Cursor vs Windsurf: Building a Full-Stack Feature from Scratch
The Prompt
Build a complete user authentication system with email/password signup, login, password reset flow, and session management. Use Next.js 15 App Router with server actions, Prisma ORM with PostgreSQL, and implement proper CSRF protection. Include the database schema, API routes, middleware, and a basic UI with form validation.
This test evaluates how each AI coding assistant handles a complex, multi-file feature build that requires architectural decisions, security awareness, and coordination across frontend and backend layers. Both tools were given the same prompt in a fresh Next.js 15 project with Prisma already configured.
CursorWindsurf — faster but shipped security gaps
Cursor's Agent Mode approached this methodically in 3 rounds of prompting:\n\n**Round 1 — Schema & Backend:**\nGenerated a complete Prisma schema with User, Session, and PasswordResetToken models. Created server actions for signup (with bcrypt hashing), login (with session cookie creation), and a password reset flow using crypto.randomUUID() for tokens. Added proper CSRF middleware using the double-submit cookie pattern.\n\n**Round 2 — Frontend & Validation:**\nBuilt signup/login/reset forms using React Server Components with progressive enhancement. Used Zod for server-side validation with errors surfaced via useActionState. Forms work without JavaScript enabled. Added rate limiting on the reset endpoint.\n\n**Round 3 — Polish & Security:**\nAfter prompting \"review for security issues,\" Cursor identified and fixed: timing-safe comparison for tokens, HTTP-only secure cookie flags, session rotation on login, and added a migration file. Also suggested (but didn't auto-implement) email verification as a next step.\n\n**Files created:** 14 files across schema, actions, middleware, components, and utils.\n**Total interaction time:** ~4 minutes with review between rounds.\n**Notable:** Each step required explicit approval before execution. Cursor showed its diff preview before applying changes, letting the developer verify the approach at each stage.
WindsurfWindsurf — faster but shipped security gaps
Windsurf's Cascade mode executed this as a single autonomous flow:\n\n**Cascade ran 8 sequential steps without intervention:**\n1. Analyzed the existing project structure and Prisma config\n2. Generated the database schema (User, Session, PasswordReset models)\n3. Created all server actions (signup, login, logout, requestReset, confirmReset)\n4. Built middleware for session validation and CSRF protection\n5. Generated form components with client-side + server-side validation\n6. Added a shared auth utility library\n7. Ran the Prisma migration automatically\n8. Created a basic test file for the auth flows\n\n**Files created:** 16 files including the test file and a README section.\n**Total interaction time:** ~2.5 minutes, fully autonomous.\n**Notable:** Windsurf used its Codemaps feature to understand the existing project layout before generating code, which meant imports and paths were correct on the first try. However, it used SHA-256 for password hashing instead of bcrypt (a security concern), and the CSRF implementation used a simpler origin-check pattern rather than double-submit cookies. The session management worked but lacked session rotation on privilege escalation.\n\n**After prompting for security review:** Windsurf caught the SHA-256 issue and swapped to argon2, added session rotation, but still missed the timing-safe token comparison.
🔍 Analysis
This battle highlights the fundamental philosophical difference between these two tools. Cursor's controlled, step-by-step approach produced more secure code out of the gate — bcrypt from the start, double-submit CSRF, timing-safe comparisons. The developer stayed in the loop and could catch issues before they were written. Windsurf was significantly faster (2.5 min vs 4 min) and produced more files (including tests), but its autonomous execution introduced security gaps that required additional review.\n\nFor feature building specifically, the question becomes: do you value speed or security-by-default? In a production codebase, Cursor's approach of showing diffs and requiring approval at each stage reduces the chance of shipping vulnerable code. Windsurf's autonomous mode is better suited for prototyping, internal tools, or situations where a senior developer will review everything afterward.\n\nThe iBuildR Research benchmark (March 2026) aligns with our findings: Cursor completed a comparable component in 2 rounds vs Windsurf's 3 for simpler tasks, but for security-sensitive features, Cursor's deliberate approach pays dividends.\n\nCursor wins this battle narrowly — not because it's faster or produces more code, but because when you're building auth systems, getting security right the first time matters more than saving 90 seconds.
"We had Cursor and Windsurf build a full auth system from scratch. Cursor took 4 min with developer approval at each step. Windsurf did it in 2.5 min autonomously. But Windsurf shipped SHA-256 password hashing and missed CSRF edge cases. Speed vs security — which matters more for your team?"