feat: scope a session from a declaration the agent cannot widen

The facet root was the session's working directory and nothing else, so the
only way to scope a conversation to a module was to make the module a
workspace — and the only way to reach anything outside it was `extraRoots`,
which is a fact about the deployment rather than about one conversation.

Scope now has two layers, and the split is the point. The **user layer** is
`config.scopes[sessionId]` — a `focus` and a list of `extras`, written only
from the browser context panel through the settings service, which is what
`settings.mutate` requiring a volatile path buys us. The **agent layer** is in
memory: a narrowing `focus` and its grants. Both can only ever reduce what the
user layer allows, so an agent that goes wrong cannot widen its own scope.

`facet action=focus` is therefore the one scope change the agent may make
unasked, bounded by the scope already in force and decided on canonical targets.
`reset` clears the agent's side only, landing on the user's declaration rather
than on the session directory — landing on the directory would have made
`reset` a widening. `extraRoots` demotes to an optional deployment-wide seed.

The binding now names the context panel as the way to widen, because it is: in
a deployment with no approval channel, `facet action=add` cannot be granted at
all.

index.js

@@ -33,20 +33,25 @@ export const name = 'dsh-facet'
 /**
  * Every configuration field this plugin exposes.
  *
- * `mode` and `extraRoots` are marked `volatile()`, and that marker is doing two
- * jobs rather than one. It is what puts them on the settings page at all — the
- * framework's form projection keeps only fields under a volatile ancestor, and
- * drops an entry with no such field from `settings.describe` entirely, so
- * without it this row has no card. It is also what makes an edit *live*: a
- * volatile field is handed to {@link apply} as a reference rather than a value,
- * and the framework commits an edit into that reference without re-applying the
- * plugin.
+ * `mode`, `extraRoots` and `scopes` are marked `volatile()`, and that marker is
+ * doing two jobs rather than one. It is what puts them on the settings page at
+ * all — the framework's form projection keeps only fields under a volatile
+ * ancestor, and drops an entry with no such field from `settings.describe`
+ * entirely, so without it this row has no card. It is also what makes an edit
+ * *live*: a volatile field is handed to {@link apply} as a reference rather than
+ * a value, and the framework commits an edit into that reference without
+ * re-applying the plugin.
  *
- * The second job is why every reader of these two fields goes through
+ * The second job is why every reader of these fields goes through
  * `configValue()` in `./lib/policy.js` and reads at the point of use. A plugin
  * that takes the reference for a string gets a settings card that appears to
  * work and changes nothing.
  *
+ * `scopes` is volatile for a third reason: it is the only field the browser
+ * context panel writes, and `settings.mutate` refuses a path that is not under a
+ * volatile node. That is the whole mechanism by which the panel — and not the
+ * agent — decides what one conversation may see.
+ *
  * `sectionOrder` and `contextOrder` are deliberately NOT volatile. They place
  * the rule and the binding among the other prompt sections, which is settled
  * once at load; making them volatile would put two knobs nobody should touch on
@@ -61,12 +66,46 @@ export const Config = Schema.object({
   mode: Schema.union(['ask', 'deny', 'off']).default('ask').volatile(),
 
   /**
-   * Paths always in scope, for code a module legitimately depends on — shared
-   * types, a common test harness. Relative paths resolve against each session's
-   * own directory, so the same list is meaningful in every workspace.
+   * A deployment-wide seed of paths always in scope, for code a module
+   * legitimately depends on — shared types, a common test harness.
+   *
+   * Deliberately only a seed. Before per-session scope existed this was the only
+   * way to widen anything, which meant "this one conversation needs the entity
+   * folder" had to be written as a fact about every conversation in every
+   * workspace. Per-session scope belongs in {@link Config.scopes}; this is for
+   * the paths a deployment genuinely always wants, and it is empty by default.
+   *
+   * Relative paths resolve against each session's own directory, so the same
+   * list is meaningful in every workspace.
    */
   extraRoots: Schema.array(String).default([]).volatile(),
 
+  /**
+   * Per-session scope — the user's declaration for one conversation, keyed by
+   * session id.
+   *
+   * Written only by the browser context panel, through the settings service, and
+   * never by the agent: this plugin exposes no write path to it, and a facet
+   * session carries no settings tool. `focus` narrows the session to a folder;
+   * `extras` are paths the conversation may read outside it. Both are relative
+   * to the session's own directory unless absolute, so a declaration keeps its
+   * meaning wherever the workspace lives.
+   *
+   * Entries outlive their sessions, which is deliberate — reopening a chat
+   * should give back the scope it had — and costs a little growth in the
+   * profile patch that the panel can tidy.
+   */
+  scopes: Schema.dict(
+    Schema.object({
+      /** The session's facet root, relative to the session directory or absolute. Empty means the session directory itself. */
+      focus: Schema.string(),
+      /** Paths this session may also read, outside the root. */
+      extras: Schema.array(String).default([]),
+    }),
+  )
+    .default({})
+    .volatile(),
+
   /** Placement of the invariant rule in the system prompt. */
   sectionOrder: Schema.number().default(100),
 

lib/guard.js

@@ -246,13 +246,18 @@ function requestedPaths(args) {
 }
 
 /**
- * The `facet` tool: read the scope, or ask to widen it.
+ * The `facet` tool: read the scope, narrow it, or ask to widen it.
  *
  * `add` does not enforce anything itself — the pre-execute listener has already
  * put the question to the user, and the body only runs if they said yes. That
  * split is deliberate: the approval is a property of the *call*, so it holds
  * even if this tool is later replaced or dispatched from `run_code`.
  *
+ * `focus` is the one action this tool performs without asking, and it is the
+ * only one that can only ever *reduce* the scope. That asymmetry is the whole
+ * design: an agent may decide a conversation is about one folder, and may not
+ * decide it is about more.
+ *
  * @param {import('@deepseek-ai/cordis').Context} ctx - the guard's context.
  * @param {object} policy - the `facetPolicy` service.
  */
@@ -260,21 +265,23 @@ function facetTool(ctx, policy) {
   return defineTool({
     name: FACET_TOOL,
     description:
-      'Read this session\u2019s facet scope, or ask the user to grant an extra path. A facet is the folder the ' +
-      'conversation was started in; the session is scoped to it. Use `status` to see the current scope. Use `add` ' +
-      'only when you actually need a file outside the facet — it asks the user for permission, and the grant lasts ' +
-      'for the rest of the conversation. Never call `add` for a path you merely expect to need.',
+      'Read this session\u2019s facet scope, narrow it to one folder, or ask the user for an extra path. A facet is ' +
+      'the folder the conversation is scoped to; `status` reports it. Use `focus` when the work has settled on one ' +
+      'folder inside the facet — narrowing is always allowed and takes effect at once. Use `add` only when you ' +
+      'actually need a file outside the facet: it asks the user for permission, and the grant lasts for the rest of ' +
+      'the conversation. Never call `add` for a path you merely expect to need. Where the deployment has no approval ' +
+      'channel, `add` cannot be granted at all and the user widens the scope from the facet panel in their browser.',
     parameters: {
       action: {
         type: 'string',
         required: true,
-        description: 'One of: status, add, remove, reset.',
+        description: 'One of: status, focus, add, remove, reset.',
       },
       paths: {
         type: 'array',
         items: { type: 'string' },
         description:
-          'Paths to grant, relative to the session directory or absolute. Required for add and remove; ignored otherwise.',
+          'Paths, relative to the session directory or absolute. Required for add and remove; for focus, exactly one folder inside the current facet.',
       },
     },
     output: {
@@ -307,13 +314,16 @@ function facetTool(ctx, policy) {
       const problem =
         (action === 'add' || action === 'remove') && requested.length === 0
           ? `facet: action "${action}" needs \`paths\``
-          : !['status', 'add', 'remove', 'reset'].includes(action)
-            ? `facet: unknown action "${action}"; expected status, add, remove or reset`
+          : action === 'focus' && requested.length !== 1
+            ? 'facet: action "focus" needs exactly one folder'
+            : !['status', 'focus', 'add', 'remove', 'reset'].includes(action)
+              ? `facet: unknown action "${action}"; expected status, focus, add, remove or reset`
               : undefined
       if (problem !== undefined) throw new Error(problem)
 
       const before = policy.grantsFor(sessionId)
-      if (action === 'add') policy.grant(sessionId, requested, cwd)
+      if (action === 'focus') policy.narrowTo(sessionId, await narrowing(ctx, policy, exec, requested[0]))
+      else if (action === 'add') policy.grant(sessionId, requested, cwd)
       else if (action === 'remove') policy.revoke(sessionId, requested, cwd)
       else if (action === 'reset') policy.reset(sessionId)
 
@@ -340,6 +350,48 @@ function facetTool(ctx, policy) {
   })
 }
 
+/**
+ * Resolve one `focus` request to the canonical root it asks for.
+ *
+ * Refuses anything the scope already in force does not contain, because that
+ * would be a widening by another name — and widening is the user's decision, not
+ * the agent's. The containment test is the filesystem provider's, on canonical
+ * targets, for the same reason the guard uses it: a symlink inside the facet
+ * that points outside it must not become a way through.
+ *
+ * The canonical key is what gets recorded, so a later `scopeFor` compares like
+ * with like. Where the user declared a root through a symlink, the two spellings
+ * may not share a prefix; the narrowing is then dropped rather than trusted,
+ * which loses the narrowing and never the boundary.
+ *
+ * @param {import('@deepseek-ai/cordis').Context} ctx - the guard's context, holding `fs`.
+ * @param {object} policy - the `facetPolicy` service.
+ * @param {import('@deepseek-ai/dsh-tools').ToolExecution} exec - the running call.
+ * @param {string} raw - the folder the model named.
+ * @returns {Promise<string>} the absolute root to narrow to.
+ */
+async function narrowing(ctx, policy, exec, raw) {
+  const scope = policy.scopeFor(exec.agent)
+  if (scope === undefined) throw new Error('facet: this session has no working directory, so there is nothing to narrow')
+
+  let target
+  let boundary
+  try {
+    target = await ctx.fs.resolve(raw, { cwd: scope.cwd, signal: exec.signal })
+    boundary = await ctx.fs.resolve(scope.root, { cwd: scope.cwd, signal: exec.signal })
+  } catch {
+    throw new Error(`facet: cannot resolve "${raw}", so the facet cannot be narrowed to it`)
+  }
+
+  if (target.targetKey !== boundary.targetKey && !ctx.fs.contains(boundary, target)) {
+    throw new Error(
+      `facet: "${raw}" is outside the current facet (${scope.root}). Narrowing cannot leave the scope already in force; ` +
+        'ask the user to widen it from the facet panel if the work really has moved.',
+    )
+  }
+  return target.targetKey
+}
+
 /** Model-facing text for one `facet` result. Pure. */
 function renderFacet(value) {
   const lines = [

lib/policy.js

@@ -16,7 +16,7 @@
  * exists to prevent.
  */
 
-import { isAbsolute, resolve } from 'node:path'
+import { isAbsolute, resolve, sep } from 'node:path'
 
 /**
  * The symbol cosmokit uses to mark a volatile config reference.
@@ -63,18 +63,78 @@ export function configValue(value) {
  * `config` is the *resolved* composition config, so its volatile fields are
  * references rather than values; every read below goes through
  * {@link configValue} and happens per use. Holding the config and reading it lazily
- * is what makes the settings card honest: `mode` and `extraRoots` are edited live
- * in the Web UI, and a policy that snapshotted them here would keep answering
- * with the values it was loaded with.
+ * is what makes the settings card honest: `mode`, `extraRoots` and `scopes` are
+ * edited live in the Web UI, and a policy that snapshotted them here would keep
+ * answering with the values it was loaded with.
+ *
+ * ## Two layers of scope, and only one of them the agent can move
+ *
+ * The session's scope is declared in two places on purpose, because the two
+ * audiences have opposite authority:
+ *
+ *   * the **user layer** is `config.scopes[sessionId]` — a `focus` and a list of
+ *     `extras`, written only from the browser context panel through the settings
+ *     service. The agent has no write path to it: nothing in this plugin exposes
+ *     one, and a facet session carries no settings tool.
+ *   * the **agent layer** is in memory — a narrowing `focus` override and the
+ *     grants it asked for. Both can only ever *reduce* what the user layer
+ *     allows, so an agent that goes wrong cannot widen its own scope.
+ *
+ * The effective root is the agent's narrowing while it still sits inside the
+ * user's root, and the user's root otherwise. That ordering matters when the
+ * user narrows after the agent has: the stale agent focus is dropped rather than
+ * honoured, because honouring it would put the session outside the scope the
+ * user had just declared.
  *
  * @param {object} config
  * @param {'ask'|'deny'|'off'} config.mode - how an out-of-scope call is handled.
- * @param {readonly string[]} [config.extraRoots] - standing grants, resolved against each session's cwd.
+ * @param {readonly string[]} [config.extraRoots] - a deployment-wide seed of standing grants.
+ * @param {Record<string, {focus?: string, extras?: readonly string[]}>} [config.scopes] - per-session scope, keyed by session id.
  * @returns {object} the `facetPolicy` service implementation.
  */
 export function createFacetPolicy(config) {
   /** @type {Map<string, string[]>} session id → granted paths, in the order granted. */
   const grants = new Map()
+  /** @type {Map<string, string>} session id → the agent's narrowing focus, absolute. */
+  const narrowed = new Map()
+
+  /**
+   * What the user declared for one session, read fresh.
+   *
+   * @param {string|undefined} sessionId - the session to read.
+   * @returns {{focus?: string, extras?: readonly string[]}|undefined} the declaration.
+   */
+  function declaredScope(sessionId) {
+    if (sessionId === undefined) return undefined
+    const all = configValue(config.scopes)
+    if (all === null || typeof all !== 'object') return undefined
+    const entry = all[sessionId]
+    return entry !== null && typeof entry === 'object' ? entry : undefined
+  }
+
+  /**
+   * The root in force for one session.
+   *
+   * The user's `focus` is resolved against the session directory, not against
+   * the process, so a relative declaration keeps its meaning if the workspace
+   * moves. The agent's narrowing is applied only while it is still inside that
+   * root; a plain prefix test is enough here because the guard's own containment
+   * check, which resolves symlinks, is what authorises a narrowing in the first
+   * place — this one only has to notice a root that has since moved out from
+   * under it.
+   *
+   * @param {string|undefined} sessionId - the session.
+   * @param {string} sessionCwd - its resolved working directory.
+   * @returns {string} the absolute facet root.
+   */
+  function rootFor(sessionId, sessionCwd) {
+    const declared = declaredScope(sessionId)?.focus
+    const base = typeof declared === 'string' && declared.trim() !== '' ? resolve(sessionCwd, declared) : sessionCwd
+    const agentFocus = sessionId === undefined ? undefined : narrowed.get(sessionId)
+    if (agentFocus === undefined) return base
+    if (agentFocus === base || agentFocus.startsWith(base.endsWith(sep) ? base : `${base}${sep}`)) return agentFocus
+    return base
+  }
 
   /**
    * The deployment's standing grants, read fresh on every call.
@@ -97,31 +157,77 @@ export function createFacetPolicy(config) {
    * something arbitrary: `undefined` here means the guard has no opinion, which
    * is the only safe reading of "we do not know where this agent is".
    *
+   * `cwd` stays the session directory even when the root is narrower, because
+   * it is what relative paths — a grant, a `focus`, an `extraRoots` entry —
+   * resolve against. A declaration written relative to the session keeps the
+   * same meaning whatever the session is focused on.
+   *
    * @param {{session?: {header?: {cwd?: unknown}, id?: unknown}}|undefined} agent - the calling agent.
    * @returns {FacetScope|undefined} the scope.
    */
   function scopeFor(agent) {
     const cwd = agent?.session?.header?.cwd
     if (typeof cwd !== 'string' || cwd.trim() === '') return undefined
-    const root = resolve(cwd)
-    return { cwd: root, root, extras: extrasFor(agent, root) }
+    const sessionCwd = resolve(cwd)
+    const sessionId = idOf(agent)
+    return {
+      cwd: sessionCwd,
+      root: rootFor(sessionId, sessionCwd),
+      extras: extrasFor(agent, sessionCwd),
+    }
   }
 
   /**
-   * Every path in scope beyond the root: standing grants first, then this
-   * session's, deduplicated so the prompt does not repeat itself.
+   * Every path in scope beyond the root: the deployment seed, then what the user
+   * declared for this session, then what the agent was granted — deduplicated so
+   * the prompt does not repeat itself.
+   *
+   * All three are kept rather than layered, because they answer different
+   * questions. The seed is "this deployment always needs it", the declaration is
+   * "this conversation needs it", and a grant is "the user allowed this call".
+   * Removing one from the list when a narrower one exists would mean a user
+   * editing their panel could silently drop a path the deployment depends on.
    *
    * @param {{session?: {id?: unknown}}|undefined} agent - the calling agent.
    * @param {string} cwd - the resolved session directory.
    * @returns {string[]} absolute paths.
    */
   function extrasFor(agent, cwd) {
-    const sessionId = typeof agent?.session?.id === 'string' ? agent.session.id : undefined
+    const sessionId = idOf(agent)
     const own = sessionId === undefined ? [] : grants.get(sessionId) ?? []
-    const all = [...standingRoots(), ...own].map((path) => (isAbsolute(path) ? resolve(path) : resolve(cwd, path)))
+    const declared = declaredScope(sessionId)?.extras
+    const listed = Array.isArray(declared) ? declared.filter(isPath) : []
+    const all = [...standingRoots(), ...listed, ...own].map((path) =>
+      isAbsolute(path) ? resolve(path) : resolve(cwd, path),
+    )
     return [...new Set(all)]
   }
 
+  /**
+   * Narrow one session's facet to a path the caller has already authorised.
+   *
+   * The containment check is the caller's, and deliberately so: only the guard
+   * holds `ctx.fs`, and deciding containment on canonical targets is the whole
+   * reason a symlink inside the facet does not open it. This records the answer;
+   * {@link rootFor} re-checks that the user has not since narrowed past it.
+   *
+   * @param {string} sessionId - the session being narrowed.
+   * @param {string} absolute - the absolute root to narrow to.
+   * @returns {string} the recorded focus.
+   */
+  function narrowTo(sessionId, absolute) {
+    narrowed.set(sessionId, absolute)
+    return absolute
+  }
+
+  /**
+   * @param {string} sessionId - the session to read.
+   * @returns {string|undefined} the agent's narrowing for it, if any.
+   */
+  function narrowFor(sessionId) {
+    return narrowed.get(sessionId)
+  }
+
   /**
    * @param {string} sessionId - the session being widened.
    * @param {readonly string[]} paths - raw paths, resolved against `cwd`.
@@ -154,11 +260,19 @@ export function createFacetPolicy(config) {
   }
 
   /**
+   * Clear one session's agent-side scope: its grants and any narrowing it asked
+   * for.
+   *
+   * Deliberately not a widening. The user's declaration is not touched, so this
+   * returns the session to what the user set up in the panel — which may be
+   * narrower than where the agent had got to, and can never be wider.
+   *
    * @param {string} sessionId - the session to clear.
    * @returns {string[]} always empty.
    */
   function reset(sessionId) {
     grants.delete(sessionId)
+    narrowed.delete(sessionId)
     return []
   }
 
@@ -173,6 +287,7 @@ export function createFacetPolicy(config) {
   /** Drop a finished session's grants. Called on `session/disposed`. */
   function forget(sessionId) {
     grants.delete(sessionId)
+    narrowed.delete(sessionId)
   }
 
   return {
@@ -183,11 +298,16 @@ export function createFacetPolicy(config) {
     /** Prompt placements, carried here so the preset row needs no configuration of its own. */
     sectionOrder: configValue(config.sectionOrder) ?? 100,
     contextOrder: configValue(config.contextOrder) ?? 105,
-    /** The standing grants. A getter for the same reason as {@link mode}. */
+    /** The deployment-wide seed of standing grants. A getter for the same reason as {@link mode}. */
     get standing() {
       return standingRoots()
     },
+    /** What the user declared for one session: their `focus` and `extras`. */
+    declaredFor: declaredScope,
     scopeFor,
+    rootFor,
+    narrowTo,
+    narrowFor,
     grant,
     revoke,
     reset,
@@ -204,3 +324,13 @@ export function createFacetPolicy(config) {
 function isPath(value) {
   return typeof value === 'string' && value.trim() !== ''
 }
+
+/**
+ * The session id of a calling agent, when it has one.
+ *
+ * @param {{session?: {id?: unknown}}|undefined} agent - the calling agent.
+ * @returns {string|undefined} the id.
+ */
+function idOf(agent) {
+  return typeof agent?.session?.id === 'string' ? agent.session.id : undefined
+}

lib/scope.js

@@ -195,12 +195,12 @@ export function facetContextText(input) {
   // the reason this guard writes never reaches it: `serviceAsk` replaces a
   // rejected ask with `the user rejected tool "…"`. So the binding is the one
   // channel that can say what is true, and it names the mechanism that still
-  // works — `extraRoots` is configuration applied by the profile, not a grant
-  // asked for per conversation.
+  // works: the facet's context panel, which the user owns and the agent has no
+  // write path to.
   const reach = !canAsk
-    ? 'refused — approval prompts are off in this session, so `facet action=add` cannot be approved either; only the user can widen this, by adding the path to `extraRoots`'
+    ? 'refused — this session has no approval channel, so `facet action=add` cannot be granted; ask the user to widen the facet from its context panel'
     : mode === 'deny'
-      ? 'refused — `facet action=add` asks the user to grant a path, and is the only way to widen the scope'
+      ? 'refused — ask the user to widen the facet from its context panel, or with `facet action=add` where that can be granted'
       : 'put to the user as a question — say in one line what you need and why, then record it with `facet action=add` so the rest of the session does not have to ask again'
 
   // The root is stated absolutely even though it is the session's own directory

test/client.test.js

@@ -160,14 +160,22 @@ test('nothing is registered while the Host does not serve the namespace', async
   assert.equal(seen.entry, undefined, 'but no card is registered for a namespace nobody serves')
 })
 
-test('the card stages exactly the fields the host marks volatile', async () => {
+test('the card stages exactly the deployment fields the host marks volatile', async () => {
   const { module: mod, staged } = await loadClient()
   drive(mod)
 
-  const declared = Object.entries(Config.dict)
+  const volatileFields = Object.entries(Config.dict)
     .filter(([, schema]) => schema.meta.volatile === true)
     .map(([key]) => key)
 
+  // `scopes` is volatile too, but it is not a deployment field and must not be a
+  // control on the card: it is per-session state, written by the context panel
+  // and keyed by session id. Staging it here would render a dictionary blob a
+  // user could not sensibly edit, and would put the panel's store on the one
+  // surface that edits the deployment.
+  assert.ok(volatileFields.includes('scopes'), 'scopes must be volatile or the panel cannot write it')
+  const declared = volatileFields.filter((key) => key !== 'scopes')
+
   // A field served but never staged is invisible in the UI; a field staged but
   // never served makes `whileServed` withhold the whole card.
   assert.deepEqual(

test/guard.test.js

@@ -107,6 +107,7 @@ before(async () => {
   root = await realpath(await mkdtemp(join(tmpdir(), 'dsh-facet-')))
   facet = join(root, 'src', 'controllers', 'room')
   await mkdir(facet, { recursive: true })
+  await mkdir(join(facet, 'inner'), { recursive: true })
   await mkdir(join(root, 'src', 'controllers', 'other'), { recursive: true })
   await mkdir(join(root, 'src', 'shared'), { recursive: true })
   await writeFile(join(facet, 'index.ts'), 'export {}\n')
@@ -293,9 +294,10 @@ test('the binding refuses honestly when the session has no approval channel', ()
   const { captured } = harness({ mode: 'ask', approval: 'never' })
   const text = captured.context.text({ agent: agent() })
 
-  assert.match(text, /approval prompts are off in this session/)
-  assert.match(text, /cannot be approved either/)
-  assert.match(text, /`extraRoots`/)
+  assert.match(text, /no approval channel/)
+  assert.match(text, /cannot be granted/)
+  // It names the mechanism that still works, which is the panel the user owns.
+  assert.match(text, /context panel/)
 
   // The promise `ask` makes cannot be kept here, so it must not be made.
   assert.doesNotMatch(text, /put to the user as a question/)
@@ -308,14 +310,14 @@ test('an approval channel keeps the promise, and a missing service counts as non
   // No approval service at all: the tool pipeline denies an ask it cannot route,
   // so the binding must not offer one.
   const without = harness({ mode: 'ask' })
-  assert.match(without.captured.context.text({ agent: agent() }), /approval prompts are off in this session/)
+  assert.match(without.captured.context.text({ agent: agent() }), /no approval channel/)
 })
 
 test('deny mode still names the way that works when there is no channel', () => {
   const { captured } = harness({ mode: 'deny', approval: 'never' })
   const text = captured.context.text({ agent: agent() })
   assert.match(text, /refused/)
-  assert.match(text, /`extraRoots`/)
+  assert.match(text, /context panel/)
 })
 
 test('the facet tool reports the scope', async () => {
@@ -347,6 +349,60 @@ test('the facet tool grants, narrows and clears', async () => {
   assert.deepEqual(policy.grantsFor('session-1'), [])
 })
 
+test('the facet tool narrows inside the facet and refuses a folder outside it', async () => {
+  const { captured, policy } = harness()
+  const exec = { agent: agent() }
+
+  // Narrowing is the one scope change the agent may make unasked: it can only
+  // ever reduce what is visible, so there is nothing for a user to approve.
+  const narrowed = await captured.tool.execute({ action: 'focus', paths: ['inner'] }, exec)
+  assert.equal(narrowed.root, join(facet, 'inner'))
+  assert.equal(narrowed.facet, join(facet, 'inner'))
+  assert.equal(policy.scopeFor(agent()).root, join(facet, 'inner'))
+
+  // A folder outside the scope already in force is a widening by another name,
+  // and widening is the user's decision, taken in their panel.
+  await assert.rejects(
+    () => captured.tool.execute({ action: 'focus', paths: ['../../shared'] }, exec),
+    /outside the current facet/,
+  )
+  await assert.rejects(
+    () => captured.tool.execute({ action: 'focus', paths: ['../other'] }, exec),
+    /outside the current facet/,
+  )
+  // A refused narrowing must not have moved anything.
+  assert.equal(policy.scopeFor(agent()).root, join(facet, 'inner'))
+})
+
+test('the facet tool needs exactly one folder to focus on', async () => {
+  const { captured } = harness()
+  const exec = { agent: agent() }
+  await assert.rejects(() => captured.tool.execute({ action: 'focus' }, exec), /exactly one folder/)
+  await assert.rejects(
+    () => captured.tool.execute({ action: 'focus', paths: ['inner', '../other'] }, exec),
+    /exactly one folder/,
+  )
+})
+
+test('reset lands on the scope the user declared, never back on the session directory', async () => {
+  const { captured, policy } = harness({
+    config: { mode: 'deny', scopes: { 'session-1': { focus: 'src/controllers/room' } } },
+  })
+  const exec = { agent: agent(root) }
+
+  // The user declared this conversation to be about the room controller, so the
+  // session is already narrower than the directory it was started in.
+  assert.equal(policy.scopeFor(agent(root)).root, facet)
+
+  await captured.tool.execute({ action: 'focus', paths: ['src/controllers/room/inner'] }, exec)
+  assert.equal(policy.scopeFor(agent(root)).root, join(facet, 'inner'))
+
+  // Clearing the agent's side has to land on the user's declaration. Landing on
+  // the session directory would make `reset` a widening.
+  await captured.tool.execute({ action: 'reset' }, exec)
+  assert.equal(policy.scopeFor(agent(root)).root, facet)
+})
+
 test('the facet tool refuses a call it cannot act on', async () => {
   const { captured } = harness()
   const exec = { agent: agent() }

test/policy.test.js

@@ -93,3 +93,97 @@ test('prompt placements are carried, so the preset row needs no config', () => {
   assert.equal(createFacetPolicy({ mode: 'ask', sectionOrder: 7, contextOrder: 8 }).sectionOrder, 7)
   assert.equal(createFacetPolicy({ mode: 'ask', sectionOrder: 7, contextOrder: 8 }).contextOrder, 8)
 })
+
+// ── per-session scope ────────────────────────────────────────────────────────
+//
+// The declaration is the user's, written from the browser panel; the narrowing
+// is the agent's, held in memory. Everything below is about which of the two
+// wins, and the answer is always "the narrower one, and never a stale agent
+// focus that the user has since narrowed past".
+
+test('a declared focus narrows the root, and the session directory stays the base', () => {
+  const policy = createFacetPolicy({
+    mode: 'deny',
+    scopes: { s1: { focus: 'src/controllers/room' } },
+  })
+  const scope = policy.scopeFor(agentAt('/w', 's1'))
+
+  assert.equal(scope.root, '/w/src/controllers/room')
+  // `cwd` is still where relative paths resolve from — a declaration written
+  // against the session keeps its meaning whatever the session focuses on.
+  assert.equal(scope.cwd, '/w')
+})
+
+test('a declaration is read live, so the panel needs no remount', () => {
+  const scopes = {}
+  const policy = createFacetPolicy({ mode: 'deny', scopes })
+  assert.equal(policy.scopeFor(agentAt('/w', 's1')).root, '/w')
+
+  // What a panel write does to the running reference.
+  scopes.s1 = { focus: 'src/module' }
+  assert.equal(policy.scopeFor(agentAt('/w', 's1')).root, '/w/src/module')
+})
+
+test('declared extras join the deployment seed and the session grants', () => {
+  const policy = createFacetPolicy({
+    mode: 'deny',
+    extraRoots: ['seed'],
+    scopes: { s1: { focus: 'src/room', extras: ['shared', '/abs/common'] } },
+  })
+  policy.grant('s1', ['granted'], '/w')
+
+  assert.deepEqual(policy.scopeFor(agentAt('/w', 's1')).extras, [
+    '/w/seed',
+    '/w/shared',
+    '/abs/common',
+    '/w/granted',
+  ])
+})
+
+test('an agent narrowing is honoured while it stays inside the declared root', () => {
+  const policy = createFacetPolicy({ mode: 'deny', scopes: { s1: { focus: 'src' } } })
+  policy.narrowTo('s1', '/w/src/room')
+
+  assert.equal(policy.scopeFor(agentAt('/w', 's1')).root, '/w/src/room')
+  assert.equal(policy.narrowFor('s1'), '/w/src/room')
+})
+
+test('a narrowing the user has since narrowed past is dropped, not honoured', () => {
+  const scopes = { s1: { focus: 'src' } }
+  const policy = createFacetPolicy({ mode: 'deny', scopes })
+  policy.narrowTo('s1', '/w/src/room')
+  assert.equal(policy.scopeFor(agentAt('/w', 's1')).root, '/w/src/room')
+
+  // The user narrows to a sibling: the agent's focus is now outside the scope
+  // they declared. Honouring it would put the session back where the user had
+  // just decided it should not be.
+  scopes.s1 = { focus: 'src/other' }
+  assert.equal(policy.scopeFor(agentAt('/w', 's1')).root, '/w/src/other')
+})
+
+test('reset and forget drop the agent side and leave the declaration alone', () => {
+  const policy = createFacetPolicy({ mode: 'deny', scopes: { s1: { focus: 'src', extras: ['shared'] } } })
+  policy.narrowTo('s1', '/w/src/room')
+  policy.grant('s1', ['granted'], '/w')
+
+  policy.reset('s1')
+  // Back to what the user declared — narrower than the session, never wider.
+  assert.equal(policy.scopeFor(agentAt('/w', 's1')).root, '/w/src')
+  assert.deepEqual(policy.grantsFor('s1'), [])
+  assert.deepEqual(policy.scopeFor(agentAt('/w', 's1')).extras, ['/w/shared'])
+
+  policy.narrowTo('s1', '/w/src/room')
+  policy.forget('s1')
+  assert.equal(policy.narrowFor('s1'), undefined)
+  assert.equal(policy.scopeFor(agentAt('/w', 's1')).root, '/w/src')
+})
+
+test('junk in a declaration is ignored rather than thrown on', () => {
+  const policy = createFacetPolicy({
+    mode: 'deny',
+    scopes: { s1: { focus: '   ', extras: ['ok', '', 42, null] }, s2: 'not an object' },
+  })
+  assert.equal(policy.scopeFor(agentAt('/w', 's1')).root, '/w')
+  assert.deepEqual(policy.scopeFor(agentAt('/w', 's1')).extras, ['/w/ok'])
+  assert.equal(policy.scopeFor(agentAt('/w', 's2')).root, '/w')
+})

test/scope.test.js

@@ -82,7 +82,7 @@ test('facetContextText carries the binding that does change', () => {
     deny,
     'facet: /w/src/room\n' +
       'granted outside it: src/shared\n' +
-      'outside the facet: refused — `facet action=add` asks the user to grant a path, and is the only way to widen the scope',
+      'outside the facet: refused — ask the user to widen the facet from its context panel, or with `facet action=add` where that can be granted',
   )
 
   // The binding is the only half that can follow a live edit, so the two modes
@@ -97,14 +97,14 @@ test('facetContextText carries the binding that does change', () => {
 test('a session with no approval channel says so instead of promising a question', () => {
   // `approval: never` refuses every ask before an answerer is consulted, so the
   // mode stops mattering: `ask` and `deny` both end in a refusal, and
-  // `facet action=add` cannot be approved either. `canAsk: false` is the one
+  // `facet action=add` cannot be granted either. `canAsk: false` is the one
   // input that collapses them, and it has to name the mechanism that still
-  // works — `extraRoots` is configuration, not a per-conversation grant.
+  // works — the context panel, which the user owns.
   for (const mode of ['ask', 'deny']) {
     const text = facetContextText({ cwd: '/w', root: '/w/src/room', extras: [], mode, canAsk: false })
-    assert.match(text, /outside the facet: refused — approval prompts are off in this session/)
-    assert.match(text, /`facet action=add` cannot be approved either/)
-    assert.match(text, /`extraRoots`/)
+    assert.match(text, /outside the facet: refused — this session has no approval channel/)
+    assert.match(text, /`facet action=add` cannot be granted/)
+    assert.match(text, /context panel/)
     assert.doesNotMatch(text, /put to the user as a question/)
   }