v1.68.3.0 fix(pairing): re-pair to narrow revokes the old grant on the spot (#2665)

* fix(pairing): reject reserved clientId 'root' at all token writers

'root' is the sentinel checkScope/checkDomain/checkRate and the server
command gate use for the omnipotent caller, so a scoped token carrying it
bypasses every enforcement path. Add ReservedClientIdError + a shared
assertValidClientId; createToken/createSetupKey throw, restoreRegistry
skips-and-logs (a corrupt state file must not brick boot). /pair and /token
surface it as a named 400, and the CLI fast-fails --client root.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* fix(pairing): release tab ownership on revoke

tabOwnership cleared only on tab close, so after DELETE /token a same-name
re-pair inherited the revoked agent's authenticated tabs (own-only access
keys on owner === clientId). Add BrowserManager.releaseClientTabs and run it
unconditionally in DELETE /token (ownership outlives the token, so an
expired-token client can still own tabs); 404 only when both nothing was
revoked and nothing released. Response now carries tabs_released.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* v1.68.3.0 fix(pairing): re-pair to narrow revokes the old grant on the spot

POST /pair minted a new setup key but never touched the agent's live
session, so re-pairing --client X --restrict read while X was connected (or
whose 5-min key expired unexchanged) left the original full-access session,
eval included, alive up to 24h.

A reducing re-pair (fewer scopes, tighter domains, lower rate, stricter tab
policy) now revokes the live session and releases its tabs before minting
the new key (grantReducesAccess + revokeClientFully; superseded in the
response). Non-reducing re-pairs keep the session and only drop stale PENDING
setup keys, so a broaden/refresh never strands a working agent and a
narrowing re-pair issued before the agent connects can't leave the old broad
key exchangeable. Revoke happens before mint (revokeToken deletes all of a
client's tokens). CLI prints a version-skew-safe supersede notice and warns
when a re-pair-shaped call omits --client. Docs + CHANGELOG + VERSION.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* fix(pairing): harden re-pair per adversarial review

Adversarial review of the diff found four issues, now fixed:
- Validate the requested grant BEFORE the supersede revoke: a reducing
  re-pair with a bad scope/rate no longer destroys the live session and
  then fails to mint a replacement (assertValidTokenOptions runs up front).
- A re-pair with no live session releases tabs orphaned by an expired
  incarnation, closing the tab-inheritance gap /pair had (DELETE /token
  already released unconditionally).
- Test the DELETE /token revoked=0/tabs>0 path and the /pair orphaned-tab
  release at the handler level (HTTP e2e can't, headless owns no tabs).
- Test the CLI --client root fast-fail; fix its null-guard (parseFlag
  returns null when --client is absent).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

---------

Co-authored-by: Garry Tan <garry@ycombinator.com>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

browse/src/browser-manager.ts

@@ -1056,6 +1056,25 @@ export class BrowserManager {
     this.tabOwnership.set(tabId, toClientId);
   }
 
+  /**
+   * Release all tab ownership held by a client (called on revoke / reducing
+   * re-pair). Deletes the ownership entries so an own-only client re-pairing
+   * under the same name can no longer inherit the revoked agent's
+   * authenticated tabs (checkTabAccess gates own-only on owner === clientId).
+   * Tabs are NOT closed — leaving the page open is the local human's call, not
+   * the daemon's; the residual is a root-only tab. Returns the released ids.
+   */
+  releaseClientTabs(clientId: string): number[] {
+    const released: number[] = [];
+    for (const [tabId, owner] of this.tabOwnership) {
+      if (owner === clientId) {
+        this.tabOwnership.delete(tabId);
+        released.push(tabId);
+      }
+    }
+    return released;
+  }
+
   async getTabListWithTitles(): Promise<Array<{ id: number; url: string; title: string; active: boolean }>> {
     const tabs: Array<{ id: number; url: string; title: string; active: boolean }> = [];
     for (const [id, page] of this.pages) {

browse/src/cli.ts

@@ -1225,6 +1225,14 @@ async function tunnelAgents(): Promise<number> {
  * opposite of the user's intent. And `control` never rides in via --restrict:
  * browser-wide destructive ops stay behind the explicit --control flag. */
 function validatePairAgentFlags(args: string[]): void {
+  // `root` is the sentinel that bypasses all scope/domain/rate/tab enforcement;
+  // naming an agent that way would silently un-sandbox it. Reject client-side
+  // before hitting the daemon (the server rejects it too).
+  const client = parseFlag(args, '--client');
+  if (client && client.trim().toLowerCase() === 'root') {
+    console.error("[browse] --client 'root' is reserved — it would bypass all scope enforcement. Choose another name.");
+    process.exit(1);
+  }
   // hasFlag/parseFlag are exact-token matches, so `--restrict=read` would
   // sail past every check below and silently grant FULL access.
   if (args.some(a => a.startsWith('--restrict='))) {
@@ -1305,8 +1313,21 @@ async function handlePairAgent(state: ServerState, args: string[]): Promise<void
     scopes: string[];
     tunnel_url: string | null;
     server_url: string;
+    superseded?: { tokens_deleted: number; tabs_released: number };
   };
 
+  // Version-skew safe: only speak when the daemon actually superseded a live
+  // session (old daemons omit the field, so a new CLI never claims a false one).
+  if (pairData.superseded && pairData.superseded.tokens_deleted > 0) {
+    console.log(`[browse] Superseded the previous session for "${clientName}" (${pairData.superseded.tokens_deleted} token(s), ${pairData.superseded.tabs_released} tab(s) released). The agent must reconnect with the new key.`);
+  }
+  // A re-pair narrows/changes an EXISTING agent only when it reuses that agent's
+  // --client name. Without one, this mints a brand-new agent and the old grant
+  // lives on — warn when the intent looks like a re-pair.
+  if (!parseFlag(args, '--client') && (restrict || domains)) {
+    console.warn(`[browse] No --client given: this pairs a NEW agent and does NOT narrow an existing one. To change an agent's access, re-pair with its --client name (see 'browse tunnel agents').`);
+  }
+
   // Determine the URL to use
   let serverUrl: string;
   if (pairData.tunnel_url) {

browse/src/server.ts

@@ -32,7 +32,8 @@ import {
   checkRate, createToken, createSetupKey, exchangeSetupKey, revokeToken,
   listTokens, recordCommand,
   isRootToken, checkConnectRateLimit, type TokenInfo, type ScopeCategory,
-  DEFAULT_PAIR_SCOPES, InvalidScopeError,
+  DEFAULT_PAIR_SCOPES, InvalidScopeError, ReservedClientIdError, assertValidClientId,
+  assertValidTokenOptions, revokeSetupKeys, getClientSession, grantReducesAccess,
 } from './token-registry';
 import { validateTempPath } from './path-security';
 import { resolveConfig, ensureStateDir, readVersionHash, resolveChromiumProfile, cleanSingletonLocks, isPairAgentEnabled } from './config';
@@ -2318,9 +2319,9 @@ export function buildFetchHandler(cfg: ServerConfig): ServerHandle {
             agent: session.clientId,
           }), { status: 200, headers: { 'Content-Type': 'application/json' } });
         } catch (err) {
-          // Name the caller's typo (bad scope, negative rateLimit) instead of
-          // hiding it behind the generic body error.
-          if (err instanceof InvalidScopeError) {
+          // Name the caller's typo (bad scope, negative rateLimit, reserved
+          // clientId) instead of hiding it behind the generic body error.
+          if (err instanceof InvalidScopeError || err instanceof ReservedClientIdError) {
             return new Response(JSON.stringify({ error: err.message }), {
               status: 400, headers: { 'Content-Type': 'application/json' },
             });
@@ -2348,13 +2349,18 @@ export function buildFetchHandler(cfg: ServerConfig): ServerHandle {
           });
         }
         const revoked = revokeToken(clientId);
-        if (!revoked) {
+        // Release tabs UNCONDITIONALLY: ownership outlives the token (it clears
+        // only on tab close), so a client whose token already expired can still
+        // own tabs. Gating release on a revoke hit would orphan that ownership
+        // and let a same-name re-pair inherit an authenticated tab.
+        const tabsReleased = browserManager.releaseClientTabs(clientId).length;
+        if (!revoked && tabsReleased === 0) {
           return new Response(JSON.stringify({ error: `Agent "${clientId}" not found` }), {
             status: 404, headers: { 'Content-Type': 'application/json' },
           });
         }
-        console.log(`[browse] Revoked ${revoked} token(s) for: ${clientId}`);
-        return new Response(JSON.stringify({ revoked: clientId, tokens_deleted: revoked }), {
+        console.log(`[browse] Revoked ${revoked} token(s), released ${tabsReleased} tab(s) for: ${clientId}`);
+        return new Response(JSON.stringify({ revoked: clientId, tokens_deleted: revoked, tabs_released: tabsReleased }), {
           status: 200, headers: { 'Content-Type': 'application/json' },
         });
       }
@@ -2392,6 +2398,9 @@ export function buildFetchHandler(cfg: ServerConfig): ServerHandle {
         }
         try {
           const pairBody = await req.json() as any;
+          // Reject a reserved/invalid clientId up front (createSetupKey enforces
+          // it too, but this makes the 400 unambiguous and skips the teardown).
+          if (pairBody.clientId !== undefined) assertValidClientId(pairBody.clientId);
           // Default: DEFAULT_PAIR_SCOPES (full page access). The trust boundary
           // is the pairing ceremony itself, not the scope. --control adds
           // browser-wide destructive commands (stop, restart, disconnect).
@@ -2406,6 +2415,44 @@ export function buildFetchHandler(cfg: ServerConfig): ServerHandle {
           const scopes = pairBody.control || pairBody.admin
             ? [...DEFAULT_PAIR_SCOPES, 'control' as const]
             : ((pairBody.scopes || [...DEFAULT_PAIR_SCOPES]) as ScopeCategory[]);
+          // D1: a re-pair supersedes prior grants. ALWAYS drop stale setup keys
+          // so a superseded broad key can never be exchanged — this closes the
+          // shadow-key hole where a narrowing re-pair before the agent connects
+          // would otherwise leave the old broad key live. Revoke the live
+          // SESSION only when the new grant actually reduces access, so a
+          // broaden/refresh never strands a working agent mid-task. Compare
+          // against the resolved grant (not raw pairBody) so dropping 'control'
+          // or a default re-pair is classified correctly. Revoke runs BEFORE
+          // createSetupKey — revokeToken deletes all of a clientId's tokens, so
+          // minting first would nuke the fresh key.
+          const grant = {
+            scopes: [...scopes] as ScopeCategory[],
+            domains: pairBody.domains as string[] | undefined,
+            rateLimit: pairBody.rateLimit ?? 10,
+            tabPolicy: 'own-only' as const,
+          };
+          // Validate BEFORE any revoke (createSetupKey validates too, but that
+          // runs after the teardown below). A bad scope or negative rateLimit
+          // must 400 without knocking a live session offline — otherwise a
+          // reducing re-pair with a typo (--restrict red) destroys the session
+          // and mints no replacement.
+          assertValidTokenOptions(grant.scopes, grant.rateLimit);
+          const priorSession = pairBody.clientId ? getClientSession(pairBody.clientId) : null;
+          let superseded: { tokens_deleted: number; tabs_released: number } | undefined;
+          if (priorSession && grantReducesAccess(priorSession, grant)) {
+            const tokensDeleted = revokeToken(pairBody.clientId);
+            const tabsReleased = browserManager.releaseClientTabs(pairBody.clientId).length;
+            superseded = { tokens_deleted: tokensDeleted, tabs_released: tabsReleased };
+            console.log(`[browse] Superseded ${tokensDeleted} token(s), released ${tabsReleased} tab(s) for reducing re-pair: ${pairBody.clientId}`);
+          } else if (pairBody.clientId) {
+            revokeSetupKeys(pairBody.clientId);
+            // No live session, but tab ownership outlives token expiry: free any
+            // tabs orphaned by an expired session so this re-pair can't inherit
+            // an earlier incarnation's authenticated pages (mirrors DELETE
+            // /token's unconditional release). A live-session broaden keeps its
+            // tabs — the working agent still owns them.
+            if (!priorSession) browserManager.releaseClientTabs(pairBody.clientId);
+          }
           const setupKey = createSetupKey({
             clientId: pairBody.clientId,
             scopes: [...scopes],
@@ -2440,11 +2487,12 @@ export function buildFetchHandler(cfg: ServerConfig): ServerHandle {
             scopes: setupKey.scopes,
             tunnel_url: verifiedTunnelUrl,
             server_url: `http://127.0.0.1:${browsePort}`,
+            ...(superseded ? { superseded } : {}),
           }), { status: 200, headers: { 'Content-Type': 'application/json' } });
         } catch (err) {
-          // Name the caller's typo (bad scope, negative rateLimit) instead of
-          // hiding it behind the generic body error.
-          if (err instanceof InvalidScopeError) {
+          // Name the caller's typo (bad scope, negative rateLimit, reserved
+          // clientId) instead of hiding it behind the generic body error.
+          if (err instanceof InvalidScopeError || err instanceof ReservedClientIdError) {
             return new Response(JSON.stringify({ error: err.message }), {
               status: 400, headers: { 'Content-Type': 'application/json' },
             });

browse/src/token-registry.ts

@@ -106,7 +106,7 @@ export const DEFAULT_PAIR_SCOPES: readonly ScopeCategory[] = ['read', 'write', '
  */
 export class InvalidScopeError extends Error {}
 
-function assertValidTokenOptions(scopes: readonly string[], rateLimit: number): void {
+export function assertValidTokenOptions(scopes: readonly string[], rateLimit: number): void {
   const validScopes: ScopeCategory[] = ['read', 'write', 'admin', 'meta', 'control'];
   for (const s of scopes) {
     if (!validScopes.includes(s as ScopeCategory)) {
@@ -116,6 +116,26 @@ function assertValidTokenOptions(scopes: readonly string[], rateLimit: number):
   if (rateLimit < 0) throw new InvalidScopeError('rateLimit must be >= 0');
 }
 
+/**
+ * Typed error for a reserved or malformed clientId. `root` is the sentinel that
+ * checkScope/checkDomain/checkRate and the server command gate use to mean "the
+ * omnipotent root caller" (validateToken:360), so a scoped token carrying it
+ * would bypass every enforcement path. Empty/non-string ids collapse distinct
+ * agents together and break revoke-by-clientId. Request-path writers throw;
+ * restoreRegistry skips-and-logs so one bad state-file entry can't drop later
+ * sessions or brick boot.
+ */
+export class ReservedClientIdError extends Error {}
+
+export function assertValidClientId(clientId: unknown): asserts clientId is string {
+  if (typeof clientId !== 'string' || clientId.trim() === '') {
+    throw new ReservedClientIdError('clientId must be a non-empty string');
+  }
+  if (clientId.trim().toLowerCase() === 'root') {
+    throw new ReservedClientIdError("clientId 'root' is reserved");
+  }
+}
+
 // ─── Types ──────────────────────────────────────────────────────
 
 export interface TokenInfo {
@@ -234,6 +254,7 @@ export function createToken(opts: CreateTokenOptions): TokenInfo {
   } = opts;
 
   // Validate inputs
+  assertValidClientId(clientId);
   assertValidTokenOptions(scopes, rateLimit);
   if (expiresSeconds !== null && expiresSeconds !== undefined && expiresSeconds < 0) {
     throw new Error('expiresSeconds must be >= 0 or null');
@@ -276,6 +297,9 @@ export function createToken(opts: CreateTokenOptions): TokenInfo {
  * Setup keys expire in 5 minutes and can only be exchanged once.
  */
 export function createSetupKey(opts: Omit<CreateTokenOptions, 'clientId'> & { clientId?: string }): TokenInfo {
+  // Only validate when a clientId is supplied; an omitted one gets a safe
+  // generated `remote-<ts>` default below.
+  if (opts.clientId !== undefined) assertValidClientId(opts.clientId);
   const scopes = opts.scopes || ['read', 'write'];
   // ?? not ||: rateLimit 0 is documented as "unlimited" and must survive.
   const rateLimit = opts.rateLimit ?? 10;
@@ -471,6 +495,110 @@ export function revokeToken(clientId: string): number {
   return deleted;
 }
 
+/**
+ * Revoke the PENDING (unspent) setup keys for a client, leaving any live
+ * session AND spent keys untouched. A re-pair always drops pending keys so a
+ * superseded broad key can never be exchanged — this closes the shadow-key
+ * hole (a reducing re-pair before the agent connects would otherwise leave the
+ * old broad key live) without touching the spent key that #2646 keeps for
+ * idempotent re-exchange on a tunnel drop. Returns the number deleted.
+ */
+export function revokeSetupKeys(clientId: string): number {
+  let deleted = 0;
+  for (const [token, info] of tokens) {
+    // usesRemaining !== 0 = still exchangeable (pending). Spent keys (0) are
+    // harmless: their session is either kept here or revoked on the reduce path.
+    if (info.clientId === clientId && info.type === 'setup' && info.usesRemaining !== 0) {
+      tokens.delete(token);
+      deleted++;
+    }
+  }
+  return deleted;
+}
+
+/** The live (non-expired) session token for a client, if any. */
+export function getClientSession(clientId: string): TokenInfo | null {
+  const now = new Date();
+  for (const info of tokens.values()) {
+    if (info.clientId !== clientId || info.type !== 'session') continue;
+    if (info.expiresAt && new Date(info.expiresAt) < now) continue;
+    return info;
+  }
+  return null;
+}
+
+/** The effective grant a re-pair is requesting, resolved to concrete values. */
+export interface ResolvedGrant {
+  scopes: ScopeCategory[];
+  domains?: string[];
+  rateLimit: number;
+  tabPolicy: 'own-only' | 'shared';
+}
+
+/**
+ * Does `grant` remove any capability the live `prior` session holds? Drives the
+ * /pair supersede decision: a reducing re-pair revokes the old session
+ * immediately (the narrowing must not wait for a reconnect that may never
+ * happen); a broaden/refresh leaves it working (no outage). Fails toward
+ * revocation on an unprovable domain superset — a spurious revoke costs one
+ * reconnect, a missed one leaves wide access live.
+ */
+export function grantReducesAccess(prior: TokenInfo, grant: ResolvedGrant): boolean {
+  return scopesReduced(prior.scopes, grant.scopes)
+    || domainsReduced(prior.domains, grant.domains)
+    || rateReduced(prior.rateLimit, grant.rateLimit)
+    || tabPolicyReduced(prior.tabPolicy, grant.tabPolicy);
+}
+
+function scopesReduced(prior: ScopeCategory[], next: ScopeCategory[]): boolean {
+  // Any scope the prior held that the new grant omits (also catches dropping 'control').
+  return prior.some(s => !next.includes(s));
+}
+
+function domainsReduced(prior: string[] | undefined, next: string[] | undefined): boolean {
+  const priorUnrestricted = !prior || prior.length === 0;
+  const nextUnrestricted = !next || next.length === 0;
+  if (priorUnrestricted) return !nextUnrestricted; // universe → restricted = reduce
+  if (nextUnrestricted) return false;              // restricted → universe = broaden
+  // Both restricted: reduced if any host the prior allowlist admits is no longer
+  // admitted by the new one. Approximate over patterns — prior is covered iff
+  // every prior pattern is covered by some next pattern; anything unprovable
+  // counts as reduced (fail toward revocation).
+  return prior!.some(p => !next!.some(n => domainGlobCovers(n, p)));
+}
+
+/** Does allowlist pattern `wide` admit every host that `narrow` admits? Mirrors
+ * matchDomainGlob's suffix/exact rules. */
+function domainGlobCovers(wide: string, narrow: string): boolean {
+  if (wide === narrow) return true;
+  const wideGlob = wide.startsWith('*.');
+  if (wideGlob) {
+    const wideSuffix = wide.slice(1); // ".example.com"
+    const wideApex = wide.slice(2);   // "example.com"
+    if (!narrow.startsWith('*.')) {
+      // narrow is an exact host; covered iff the wide glob matches it.
+      return narrow === wideApex || narrow.endsWith(wideSuffix);
+    }
+    // narrow is also a glob; its apex must fall under the wide suffix.
+    const narrowApex = narrow.slice(2);
+    return narrowApex === wideApex || narrowApex.endsWith(wideSuffix);
+  }
+  // wide is an exact host: covers only the identical host (handled by === above).
+  return false;
+}
+
+function rateReduced(prior: number, next: number): boolean {
+  const priorUnlimited = prior <= 0; // 0 = unlimited
+  const nextUnlimited = next <= 0;
+  if (priorUnlimited) return !nextUnlimited; // unlimited → capped = reduce
+  if (nextUnlimited) return false;           // capped → unlimited = broaden
+  return next < prior;                       // both capped: a lower cap = reduce
+}
+
+function tabPolicyReduced(prior: 'own-only' | 'shared', next: 'own-only' | 'shared'): boolean {
+  return prior === 'shared' && next === 'own-only';
+}
+
 /**
  * Rotate the root token. All scoped tokens are invalidated.
  * Returns the new root token.
@@ -535,6 +663,16 @@ export function restoreRegistry(state: TokenRegistryState): void {
     // Skip expired tokens
     if (data.expiresAt && new Date(data.expiresAt) < now) continue;
 
+    // Skip-and-log rather than throw: a hand-edited or corrupt state file must
+    // not brick boot or drop every later valid session. A persisted clientId
+    // 'root' would otherwise inject a token that bypasses all scope checks.
+    try {
+      assertValidClientId(clientId);
+    } catch (err) {
+      console.warn(`[browse] restoreRegistry: skipping invalid clientId ${JSON.stringify(clientId)}: ${err instanceof Error ? err.message : String(err)}`);
+      continue;
+    }
+
     tokens.set(data.token, {
       ...data,
       clientId,