diff --git a/mobile/src/components/HostProtocolGate.test.ts b/mobile/src/components/HostProtocolGate.test.ts
index 44a2265ccb3..2b5cf9a18ec 100644
--- a/mobile/src/components/HostProtocolGate.test.ts
+++ b/mobile/src/components/HostProtocolGate.test.ts
@@ -1,6 +1,7 @@
 import { createElement, useEffect } from 'react'
 import { act, create, type ReactTestRenderer } from 'react-test-renderer'
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
+import { createRpcClientTestDouble } from '../test/rpc-client-test-double'
 import type { RpcClient } from '../transport/rpc-client'
 import { HostProtocolGate, useHostProtocolGates } from './HostProtocolGate'
 
@@ -36,7 +37,9 @@ vi.mock('../transport/client-context', () => ({
 }))
 
 function clientWithStatus(result: Record<string, unknown>): RpcClient {
-  return { sendRequest: vi.fn().mockResolvedValue({ ok: true, result }) } as unknown as RpcClient
+  return createRpcClientTestDouble({
+    sendRequest: vi.fn().mockResolvedValue({ ok: true, result })
+  })
 }
 
 function GateConsumer() {
@@ -161,9 +164,9 @@ describe('HostProtocolGate', () => {
   })
 
   it('does not mount host routes before a connected host passes the compatibility probe', async () => {
-    const client = {
+    const client = createRpcClientTestDouble({
       sendRequest: vi.fn().mockReturnValue(new Promise(() => {}))
-    } as unknown as RpcClient
+    })
     hostClient.current = { client, state: 'connected' }
     renderer = await renderGate()
     const output = renderedText(renderer)
@@ -179,9 +182,9 @@ describe('HostProtocolGate', () => {
     expect(renderedText(renderer)).toContain('HostContent')
     expect(probeMounts.count).toBe(1)
 
-    const client = {
+    const client = createRpcClientTestDouble({
       sendRequest: vi.fn().mockReturnValue(new Promise(() => {}))
-    } as unknown as RpcClient
+    })
     await act(async () => {
       hostClient.current = { client, state: 'connected' }
       renderer?.update(gateElement())
@@ -220,7 +223,7 @@ describe('HostProtocolGate', () => {
   })
 
   it('keeps an already-validated host route mounted while reconnect status is pending', async () => {
-    const client = {
+    const client = createRpcClientTestDouble({
       sendRequest: vi
         .fn()
         .mockResolvedValueOnce({
@@ -228,7 +231,7 @@ describe('HostProtocolGate', () => {
           result: { protocolVersion: 5, minCompatibleMobileVersion: 0 }
         })
         .mockReturnValueOnce(new Promise(() => {}))
-    } as unknown as RpcClient
+    })
     hostClient.current = { client, state: 'connected' }
     renderer = await renderGate()
 
@@ -251,9 +254,9 @@ describe('HostProtocolGate', () => {
 
   it('fails open when a connected host cannot answer the status probe', async () => {
     hostClient.current = {
-      client: {
+      client: createRpcClientTestDouble({
         sendRequest: vi.fn().mockResolvedValue({ ok: false, error: { message: 'unavailable' } })
-      } as unknown as RpcClient,
+      }),
       state: 'connected'
     }
     renderer = await renderGate()
diff --git a/mobile/src/components/NewWorktreeModal.test.tsx b/mobile/src/components/NewWorktreeModal.test.tsx
index 0bbdb462d4c..c1c3c99fe6d 100644
--- a/mobile/src/components/NewWorktreeModal.test.tsx
+++ b/mobile/src/components/NewWorktreeModal.test.tsx
@@ -1,7 +1,8 @@
 import { createElement } from 'react'
 import { act, create, type ReactTestRenderer } from 'react-test-renderer'
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
-import type { RpcClient } from '../transport/rpc-client'
+import { createRpcClientTestDouble } from '../test/rpc-client-test-double'
+import type { RpcResponse } from '../transport/types'
 
 const asyncStorage = vi.hoisted(() => ({
   getItem: vi.fn().mockResolvedValue(null),
@@ -49,6 +50,10 @@ import { NewWorktreeModal } from './NewWorktreeModal'
 
 const LOCAL_HOST_LABEL = getLocalExecutionHostLabel('darwin')
 
+function rpcSuccess(result: unknown): RpcResponse {
+  return { id: '1', ok: true, result, _meta: { runtimeId: 'runtime-1' } }
+}
+
 const repos = [
   {
     id: 'repo-1',
@@ -100,11 +105,11 @@ describe('NewWorktreeModal project targets', () => {
         return Promise.reject(new Error('connection closed'))
       }
       if (method === 'status.get') {
-        return Promise.resolve({ ok: true, result: { hostPlatform: 'darwin' } })
+        return Promise.resolve(rpcSuccess({ hostPlatform: 'darwin' }))
       }
       return new Promise(() => {})
     })
-    const client = { sendRequest } as unknown as RpcClient
+    const client = createRpcClientTestDouble({ sendRequest })
 
     await act(async () => {
       renderer = create(
@@ -118,9 +123,7 @@ describe('NewWorktreeModal project targets', () => {
       )
       await Promise.resolve()
     })
-    await act(async () => {
-      await Promise.resolve()
-    })
+    await flushUpdates()
 
     expect(sendRequest).toHaveBeenCalledWith('repo.list')
     expect(pickerItems(renderer, 'Project')).toEqual([
@@ -143,17 +146,17 @@ describe('NewWorktreeModal project targets', () => {
         upstream: { owner: 'stablyai', repo: 'orca' }
       }
     ]
-    const client = {
+    const client = createRpcClientTestDouble({
       sendRequest: vi.fn().mockImplementation((method: string) => {
         if (method === 'repo.list') {
           return Promise.resolve({ ok: true, result: { repos: listedRepos } })
         }
         if (method === 'status.get') {
-          return Promise.resolve({ ok: true, result: { hostPlatform: 'darwin' } })
+          return Promise.resolve(rpcSuccess({ hostPlatform: 'darwin' }))
         }
         return new Promise(() => {})
       })
-    } as unknown as RpcClient
+    })
 
     await act(async () => {
       renderer = create(
@@ -167,6 +170,7 @@ describe('NewWorktreeModal project targets', () => {
       )
       await Promise.resolve()
     })
+    await flushUpdates()
 
     expect(pickerItems(renderer, 'Project')).toEqual([
       expect.objectContaining({ label: 'orca', detail: 'stablyai/orca' })
@@ -223,14 +227,14 @@ describe('NewWorktreeModal project targets', () => {
         return Promise.resolve({ ok: true, result: {} })
       }
       if (method === 'status.get') {
-        return Promise.resolve({ ok: true, result: { hostPlatform: 'linux' } })
+        return Promise.resolve(rpcSuccess({ hostPlatform: 'linux' }))
       }
       if (method === 'repo.hooks') {
         return Promise.resolve({ ok: true, result: { hooks: null, source: null } })
       }
       return Promise.resolve({ ok: true, result: {} })
     })
-    const client = { sendRequest } as unknown as RpcClient
+    const client = createRpcClientTestDouble({ sendRequest })
 
     await act(async () => {
       renderer = create(
@@ -279,14 +283,14 @@ describe('NewWorktreeModal project targets', () => {
         return Promise.resolve({ ok: true, result: {} })
       }
       if (method === 'status.get') {
-        return Promise.resolve({ ok: true, result: { hostPlatform: 'darwin' } })
+        return Promise.resolve(rpcSuccess({ hostPlatform: 'darwin' }))
       }
       if (method === 'repo.hooks') {
         return Promise.resolve({ ok: true, result: { hooks: null, source: null } })
       }
       return Promise.resolve({ ok: true, result: {} })
     })
-    const client = { sendRequest } as unknown as RpcClient
+    const client = createRpcClientTestDouble({ sendRequest })
 
     await act(async () => {
       renderer = create(
@@ -312,25 +316,25 @@ describe('NewWorktreeModal project targets', () => {
       resolveOldList = resolve
     })
     const freshRepo = { ...repos[0]!, id: 'repo-fresh', displayName: 'fresh' }
-    const oldClient = {
+    const oldClient = createRpcClientTestDouble({
       sendRequest: vi.fn().mockImplementation((method: string) => {
         if (method === 'repo.list') {
           return oldList
         }
         return new Promise(() => {})
       })
-    } as unknown as RpcClient
-    const freshClient = {
+    })
+    const freshClient = createRpcClientTestDouble({
       sendRequest: vi.fn().mockImplementation((method: string) => {
         if (method === 'repo.list') {
           return Promise.resolve({ ok: true, result: { repos: [freshRepo] } })
         }
         if (method === 'status.get') {
-          return Promise.resolve({ ok: true, result: { hostPlatform: 'darwin' } })
+          return Promise.resolve(rpcSuccess({ hostPlatform: 'darwin' }))
         }
         return new Promise(() => {})
       })
-    } as unknown as RpcClient
+    })
     const modalProps = {
       visible: true,
       hostId: 'host-1',
@@ -357,7 +361,7 @@ describe('NewWorktreeModal project targets', () => {
 
   it('remounts before the reopened session renders, so no stale instance sees visible', async () => {
     const sendRequest = vi.fn().mockImplementation(() => new Promise(() => {}))
-    const client = { sendRequest } as unknown as RpcClient
+    const client = createRpcClientTestDouble({ sendRequest })
     const modalProps = {
       client,
       hostId: 'host-1',
@@ -378,9 +382,9 @@ describe('NewWorktreeModal project targets', () => {
   })
 
   it('starts with fresh form state after closing and reopening', async () => {
-    const client = {
+    const client = createRpcClientTestDouble({
       sendRequest: vi.fn().mockImplementation(() => new Promise(() => {}))
-    } as unknown as RpcClient
+    })
     const modalProps = {
       client,
       hostId: 'host-1',
diff --git a/mobile/src/components/codex-reset-credit-capability.test.ts b/mobile/src/components/codex-reset-credit-capability.test.ts
index 7afaa7d7b80..46c6bf33219 100644
--- a/mobile/src/components/codex-reset-credit-capability.test.ts
+++ b/mobile/src/components/codex-reset-credit-capability.test.ts
@@ -1,6 +1,7 @@
 import { createElement } from 'react'
 import { act, create, type ReactTestRenderer } from 'react-test-renderer'
 import { afterEach, describe, expect, it, vi } from 'vitest'
+import { createRpcClientTestDouble } from '../test/rpc-client-test-double'
 import type { RpcClient } from '../transport/rpc-client'
 
 const probe = vi.hoisted(() => ({
@@ -58,7 +59,7 @@ describe('useCodexResetCreditCapability', () => {
         return cancel
       }
     )
-    const client = { sendRequest: vi.fn() } as unknown as RpcClient
+    const client = createRpcClientTestDouble({ sendRequest: vi.fn() })
     let renderer: ReactTestRenderer | null = null
 
     function Harness() {
diff --git a/mobile/src/home/mobile-home-connection-state.test.ts b/mobile/src/home/mobile-home-connection-state.test.ts
index 7e625034a0a..b577963f857 100644
--- a/mobile/src/home/mobile-home-connection-state.test.ts
+++ b/mobile/src/home/mobile-home-connection-state.test.ts
@@ -1,5 +1,5 @@
 import { describe, expect, it } from 'vitest'
-import type { RpcClient } from '../transport/rpc-client'
+import { createRpcClientTestDouble } from '../test/rpc-client-test-double'
 import type { HostCatalogEntry } from '../transport/types'
 import {
   reconcileMobileHomeHostStates,
@@ -22,7 +22,7 @@ function catalogHost(
 }
 
 function liveClient(hostId: string, state: MobileHomeClientEntry['state']): MobileHomeClientEntry {
-  return { hostId, state, client: {} as RpcClient }
+  return { hostId, state, client: createRpcClientTestDouble() }
 }
 
 describe('mobile home connection state', () => {
diff --git a/mobile/src/notifications/mobile-notifications.test.ts b/mobile/src/notifications/mobile-notifications.test.ts
index d85b1363005..d1ef0df8a2b 100644
--- a/mobile/src/notifications/mobile-notifications.test.ts
+++ b/mobile/src/notifications/mobile-notifications.test.ts
@@ -7,8 +7,8 @@ import {
   subscribeToDesktopNotifications
 } from './mobile-notifications'
 import AsyncStorage from '@react-native-async-storage/async-storage'
-import type { RpcClient } from '../transport/rpc-client'
 import { loadPushNotificationsEnabled } from '../storage/preferences'
+import { createRpcClientTestDouble } from '../test/rpc-client-test-double'
 import { resetHostNotificationSessionsForTests } from './notification-reconnect-catchup'
 
 vi.mock('expo-notifications', () => ({
@@ -93,11 +93,11 @@ describe('subscribeToDesktopNotifications', () => {
 
   it('drops the local stream when disposed before the desktop returns ready', () => {
     const unsubscribeStream = vi.fn()
-    const client = {
+    const client = createRpcClientTestDouble({
       subscribe: vi.fn(() => unsubscribeStream),
       getState: vi.fn(() => 'connected'),
       sendRequest: vi.fn()
-    } as unknown as RpcClient
+    })
 
     const unsubscribe = subscribeToDesktopNotifications(client, 'host-1')
     unsubscribe()
@@ -117,14 +117,14 @@ describe('subscribeToDesktopNotifications', () => {
       .mockResolvedValueOnce('scheduled-2')
     vi.mocked(Notifications.dismissNotificationAsync).mockResolvedValue(undefined)
     let onEvent: ((data: unknown) => void) | null = null
-    const client = {
+    const client = createRpcClientTestDouble({
       subscribe: vi.fn((_method, _params, callback: (data: unknown) => void) => {
         onEvent = callback
         return vi.fn()
       }),
       getState: vi.fn(() => 'connected'),
       sendRequest: vi.fn()
-    } as unknown as RpcClient
+    })
 
     subscribeToDesktopNotifications(client, 'host-1')
     onEvent?.({
@@ -173,14 +173,14 @@ describe('subscribeToDesktopNotifications', () => {
     } as never)
     vi.mocked(Notifications.scheduleNotificationAsync).mockResolvedValue('scheduled-1')
     let onEvent: ((data: unknown) => void) | null = null
-    const client = {
+    const client = createRpcClientTestDouble({
       subscribe: vi.fn((_method, _params, callback: (data: unknown) => void) => {
         onEvent = callback
         return vi.fn()
       }),
       getState: vi.fn(() => 'connected'),
       sendRequest: vi.fn()
-    } as unknown as RpcClient
+    })
 
     subscribeToDesktopNotifications(client, 'host-concurrent')
     onEvent?.({
@@ -217,14 +217,14 @@ describe('subscribeToDesktopNotifications', () => {
     )
     vi.mocked(Notifications.dismissNotificationAsync).mockResolvedValue(undefined)
     let onEvent: ((data: unknown) => void) | null = null
-    const client = {
+    const client = createRpcClientTestDouble({
       subscribe: vi.fn((_method, _params, callback: (data: unknown) => void) => {
         onEvent = callback
         return vi.fn()
       }),
       getState: vi.fn(() => 'connected'),
       sendRequest: vi.fn()
-    } as unknown as RpcClient
+    })
 
     subscribeToDesktopNotifications(client, 'host-dismiss-race')
     onEvent?.({
@@ -257,14 +257,14 @@ describe('subscribeToDesktopNotifications', () => {
       .mockResolvedValueOnce('scheduled-2')
     vi.mocked(Notifications.dismissNotificationAsync).mockResolvedValue(undefined)
     let onEvent: ((data: unknown) => void) | null = null
-    const client = {
+    const client = createRpcClientTestDouble({
       subscribe: vi.fn((_method, _params, callback: (data: unknown) => void) => {
         onEvent = callback
         return vi.fn()
       }),
       getState: vi.fn(() => 'connected'),
       sendRequest: vi.fn()
-    } as unknown as RpcClient
+    })
 
     subscribeToDesktopNotifications(client, 'host-dismiss-failed-replacement')
     onEvent?.({
@@ -304,14 +304,14 @@ describe('subscribeToDesktopNotifications', () => {
   it('treats unknown dismiss events as no-ops', async () => {
     vi.mocked(Notifications.dismissNotificationAsync).mockResolvedValue(undefined)
     let onEvent: ((data: unknown) => void) | null = null
-    const client = {
+    const client = createRpcClientTestDouble({
       subscribe: vi.fn((_method, _params, callback: (data: unknown) => void) => {
         onEvent = callback
         return vi.fn()
       }),
       getState: vi.fn(() => 'connected'),
       sendRequest: vi.fn()
-    } as unknown as RpcClient
+    })
 
     subscribeToDesktopNotifications(client, 'host-unknown')
     onEvent?.({ type: 'dismiss', notificationId: 'agent:missing' })
@@ -335,14 +335,14 @@ describe('subscribeToDesktopNotifications', () => {
         .mockResolvedValueOnce('scheduled-new')
       vi.mocked(Notifications.dismissNotificationAsync).mockResolvedValue(undefined)
       let onEvent: ((data: unknown) => void) | null = null
-      const client = {
+      const client = createRpcClientTestDouble({
         subscribe: vi.fn((_method, _params, callback: (data: unknown) => void) => {
           onEvent = callback
           return vi.fn()
         }),
         getState: vi.fn(() => 'connected'),
         sendRequest: vi.fn()
-      } as unknown as RpcClient
+      })
 
       subscribeToDesktopNotifications(client, 'host-1')
       onEvent?.({ type: 'notification', title: 't', body: 'b', notificationId: 'agent:old' })
@@ -386,7 +386,7 @@ describe('subscribeToDesktopNotifications — reconnect catch-up', () => {
   function makeClient() {
     let onData: ((data: unknown) => void) | null = null
     const sentRequests: { method: string; params: unknown }[] = []
-    const client = {
+    const client = createRpcClientTestDouble({
       subscribe: vi.fn((_method: string, _params: unknown, cb: (data: unknown) => void) => {
         onData = cb
         return vi.fn()
@@ -399,12 +399,12 @@ describe('subscribeToDesktopNotifications — reconnect catch-up', () => {
             result: method === 'notifications.getMissedSince' ? { notifications: [] } : undefined
           }) as never
       )
-    }
+    })
     // Why: onData is captured live via a getter (not destructured) because the
     // subscribe mock assigns it asynchronously as a side effect of
     // subscribeToDesktopNotifications calling client.subscribe.
     return {
-      client: client as unknown as RpcClient,
+      client,
       get onData() {
         return onData
       },
diff --git a/mobile/src/tasks/worktree-create-capability.test.ts b/mobile/src/tasks/worktree-create-capability.test.ts
index cad108e29d7..40925dabbdc 100644
--- a/mobile/src/tasks/worktree-create-capability.test.ts
+++ b/mobile/src/tasks/worktree-create-capability.test.ts
@@ -1,4 +1,5 @@
 import { describe, expect, it } from 'vitest'
+import { createRpcClientTestDouble } from '../test/rpc-client-test-double'
 import type { RpcClient } from '../transport/rpc-client'
 import { LogicalClientCutoverError } from '../transport/stable-logical-rpc-client'
 import { readNewWorktreeRuntimeCapabilities } from './worktree-create-capability'
@@ -18,7 +19,7 @@ type StatusOutcome =
 
 function statusClient(outcomes: StatusOutcome[]): RpcClient {
   let call = 0
-  return {
+  return createRpcClientTestDouble({
     sendRequest: async () => {
       const outcome = outcomes[Math.min(call, outcomes.length - 1)]!
       call += 1
@@ -38,7 +39,7 @@ function statusClient(outcomes: StatusOutcome[]): RpcClient {
         _meta: { runtimeId: 'r' }
       }
     }
-  } as unknown as RpcClient
+  })
 }
 
 describe('readNewWorktreeRuntimeCapabilities', () => {
diff --git a/mobile/src/tasks/worktree-create-retry.test.ts b/mobile/src/tasks/worktree-create-retry.test.ts
index b4463207ebe..c16bbfb609b 100644
--- a/mobile/src/tasks/worktree-create-retry.test.ts
+++ b/mobile/src/tasks/worktree-create-retry.test.ts
@@ -1,4 +1,5 @@
 import { describe, expect, it, vi } from 'vitest'
+import { createRpcClientTestDouble } from '../test/rpc-client-test-double'
 import type { RpcClient } from '../transport/rpc-client'
 import { markRpcDeliveryUnknown } from '../transport/rpc-delivery-ambiguity'
 import { LogicalClientCutoverError } from '../transport/stable-logical-rpc-client'
@@ -70,7 +71,7 @@ function scriptedClient(
   lastInboundAt?: number | (() => number)
 ): RpcClient {
   let call = 0
-  return {
+  return createRpcClientTestDouble({
     getState: () => connection?.getState() ?? 'connected',
     getLastInboundAt: () =>
       (typeof lastInboundAt === 'function' ? lastInboundAt() : lastInboundAt) ?? null,
@@ -107,7 +108,7 @@ function scriptedClient(
         _meta: { runtimeId: 'r' }
       }
     }
-  } as unknown as RpcClient
+  })
 }
 
 describe('createWorktreeWithNameRetry', () => {
diff --git a/mobile/src/test/rpc-client-test-double.ts b/mobile/src/test/rpc-client-test-double.ts
new file mode 100644
index 00000000000..4507457e366
--- /dev/null
+++ b/mobile/src/test/rpc-client-test-double.ts
@@ -0,0 +1,19 @@
+import type { RpcClient } from '../transport/rpc-client'
+
+export function createRpcClientTestDouble(): RpcClient
+export function createRpcClientTestDouble<T extends Partial<RpcClient>>(overrides: T): RpcClient & T
+export function createRpcClientTestDouble(overrides: Partial<RpcClient> = {}): RpcClient {
+  const client: RpcClient = {
+    sendRequest: () => Promise.reject(new Error('Unconfigured RPC test request')),
+    subscribe: () => () => {},
+    updateTerminalSubscriptionViewport: () => {},
+    getState: () => 'connected',
+    getReconnectAttempt: () => 0,
+    getLastConnectedAt: () => null,
+    getLastInboundAt: () => null,
+    onStateChange: () => () => {},
+    notifyForeground: () => {},
+    close: () => {}
+  }
+  return Object.assign(client, overrides)
+}