diff --git a/mobile/src/components/NewWorktreeModal.tsx b/mobile/src/components/NewWorktreeModal.tsx
index 09a0914d4aa..ebbfc168e0d 100644
--- a/mobile/src/components/NewWorktreeModal.tsx
+++ b/mobile/src/components/NewWorktreeModal.tsx
@@ -51,6 +51,7 @@ import {
 import { createBlankWorkspace } from '../tasks/blank-workspace-create'
 import { createWorkspaceFromComposerSource } from '../tasks/source-workspace-create'
 import { MOBILE_TASKS_CAPABILITY } from '../tasks/mobile-tasks-capability'
+import { MOBILE_WORKTREE_CREATE_IDEMPOTENCY_CAPABILITY } from '../tasks/worktree-create-capability'
 import { normalizeWorkspaceAgent } from '../tasks/workspace-agent-selection'
 import {
   filterAvailableTaskProviders,
@@ -211,6 +212,7 @@ function NewWorktreeModalContent({
   const [note, setNote] = useState('')
   const [availableProviders, setAvailableProviders] = useState<TaskProvider[]>([])
   const [tasksSupported, setTasksSupported] = useState(false)
+  const [idempotentWorktreeCreateSupported, setIdempotentWorktreeCreateSupported] = useState(false)
   const [showAdvanced, setShowAdvanced] = useState(false)
   const [setupHookDetails, setSetupHookDetails] = useState<SetupHookDetails | null>(null)
   const [trustedOrcaHooks, setTrustedOrcaHooks] = useState<PersistedTrustedOrcaHooks>({})
@@ -417,6 +419,9 @@ function NewWorktreeModalContent({
       const capabilities =
         (statusResult?.result as { capabilities?: string[] } | undefined)?.capabilities ?? []
       setTasksSupported(capabilities.includes(MOBILE_TASKS_CAPABILITY))
+      setIdempotentWorktreeCreateSupported(
+        capabilities.includes(MOBILE_WORKTREE_CREATE_IDEMPOTENCY_CAPABILITY)
+      )
       const glabInstalled =
         (okResult(preflightRes)?.result as { glab?: { installed?: boolean } } | undefined)?.glab
           ?.installed === true
@@ -698,7 +703,8 @@ function NewWorktreeModalContent({
             },
             workspaceName: trimmedName || undefined,
             note: trimmedNote,
-            nameIsAutoManaged: composer.isNameAutoManaged
+            nameIsAutoManaged: composer.isNameAutoManaged,
+            supportsIdempotentCutoverRetry: idempotentWorktreeCreateSupported
           })
         : await createBlankWorkspace({
             client,
@@ -707,7 +713,8 @@ function NewWorktreeModalContent({
             startupCommand: command,
             createdWithAgentId,
             comment: trimmedNote,
-            setupDecision
+            setupDecision,
+            supportsIdempotentCutoverRetry: idempotentWorktreeCreateSupported
           })
       if ('error' in result) {
         setError(result.error)
diff --git a/mobile/src/tasks/blank-workspace-create.test.ts b/mobile/src/tasks/blank-workspace-create.test.ts
index 1fe37dba473..ba0fc4f1066 100644
--- a/mobile/src/tasks/blank-workspace-create.test.ts
+++ b/mobile/src/tasks/blank-workspace-create.test.ts
@@ -34,7 +34,8 @@ describe('createBlankWorkspace', () => {
       startupCommand: undefined,
       createdWithAgentId: undefined,
       comment: undefined,
-      setupDecision: 'inherit'
+      setupDecision: 'inherit',
+      supportsIdempotentCutoverRetry: true
     })
 
     expect(result).toEqual({ worktreeId: 'wt-1', name: 'octopus' })
@@ -67,7 +68,8 @@ describe('createBlankWorkspace', () => {
       startupCommand: 'claude',
       createdWithAgentId: 'claude',
       comment: 'spike',
-      setupDecision: 'run'
+      setupDecision: 'run',
+      supportsIdempotentCutoverRetry: true
     })
 
     expect(calls[0]?.params).toMatchObject({
@@ -96,7 +98,8 @@ describe('createBlankWorkspace', () => {
       startupCommand: undefined,
       createdWithAgentId: undefined,
       comment: undefined,
-      setupDecision: 'inherit'
+      setupDecision: 'inherit',
+      supportsIdempotentCutoverRetry: true
     })
 
     expect(result).toEqual({ worktreeId: 'wt-3', name: 'octopus-2' })
@@ -121,7 +124,8 @@ describe('createBlankWorkspace', () => {
       startupCommand: undefined,
       createdWithAgentId: undefined,
       comment: undefined,
-      setupDecision: 'inherit'
+      setupDecision: 'inherit',
+      supportsIdempotentCutoverRetry: true
     })
 
     expect(result).toEqual({ worktreeId: 'wt-4', name: 'octopus-2' })
@@ -139,7 +143,8 @@ describe('createBlankWorkspace', () => {
       startupCommand: undefined,
       createdWithAgentId: undefined,
       comment: undefined,
-      setupDecision: 'skip'
+      setupDecision: 'skip',
+      supportsIdempotentCutoverRetry: true
     })
 
     expect(result).toEqual({ error: 'SSH connection is not available' })
diff --git a/mobile/src/tasks/blank-workspace-create.ts b/mobile/src/tasks/blank-workspace-create.ts
index 014af558198..be21be54378 100644
--- a/mobile/src/tasks/blank-workspace-create.ts
+++ b/mobile/src/tasks/blank-workspace-create.ts
@@ -14,10 +14,12 @@ export async function createBlankWorkspace(args: {
   createdWithAgentId: TuiAgent | undefined
   comment: string | undefined
   setupDecision: WorkspaceCreateSetupDecision
+  supportsIdempotentCutoverRetry: boolean
 }): Promise<WorktreeCreateResult> {
   return createWorktreeWithNameRetry({
     client: args.client,
     baseName: args.baseName,
+    supportsIdempotentCutoverRetry: args.supportsIdempotentCutoverRetry,
     buildParams: (name) => {
       const params: Record<string, unknown> = {
         repo: `id:${args.repoId}`,
diff --git a/mobile/src/tasks/source-workspace-create.test.ts b/mobile/src/tasks/source-workspace-create.test.ts
index d23e0c66317..592375a7735 100644
--- a/mobile/src/tasks/source-workspace-create.test.ts
+++ b/mobile/src/tasks/source-workspace-create.test.ts
@@ -30,7 +30,8 @@ const baseArgs = {
   setupDecision: 'inherit' as const,
   agent,
   workspaceName: undefined,
-  note: undefined
+  note: undefined,
+  supportsIdempotentCutoverRetry: true
 }
 
 describe('createWorkspaceFromComposerSource', () => {
diff --git a/mobile/src/tasks/source-workspace-create.ts b/mobile/src/tasks/source-workspace-create.ts
index d16cc174142..2c6055dd3b2 100644
--- a/mobile/src/tasks/source-workspace-create.ts
+++ b/mobile/src/tasks/source-workspace-create.ts
@@ -30,6 +30,7 @@ export type CreateWorkspaceFromComposerArgs = {
   workspaceName: string | undefined
   note: string | undefined
   nameIsAutoManaged?: boolean
+  supportsIdempotentCutoverRetry: boolean
 }
 
 export async function createWorkspaceFromComposerSource(
@@ -92,6 +93,7 @@ async function createWorkItemWorkspace(args: {
   workspaceName: string | undefined
   note: string | undefined
   nameIsAutoManaged?: boolean
+  supportsIdempotentCutoverRetry: boolean
 }): Promise<WorktreeCreateResult> {
   const { client, selection, targetRepoId, setupDecision, agent, workspaceName, note } = args
   const item = selection.item
@@ -136,6 +138,7 @@ async function createWorkItemWorkspace(args: {
   return createWorktreeWithNameRetry({
     client,
     baseName,
+    supportsIdempotentCutoverRetry: args.supportsIdempotentCutoverRetry,
     buildParams: (name) => ({ ...params, name })
   })
 }
@@ -148,6 +151,7 @@ async function createBranchWorkspace(args: {
   agent: WorkspaceCreateAgentBundle
   workspaceName: string | undefined
   note: string | undefined
+  supportsIdempotentCutoverRetry: boolean
 }): Promise<WorktreeCreateResult> {
   const { client, selection, targetRepoId, setupDecision, agent, workspaceName, note } = args
   const createdWithAgentId = agent.choice === 'blank' ? undefined : agent.choice
@@ -173,6 +177,7 @@ async function createBranchWorkspace(args: {
     return createWorktreeWithNameRetry({
       client,
       baseName,
+      supportsIdempotentCutoverRetry: args.supportsIdempotentCutoverRetry,
       maxAttempts: 1,
       buildParams: (name) =>
         applyCommon({
@@ -195,6 +200,7 @@ async function createBranchWorkspace(args: {
   return createWorktreeWithNameRetry({
     client,
     baseName,
+    supportsIdempotentCutoverRetry: args.supportsIdempotentCutoverRetry,
     buildParams: (candidate) => {
       const params: Record<string, unknown> = {
         repo: `id:${targetRepoId}`,
@@ -219,6 +225,7 @@ async function createNewBranchWorkspace(args: {
   agent: WorkspaceCreateAgentBundle
   workspaceName: string | undefined
   note: string | undefined
+  supportsIdempotentCutoverRetry: boolean
 }): Promise<WorktreeCreateResult> {
   const { client, selection, targetRepoId, setupDecision, agent, note } = args
   const createdWithAgentId = agent.choice === 'blank' ? undefined : agent.choice
@@ -230,6 +237,7 @@ async function createNewBranchWorkspace(args: {
   return createWorktreeWithNameRetry({
     client,
     baseName: selection.branchName,
+    supportsIdempotentCutoverRetry: args.supportsIdempotentCutoverRetry,
     buildParams: (candidate) => {
       const params: Record<string, unknown> = {
         repo: `id:${targetRepoId}`,
diff --git a/mobile/src/tasks/worktree-create-capability.ts b/mobile/src/tasks/worktree-create-capability.ts
new file mode 100644
index 00000000000..36321885c28
--- /dev/null
+++ b/mobile/src/tasks/worktree-create-capability.ts
@@ -0,0 +1,4 @@
+// Why: older hosts strip worktree.create's clientMutationId, so mobile must not
+// replay an ambiguous create unless the host advertises idempotency support.
+// Mirrors WORKTREE_CREATE_IDEMPOTENCY_RUNTIME_CAPABILITY in the shared protocol.
+export const MOBILE_WORKTREE_CREATE_IDEMPOTENCY_CAPABILITY = 'worktree.create-idempotency.v1'
diff --git a/mobile/src/tasks/worktree-create-retry.test.ts b/mobile/src/tasks/worktree-create-retry.test.ts
index 6c5328cefda..5a7d39ffb1e 100644
--- a/mobile/src/tasks/worktree-create-retry.test.ts
+++ b/mobile/src/tasks/worktree-create-retry.test.ts
@@ -39,8 +39,6 @@ function scriptedClient(
   } as unknown as RpcClient
 }
 
-const noSleep = async (): Promise<void> => {}
-
 describe('createWorktreeWithNameRetry', () => {
   it('stamps a clientMutationId on the create request', async () => {
     const attempts: Attempt[] = []
@@ -49,8 +47,8 @@ describe('createWorktreeWithNameRetry', () => {
       client,
       baseName: 'otter',
       buildParams: (name) => ({ repo: 'id:r', name }),
-      mintMutationId: () => 'key-1',
-      sleep: noSleep
+      supportsIdempotentCutoverRetry: true,
+      mintMutationId: () => 'key-1'
     })
     expect(result).toEqual({ worktreeId: 'wt-1', name: 'otter' })
     expect(attempts).toHaveLength(1)
@@ -67,8 +65,8 @@ describe('createWorktreeWithNameRetry', () => {
       client,
       baseName: 'seal',
       buildParams: (name) => ({ repo: 'id:r', name }),
-      mintMutationId: () => 'key-mig',
-      sleep: noSleep
+      supportsIdempotentCutoverRetry: true,
+      mintMutationId: () => 'key-mig'
     })
     expect(result).toEqual({ worktreeId: 'wt-2', name: 'seal' })
     expect(attempts).toHaveLength(2)
@@ -87,8 +85,8 @@ describe('createWorktreeWithNameRetry', () => {
         client,
         baseName: 'crab',
         buildParams: (name) => ({ repo: 'id:r', name }),
-        mintMutationId: () => 'key-x',
-        sleep: noSleep
+        supportsIdempotentCutoverRetry: true,
+        mintMutationId: () => 'key-x'
       })
     ).rejects.toBeInstanceOf(LogicalClientCutoverError)
     // Initial attempt + 5 retries.
@@ -103,8 +101,8 @@ describe('createWorktreeWithNameRetry', () => {
         client,
         baseName: 'eel',
         buildParams: (name) => ({ repo: 'id:r', name }),
-        mintMutationId: () => 'key-t',
-        sleep: noSleep
+        supportsIdempotentCutoverRetry: true,
+        mintMutationId: () => 'key-t'
       })
     ).rejects.toThrow('Request timed out')
     expect(attempts).toHaveLength(1)
@@ -121,8 +119,8 @@ describe('createWorktreeWithNameRetry', () => {
       client,
       baseName: 'topic',
       buildParams: (name) => ({ repo: 'id:r', name }),
-      mintMutationId: () => `key-${(n += 1)}`,
-      sleep: noSleep
+      supportsIdempotentCutoverRetry: true,
+      mintMutationId: () => `key-${(n += 1)}`
     })
     expect(result).toEqual({ worktreeId: 'wt-3', name: 'topic-2' })
     expect(attempts).toHaveLength(2)
@@ -131,4 +129,20 @@ describe('createWorktreeWithNameRetry', () => {
     expect(attempts[1]!.params.clientMutationId).toBe('key-2')
     expect(attempts[1]!.params.name).toBe('topic-2')
   })
+
+  it('does not replay an ambiguous cutover when the host lacks idempotency support', async () => {
+    const attempts: Attempt[] = []
+    const client = scriptedClient([{ throws: new LogicalClientCutoverError() }], attempts)
+    await expect(
+      createWorktreeWithNameRetry({
+        client,
+        baseName: 'ray',
+        buildParams: (name) => ({ repo: 'id:r', name }),
+        supportsIdempotentCutoverRetry: false,
+        mintMutationId: () => 'must-not-be-used'
+      })
+    ).rejects.toBeInstanceOf(LogicalClientCutoverError)
+    expect(attempts).toHaveLength(1)
+    expect(attempts[0]!.params.clientMutationId).toBeUndefined()
+  })
 })
diff --git a/mobile/src/tasks/worktree-create-retry.ts b/mobile/src/tasks/worktree-create-retry.ts
index 0d605a9a8f3..d487fc09490 100644
--- a/mobile/src/tasks/worktree-create-retry.ts
+++ b/mobile/src/tasks/worktree-create-retry.ts
@@ -22,16 +22,15 @@ export type WorktreeCreateResult = { worktreeId: string; name: string } | { erro
 // instead of surfacing "RPC interrupted by connection migration" with the
 // worktree silently created.
 const WORKTREE_CREATE_CUTOVER_MAX_RETRIES = 5
-const WORKTREE_CREATE_CUTOVER_RETRY_DELAY_MS = 300
 
 export type CreateWorktreeWithNameRetryArgs = {
   client: RpcClient
   baseName: string
   buildParams: (name: string) => Record<string, unknown>
+  supportsIdempotentCutoverRetry: boolean
   maxAttempts?: number
   // Injected in tests; production mints a fresh idempotency key per candidate.
   mintMutationId?: () => string
-  sleep?: (ms: number) => Promise<void>
 }
 
 // Creates a worktree, retrying with a numeric suffix on a name-collision error.
@@ -42,18 +41,24 @@ export type CreateWorktreeWithNameRetryArgs = {
 export async function createWorktreeWithNameRetry(
   args: CreateWorktreeWithNameRetryArgs
 ): Promise<WorktreeCreateResult> {
-  const { client, baseName, buildParams } = args
+  const { client, baseName, buildParams, supportsIdempotentCutoverRetry } = args
   const maxAttempts = args.maxAttempts ?? CLIENT_WORKTREE_CREATE_MAX_ATTEMPTS
   const mintMutationId = args.mintMutationId ?? defaultWorktreeCreateMutationId
-  const sleep = args.sleep ?? defaultSleep
   let lastError: string | null = null
   for (let attempt = 0; attempt < maxAttempts; attempt += 1) {
     const candidateName = getClientWorktreeCreateCandidate(baseName, attempt)
-    // Why: one idempotency key per candidate name. A cutover retry reuses the
-    // SAME key so the host dedupes (no duplicate worktree), while a name-collision
-    // bump is a genuinely new create that must mint a fresh key.
-    const params = { ...buildParams(candidateName), clientMutationId: mintMutationId() }
-    const response = await sendWorktreeCreateResilient(client, params, sleep)
+    const candidateParams = buildParams(candidateName)
+    // Why: older hosts strip unknown fields, so only stamp and replay when the
+    // host advertises idempotency. One key per candidate makes cutover retries
+    // safe while a name-collision bump remains a genuinely new create.
+    const params = supportsIdempotentCutoverRetry
+      ? { ...candidateParams, clientMutationId: mintMutationId() }
+      : candidateParams
+    const response = await sendWorktreeCreateResilient(
+      client,
+      params,
+      supportsIdempotentCutoverRetry
+    )
     if (response.ok) {
       const result = (response as RpcSuccess).result as { worktree: { id: string } }
       return { worktreeId: result.worktree.id, name: candidateName }
@@ -71,7 +76,7 @@ export async function createWorktreeWithNameRetry(
 async function sendWorktreeCreateResilient(
   client: RpcClient,
   params: Record<string, unknown>,
-  sleep: (ms: number) => Promise<void>
+  supportsIdempotentCutoverRetry: boolean
 ): Promise<RpcResponse> {
   for (let migrationRetry = 0; ; migrationRetry += 1) {
     try {
@@ -80,13 +85,14 @@ async function sendWorktreeCreateResilient(
       })
     } catch (error) {
       if (
+        !supportsIdempotentCutoverRetry ||
         !isLogicalClientCutoverError(error) ||
         migrationRetry >= WORKTREE_CREATE_CUTOVER_MAX_RETRIES
       ) {
         throw error
       }
-      // Give migrateTo a beat to settle on the authenticated replacement session.
-      await sleep(WORKTREE_CREATE_CUTOVER_RETRY_DELAY_MS)
+      // Why: LogicalClientCutoverError is raised only after migrateTo installs an
+      // authenticated replacement, so retry immediately instead of adding UI lag.
     }
   }
 }
@@ -102,7 +108,3 @@ function defaultWorktreeCreateMutationId(): string {
   const randomPart = Math.random().toString(36).slice(2, 10)
   return `worktree-create:${Date.now().toString(36)}:${randomPart}`
 }
-
-function defaultSleep(ms: number): Promise<void> {
-  return new Promise((resolve) => setTimeout(resolve, ms))
-}
diff --git a/src/main/runtime/orca-runtime.test.ts b/src/main/runtime/orca-runtime.test.ts
index 4ecc79b1bc2..66ce78ca40b 100644
--- a/src/main/runtime/orca-runtime.test.ts
+++ b/src/main/runtime/orca-runtime.test.ts
@@ -1416,6 +1416,25 @@ describe('OrcaRuntimeService.dedupeWorktreeCreate', () => {
     expect(retried).toEqual(first)
   })
 
+  it('expires settled successes after the reconnect window', async () => {
+    vi.useFakeTimers()
+    try {
+      const runtime = new OrcaRuntimeService(store)
+      let calls = 0
+      const factory = (): Promise<{ n: number }> => Promise.resolve({ n: (calls += 1) })
+      await runtime.dedupeWorktreeCreate('id:r', 'key-1', factory)
+      await vi.advanceTimersByTimeAsync(59_999)
+      await runtime.dedupeWorktreeCreate('id:r', 'key-1', factory)
+      expect(calls).toBe(1)
+
+      await vi.advanceTimersByTimeAsync(1)
+      await runtime.dedupeWorktreeCreate('id:r', 'key-1', factory)
+      expect(calls).toBe(2)
+    } finally {
+      vi.useRealTimers()
+    }
+  })
+
   it('drops a failed create so a genuine retry starts fresh', async () => {
     const runtime = new OrcaRuntimeService(store)
     let calls = 0
@@ -1555,6 +1574,7 @@ describe('OrcaRuntimeService', () => {
     expect(status.capabilities).toContain('terminal.binary-stream.v1')
     expect(status.capabilities).toContain('workspace-ports.v1')
     expect(status.capabilities).toContain('mobile.tasks.v1')
+    expect(status.capabilities).toContain('worktree.create-idempotency.v1')
     expect(status.capabilities).toContain('project-host-setup.v1')
     expect(status.capabilities).toContain('linear.issue-attribute-filter.v1')
     expect(status.capabilities).not.toContain('browser.screencast.v1')
diff --git a/src/shared/protocol-version.ts b/src/shared/protocol-version.ts
index f6242c93e99..a1fc0ae817f 100644
--- a/src/shared/protocol-version.ts
+++ b/src/shared/protocol-version.ts
@@ -44,6 +44,10 @@ export const BROWSER_CERTIFICATE_TRUST_RUNTIME_CAPABILITY = 'browser.certificate
 // floor-taking input. Mobile must not forward replies unless advertised.
 export const TERMINAL_QUERY_REPLY_INPUT_RUNTIME_CAPABILITY =
   'terminal.query-reply-input.v1' as const
+// Why: older hosts strip worktree.create's clientMutationId, so mobile must only
+// replay ambiguous cutovers when the host advertises idempotent create support.
+export const WORKTREE_CREATE_IDEMPOTENCY_RUNTIME_CAPABILITY =
+  'worktree.create-idempotency.v1' as const
 
 export const RUNTIME_CAPABILITIES = [
   'runtime.status.compat.v1',
@@ -60,7 +64,8 @@ export const RUNTIME_CAPABILITIES = [
   FOLDER_WORKSPACE_PATH_STATUS_RUNTIME_CAPABILITY,
   LINEAR_ISSUE_ATTRIBUTE_FILTER_RUNTIME_CAPABILITY,
   AI_VAULT_RUNTIME_CAPABILITY,
-  TERMINAL_QUERY_REPLY_INPUT_RUNTIME_CAPABILITY
+  TERMINAL_QUERY_REPLY_INPUT_RUNTIME_CAPABILITY,
+  WORKTREE_CREATE_IDEMPOTENCY_RUNTIME_CAPABILITY
 ] as const
 
 export type RuntimeCapability = (typeof RUNTIME_CAPABILITIES)[number] | (string & {})