[SDK] Add pds and chat clients and the canonical client hooks (#11350)

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

src/lib/constants.ts

@@ -1,5 +1,6 @@
 import {type Insets, Platform} from 'react-native'
 import {type AppBskyActorDefs, BSKY_LABELER_DID} from '@atproto/api'
+import {type Service} from '@atproto/lex'
 
 import {type ProxyHeaderValue} from '#/state/session/agent'
 import {BLUESKY_PROXY_DID, CHAT_PROXY_DID, IS_DEV} from '#/env'
@@ -247,6 +248,21 @@ export const BLUESKY_PROXY_HEADER = {
   },
 }
 
+/**
+ * The chat service's proxy target, in the `did#service_id` form a lex client's
+ * `service` option takes. A client constructed with it emits `atproto-proxy:
+ * <this value>` on every request, which is what routes `chat.bsky.*` calls to
+ * the chat service.
+ *
+ * The DID comes from the env-configurable `CHAT_PROXY_DID` (via
+ * `EXPO_PUBLIC_CHAT_PROXY_DID`) rather than a hard-coded constant, so the
+ * target can be retargeted per environment.
+ *
+ * This is the client-level equivalent of {@link DM_SERVICE_HEADERS}, which
+ * carries the same value as a per-call header.
+ */
+export const CHAT_PROXY_SERVICE: Service = `${CHAT_PROXY_DID}#bsky_chat`
+
 export const DM_SERVICE_HEADERS = {
   'atproto-proxy': `${CHAT_PROXY_DID}#bsky_chat`,
 }

src/state/queries/trending/useGetTrendsQuery.ts

@@ -10,7 +10,7 @@ import {logger} from '#/logger'
 import {getContentLanguages} from '#/state/preferences/languages'
 import {STALE} from '#/state/queries'
 import {usePreferencesQuery} from '#/state/queries/preferences'
-import {useLexClient} from '#/state/session'
+import {useAppviewClient} from '#/state/session'
 import {app} from '#/lexicons'
 
 export const DEFAULT_LIMIT = 5
@@ -33,7 +33,7 @@ export const createGetTrendsQueryKey = (limit?: number) =>
   limit === undefined ? ['trends'] : ['trends', {limit}]
 
 export function useGetTrendsQuery(props: QueryProps = {}) {
-  const client = useLexClient()
+  const client = useAppviewClient()
   const {data: preferences} = usePreferencesQuery()
   const limit = props.limit ?? DEFAULT_LIMIT
   const mutedWords = useMemo(() => {

src/state/session/__tests__/clients-test.ts

@@ -13,9 +13,16 @@ jest.mock('jwt-decode', () => ({
   },
 }))
 
-import {app} from '#/lexicons'
+import {CHAT_PROXY_SERVICE} from '#/lib/constants'
+import {app, chat, com} from '#/lexicons'
 import {BskyAppAgent, PasswordSessionManager} from '../bridge-agent'
-import {agentToLexClient} from '../clients'
+import {
+  agentToAppviewClient,
+  agentToChatClient,
+  agentToPdsClient,
+  getUnauthenticatedThrowingClient,
+  NotAuthenticatedError,
+} from '../clients'
 import {sessionAccountToSessionData} from '../session-data'
 import {
   asFetch,
@@ -26,6 +33,7 @@ import {
   makeMockFetch,
   type MockFetch,
   SERVICE,
+  urlsOf,
 } from './mock-fetch'
 
 const PROFILE_BODY = {
@@ -70,7 +78,7 @@ function initFor(mock: MockFetch, nsid: string): RequestInit | undefined {
   return call?.[1]
 }
 
-describe('agentToLexClient', () => {
+describe('agentToAppviewClient', () => {
   let fetchMock: MockFetch
 
   beforeEach(() => {
@@ -81,9 +89,9 @@ describe('agentToLexClient', () => {
     const {agent: agentA} = setup(fetchMock)
     const {agent: agentB} = setup(fetchMock)
 
-    const clientA1 = agentToLexClient(agentA)
+    const clientA1 = agentToAppviewClient(agentA)
-    const clientA2 = agentToLexClient(agentA)
+    const clientA2 = agentToAppviewClient(agentA)
-    const clientB = agentToLexClient(agentB)
+    const clientB = agentToAppviewClient(agentB)
 
     expect(clientA1).toBeInstanceOf(Client)
     expect(clientA1).toBe(clientA2)
@@ -92,20 +100,23 @@ describe('agentToLexClient', () => {
 
   it('passes through the agent did', () => {
     const {agent} = setup(fetchMock)
-    expect(agentToLexClient(agent).did).toBe(DID)
+    expect(agentToAppviewClient(agent).did).toBe(DID)
   })
 
   it('reflects an undefined did on a logged-out agent', () => {
     const {agent} = setupPublic(fetchMock)
-    expect(agentToLexClient(agent).did).toBeUndefined()
+    expect(agentToAppviewClient(agent).did).toBeUndefined()
   })
 
   it('routes client.call through the agent to the network', async () => {
     const {agent} = setup(fetchMock)
 
-    const body = await agentToLexClient(agent).call(app.bsky.actor.getProfile, {
+    const body = await agentToAppviewClient(agent).call(
-      actor: HANDLE,
+      app.bsky.actor.getProfile,
-    })
+      {
+        actor: HANDLE,
+      },
+    )
 
     expect(body.handle).toBe(HANDLE)
     const call = fetchMock.mock.calls.find(c => {
@@ -121,7 +132,7 @@ describe('agentToLexClient', () => {
     const {agent} = setup(fetchMock)
     agent.configureProxy('did:web:api.bsky.app#bsky_appview')
 
-    await agentToLexClient(agent).call(app.bsky.actor.getProfile, {
+    await agentToAppviewClient(agent).call(app.bsky.actor.getProfile, {
       actor: HANDLE,
     })
 
@@ -135,7 +146,7 @@ describe('agentToLexClient', () => {
     const {agent} = setup(fetchMock)
     agent.configureLabelersHeader(['did:plc:labeler'])
 
-    await agentToLexClient(agent).call(app.bsky.actor.getProfile, {
+    await agentToAppviewClient(agent).call(app.bsky.actor.getProfile, {
       actor: HANDLE,
     })
 
@@ -155,7 +166,7 @@ describe('agentToLexClient', () => {
   it('sends the session access token', async () => {
     const {agent} = setup(fetchMock)
 
-    await agentToLexClient(agent).call(app.bsky.actor.getProfile, {
+    await agentToAppviewClient(agent).call(app.bsky.actor.getProfile, {
       actor: HANDLE,
     })
 
@@ -167,7 +178,7 @@ describe('agentToLexClient', () => {
 
   it('falls back to unauthenticated requests once the agent is disposed', async () => {
     const {agent} = setup(fetchMock)
-    const client = agentToLexClient(agent)
+    const client = agentToAppviewClient(agent)
     agent.dispose()
 
     await client.call(app.bsky.actor.getProfile, {actor: HANDLE})
@@ -177,3 +188,158 @@ describe('agentToLexClient', () => {
     expect(client.did).toBeUndefined()
   })
 })
+
+describe('agentToPdsClient', () => {
+  let fetchMock: MockFetch
+
+  beforeEach(() => {
+    fetchMock = makeProfileFetch()
+  })
+
+  it('memoizes one client per agent', () => {
+    const {agent: agentA} = setup(fetchMock)
+    const {agent: agentB} = setup(fetchMock)
+
+    const clientA1 = agentToPdsClient(agentA)
+    const clientA2 = agentToPdsClient(agentA)
+
+    expect(clientA1).toBeInstanceOf(Client)
+    expect(clientA1).toBe(clientA2)
+    expect(clientA1).not.toBe(agentToPdsClient(agentB))
+  })
+
+  it('is a distinct client from the appview client for the same agent', () => {
+    const {agent} = setup(fetchMock)
+    expect(agentToPdsClient(agent)).not.toBe(agentToAppviewClient(agent))
+  })
+
+  it('passes through the agent did', () => {
+    const {agent} = setup(fetchMock)
+    expect(agentToPdsClient(agent).did).toBe(DID)
+  })
+
+  it('sends the session access token', async () => {
+    const {agent} = setup(fetchMock)
+
+    await agentToPdsClient(agent).call(com.atproto.server.getSession, {})
+
+    const init = initFor(fetchMock, 'com.atproto.server.getSession')
+    expect(new Headers(init?.headers).get('authorization')).toBe(
+      'Bearer access-jwt',
+    )
+  })
+
+  it('emits neither the proxy nor the labeler header the agent is configured with', async () => {
+    /*
+     * The load-bearing difference from the appview client: this client wraps the
+     * session manager, below the agent layer that sets both headers, so a
+     * request reaches the account's PDS instead of being proxied onward.
+     */
+    const {agent} = setup(fetchMock)
+    agent.configureProxy('did:web:api.bsky.app#bsky_appview')
+    agent.configureLabelersHeader(['did:plc:labeler'])
+
+    await agentToPdsClient(agent).call(com.atproto.server.getSession, {})
+
+    const headers = new Headers(
+      initFor(fetchMock, 'com.atproto.server.getSession')?.headers,
+    )
+    expect(headers.get('atproto-proxy')).toBeNull()
+    expect(headers.get('atproto-accept-labelers')).toBeNull()
+  })
+
+  it('resolves the relative xrpc path against the account host', async () => {
+    /*
+     * lex-client hands its fetchHandler an origin-less `/xrpc/<nsid>` path; the
+     * session manager absolutizes it against dispatchUrl.
+     */
+    const {agent} = setup(fetchMock)
+
+    await agentToPdsClient(agent).call(com.atproto.server.getSession, {})
+
+    expect(urlsOf(fetchMock)).toContain(
+      `${SERVICE}/xrpc/com.atproto.server.getSession`,
+    )
+  })
+})
+
+describe('agentToChatClient', () => {
+  let fetchMock: MockFetch
+
+  beforeEach(() => {
+    fetchMock = makeProfileFetch()
+  })
+
+  it('memoizes one client per agent, distinct from the pds client', () => {
+    const {agent} = setup(fetchMock)
+
+    const client = agentToChatClient(agent)
+
+    expect(client).toBeInstanceOf(Client)
+    expect(client).toBe(agentToChatClient(agent))
+    expect(client).not.toBe(agentToPdsClient(agent))
+  })
+
+  it('emits the chat proxy header exactly once, with the session token', async () => {
+    const {agent} = setup(fetchMock)
+
+    /* the stub body fails listConvos output validation; headers are recorded pre-parse */
+    await agentToChatClient(agent)
+      .call(chat.bsky.convo.listConvos, {})
+      .catch(() => {})
+
+    const headers = new Headers(
+      initFor(fetchMock, 'chat.bsky.convo.listConvos')?.headers,
+    )
+    /*
+     * An exact match, not `toContain`: `Headers` comma-joins repeated entries
+     * for the same name, so a second contributor would show up here.
+     */
+    expect(headers.get('atproto-proxy')).toBe(CHAT_PROXY_SERVICE)
+    expect(headers.get('authorization')).toBe('Bearer access-jwt')
+  })
+
+  it('does not emit the agent labeler header', async () => {
+    const {agent} = setup(fetchMock)
+    agent.configureLabelersHeader(['did:plc:labeler'])
+
+    await agentToChatClient(agent)
+      .call(chat.bsky.convo.listConvos, {})
+      .catch(() => {})
+
+    const headers = new Headers(
+      initFor(fetchMock, 'chat.bsky.convo.listConvos')?.headers,
+    )
+    expect(headers.get('atproto-accept-labelers')).toBeNull()
+  })
+})
+
+describe('getUnauthenticatedThrowingClient', () => {
+  it('is a stable singleton with no did', () => {
+    const client = getUnauthenticatedThrowingClient()
+
+    expect(client.did).toBeUndefined()
+    /* identity is stable so it is safe in React Query keys */
+    expect(getUnauthenticatedThrowingClient()).toBe(client)
+  })
+
+  it('rejects any call with NotAuthenticatedError as the cause, with no fetch', async () => {
+    /*
+     * The throwing fetchHandler fires before any network I/O. lex-client wraps a
+     * fetchHandler throw in an internal error whose `cause` is the original, so
+     * the NotAuthenticatedError surfaces there.
+     */
+    const fetchMock = makeProfileFetch()
+    const err = await getUnauthenticatedThrowingClient()
+      .call(com.atproto.server.getSession, {})
+      .then(() => undefined)
+      .catch((e: unknown) => e)
+
+    expect((err as Error).cause).toBeInstanceOf(NotAuthenticatedError)
+    expect(((err as Error).cause as Error).name).toBe('NotAuthenticatedError')
+    expect(((err as Error).cause as Error).message).toBe(
+      'Not authenticated: this operation requires an active session',
+    )
+    expect(fetchMock).not.toHaveBeenCalled()
+  })
+})

src/state/session/__tests__/provider-clients-test.tsx

@@ -0,0 +1,193 @@
+import {type Client} from '@atproto/lex'
+import {PasswordSession} from '@atproto/lex-password-session'
+import {beforeEach, describe, expect, it, jest} from '@jest/globals'
+import {act, render} from '@testing-library/react-native'
+
+import {type SessionAccount} from '../types'
+
+/*
+ * The provider pulls the whole app shell in through `#/state/util` and the
+ * account factories. These mocks cut the tree back to the session lifecycle
+ * itself, mirroring provider-abort-test.tsx.
+ */
+jest.mock('#/state/persisted', () => {
+  const {
+    defaults,
+  }: typeof import('#/state/persisted/schema') = require('#/state/persisted/schema')
+  return {
+    defaults,
+    get: (key: keyof typeof defaults) => defaults[key],
+    write: () => Promise.resolve(),
+    readLatest: (key: keyof typeof defaults) => defaults[key],
+    onUpdate: () => () => {},
+  }
+})
+jest.mock('#/state/util', () => ({useCloseAllActiveElements: () => () => {}}))
+jest.mock('#/components/dialogs/Context', () => ({
+  useGlobalDialogsControlContext: () => ({signinDialogControl: {open() {}}}),
+}))
+jest.mock('#/analytics', () => ({
+  AnalyticsContext: ({children}: {children: React.ReactNode}) => children,
+  useAnalyticsBase: () => ({metric() {}, logger: {debug() {}, error() {}}}),
+  utils: {accountToSessionMetadata: () => ({}), useMeta: () => undefined},
+}))
+jest.mock('#/state/shell/onboarding', () => ({
+  useOnboardingDispatch: () => () => {},
+}))
+jest.mock('#/ageAssurance/data', () => ({
+  clearAgeAssuranceServerDataForAll: () => {},
+  clearAgeAssuranceServerDataForDid: () => {},
+}))
+jest.mock('#/lib/persisted-query-storage', () => ({
+  clearPersistedQueryStorage: () => Promise.resolve(),
+}))
+jest.mock('#/lib/notifications/notifications', () => ({
+  unregisterPushToken: () => Promise.resolve(),
+}))
+jest.mock('jwt-decode', () => ({
+  jwtDecode: () => ({scope: 'com.atproto.access'}),
+}))
+jest.mock('#/state/events', () => ({
+  emitSessionDropped: () => {},
+  emitNetworkConfirmed: () => {},
+  emitNetworkLost: () => {},
+}))
+
+const mockLogin = jest.fn<(...args: unknown[]) => Promise<unknown>>()
+jest.mock('../session-core', () => ({
+  ...jest.requireActual<object>('../session-core'),
+  createSessionBundleAndLogin: (...args: unknown[]) => mockLogin(...args),
+}))
+jest.mock('../create-account', () => ({
+  createSessionBundleAndCreateAccount: () => new Promise(() => {}),
+}))
+
+import {
+  Provider,
+  useAppviewClient,
+  useChatClient,
+  useMaybeChatClient,
+  useMaybePdsClient,
+  usePdsClient,
+  useSessionApi,
+} from '#/state/session'
+import {type SessionApiContext} from '#/state/session/types'
+import {BskyAppAgent, PasswordSessionManager} from '../bridge-agent'
+import {
+  agentToAppviewClient,
+  agentToChatClient,
+  agentToPdsClient,
+  getUnauthenticatedThrowingClient,
+} from '../clients'
+import {type SessionBundle} from '../session-core'
+import {sessionAccountToSessionData} from '../session-data'
+import {asFetch, makeAccount, makeMockFetch} from './mock-fetch'
+
+type Clients = {
+  appview: Client
+  pds: Client
+  chat: Client
+  maybePds: Client | null
+  maybeChat: Client | null
+}
+
+/**
+ * Build a bundle whose agent is a real `BskyAppAgent` over a real
+ * `PasswordSession`, since the client builders derive from the agent. Only the
+ * fields the provider reads are populated.
+ */
+function makeBundle(account: SessionAccount): SessionBundle {
+  const fetchMock = makeMockFetch()
+  const session = new PasswordSession(sessionAccountToSessionData(account), {
+    fetch: asFetch(fetchMock),
+  })
+  const manager = new PasswordSessionManager(session, {
+    service: account.service,
+  })
+  manager.setFetch(asFetch(fetchMock))
+  return {
+    session,
+    agent: new BskyAppAgent(manager),
+    service: new URL(account.service),
+  }
+}
+
+/** Render the provider and hand back the client hooks' current values. */
+function renderClients(): {api: SessionApiContext; clients: () => Clients} {
+  let api!: SessionApiContext
+  let clients!: Clients
+  function Probe() {
+    api = useSessionApi()
+    clients = {
+      appview: useAppviewClient(),
+      pds: usePdsClient(),
+      chat: useChatClient(),
+      maybePds: useMaybePdsClient(),
+      maybeChat: useMaybeChatClient(),
+    }
+    return null
+  }
+  render(
+    <Provider>
+      <Probe />
+    </Provider>,
+  )
+  return {api, clients: () => clients}
+}
+
+beforeEach(() => {
+  mockLogin.mockReset()
+})
+
+describe('client hooks while logged out', () => {
+  it('serves the public agent for appview reads', () => {
+    const {clients} = renderClients()
+    expect(clients().appview).toBeDefined()
+    /* the logged-out bundle's agent IS the public agent, so no separate branch */
+    expect(clients().appview.did).toBeUndefined()
+  })
+
+  it('serves the throwing client for the write surfaces', () => {
+    const {clients} = renderClients()
+    const throwing = getUnauthenticatedThrowingClient()
+    expect(clients().pds).toBe(throwing)
+    expect(clients().chat).toBe(throwing)
+  })
+
+  it('serves null from the maybe variants', () => {
+    const {clients} = renderClients()
+    expect(clients().maybePds).toBeNull()
+    expect(clients().maybeChat).toBeNull()
+  })
+})
+
+describe('client hooks with a session', () => {
+  it('derives every surface from the session bundle agent', async () => {
+    const account = makeAccount()
+    const bundle = makeBundle(account)
+    const {api, clients} = renderClients()
+
+    mockLogin.mockResolvedValueOnce({bundle, account})
+    await act(async () => {
+      await api.login({} as never, 'LoginForm')
+    })
+
+    expect(clients().appview).toBe(agentToAppviewClient(bundle.agent))
+    expect(clients().pds).toBe(agentToPdsClient(bundle.agent))
+    expect(clients().chat).toBe(agentToChatClient(bundle.agent))
+  })
+
+  it('serves the same clients from the maybe variants', async () => {
+    const account = makeAccount()
+    const bundle = makeBundle(account)
+    const {api, clients} = renderClients()
+
+    mockLogin.mockResolvedValueOnce({bundle, account})
+    await act(async () => {
+      await api.login({} as never, 'LoginForm')
+    })
+
+    expect(clients().maybePds).toBe(clients().pds)
+    expect(clients().maybeChat).toBe(clients().chat)
+  })
+})

src/state/session/clients.ts

@@ -1,15 +1,15 @@
 import {type Client} from '@atproto/lex'
 
-import {PUBLIC_BSKY_SERVICE} from '#/lib/constants'
+import {CHAT_PROXY_SERVICE, PUBLIC_BSKY_SERVICE} from '#/lib/constants'
 import {createLexClient} from '#/lib/lexClient'
 import {type BskyAppAgent} from './bridge-agent'
 import {networkAwareFetch} from './network'
 
 /*
- * One client per agent, so that repeated reads for the same agent return the
+ * One client per agent, per surface, so that repeated reads for the same agent
- * same instance. Client identity is observable: a lex `Client` is passed to
+ * return the same instance. Client identity is observable: a lex `Client` is
- * React Query `queryFn`s and read from render paths, so a freshly allocated
+ * passed to React Query `queryFn`s and read from render paths, so a freshly
- * client on every read would break any dependency array or reference
+ * allocated client on every read would break any dependency array or reference
  * comparison built on top of it.
  *
  * Keying on the agent also ties client lifetime to agent lifetime. A disposed
@@ -17,10 +17,12 @@ import {networkAwareFetch} from './network'
  * rotation builds a new agent rather than mutating the old one, so a client
  * derived from a stale agent becomes unreachable exactly when its agent does.
  */
-const lexClients = new WeakMap<BskyAppAgent, Client>()
+const appviewClients = new WeakMap<BskyAppAgent, Client>()
+const pdsClients = new WeakMap<BskyAppAgent, Client>()
+const chatClients = new WeakMap<BskyAppAgent, Client>()
 
 /**
- * The lex {@link Client} for an agent, memoized per agent.
+ * The appview {@link Client} for an agent, memoized per agent.
  *
  * The wrapped handler is `agent.fetchHandler`, NOT
  * `agent.sessionManager.fetchHandler`. The agent-level handler is where
@@ -30,8 +32,8 @@ const lexClients = new WeakMap<BskyAppAgent, Client>()
  * deliberately built with neither a `service` option nor labelers - setting
  * either here would emit them a second time.
  */
-export function agentToLexClient(agent: BskyAppAgent): Client {
+export function agentToAppviewClient(agent: BskyAppAgent): Client {
-  const existing = lexClients.get(agent)
+  const existing = appviewClients.get(agent)
   if (existing) {
     return existing
   }
@@ -41,10 +43,101 @@ export function agentToLexClient(agent: BskyAppAgent): Client {
     },
     fetchHandler: (path, init) => agent.fetchHandler(path, init),
   })
-  lexClients.set(agent, client)
+  appviewClients.set(agent, client)
   return client
 }
 
+/**
+ * The account-host {@link Client} for an agent, memoized per agent.
+ *
+ * This wraps `agent.sessionManager.fetchHandler`, one layer below
+ * {@link agentToAppviewClient}. That layer does authorization and refresh-on-401
+ * and resolves the request against `dispatchUrl` (the account's PDS), but it
+ * does NOT set `atproto-proxy` or `atproto-accept-labelers`, so requests reach
+ * the PDS itself rather than being proxied onward. That is the right transport
+ * for `com.atproto.*` repo/server/identity calls.
+ *
+ * No `service` option for the same reason: adding one would reintroduce the
+ * proxy header this client exists to avoid.
+ *
+ * The handler is wrapped in a closure rather than passed by reference because
+ * `PasswordSessionManager.fetchHandler` reads `this`. Relative paths are
+ * intentional: lex-client hands its handler an origin-less
+ * `/xrpc/<nsid>[?query]` path, which the session manager absolutizes against
+ * `dispatchUrl`.
+ */
+export function agentToPdsClient(agent: BskyAppAgent): Client {
+  const existing = pdsClients.get(agent)
+  if (existing) {
+    return existing
+  }
+  const client = createLexClient({
+    get did() {
+      return agent.did
+    },
+    fetchHandler: (path, init) => agent.sessionManager.fetchHandler(path, init),
+  })
+  pdsClients.set(agent, client)
+  return client
+}
+
+/**
+ * The chat {@link Client} for an agent, memoized per agent.
+ *
+ * Same session-manager transport as {@link agentToPdsClient} - authorization
+ * and PDS routing, no agent-level proxy or labeler headers - but constructed
+ * with {@link CHAT_PROXY_SERVICE} as its `service`, so lex-client emits
+ * `atproto-proxy: <CHAT_PROXY_SERVICE>` on every request and `chat.bsky.*`
+ * calls are proxied to the chat service.
+ */
+export function agentToChatClient(agent: BskyAppAgent): Client {
+  const existing = chatClients.get(agent)
+  if (existing) {
+    return existing
+  }
+  const client = createLexClient(
+    {
+      get did() {
+        return agent.did
+      },
+      fetchHandler: (path, init) =>
+        agent.sessionManager.fetchHandler(path, init),
+    },
+    {service: CHAT_PROXY_SERVICE},
+  )
+  chatClients.set(agent, client)
+  return client
+}
+
+/** Thrown when a write/auth-only client is used with no active session. */
+export class NotAuthenticatedError extends Error {
+  constructor(op = 'this operation') {
+    super(`Not authenticated: ${op} requires an active session`)
+    this.name = 'NotAuthenticatedError'
+  }
+}
+
+let unauthedClient: Client | undefined
+
+/**
+ * A {@link Client} that throws {@link NotAuthenticatedError} on any request,
+ * before any network I/O. It is the logged-out value of the write/auth-only
+ * hooks (`usePdsClient`/`useChatClient`) so an unauthenticated call fails
+ * immediately and legibly instead of silently hitting public infrastructure,
+ * which would answer with an opaque 4xx.
+ *
+ * A single module-level instance, so its identity is stable across renders -
+ * safe to use in React Query keys and as a hook return value.
+ */
+export function getUnauthenticatedThrowingClient(): Client {
+  return (unauthedClient ??= createLexClient({
+    did: undefined,
+    fetchHandler: () => {
+      throw new NotAuthenticatedError()
+    },
+  }))
+}
+
 let publicLexClient: Client | undefined
 
 /**
@@ -52,9 +145,10 @@ let publicLexClient: Client | undefined
  * appview.
  *
  * A single module-level instance for the same identity-stability reason as
- * {@link agentToLexClient}: there is no session to scope it to, so it lives for
+ * {@link agentToAppviewClient}: there is no session to scope it to, so it lives
- * the lifetime of the process. Requests go through {@link networkAwareFetch} so
+ * for the lifetime of the process. Requests go through
- * public reads feed the app's reachability signal like authenticated ones do.
+ * {@link networkAwareFetch} so public reads feed the app's reachability signal
+ * like authenticated ones do.
  *
  * Unlike the public agent it parallels, this client sends neither
  * `atproto-proxy` nor `atproto-accept-labelers`. `createPublicAgent` configures
@@ -63,7 +157,7 @@ let publicLexClient: Client | undefined
  * consumer that needs moderation labels on public reads must configure labelers
  * itself before issuing the request.
  */
-export function getPublicLexClient(): Client {
+export function getPublicAppviewClient(): Client {
   return (publicLexClient ??= createLexClient({
     service: PUBLIC_BSKY_SERVICE,
     fetch: networkAwareFetch,

src/state/session/index.tsx

@@ -19,7 +19,13 @@ import {useGlobalDialogsControlContext} from '#/components/dialogs/Context'
 import {AnalyticsContext, useAnalyticsBase, utils} from '#/analytics'
 import {IS_WEB} from '#/env'
 import {emitSessionDropped} from '../events'
-import {agentToLexClient, getPublicLexClient} from './clients'
+import {
+  agentToAppviewClient,
+  agentToChatClient,
+  agentToPdsClient,
+  getPublicAppviewClient,
+  getUnauthenticatedThrowingClient,
+} from './clients'
 import {createSessionBundleAndCreateAccount} from './create-account'
 import {pickExpiryRescueCandidate} from './expiry-rescue'
 import {type Action, getInitialState, reducer, type State} from './reducer'
@@ -711,20 +717,70 @@ export function useAgent(): AtpAgent {
 }
 
 /**
- * The lex client for the active session, or for the public agent when logged
+ * Client for appview reads.
- * out.
+ *
+ * When logged out the bundle's agent is the public agent built by
+ * `createPublicAgent`, which is configured with the appview proxy and dispatches
+ * unauthenticated, so the logged-out fallback is the agent itself - there is no
+ * separate public branch here.
  */
-export function useLexClient(): Client {
+export function useAppviewClient(): Client {
   const bundle = useContext(BundleContext)
   if (!bundle) {
-    throw Error('useLexClient() must be below <SessionProvider>.')
+    throw Error('useAppviewClient() must be below <SessionProvider>.')
   }
-  return agentToLexClient(bundle.agent)
+  return agentToAppviewClient(bundle.agent)
 }
 
 /**
- * The unauthenticated lex client for public reads.
+ * Client for account-host requests. It shares the active session's auth
+ * lifecycle but sets no proxy or labeler headers, so calls target the PDS.
+ * Logged out, calls throw `NotAuthenticatedError` before network I/O. Use
+ * {@link useMaybePdsClient} when the caller must branch on authentication.
  */
-export function usePublicLexClient(): Client {
+export function usePdsClient(): Client {
-  return getPublicLexClient()
+  const bundle = useContext(BundleContext)
+  if (!bundle) {
+    throw Error('usePdsClient() must be below <SessionProvider>.')
+  }
+  return bundle.session
+    ? agentToPdsClient(bundle.agent)
+    : getUnauthenticatedThrowingClient()
+}
+
+/**
+ * Client for `chat.bsky.*` calls. Logged-out calls throw
+ * `NotAuthenticatedError`; use {@link useMaybeChatClient} to branch on auth.
+ */
+export function useChatClient(): Client {
+  const bundle = useContext(BundleContext)
+  if (!bundle) {
+    throw Error('useChatClient() must be below <SessionProvider>.')
+  }
+  return bundle.session
+    ? agentToChatClient(bundle.agent)
+    : getUnauthenticatedThrowingClient()
+}
+
+/**
+ * Account-host client for the active session, or `null` when logged out.
+ */
+export function useMaybePdsClient(): Client | null {
+  const bundle = useContext(BundleContext)
+  return bundle?.session ? agentToPdsClient(bundle.agent) : null
+}
+
+/**
+ * Chat client for the active session, or `null` when logged out.
+ */
+export function useMaybeChatClient(): Client | null {
+  const bundle = useContext(BundleContext)
+  return bundle?.session ? agentToChatClient(bundle.agent) : null
+}
+
+/**
+ * The unauthenticated client for public appview reads.
+ */
+export function usePublicAppviewClient(): Client {
+  return getPublicAppviewClient()
 }