Jyotisha/frontend/tests/rectification-dup-question-20260926.test.tsx

/**
 * 2026-09-26, staging, real device (TASK-rectification-dup-question-20260926):
 *
 * A (BUG-1045, recurrence of BUG-585 via BUG-969 ③): a typed answer to a
 *   pending choice (or a collect denial) streams 「ack + next stem」 as one
 *   `answer.delta`; the snapshot merge then hangs the same stem as a question
 *   block under it, so the stem showed twice until a refresh.
 * B (BUG-1046): a tapped option was marked answered locally before the POST;
 *   when the POST failed nothing rolled it back, so the latest message showed
 *   the answered card and the standalone `persisted_question` block drew the
 *   very same question a second time.
 *
 * These tests mount the real `RectificationAgenticChat` on the minimal host DOM
 * and drive the LIVE path through a fake `fetch`: stream → settle → snapshot
 * merge. They count what the reader would see, not helper return values.
 */
import assert from "node:assert/strict";
import test from "node:test";

import { RectificationAgenticChat } from "../src/components/rectification-agentic-chat.tsx";
import { persistCollectDenialTurn } from "../src/lib/rectification-agentic/v9/answer-choice.ts";
import { composeCollectSpokenAssistantText } from "../src/lib/rectification-agentic/v9/collect-prompt.ts";
import { attachQuestionsToTurns } from "../src/lib/rectification-agentic/v9/turn-question.ts";
import type { ConversationFocus } from "../src/lib/rectification-agentic/v9/tool-service.ts";
import { RECTIFICATION_USER_COPY } from "../src/lib/rectification-agentic/user-copy.ts";
import {
  RECTIFICATION_CHOICE_SUBMIT_FAILED_COPY,
} from "../src/lib/rectification-surface-state.ts";
import {
  appendUnseenAssistantTurns,
  mergeTurnQuestions,
  type SnapshotTurnMessage,
} from "../src/lib/rectification-snapshot-messages.ts";
import { createClientLifecycleHarness } from "./react-client-lifecycle-test-support.ts";
import { fakeAccounting, USER_ID } from "./rectification-v9-test-support.ts";

const CASE_ID = "44444444-4444-4444-8444-444444444444";
const SESSION_ID = "33333333-3333-4333-8333-333333333333";
const FOCUS_1 = "aaaaaaaa-aaaa-4aaa-8aaa-aaaaaaaaaaa1";
const FOCUS_2 = "aaaaaaaa-aaaa-4aaa-8aaa-aaaaaaaaaaa2";
const STEM_1 = "2023 年前后，有没有换过工作或职责明显变化？";
const STEM_2 = "2024 年 3 月前后，有没有收入明显变化、大笔支出或欠债？";
const RANGE_ACK = "已记录，范围没变；14:58–14:59 领先，14:40–14:43 落后。";
const COLLECT_STEM = "还有吗？比如搬家、升学或家里的大事。";

const OPTIONS = [
  { key: "A" as const, label: "明确发生且时间吻合", answer_class: "yes", role: "primary" },
  { key: "B" as const, label: "发生过但程度较弱", answer_class: "weak_yes", role: "primary" },
  { key: "C" as const, label: "没有这回事", answer_class: "no", role: "primary" },
  { key: "D" as const, label: "这段记不清楚", answer_class: "unsure", role: "primary" },
];

function choiceSchema(prompt: string) {
  return {
    prompt,
    probe_id: `probe:${prompt.slice(0, 4)}`,
    choice: {
      prompt,
      option_a: OPTIONS[0].label,
      option_b: OPTIONS[1].label,
      option_c: OPTIONS[2].label,
      option_d: OPTIONS[3].label,
      options: OPTIONS.map(({ key, label, answer_class }) => ({ key, label, answer_class })),
    },
  };
}

function focus(id: string, prompt: string, overrides: Partial<ConversationFocus> = {}): ConversationFocus {
  return {
    id,
    caseId: CASE_ID,
    questionId: `distinguish:${id.slice(-1)}`,
    intent: "distinguish_candidates",
    targetEvidenceId: null,
    targetDomain: "career",
    targetKind: null,
    expectedAnswerSchema: choiceSchema(prompt),
    status: "active",
    askedAt: "2026-09-26T08:00:00.000Z",
    resolvedAt: null,
    askedTurnId: null,
    answerOption: null,
    ...overrides,
  };
}

function collectFocus(id: string, prompt: string, askedTurnId: string): ConversationFocus {
  return focus(id, prompt, {
    questionId: "collect:open",
    intent: "collect_fact",
    expectedAnswerSchema: { prompt, collect: true },
    askedTurnId,
  });
}

function choiceCard(focusId: string, prompt: string, questionId: string) {
  return {
    question_id: questionId,
    method_id: "candidate_discriminator",
    prompt,
    choice_mode: "A/B/C/D",
    options: OPTIONS,
    focus_id: focusId,
    case_revision: 3,
    probe_id: `probe:${prompt.slice(0, 4)}`,
  };
}

type RawTurn = { id: string; role: "user" | "assistant"; text: string; status: string };

/** The GET route's turn assembly: the real `attachQuestionsToTurns`. */
function snapshot(rawTurns: RawTurn[], focuses: ConversationFocus[], current: ConversationFocus | null) {
  const turns = attachQuestionsToTurns(rawTurns, focuses);
  const collect = current && current.expectedAnswerSchema.collect === true;
  return {
    case: { status: "collecting_evidence" },
    question_source: current ? "focus" : null,
    current_question: current
      ? {
        kind: collect ? "collect_spoken" : "choice",
        prompt: current.expectedAnswerSchema.prompt,
        focus_id: current.id,
        question_id: current.questionId,
      }
      : null,
    choice_card: current && !collect
      ? choiceCard(current.id, String(current.expectedAnswerSchema.prompt), current.questionId)
      : null,
    turns,
  };
}

function ndjson(events: unknown[]): Response {
  return new Response(`${events.map((event) => JSON.stringify(event)).join("\n")}\n`, {
    status: 200,
    headers: { "content-type": "application/x-ndjson; charset=utf-8" },
  });
}

function json(body: unknown, status = 200): Response {
  return new Response(JSON.stringify(body), { status, headers: { "content-type": "application/json" } });
}

type Route = (request: { url: string; method: string; body: Record<string, unknown> | null }) => Response | Promise<Response>;

async function mountChat(input: {
  initialTurns: RawTurn[];
  initialFocuses: ConversationFocus[];
  initialCurrent: ConversationFocus | null;
  route: Route;
}) {
  const harness = createClientLifecycleHarness();
  const win = (globalThis as unknown as { window: Record<string, unknown> }).window;
  win.matchMedia = () => ({ matches: false, addEventListener() {}, removeEventListener() {} });
  win.setInterval = setInterval;
  win.clearInterval = clearInterval;
  // Host DOM has no layout: the scroll-anchor hook only needs these to exist.
  const proto = (harness.container as unknown as { constructor: { prototype: Record<string, unknown> } }).constructor.prototype;
  Object.assign(proto, {
    querySelector: () => null,
    querySelectorAll: () => [],
    getBoundingClientRect: () => ({ top: 0, bottom: 0, left: 0, right: 0, width: 0, height: 0 }),
    compareDocumentPosition: () => 0,
    scrollTo() {},
    scrollTop: 0,
    scrollHeight: 0,
    clientHeight: 0,
  });
  const doc = (globalThis as unknown as { document: { createElement: (tag: string) => { style: object } } }).document;
  const create = doc.createElement.bind(doc);
  const styled = <T extends { style: object }>(element: T): T => {
    Object.assign(element.style, { setProperty() {}, removeProperty() {}, getPropertyValue: () => "" });
    return element;
  };
  doc.createElement = (tag: string) => styled(create(tag));
  styled(harness.container as unknown as { style: object });

  const originalFetch = globalThis.fetch;
  const requests: Array<{ url: string; method: string; body: Record<string, unknown> | null }> = [];
  globalThis.fetch = (async (resource: RequestInfo | URL, init?: RequestInit) => {
    const request = {
      url: String(resource),
      method: init?.method ?? "GET",
      body: typeof init?.body === "string" ? JSON.parse(init.body) as Record<string, unknown> : null,
    };
    requests.push(request);
    return input.route(request);
  }) as typeof fetch;

  const initial = snapshot(input.initialTurns, input.initialFocuses, input.initialCurrent);
  await harness.render(
    <RectificationAgenticChat
      caseId={CASE_ID}
      sessionId={SESSION_ID}
      readonly={false}
      shouldStartOpening={false}
      initialTurns={initial.turns}
      initialSnapshot={initial}
      declaredTime="14:50"
      birthDate="1990-06-15"
      models={[]}
      selectedModelId="model"
      onSelectModel={() => {}}
      headerSlot={null}
    />,
  );
  await harness.idle();

  type Host = ReturnType<typeof harness.elements>[number];
  const byTag = (tag: string) => harness.elements().filter((node) => node.tagName === tag);
  const attr = (node: Host, name: string) => node.getAttribute(name);
  const insideDisabledFieldset = (node: Host): boolean => {
    for (let at: Host | null = node; at; at = at.parentNode as Host | null) {
      if (at.tagName === "FIELDSET" && at.hasAttribute("disabled")) return true;
    }
    return false;
  };
  // What a sighted reader sees: screen-reader-only nodes (the card's
  // `<legend className="sr-only">`) are not a second visible stem.
  const visibleText = (node: Host): string => {
    if ((node.props.className as string | undefined)?.split(/\s+/).includes("sr-only")) return "";
    return node.textContent + node.childNodes.map((child) => visibleText(child as Host)).join("");
  };
  const optionButtons = () => byTag("BUTTON").filter((node) => (node.props.className as string | undefined)?.includes("birth-time-choice-option"));
  return {
    harness,
    requests,
    text: () => visibleText(harness.container as Host),
    occurrences: (needle: string) => visibleText(harness.container as Host).split(needle).length - 1,
    cards: () => byTag("SECTION").filter((node) => (node.props.className as string | undefined)?.includes("rectification-choice-card")),
    clickableOptions: () => optionButtons().filter((node) => !insideDisabledFieldset(node)),
    selectedOptions: () => optionButtons().filter((node) => attr(node, "data-selected") === "true"),
    persistedBlocks: () => harness.elements().filter((node) => attr(node, "data-testid") === "persisted-question"),
    async type(message: string) {
      const textarea = byTag("TEXTAREA")[0];
      assert.ok(textarea, "composer textarea");
      await harness.event(textarea, "onChange", { target: { value: message } });
      const form = byTag("FORM")[0];
      assert.ok(form, "composer form");
      await harness.event(form, "onSubmit");
      for (let i = 0; i < 5; i += 1) await harness.idle();
    },
    async tap(label: string) {
      const button = optionButtons().find((node) => node.text.includes(label) && !insideDisabledFieldset(node));
      assert.ok(button, `clickable option ${label}`);
      await harness.event(button, "onClick");
      for (let i = 0; i < 5; i += 1) await harness.idle();
    },
    async close() {
      globalThis.fetch = originalFetch;
      await harness.close();
    },
  };
}

const OPENING: RawTurn = { id: "t0", role: "assistant", text: "眼下按 14:35–15:05 来核对。", status: "completed" };

test("A · typed answer to a pending choice: streamed ack+stem, then snapshot merge — the stem shows once (BUG-1045)", async () => {
  const q1 = focus(FOCUS_1, STEM_1, { askedTurnId: "t0" });
  // The server's deterministic reply for a typed answer to a pending choice
  // (`persistApplied`): the ack with the next stem appended (BUG-969 ③).
  const streamed = composeCollectSpokenAssistantText(RANGE_ACK, STEM_2);
  assert.ok(streamed.includes(STEM_2), "fixture: the stream carries the next stem");
  const chat = await mountChat({
    initialTurns: [OPENING],
    initialFocuses: [q1],
    initialCurrent: q1,
    route: ({ url, method }) => {
      if (method === "POST") return ndjson([{ type: "answer.delta", text: streamed }, { type: "run.completed", turnId: "t2" }]);
      assert.ok(url.startsWith(`/api/rectification/cases/${CASE_ID}`));
      const q1Done = { ...q1, status: "resolved" as const, answerOption: "B" as const };
      const q2 = focus(FOCUS_2, STEM_2, { askedTurnId: "t2" });
      return json(snapshot([
        OPENING,
        { id: "t1", role: "user", text: "换过，2023 年 3 月。", status: "completed" },
        { id: "t2", role: "assistant", text: streamed, status: "completed" },
      ], [q1Done, q2], q2));
    },
  });
  try {
    assert.equal(chat.occurrences(STEM_1), 1);
    await chat.type("换过，2023 年 3 月。");
    assert.equal(chat.harness.errors.length, 0, String(chat.harness.errors[0] ?? ""));
    assert.ok(chat.text().includes(RANGE_ACK), "the ack stays in the bubble");
    assert.equal(chat.occurrences(STEM_2), 1, `stem must show exactly once:\n${chat.text()}`);
    assert.equal(chat.persistedBlocks().length, 0);
    // The one visible stem is the card's: four clickable options for Q2.
    assert.equal(chat.clickableOptions().length, 4);
  } finally {
    await chat.close();
  }
});

test("A · collect denial with a next choice: streamed ack+stem from persistCollectDenialTurn shows the stem once (BUG-1045)", async () => {
  const collect = collectFocus(FOCUS_1, COLLECT_STEM, "t0");
  const q2 = focus(FOCUS_2, STEM_2);
  const accounting = fakeAccounting({
    append_agentic_rectification_turn: () => ({ turn_id: "t2", idempotent: false }),
    set_agentic_rectification_conversation_focus: (_fn, args) => ({
      focus: { ...q2, asked_turn_id: args.p_asked_turn_id, askedTurnId: args.p_asked_turn_id },
      idempotent: false,
    }),
  });
  // The real server helper produces the streamed text.
  const denial = await persistCollectDenialTurn({
    accounting: accounting.client,
    userId: USER_ID,
    caseId: CASE_ID,
    requestId: "99999999-9999-4999-8999-999999999999",
    userMessage: "想不到了",
    applied: {
      narration: STEM_2,
      ack: RECTIFICATION_USER_COPY.collectDeclinedAck,
      closeStatus: "skipped",
      nextInterviewPersisted: true,
      nextChoiceReady: true,
      focus: q2,
    },
  });
  assert.ok(denial.streamText.includes(STEM_2), "fixture: the stream carries the next stem");
  const chat = await mountChat({
    initialTurns: [{ ...OPENING, text: "记下了。" }],
    initialFocuses: [collect],
    initialCurrent: collect,
    route: ({ method }) => {
      if (method === "POST") return ndjson([{ type: "answer.delta", text: denial.streamText }, { type: "run.completed", turnId: "t2" }]);
      return json(snapshot([
        { ...OPENING, text: "记下了。" },
        { id: "t1", role: "user", text: "想不到了", status: "completed" },
        { id: "t2", role: "assistant", text: denial.streamText, status: "completed" },
      ], [{ ...collect, status: "skipped" }, { ...q2, askedTurnId: "t2" }], { ...q2, askedTurnId: "t2" }));
    },
  });
  try {
    await chat.type("想不到了");
    assert.ok(chat.text().includes(RECTIFICATION_USER_COPY.collectDeclinedAck));
    assert.equal(chat.occurrences(STEM_2), 1, `stem must show exactly once:\n${chat.text()}`);
    assert.equal(chat.persistedBlocks().length, 0);
    assert.equal(chat.clickableOptions().length, 4);
  } finally {
    await chat.close();
  }
});

for (const failure of ["409 stale_question", "network error"] as const) {
  test(`B · failed choice submit (${failure}): one clickable card, answer mark withdrawn, error copy (BUG-1046)`, async () => {
    const q1 = focus(FOCUS_1, STEM_1, { askedTurnId: "t0" });
    let snapshotReads = 0;
    const chat = await mountChat({
      initialTurns: [OPENING],
      initialFocuses: [q1],
      initialCurrent: q1,
      route: ({ method, body }) => {
        if (method === "POST") {
          assert.equal(body?.action, "answer_choice");
          assert.equal(body?.optionId, "B");
          if (failure === "network error") throw new TypeError("Failed to fetch");
          return json({ error: "这道题已经过期，请回答当前问题", message: "这道题已经过期，请回答当前问题", code: "stale_question" }, 409);
        }
        snapshotReads += 1;
        // The server never recorded the tap: Q1 is still the active question.
        return json(snapshot([OPENING], [q1], q1));
      },
    });
    try {
      assert.equal(chat.cards().length, 1);
      await chat.tap("发生过但程度较弱");
      assert.equal(chat.occurrences(STEM_1), 1, `question must show once:\n${chat.text()}`);
      assert.equal(chat.cards().length, 1, "exactly one card");
      assert.equal(chat.persistedBlocks().length, 0, "no standalone duplicate");
      assert.equal(chat.selectedOptions().length, 0, "the optimistic B mark is withdrawn");
      assert.equal(chat.clickableOptions().length, 4, "the card can be tapped again");
      assert.ok(chat.text().includes(RECTIFICATION_CHOICE_SUBMIT_FAILED_COPY), chat.text());
      assert.ok(snapshotReads >= 1, "the snapshot is reloaded after the failure");
      // A retry goes through the same card.
      await chat.tap("发生过但程度较弱");
      assert.equal(chat.requests.filter((request) => request.method === "POST").length, 2);
    } finally {
      await chat.close();
    }
  });
}

test("B · a typed answer that never reaches the server withdraws its mark: still one tappable card", async () => {
  const q1 = focus(FOCUS_1, STEM_1, { askedTurnId: "t0" });
  const chat = await mountChat({
    initialTurns: [OPENING],
    initialFocuses: [q1],
    initialCurrent: q1,
    route: ({ method }) => (method === "POST"
      ? json({ error: "模型暂不可用", message: "请选择其他模型后重新发送，本次不会扣除点数。" }, 409)
      : json(snapshot([OPENING], [q1], q1))),
  });
  try {
    await chat.type("换过");
    assert.equal(chat.occurrences(STEM_1), 1, chat.text());
    assert.equal(chat.cards().length, 1);
    assert.equal(chat.persistedBlocks().length, 0);
    assert.equal(chat.clickableOptions().length, 4);
  } finally {
    await chat.close();
  }
});

test("D3 · the live focus on an older message moves to the latest one (BUG-635) instead of being drawn twice", async () => {
  const q1 = focus(FOCUS_1, STEM_1, { askedTurnId: "t0" });
  const later: RawTurn = { id: "t2", role: "assistant", text: "记下了：2023 年 3 月换工作。", status: "completed" };
  const turns: RawTurn[] = [OPENING, { id: "t1", role: "user", text: "2023 年 3 月换了工作", status: "completed" }, later];
  const chat = await mountChat({
    initialTurns: turns,
    initialFocuses: [q1],
    initialCurrent: q1,
    route: () => json(snapshot(turns, [q1], q1)),
  });
  try {
    assert.equal(chat.occurrences(STEM_1), 1, chat.text());
    assert.equal(chat.persistedBlocks().length, 0);
    assert.equal(chat.cards().length, 1);
    assert.equal(chat.clickableOptions().length, 4);
    const text = chat.text();
    assert.ok(text.indexOf(later.text) < text.indexOf(STEM_1), "the question reads under the latest message");
  } finally {
    await chat.close();
  }
});

test("D3 · a persisted question with no asked turn hangs on the latest assistant message, never a second block", async () => {
  // The snapshot names Q1 but no turn carries it (no askedTurnId, GET could not hang it).
  const q1 = focus(FOCUS_1, STEM_1);
  const chat = await mountChat({
    initialTurns: [OPENING],
    initialFocuses: [],
    initialCurrent: q1,
    route: () => json(snapshot([OPENING], [], q1)),
  });
  try {
    assert.equal(chat.occurrences(STEM_1), 1, chat.text());
    assert.equal(chat.persistedBlocks().length, 0, "an assistant message exists: no standalone block");
    assert.equal(chat.cards().length, 1);
    assert.equal(chat.clickableOptions().length, 4);
  } finally {
    await chat.close();
  }
});

test("D3 · with no assistant message at all the standalone block is the fallback, drawn once", async () => {
  const q1 = focus(FOCUS_1, STEM_1);
  const chat = await mountChat({
    initialTurns: [{ id: "u0", role: "user", text: "我记得 2023 年换过工作。", status: "completed" }],
    initialFocuses: [],
    initialCurrent: q1,
    route: () => json(snapshot([], [], q1)),
  });
  try {
    assert.equal(chat.persistedBlocks().length, 1);
    assert.equal(chat.occurrences(STEM_1), 1, chat.text());
    assert.equal(chat.clickableOptions().length, 4);
  } finally {
    await chat.close();
  }
});

test("D4 · willContinue: a server turn the client never saw is merged in before the follow-up row, so its question is not redrawn", async () => {
  const q1 = focus(FOCUS_1, STEM_1, { askedTurnId: "t0" });
  const q1Done = { ...q1, status: "resolved" as const, answerOption: "B" as const };
  // H2: the server wrote the turn that carries Q2 while applying the tap; the
  // follow-up read_only run is a separate turn.
  const q2 = focus(FOCUS_2, STEM_2, { askedTurnId: "t2" });
  const serverTurns: RawTurn[] = [
    OPENING,
    { id: "t2", role: "assistant", text: "已记录，范围没变。", status: "completed" },
  ];
  let posts = 0;
  const chat = await mountChat({
    initialTurns: [OPENING],
    initialFocuses: [q1],
    initialCurrent: q1,
    route: ({ method }) => {
      if (method === "POST") {
        posts += 1;
        if (posts === 1) {
          return json({
            type: "choice.applied",
            narration: "已记录，范围没变。",
            nextAction: { type: "ask_candidate_discriminator" },
            nextInterviewPersisted: false,
            nextChoiceReady: false,
          });
        }
        serverTurns.push({ id: "t3", role: "assistant", text: "这一步按你的选择继续。", status: "completed" });
        return ndjson([{ type: "answer.delta", text: "这一步按你的选择继续。" }, { type: "run.completed", turnId: "t3" }]);
      }
      return json(snapshot([...serverTurns], [q1Done, q2], q2));
    },
  });
  try {
    await chat.tap("发生过但程度较弱");
    assert.equal(posts, 2, "the tap and the follow-up run");
    assert.ok(chat.text().includes("已记录，范围没变。"), `server turn t2 merged in:\n${chat.text()}`);
    assert.equal(chat.occurrences(STEM_2), 1, chat.text());
    assert.equal(chat.persistedBlocks().length, 0);
    assert.equal(chat.occurrences("已记录，范围没变。"), 1);
    const text = chat.text();
    assert.ok(text.indexOf("已记录，范围没变。") < text.indexOf("这一步按你的选择继续。"), "t2 sits before the follow-up row");
  } finally {
    await chat.close();
  }
});

test("D4 · send() settle: an extra assistant turn in the snapshot joins the transcript; the live row is not duplicated", async () => {
  const q1 = focus(FOCUS_1, STEM_1, { askedTurnId: "t0" });
  const q2 = focus(FOCUS_2, STEM_2, { askedTurnId: "t3" });
  const chat = await mountChat({
    initialTurns: [OPENING],
    initialFocuses: [q1],
    initialCurrent: q1,
    route: ({ method }) => {
      if (method === "POST") return ndjson([{ type: "answer.delta", text: "记下了：2023 年 3 月换工作。" }, { type: "run.completed", turnId: "t2" }]);
      return json(snapshot([
        OPENING,
        { id: "t1", role: "user", text: "2023 年 3 月换了工作", status: "completed" },
        { id: "t2", role: "assistant", text: "记下了：2023 年 3 月换工作。", status: "completed" },
        { id: "t3", role: "assistant", text: "接下来我们继续。", status: "completed" },
      ], [{ ...q1, status: "resolved" }, q2], q2));
    },
  });
  try {
    await chat.type("2023 年 3 月换了工作");
    assert.equal(chat.occurrences("记下了：2023 年 3 月换工作。"), 1, chat.text());
    assert.ok(chat.text().includes("接下来我们继续。"), chat.text());
    assert.equal(chat.occurrences(STEM_2), 1);
    assert.equal(chat.persistedBlocks().length, 0);
  } finally {
    await chat.close();
  }
});

test("mergeTurnQuestions drops the attached stem from the live text; appendUnseenAssistantTurns can insert before a live row", () => {
  const streamed = composeCollectSpokenAssistantText(RANGE_ACK, STEM_2);
  const question = {
    focus_id: FOCUS_2, question_id: "q2", kind: "choice" as const, prompt: STEM_2,
    options: OPTIONS.map(({ key, label }) => ({ key, label })), status: "active", answer_option: null, probe_id: null,
  };
  const [merged] = mergeTurnQuestions(
    [{ role: "assistant", turnId: "t2", text: streamed, renderKey: "live" } satisfies SnapshotTurnMessage as SnapshotTurnMessage],
    [{ id: "t2", text: RANGE_ACK, question }],
  );
  assert.equal(merged?.text, RANGE_ACK);
  assert.equal(merged?.question?.prompt, STEM_2);
  // Idempotent: a second merge leaves the text alone.
  assert.equal(mergeTurnQuestions([merged!], [{ id: "t2", question }])[0]?.text, RANGE_ACK);
  // No question on the turn: the text is never touched.
  const plain = mergeTurnQuestions(
    [{ role: "assistant" as const, turnId: "t9", text: `${RANGE_ACK}你还记得吗？`, renderKey: "p" }],
    [{ id: "t9", question: null }],
  );
  assert.equal(plain[0]?.text, `${RANGE_ACK}你还记得吗？`);

  const inserted = appendUnseenAssistantTurns(
    [
      { role: "assistant" as const, turnId: "t0", text: "a", renderKey: "a" },
      { role: "assistant" as const, text: "", renderKey: "live" },
    ],
    [{ role: "assistant" as const, turnId: "t2", text: "b", renderKey: "b" }],
    { beforeRenderKey: "live" },
  );
  assert.deepEqual(inserted.map((message) => message.renderKey), ["a", "b", "live"]);
});