feat(THU-708): upgrade tinfoil and enable prompt caching

package.json

@@ -151,7 +151,7 @@
     "remark-parse": "^11.0.0",
     "tailwind-merge": "^3.3.1",
     "tailwindcss-animate": "^1.0.7",
-    "tinfoil": "^1.1.4",
+    "tinfoil": "^1.1.11",
     "unified": "^11.0.5",
     "uuid": "^14.0.0",
     "web-haptics": "^0.0.6",

src/ai/fetch.ts

@@ -21,7 +21,7 @@ import { getLocalSetting } from '@/stores/local-settings-store'
 import { hydrateAttachmentsAsFileParts } from '@/lib/attachments'
 import { hydrateQuotesAsText } from '@/lib/quotes'
 import { isSsoMode } from '@/lib/auth-mode'
-import { getAuthToken } from '@/lib/auth-token'
+import { getAuthToken, getUserCacheSecret } from '@/lib/auth-token'
 import { fetch as baseFetch } from '@/lib/fetch'
 import { isLoopbackHost } from '@/lib/mcp-url-validation'
 import { normalizeOpenAiBaseUrl } from '@/lib/openai-base-url'
@@ -109,7 +109,7 @@ let userTinfoilClient: SecureClient | null = null
  */
 const createSystemTinfoilClient = (cloudUrl: string): Promise<SecureClient> => {
   const clientPromise = import('tinfoil').then(
-    ({ SecureClient }) => new SecureClient({ baseURL: `${cloudUrl}/tinfoil` }),
+    ({ SecureClient }) => new SecureClient({ baseURL: `${cloudUrl}/tinfoil`, userCacheSecret: getUserCacheSecret() }),
   )
   void clientPromise.catch(() => systemTinfoilClients.delete(cloudUrl))
   systemTinfoilClients.set(cloudUrl, clientPromise)
@@ -163,7 +163,7 @@ const evictSystemTinfoilClient = (): void => {
 export const getTinfoilClient = async (): Promise<SecureClient> => {
   if (!userTinfoilClient) {
     const { SecureClient } = await import('tinfoil')
-    userTinfoilClient = new SecureClient()
+    userTinfoilClient = new SecureClient({ userCacheSecret: getUserCacheSecret() })
   }
   await userTinfoilClient.ready()
   return userTinfoilClient

src/lib/auth-token.test.ts

@@ -6,9 +6,11 @@ import { afterEach, beforeAll, beforeEach, describe, expect, it, mock } from 'bu
 import {
   clearAuthToken,
   clearDeviceId,
+  clearUserCacheSecret,
   getAuthenticatedHeaders,
   getAuthToken,
   getDeviceId,
+  getUserCacheSecret,
   onAuthTokenChangedInOtherTab,
   setAuthToken,
 } from './auth-token'
@@ -47,13 +49,15 @@ beforeAll(() => {
 beforeEach(() => {
   clearAuthToken()
   clearDeviceId()
+  clearUserCacheSecret()
 })
 
 // Mirror the beforeEach cleanup so the last test's token can't leak into the
 // next test file (AuthProvider's mount effect fires get-session on any token).
 afterEach(() => {
   clearAuthToken()
   clearDeviceId()
+  clearUserCacheSecret()
 })
 
 describe('auth-token', () => {
@@ -99,6 +103,28 @@ describe('auth-token', () => {
     })
   })
 
+  describe('getUserCacheSecret', () => {
+    it('returns 64-char hex', () => {
+      expect(getUserCacheSecret()).toMatch(/^[0-9a-f]{64}$/)
+    })
+
+    it('returns the same secret across calls', () => {
+      expect(getUserCacheSecret()).toBe(getUserCacheSecret())
+    })
+
+    it('differs from the device ID', () => {
+      expect(getUserCacheSecret()).not.toBe(getDeviceId())
+    })
+
+    it('generates a new secret after clearUserCacheSecret', () => {
+      const first = getUserCacheSecret()
+      clearUserCacheSecret()
+      const second = getUserCacheSecret()
+      expect(second).toMatch(/^[0-9a-f]{64}$/)
+      expect(second).not.toBe(first)
+    })
+  })
+
   describe('getAuthenticatedHeaders', () => {
     it('returns Authorization, X-Device-ID, and X-Device-Name when token and device ID exist', () => {
       setAuthToken('my-token')

src/lib/auth-token.ts

@@ -15,6 +15,7 @@ import { getDeviceDisplayName } from '@/lib/platform'
 
 const deviceIdKey = 'thunderbolt_device_id'
 const authTokenKey = 'thunderbolt_auth_token'
+const userCacheSecretKey = 'thunderbolt_user_cache_secret'
 
 /** Get or create device_id (from localStorage). */
 export const getDeviceId = (): string => {
@@ -44,6 +45,33 @@ export const clearDeviceId = (): void => {
   localStorage.removeItem(deviceIdKey)
 }
 
+/**
+ * Get or create the Tinfoil prompt-cache secret (from localStorage).
+ * Per-device, never synced (THU-708). Distinct from the device ID: it must
+ * only reach the attested enclave, never our backend.
+ *
+ * Plain localStorage is deliberate: the same store holds the bearer token,
+ * which grants full account access — strictly more than a cache-namespace
+ * key. The SDK needs the plaintext string, so a client-side wrapping key
+ * would add no protection (it would live in the same origin storage). Moves
+ * to encrypted storage together with the auth token (see file TODO).
+ */
+export const getUserCacheSecret = (): string => {
+  const existing = localStorage.getItem(userCacheSecretKey)
+  if (existing) {
+    return existing
+  }
+  const bytes = crypto.getRandomValues(new Uint8Array(32))
+  const secret = Array.from(bytes, (b) => b.toString(16).padStart(2, '0')).join('')
+  localStorage.setItem(userCacheSecretKey, secret)
+  return secret
+}
+
+/** Clear the prompt-cache secret (identity teardown — forces a new cache namespace). */
+export const clearUserCacheSecret = (): void => {
+  localStorage.removeItem(userCacheSecretKey)
+}
+
 /**
  * Build authenticated headers (Authorization + device identity).
  * Single source of truth for callers that cannot use the HTTP client (e.g. PowerSync connector).

src/lib/cleanup.ts

@@ -5,7 +5,7 @@
 import { disposeAllAdapters } from '@/acp/adapter-cache'
 import { clearIrohClientSecret } from '@/acp/iroh/iroh-transport'
 import { setSyncEnabled } from '@/db/powersync/sync-state'
-import { clearAuthToken, clearDeviceId } from '@/lib/auth-token'
+import { clearAuthToken, clearDeviceId, clearUserCacheSecret } from '@/lib/auth-token'
 import { resetAppDir } from '@/lib/fs'
 import { clearCachedSession } from '@/lib/session-cache'
 import { handleFullWipe } from '@/services/encryption'
@@ -70,6 +70,7 @@ export const clearLocalData = async (options?: ClearLocalDataOptions): Promise<v
   if (clearAuth) {
     clearAuthToken()
     clearDeviceId()
+    clearUserCacheSecret()
     // The iroh client secret is the bridge access credential (plaintext localStorage),
     // so it must be wiped with the other local creds on every identity teardown.
     clearIrohClientSecret()

src/testing-library.ts

@@ -2,7 +2,7 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-import { clearAuthToken, clearDeviceId } from '@/lib/auth-token'
+import { clearAuthToken, clearDeviceId, clearUserCacheSecret } from '@/lib/auth-token'
 import { clearMemoizeCache } from '@/lib/memoize'
 import { installFakeTimers } from '@/test-utils/fake-timers'
 import type { Clock } from '@sinonjs/fake-timers'
@@ -128,6 +128,7 @@ afterEach(() => {
   // get-session call against the next file's HTTP client.
   clearAuthToken()
   clearDeviceId()
+  clearUserCacheSecret()
 })
 
 /**