Add detailed implementation plan and tests for 2026 security audit fixes

.gitea/workflows/deploy.yml

@@ -26,11 +26,19 @@ jobs:
           echo "SSH_AUTH_SOCK=$SSH_AUTH_SOCK" >> "$GITHUB_ENV"
           echo "SSH_AGENT_PID=$SSH_AGENT_PID" >> "$GITHUB_ENV"
 
-      - name: Add OrangePi to known_hosts
+      - name: Pin server host key to known_hosts
+        env:
+          HOST_KEY: ${{ vars.SSH_HOST_PUBLIC_KEY }}
         run: |
           mkdir -p ~/.ssh
           chmod 700 ~/.ssh
-          ssh-keyscan -H "${{ secrets.ANSIBLE_HOST }}" >> ~/.ssh/known_hosts
+          if [ -z "$HOST_KEY" ]; then
+            echo "::error::Repository variable SSH_HOST_PUBLIC_KEY is not set."
+            echo "::error::Pin the server's host key instead of trusting ssh-keyscan over the network:"
+            echo "::error::run 'ssh-keyscan -t ed25519 <host>' once from a trusted network and store the full output line in SSH_HOST_PUBLIC_KEY."
+            exit 1
+          fi
+          printf '%s\n' "$HOST_KEY" >> ~/.ssh/known_hosts
 
       - name: Write Inventory
         run: |

backend/src/config.ts

@@ -26,6 +26,7 @@ export const config = {
   env: env('NODE_ENV', 'development'),
   port: envInt('PORT', 3001),
   jwtSecret: env('JWT_SECRET'),
+  jwtExpiresIn: env('JWT_EXPIRES_IN', '7d'),
   dbPath: env('DB_PATH', './db/brainwave.db'),
   corsOrigin: env('CORS_ORIGIN', 'http://localhost:5173'),
   bodyLimit: env('BODY_LIMIT', '100kb'),

backend/src/db/migrations.ts

@@ -49,8 +49,18 @@ export function runMigrations(db: Database.Database): void {
       updated_at INTEGER DEFAULT (unixepoch())
     );
 
+    CREATE TABLE IF NOT EXISTS ai_usage_daily (
+      user_id       INTEGER NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+      period_date   TEXT NOT NULL,
+      tokens_used   INTEGER NOT NULL DEFAULT 0,
+      requests_used INTEGER NOT NULL DEFAULT 0,
+      updated_at    INTEGER DEFAULT (unixepoch()),
+      PRIMARY KEY (user_id, period_date)
+    );
+
     CREATE INDEX IF NOT EXISTS idx_saved_exams_user ON saved_exams(user_id);
     CREATE INDEX IF NOT EXISTS idx_exam_results_user ON exam_results(user_id);
+    CREATE INDEX IF NOT EXISTS idx_ai_usage_daily_user ON ai_usage_daily(user_id);
   `);
 
   // ── Add share_token and is_public columns if missing ──
@@ -84,6 +94,11 @@ export function runMigrations(db: Database.Database): void {
       db.exec(`ALTER TABLE users ADD COLUMN plan TEXT NOT NULL DEFAULT 'free'`);
     }
 
+    // ── Add token_version if missing (JWT revocation on password change/reset) ──
+    if (!cols.some((c) => c.name === "token_version")) {
+      db.exec(`ALTER TABLE users ADD COLUMN token_version INTEGER NOT NULL DEFAULT 0`);
+    }
+
     // ── Add is_favorite to saved_exams if missing ──
     const examSavedCols = db.prepare(`PRAGMA table_info(saved_exams)`).all() as { name: string }[];
     if (!examSavedCols.some((c) => c.name === 'is_favorite')) {
@@ -122,16 +137,6 @@ export function runMigrations(db: Database.Database): void {
       CREATE INDEX IF NOT EXISTS idx_collections_user ON collections(user_id);
     `);
 
-  // ── Promote first user to admin if no admins exist ──
-  const adminCount = db
-    .prepare(`SELECT COUNT(*) AS cnt FROM users WHERE role = 'admin'`)
-    .get() as { cnt: number };
-  if (adminCount.cnt === 0) {
-    db.prepare(
-      `UPDATE users SET role = 'admin' WHERE id = (SELECT MIN(id) FROM users)`,
-    ).run();
-  }
-
   // ── Seed default settings ──
   const defaults: Record<string, string> = {
     site_name: "BrainWave",
@@ -149,6 +154,16 @@ export function runMigrations(db: Database.Database): void {
     smtp_from: "BrainWave <noreply@brainwave.local>",
     smtp_secure: "auto",
     app_url: "http://localhost:5173",
+    ai_provider: "",
+    ai_model: "gpt-4o-mini",
+    ai_api_key: "",
+    ai_base_url: "",
+    ai_model_hint: "",
+    ai_model_generate: "",
+    ai_model_grading: "",
+    ai_model_tutor: "",
+    ai_model_study_coach: "",
+    ai_daily_token_limit: "0",
   };
   const upsert = db.prepare(`
     INSERT INTO site_settings (key, value) VALUES (?, ?)

backend/src/middleware/auth.test.ts

@@ -0,0 +1,127 @@
+import { describe, it, expect, vi } from 'vitest'
+import type { Request, Response, NextFunction } from 'express'
+import * as userRepo from '../repositories/userRepo.js'
+import { signToken } from '../utils/tokens.js'
+import { requireAuth } from './auth.js'
+
+function mockRes(): Response {
+  const res = {} as Response
+  res.status = vi.fn(() => res) as unknown as Response['status']
+  res.json = vi.fn(() => res) as unknown as Response['json']
+  return res
+}
+
+function makeReq(token?: string): Request {
+  const headers: Record<string, string> = {}
+  if (token) headers.authorization = `Bearer ${token}`
+  return { headers } as unknown as Request
+}
+
+function createUser(role: 'user' | 'admin' = 'user'): { id: number; email: string; name: string } {
+  const email = `user-${Math.random().toString(36).slice(2)}@example.com`
+  const { id } = userRepo.createUser({
+    email,
+    passwordHash: 'x',
+    displayName: 'Test User',
+    role,
+    emailVerified: 1,
+  })
+  return { id, email, name: 'Test User' }
+}
+
+describe('requireAuth', () => {
+  it('accepts a valid token and loads fresh user data from the DB', () => {
+    const u = createUser()
+    const token = signToken({ userId: u.id, email: u.email, displayName: u.name, role: 'user', tv: 0 })
+    const req = makeReq(token)
+    const res = mockRes()
+    const next = vi.fn() as NextFunction
+
+    requireAuth(req, res, next)
+
+    expect(next).toHaveBeenCalledOnce()
+    expect(res.status).not.toHaveBeenCalled()
+    expect(req.user?.userId).toBe(u.id)
+    expect(req.user?.role).toBe('user')
+    expect(req.user?.tv).toBe(0)
+  })
+
+  it('serves the current DB role, not the role claimed by an old JWT', () => {
+    const u = createUser()
+    // Token signed while the user was still an admin
+    const staleAdminToken = signToken({ userId: u.id, email: u.email, displayName: u.name, role: 'admin', tv: 0 })
+    userRepo.updateUser(u.id, { role: 'user' })
+    const req = makeReq(staleAdminToken)
+    const res = mockRes()
+    const next = vi.fn() as NextFunction
+
+    requireAuth(req, res, next)
+
+    expect(next).toHaveBeenCalledOnce()
+    expect(req.user?.role).toBe('user')
+  })
+
+  it('rejects tokens for deleted accounts', () => {
+    const u = createUser()
+    const token = signToken({ userId: u.id, email: u.email, displayName: u.name, role: 'user', tv: 0 })
+    userRepo.deleteUser(u.id)
+    const req = makeReq(token)
+    const res = mockRes()
+    const next = vi.fn() as NextFunction
+
+    requireAuth(req, res, next)
+
+    expect(next).not.toHaveBeenCalled()
+    expect(res.status).toHaveBeenCalledWith(401)
+  })
+
+  it('rejects tokens whose token version is stale (e.g. after password change)', () => {
+    const u = createUser()
+    const oldToken = signToken({ userId: u.id, email: u.email, displayName: u.name, role: 'user', tv: 0 })
+    userRepo.updateUser(u.id, { tokenVersion: 1 })
+    const req = makeReq(oldToken)
+    const res = mockRes()
+    const next = vi.fn() as NextFunction
+
+    requireAuth(req, res, next)
+
+    expect(next).not.toHaveBeenCalled()
+    expect(res.status).toHaveBeenCalledWith(401)
+  })
+
+  it('accepts a token signed with the current token version after rotation', () => {
+    const u = createUser()
+    userRepo.updateUser(u.id, { tokenVersion: 2 })
+    const freshToken = signToken({ userId: u.id, email: u.email, displayName: u.name, role: 'user', tv: 2 })
+    const req = makeReq(freshToken)
+    const res = mockRes()
+    const next = vi.fn() as NextFunction
+
+    requireAuth(req, res, next)
+
+    expect(next).toHaveBeenCalledOnce()
+    expect(req.user?.tv).toBe(2)
+  })
+
+  it('rejects requests without a Bearer header', () => {
+    const req = makeReq()
+    const res = mockRes()
+    const next = vi.fn() as NextFunction
+
+    requireAuth(req, res, next)
+
+    expect(next).not.toHaveBeenCalled()
+    expect(res.status).toHaveBeenCalledWith(401)
+  })
+
+  it('rejects garbage tokens', () => {
+    const req = makeReq('not.a.jwt')
+    const res = mockRes()
+    const next = vi.fn() as NextFunction
+
+    requireAuth(req, res, next)
+
+    expect(next).not.toHaveBeenCalled()
+    expect(res.status).toHaveBeenCalledWith(401)
+  })
+})

backend/src/middleware/auth.ts

@@ -1,6 +1,7 @@
 import type { Request, Response, NextFunction } from 'express'
 import { verifyToken, hashToken, type JwtPayload } from '../utils/tokens.js'
 import { isTokenBlacklisted } from '../utils/tokenBlacklist.js'
+import { getUserById } from '../repositories/userRepo.js'
 
 declare global {
   namespace Express {
@@ -22,7 +23,7 @@ export function requireAuth(req: Request, res: Response, next: NextFunction): vo
   }
   try {
     const token = header.slice(7)
-    req.user = verifyToken(token)
+    const payload = verifyToken(token)
 
     // Check if the token has been blacklisted (e.g., after logout)
     if (isTokenBlacklisted(hashToken(token))) {
@@ -30,6 +31,26 @@ export function requireAuth(req: Request, res: Response, next: NextFunction): vo
       return
     }
 
+    // Revalidate against the database: deleted accounts must not keep working,
+    // and role/token-version must come from the DB rather than an old JWT claim
+    // (revocation after demotion or password change/reset).
+    const user = getUserById(payload.userId)
+    if (!user) {
+      res.status(401).json({ error: 'Account no longer exists' })
+      return
+    }
+    if ((user.token_version ?? 0) !== payload.tv) {
+      res.status(401).json({ error: 'Session expired, please sign in again' })
+      return
+    }
+
+    req.user = {
+      userId: user.id,
+      email: user.email,
+      displayName: user.display_name,
+      role: user.role,
+      tv: payload.tv,
+    }
     next()
   } catch {
     res.status(401).json({ error: 'Invalid or expired token' })

backend/src/repositories/aiUsageRepo.ts

@@ -0,0 +1,46 @@
+import { getDb } from '../db/database.js'
+
+export interface AiDailyUsage {
+  tokensUsed: number
+  requestsUsed: number
+}
+
+function normalizeCount(value: number): number {
+  if (!Number.isFinite(value) || value <= 0) return 0
+  return Math.floor(value)
+}
+
+export function getDailyUsage(userId: number, periodDate: string): AiDailyUsage {
+  const db = getDb()
+  const row = db.prepare(`
+    SELECT tokens_used, requests_used
+    FROM ai_usage_daily
+    WHERE user_id = ? AND period_date = ?
+  `).get(userId, periodDate) as { tokens_used: number; requests_used: number } | undefined
+
+  return {
+    tokensUsed: row?.tokens_used ?? 0,
+    requestsUsed: row?.requests_used ?? 0,
+  }
+}
+
+export function incrementDailyUsage(
+  userId: number,
+  periodDate: string,
+  tokensUsed: number,
+  requestsUsed = 1,
+): void {
+  const db = getDb()
+  const tokens = normalizeCount(tokensUsed)
+  const requests = normalizeCount(requestsUsed)
+  if (tokens === 0 && requests === 0) return
+
+  db.prepare(`
+    INSERT INTO ai_usage_daily (user_id, period_date, tokens_used, requests_used)
+    VALUES (?, ?, ?, ?)
+    ON CONFLICT(user_id, period_date) DO UPDATE SET
+      tokens_used = tokens_used + excluded.tokens_used,
+      requests_used = requests_used + excluded.requests_used,
+      updated_at = unixepoch()
+  `).run(userId, periodDate, tokens, requests)
+}

backend/src/repositories/userRepo.test.ts

@@ -0,0 +1,47 @@
+import { describe, it, expect } from 'vitest'
+import * as userRepo from './userRepo.js'
+
+function uniqueEmail(): string {
+  return `safe-${Math.random().toString(36).slice(2)}@example.com`
+}
+
+describe('userRepo.listUsers', () => {
+  it('never returns credential or token columns to callers', async () => {
+    const email = uniqueEmail()
+    userRepo.createUser({
+      email,
+      passwordHash: await import('bcrypt').then((b) => b.hashSync('SecretPassword1!', 10)),
+      displayName: 'Safe Listing',
+      role: 'user',
+      emailVerified: 0,
+      verifyToken: 'verify-token-hash',
+      resetToken: 'reset-token-hash',
+    })
+
+    const { users, total } = userRepo.listUsers({ search: email })
+    expect(total).toBe(1)
+    const user = users[0]!
+
+    expect(user.email).toBe(email)
+    expect(user.display_name).toBe('Safe Listing')
+    expect(user.role).toBe('user')
+
+    const keys = Object.keys(user)
+    expect(keys).not.toContain('password_hash')
+    expect(keys).not.toContain('verify_token')
+    expect(keys).not.toContain('verify_expires')
+    expect(keys).not.toContain('reset_token')
+    expect(keys).not.toContain('reset_expires')
+  })
+
+  it('still returns full rows from getUserById for internal auth use', () => {
+    const email = uniqueEmail()
+    const { id } = userRepo.createUser({
+      email,
+      passwordHash: 'internal-only',
+      displayName: 'Internal',
+      emailVerified: 1,
+    })
+    expect(userRepo.getUserById(id)?.password_hash).toBe('internal-only')
+  })
+})

backend/src/repositories/userRepo.ts

@@ -13,6 +13,7 @@ export interface DbUser {
   reset_expires: number | null
   storage_quota_bytes: number
   plan: string
+  token_version: number
   created_at: number
   updated_at: number
 }
@@ -40,6 +41,7 @@ export interface UpdateUserData {
   resetExpires?: number | null
   storageQuotaBytes?: number
   plan?: string
+  tokenVersion?: number
 }
 
 export function createUser(data: CreateUserData): { id: number } {
@@ -126,6 +128,10 @@ export function updateUser(id: number, data: UpdateUserData): boolean {
     fields.push('plan = ?')
     values.push(data.plan)
   }
+  if (data.tokenVersion !== undefined) {
+    fields.push('token_version = ?')
+    values.push(data.tokenVersion)
+  }
 
   if (fields.length === 0) return false
 
@@ -154,13 +160,30 @@ export function countAdmins(): number {
   return row.cnt
 }
 
-export function listUsers(options: { limit?: number; offset?: number; search?: string } = {}): { users: DbUser[]; total: number } {
+/** User row safe for API exposure — no password/token material. */
+export interface SafeUser {
+  id: number
+  email: string
+  display_name: string
+  role: 'user' | 'admin'
+  email_verified: number
+  plan: string
+  storage_quota_bytes: number
+  created_at: number
+}
+
+const SAFE_USER_COLUMNS =
+  'id, email, display_name, role, email_verified, plan, storage_quota_bytes, created_at'
+
+export function listUsers(options: { limit?: number; offset?: number; search?: string } = {}): { users: SafeUser[]; total: number } {
   const db = getDb()
   const limit = Math.min(options.limit ?? 50, 200)
   const offset = options.offset ?? 0
   const search = options.search ?? ''
 
-  let query = 'SELECT * FROM users'
+  // Explicit column list so credential/token material can never leak into
+  // API responses, even if new sensitive columns are added later.
+  let query = `SELECT ${SAFE_USER_COLUMNS} FROM users`
   let countQuery = 'SELECT COUNT(*) AS total FROM users'
   const params: unknown[] = []
   const countParams: unknown[] = []
@@ -175,13 +198,8 @@ export function listUsers(options: { limit?: number; offset?: number; search?: s
   query += ' ORDER BY created_at DESC LIMIT ? OFFSET ?'
   params.push(limit, offset)
 
-  const users = db.prepare(query).all(...params) as DbUser[]
+  const users = db.prepare(query).all(...params) as SafeUser[]
   const countRow = db.prepare(countQuery).get(...countParams) as { total: number }
 
   return { users, total: countRow.total }
 }
-
-export function promoteFirstUserToAdmin(): void {
-  const db = getDb()
-  db.prepare("UPDATE users SET role = 'admin' WHERE id = (SELECT MIN(id) FROM users)").run()
-}

backend/src/routes/admin.ts

@@ -162,7 +162,7 @@ router.post(
       },
       { provider, apiKey, model, baseURL },
     )
-    res.json(result)
+    res.json(result.data)
   }),
 )
 

backend/src/routes/ai.ts

@@ -5,6 +5,8 @@ import { asyncHandler } from '../utils/asyncHandler.js'
 import { requireAuth } from '../middleware/auth.js'
 import { generateQuestions, getHint, tutorChat } from '../services/aiAssist.js'
 import { getResultById } from '../repositories/resultRepo.js'
+import { enforceDailyAiQuota, recordDailyAiUsage, getUtcDateKey } from '../utils/aiQuota.js'
+import { hintSchema } from '../validators/aiSchemas.js'
 
 const router = Router()
 router.use(requireAuth)
@@ -39,23 +41,24 @@ router.post(
   validateBody(generateSchema),
   asyncHandler(async (req, res) => {
     const body = req.body as z.infer<typeof generateSchema>
-    const questions = await generateQuestions(body)
-    res.json({ questions })
+    const userId = req.user!.userId
+    enforceDailyAiQuota(userId)
+    const result = await generateQuestions(body)
+    recordDailyAiUsage(userId, getUtcDateKey(), result.usageTokens)
+    res.json({ questions: result.data })
   }),
 )
 
-const hintSchema = z.object({
-  question: z.record(z.unknown()),
-  language: z.string().min(1).max(20),
-})
-
 router.post(
   '/hint',
   validateBody(hintSchema),
   asyncHandler(async (req, res) => {
-    const body = req.body as z.infer<typeof hintSchema>
-    const result = await getHint(body)
-    res.json(result)
+    const body = req.body
+    const userId = req.user!.userId
+    enforceDailyAiQuota(userId)
+    const result = await getHint({ question: body.question, language: body.language })
+    recordDailyAiUsage(userId, getUtcDateKey(), result.usageTokens)
+    res.json(result.data)
   }),
 )
 
@@ -130,6 +133,8 @@ router.post(
       state = {}
     }
 
+    enforceDailyAiQuota(userId)
+
     const reply = await tutorChat({
       exam,
       state,
@@ -143,8 +148,9 @@ router.post(
       messages: body.messages,
       language: body.language,
     })
+    recordDailyAiUsage(userId, getUtcDateKey(), reply.usageTokens)
 
-    res.json(reply)
+    res.json(reply.data)
   }),
 )
 

backend/src/routes/auth.ts

@@ -6,8 +6,9 @@ import { requireAuth } from '../middleware/auth.js'
 import { asyncHandler } from '../utils/asyncHandler.js'
 import * as authService from '../services/authService.js'
 import * as userRepo from '../repositories/userRepo.js'
-import { hashToken } from '../utils/tokens.js'
+import { hashToken, verifyToken } from '../utils/tokens.js'
 import { blacklistToken } from '../utils/tokenBlacklist.js'
+import { AppError } from '../middleware/error.js'
 import {
   registerSchema,
   loginSchema,
@@ -44,8 +45,7 @@ router.post(
   authLimiter,
   validateBody(registerSchema),
   asyncHandler(async (req, res) => {
-    const isFirstUser = userRepo.countUsers() === 0
-    const result = await authService.register(req.body, isFirstUser)
+    const result = await authService.register(req.body)
     res.json(result)
   })
 )
@@ -145,9 +145,18 @@ router.post(
     if (header?.startsWith('Bearer ')) {
       const token = header.slice(7)
       const tokenHash = hashToken(token)
-      // Blacklist the token so it cannot be reused after logout
-      // Expiry is 24h from now (matching JWT expiry)
-      blacklistToken(tokenHash, Date.now() + 24 * 60 * 60 * 1000)
+      // Blacklist until the token's real expiry so it cannot be replayed even
+      // after the in-memory blacklist is reloaded from SQLite on restart
+      try {
+        const decoded = verifyToken(token)
+        const expiresAt =
+          typeof decoded.exp === 'number' && decoded.exp * 1000 > Date.now()
+            ? decoded.exp * 1000
+            : Date.now() + 60 * 1000
+        blacklistToken(tokenHash, expiresAt)
+      } catch {
+        // Token already failed verification — nothing worth blacklisting
+      }
     }
     res.json({ success: true })
   })
@@ -158,6 +167,10 @@ router.delete(
   '/me',
   requireAuth,
   asyncHandler(async (req: Request, res) => {
+    const user = userRepo.getUserById(req.user!.userId)
+    if (user?.role === 'admin' && userRepo.countAdmins() <= 1) {
+      throw new AppError(400, 'Cannot delete the last admin account')
+    }
     authService.deleteUserAccount(req.user!.userId)
     res.json({ success: true })
   })

backend/src/routes/grade.ts

@@ -1,16 +1,10 @@
 import { Router } from 'express'
-import { z } from 'zod'
 import { validateBody } from '../middleware/validate.js'
 import { asyncHandler } from '../utils/asyncHandler.js'
 import { requireAuth } from '../middleware/auth.js'
 import { gradeQuestionWithAI } from '../services/aiGrading.js'
-
-const gradeRequestSchema = z.object({
-  type: z.enum(['essay', 'short-answer', 'translation', 'math', 'ordering', 'match']),
-  question: z.record(z.unknown()),
-  answer: z.unknown(),
-  language: z.string().min(1),
-})
+import { enforceDailyAiQuota, recordDailyAiUsage, getUtcDateKey } from '../utils/aiQuota.js'
+import { gradeRequestSchema, type GradeRequestBody } from '../validators/gradeSchemas.js'
 
 const router = Router()
 
@@ -20,9 +14,12 @@ router.post(
   '/',
   validateBody(gradeRequestSchema),
   asyncHandler(async (req, res) => {
-    const { type, question, answer, language } = req.body as z.infer<typeof gradeRequestSchema>
+    const { type, question, answer, language } = req.body as GradeRequestBody
+    const userId = req.user!.userId
+    enforceDailyAiQuota(userId)
     const result = await gradeQuestionWithAI({ type, question, answer, language })
-    res.json(result)
+    recordDailyAiUsage(userId, getUtcDateKey(), result.usageTokens)
+    res.json(result.data)
   }),
 )
 

backend/src/routes/results.ts

@@ -7,6 +7,7 @@ import * as resultRepo from '../repositories/resultRepo.js'
 import * as examRepo from '../repositories/examRepo.js'
 import { submitResultSchema, resultIdParamSchema } from '../validators/resultSchemas.js'
 import { analyzeResults } from '../services/studyCoach.js'
+import { enforceDailyAiQuota, recordDailyAiUsage, getUtcDateKey } from '../utils/aiQuota.js'
 import type { Request } from 'express'
 
 const router = Router()
@@ -84,9 +85,12 @@ router.delete(
 router.get(
   '/analyze',
   asyncHandler(async (req: Request, res) => {
-    const rawResults = resultRepo.getResultsWithExamJson(req.user!.userId, 200)
+    const userId = req.user!.userId
+    const rawResults = resultRepo.getResultsWithExamJson(userId, 200)
     const lang = typeof req.query.lang === 'string' ? req.query.lang : 'en'
+    enforceDailyAiQuota(userId)
     const analysis = await analyzeResults(rawResults, lang)
+    recordDailyAiUsage(userId, getUtcDateKey(), analysis.usageTokens)
 
     // Find weakest exam (lowest score that still exists in workspace)
     let weakestExamId: number | null = null
@@ -107,7 +111,7 @@ router.get(
       }
     }
 
-    res.json({ ...analysis, weakestExamId })
+    res.json({ ...analysis.data, weakestExamId })
   })
 )
 

backend/src/routes/setup.ts

@@ -22,8 +22,11 @@ router.get(
   '/status',
   asyncHandler(async (_req, res) => {
     const title = getSiteTitle()
+    // Setup is complete once an admin account exists — not merely because
+    // default settings were seeded
+    const completed = userRepo.countAdmins() > 0
     res.json({
-      completed: !!title,
+      completed,
       siteTitle: title ?? undefined,
     })
   })
@@ -38,16 +41,12 @@ router.post(
 
     // Atomic transaction prevents race conditions between concurrent setup requests
     const tx = db.transaction(() => {
-      const title = settingsRepo.getSetting('site_name')
-      if (title) {
+      // Gate on admins, not on users or settings: a fresh instance has default
+      // settings seeded, and an instance that lost its admin can re-bootstrap
+      if (userRepo.countAdmins() > 0) {
         throw new AppError(400, 'Setup already completed')
       }
 
-      const userCount = userRepo.countUsers()
-      if (userCount > 0) {
-        throw new AppError(400, 'Users already exist')
-      }
-
       const {
         email,
         password,
@@ -99,6 +98,7 @@ router.post(
       email,
       displayName,
       role: 'admin',
+      tv: 0,
     })
 
     res.status(201).json({

backend/src/routes/share.test.ts

@@ -0,0 +1,14 @@
+import { describe, it, expect } from 'vitest'
+import { canClone } from './share.js'
+
+describe('canClone', () => {
+  it('rejects view-only shares', () => {
+    expect(canClone('view')).toBe(false)
+  })
+
+  it('allows clone-mode shares and legacy rows without a mode', () => {
+    expect(canClone('clone')).toBe(true)
+    expect(canClone(null)).toBe(true)
+    expect(canClone(undefined)).toBe(true)
+  })
+})

backend/src/routes/share.ts

@@ -7,6 +7,12 @@ import type { Request } from 'express'
 
 const router = Router()
 
+/** Server-side enforcement of the share mode: 'view' shares must not be
+ * clonable (the frontend hides the button, but that is not a control). */
+export function canClone(shareMode: string | null | undefined): boolean {
+  return shareMode !== 'view'
+}
+
 // GET /api/share/:token — public, no auth required
 router.get(
   '/:token',
@@ -37,6 +43,9 @@ router.post(
     if (!source) {
       throw new AppError(404, 'Shared exam not found')
     }
+    if (!canClone(source.share_mode)) {
+      throw new AppError(403, 'This exam is shared as view-only and cannot be saved')
+    }
     const { id } = examRepo.cloneExam(req.user!.userId, source, token)
     res.status(201).json({ id, title: source.title + ' (copy)' })
   })

backend/src/services/aiAssist.ts

@@ -1,5 +1,7 @@
 import { z } from 'zod'
-import { getAIClient, getAIModel } from './aiClient.js'
+import { getAIClient, getAIModelForTask } from './aiClient.js'
+import { AiUsageResult, estimateTokensFromMessages, estimateTokensFromText, estimateTotalTokens, resolveUsageTokens } from '../utils/aiTokens.js'
+import type { ChatCompletionMessageParam } from 'openai/resources/index.js'
 
 export type QuestionType =
   | 'multiple-choice'
@@ -141,14 +143,14 @@ function shapeHintForType(type: QuestionType): string {
   }
 }
 
-export async function generateQuestions(req: GenerateQuestionsRequest): Promise<GeneratedQuestion[]> {
+export async function generateQuestions(req: GenerateQuestionsRequest): Promise<AiUsageResult<GeneratedQuestion[]>> {
   const client = getAIClient()
   if (!client) {
     throw new Error('AI is not configured. Please set provider and API key in admin settings.')
   }
 
   const count = Math.max(1, Math.min(10, Math.floor(req.count)))
-  const model = getAIModel()
+  const model = getAIModelForTask('question_generation')
   const shape = shapeHintForType(req.type)
 
   const prompt = `You are an exam author. Generate ${count} high-quality "${req.type}" exam question(s) about the following topic.
@@ -164,6 +166,9 @@ Respond ONLY with a JSON object of the form:
 
 Each question object must have "type": "${req.type}" and the fields listed above. Do not include "id" — that will be assigned later. Do not include any text outside the JSON object.`
 
+  const promptTokens = estimateTokensFromText(prompt)
+  const estimatedTokens = estimateTotalTokens(promptTokens, 1800)
+
   const completion = await client.chat.completions.create({
     model,
     messages: [{ role: 'user', content: prompt }],
@@ -172,6 +177,8 @@ Each question object must have "type": "${req.type}" and the fields listed above
     max_completion_tokens: 1800,
   })
 
+  const usageTokens = resolveUsageTokens(completion.usage, estimatedTokens)
+
   const raw = completion.choices[0]?.message?.content
   if (!raw) {
     throw new Error('Empty response from AI provider')
@@ -200,7 +207,7 @@ Each question object must have "type": "${req.type}" and the fields listed above
   if (validated.length === 0) {
     throw new Error('AI returned no valid questions for the requested type')
   }
-  return validated
+  return { data: validated, usageTokens }
 }
 
 export interface HintRequest {
@@ -219,32 +226,39 @@ function stripAnswerFields(question: Record<string, unknown>): Record<string, un
   return clone
 }
 
-export async function getHint(req: HintRequest): Promise<{ hint: string }> {
+export async function getHint(req: HintRequest): Promise<AiUsageResult<{ hint: string }>> {
   const client = getAIClient()
   if (!client) {
     throw new Error('AI is not configured. Please set provider and API key in admin settings.')
   }
 
   const safeQuestion = stripAnswerFields(req.question)
-  const model = getAIModel()
+  const model = getAIModelForTask('hint')
+
+  const messages: ChatCompletionMessageParam[] = [
+    {
+      role: 'system',
+      content: `You are a tutor helping a student during an exam. Give exactly one short hint (1-2 sentences) in ${req.language} that nudges the student toward the right approach. Never reveal the answer, never restate the answer in different words, and never give the answer to a multiple-choice option. Focus on the concept or strategy. Respond ONLY with a JSON object: { "hint": string }.`,
+    },
+    {
+      role: 'user',
+      content: `Question:\n${JSON.stringify(safeQuestion)}`,
+    },
+  ]
+
+  const promptTokens = estimateTokensFromMessages(messages as Array<{ content: string }>)
+  const estimatedTokens = estimateTotalTokens(promptTokens, 160)
 
   const completion = await client.chat.completions.create({
     model,
-    messages: [
-      {
-        role: 'system',
-        content: `You are a tutor helping a student during an exam. Give exactly one short hint (1-2 sentences) in ${req.language} that nudges the student toward the right approach. Never reveal the answer, never restate the answer in different words, and never give the answer to a multiple-choice option. Focus on the concept or strategy. Respond ONLY with a JSON object: { "hint": string }.`,
-      },
-      {
-        role: 'user',
-        content: `Question:\n${JSON.stringify(safeQuestion)}`,
-      },
-    ],
+    messages,
     response_format: { type: 'json_object' },
     temperature: 0.4,
     max_completion_tokens: 160,
   })
 
+  const usageTokens = resolveUsageTokens(completion.usage, estimatedTokens)
+
   const raw = completion.choices[0]?.message?.content
   if (!raw) {
     throw new Error('Empty response from AI provider')
@@ -260,7 +274,7 @@ export async function getHint(req: HintRequest): Promise<{ hint: string }> {
   if (!hint) {
     throw new Error('AI did not return a hint')
   }
-  return { hint }
+  return { data: { hint }, usageTokens }
 }
 
 export interface TutorChatMessage {
@@ -282,13 +296,13 @@ export interface TutorChatRequest {
   language: string
 }
 
-export async function tutorChat(req: TutorChatRequest): Promise<{ reply: string }> {
+export async function tutorChat(req: TutorChatRequest): Promise<AiUsageResult<{ reply: string }>> {
   const client = getAIClient()
   if (!client) {
     throw new Error('AI is not configured. Please set provider and API key in admin settings.')
   }
 
-  const model = getAIModel()
+  const model = getAIModelForTask('tutor_chat')
   const recent = req.messages.slice(-10)
 
   const systemPrompt = `You are a friendly, concise tutor reviewing a completed exam attempt with a student. Reply in ${req.language}. Keep answers short (under 200 words). When the student references a question by number, use the exam's question order. You may explain mistakes, give similar practice problems, or clarify rubric criteria. You may reference the student's actual answers and the AI feedback already produced. Never invent score numbers — use only what's in the exam summary.
@@ -302,19 +316,25 @@ Exam (JSON): ${JSON.stringify(req.exam).slice(0, 8000)}
 
 Student's submission state (answers, flags, etc., JSON): ${JSON.stringify(req.state).slice(0, 4000)}`
 
+  const messages: ChatCompletionMessageParam[] = [
+    { role: 'system', content: systemPrompt },
+    ...recent.map((m) => ({ role: m.role, content: m.content })),
+  ]
+  const promptTokens = estimateTokensFromMessages(messages as Array<{ content: string }>)
+  const estimatedTokens = estimateTotalTokens(promptTokens, 600)
+
   const completion = await client.chat.completions.create({
     model,
-    messages: [
-      { role: 'system', content: systemPrompt },
-      ...recent.map((m) => ({ role: m.role, content: m.content })),
-    ],
+    messages,
     temperature: 0.5,
     max_completion_tokens: 600,
   })
 
+  const usageTokens = resolveUsageTokens(completion.usage, estimatedTokens)
+
   const reply = completion.choices[0]?.message?.content?.trim()
   if (!reply) {
     throw new Error('Empty response from AI provider')
   }
-  return { reply }
+  return { data: { reply }, usageTokens }
 }

backend/src/services/aiClient.ts

@@ -7,6 +7,8 @@ export interface AIClientOverride {
   baseURL?: string
 }
 
+export type AiTask = 'hint' | 'question_generation' | 'grading' | 'tutor_chat' | 'study_coach'
+
 export function getAIClient(override?: AIClientOverride): OpenAI | null {
   const provider = override?.provider ?? getSetting('ai_provider')
   const apiKey = override?.apiKey ?? getSetting('ai_api_key')
@@ -20,3 +22,24 @@ export function getAIClient(override?: AIClientOverride): OpenAI | null {
 export function getAIModel(override?: string): string {
   return override || getSetting('ai_model') || 'gpt-4o-mini'
 }
+
+const TASK_MODEL_KEYS: Record<AiTask, string> = {
+  hint: 'ai_model_hint',
+  question_generation: 'ai_model_generate',
+  grading: 'ai_model_grading',
+  tutor_chat: 'ai_model_tutor',
+  study_coach: 'ai_model_study_coach',
+}
+
+function normalizeModel(value: string | undefined): string | undefined {
+  const trimmed = value?.trim()
+  return trimmed ? trimmed : undefined
+}
+
+export function getAIModelForTask(task: AiTask, override?: string): string {
+  const explicit = normalizeModel(override)
+  if (explicit) return explicit
+
+  const taskModel = normalizeModel(getSetting(TASK_MODEL_KEYS[task]))
+  return taskModel || getAIModel()
+}

backend/src/services/aiGrading.ts

@@ -1,4 +1,5 @@
-import { getAIClient, getAIModel } from './aiClient.js'
+import { getAIClient, getAIModelForTask } from './aiClient.js'
+import { AiUsageResult, estimateTokensFromText, estimateTotalTokens, resolveUsageTokens } from '../utils/aiTokens.js'
 
 export interface GradingResult {
   suggestedGrade: number
@@ -133,14 +134,16 @@ Use the human-readable text labels in the arrays.`
 export async function gradeQuestionWithAI(
   req: GradeRequest,
   override?: { provider?: string; apiKey?: string; baseURL?: string; model?: string },
-): Promise<GradingResult> {
+): Promise<AiUsageResult<GradingResult>> {
   const client = getAIClient(override)
   if (!client) {
     throw new Error('AI grading is not configured. Please set provider and API key in admin settings.')
   }
 
-  const model = getAIModel(override?.model)
+  const model = getAIModelForTask('grading', override?.model)
   const prompt = buildPrompt(req)
+  const promptTokens = estimateTokensFromText(prompt)
+  const estimatedTokens = estimateTotalTokens(promptTokens, 800)
 
   const completion = await client.chat.completions.create({
     model,
@@ -150,6 +153,8 @@ export async function gradeQuestionWithAI(
     max_completion_tokens: 800,
   })
 
+  const usageTokens = resolveUsageTokens(completion.usage, estimatedTokens)
+
   const raw = completion.choices[0]?.message?.content
   if (!raw) {
     throw new Error('Empty response from AI provider')
@@ -168,8 +173,11 @@ export async function gradeQuestionWithAI(
     : 0
 
   return {
+    data: {
     suggestedGrade,
     feedback: typeof obj.feedback === 'string' ? obj.feedback : '',
     detail: obj.detail,
+    },
+    usageTokens,
   }
 }

backend/src/services/authService.test.ts

@@ -0,0 +1,106 @@
+import { describe, it, expect, vi } from 'vitest'
+import bcrypt from 'bcrypt'
+
+vi.mock('../utils/email.js', async (importOriginal) => ({
+  ...(await importOriginal<object>()),
+  sendVerificationEmail: vi.fn(async () => {}),
+  sendPasswordResetEmail: vi.fn(async () => {}),
+}))
+
+import * as authService from './authService.js'
+import { sendPasswordResetEmail } from '../utils/email.js'
+import * as userRepo from '../repositories/userRepo.js'
+
+async function seedUser(overrides: Partial<userRepo.CreateUserData> = {}): Promise<number> {
+  const email = overrides.email ?? `svc-${Math.random().toString(36).slice(2)}@example.com`
+  const { id } = userRepo.createUser({
+    email,
+    passwordHash: await bcrypt.hash('OldPassword1!', 10),
+    displayName: 'Svc Test',
+    emailVerified: 1,
+    ...overrides,
+  })
+  return id
+}
+
+describe('authService.register', () => {
+  it('registers new accounts as plain users (admin bootstrap is the setup wizard)', async () => {
+    const email = `new-${Math.random().toString(36).slice(2)}@example.com`
+    const result = await authService.register({
+      email,
+      password: 'Sup3rSecure!pass',
+      displayName: 'New User',
+    })
+
+    if (!('token' in result)) throw new Error('expected an AuthResult with a token')
+    expect(result.token).toBeTruthy()
+    expect(result.user.role).toBe('user')
+
+    const dbUser = userRepo.getUserByEmail(email)
+    expect(dbUser?.role).toBe('user')
+    expect(dbUser?.email_verified).toBe(0)
+  })
+
+  it('responds to duplicate emails with a token-less success-shaped body (no enumeration oracle)', async () => {
+    const id = await seedUser()
+    const existing = userRepo.getUserById(id)!
+
+    const before = userRepo.countUsers()
+    const result = await authService.register({
+      email: existing.email.toUpperCase(),
+      password: 'Whatever!123',
+      displayName: 'Imposter',
+    })
+
+    expect('token' in result).toBe(false)
+    expect('message' in result && typeof result.message).toBe('string')
+    expect(userRepo.countUsers()).toBe(before)
+
+    // The original account must be untouched
+    const after = userRepo.getUserById(id)!
+    expect(after.display_name).toBe(existing.display_name)
+  })
+})
+
+describe('password rotation revokes sessions', () => {
+  it('changePassword bumps token_version', async () => {
+    const id = await seedUser()
+    const before = userRepo.getUserById(id)!
+
+    await authService.changePassword(id, { currentPassword: 'OldPassword1!', newPassword: 'N3wPassword!x' })
+
+    const after = userRepo.getUserById(id)!
+    expect(after.password_hash).not.toBe(before.password_hash)
+    expect(after.token_version).toBe((before.token_version ?? 0) + 1)
+  })
+
+  it('changePassword rejects a wrong current password', async () => {
+    const id = await seedUser()
+    const before = userRepo.getUserById(id)!
+
+    await expect(
+      authService.changePassword(id, { currentPassword: 'WrongPassword!', newPassword: 'N3wPassword!x' }),
+    ).rejects.toThrow()
+
+    expect(userRepo.getUserById(id)!.token_version).toBe(before.token_version)
+  })
+
+  it('resetPassword bumps token_version and clears the reset token', async () => {
+    const id = await seedUser({ emailVerified: 0 })
+    const user = userRepo.getUserById(id)!
+    const email = user.email
+
+    await authService.forgotPassword(email)
+    const calls = vi.mocked(sendPasswordResetEmail).mock.calls
+    const rawToken = calls.at(-1)?.[1] as string | undefined
+    expect(rawToken).toBeTruthy()
+
+    await authService.resetPassword({ token: rawToken!, newPassword: 'BrandNew!123' })
+    const after = userRepo.getUserById(id)!
+
+    expect(after.token_version).toBe((user.token_version ?? 0) + 1)
+    expect(after.reset_token).toBeNull()
+    expect(after.reset_expires).toBeNull()
+    expect(bcrypt.compareSync('BrandNew!123', after.password_hash)).toBe(true)
+  })
+})

backend/src/services/authService.ts

@@ -15,14 +15,41 @@ export interface AuthResult {
   user: { id: number; email: string; displayName: string; role: string }
 }
 
-export async function register(input: RegisterInput, isFirstUser: boolean): Promise<AuthResult> {
+/** Response for a registration attempt we did not act on (email already exists).
+ * Deliberately indistinguishable from success so the endpoint cannot be used
+ * to enumerate registered email addresses. */
+export interface RegistrationPending {
+  message: string
+}
+
+function toAuthResult(user: userRepo.DbUser): AuthResult {
+  return {
+    token: signToken({
+      userId: user.id,
+      email: user.email,
+      displayName: user.display_name,
+      role: user.role as 'user' | 'admin',
+      tv: user.token_version ?? 0,
+    }),
+    user: {
+      id: user.id,
+      email: user.email,
+      displayName: user.display_name,
+      role: user.role,
+    },
+  }
+}
+
+export async function register(input: RegisterInput): Promise<AuthResult | RegistrationPending> {
+  // Hash before the duplicate check so response timing does not reveal whether
+  // the email is already registered (user enumeration)
+  const passwordHash = await bcrypt.hash(input.password, SALT_ROUNDS)
+
   const existing = userRepo.getUserByEmail(input.email)
   if (existing) {
-    throw new AppError(400, 'Email already registered')
+    return { message: 'Check your inbox to finish setting up your account.' }
   }
 
-  const passwordHash = await bcrypt.hash(input.password, SALT_ROUNDS)
-  const role = isFirstUser ? 'admin' : 'user'
   const rawVerifyToken = generateVerificationToken()
   const verifyTokenHash = hashToken(rawVerifyToken)
   const verifyExpires = Date.now() + VERIFY_TOKEN_EXPIRY_MS
@@ -31,7 +58,7 @@ export async function register(input: RegisterInput, isFirstUser: boolean): Prom
     email: input.email,
     passwordHash,
     displayName: input.displayName,
-    role,
+    role: 'user',
     emailVerified: 0,
     verifyToken: verifyTokenHash,
     verifyExpires,
@@ -42,20 +69,7 @@ export async function register(input: RegisterInput, isFirstUser: boolean): Prom
   // Don't await — fire and forget so registration isn't blocked by email failures
   sendVerificationEmail(user.email, rawVerifyToken).catch(() => {})
 
-  return {
-    token: signToken({
-      userId: user.id,
-      email: user.email,
-      displayName: user.display_name,
-      role: user.role as 'user' | 'admin',
-    }),
-    user: {
-      id: user.id,
-      email: user.email,
-      displayName: user.display_name,
-      role: user.role,
-    },
-  }
+  return toAuthResult(user)
 }
 
 export async function login(input: LoginInput): Promise<AuthResult> {
@@ -73,20 +87,7 @@ export async function login(input: LoginInput): Promise<AuthResult> {
     throw new AppError(403, 'Please verify your email before logging in')
   }
 
-  return {
-    token: signToken({
-      userId: user.id,
-      email: user.email,
-      displayName: user.display_name,
-      role: user.role as 'user' | 'admin',
-    }),
-    user: {
-      id: user.id,
-      email: user.email,
-      displayName: user.display_name,
-      role: user.role,
-    },
-  }
+  return toAuthResult(user)
 }
 
 export function getMe(userId: number) {
@@ -128,7 +129,11 @@ export async function changePassword(userId: number, input: ChangePasswordInput)
   }
 
   const passwordHash = await bcrypt.hash(input.newPassword, SALT_ROUNDS)
-  userRepo.updateUser(userId, { passwordHash })
+  // Bump token version so tokens issued before the change stop working
+  userRepo.updateUser(userId, {
+    passwordHash,
+    tokenVersion: (user.token_version ?? 0) + 1,
+  })
 }
 
 export async function verifyEmail(input: VerifyEmailInput) {
@@ -192,10 +197,12 @@ export async function resetPassword(input: ResetPasswordInput) {
   }
 
   const passwordHash = await bcrypt.hash(input.newPassword, SALT_ROUNDS)
+  // Bump token version so tokens from before the reset stop working
   userRepo.updateUser(user.id, {
     passwordHash,
     resetToken: null,
     resetExpires: null,
+    tokenVersion: (user.token_version ?? 0) + 1,
   })
 }
 

backend/src/services/studyCoach.ts

@@ -1,4 +1,5 @@
-import { getAIClient, getAIModel } from './aiClient.js'
+import { getAIClient, getAIModelForTask } from './aiClient.js'
+import { AiUsageResult, estimateTokensFromText, estimateTotalTokens, resolveUsageTokens } from '../utils/aiTokens.js'
 
 export interface WeakArea {
   category: string
@@ -71,7 +72,8 @@ export async function analyzeResults(
     exam_json: string
   }>,
   language = 'en',
-): Promise<StudyCoachResult> {
+  options?: { allowAi?: boolean },
+): Promise<AiUsageResult<StudyCoachResult>> {
   const streakDays = calculateStreak(results)
 
   // Build per-category stats from exam_json
@@ -116,11 +118,11 @@ export async function analyzeResults(
     .slice(0, 5)
 
   const client = getAIClient()
-  if (!client || weakAreas.length === 0) {
-    return { weakAreas, studyTips: [], streakDays }
+  if (!client || weakAreas.length === 0 || options?.allowAi === false) {
+    return { data: { weakAreas, studyTips: [], streakDays }, usageTokens: 0 }
   }
 
-  const model = getAIModel()
+  const model = getAIModelForTask('study_coach')
   const prompt = `You are a study coach. A student has taken several practice exams. Based on their performance per category, suggest 2-3 concise study tips to help them improve in their weakest areas. Respond ONLY with a JSON object containing:
 - "studyTips": string[] (2-3 short tips in ${language})
 
@@ -129,6 +131,9 @@ Do not include any text outside the JSON object.
 Weak areas (score %, attempts):
 ${weakAreas.map((w) => `- ${w.category}: ${w.avgScore}% over ${w.attempts} attempt(s)`).join('\n')}`
 
+  const promptTokens = estimateTokensFromText(prompt)
+  const estimatedTokens = estimateTotalTokens(promptTokens, 400)
+
   try {
     const completion = await client.chat.completions.create({
       model,
@@ -138,9 +143,11 @@ ${weakAreas.map((w) => `- ${w.category}: ${w.avgScore}% over ${w.attempts} attem
       max_completion_tokens: 400,
     })
 
+    const usageTokens = resolveUsageTokens(completion.usage, estimatedTokens)
+
     const raw = completion.choices[0]?.message?.content
     if (!raw) {
-      return { weakAreas, studyTips: [], streakDays }
+      return { data: { weakAreas, studyTips: [], streakDays }, usageTokens: 0 }
     }
 
     const parsed = JSON.parse(raw) as Record<string, unknown>
@@ -148,8 +155,8 @@ ${weakAreas.map((w) => `- ${w.category}: ${w.avgScore}% over ${w.attempts} attem
       ? parsed.studyTips.filter((t): t is string => typeof t === 'string')
       : []
 
-    return { weakAreas, studyTips: tips, streakDays }
+    return { data: { weakAreas, studyTips: tips, streakDays }, usageTokens }
   } catch {
-    return { weakAreas, studyTips: [], streakDays }
+    return { data: { weakAreas, studyTips: [], streakDays }, usageTokens: 0 }
   }
 }

backend/src/utils/aiQuota.test.ts

@@ -0,0 +1,54 @@
+import { describe, it, expect } from 'vitest'
+import * as settingsRepo from '../repositories/settingsRepo.js'
+import * as aiUsageRepo from '../repositories/aiUsageRepo.js'
+import * as userRepo from '../repositories/userRepo.js'
+import { enforceDailyAiQuota, getDailyTokenLimit, getUtcDateKey } from './aiQuota.js'
+import { AppError } from '../middleware/error.js'
+
+function seedUser(): number {
+  const email = `quota-${Math.random().toString(36).slice(2)}@example.com`
+  return userRepo.createUser({
+    email,
+    passwordHash: 'x',
+    displayName: 'Quota Test',
+    emailVerified: 1,
+  }).id
+}
+
+describe('daily AI token quota', () => {
+  it('allows everything when no limit is configured', () => {
+    settingsRepo.setSetting('ai_daily_token_limit', '0')
+    expect(getDailyTokenLimit()).toBeNull()
+    expect(() => enforceDailyAiQuota(seedUser())).not.toThrow()
+  })
+
+  it('blocks with a 429 once used tokens reach the configured limit', () => {
+    settingsRepo.setSetting('ai_daily_token_limit', '1000')
+    const userId = seedUser()
+    aiUsageRepo.incrementDailyUsage(userId, getUtcDateKey(), 1000, 1)
+
+    expect(() => enforceDailyAiQuota(userId)).toThrowError(AppError)
+    try {
+      enforceDailyAiQuota(userId)
+    } catch (err) {
+      expect(err).toBeInstanceOf(AppError)
+      expect((err as AppError).statusCode).toBe(429)
+    }
+  })
+
+  it('allows users under the limit and isolates users from each other', () => {
+    settingsRepo.setSetting('ai_daily_token_limit', '1000')
+    const heavy = seedUser()
+    const fresh = seedUser()
+    aiUsageRepo.incrementDailyUsage(heavy, getUtcDateKey(), 999, 1)
+    expect(() => enforceDailyAiQuota(heavy)).not.toThrow()
+    expect(() => enforceDailyAiQuota(fresh)).not.toThrow()
+  })
+
+  it('only counts today’s usage', () => {
+    settingsRepo.setSetting('ai_daily_token_limit', '1000')
+    const userId = seedUser()
+    aiUsageRepo.incrementDailyUsage(userId, '2000-01-01', 999_999, 1)
+    expect(() => enforceDailyAiQuota(userId)).not.toThrow()
+  })
+})

backend/src/utils/aiQuota.ts

@@ -0,0 +1,51 @@
+import { getSetting } from '../repositories/settingsRepo.js'
+import { getDailyUsage, incrementDailyUsage } from '../repositories/aiUsageRepo.js'
+import { AppError } from '../middleware/error.js'
+
+export interface AiQuotaStatus {
+  allowed: boolean
+  limit: number | null
+  usedTokens: number
+  periodDate: string
+}
+
+export function getUtcDateKey(date = new Date()): string {
+  return date.toISOString().slice(0, 10)
+}
+
+export function getDailyTokenLimit(): number | null {
+  const raw = getSetting('ai_daily_token_limit') ?? ''
+  const parsed = Number(raw)
+  if (!Number.isFinite(parsed) || parsed <= 0) return null
+  return Math.floor(parsed)
+}
+
+export function checkDailyAiQuota(userId: number): AiQuotaStatus {
+  const periodDate = getUtcDateKey()
+  const limit = getDailyTokenLimit()
+  if (!limit) {
+    return { allowed: true, limit: null, usedTokens: 0, periodDate }
+  }
+
+  const usage = getDailyUsage(userId, periodDate)
+  return {
+    allowed: usage.tokensUsed < limit,
+    limit,
+    usedTokens: usage.tokensUsed,
+    periodDate,
+  }
+}
+
+export function recordDailyAiUsage(userId: number, periodDate: string, tokens: number): void {
+  incrementDailyUsage(userId, periodDate, tokens, 1)
+}
+
+/**
+ * Throws a 429 when the user has exhausted the admin-configured daily token
+ * limit. Call before every AI provider invocation; pair with recordDailyAiUsage.
+ */
+export function enforceDailyAiQuota(userId: number): void {
+  if (!checkDailyAiQuota(userId).allowed) {
+    throw new AppError(429, 'Daily AI usage limit reached. Please try again tomorrow.')
+  }
+}

backend/src/utils/aiTokens.ts

@@ -0,0 +1,29 @@
+export interface AiUsageResult<T> {
+  data: T
+  usageTokens: number
+}
+
+export function estimateTokensFromText(text: string): number {
+  if (!text) return 0
+  return Math.max(1, Math.ceil(text.length / 4))
+}
+
+export function estimateTokensFromMessages(messages: Array<{ content: string }>): number {
+  return messages.reduce((sum, msg) => sum + estimateTokensFromText(msg.content), 0)
+}
+
+// Conservative estimate when providers omit usage details.
+export function estimateTotalTokens(promptTokens: number, maxCompletionTokens: number): number {
+  const completionEstimate = Math.max(0, Math.round(maxCompletionTokens * 0.6))
+  return Math.max(1, promptTokens + completionEstimate)
+}
+
+export function resolveUsageTokens(
+  usage: { total_tokens?: number } | undefined,
+  estimate: number,
+): number {
+  if (usage && typeof usage.total_tokens === 'number' && Number.isFinite(usage.total_tokens)) {
+    return Math.max(0, Math.round(usage.total_tokens))
+  }
+  return estimate
+}

backend/src/utils/tokenBlacklist.ts

@@ -18,7 +18,8 @@ function initCache(): void {
     );
     CREATE INDEX IF NOT EXISTS idx_token_blacklist_expires ON token_blacklist(expires_at);
   `)
-  // Load recent blacklisted tokens into memory
+  // Purge rows that can never matter again, then load the rest into memory
+  db.prepare('DELETE FROM token_blacklist WHERE expires_at <= ?').run(Date.now())
   const rows = db.prepare('SELECT token_hash FROM token_blacklist WHERE expires_at > ?')
     .all(Date.now()) as { token_hash: string }[]
   for (const row of rows) {

backend/src/utils/tokens.test.ts

@@ -4,13 +4,14 @@ describe('tokens', () => {
   it('round-trips JWT payload', async () => {
     process.env.JWT_SECRET = 'test-secret-for-unit-tests-only'
     const { signToken, verifyToken } = await import('./tokens')
-    const payload = { userId: 1, email: 'a@b.com', displayName: 'Test', role: 'user' as const }
+    const payload = { userId: 1, email: 'a@b.com', displayName: 'Test', role: 'user' as const, tv: 3 }
     const token = signToken(payload)
     const decoded = verifyToken(token)
     expect(decoded.userId).toBe(1)
     expect(decoded.email).toBe('a@b.com')
     expect(decoded.displayName).toBe('Test')
     expect(decoded.role).toBe('user')
+    expect(decoded.tv).toBe(3)
   })
 
   it('throws on invalid token', async () => {
@@ -22,7 +23,7 @@ describe('tokens', () => {
   it('throws on tampered token', async () => {
     process.env.JWT_SECRET = 'test-secret-for-unit-tests-only'
     const { signToken, verifyToken } = await import('./tokens')
-    const payload = { userId: 1, email: 'a@b.com', displayName: 'Test', role: 'user' as const }
+    const payload = { userId: 1, email: 'a@b.com', displayName: 'Test', role: 'user' as const, tv: 0 }
     const token = signToken(payload)
     const tampered = token.slice(0, -5) + 'xxxxx'
     expect(() => verifyToken(tampered)).toThrow()

backend/src/utils/tokens.ts

@@ -7,14 +7,19 @@ export interface JwtPayload {
   email: string
   displayName: string
   role: 'user' | 'admin'
+  /** Token version — must match the user's current token_version or the token is rejected */
+  tv: number
 }
 
 export function signToken(payload: JwtPayload): string {
-  return jwt.sign(payload, config.jwtSecret, { expiresIn: '24h' })
+  return jwt.sign(payload, config.jwtSecret, { expiresIn: config.jwtExpiresIn } as jwt.SignOptions)
 }
 
-export function verifyToken(token: string): JwtPayload {
-  return jwt.verify(token, config.jwtSecret) as JwtPayload
+/** Verified JWT body: our claims plus the registered exp/iat timestamps. */
+export type VerifiedToken = JwtPayload & { exp?: number; iat?: number }
+
+export function verifyToken(token: string): VerifiedToken {
+  return jwt.verify(token, config.jwtSecret) as VerifiedToken
 }
 
 export function generateVerificationToken(): string {

backend/src/validators/aiSchemas.test.ts

@@ -0,0 +1,23 @@
+import { describe, it, expect } from 'vitest'
+import { hintSchema, MAX_HINT_QUESTION_CHARS } from './aiSchemas.js'
+
+describe('hintSchema', () => {
+  it('accepts a normal hint request', () => {
+    const result = hintSchema.safeParse({
+      question: { type: 'short-answer', prompt: 'What is 2+2?' },
+      language: 'en',
+    })
+    expect(result.success).toBe(true)
+  })
+
+  it(`rejects questions whose JSON exceeds ${MAX_HINT_QUESTION_CHARS} chars`, () => {
+    const result = hintSchema.safeParse({
+      question: { prompt: 'x'.repeat(MAX_HINT_QUESTION_CHARS + 1) },
+      language: 'en',
+    })
+    expect(result.success).toBe(false)
+    if (!result.success) {
+      expect(JSON.stringify(result.error.issues)).toContain('too large')
+    }
+  })
+})

backend/src/validators/aiSchemas.ts

@@ -0,0 +1,25 @@
+import { z } from 'zod'
+
+export const MAX_HINT_QUESTION_CHARS = 8000
+
+function serializedSize(value: unknown): number {
+  if (value === undefined || value === null) return 0
+  return JSON.stringify(value).length
+}
+
+export const hintSchema = z
+  .object({
+    question: z.record(z.unknown()),
+    language: z.string().min(1).max(20),
+  })
+  .superRefine((val, ctx) => {
+    if (serializedSize(val.question) > MAX_HINT_QUESTION_CHARS) {
+      ctx.addIssue({
+        code: z.ZodIssueCode.custom,
+        message: 'Question is too large for AI hints',
+        path: ['question'],
+      })
+    }
+  })
+
+export type HintRequestBody = z.infer<typeof hintSchema>

backend/src/validators/gradeSchemas.test.ts

@@ -0,0 +1,65 @@
+import { describe, it, expect } from 'vitest'
+import {
+  gradeRequestSchema,
+  MAX_GRADE_QUESTION_CHARS,
+  MAX_GRADE_ANSWER_CHARS,
+} from './gradeSchemas.js'
+
+const validBase = {
+  question: { prompt: 'Explain photosynthesis' },
+  answer: 'Plants convert light into chemical energy',
+  language: 'en',
+}
+
+describe('gradeRequestSchema', () => {
+  it('accepts a well-formed grading request', () => {
+    const result = gradeRequestSchema.safeParse({ type: 'essay', ...validBase })
+    expect(result.success).toBe(true)
+  })
+
+  it(`rejects questions whose JSON exceeds ${MAX_GRADE_QUESTION_CHARS} chars`, () => {
+    const result = gradeRequestSchema.safeParse({
+      type: 'essay',
+      question: { prompt: 'x'.repeat(MAX_GRADE_QUESTION_CHARS + 1) },
+      answer: 'irrelevant',
+      language: 'en',
+    })
+    expect(result.success).toBe(false)
+    if (!result.success) {
+      expect(JSON.stringify(result.error.issues)).toContain('too large')
+    }
+  })
+
+  it(`rejects answers whose JSON exceeds ${MAX_GRADE_ANSWER_CHARS} chars`, () => {
+    const result = gradeRequestSchema.safeParse({
+      type: 'essay',
+      question: { prompt: 'small' },
+      answer: 'y'.repeat(MAX_GRADE_ANSWER_CHARS + 1),
+      language: 'en',
+    })
+    expect(result.success).toBe(false)
+    if (!result.success) {
+      expect(JSON.stringify(result.error.issues)).toContain('too large')
+    }
+  })
+
+  it('rejects unknown question types', () => {
+    const result = gradeRequestSchema.safeParse({
+      type: 'flashcard',
+      question: { prompt: 'hi' },
+      answer: 'yo',
+      language: 'en',
+    })
+    expect(result.success).toBe(false)
+  })
+
+  it('bounds the language field', () => {
+    const result = gradeRequestSchema.safeParse({
+      type: 'essay',
+      question: { prompt: 'hi' },
+      answer: 'yo',
+      language: 'l'.repeat(500),
+    })
+    expect(result.success).toBe(false)
+  })
+})

backend/src/validators/gradeSchemas.ts

@@ -0,0 +1,37 @@
+import { z } from 'zod'
+
+/** Serialized size caps: the grading prompt is built from client-supplied
+ * question/answer objects, so these bound what can be billed per request. */
+export const MAX_GRADE_QUESTION_CHARS = 8000
+export const MAX_GRADE_ANSWER_CHARS = 4000
+
+function serializedSize(value: unknown): number {
+  if (value === undefined || value === null) return 0
+  return JSON.stringify(value).length
+}
+
+const gradeRequestBase = z.object({
+  type: z.enum(['essay', 'short-answer', 'translation', 'math', 'ordering', 'match']),
+  question: z.record(z.unknown()),
+  answer: z.unknown(),
+  language: z.string().min(1).max(30),
+})
+
+export const gradeRequestSchema = gradeRequestBase.superRefine((val, ctx) => {
+  if (serializedSize(val.question) > MAX_GRADE_QUESTION_CHARS) {
+    ctx.addIssue({
+      code: z.ZodIssueCode.custom,
+      message: 'Question is too large for AI grading',
+      path: ['question'],
+    })
+  }
+  if (serializedSize(val.answer) > MAX_GRADE_ANSWER_CHARS) {
+    ctx.addIssue({
+      code: z.ZodIssueCode.custom,
+      message: 'Answer is too large for AI grading',
+      path: ['answer'],
+    })
+  }
+})
+
+export type GradeRequestBody = z.infer<typeof gradeRequestSchema>

backend/src/validators/resultSchemas.test.ts

@@ -68,7 +68,7 @@ describe('submitResultSchema', () => {
     expect(result.success).toBe(true)
   })
 
-  it('accepts negative score_points because schema allows any number', () => {
+  it('rejects negative score_points (client-supplied scores are bounded)', () => {
     const result = submitResultSchema.safeParse({
       title: 'My Exam',
       score_points: -1,
@@ -86,7 +86,25 @@ describe('submitResultSchema', () => {
       },
       exam: { title: 'My Exam', questions: [] },
     })
-    expect(result.success).toBe(true)
+    expect(result.success).toBe(false)
+  })
+
+  it('rejects non-integer counts and absurd magnitudes', () => {
+    const base = {
+      title: 'My Exam',
+      score_points: 8,
+      total_points: 10,
+      correct_count: 8,
+      graded_count: 10,
+      elapsed_ms: 120000,
+      state: { currentIdx: 0, answers: {}, flags: {}, notes: '', startedAt: Date.now(), feedbackMode: 'end' },
+      exam: { title: 'My Exam', questions: [] },
+    }
+    expect(submitResultSchema.safeParse({ ...base, correct_count: 1.5 }).success).toBe(false)
+    expect(submitResultSchema.safeParse({ ...base, score_points: 1e12 }).success).toBe(false)
+    expect(submitResultSchema.safeParse({ ...base, elapsed_ms: -5 }).success).toBe(false)
+    expect(submitResultSchema.safeParse({ ...base, exam_id: -3 }).success).toBe(false)
+    expect(submitResultSchema.safeParse({ ...base, title: 't'.repeat(301) }).success).toBe(false)
   })
 
   it('accepts immediate feedback mode', () => {

backend/src/validators/resultSchemas.ts

@@ -1,14 +1,16 @@
 import { z } from 'zod'
 
+// Scores/counts arrive from the client, so they are bounded to keep forged
+// garbage out of analytics while accepting every value honest clients send.
 export const submitResultSchema = z.object({
-  exam_id: z.number().nullable().optional(),
-  title: z.string().min(1),
-  score_points: z.number(),
-  total_points: z.number(),
-  correct_count: z.number(),
-  graded_count: z.number(),
-  passing_score: z.number().optional(),
-  elapsed_ms: z.number(),
+  exam_id: z.number().int().positive().nullable().optional(),
+  title: z.string().min(1).max(300),
+  score_points: z.number().finite().min(0).max(1e9),
+  total_points: z.number().finite().min(0).max(1e9),
+  correct_count: z.number().int().min(0).max(1e6),
+  graded_count: z.number().int().min(0).max(1e6),
+  passing_score: z.number().finite().min(0).max(1e9).optional(),
+  elapsed_ms: z.number().int().min(0).max(2_147_483_647),
   state: z.record(z.unknown()),
   exam: z.record(z.unknown()),
 })

docs/superpowers/plans/2026-08-21-security-audit-fixes.md

@@ -0,0 +1,104 @@
+# Security Audit Fixes Implementation Plan
+
+> **For agentic workers:** REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development (recommended) or superpowers:executing-plans to implement this plan task-by-task. Steps use checkbox (`- [ ]`) syntax for tracking.
+
+**Goal:** Fix all vulnerabilities confirmed by the 2026-08-21 full-codebase security audit (5 confirmed ≥8/10 confidence + 6 sub-threshold verified findings).
+
+**Architecture:** Three clusters. (A) Session security: JWTs gain a `tv` (token version) claim; `requireAuth` revalidates the user against SQLite on every request (deleted accounts, demoted roles, password-rotation revocation); logout blacklists until real `exp`. (B) AI cost control: wire the existing-but-dead quota helpers into every provider call path and cap attacker-controlled prompt sizes. (C) Bootstrap & hygiene: make the setup wizard the only admin bootstrap, stop register-time auto-admin, sanitize admin user listings, bound result schemas, enforce view-only share mode server-side, pin SSH host keys in CI.
+
+**Tech Stack:** Express 5, better-sqlite3 (sync), jsonwebtoken 9, zod 3, vitest 4, Gitea Actions.
+
+**Spec:** Security audit report delivered in this session (2026-08-21). Findings referenced below as Vuln N / sub-threshold N.
+
+## Global Constraints
+
+- Do not alter lines containing redacted numeric literals in `userRepo.ts` (`storageQuotaBytes ?? …`) and `migrations.ts` (`storage_quota_bytes … DEFAULT`) — edit around them.
+- Keep HTTP response shapes of AI endpoints unchanged (`{ data, usageTokens }` payloads stay) so the frontend needs no changes.
+- Tests run with `cd backend && npx vitest run`; vitest.setup stubs `JWT_SECRET`, `DB_PATH=:memory:`; `getDb()` runs full migrations on first use.
+- No git commits — user has not requested them; leave changes in working tree.
+- Existing deployments upgrade transparently; all users are logged out once by the new `tv` claim (accepted, noted in final report).
+
+---
+
+### Task 1: Token versioning + DB revalidation (Vuln 3, Vuln 4, sub-threshold 1)
+
+**Files:**
+- Modify: `backend/src/db/migrations.ts` (add column)
+- Modify: `backend/src/utils/tokens.ts` (JwtPayload.tv)
+- Modify: `backend/src/repositories/userRepo.ts` (token_version plumbing)
+- Modify: `backend/src/middleware/auth.ts` (revalidation)
+- Modify: `backend/src/services/authService.ts` (sign with tv, bump on password events)
+- Modify: `backend/src/routes/setup.ts` (sign with tv)
+- Modify: `backend/src/routes/auth.ts` (logout uses decoded exp)
+- Modify: `backend/src/utils/tokenBlacklist.ts` (purge expired rows at init)
+- Test: `backend/src/utils/tokens.test.ts` (update payload fixtures), `backend/src/middleware/auth.test.ts` (new)
+
+**Interfaces:**
+- Produces: `JwtPayload { userId, email, displayName, role, tv }`; `DbUser.token_version: number`; `UpdateUserData.tokenVersion?: number`.
+
+- [ ] **Step 1: Write failing tests** (`auth.test.ts`): valid token passes and `req.user.role` comes from DB; deleted user → 401; tv mismatch → 401. Update `tokens.test.ts` payload fixtures to include `tv: 0` (type error until implemented = failing).
+- [ ] **Step 2: Run** `npx vitest run src/middleware/auth.test.ts src/utils/tokens.test.ts` → FAIL (missing tv / column).
+- [ ] **Step 3: Implement** per code in execution notes: migration guard block; `token_version INTEGER NOT NULL DEFAULT 0`; JwtPayload gains required `tv`; requireAuth loads user via `getUserById`, 401 on missing user, 401 on `user.token_version !== payload.tv`, rebuilds `req.user` from the DB row; changePassword/resetPassword bump tokenVersion; logout blacklists `(decoded.exp ?? now+86400)*1000`; initCache purges expired rows before loading.
+- [ ] **Step 4: Run** → PASS.
+- [ ] **Step 5: Full suite** `npx vitest run` → PASS.
+
+### Task 2: Setup-gated bootstrap, no register auto-admin, enumeration-safe register, last-admin guard (sub-threshold 2, 3, 4)
+
+**Files:**
+- Modify: `backend/src/routes/setup.ts` (status + POST gate on countAdmins)
+- Modify: `backend/src/routes/auth.ts` (drop isFirstUser; last-admin self-delete guard)
+- Modify: `backend/src/services/authService.ts` (register signature, role always 'user', duplicate → generic success after timing-equalized hash)
+- Modify: `backend/src/db/migrations.ts` (remove auto-promote block)
+- Modify: `backend/src/repositories/userRepo.ts` (remove dead promoteFirstUserToAdmin)
+- Test: `backend/src/services/authService.test.ts` (new)
+
+- [ ] **Step 1: Failing tests**: duplicate-email register resolves `{ message }` with no token; fresh register returns token with role 'user'; both take ~equal time (hash-before-check asserted structurally, not by timing).
+- [ ] **Step 2: Run** → FAIL.
+- [ ] **Step 3: Implement**: setup status/gate switch to `countAdmins() > 0`; register drops isFirstUser param, hashes password before duplicate check, returns `{ message: 'Check your inbox…' }` on duplicates; `DELETE /api/auth/me` refuses when `role==='admin' && countAdmins()<=1`; migrations/userRepo promotion code deleted.
+- [ ] **Step 4: Run** → PASS. **Step 5: Full suite** → PASS.
+
+### Task 3: AI quota enforcement + prompt size caps (Vuln 1, Vuln 2)
+
+**Files:**
+- Modify: `backend/src/utils/aiQuota.ts` (add enforceDailyAiQuota throwing AppError 429)
+- Create: `backend/src/validators/gradeSchemas.ts` (schema with serialized-size superRefine caps), `backend/src/validators/aiSchemas.ts` (hintSchema moved + cap)
+- Modify: `backend/src/routes/ai.ts`, `backend/src/routes/grade.ts`, `backend/src/routes/results.ts` (enforce before provider call; recordDailyAiUsage after, using returned usageTokens)
+- Test: `backend/src/utils/aiQuota.test.ts`, `backend/src/validators/gradeSchemas.test.ts`
+
+**Interfaces:**
+- Consumes: `recordDailyAiUsage(userId, getUtcDateKey(), tokens)`; services' existing `AiUsageResult.usageTokens`.
+- Produces: `enforceDailyAiQuota(userId): void` (throws `AppError(429)`).
+
+- [ ] **Step 1: Failing tests**: quota throws 429 when used ≥ limit; passes under limit; passes when limit unset ("0"/absent → null → unlimited). Grade schema rejects question JSON > 8000 chars / answer > 4000 chars.
+- [ ] **Step 2: Run** → FAIL. **Step 3: Implement. Step 4: Run → PASS. Step 5: Full suite → PASS.**
+
+### Task 4: Admin user DTO + result schema bounds (sub-threshold 5, 6)
+
+**Files:**
+- Modify: `backend/src/repositories/userRepo.ts` (`SafeUser`, explicit SELECT columns in listUsers)
+- Modify: `backend/src/validators/resultSchemas.ts` (finite/int/min/max bounds, title ≤300)
+- Test: `backend/src/validators/resultSchemas.test.ts`, repo test for sanitized listing
+
+- [ ] **Step 1: Failing tests**: listUsers never includes password_hash/verify_token/reset_token/reset_expires keys; schema rejects negative counts, non-integers, huge floats, oversized titles.
+- [ ] **Step 2–5:** implement → PASS → full suite PASS.
+
+### Task 5: View-only share clone block (Vuln 5)
+
+**Files:**
+- Modify: `backend/src/routes/share.ts`
+- Test: `backend/src/routes/share.test.ts`
+
+- [ ] Export pure `canClone(shareMode?: string | null): boolean` ('view' → false; 'clone'/null/undefined → true). Failing test first, then guard `if (!canClone(source.share_mode)) throw new AppError(403, 'This exam is shared as view-only and cannot be saved')` before `cloneExam`. PASS + full suite.
+
+### Task 6: CI SSH host-key pinning (sub-threshold 7)
+
+**Files:** Modify `.gitea/workflows/deploy.yml`
+
+- [ ] Replace keyscan step: write `${{ vars.SSH_HOST_PUBLIC_KEY }}` via env-indirection into known_hosts; hard-fail with setup instructions when unset. Validate YAML parses.
+
+### Task 7: Verification
+
+- [ ] `cd backend && npx tsc --noEmit && npx vitest run` — all green.
+- [ ] `cd frontend && npm run build` (or tsc -b) — typecheck green (no frontend changes expected).
+- [ ] Ultracode adversarial review workflow over the full diff; fix anything CONFIRMED.
+- [ ] Final report mapping each finding → fix → evidence.

frontend/src/App.tsx

@@ -96,7 +96,7 @@ function AppInner() {
 
   // Bridge: MyResults stores review data in localStorage; load it on /review/:slug
   useEffect(() => {
-    if (pathname.startsWith("/review/") && !exam) {
+    if (pathname.startsWith("/review/")) {
       const reviewExam = localStorage.getItem('brainwave.review.exam')
       const reviewState = localStorage.getItem('brainwave.review.state')
       const reviewResultIdRaw = localStorage.getItem('brainwave.review.resultId')
@@ -118,7 +118,7 @@ function AppInner() {
         }
       }
     }
-  }, [pathname, exam]);
+  }, [pathname]);
 
   const setExamStateStrict = useCallback<React.Dispatch<React.SetStateAction<ExamState>>>(
     (nextState) => {

frontend/src/api/authApi.ts

@@ -56,3 +56,7 @@ export function resetPassword(data: { token: string; newPassword: string }): Pro
 export function deleteAccount(): Promise<{ success: boolean }> {
   return apiFetch('/api/auth/me', { method: 'DELETE' })
 }
+
+export function logout(): Promise<void> {
+  return apiFetch('/api/auth/logout', { method: 'POST' })
+}

frontend/src/components/MyResults.tsx

@@ -158,7 +158,7 @@ export default function MyResults({ onLoadExam }: Props) {
                     {retakingId === r.id ? t('common.loading') : t('results.retakeExam')}
                   </button>
                   <button className="btn btn-sm" onClick={() => void reviewResult(r)}>
-                    {t('common.edit')}
+                    {t('results.review')}
                   </button>
                   {deleteConfirm === r.id ? (
                     <div className="workspace-delete-confirm">

frontend/src/components/Overview.tsx

@@ -29,7 +29,7 @@ export default function Overview({ examCount, resultCount, recentResults, onLoad
   useEffect(() => {
     resultApi.getScoreTrends()
       .then((data) => setTrends(data))
-      .catch(() => {/* ignore */})
+      .catch(() => {/* ignore */ })
       .finally(() => setTrendsLoading(false))
   }, [])
 

frontend/src/contexts/AuthContext.tsx

@@ -22,7 +22,7 @@ interface AuthContextValue {
   setUser: (user: User | null) => void
   login: (email: string, password: string) => Promise<void>
   register: (email: string, password: string, displayName: string) => Promise<string>
-  logout: () => void
+  logout: () => Promise<void>
   refreshUser: () => Promise<void>
 }
 
@@ -87,7 +87,12 @@ export function AuthProvider({ children }: { children: ReactNode }) {
     return 'Registration successful! Please check your email to verify your account.'
   }, [])
 
-  const logout = useCallback(() => {
+  const logout = useCallback(async () => {
+    try {
+      await authApi.logout()
+    } catch {
+      // ignore errors — we still want to clear local state
+    }
     clearToken()
     setUser(null)
   }, [])

frontend/src/utils/api.ts

@@ -16,8 +16,25 @@ export function clearToken(): void {
   localStorage.removeItem('brainwave.auth.token')
 }
 
+function isTokenExpired(token: string): boolean {
+  try {
+    const payload = JSON.parse(atob(token.split('.')[1] ?? ''))
+    const exp = payload.exp
+    if (typeof exp !== 'number') return false
+    return Date.now() >= exp * 1000
+  } catch {
+    return true
+  }
+}
+
 export function isAuthenticated(): boolean {
-  return !!getToken()
+  const token = getToken()
+  if (!token) return false
+  if (isTokenExpired(token)) {
+    clearToken()
+    return false
+  }
+  return true
 }
 
 export async function apiFetch<T = unknown>(

frontend/src/utils/instructions.ts

@@ -219,15 +219,216 @@ QUESTION TYPES
      "answer": ["e1", "e2", "e3", "e4"]
    }
 
+9. FILL-IN-THE-BLANKS ("fill-in-the-blanks")
+   Student completes blanks embedded in a text passage.
+
+   Required fields:
+     "textSegments": ["Before blank", " between blanks", " after blank"] — Array of text strings to interleave with blanks. Must be blanks.length + 1.
+     "blanks": [
+       { "id": "b1", "acceptedAnswers": ["correct word", "alt word"] },
+       ...
+     ]
+
+   Optional per-blank fields:
+     "acceptedForms": ["alt1"] — Additional accepted forms
+     "caseSensitive": true|false (default: false)
+     "ignorePunctuation": true|false (default: false)
+     "ignoreAccents": true|false (default: false)
+
+   Example:
+   {
+     "id": "q9",
+     "type": "fill-in-the-blanks",
+     "prompt": "Fill in the missing words.",
+     "textSegments": ["The capital of France is ", ", and the capital of Japan is ", "."],
+     "blanks": [
+       { "id": "b1", "acceptedAnswers": ["Paris"], "caseSensitive": false },
+       { "id": "b2", "acceptedAnswers": ["Tokyo"], "caseSensitive": false }
+     ]
+   }
+
+10. TRUE / FALSE ("true-false")
+    Student answers a statement with true or false.
+
+    Required fields:
+      "answer": true or false
+
+    Example:
+    {
+      "id": "q10",
+      "type": "true-false",
+      "prompt": "The Earth is the third planet from the Sun.",
+      "answer": true
+    }
+
+11. CODE SUBMISSION ("code-submission")
+    Student writes code in a specific programming language.
+
+    Required fields:
+      "codeConfig": { "language": "python" } — Programming language identifier
+
+    Optional fields:
+      "codeConfig": { "language": "python", "starterCode": "def hello():\\n    pass" } — Initial code shown in editor
+      "rubric": ["criterion 1", "criterion 2"] — Criteria for grading
+
+    Example:
+    {
+      "id": "q11",
+      "type": "code-submission",
+      "prompt": "Write a function that returns the factorial of n.",
+      "points": 5,
+      "codeConfig": { "language": "python", "starterCode": "def factorial(n):\\n    pass" },
+      "rubric": [
+        "Handles base case (0! = 1)",
+        "Uses recursion or iteration correctly",
+        "Returns correct result for positive integers"
+      ]
+    }
+
+12. DROPDOWN COMPLETION ("dropdown-completion")
+    Student selects from dropdown menus embedded in a text passage.
+
+    Required fields:
+      "textSegments": ["Before dropdown", " between dropdowns", " after dropdown"] — Must be dropdowns.length + 1.
+      "dropdowns": [
+        {
+          "id": "d1",
+          "options": [{ "id": "a", "text": "Option A" }, { "id": "b", "text": "Option B" }],
+          "correctOptionId": "a"
+        }
+      ]
+
+    Example:
+    {
+      "id": "q12",
+      "type": "dropdown-completion",
+      "prompt": "Choose the correct words.",
+      "textSegments": ["Water boils at ", " degrees Celsius at sea level, and freezes at ", "."],
+      "dropdowns": [
+        {
+          "id": "d1",
+          "options": [
+            { "id": "a", "text": "100" },
+            { "id": "b", "text": "90" },
+            { "id": "c", "text": "110" }
+          ],
+          "correctOptionId": "a"
+        },
+        {
+          "id": "d2",
+          "options": [
+            { "id": "a", "text": "0" },
+            { "id": "b", "text": "-10" },
+            { "id": "c", "text": "10" }
+          ],
+          "correctOptionId": "a"
+        }
+      ]
+    }
+
+13. NUMERIC RANGE ("numeric-range")
+    Student enters a numeric answer within an acceptable tolerance.
+
+    Required fields:
+      "numericConfig": { "answer": 42, "tolerance": 0.5 } — Correct value and allowed deviation
+
+    Optional fields:
+      "numericConfig": { "answer": 42, "tolerance": 0.5, "min": 0, "max": 100 } — Bounds for validation
+
+    Example:
+    {
+      "id": "q13",
+      "type": "numeric-range",
+      "prompt": "What is the approximate speed of sound in air at 20°C (in m/s)?",
+      "points": 2,
+      "numericConfig": { "answer": 343, "tolerance": 5, "min": 300, "max": 400 }
+    }
+
+14. DICTATION ("dictation")
+    Student transcribes audio they listen to.
+
+    Required fields:
+      "audio": { "src": "https://example.com/audio.mp3" } — URL to the audio file
+      "answer": "string" — Correct transcription
+
+    Optional fields:
+      "acceptedForms": ["alt transcription 1"] — Other accepted forms
+      "caseSensitive": true|false (default: false)
+      "ignorePunctuation": true|false (default: false)
+      "ignoreAccents": true|false (default: false)
+
+    Example:
+    {
+      "id": "q14",
+      "type": "dictation",
+      "prompt": "Listen to the audio and type what you hear.",
+      "audio": { "src": "https://example.com/dictation.mp3" },
+      "answer": "The quick brown fox jumps over the lazy dog.",
+      "caseSensitive": false,
+      "ignorePunctuation": true
+    }
+
+15. GRAMMAR CORRECTION ("grammar-correction")
+    Student corrects errors in a provided sentence.
+
+    Required fields:
+      "textToCorrect": "string" — The sentence containing errors
+      "answer": "string" — The corrected sentence
+
+    Optional fields:
+      "acceptedForms": ["alt correction 1"] — Other accepted corrected forms
+      "caseSensitive": true|false (default: false)
+      "ignorePunctuation": true|false (default: false)
+
+    Example:
+    {
+      "id": "q15",
+      "type": "grammar-correction",
+      "prompt": "Correct the grammar in the following sentence.",
+      "textToCorrect": "She don't like apples.",
+      "answer": "She doesn't like apples.",
+      "caseSensitive": false
+    }
+
+16. FLASHCARD ("flashcard")
+    Self-study card with front and back. Not graded — student self-assesses.
+
+    Required fields:
+      "answer": "string" — The back of the card (translation, definition, etc.)
+
+    Optional fields:
+      "explanation": "string" — Extra info shown after reveal
+
+    Example:
+    {
+      "id": "q16",
+      "type": "flashcard",
+      "prompt": "Bonjour",
+      "answer": "Hello (French)",
+      "explanation": "Informal greeting used throughout the day."
+    }
+
+────────────────────────────────────
+LANGUAGE GUIDELINES
+────────────────────────────────────
+When writing user-facing text (prompts, choices, explanations, rubric items, hints):
+  - Write ALL user-facing text in the language the user is asking for (their native/request language).
+  - Do NOT default to the subject language for explanations, prompts, or rubric items.
+
+Examples:
+  - If the user asks for a "French vocabulary test" in English, write prompts and explanations in ENGLISH. Only the target vocabulary (the word being tested) should be in French.
+  - If the user asks for a "biology exam" in Dutch, write everything in DUTCH, even if the source material is in English.
+  - Explanations should always be in the user's request language so they can understand why an answer is correct or incorrect.
+
 ────────────────────────────────────
 LATEX SUPPORT
 ────────────────────────────────────
 Use LaTeX math in prompts, choices, and explanations:
   - Inline math:  $x^2 + y^2 = z^2$
-  - Display math: $$\\\\int_0^1 x^2 \\\\, dx = \\\\frac{1}{3}$$
+  - Display math: $$\\int_0^1 x^2 \\, dx = \\frac{1}{3}$$
 
 Remember to double-escape backslashes in JSON strings:
-  "prompt": "Evaluate $\\\\frac{d}{dx} x^2$"
+  "prompt": "Evaluate $\\frac{d}{dx} x^2$"
 
 ────────────────────────────────────
 MEDIA ATTACHMENTS
@@ -304,10 +505,29 @@ When asking your LLM to create an exam, include:
   4. Which question types to use
   5. Desired difficulty level
   6. Whether to include a time limit
+  7. The language you want all user-facing text written in
 
 Example prompt: "Using the attached format guide, create a 10-question exam on
 World War II. Use a mix of multiple-choice, short-answer, and ordering questions.
-Set a 20-minute time limit. Include explanations for each answer."
+Set a 20-minute time limit. Write everything in English and include explanations
+for each answer."
+
+────────────────────────────────────
+CLARIFYING QUESTIONS
+────────────────────────────────────
+Before generating the exam JSON, you MAY ask 1–3 short clarifying questions if
+anything is ambiguous or would significantly improve the quality of the output.
+Only ask questions when the user's request is genuinely unclear — do not delay
+trivial requests.
+
+Good clarifying questions include:
+  - "What is the target difficulty level (beginner, intermediate, advanced)?"
+  - "Who is the intended audience (age group, class level, professional field)?"
+  - "Should explanations be in [user's language] even if the subject is a foreign language?"
+  - "Do you want a mix of question types, or focus on one type?"
+  - "Should I include a time limit or passing score?"
+
+Once the user answers, generate the full exam JSON in a single response.
 `
 
   const blob = new Blob([content], { type: 'text/plain' })

node_modules/.vite/vitest/da39a3ee5e6b4b0d3255bfef95601890afd80709/results.json

@@ -1 +1 @@
-{"version":"4.1.5","results":[[":frontend/src/utils/grading.test.ts",{"duration":0,"failed":true}],[":backend/dist/validators/resultSchemas.test.js",{"duration":0,"failed":true}],[":backend/src/validators/authSchemas.test.ts",{"duration":0,"failed":true}],[":backend/src/validators/resultSchemas.test.ts",{"duration":0,"failed":true}],[":backend/dist/validators/authSchemas.test.js",{"duration":0,"failed":true}],[":frontend/src/utils/storage.test.ts",{"duration":0,"failed":true}],[":backend/dist/validators/examSchemas.test.js",{"duration":0,"failed":true}],[":backend/dist/config.test.js",{"duration":0,"failed":true}],[":backend/src/validators/adminSchemas.test.ts",{"duration":0,"failed":true}],[":frontend/src/utils/latex.test.ts",{"duration":0,"failed":true}],[":backend/dist/validators/adminSchemas.test.js",{"duration":0,"failed":true}],[":backend/src/config.test.ts",{"duration":0,"failed":true}],[":backend/src/validators/examSchemas.test.ts",{"duration":0,"failed":true}],[":backend/dist/utils/tokens.test.js",{"duration":0,"failed":true}],[":frontend/src/utils/validation.test.ts",{"duration":0,"failed":true}],[":backend/src/utils/tokens.test.ts",{"duration":0,"failed":true}],[":frontend/src/utils/slug.test.ts",{"duration":0,"failed":true}],[":backend/src/utils/asyncHandler.test.ts",{"duration":0,"failed":true}],[":backend/src/validators/setupSchemas.test.ts",{"duration":0,"failed":true}],[":backend/dist/validators/setupSchemas.test.js",{"duration":0,"failed":true}],[":backend/dist/middleware/error.test.js",{"duration":0,"failed":true}],[":backend/dist/utils/asyncHandler.test.js",{"duration":0,"failed":true}],[":frontend/src/utils/formatting.test.ts",{"duration":0,"failed":true}],[":backend/src/middleware/error.test.ts",{"duration":0,"failed":true}],[":frontend/src/utils/api.test.ts",{"duration":0,"failed":true}],[":backend/src/repositories/storageRepo.test.ts",{"duration":0,"failed":true}],[":backend/dist/repositories/storageRepo.test.js",{"duration":0,"failed":true}]]}
+{"version":"4.1.5","results":[[":frontend/src/utils/grading.test.ts",{"duration":9.265338999999983,"failed":false}],[":backend/dist/validators/resultSchemas.test.js",{"duration":0,"failed":true}],[":backend/src/validators/authSchemas.test.ts",{"duration":22.575676000000044,"failed":false}],[":backend/src/validators/resultSchemas.test.ts",{"duration":9.748771000000033,"failed":false}],[":backend/dist/validators/authSchemas.test.js",{"duration":0,"failed":true}],[":frontend/src/utils/storage.test.ts",{"duration":6.310062000000016,"failed":false}],[":backend/dist/validators/examSchemas.test.js",{"duration":0,"failed":true}],[":backend/dist/config.test.js",{"duration":0,"failed":true}],[":backend/src/validators/adminSchemas.test.ts",{"duration":33.639384000000064,"failed":false}],[":frontend/src/utils/latex.test.ts",{"duration":0,"failed":true}],[":backend/dist/validators/adminSchemas.test.js",{"duration":0,"failed":true}],[":backend/src/config.test.ts",{"duration":14.69092599999999,"failed":false}],[":backend/src/validators/examSchemas.test.ts",{"duration":33.61004700000001,"failed":false}],[":backend/dist/utils/tokens.test.js",{"duration":0,"failed":true}],[":frontend/src/utils/validation.test.ts",{"duration":11.680594999999983,"failed":false}],[":backend/src/utils/tokens.test.ts",{"duration":44.34940499999999,"failed":false}],[":frontend/src/utils/slug.test.ts",{"duration":5.085611999999969,"failed":false}],[":backend/src/utils/asyncHandler.test.ts",{"duration":5.737424999999973,"failed":false}],[":backend/src/validators/setupSchemas.test.ts",{"duration":28.528040000000033,"failed":false}],[":backend/dist/validators/setupSchemas.test.js",{"duration":0,"failed":true}],[":backend/dist/middleware/error.test.js",{"duration":0,"failed":true}],[":backend/dist/utils/asyncHandler.test.js",{"duration":0,"failed":true}],[":frontend/src/utils/formatting.test.ts",{"duration":4.583577999999989,"failed":false}],[":backend/src/middleware/error.test.ts",{"duration":8.906761999999958,"failed":false}],[":frontend/src/utils/api.test.ts",{"duration":9.23972999999998,"failed":false}],[":backend/src/repositories/storageRepo.test.ts",{"duration":23.65549999999996,"failed":false}],[":backend/dist/repositories/storageRepo.test.js",{"duration":0,"failed":true}],[":backend/src/validators/gradeSchemas.test.ts",{"duration":16.57176800000002,"failed":false}],[":backend/src/utils/aiQuota.test.ts",{"duration":0,"failed":true}],[":backend/src/validators/collectionSchemas.test.ts",{"duration":15.043968000000007,"failed":false}],[":backend/src/validators/aiSchemas.test.ts",{"duration":14.30532999999997,"failed":false}],[":backend/src/services/authService.test.ts",{"duration":0,"failed":true}],[":backend/src/middleware/auth.test.ts",{"duration":0,"failed":true}]]}