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the new key (grantReducesAccess + revokeClientFully; superseded in the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>

browse/src/cli.ts

@@ -1313,8 +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+    superseded?: { tokens_deleted: number; tabs_released: number };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+  // Version-skew safe: only speak when the daemon actually superseded a live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superseded && pairData.superseded.tokens_deleted 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+    console.log(`[browse] Superseded the previous session for "${clientName}" (${pairData.superseded.tokens_deleted} token(s), ${pairData.superseded.tabs_released} tab(s) released).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, ReservedClientIdError,
+  DEFAULT_PAIR_SCOPES, InvalidScopeError, ReservedClientIdError, assertValidClientId,
+  revokeSetupKeys, getClientSession, grantReducesAccess,
 } from './token-registry';
 import { validateTempPath } from './path-security';
 import { resolveConfig, ensureStateDir, readVersionHash, resolveChromiumProfile, cleanSingletonLocks, isPairAgentEnabled } from './config';
@@ -2397,6 +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).
@@ -2411,6 +2415,32 @@ 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,
+          };
+          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: ${pairBody.clientId}`);
+          } else if (pairBody.clientId) {
+            revokeSetupKeys(pairBody.clientId);
+          }
           const setupKey = createSetupKey({
             clientId: pairBody.clientId,
             scopes: [...scopes],
@@ -2445,6 +2475,7 @@ export function buildFetchHandler(cfg: ServerConfig): ServerHandle {
             scopes: setupKey.scopes,
             tunnel_url: verifiedTunnelUrl,
             server_url: `http://127.0.0.1:${browsePort}`,
+            ...(superseded ? { superseded } : {}),
           }), { status: 200, headers: { 'Content-Type': 'application/json' } });
         } catch (err) {
           // Name the caller's typo (bad scope, negative rateLimit, reserved

browse/src/token-registry.ts

@@ -495,6 +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.

browse/test/pair-agent-e2e.test.ts

@@ -318,6 +318,61 @@ describe('pair-agent flow end-to-end (HTTP only, no ngrok)', () => {
     expect(body.error).not.toBe('Invalid request body');
   });
 
+  // ─── D1: a reducing re-pair supersedes the prior grant immediately ────
+
+  const pairAs = async (body: any) => (await (await fetch(`${daemon.baseUrl}/pair`, {
+    method: 'POST',
+    headers: { 'Content-Type': 'application/json', Authorization: `Bearer ${daemon.token}` },
+    body: JSON.stringify(body),
+  })).json()) as any;
+  const connectKey = async (setup_key: string) => {
+    const r = await fetch(`${daemon.baseUrl}/connect`, {
+      method: 'POST', headers: { 'Content-Type': 'application/json' }, body: JSON.stringify({ setup_key }),
+    });
+    return { status: r.status, body: await r.json().catch(() => ({})) as any };
+  };
+  const statusWith = (token: string) => fetch(`${daemon.baseUrl}/command`, {
+    method: 'POST', headers: { 'Content-Type': 'application/json', Authorization: `Bearer ${token}` },
+    body: JSON.stringify({ command: 'status', args: [] }),
+  });
+
+  test('reducing re-pair revokes the prior session immediately, without exchanging the new key', async () => {
+    const { setup_key: k1 } = await pairAs({ clientId: 'reduce-me' });      // broad
+    const { body: c1 } = await connectKey(k1);
+    const s1 = c1.token as string;
+    expect((await statusWith(s1)).status).not.toBe(401);                    // works
+    // Narrow WITHOUT exchanging the new key — this is the whole bug.
+    const rp = await pairAs({ clientId: 'reduce-me', scopes: ['read'] });
+    expect(rp.superseded?.tokens_deleted).toBeGreaterThanOrEqual(1);
+    expect((await statusWith(s1)).status).toBe(401);                        // old session revoked
+    // The new narrow key still works and yields the reduced scope.
+    const c2 = await connectKey(rp.setup_key);
+    expect(c2.status).toBe(200);
+    expect(c2.body.scopes).toEqual(['read']);
+    expect((await statusWith(c2.body.token)).status).not.toBe(401);
+  });
+
+  test('reducing re-pair BEFORE connect kills the stale broad setup key; only the narrow key works', async () => {
+    const { setup_key: broad } = await pairAs({ clientId: 'shadow' });      // never connected
+    const rp = await pairAs({ clientId: 'shadow', scopes: ['read'] });      // narrowing re-pair
+    expect(rp.superseded).toBeUndefined();                                  // no live session existed
+    expect((await connectKey(broad)).status).toBe(401);                     // stale broad key dead
+    const c = await connectKey(rp.setup_key);
+    expect(c.status).toBe(200);
+    expect(c.body.scopes).toEqual(['read']);                               // narrow key survives
+  });
+
+  test('broadening re-pair does NOT revoke the working session (no outage)', async () => {
+    const first = await pairAs({ clientId: 'broaden', scopes: ['read'] });
+    expect(first.superseded).toBeUndefined();                              // first pair supersedes nothing
+    const { body: c } = await connectKey(first.setup_key);
+    const s = c.token as string;
+    expect((await statusWith(s)).status).not.toBe(401);
+    const rp = await pairAs({ clientId: 'broaden', scopes: ['read', 'write'] }); // broaden
+    expect(rp.superseded).toBeUndefined();                                 // session not superseded
+    expect((await statusWith(s)).status).not.toBe(401);                    // still working
+  });
+
   // ─── D3: DELETE /token releases tabs unconditionally; 404 only when empty ─
 
   test('DELETE /token returns tabs_released and 404 only when nothing to revoke or release', async () => {

browse/test/token-registry.test.ts

@@ -7,6 +7,8 @@ import {
   serializeRegistry, restoreRegistry, checkConnectRateLimit,
   SCOPE_READ, SCOPE_WRITE, SCOPE_ADMIN, SCOPE_CONTROL, SCOPE_META,
   DEFAULT_PAIR_SCOPES, InvalidScopeError, ReservedClientIdError,
+  revokeSetupKeys, getClientSession, grantReducesAccess,
+  type TokenInfo, type ResolvedGrant,
   __resetRegistry,
 } from '../src/token-registry';
 
@@ -40,6 +42,16 @@ describe('token-registry', () => {
       expect(key.clientId.startsWith('remote-')).toBe(true);
     });
 
+    it('revokeSetupKeys drops only PENDING keys, keeping the spent key and the session', () => {
+      const k1 = createSetupKey({ clientId: 'x' });   // pending
+      exchangeSetupKey(k1.token);                      // k1 now spent + a session exists
+      createSetupKey({ clientId: 'x' });               // pending k2
+      expect(revokeSetupKeys('x')).toBe(1);            // only the pending k2
+      expect(getClientSession('x')).not.toBeNull();    // session kept
+      // The spent key survives for idempotent re-exchange (#2646).
+      expect(exchangeSetupKey(k1.token)).not.toBeNull();
+    });
+
     it('restoreRegistry skips a persisted "root" entry instead of injecting a bypass token', () => {
       restoreRegistry({ agents: {
         root: { token: 'gsk_sess_evil', type: 'session', scopes: ['read', 'write', 'admin', 'meta', 'control'], tabPolicy: 'shared', rateLimit: 0, expiresAt: null, createdAt: new Date().toISOString() } as any,
@@ -52,6 +64,49 @@ describe('token-registry', () => {
     });
   });
 
+  // D1: drives the /pair supersede decision. Direction matters — dropping an
+  // allowlisted domain is the reduction, not adding one; 0 = unlimited rate.
+  describe('grantReducesAccess (D1)', () => {
+    const prior = (o: Partial<TokenInfo> = {}): TokenInfo => ({
+      token: 't', clientId: 'c', type: 'session',
+      scopes: ['read', 'write', 'admin', 'meta'], tabPolicy: 'own-only',
+      rateLimit: 10, expiresAt: null, createdAt: '', commandCount: 0, ...o,
+    });
+    const grant = (o: Partial<ResolvedGrant> = {}): ResolvedGrant => ({
+      scopes: ['read', 'write', 'admin', 'meta'], rateLimit: 10, tabPolicy: 'own-only', ...o,
+    });
+
+    it('scopes: drop → reduce; add/equal → not; dropping control → reduce', () => {
+      expect(grantReducesAccess(prior({ scopes: ['read', 'write', 'admin', 'meta'] }), grant({ scopes: ['read'] }))).toBe(true);
+      expect(grantReducesAccess(prior({ scopes: ['read'] }), grant({ scopes: ['read', 'write'] }))).toBe(false);
+      expect(grantReducesAccess(prior({ scopes: ['read'] }), grant({ scopes: ['read'] }))).toBe(false);
+      expect(grantReducesAccess(prior({ scopes: ['read', 'control'] }), grant({ scopes: ['read'] }))).toBe(true);
+    });
+
+    it('domains: drop → reduce; add/equal → not; unrestricted→restricted → reduce; glob narrowing → reduce', () => {
+      expect(grantReducesAccess(prior({ domains: ['a.com', 'b.com'] }), grant({ domains: ['a.com'] }))).toBe(true);
+      expect(grantReducesAccess(prior({ domains: ['a.com'] }), grant({ domains: ['a.com', 'b.com'] }))).toBe(false);
+      expect(grantReducesAccess(prior({ domains: ['a.com'] }), grant({ domains: ['a.com'] }))).toBe(false);
+      expect(grantReducesAccess(prior({ domains: undefined }), grant({ domains: ['a.com'] }))).toBe(true);
+      expect(grantReducesAccess(prior({ domains: ['a.com'] }), grant({ domains: undefined }))).toBe(false);
+      expect(grantReducesAccess(prior({ domains: ['*.example.com'] }), grant({ domains: ['*.com'] }))).toBe(false); // widen
+      expect(grantReducesAccess(prior({ domains: ['*.com'] }), grant({ domains: ['*.example.com'] }))).toBe(true);  // narrow
+    });
+
+    it('rate (0 = unlimited): unlimited→capped → reduce; lower cap → reduce; higher/equal → not', () => {
+      expect(grantReducesAccess(prior({ rateLimit: 0 }), grant({ rateLimit: 10 }))).toBe(true);
+      expect(grantReducesAccess(prior({ rateLimit: 10 }), grant({ rateLimit: 5 }))).toBe(true);
+      expect(grantReducesAccess(prior({ rateLimit: 5 }), grant({ rateLimit: 10 }))).toBe(false);
+      expect(grantReducesAccess(prior({ rateLimit: 10 }), grant({ rateLimit: 10 }))).toBe(false);
+      expect(grantReducesAccess(prior({ rateLimit: 10 }), grant({ rateLimit: 0 }))).toBe(false); // → unlimited = broaden
+    });
+
+    it('tabPolicy: shared → own-only → reduce; the reverse → not', () => {
+      expect(grantReducesAccess(prior({ tabPolicy: 'shared' }), grant({ tabPolicy: 'own-only' }))).toBe(true);
+      expect(grantReducesAccess(prior({ tabPolicy: 'own-only' }), grant({ tabPolicy: 'shared' }))).toBe(false);
+    });
+  });
+
   describe('root token', () => {
     it('identifies root token correctly', () => {
       expect(isRootToken('root-token-for-tests')).toBe(true);