fix(mobile): preserve grouped prompt response compatibility

mobile/src/session/use-mobile-structured-prompt-responses.test.tsx

@@ -0,0 +1,175 @@
+import { createElement, useRef } from 'react'
+import { act, create, type ReactTestRenderer } from 'react-test-renderer'
+import { afterEach, describe, expect, it, vi } from 'vitest'
+import type { AgentSessionPromptResult } from '../../../src/shared/agent-session-wire'
+import type { AgentJournalRenderItem } from '../../../src/shared/agent-session-journal-types'
+import {
+  EMPTY_STRUCTURED_AGENT_SESSION,
+  type StructuredAgentSessionState
+} from '../../../src/shared/structured-agent-session-reducer'
+import { projectStructuredQuestion } from './mobile-structured-agent-prompts'
+import type {
+  StructuredAgentSessionMutate,
+  StructuredAgentSessionMutationResult
+} from './mobile-structured-agent-session-rpc'
+import { groupedQuestionPromptKey } from './mobile-structured-grouped-question'
+import { useMobileStructuredPromptResponses } from './use-mobile-structured-prompt-responses'
+
+type PromptResponses = ReturnType<typeof useMobileStructuredPromptResponses>
+
+let currentHook: PromptResponses | null = null
+let renderer: ReactTestRenderer | null = null
+
+function groupedPrompt(itemId: string, revision: number): AgentJournalRenderItem {
+  return {
+    itemId,
+    revision,
+    sequence: 1,
+    observedAt: 1,
+    body: {
+      kind: 'question',
+      question: '2 grouped questions from Claude',
+      options: [],
+      questions: [
+        {
+          id: 'q1',
+          question: 'First?',
+          multiSelect: false,
+          options: [
+            { id: 'q1:choice-1', label: 'One' },
+            { id: 'q1:choice-2', label: 'Another one' }
+          ]
+        },
+        {
+          id: 'q2',
+          question: 'Second?',
+          multiSelect: false,
+          options: [
+            { id: 'q2:choice-1', label: 'Two' },
+            { id: 'q2:choice-2', label: 'Another two' }
+          ]
+        }
+      ],
+      resolution: { state: 'pending', selectedOptionId: null, resolvedBy: null, resolvedAt: null }
+    }
+  }
+}
+
+function sessionState(prompt: AgentJournalRenderItem): StructuredAgentSessionState {
+  return { ...EMPTY_STRUCTURED_AGENT_SESSION, status: 'ready', items: [prompt] }
+}
+
+function projectedResponse(prompt: AgentJournalRenderItem, draft: PromptResponses['groupedDraft']) {
+  const projected = projectStructuredQuestion(prompt, draft)
+  const response = projected?.optionTokens[0]
+  if (!response) {
+    throw new Error('Grouped question did not project an option response')
+  }
+  return response
+}
+
+function Probe(props: {
+  sessionKey: string
+  state: StructuredAgentSessionState
+  mutate: StructuredAgentSessionMutate
+}) {
+  const stateRef = useRef(props.state)
+  stateRef.current = props.state
+  currentHook = useMobileStructuredPromptResponses({
+    stateRef,
+    sessionKey: props.sessionKey,
+    mutate: props.mutate,
+    onSendError: vi.fn()
+  })
+  return null
+}
+
+function hook(): PromptResponses {
+  if (!currentHook) {
+    throw new Error('Hook probe is not mounted')
+  }
+  return currentHook
+}
+
+afterEach(() => {
+  act(() => renderer?.unmount())
+  currentHook = null
+  renderer = null
+})
+
+describe('useMobileStructuredPromptResponses', () => {
+  it.each([
+    ['another session', 'session-b', groupedPrompt('item-b', 1)],
+    ['a newer prompt revision', 'session-a', groupedPrompt('item-a', 2)]
+  ])(
+    'does not let a completed grouped response clear %s draft',
+    async (_, nextSession, nextPrompt) => {
+      const firstPrompt = groupedPrompt('item-a', 1)
+      let resolveMutation!: (
+        value: StructuredAgentSessionMutationResult<AgentSessionPromptResult>
+      ) => void
+      const pendingMutation = new Promise<
+        StructuredAgentSessionMutationResult<AgentSessionPromptResult>
+      >((resolve) => {
+        resolveMutation = resolve
+      })
+      const mutate = vi.fn(() => pendingMutation) as unknown as StructuredAgentSessionMutate
+
+      act(() => {
+        renderer = create(
+          createElement(Probe, {
+            sessionKey: 'session-a',
+            state: sessionState(firstPrompt),
+            mutate
+          })
+        )
+      })
+      await act(async () => {
+        await hook().respondQuestion(projectedResponse(firstPrompt, null))
+      })
+      let firstSubmission!: Promise<boolean>
+      act(() => {
+        firstSubmission = hook().respondQuestion(
+          projectedResponse(firstPrompt, hook().groupedDraft)
+        )
+      })
+
+      act(() => {
+        renderer?.update(
+          createElement(Probe, {
+            sessionKey: nextSession,
+            state: sessionState(nextPrompt),
+            mutate
+          })
+        )
+      })
+      await act(async () => {
+        await hook().respondQuestion(projectedResponse(nextPrompt, null))
+      })
+      expect(hook().groupedDraft?.answers).toHaveLength(1)
+
+      await act(async () => {
+        resolveMutation({
+          status: 'accepted',
+          value: {
+            itemId: firstPrompt.itemId,
+            revision: firstPrompt.revision,
+            resolution: {
+              state: 'resolved',
+              selectedOptionId: 'q2:choice-1',
+              resolvedBy: 'mobile',
+              resolvedAt: 2
+            }
+          },
+          sameFence: true
+        })
+        await firstSubmission
+      })
+
+      expect(hook().groupedDraft?.promptKey).toBe(
+        groupedQuestionPromptKey(nextPrompt.itemId, nextPrompt.revision)
+      )
+      expect(hook().groupedDraft?.answers).toHaveLength(1)
+    }
+  )
+})

mobile/src/session/use-mobile-structured-prompt-responses.ts

@@ -66,11 +66,12 @@ export function useMobileStructuredPromptResponses(args: {
     async (answer: string): Promise<boolean> => {
       const prompt = stateRef.current.items.find(pendingStructuredQuestion) ?? null
       if (prompt?.body.questions) {
+        const promptKey = groupedQuestionPromptKey(prompt.itemId, prompt.revision)
         const grouped = advanceGroupedQuestion({
           response: answer,
           questions: prompt.body.questions,
           draft: groupedDraft,
-          promptKey: groupedQuestionPromptKey(prompt.itemId, prompt.revision)
+          promptKey
         })
         if (!grouped) {
           return false
@@ -86,7 +87,11 @@ export function useMobileStructuredPromptResponses(args: {
         )
         if (result.status !== 'rejected') {
           // The group left the phone; a retry must start from the first question, not a stale tail.
-          setCollected(null)
+          setCollected((current) =>
+            current?.sessionKey === sessionKey && current.draft.promptKey === promptKey
+              ? null
+              : current
+          )
         }
         if (result.status === 'unknown') {
           onSendError('Answer unconfirmed — check chat before retrying')

src/main/runtime/rpc/methods/structured-agent-session-schemas.ts

@@ -12,6 +12,8 @@ import {
 import { normalizeExecutionHostId } from '../../../../shared/execution-host'
 
 const MAX_ID_LENGTH = 512
+// Four Claude questions with all four generated choices occupy 610 chars when fully percent-encoded.
+const MAX_RESPONSE_OPTION_ID_LENGTH = 1024
 const MAX_PROMPT_BYTES = 256 * 1024
 const MAX_BLOCKS = 64
 const MAX_OPTION_LABEL = 512
@@ -21,11 +23,11 @@ export const SessionId = z
   .max(MAX_ID_LENGTH)
   .refine(isAgentSessionId, 'Invalid agent session id')
 
-const Identifier = (message: string) =>
+const Identifier = (message: string, maxLength = MAX_ID_LENGTH) =>
   z
     .string()
     .min(1, message)
-    .max(MAX_ID_LENGTH, message)
+    .max(maxLength, message)
     .refine((value) => value === value.trim(), message)
 
 export const JournalCursor = z
@@ -166,7 +168,7 @@ export const RespondParams = z
     itemId: Identifier('Invalid item id'),
     /** Compare-and-set: the revision the client had on screen. */
     expectedRevision: z.number().int().positive(),
-    optionId: Identifier('Invalid option id')
+    optionId: Identifier('Invalid option id', MAX_RESPONSE_OPTION_ID_LENGTH)
   })
   .strict()
 

src/main/runtime/rpc/methods/structured-agent-session.test.ts

@@ -732,6 +732,41 @@ describe('parameter validation', () => {
     })
   })
 
+  it('accepts the maximum fully encoded Claude choice group and retains a finite bound', async () => {
+    const maximumSelections = Array.from({ length: 4 }, (_, questionIndex) => ({
+      questionId: `q${questionIndex + 1}`,
+      optionIds: Array.from(
+        { length: 4 },
+        (_, optionIndex) => `q${questionIndex + 1}:choice-${optionIndex + 1}`
+      )
+    }))
+    const optionId = `question-group:${encodeURIComponent(JSON.stringify(maximumSelections))}`
+    expect(optionId.length).toBe(610)
+
+    const response = await call(
+      'agentSession.respondToQuestion',
+      {
+        envelope: envelope(),
+        itemId: 'item-1',
+        expectedRevision: 1,
+        optionId
+      },
+      STRUCTURED_CLIENT
+    )
+    expect(response).toMatchObject({ ok: true })
+    expect(hostCalls.respondToPrompt).toHaveBeenCalledWith(
+      expect.anything(),
+      expect.objectContaining({ optionId })
+    )
+
+    await rejects('agentSession.respondToQuestion', {
+      envelope: envelope(),
+      itemId: 'item-1',
+      expectedRevision: 1,
+      optionId: 'x'.repeat(1025)
+    })
+  })
+
   it('bounds a history page and validates its cursor', async () => {
     await rejects('agentSession.history', {
       sessionId: SESSION,

src/shared/agent-session-question-answer.test.ts

@@ -6,6 +6,12 @@ import {
   type AgentSessionQuestionAnswer
 } from './agent-session-question-answer'
 
+const GROUP_ANSWER_PREFIX = 'question-group:'
+
+function decodeWithOriginalPercentDecoder(encoded: string): unknown {
+  return JSON.parse(decodeURIComponent(encoded.slice(GROUP_ANSWER_PREFIX.length)))
+}
+
 describe('agent-session grouped question answers', () => {
   const answers: AgentSessionQuestionAnswer[] = [
     { questionId: 'q1', optionIds: ['target-web', 'target-mobile'] },
@@ -18,6 +24,44 @@ describe('agent-session grouped question answers', () => {
     )
   })
 
+  it('keeps compact answers readable by the original percent-decoding contract', () => {
+    expect(decodeWithOriginalPercentDecoder(encodeAgentSessionQuestionAnswers(answers))).toEqual(
+      answers
+    )
+  })
+
+  it('accepts the previous fully percent-encoded representation', () => {
+    const encoded = `${GROUP_ANSWER_PREFIX}${encodeURIComponent(JSON.stringify(answers))}`
+
+    expect(decodeAgentSessionQuestionAnswers(encoded)).toEqual(answers)
+  })
+
+  it('round-trips percent signs and Unicode through the compact representation', () => {
+    const unicodeAnswers: AgentSessionQuestionAnswer[] = [
+      {
+        questionId: '進捗%',
+        optionIds: ['100%:完了', '🚀'],
+        other: 'café 東京 50%'
+      }
+    ]
+
+    expect(
+      decodeAgentSessionQuestionAnswers(encodeAgentSessionQuestionAnswers(unicodeAnswers))
+    ).toEqual(unicodeAnswers)
+  })
+
+  it("fits Claude's maximum choice group within a 512-character host response bound", () => {
+    const maximumSelections = Array.from({ length: 4 }, (_, questionIndex) => ({
+      questionId: `q${questionIndex + 1}`,
+      optionIds: Array.from(
+        { length: 4 },
+        (_, optionIndex) => `q${questionIndex + 1}:choice-${optionIndex + 1}`
+      )
+    }))
+
+    expect(encodeAgentSessionQuestionAnswers(maximumSelections).length).toBeLessThanOrEqual(512)
+  })
+
   it('validates each grouped answer against its question shape', () => {
     const questions = [
       {

src/shared/agent-session-question-answer.ts

@@ -11,7 +11,8 @@ export type AgentSessionQuestionAnswer = {
 export function encodeAgentSessionQuestionAnswers(
   answers: readonly AgentSessionQuestionAnswer[]
 ): string {
-  return `${GROUP_ANSWER_PREFIX}${encodeURIComponent(JSON.stringify(answers))}`
+  // RPC already JSON-frames this value; escaping `%` alone preserves decodeURIComponent readers.
+  return `${GROUP_ANSWER_PREFIX}${JSON.stringify(answers).replaceAll('%', '%25')}`
 }
 
 export function decodeAgentSessionQuestionAnswers(