diff --git a/mobile/src/transport/rpc-incompatible-reply-error.ts b/mobile/src/transport/rpc-incompatible-reply-error.ts
index 026732ca3b5..dd42b42a814 100644
--- a/mobile/src/transport/rpc-incompatible-reply-error.ts
+++ b/mobile/src/transport/rpc-incompatible-reply-error.ts
@@ -1,6 +1,8 @@
 import type { RpcDecodeIssue } from './rpc-operation-contract'
 
-const INCOMPATIBLE_REPLY_MESSAGE_PREFIX = 'incompatible_reply: '
+/** The machine token. `message` is user-facing copy, so callers branch on this or on `name`. */
+export const RPC_INCOMPATIBLE_REPLY_CODE = 'incompatible_reply'
+const INCOMPATIBLE_REPLY_ERROR_NAME = 'RpcIncompatibleReplyError'
 
 // Why: a reply the operation's reader cannot read says nothing about what the host did.
 // On a mutation it is NOT evidence the mutation failed and authorizes no retry — only a
@@ -8,20 +10,24 @@ const INCOMPATIBLE_REPLY_MESSAGE_PREFIX = 'incompatible_reply: '
 // tasks/worktree-create-retry.ts). So this error is deliberately neither marked
 // delivery-unknown nor shaped like the cutover error the retry loops replay on.
 export class RpcIncompatibleReplyError extends Error {
+  readonly code = RPC_INCOMPATIBLE_REPLY_CODE
+
   constructor(
     readonly operationName: string,
     readonly method: string,
     readonly issues: readonly RpcDecodeIssue[]
   ) {
-    super(`${INCOMPATIBLE_REPLY_MESSAGE_PREFIX}${operationName} (${method})`)
+    // Why plain copy: this message reaches toasts and screen error text unchanged.
+    super(`The host sent a reply this app could not read (${method})`)
+    this.name = INCOMPATIBLE_REPLY_ERROR_NAME
   }
 }
 
-// Why: instanceof can miss across bundle copies, so also match by message, mirroring
-// isLogicalClientCutoverError.
+// Why: instanceof can miss across bundle copies, so also match the name a copy still carries,
+// mirroring isLogicalClientCutoverError.
 export function isRpcIncompatibleReplyError(error: unknown): boolean {
   return (
     error instanceof RpcIncompatibleReplyError ||
-    (error instanceof Error && error.message.startsWith(INCOMPATIBLE_REPLY_MESSAGE_PREFIX))
+    (error instanceof Error && error.name === INCOMPATIBLE_REPLY_ERROR_NAME)
   )
 }
diff --git a/mobile/src/transport/rpc-operation.test.ts b/mobile/src/transport/rpc-operation.test.ts
index 91542b48528..a05170cb2a8 100644
--- a/mobile/src/transport/rpc-operation.test.ts
+++ b/mobile/src/transport/rpc-operation.test.ts
@@ -7,6 +7,7 @@ import {
 } from './stable-logical-rpc-client'
 import { isRpcDeliveryUnknown, markRpcDeliveryUnknown } from './rpc-delivery-ambiguity'
 import {
+  RPC_INCOMPATIBLE_REPLY_CODE,
   RpcIncompatibleReplyError,
   isRpcIncompatibleReplyError
 } from './rpc-incompatible-reply-error'
@@ -320,6 +321,33 @@ describe('an incompatible reply', () => {
       runRpcOperation(connectedSession(incompatible), workspaceListOrNull, {})
     ).resolves.toBeNull()
   })
+
+  // `message` reaches toasts and screen copy, so the machine token lives on `code`/`name` instead.
+  it('carries readable copy in the message and the token on code and name', async () => {
+    const caught = await runRpcOperation(
+      connectedSession(incompatible),
+      workspaceListOrThrow,
+      {}
+    ).catch((thrown: unknown) => thrown)
+
+    expect((caught as Error).message).toBe(
+      'The host sent a reply this app could not read (worktree.ps)'
+    )
+    expect((caught as Error).message).not.toContain('incompatible_reply')
+    expect((caught as RpcIncompatibleReplyError).code).toBe(RPC_INCOMPATIBLE_REPLY_CODE)
+    expect((caught as Error).name).toBe('RpcIncompatibleReplyError')
+  })
+
+  // A second bundle copy of this module fails `instanceof`, so the name is the fallback.
+  it('recognizes a foreign copy of the error by name', () => {
+    const foreign = Object.assign(new Error('anything at all'), {
+      name: 'RpcIncompatibleReplyError'
+    })
+
+    expect(foreign instanceof RpcIncompatibleReplyError).toBe(false)
+    expect(isRpcIncompatibleReplyError(foreign)).toBe(true)
+    expect(isRpcIncompatibleReplyError(new Error('incompatible_reply: x (y)'))).toBe(false)
+  })
 })
 
 describe('a descriptor', () => {