Merge remote-tracking branch 'origin/master' into codex/session-scoped-sandbox-roots

# Conflicts:
#	examples/acp-agent/tests/acp.snapshot.ts
#	packages/examples/agent-spine-demo/package.json
#	pnpm-lock.yaml

packages/fs/README.md

@@ -8,7 +8,7 @@ The filesystem stack: a provider seam (text IO + atomic mutation with an optiona
 | `fs-local/` | Local-filesystem `FileSystem` implementation | (registers `ctx.fs`) |
 | `fs-sandbox/` | Sandbox-enforcing `FileSystem`: extends `fs-local` and fences write/edit by the per-call mode + workspace root policy (read-only denies, workspace-write contains to the session workspace + temp roots), reads pass through | (registers `ctx.fs`) |
 | `fs-policy/` | Policy gate plugin: observed-state + read-before-edit + version-guarded write/edit, via the `fs/*` event gate | (no service — `fs/*` listeners) |
-| `tool-fs/` | Model-facing `read`/`write`/`edit` tools AND the executor (reads via `ctx.fs`, owns read windowing, dispatches `fs/*`); resolves relative paths from the filesystem identity of the session cwd and advertises sandbox escalation fields when the mounted `ctx.fs` confines | (registers on `ctx.tools`) |
+| `tool-fs/` | Model-facing `read`/`write`/`edit` tools AND the executor (reads via `ctx.fs`, owns read windowing, dispatches `fs/*`); preserves filesystem semantics for session-cwd-relative paths and advertises sandbox escalation fields when the mounted `ctx.fs` confines | (registers on `ctx.tools`) |
 | `tool-fs-search/` | Model-facing `glob`/`grep` discovery tools when `rg` is available on the bash executor `PATH`, backed by fixed ripgrep commands through `ctx.bash`, NOT by `ctx.fs` provider methods | (registers on `ctx.tools`) |
 
 The interface lives at `fs/fs/`. A sandboxed, remote, or project-scoped filesystem backend can replace `fs-local` without touching the seam, the policy gate, or the model-facing tool schemas — `fs-sandbox` is the first such replacement (an in-process path fence over the shared sandbox mode; see [the cross-family fs sandbox Agent Note](../../.agents/notes/implemented/feature/2026-07-14-cross-family-fs-sandbox.md)). The policy (`fs-policy/`) is a plugin that participates only through the `fs/*` event gate, not a service the tool injects — so dropping it gracefully loses the policy and leaves the unconstrained bare provider rather than breaking the tool. A deployment that loads `tool-fs/` is expected to also load it. The mode fence and the read-before-edit gate are orthogonal and compose. Discovery (`tool-fs-search/`) deliberately does NOT extend the provider seam: search is a process-backed `rg` workflow on the bash executor, so filesystem backends stay free of a universal search contract; its tools register only when that executor can find `rg`, and its results are follow-up-readable when the bash workdir and the `read` root are the same workspace (the co-located deployment its README documents).

packages/fs/fs-local/package.json

@@ -11,11 +11,16 @@
       "types": "./lib/types/index.d.ts",
       "default": "./lib/index.js"
     },
+    "./invariant": {
+      "types": "./lib/types/invariant.d.ts",
+      "default": "./lib/invariant.js"
+    },
     "./src/*": "./src/*",
     "./package.json": "./package.json"
   },
   "files": [
     "lib/index.js",
+    "lib/invariant.js",
     "lib/types/**/*.d.ts",
     "lib/types/**/*.d.ts.map",
     "src"
@@ -23,6 +28,7 @@
   "license": "BSD-3-Clause",
   "peerDependencies": {
     "@deepseek-ai/dsh-fs": "^0.0.1",
+    "@deepseek-ai/dsh-invariants": "^0.0.1",
     "cordis": "^4.0.0-rc.7"
   },
   "dependencies": {
@@ -30,6 +36,7 @@
   },
   "devDependencies": {
     "@deepseek-ai/dsh-fs": "workspace:^",
+    "@deepseek-ai/dsh-invariants": "workspace:^",
     "@deepseek-ai/dsh-llm": "workspace:^",
     "cordis": "^4.0.0-rc.7"
   }

packages/fs/fs-local/src/invariant.ts

@@ -0,0 +1,30 @@
+/**
+ * Package-owned invariant companion for `@deepseek-ai/dsh-fs-local`.
+ * @module @deepseek-ai/dsh-fs-local/invariant
+ */
+
+/* jscpd:ignore-start */
+import type { Context } from 'cordis'
+import type { InvariantInstaller } from '@deepseek-ai/dsh-invariants'
+
+const PACKAGE_NAME = '@deepseek-ai/dsh-fs-local'
+
+/** Cordis companion plugin name. */
+export const name = 'fs-local-invariant'
+/** Service required before the companion can reserve package ownership. */
+export const inject = ['invariants']
+
+/**
+ * No runtime invariant: this package exposes no independent event sequence or mutable data relation
+ * beyond contracts enforced at its owning seam.
+ */
+const install: InvariantInstaller = () => {}
+
+/**
+ * Register this package's invariant companion.
+ * @param ctx - Cordis context carrying the invariant service.
+ * @returns the installed registration's disposer after setup succeeds.
+ */
+export const apply = (ctx: Context): Promise<() => void> =>
+  Promise.resolve(ctx.invariants.register(PACKAGE_NAME, install))
+/* jscpd:ignore-end */

packages/fs/fs-local/tsconfig.json

@@ -6,10 +6,23 @@
   },
   "include": ["src"],
   "references": [
-    { "path": "../../../vendor/cosmokit" },
-    { "path": "../../../vendor/cordis" },
-    { "path": "../../../vendor/schemastery" },
-    { "path": "../../llm/llm" },
-    { "path": "../fs" }
+    {
+      "path": "../../../vendor/cosmokit"
+    },
+    {
+      "path": "../../../vendor/cordis"
+    },
+    {
+      "path": "../../../vendor/schemastery"
+    },
+    {
+      "path": "../../llm/llm"
+    },
+    {
+      "path": "../fs"
+    },
+    {
+      "path": "../../support/invariants"
+    }
   ]
 }

packages/fs/fs-policy/package.json

@@ -11,11 +11,16 @@
       "types": "./lib/types/index.d.ts",
       "default": "./lib/index.js"
     },
+    "./invariant": {
+      "types": "./lib/types/invariant.d.ts",
+      "default": "./lib/invariant.js"
+    },
     "./src/*": "./src/*",
     "./package.json": "./package.json"
   },
   "files": [
     "lib/index.js",
+    "lib/invariant.js",
     "lib/types/**/*.d.ts",
     "lib/types/**/*.d.ts.map",
     "src"
@@ -23,10 +28,12 @@
   "license": "BSD-3-Clause",
   "peerDependencies": {
     "@deepseek-ai/dsh-fs": "^0.0.1",
+    "@deepseek-ai/dsh-invariants": "^0.0.1",
     "cordis": "^4.0.0-rc.7"
   },
   "devDependencies": {
     "@deepseek-ai/dsh-fs": "workspace:^",
+    "@deepseek-ai/dsh-invariants": "workspace:^",
     "@deepseek-ai/dsh-llm": "workspace:^",
     "cordis": "^4.0.0-rc.7"
   }

packages/fs/fs-policy/src/invariant.ts

@@ -0,0 +1,30 @@
+/**
+ * Package-owned invariant companion for `@deepseek-ai/dsh-fs-policy`.
+ * @module @deepseek-ai/dsh-fs-policy/invariant
+ */
+
+/* jscpd:ignore-start */
+import type { Context } from 'cordis'
+import type { InvariantInstaller } from '@deepseek-ai/dsh-invariants'
+
+const PACKAGE_NAME = '@deepseek-ai/dsh-fs-policy'
+
+/** Cordis companion plugin name. */
+export const name = 'fs-policy-invariant'
+/** Service required before the companion can reserve package ownership. */
+export const inject = ['invariants']
+
+/**
+ * No runtime invariant: this package exposes no independent event sequence or mutable data relation
+ * beyond contracts enforced at its owning seam.
+ */
+const install: InvariantInstaller = () => {}
+
+/**
+ * Register this package's invariant companion.
+ * @param ctx - Cordis context carrying the invariant service.
+ * @returns the installed registration's disposer after setup succeeds.
+ */
+export const apply = (ctx: Context): Promise<() => void> =>
+  Promise.resolve(ctx.invariants.register(PACKAGE_NAME, install))
+/* jscpd:ignore-end */

packages/fs/fs-policy/tsconfig.json

@@ -6,9 +6,20 @@
   },
   "include": ["src"],
   "references": [
-    { "path": "../../../vendor/cosmokit" },
-    { "path": "../../../vendor/cordis" },
-    { "path": "../../llm/llm" },
-    { "path": "../fs" }
+    {
+      "path": "../../../vendor/cosmokit"
+    },
+    {
+      "path": "../../../vendor/cordis"
+    },
+    {
+      "path": "../../llm/llm"
+    },
+    {
+      "path": "../fs"
+    },
+    {
+      "path": "../../support/invariants"
+    }
   ]
 }

packages/fs/fs-sandbox/package.json

@@ -11,11 +11,16 @@
       "types": "./lib/types/index.d.ts",
       "default": "./lib/index.js"
     },
+    "./invariant": {
+      "types": "./lib/types/invariant.d.ts",
+      "default": "./lib/invariant.js"
+    },
     "./src/*": "./src/*",
     "./package.json": "./package.json"
   },
   "files": [
     "lib/index.js",
+    "lib/invariant.js",
     "lib/types/**/*.d.ts",
     "lib/types/**/*.d.ts.map",
     "src"
@@ -24,6 +29,7 @@
   "peerDependencies": {
     "@deepseek-ai/dsh-fs": "^0.0.1",
     "@deepseek-ai/dsh-fs-local": "^0.0.1",
+    "@deepseek-ai/dsh-invariants": "^0.0.1",
     "@deepseek-ai/dsh-sandbox": "^0.0.1",
     "@deepseek-ai/dsh-sandbox-policy": "^0.0.1",
     "cordis": "^4.0.0-rc.7"
@@ -31,6 +37,7 @@
   "devDependencies": {
     "@deepseek-ai/dsh-fs": "workspace:^",
     "@deepseek-ai/dsh-fs-local": "workspace:^",
+    "@deepseek-ai/dsh-invariants": "workspace:^",
     "@deepseek-ai/dsh-sandbox": "workspace:^",
     "@deepseek-ai/dsh-sandbox-policy": "workspace:^",
     "cordis": "^4.0.0-rc.7"

packages/fs/fs-sandbox/src/invariant.ts

@@ -0,0 +1,27 @@
+/**
+ * Package-owned invariant companion for `@deepseek-ai/dsh-fs-sandbox`.
+ * @module @deepseek-ai/dsh-fs-sandbox/invariant
+ */
+
+/* jscpd:ignore-start */
+import type { Context } from 'cordis'
+import type { InvariantInstaller } from '@deepseek-ai/dsh-invariants'
+
+const PACKAGE_NAME = '@deepseek-ai/dsh-fs-sandbox'
+
+/** Cordis companion plugin name. */
+export const name = 'fs-sandbox-invariant'
+/** Services required before the companion can register. */
+export const inject = ['invariants']
+
+/** No runtime invariant: this stateless adapter delegates policy and filesystem relations to their owning seams. */
+const install: InvariantInstaller = () => {}
+
+/**
+ * Register this package's invariant companion.
+ * @param ctx - Cordis context carrying the invariant service.
+ * @returns the installed registration's disposer after setup succeeds.
+ */
+export const apply = (ctx: Context): Promise<() => void> =>
+  Promise.resolve(ctx.invariants.register(PACKAGE_NAME, install))
+/* jscpd:ignore-end */

packages/fs/fs-sandbox/tsconfig.json

@@ -25,6 +25,9 @@
     },
     {
       "path": "../../sandbox/sandbox-policy"
+    },
+    {
+      "path": "../../support/invariants"
     }
   ]
 }

packages/fs/fs/package.json

@@ -11,11 +11,16 @@
       "types": "./lib/types/index.d.ts",
       "default": "./lib/index.js"
     },
+    "./invariant": {
+      "types": "./lib/types/invariant.d.ts",
+      "default": "./lib/invariant.js"
+    },
     "./src/*": "./src/*",
     "./package.json": "./package.json"
   },
   "files": [
     "lib/index.js",
+    "lib/invariant.js",
     "lib/types/**/*.d.ts",
     "lib/types/**/*.d.ts.map",
     "src"
@@ -23,12 +28,14 @@
   "license": "BSD-3-Clause",
   "peerDependencies": {
     "@deepseek-ai/dsh-brand": "^0.0.1",
+    "@deepseek-ai/dsh-invariants": "^0.0.1",
     "@deepseek-ai/dsh-llm": "^0.0.1",
     "@deepseek-ai/dsh-sandbox": "^0.0.1",
     "cordis": "^4.0.0-rc.7"
   },
   "devDependencies": {
     "@deepseek-ai/dsh-brand": "workspace:^",
+    "@deepseek-ai/dsh-invariants": "workspace:^",
     "@deepseek-ai/dsh-llm": "workspace:^",
     "@deepseek-ai/dsh-sandbox": "workspace:^",
     "cordis": "^4.0.0-rc.7"

packages/fs/fs/src/invariant.ts

@@ -0,0 +1,39 @@
+/** Package-owned filesystem event-data invariants. @module @deepseek-ai/dsh-fs/invariant */
+
+import type { Context } from 'cordis'
+import type { InvariantInstaller } from '@deepseek-ai/dsh-invariants'
+import type { FsTarget, FsVersion } from './types.ts'
+
+const PACKAGE_NAME = '@deepseek-ai/dsh-fs'
+
+/** Cordis companion plugin name. */
+export const name = 'fs-invariant'
+/** Service required before the companion can reserve package ownership. */
+export const inject = ['invariants']
+
+/** Assert that an event carries a usable opaque target identity. */
+function validateTarget(target: FsTarget, fail: (message: string) => never): void {
+  if (target.targetKey.length === 0) fail('filesystem event targetKey must be non-empty')
+  if (target.displayPath.length === 0) fail('filesystem event displayPath must be non-empty')
+}
+
+/** Install checks over the filesystem decision and observation event stream. */
+const install: InvariantInstaller = (ctx, fail) => {
+  ctx.on('internal/dispatch', (_mode, eventName, args) => {
+    if (eventName !== 'fs/write-intent'
+      && eventName !== 'fs/edit-intent'
+      && eventName !== 'fs/observed') return
+    validateTarget(args[0] as FsTarget, fail)
+    if (eventName === 'fs/observed' && (args[1] as FsVersion).length === 0) {
+      fail('fs/observed version must be non-empty')
+    }
+  }, { global: true })
+}
+
+/**
+ * Register the filesystem invariant companion.
+ * @param ctx - Cordis context carrying the invariant service.
+ * @returns the installed registration's disposer after setup succeeds.
+ */
+export const apply = (ctx: Context): Promise<() => void> =>
+  Promise.resolve(ctx.invariants.register(PACKAGE_NAME, install))

packages/fs/fs/tests/invariant.spec.ts

@@ -0,0 +1,44 @@
+import { describe, expect, it } from 'vitest'
+import { Context } from 'cordis'
+import { FsTargetKey, FsVersion } from '@deepseek-ai/dsh-fs'
+import type { FsTarget } from '@deepseek-ai/dsh-fs'
+import * as FsInvariant from '@deepseek-ai/dsh-fs/invariant'
+import InvariantService from '@deepseek-ai/dsh-invariants'
+
+async function setup(): Promise<Context> {
+  const ctx = new Context()
+  await ctx.plugin(InvariantService)
+  await ctx.plugin(FsInvariant)
+  return ctx
+}
+
+const target = (key = 'file:1', displayPath = 'file.txt'): FsTarget => ({
+  targetKey: FsTargetKey(key),
+  displayPath,
+})
+
+describe('filesystem invariants', () => {
+  it('accepts decision and observation events with usable identities', async () => {
+    const ctx = await setup()
+    await expect(ctx.waterfall(
+      ctx as never, 'fs/write-intent', target(), undefined,
+      () => Promise.resolve(undefined),
+    )).resolves.toBeUndefined()
+    await expect(ctx.waterfall(
+      ctx as never, 'fs/edit-intent', target(), undefined,
+      () => Promise.resolve(undefined),
+    )).resolves.toBeUndefined()
+    expect(() => { ctx.emit('fs/observed', target(), FsVersion('v1'), undefined) }).not.toThrow()
+    expect(() => { ctx.emit('tools/change') }).not.toThrow()
+  })
+
+  it('rejects empty target and version identities', async () => {
+    const ctx = await setup()
+    expect(() => { ctx.emit('fs/observed', target(''), FsVersion('v1'), undefined) })
+      .toThrow(/targetKey must be non-empty/)
+    expect(() => { ctx.emit('fs/observed', target('file:1', ''), FsVersion('v1'), undefined) })
+      .toThrow(/displayPath must be non-empty/)
+    expect(() => { ctx.emit('fs/observed', target(), FsVersion(''), undefined) })
+      .toThrow(/version must be non-empty/)
+  })
+})

packages/fs/fs/tsconfig.json

@@ -6,10 +6,23 @@
   },
   "include": ["src"],
   "references": [
-    { "path": "../../../vendor/cosmokit" },
-    { "path": "../../../vendor/cordis" },
-    { "path": "../../util/brand" },
-    { "path": "../../llm/llm" },
-    { "path": "../../sandbox/sandbox" }
+    {
+      "path": "../../../vendor/cosmokit"
+    },
+    {
+      "path": "../../../vendor/cordis"
+    },
+    {
+      "path": "../../util/brand"
+    },
+    {
+      "path": "../../llm/llm"
+    },
+    {
+      "path": "../../support/invariants"
+    },
+    {
+      "path": "../../sandbox/sandbox"
+    }
   ]
 }

packages/fs/tool-fs-search/package.json

@@ -11,11 +11,16 @@
       "types": "./lib/types/index.d.ts",
       "default": "./lib/index.js"
     },
+    "./invariant": {
+      "types": "./lib/types/invariant.d.ts",
+      "default": "./lib/invariant.js"
+    },
     "./src/*": "./src/*",
     "./package.json": "./package.json"
   },
   "files": [
     "lib/index.js",
+    "lib/invariant.js",
     "lib/types/**/*.d.ts",
     "lib/types/**/*.d.ts.map",
     "src"
@@ -26,6 +31,7 @@
   },
   "peerDependencies": {
     "@deepseek-ai/dsh-bash": "^0.0.1",
+    "@deepseek-ai/dsh-invariants": "^0.0.1",
     "@deepseek-ai/dsh-llm": "^0.0.1",
     "@deepseek-ai/dsh-retention": "^0.0.1",
     "@deepseek-ai/dsh-session": "^0.0.1",
@@ -38,6 +44,7 @@
     "@deepseek-ai/dsh-agent": "workspace:^",
     "@deepseek-ai/dsh-bash": "workspace:^",
     "@deepseek-ai/dsh-bash-local": "workspace:^",
+    "@deepseek-ai/dsh-invariants": "workspace:^",
     "@deepseek-ai/dsh-llm": "workspace:^",
     "@deepseek-ai/dsh-retention": "workspace:^",
     "@deepseek-ai/dsh-session": "workspace:^",

packages/fs/tool-fs-search/src/invariant.ts

@@ -0,0 +1,30 @@
+/**
+ * Package-owned invariant companion for `@deepseek-ai/dsh-tool-fs-search`.
+ * @module @deepseek-ai/dsh-tool-fs-search/invariant
+ */
+
+/* jscpd:ignore-start */
+import type { Context } from 'cordis'
+import type { InvariantInstaller } from '@deepseek-ai/dsh-invariants'
+
+const PACKAGE_NAME = '@deepseek-ai/dsh-tool-fs-search'
+
+/** Cordis companion plugin name. */
+export const name = 'tool-fs-search-invariant'
+/** Service required before the companion can reserve package ownership. */
+export const inject = ['invariants']
+
+/**
+ * No runtime invariant: this model-facing adapter has no independent lifecycle stream; execution
+ * relations are owned by the capability seam it calls.
+ */
+const install: InvariantInstaller = () => {}
+
+/**
+ * Register this package's invariant companion.
+ * @param ctx - Cordis context carrying the invariant service.
+ * @returns the installed registration's disposer after setup succeeds.
+ */
+export const apply = (ctx: Context): Promise<() => void> =>
+  Promise.resolve(ctx.invariants.register(PACKAGE_NAME, install))
+/* jscpd:ignore-end */

packages/fs/tool-fs-search/tsconfig.json

@@ -6,15 +6,38 @@
   },
   "include": ["src"],
   "references": [
-    { "path": "../../../vendor/cosmokit" },
-    { "path": "../../../vendor/cordis" },
-    { "path": "../../../vendor/schemastery" },
-    { "path": "../../util/retention" },
-    { "path": "../../llm/llm" },
-    { "path": "../../core/session" },
-    { "path": "../../core/tools" },
-    { "path": "../../core/system-prompt" },
-    { "path": "../../bash/bash" },
-    { "path": "../../spill/spill" }
+    {
+      "path": "../../../vendor/cosmokit"
+    },
+    {
+      "path": "../../../vendor/cordis"
+    },
+    {
+      "path": "../../../vendor/schemastery"
+    },
+    {
+      "path": "../../util/retention"
+    },
+    {
+      "path": "../../llm/llm"
+    },
+    {
+      "path": "../../core/session"
+    },
+    {
+      "path": "../../core/tools"
+    },
+    {
+      "path": "../../core/system-prompt"
+    },
+    {
+      "path": "../../bash/bash"
+    },
+    {
+      "path": "../../spill/spill"
+    },
+    {
+      "path": "../../support/invariants"
+    }
   ]
 }

packages/fs/tool-fs/package.json

@@ -11,11 +11,16 @@
       "types": "./lib/types/index.d.ts",
       "default": "./lib/index.js"
     },
+    "./invariant": {
+      "types": "./lib/types/invariant.d.ts",
+      "default": "./lib/invariant.js"
+    },
     "./src/*": "./src/*",
     "./package.json": "./package.json"
   },
   "files": [
     "lib/index.js",
+    "lib/invariant.js",
     "lib/types/**/*.d.ts",
     "lib/types/**/*.d.ts.map",
     "src"
@@ -27,6 +32,7 @@
   },
   "peerDependencies": {
     "@deepseek-ai/dsh-fs": "^0.0.1",
+    "@deepseek-ai/dsh-invariants": "^0.0.1",
     "@deepseek-ai/dsh-llm": "^0.0.1",
     "@deepseek-ai/dsh-sandbox": "^0.0.1",
     "@deepseek-ai/dsh-sandbox-policy": "^0.0.1",
@@ -40,9 +46,10 @@
     "@deepseek-ai/dsh-agent": "workspace:^",
     "@deepseek-ai/dsh-agent-loop": "workspace:^",
     "@deepseek-ai/dsh-agent-loop-testkit": "workspace:^",
-    "@deepseek-ai/dsh-fs-policy": "workspace:^",
     "@deepseek-ai/dsh-fs": "workspace:^",
     "@deepseek-ai/dsh-fs-local": "workspace:^",
+    "@deepseek-ai/dsh-fs-policy": "workspace:^",
+    "@deepseek-ai/dsh-invariants": "workspace:^",
     "@deepseek-ai/dsh-llm": "workspace:^",
     "@deepseek-ai/dsh-llm-deepseek": "workspace:^",
     "@deepseek-ai/dsh-sandbox": "workspace:^",

packages/fs/tool-fs/src/invariant.ts

@@ -0,0 +1,30 @@
+/**
+ * Package-owned invariant companion for `@deepseek-ai/dsh-tool-fs`.
+ * @module @deepseek-ai/dsh-tool-fs/invariant
+ */
+
+/* jscpd:ignore-start */
+import type { Context } from 'cordis'
+import type { InvariantInstaller } from '@deepseek-ai/dsh-invariants'
+
+const PACKAGE_NAME = '@deepseek-ai/dsh-tool-fs'
+
+/** Cordis companion plugin name. */
+export const name = 'tool-fs-invariant'
+/** Service required before the companion can reserve package ownership. */
+export const inject = ['invariants']
+
+/**
+ * No runtime invariant: this model-facing adapter has no independent lifecycle stream; execution
+ * relations are owned by the capability seam it calls.
+ */
+const install: InvariantInstaller = () => {}
+
+/**
+ * Register this package's invariant companion.
+ * @param ctx - Cordis context carrying the invariant service.
+ * @returns the installed registration's disposer after setup succeeds.
+ */
+export const apply = (ctx: Context): Promise<() => void> =>
+  Promise.resolve(ctx.invariants.register(PACKAGE_NAME, install))
+/* jscpd:ignore-end */

packages/fs/tool-fs/src/session-cwd.ts

@@ -11,6 +11,8 @@
 import type { ToolExecution } from '@deepseek-ai/dsh-tools'
 import { canonicalPath } from '@deepseek-ai/dsh-sandbox'
 
+const PARENT_PATH_SEGMENT = /(?:^|[\\/])\.\.(?:[\\/]|$)/
+
 /**
  * The session workspace cwd for this call, or `undefined` when none applies.
  * @param exec - the tool-execution context; only its optional `agent` is read.
@@ -18,7 +20,8 @@ import { canonicalPath } from '@deepseek-ai/dsh-sandbox'
  */
 export function sessionCwd(exec: ToolExecution): string | undefined {
   const cwd = exec.agent?.session.header.cwd
-  return cwd === undefined ? undefined : canonicalPath(cwd)
+  if (cwd === undefined || !PARENT_PATH_SEGMENT.test(cwd)) return cwd
+  return canonicalPath(cwd)
 }
 
 /**

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

@@ -5,6 +5,8 @@
 
 import { describe, expect, it, vi } from 'vitest'
 import { Context } from 'cordis'
+import { realpathSync } from 'node:fs'
+import { sep } from 'node:path'
 import { CallId } from '@deepseek-ai/dsh-llm'
 import SystemPrompt, { renderPrompt } from '@deepseek-ai/dsh-system-prompt'
 import ToolRegistry from '@deepseek-ai/dsh-tools'
@@ -24,6 +26,7 @@ import * as ToolFs from '@deepseek-ai/dsh-tool-fs'
 import { STREAM_MIN_SIZE } from '../src/read.ts'
 import { formatReadOutput } from '../src/read-render.ts'
 import type { FileReadOutcome } from '../src/read-render.ts'
+import { sessionCwd } from '../src/session-cwd.ts'
 import ApprovalService from '@deepseek-ai/dsh-user-approval'
 import type { SandboxExecutionPolicy, SandboxMode } from '@deepseek-ai/dsh-sandbox'
 import SandboxPolicyService from '@deepseek-ai/dsh-sandbox-policy'
@@ -105,6 +108,20 @@ function text(result: { content: { type: string; text?: string }[] }): string {
   return result.content.filter(b => b.type === 'text').map(b => b.text).join('')
 }
 
+describe('session cwd resolution', () => {
+  const execution = (cwd?: string) => cwd === undefined
+    ? {}
+    : { agent: { session: { header: { cwd } } } }
+
+  it('retains ordinary spelling but resolves parent segments before lexical use', () => {
+    const cwd = process.cwd()
+    const throughParent = `${cwd}${sep}..`
+    expect(sessionCwd(execution() as never)).toBeUndefined()
+    expect(sessionCwd(execution(cwd) as never)).toBe(cwd)
+    expect(sessionCwd(execution(throughParent) as never)).toBe(realpathSync.native(throughParent))
+  })
+})
+
 describe('registration', () => {
   it('registers read, write, and edit', async () => {
     const { ctx } = await setup()

packages/fs/tool-fs/tsconfig.json

@@ -6,16 +6,41 @@
   },
   "include": ["src"],
   "references": [
-    { "path": "../../../vendor/cosmokit" },
-    { "path": "../../../vendor/cordis" },
-    { "path": "../../../vendor/schemastery" },
-    { "path": "../../llm/llm" },
-    { "path": "../../core/tools" },
-    { "path": "../../core/system-prompt" },
-    { "path": "../fs" },
-    { "path": "../fs-policy" },
-    { "path": "../../sandbox/sandbox" },
-    { "path": "../../sandbox/sandbox-policy" },
-    { "path": "../../ui/user-approval" }
+    {
+      "path": "../../../vendor/cosmokit"
+    },
+    {
+      "path": "../../../vendor/cordis"
+    },
+    {
+      "path": "../../../vendor/schemastery"
+    },
+    {
+      "path": "../../llm/llm"
+    },
+    {
+      "path": "../../core/tools"
+    },
+    {
+      "path": "../../core/system-prompt"
+    },
+    {
+      "path": "../fs"
+    },
+    {
+      "path": "../fs-policy"
+    },
+    {
+      "path": "../../support/invariants"
+    },
+    {
+      "path": "../../sandbox/sandbox"
+    },
+    {
+      "path": "../../sandbox/sandbox-policy"
+    },
+    {
+      "path": "../../ui/user-approval"
+    }
   ]
 }