---
name: brainstorm-ideation-example
description: "Complete TypeScript/Bun example of brainstorming authentication implementation"
see_also:
  - sp:brainstorm
  - sp:source-driven-development
  - spur agent run
---

# Brainstorm: User Authentication for API (TypeScript/Bun)

**Date:** 2026-03-25
**Input:** Issue description
**Runtime:** Bun + Hono

## Overview

The current API lacks authentication, exposing all endpoints to unauthorized access. This poses security risks for production deployment. Need to implement authentication while maintaining API simplicity and performance.

**Current state:**
- Public API with no access control
- Hono framework already in use (Bun-compatible)
- JWT tokens preferred for stateless auth
- Need both user registration and login endpoints

## Approaches

### Approach 1: JWT with jose ⭐ Recommended

**Description:** Use the `jose` library for JWT handling with Hono's middleware system. Provides stateless authentication with standard OAuth2-compatible headers.

**Trade-offs:**
- **Pros:**
  - Native Bun/Node.js compatibility
  - JWT stateless - scales horizontally without session storage
  - Standard OAuth2 Bearer token format
  - jose supports Edge Runtime and Bun
  - TypeScript-first with full type safety
- **Cons:**
  - JWT revocation requires additional complexity
  - Token storage management needed for refresh tokens
  - Initial setup more complex than basic auth

**Implementation Notes:**
```typescript
// Dependencies: jose, @hono/node-server (for middleware compatibility)
// Password hashing with bcryptjs
// JWT expiration: 15 minutes for access, 7 days for refresh

import { SignJWT, jwtVerify } from 'jose';
import { hash, compare } from 'bcryptjs';

const JWT_SECRET = new TextEncoder().encode(process.env.JWT_SECRET!);

async function createToken(payload: Record<string, unknown>) {
  return new SignJWT(payload)
    .setProtectedHeader({ alg: 'HS256' })
    .setIssuedAt()
    .setExpirationTime('15m')
    .sign(JWT_SECRET);
}

async function verifyToken(token: string) {
  const { payload } = await jwtVerify(token, JWT_SECRET);
  return payload;
}

// Middleware
async function authMiddleware(c: Context, next: Next) {
  const token = c.req.header('Authorization')?.replace('Bearer ', '');
  if (!token) return c.json({ error: 'Unauthorized' }, 401);

  try {
    const payload = await verifyToken(token);
    c.set('user', payload);
    await next();
  } catch {
    return c.json({ error: 'Invalid token' }, 401);
  }
}
```

**Confidence:** HIGH
**Sources:**
- [jose Library Docs](https://github.com/panva/jose) | Verified: 2026-03-25
- [Hono Middleware Guide](https://hono.dev/docs/middleware/builtin/bearer-auth) | Verified: 2026-03-25

---

### Approach 2: Third-Party Auth (Auth0 / Firebase)

**Description:** Integrate with managed authentication service for production-ready auth with minimal code maintenance.

**Trade-offs:**
- **Pros:**
  - Battle-tested security - provider handles security updates
  - Rich feature set - 2FA, social login, SSO out of box
  - Reduced maintenance - no auth server to manage
  - Built-in user management UI
- **Cons:**
  - Vendor lock-in - migration complexity if changing providers
  - Cost - free tier limits, paid plans for production
  - Network dependency - API calls to provider on each auth
  - Learning curve - provider-specific SDKs

**Implementation Notes:**
```typescript
// Recommended: Auth0 (generous free tier, good Bun/Edge examples)
// Alternative: Firebase Authentication (Google ecosystem)

// Auth0 example with Node.js/Bun
import { AuthenticationClient } from 'auth0';

const auth0 = new AuthenticationClient({
  domain: process.env.AUTH0_DOMAIN!,
  clientId: process.env.AUTH0_CLIENT_ID!,
  clientSecret: process.env.AUTH0_CLIENT_SECRET!,
});

async function handleLogin(username: string, password: string) {
  const response = await auth0.oauth.passwordGrant({
    username,
    password,
    realm: 'Username-Password-Authentication',
  });
  return response.data.access_token;
}
```

**Confidence:** MEDIUM
**Sources:**
- [Auth0 Node.js SDK v5](https://auth0.github.io/node-auth0/) | Verified: 2026-03-25
- [Firebase Admin Setup](https://firebase.google.com/docs/admin/setup) | Verified: 2026-03-15

---

### Approach 3: Simple API Keys

**Description:** Basic API key authentication for internal APIs or service-to-service communication. Uses `X-API-Key` header with hashed key storage.

**Trade-offs:**
- **Pros:**
  - Simple implementation - minimal code
  - No external dependencies
  - Easy to understand and debug
  - Works well for internal tools or service accounts
- **Cons:**
  - API keys often long-lived - security risk if compromised
  - No built-in user management
  - No token expiration or refresh mechanism
  - Not suitable for user-facing applications

**Implementation Notes:**
```typescript
// Store hashed API keys in database
import { hash, compare } from 'bcryptjs';

async function validateApiKey(apiKey: string, hashedKey: string) {
  return compare(apiKey, hashedKey);
}

// Middleware
async function apiKeyMiddleware(c: Context, next: Next) {
  const apiKey = c.req.header('X-API-Key');
  if (!apiKey) return c.json({ error: 'Missing API key' }, 401);

  const user = await findUserByApiKey(apiKey);
  if (!user) return c.json({ error: 'Invalid API key' }, 401);

  c.set('user', user);
  await next();
}
```

**Confidence:** MEDIUM
**Sources:**
- [Hono Bearer Auth Middleware](https://hono.dev/docs/middleware/builtin/bearer-auth) | Verified: 2026-03-25

---

## Recommendations

**Recommended:** Approach 1 (JWT with jose)

**Reasoning:**
- Best balance of security, simplicity, and maintainability
- Native Bun/TypeScript compatibility
- JWT standard enables future scalability
- No vendor lock-in or external dependencies
- Suitable for both user authentication and service accounts
- jose library is well-maintained and Edge Runtime compatible

**When to consider alternatives:**
- Use Approach 2 (Auth0/Firebase) if team lacks auth expertise or needs enterprise features immediately
- Use Approach 3 (API Keys) only for internal tools or machine-to-machine communication

## Next Steps (Potential Tasks)

1. **jwt-auth-setup** - Implement JWT authentication with jose library
2. **user-registration** - Create user registration endpoint with bcrypt password hashing
3. **token-refresh** - Implement access/refresh token flow
4. **protected-routes** - Add authentication middleware to existing endpoints
5. **auth-tests** - Write tests for authentication flow

---

**Generated by:** sp:brainstorm
**Research delegation:** sp:source-driven-development, spur agent run
**Confidence:** HIGH (official jose/Hono documentation, 2026)