fix: generate weekly quiz in a single batch LLM call

The weekly quiz path made up to six sequential LLM calls (one per topic)
with three retries each, blowing past the 30s budget. Worse, the
quiz_banks collection has been dropped, so getQuizBank/setQuizBank are
no-ops and every generated batch was thrown away — the assembled quiz
ended up empty and surfaced as "Could not assemble enough questions."

Replace the per-topic loop with a single batched call on the fast tier
that emits all five questions in one round-trip, using the review topics
as prompt context instead of separate calls.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/lib/testService.js

@@ -4,6 +4,8 @@ import { EMIT_QUIZ_QUESTIONS_TOOL } from './llmTools';
 import { getCurrentWeekContent } from './curriculumService';
 import { shuffle, sample } from './random';
 
+const QUIZ_BATCH_TIMEOUT_MS = 25_000;
+
 const QUIZ_SYSTEM = `You are a quiz generator for Respellion, an internal IT company learning platform.
 You generate multiple-choice questions to test employee knowledge on specific topics.
 Always write in clear, professional English.
@@ -218,19 +220,61 @@ export async function forceGenerateTopicQuestions(topic, count = 5) {
   return accepted;
 }
 
-async function getOrGenerateTopicQuestions(topic, count) {
-  let bank = await db.getQuizBank(topic.id);
+// Single-call batch generator used by the weekly quiz path. Generates the
+// entire 5-question test in one LLM round-trip instead of looping topic by
+// topic — the persisted quiz_banks collection is deprecated so caching can't
+// amortise multiple calls, and 6 sequential calls blew through the <30s budget.
+async function callQuizBatchModel(primaryTopic, reviewTopics, count) {
+  const reviewBlock = reviewTopics.length
+    ? `\n\nReview topics — draw ${Math.max(0, count - 3)} questions from these to broaden the test:\n${reviewTopics
+        .map((t, i) => `${i + 1}. ${t.label} (${t.type}) — ${t.description}`)
+        .join('\n')}`
+    : '';
 
-  if (bank.length < count) {
-    try {
-      await forceGenerateTopicQuestions(topic, 5);
-      bank = await db.getQuizBank(topic.id);
-    } catch (err) {
-      console.warn(`[quiz] Failed to generate questions for ${topic.label}:`, err.message);
-    }
-  }
+  const prompt = `Generate exactly ${count} multiple-choice quiz questions for this week's test and emit them via the emit_quiz_questions tool.
 
-  return sample(bank, Math.min(count, bank.length));
+Primary topic — focus 3 questions here:
+- Label: ${primaryTopic.label}
+- Type: ${primaryTopic.type}
+- Description: ${primaryTopic.description}${reviewBlock}
+
+Rules:
+- Set "topicLabel" to the label of the topic the question covers.
+- Prefix the four options with "A) ", "B) ", "C) ", "D) ".
+- Make questions specific and practical, not trivial recall.
+- Distribute correctIndex roughly evenly across 0, 1, 2, 3 within the batch.`;
+
+  const result = await callLLM({
+    task: 'quiz.batch_generate',
+    tier: 'fast',
+    system: cachedSystem(QUIZ_SYSTEM),
+    user: prompt,
+    tools: [EMIT_QUIZ_QUESTIONS_TOOL],
+    toolChoice: { type: 'tool', name: EMIT_QUIZ_QUESTIONS_TOOL.name },
+    maxTokens: 4096,
+    timeoutMs: QUIZ_BATCH_TIMEOUT_MS,
+  });
+
+  const emitted = result.toolUses[0]?.input;
+  if (!emitted) throw new Error('LLM did not emit tool output.');
+
+  let questions;
+  if (Array.isArray(emitted.questions)) questions = emitted.questions;
+  else if (Array.isArray(emitted)) questions = emitted;
+  else if (emitted.questions && typeof emitted.questions === 'object') questions = [emitted.questions];
+  else throw new Error('Unexpected quiz output shape.');
+
+  if (!questions.length) throw new Error('LLM emitted zero questions.');
+
+  return questions.map((q, i) => ({
+    id: `${primaryTopic.id}-${Date.now().toString(36)}-${i}`,
+    question: q.question || '',
+    topicLabel: q.topicLabel || primaryTopic.label,
+    options: Array.isArray(q.options) ? q.options.slice(0, 4) : [],
+    correctIndex: typeof q.correctIndex === 'number' ? q.correctIndex : 0,
+    explanation: q.explanation || 'No explanation provided.',
+    difficulty: q.difficulty || 'medium',
+  })).filter((q) => q.question && q.options.length === 4);
 }
 
 export async function getTopicQuestionBank(topicId) {
@@ -250,34 +294,41 @@ export async function generateWeeklyQuiz(userId, weekNumber, force = false) {
   const { primaryTopic, reviewTopics } = await selectTestTopics(userId, weekNumber);
   if (!primaryTopic) throw new Error('No topics available to generate a quiz.');
 
-  const questions = [];
+  // Cap review-topic context to keep the prompt focused and the call fast.
+  const reviewContext = (reviewTopics || []).slice(0, 3);
 
-  const primaryQs = await getOrGenerateTopicQuestions(primaryTopic, 3);
-  questions.push(...primaryQs);
+  let accepted = [];
+  let lastError = null;
 
-  for (const rt of reviewTopics) {
-    if (questions.length >= 5) break;
-    const rtQs = await getOrGenerateTopicQuestions(rt, 1);
-    questions.push(...rtQs);
-  }
-
-  if (questions.length < 5) {
-    const needed = 5 - questions.length;
-    const extraQs = await getOrGenerateTopicQuestions(primaryTopic, needed + 5);
-    const existingIds = new Set(questions.map(q => q.id));
-    for (const eq of extraQs) {
-      if (!existingIds.has(eq.id) && questions.length < 5) {
-        questions.push(eq);
-      }
+  for (let attempt = 0; attempt < 2; attempt++) {
+    let candidates;
+    try {
+      candidates = await callQuizBatchModel(primaryTopic, reviewContext, 5);
+    } catch (err) {
+      lastError = err.message;
+      console.warn(`[quiz] batch attempt ${attempt + 1} failed:`, err.message);
+      continue;
     }
+
+    const qualityError = validateBatchQuality(candidates);
+    if (qualityError) {
+      lastError = qualityError;
+      console.warn(`[quiz] batch quality rejected (attempt ${attempt + 1}): ${qualityError}`);
+      continue;
+    }
+
+    accepted = candidates;
+    break;
   }
 
-  const shuffled = shuffle(questions).slice(0, 5);
-
-  if (shuffled.length === 0) {
-    throw new Error('Could not assemble enough questions for this week\'s test. Please try again.');
+  if (accepted.length < 5) {
+    throw new Error(
+      `Could not generate a 5-question test for ${primaryTopic.label}${lastError ? `: ${lastError}` : ''}. Please try again.`,
+    );
   }
 
+  const shuffled = shuffle(accepted).slice(0, 5);
+
   const quiz = {
     questions: shuffled,
     meta: {