`DSH_${string}`, string> = {
+      DSH_HOME: this.dshHome,
+      DSH_SHELL: '1',
+    }
+    if (execution.agent !== undefined) {
+      values.DSH_SESSION_ID = execution.agent.session.header.id
+    }
+
+    for (const contributor of [...this.contributors.values()].sort((left, right) => left.name.localeCompare(right.name))) {
+      const resolved = contributor.resolve(execution)
+      for (const [rawKey, value] of Object.entries(resolved)) {
+        const key = rawKey as `DSH_${string}`
+        if (!Object.hasOwn(contributor.variables, key)) {
+          throw new Error(`bash env contributor "${contributor.name}" returned undeclared key "${key}"`)
+        }
+        if (typeof value !== 'string') {
+          throw new Error(`bash env contributor "${contributor.name}" returned a non-string value for "${key}"`)
+        }
+        values[key] = value
+      }
+    }
+
+    return Object.freeze(Object.fromEntries(Object.entries(values).sort(([left], [right]) => left.localeCompare(right))))
+  }
+
+  /**
+   * Enumerate plugin-contributed variables without executing their resolvers.
+   * @returns declarations sorted by environment variable name.
+   */
+  list(): BashEnvVariableInfo[] {
+    return [...this.contributors.values()]
+      .flatMap(contributor => Object.entries(contributor.variables).map(([key, variable]) => ({
+        contributor: contributor.name,
+        description: variable.description,
+        key: key as `DSH_${string}`,
+      })))
+      .sort((left, right) => left.key.localeCompare(right.key))
+  }
+}
+
 /**
  * Validate the constraints the SchemaSpec can't express. `defineTool` now
  * validates parsed args against the SchemaSpec before `execute` runs (the
@@ -168,8 +337,7 @@ function bashDescription(escalationModes: readonly SandboxMode[]): string {
   const base = 'Execute a bash command (`bash -c`) and return its stdout/stderr. '
     + 'Each call runs in a fresh shell: no state (cwd, variables, functions) persists between calls — '
     + 'pass `workdir` instead of using `cd`. Non-zero exits are reported as `[exit code: N]`. '
-    + 'The current agent session id is available as `$DSH_SESSION_ID`; when JSONL persistence is configured, '
-    + '`$DSH_SESSION_JSONL` is its absolute target path and may not exist or contain the current unflushed turn yet. '
+    + 'Current harness environment facts are exposed through managed `$DSH_*` variables; inspect them when needed. '
     + 'Commands may run under a file sandbox; a blocked file operation is reported as `[sandbox: file access denied under <mode> mode]` — a policy denial, not a bug in the command; do not retry another way (a background task reports the same marker via bash_output once it has finished). '
     + 'Long output is truncated to its tail; the full output is saved to a file whose path is reported when available. '
     + 'Set `run_in_background: true` for long-running commands: the call returns a task id immediately; '
@@ -397,22 +565,6 @@ function resolveWorkdir(modelWorkdir: string | undefined, exec: { agent?: Agent
   return modelWorkdir
 }
 
-/**
- * Build the trusted per-execution session environment. Identity always comes
- * from the calling agent's immutable session header; an optional JSONL path
- * comes from the active persistence backend's side-effect-free locator. A
- * non-agent caller has no current session, so it receives neither variable.
- */
-function sessionEnvironment(ctx: Context, exec: { agent?: Agent }): Record<string, string> | undefined {
-  const agent = exec.agent
-  if (agent === undefined) return undefined
-
-  const env: Record<string, string> = { DSH_SESSION_ID: agent.session.header.id }
-  const location = ctx.get('sessionPersistence')?.locate(agent.session.header)
-  if (location?.kind === 'jsonl') env.DSH_SESSION_JSONL = location.path
-  return env
-}
-
 /** Status line for background task reads. */
 function statusLine(task: BashTask): string {
   switch (task.status) {
@@ -422,7 +574,23 @@ function statusLine(task: BashTask): string {
   }
 }
 
-export function apply(ctx: Context): void {
+export function apply(ctx: Context, config: Config = {}): void {
+  const bashEnv = new BashEnvRegistry(ctx, config)
+  bashEnv.register({
+    name: 'session-persistence',
+    variables: {
+      DSH_SESSION_JSONL: {
+        description: 'Absolute target path of the current session JSONL when the active persistence backend provides one.',
+      },
+    },
+    resolve(execution) {
+      const agent = execution.agent
+      if (agent === undefined) return {}
+      const location = ctx.get('sessionPersistence')?.locate(agent.session.header)
+      return location?.kind === 'jsonl' ? { DSH_SESSION_JSONL: location.path } : {}
+    },
+  })
+
   // The bash tools' cross-call HABIT, which the per-tool descriptions cannot
   // carry (they describe one call each): the exit-code marker is only useful
   // if the model actually checks it every time.
@@ -614,13 +782,13 @@ export function apply(ctx: Context): void {
       // session runs in its own workspace (see resolveWorkdir); an explicit
       // model workdir still wins.
       const workdir = resolveWorkdir(args.workdir, exec)
-      const env = sessionEnvironment(ctx, exec)
+      const dshEnv = bashEnv.collect(exec)
       const request = {
         command: args.command,
         ...workdir !== undefined ? { workdir } : {},
         ...args.timeoutMs !== undefined ? { timeoutMs: args.timeoutMs } : {},
         ...exec.signal ? { signal: exec.signal } : {},
-        ...env !== undefined ? { env } : {},
+        dshEnv,
         ...sandboxMode !== undefined ? { sandboxMode } : {},
       }
       if (args.run_in_background === true) {

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

@@ -0,0 +1,189 @@
+import { homedir } from 'node:os'
+import { join, resolve } from 'node:path'
+import { afterEach, describe, expect, it, vi } from 'vitest'
+import { Context } from 'cordis'
+import { CallId } from '@deepseek-ai/dsh-llm'
+import type { Agent } from '@deepseek-ai/dsh-agent'
+import type { ToolExecution } from '@deepseek-ai/dsh-tools'
+import { BashEnvRegistry } from '@deepseek-ai/dsh-tool-bash'
+
+afterEach(() => vi.unstubAllEnvs())
+
+function execution(sessionId?: string): ToolExecution {
+  return {
+    callId: CallId('bash-env-call'),
+    name: 'bash',
+    arguments: { command: 'true' },
+    ...(sessionId === undefined
+      ? {}
+      : { agent: { session: { header: { version: 0, id: sessionId, createdAt: 0 } } } as Agent }),
+  }
+}
+
+describe('BashEnvRegistry', () => {
+  it('collects unconditional shell facts and the current agent session id', () => {
+    const ctx = new Context()
+    const registry = new BashEnvRegistry(ctx, { dshHome: './test-dsh-home' })
+
+    expect(registry.collect(execution())).toEqual({
+      DSH_HOME: resolve('./test-dsh-home'),
+      DSH_SHELL: '1',
+    })
+    expect(registry.collect(execution('session-a'))).toEqual({
+      DSH_HOME: resolve('./test-dsh-home'),
+      DSH_SESSION_ID: 'session-a',
+      DSH_SHELL: '1',
+    })
+  })
+
+  it('resolves DSH_HOME from the ambient override or the user-home default', () => {
+    vi.stubEnv('DSH_HOME', './ambient-dsh-home')
+    const fromEnvironment = new BashEnvRegistry(new Context())
+    expect(fromEnvironment.collect(execution()).DSH_HOME).toBe(resolve('./ambient-dsh-home'))
+
+    vi.stubEnv('DSH_HOME', undefined)
+    const fromDefault = new BashEnvRegistry(new Context())
+    expect(fromDefault.collect(execution()).DSH_HOME).toBe(join(homedir(), '.dsh'))
+  })
+
+  it('collects declared contributor variables and omits unavailable values', () => {
+    const ctx = new Context()
+    const registry = new BashEnvRegistry(ctx, { dshHome: './test-dsh-home' })
+    registry.register({
+      name: 'optional-session-fact',
+      variables: {
+        DSH_SESSION_OPTIONAL: { description: 'Optional session-scoped test fact.' },
+      },
+      resolve: exec => exec.agent === undefined ? {} : { DSH_SESSION_OPTIONAL: exec.agent.session.header.id },
+    })
+    registry.register({
+      name: 'always-available-fact',
+      variables: {
+        DSH_ALWAYS_AVAILABLE: { description: 'Always-available test fact.' },
+      },
+      resolve: () => ({ DSH_ALWAYS_AVAILABLE: 'yes' }),
+    })
+
+    expect(registry.collect(execution())).not.toHaveProperty('DSH_SESSION_OPTIONAL')
+    expect(registry.collect(execution()).DSH_ALWAYS_AVAILABLE).toBe('yes')
+    expect(registry.collect(execution('session-b')).DSH_SESSION_OPTIONAL).toBe('session-b')
+    expect(registry.list()).toEqual([
+      {
+        contributor: 'always-available-fact',
+        description: 'Always-available test fact.',
+        key: 'DSH_ALWAYS_AVAILABLE',
+      },
+      {
+        contributor: 'optional-session-fact',
+        description: 'Optional session-scoped test fact.',
+        key: 'DSH_SESSION_OPTIONAL',
+      },
+    ])
+  })
+
+  it('rejects duplicate variable ownership at registration time', () => {
+    const ctx = new Context()
+    const registry = new BashEnvRegistry(ctx, { dshHome: './test-dsh-home' })
+    registry.register({
+      name: 'first',
+      variables: { DSH_SHARED: { description: 'First owner.' } },
+      resolve: () => ({ DSH_SHARED: 'first' }),
+    })
+
+    expect(() => registry.register({
+      name: 'second',
+      variables: { DSH_SHARED: { description: 'Second owner.' } },
+      resolve: () => ({ DSH_SHARED: 'second' }),
+    })).toThrow(/DSH_SHARED.*first.*second|DSH_SHARED.*second.*first/)
+  })
+
+  it('rejects duplicate contributor names and malformed declarations', () => {
+    const registry = new BashEnvRegistry(new Context(), { dshHome: './test-dsh-home' })
+    registry.register({
+      name: 'declared',
+      variables: { DSH_DECLARED: { description: 'Declared fact.' } },
+      resolve: () => ({}),
+    })
+
+    expect(() => registry.register({
+      name: 'declared',
+      variables: { DSH_ANOTHER: { description: 'Another fact.' } },
+      resolve: () => ({}),
+    })).toThrow(/already registered/)
+    expect(() => registry.register({
+      name: ' ',
+      variables: { DSH_BLANK_NAME: { description: 'Blank owner.' } },
+      resolve: () => ({}),
+    })).toThrow(/name must be non-empty/)
+    expect(() => registry.register({
+      name: 'invalid-key',
+      variables: { dsh_invalid: { description: 'Invalid key.' } } as unknown as Record<'DSH_INVALID', { description: string }>,
+      resolve: () => ({}),
+    })).toThrow(/invalid key/)
+    expect(() => registry.register({
+      name: 'reserved-key',
+      variables: { DSH_HOME: { description: 'Reserved key.' } },
+      resolve: () => ({}),
+    })).toThrow(/reserved key/)
+    expect(() => registry.register({
+      name: 'blank-description',
+      variables: { DSH_BLANK_DESCRIPTION: { description: ' ' } },
+      resolve: () => ({}),
+    })).toThrow(/must describe/)
+  })
+
+  it('rejects undeclared variables returned by a contributor', () => {
+    const ctx = new Context()
+    const registry = new BashEnvRegistry(ctx, { dshHome: './test-dsh-home' })
+    registry.register({
+      name: 'drifted-provider',
+      variables: { DSH_DECLARED: { description: 'Declared fact.' } },
+      resolve: () => ({ DSH_UNDECLARED: 'bad' }),
+    })
+
+    expect(() => registry.collect(execution())).toThrow(/drifted-provider.*DSH_UNDECLARED/)
+  })
+
+  it('rejects non-string values returned by a contributor', () => {
+    const registry = new BashEnvRegistry(new Context(), { dshHome: './test-dsh-home' })
+    registry.register({
+      name: 'wrong-value-type',
+      variables: { DSH_STRING: { description: 'String fact.' } },
+      resolve: () => ({ DSH_STRING: 42 }) as unknown as Record<'DSH_STRING', string>,
+    })
+
+    expect(() => registry.collect(execution())).toThrow(/wrong-value-type.*non-string.*DSH_STRING/)
+  })
+
+  it('removes an effect-scoped contributor when its plugin is disposed', async () => {
+    const ctx = new Context()
+    const registry = new BashEnvRegistry(ctx, { dshHome: './test-dsh-home' })
+    const fiber = await ctx.plugin({
+      inject: ['bashEnv'],
+      apply(inner: Context) {
+        inner.bashEnv.register({
+          name: 'temporary',
+          variables: { DSH_TEMPORARY: { description: 'Temporary fact.' } },
+          resolve: () => ({ DSH_TEMPORARY: 'present' }),
+        })
+      },
+    })
+
+    expect(registry.collect(execution()).DSH_TEMPORARY).toBe('present')
+    await fiber.dispose()
+    expect(registry.collect(execution())).not.toHaveProperty('DSH_TEMPORARY')
+  })
+
+  it('returns an explicit contributor disposer', () => {
+    const registry = new BashEnvRegistry(new Context(), { dshHome: './test-dsh-home' })
+    const dispose = registry.register({
+      name: 'explicit-disposal',
+      variables: { DSH_EXPLICIT_DISPOSAL: { description: 'Explicitly disposed fact.' } },
+      resolve: () => ({ DSH_EXPLICIT_DISPOSAL: 'present' }),
+    })
+
+    expect(registry.collect(execution()).DSH_EXPLICIT_DISPOSAL).toBe('present')
+    dispose()
+    expect(registry.collect(execution())).not.toHaveProperty('DSH_EXPLICIT_DISPOSAL')
+  })
+})

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

@@ -1,4 +1,4 @@
-import { afterEach, describe, expect, it } from 'vitest'
+import { afterEach, describe, expect, it, vi } from 'vitest'
 import { Context } from 'cordis'
 import { existsSync, mkdtempSync, readFileSync, rmSync } from 'node:fs'
 import { tmpdir } from 'node:os'
@@ -21,7 +21,7 @@ import { MockAdapter, textResponse, toolCallResponse } from '../../../core/agent
  * through the agent loop, exercising the same seams a live model would
  * (tool/call + tool/result session events, agent.inject notifications).
  */
-async function harness(adapter: MockAdapter, sessionRoot?: string) {
+async function harness(adapter: MockAdapter, sessionRoot?: string, dshHome?: string) {
   const ctx = new Context()
   await ctx.plugin(LlmService)
   await ctx.plugin(SessionStore)
@@ -31,13 +31,16 @@ async function harness(adapter: MockAdapter, sessionRoot?: string) {
   await ctx.plugin(AgentRegistry)
   await ctx.plugin(AgentLoop, { agents: [] })
   await ctx.plugin(LocalBashExecutor, { timeoutMs: 10_000 })
-  await ctx.plugin(ToolBash)
+  await ctx.plugin(ToolBash, dshHome === undefined ? {} : { dshHome })
   ctx.llm.registerAdapter(['mock'], adapter)
   return ctx
 }
 
 const dirs: string[] = []
-afterEach(() => { for (const dir of dirs.splice(0)) rmSync(dir, { recursive: true, force: true }) })
+afterEach(() => {
+  vi.unstubAllEnvs()
+  for (const dir of dirs.splice(0)) rmSync(dir, { recursive: true, force: true })
+})
 
 function waitForIdle(ctx: Context, agent: ReactLoopAgent): Promise<void> {
   return new Promise((resolve) => {
@@ -79,14 +82,16 @@ describe('bash tool through the agent loop', () => {
   it('first-turn bash receives session identity before the lazy JSONL file materializes', async () => {
     const root = mkdtempSync(join(tmpdir(), 'dsh-bash-session-env-'))
     dirs.push(root)
+    const dshHome = join(root, 'dsh-home')
+    vi.stubEnv('DSH_STALE_PARENT', 'stale')
     const adapter = new MockAdapter([
       toolCallResponse('call-1', 'bash', {
-        command: 'printf \'%s\\n%s\\n\' "$DSH_SESSION_ID" "$DSH_SESSION_JSONL"; if [ -e "$DSH_SESSION_JSONL" ]; then printf \'present\\n\'; else printf \'absent\\n\'; fi',
+        command: 'printf \'%s\\n%s\\n%s\\n%s\\n%s\\n\' "$DSH_HOME" "$DSH_SHELL" "$DSH_SESSION_ID" "$DSH_SESSION_JSONL" "${DSH_STALE_PARENT-unset}"; if [ -e "$DSH_SESSION_JSONL" ]; then printf \'present\\n\'; else printf \'absent\\n\'; fi',
         description: 'inspect session environment',
       }),
       textResponse('Session environment inspected.'),
     ])
-    const ctx = await harness(adapter, root)
+    const ctx = await harness(adapter, root, dshHome)
     const handle = ctx.agents.create({
       agentId: AgentId('session-env'),
       sessionId: SessionId('session-env-id'),
@@ -100,7 +105,7 @@ describe('bash tool through the agent loop', () => {
     await waitForIdle(ctx, agent)
 
     const result = findEvent(events(agent), 'tool/result')
-    expect(resultText(result)).toBe(`session-env-id\n${location?.path}\nabsent\n`)
+    expect(resultText(result)).toBe(`${dshHome}\n1\nsession-env-id\n${location?.path}\nunset\nabsent\n`)
     expect(existsSync(location!.path)).toBe(true)
     const header = JSON.parse(readFileSync(location!.path, 'utf8').split('\n')[0]!) as { type: string; id: string }
     expect(header).toMatchObject({ type: 'session', id: 'session-env-id' })

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

@@ -892,6 +892,8 @@ describe('tool-owned UI presentation (presentCall / presentResult)', () => {
 })
 
 describe('the model-facing bash tool builds its request from named args only (no {...args} forward)', () => {
+  const recordingDshHome = join(spillDir, 'dsh-home')
+
   /**
    * Records every {@link BashExecRequest} the consumer hands to `resolve()`, so a
    * test can assert what the model-facing tool DID and DID NOT forward. The `bash`
@@ -899,7 +901,7 @@ describe('the model-facing bash tool builds its request from named args only (no
    * 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
+   * model input into the ordinary `env` channel — 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.
@@ -915,6 +917,7 @@ describe('the model-facing bash tool builds its request from named args only (no
         ...request.signal ? { signal: request.signal } : {},
         ...request.stdin !== undefined ? { stdin: request.stdin } : {},
         ...request.env !== undefined ? { env: request.env } : {},
+        ...request.dshEnv !== undefined ? { dshEnv: request.dshEnv } : {},
         owner: request.owner,
         sandboxMode: request.sandboxMode,
       }
@@ -943,15 +946,15 @@ describe('the model-facing bash tool builds its request from named args only (no
       await ctx.plugin(SessionPersistenceJsonl, { root: join(spillDir, 'jsonl') })
     }
     await ctx.plugin(RecordingBashExecutor)
-    await ctx.plugin(ToolBash)
+    await ctx.plugin(ToolBash, { dshHome: recordingDshHome })
     return { ctx, bash: ctx.bash as RecordingBashExecutor }
   }
 
-  it('describes the trusted session variables to the model', async () => {
+  it('describes the managed harness environment namespace to the model', async () => {
     const { ctx } = await setupRecording()
     const description = ctx.tools.get('bash')?.description ?? ''
-    expect(description).toContain('DSH_SESSION_ID')
-    expect(description).toContain('DSH_SESSION_JSONL')
+    expect(description).toContain('$DSH_*')
+    expect(description).not.toContain('DSH_SESSION_JSONL')
   })
 
   it('injects the session id and JSONL target path into a foreground request', async () => {
@@ -966,9 +969,11 @@ describe('the model-facing bash tool builds its request from named args only (no
       agent,
     })
 
-    expect(bash.requests[0]?.env).toEqual({
+    expect(bash.requests[0]?.dshEnv).toEqual({
+      DSH_HOME: recordingDshHome,
       DSH_SESSION_ID: 'request-fg',
       DSH_SESSION_JSONL: path,
+      DSH_SHELL: '1',
     })
   })
 
@@ -989,13 +994,16 @@ describe('the model-facing bash tool builds its request from named args only (no
       agent,
     })
 
-    expect(bash.requests[0]?.env).toEqual({
+    expect(bash.requests[0]?.env).toBeUndefined()
+    expect(bash.requests[0]?.dshEnv).toEqual({
+      DSH_HOME: recordingDshHome,
       DSH_SESSION_ID: 'request-bg',
       DSH_SESSION_JSONL: path,
+      DSH_SHELL: '1',
     })
   })
 
-  it('injects only the stable session id when no JSONL locator is available', async () => {
+  it('injects built-ins and the stable session id when no JSONL locator is available', async () => {
     const { ctx, bash } = await setupRecording()
     const agent = registerFakeAgent(ctx, 'request-id-only', () => undefined)
     const ambient = process.env.DSH_SESSION_ID
@@ -1007,7 +1015,11 @@ describe('the model-facing bash tool builds its request from named args only (no
       agent,
     })
 
-    expect(bash.requests[0]?.env).toEqual({ DSH_SESSION_ID: 'request-id-only' })
+    expect(bash.requests[0]?.dshEnv).toEqual({
+      DSH_HOME: recordingDshHome,
+      DSH_SESSION_ID: 'request-id-only',
+      DSH_SHELL: '1',
+    })
     expect(process.env.DSH_SESSION_ID).toBe(ambient)
   })
 
@@ -1025,17 +1037,21 @@ describe('the model-facing bash tool builds its request from named args only (no
       })
     }
 
-    expect(bash.requests.map(request => request.env)).toEqual([
+    expect(bash.requests.map(request => request.dshEnv)).toEqual([
       {
+        DSH_HOME: recordingDshHome,
         DSH_SESSION_ID: 'request-parent',
         DSH_SESSION_JSONL: ctx.sessionPersistence.locate(parent.session.header)?.path,
+        DSH_SHELL: '1',
       },
       {
+        DSH_HOME: recordingDshHome,
         DSH_SESSION_ID: 'request-child',
         DSH_SESSION_JSONL: ctx.sessionPersistence.locate(child.session.header)?.path,
+        DSH_SHELL: '1',
       },
     ])
-    expect(bash.requests[0]?.env?.DSH_SESSION_JSONL).not.toBe(bash.requests[1]?.env?.DSH_SESSION_JSONL)
+    expect(bash.requests[0]?.dshEnv?.DSH_SESSION_JSONL).not.toBe(bash.requests[1]?.dshEnv?.DSH_SESSION_JSONL)
   })
 
   it('does not forward env/stdin even when the model includes them as extra arguments', async () => {