fix(codex): retain exact cancellable prompt turn ids

src/main/codex/codex-prompt-registry-bounds.ts

@@ -2,6 +2,7 @@ import {
   boundPayload,
   digestPayload
 } from '../native-chat/agent-session-journal/journal-payload-bounds'
+import { AGENT_SESSION_ID_MAX_LENGTH } from '../../shared/agent-session-wire'
 
 export const CODEX_JOURNAL_PROMPT_ID_COMPONENT_MAX_BYTES = 256
 export const CODEX_JOURNAL_PROMPT_OPTION_ID_MAX_BYTES = 1024
@@ -13,7 +14,7 @@ export const CODEX_PROMPT_MAX_ANSWER_BYTES = 64 * 1024
 export const MAX_CODEX_PROMPT_REGISTRY_ENTRIES = 128
 export const MAX_CODEX_PROMPT_JOURNAL_BINDINGS = 256
 export const MAX_CODEX_PROMPT_REGISTRY_BYTES = 4 * 1024 * 1024
-const CODEX_PROMPT_TURN_ID_RESERVED_BYTES = 512
+const CODEX_PROMPT_TURN_ID_RESERVED_BYTES = AGENT_SESSION_ID_MAX_LENGTH * 3
 
 type CodexPromptRegistryEntryBounds = {
   threadId: string
@@ -49,7 +50,7 @@ export function codexPromptTurnIdentity(turnId: string): {
   turnId: string | null
   turnIdDigest?: string
 } {
-  return Buffer.byteLength(turnId, 'utf8') <= CODEX_PROMPT_TURN_ID_RESERVED_BYTES
+  return turnId.length <= AGENT_SESSION_ID_MAX_LENGTH
     ? { turnId }
     : { turnId: null, turnIdDigest: digestPayload(turnId) }
 }

src/main/codex/codex-prompt-registry.ts

@@ -89,11 +89,15 @@ export class CodexPromptRegistry {
       return null
     }
     const turnId = readString(request.params, 'turnId')
+    const turnIdentity = turnId ? codexPromptTurnIdentity(turnId) : { turnId: null }
+    if (turnId && turnIdentity.turnId === null) {
+      return null
+    }
     const prompt: CodexPendingPrompt = {
       requestId: request.id,
       method: request.method,
       threadId,
-      ...(turnId ? codexPromptTurnIdentity(turnId) : { turnId: null }),
+      ...turnIdentity,
       codexItemId,
       promptKey: readString(request.params, 'approvalId') ?? codexItemId,
       questionIds,

src/main/codex/codex-structured-prompt-ownership.test.ts

@@ -1,5 +1,6 @@
 import { describe, expect, it, vi } from 'vitest'
 import { agentJournalItemKey } from '../../shared/agent-session-journal-item-key'
+import { AGENT_SESSION_ID_MAX_LENGTH } from '../../shared/agent-session-wire'
 import type {
   AgentJournalItemBody,
   AgentJournalItemIdentity
@@ -301,6 +302,30 @@ describe('Codex live prompt ownership', () => {
     expect(codex.connections[0]?.closed).toBe(false)
   })
 
+  it('keeps a wire-valid multibyte prompt turn id as the exact interrupt target', async () => {
+    const promptTurnId = '界'.repeat(171)
+    expect(promptTurnId.length).toBeLessThanOrEqual(AGENT_SESSION_ID_MAX_LENGTH)
+    expect(Buffer.byteLength(promptTurnId, 'utf8')).toBeGreaterThan(AGENT_SESSION_ID_MAX_LENGTH)
+    const codex = fakeCodex({
+      'turn/interrupt': () => completeTurn(codex, 'thread-child', promptTurnId)
+    })
+    const adapter = await acquired(codex)
+    registerPrompt(adapter, codex, 'child-prompt', 'thread-child', promptTurnId)
+
+    await expect(
+      adapter.cancelTurn({
+        sessionId: 'session-1',
+        turnId: 'root-turn',
+        fence: 7,
+        prompt: { itemId: 'child-prompt' }
+      })
+    ).resolves.toEqual({ cancelled: true })
+    expect(codex.connections[0]?.calls.at(-1)).toEqual({
+      method: 'turn/interrupt',
+      params: { threadId: 'thread-child', turnId: promptTurnId }
+    })
+  })
+
   it('settles a grouped prompt and its running turn before reporting cancellation', async () => {
     const codex = fakeCodex({
       'turn/interrupt': () => {

src/main/codex/codex-structured-prompt-replies.test.ts

@@ -1,4 +1,5 @@
 import { describe, expect, it } from 'vitest'
+import { AGENT_SESSION_ID_MAX_LENGTH } from '../../shared/agent-session-wire'
 import {
   applyCodexPromptAnswer,
   CodexPromptRegistry,
@@ -122,7 +123,7 @@ describe('CodexPromptRegistry', () => {
     expect(registry.find('other-thread-item')?.requestId).toBe(3)
   })
 
-  it('bounds an oversized backfilled turn id and still clears its prompt', () => {
+  it('retains a bounded cleanup identity for an unaddressable backfilled turn id', () => {
     const registry = new CodexPromptRegistry()
     const turnId = 'turn-'.padEnd(MAX_CODEX_PROMPT_REGISTRY_BYTES + 1, 'x')
     registry.register({
@@ -138,20 +139,34 @@ describe('CodexPromptRegistry', () => {
     expect(registry.find('journal-root')).toBeNull()
   })
 
-  it('bounds an oversized request turn id and still clears its prompt', () => {
+  it('reserves enough bytes for a wire-valid multibyte backfilled turn id', () => {
     const registry = new CodexPromptRegistry()
-    const turnId = 'turn-'.padEnd(MAX_CODEX_PROMPT_REGISTRY_BYTES + 1, 'x')
+    registry.register({
+      id: 1,
+      method: 'item/commandExecution/requestApproval',
+      params: { itemId: 'root-item', threadId: 'thread-1' }
+    })
+    const reservedBytes = registry.bytes
+    const turnId = '界'.repeat(AGENT_SESSION_ID_MAX_LENGTH)
+
+    registry.bindJournalItemId('journal-root', 'thread-1', 'root-item', turnId)
+
+    expect(registry.find('journal-root')?.turnId).toBe(turnId)
+    expect(registry.bytes).toBe(reservedBytes)
+    expect(registry.bytes).toBeLessThanOrEqual(MAX_CODEX_PROMPT_REGISTRY_BYTES)
+  })
+
+  it('rejects a request turn id beyond the wire identity bound', () => {
+    const registry = new CodexPromptRegistry()
+    const turnId = 'x'.repeat(AGENT_SESSION_ID_MAX_LENGTH + 1)
     const prompt = registry.register({
       id: 1,
       method: 'item/commandExecution/requestApproval',
       params: { itemId: 'root-item', threadId: 'thread-1', turnId }
     })
 
-    expect(prompt).not.toBeNull()
-    expect(registry.bytes).toBeLessThanOrEqual(MAX_CODEX_PROMPT_REGISTRY_BYTES)
-    registry.bindJournalItemId('journal-root', 'thread-1', 'root-item')
-    registry.clearTurn('thread-1', turnId)
-    expect(registry.find('journal-root')).toBeNull()
+    expect(prompt).toBeNull()
+    expect(registry.bytes).toBe(0)
   })
 
   it('addresses a prompt by its journal item id once bound, and forgets both', () => {

src/shared/agent-session-wire.ts

@@ -75,6 +75,8 @@ export type AgentSessionTurnActivity = {
   text: string
 }
 
+export const AGENT_SESSION_ID_MAX_LENGTH = 512
+
 /** Backward paging is the client's normal read; 40 matches the page size the
  *  mobile list renders without a visible fill-in. */
 export const AGENT_SESSION_HISTORY_DEFAULT_LIMIT = 40

src/shared/rpc-contract/structured-agent-session-params.ts

@@ -2,11 +2,12 @@ import { z } from 'zod'
 import { isAgentSessionId } from '../agent-session-record'
 import { normalizeExecutionHostId } from '../execution-host'
 import {
+  AGENT_SESSION_ID_MAX_LENGTH,
   AGENT_SESSION_HISTORY_DIRECTIONS,
   AGENT_SESSION_HISTORY_MAX_LIMIT
 } from '../agent-session-wire'
 
-export const MAX_ID_LENGTH = 512
+export const MAX_ID_LENGTH = AGENT_SESSION_ID_MAX_LENGTH
 
 // Four Claude questions with all four generated choices occupy 610 chars when fully percent-encoded.
 export const MAX_RESPONSE_OPTION_ID_LENGTH = 1024