I Refactored a 150-File Backend with Two AI IDEs — Real Data, Real Pitfalls

150 Files, One Permission Module, Two Completely Different Experiences

Last week I took on a task: adding RBAC to a Node.js backend. The project had 152 files, roughly 18,000 lines of code, built with NestJS + TypeScript + PostgreSQL — with zero permission controls in place.

I completed the same task using both Cursor and Windsurf.

The results: Cursor Composer took about 2 hours with 6 manual interventions. Windsurf Cascade took about 15 minutes with 2 manual interventions.

But this isn’t a “Windsurf crushes Cursor” article. The reality is far more nuanced.

By the end of this post, you’ll know exactly what each tool excels at, where they fail, how to choose between them, and how to avoid the traps. Every prompt and step is reproducible.

Why This Test Matters

Most AI IDE comparison articles share a common flaw: they demo on a Hello World project and call it a day. That’s not how real developers work.

A real scenario looks like this:

• A project that’s been running for two years with accumulated technical debt
• 152 files spread across 6 modules under src/
• 47 existing API endpoints, all without authentication
• Need to add role-based access control without breaking anything
• TypeORM with PostgreSQL, requiring migrations

A seasoned developer would need roughly a day to do this manually: design permission tables, write decorators, add guards, configure permissions for every controller, write tests, and verify nothing broke.

It’s not rocket science, but the volume of work is real and easy to get wrong.

This is exactly where AI IDEs should shine — offloading mechanical bulk changes to AI while humans focus on design and verification.

Test Methodology: Same Task, Two Tools, Fair Comparison

To ensure fairness, I designed a rigorous comparison process:

Same task: Add role-based access control to all Controllers, create Role and Permission entities, generate migrations, and write unit tests.

Same project: Forked twice on GitHub, opened separately in Cursor and Windsurf with identical initial commits.

Same prompt (first phase):

Add a complete RBAC permission system to this NestJS project:

1. Create Role and Permission entities (TypeORM) with many-to-many relationships
2. Create a @RequireRoles('admin') decorator
3. Create a RolesGuard that extracts and validates roles from JWT tokens
4. Add appropriate role requirements to every method in all Controllers under src/modules/
5. Create the corresponding migration file
6. Write unit tests for the new Guard and Decorator
7. Do not modify any existing business logic code

The project uses TypeORM + PostgreSQL + Passport JWT.

Here’s the detailed breakdown.

Windsurf Cascade: 15 Minutes of Magic (and Its Cost)

Opened Windsurf, hit Cmd+I to bring up Cascade, pasted the prompt, hit Enter.

Round 1 (0–5 minutes)

Cascade started reading the project structure. The status bar showed Reading 152 files... and after about 30 seconds, it proposed a plan:

1. Create src/common/guards/roles.guard.ts
2. Create src/common/decorators/roles.decorator.ts
3. Create src/entities/role.entity.ts and src/entities/permission.entity.ts
4. Modify 6 Controller files to add decorators to each method
5. Create a migration

I clicked “Approve.” Cascade started writing code.

Here’s a detail worth noting: Cascade didn’t write everything at once. It followed dependency order — entities first, then decorators, then the guard, and finally the controller modifications. This suggests decent file dependency analysis.

Round 2 (5–10 minutes)

About 3 minutes later, Cascade finished all new files and started modifying existing Controllers. It added decorators to UserController like this:

@RequireRoles('admin')
@Get('users')
async findAll() { ... }

@RequireRoles('admin', 'manager')
@Patch('users/:id')
async update() { ... }

The role assignment logic was reasonable: write operations got admin, some read operations got manager and admin, and public login/register endpoints were left unrestricted.

But here’s where things went sideways. Cascade also modified auth.service.ts, injecting role-loading logic into the validateUser method. This would change the existing login flow behavior.

I clicked “Reject this change.” Cascade received the feedback and moved the role injection to a separate AuthService method instead of modifying the existing one.

Round 3 (10–15 minutes)

Finally, it automatically created the migration file and tests. Tests covered basic Guard and Decorator scenarios.

Final results:

• 6 new files created
• 6 Controller files modified
• 1 migration created
• Tests: 12 test cases, all passing
• Manual interventions: 2 (one rejection, one migration confirmation)

Verification: npm run start:dev started normally. Manual testing with Postman confirmed permission interception worked as expected.

Cursor Composer: Slow, But Controlled

Switched to Cursor, opened the Composer panel (Cmd+I), pasted the same prompt.

Round 1 (0–20 minutes)

Composer spent longer analyzing the project than Cascade. After about a minute, it output a plan — similar to Cascade’s, but with a key difference: Cursor’s approach was more conservative.

It didn’t automatically add decorators to Controllers. Instead, it created the infrastructure files (entities, decorators, guard) first, then asked me:

“I’ve created the basic RBAC components. Which Controllers should I add permission controls to? You can specify files, or I can analyze all Controllers and suggest appropriate roles.”

I chose “analyze all and suggest.”

Round 2 (20–60 minutes)

This was the most tedious phase. Composer started modifying Controllers one by one, but required confirmation for each file. 6 Controllers, 3-5 endpoints each, 24 total confirmations.

Cursor’s role assignments were more thoughtful than Windsurf’s. For example, it assigned GET /orders to both admin and support rather than broadly assigning it to manager. This shows it read more context to understand the business domain.

But the speed was noticeably slow. Each confirmation took 1-2 minutes, and sometimes it was “thinking” with no visible progress on screen.

Round 3 (60–90 minutes)

After finishing the Controllers, Composer started writing tests. It wrote 18 test cases — 6 more than Windsurf’s 12. It covered more edge cases: no-token access, expired tokens, insufficient roles, etc.

But one test failed:

✕ RolesGuard should allow access with valid role (32ms)
  Expected status 200, received 403

The cause was a typo in a Controller decorator parameter (admn instead of admin). Composer introduced a low-level bug during batch modifications.

I manually fixed the typo, reran the tests, and they all passed.

Round 4 (90–120 minutes)

Finally, the migration. Cursor auto-generated it but used synchronize: true instead of a proper migration file. I asked it to regenerate using TypeORM CLI, and it complied.

Final results:

• 6 new files created
• 6 Controller files modified
• 1 migration created
• Tests: 18 test cases, all passing (after typo fix)
• Manual interventions: 6 (24 confirmations + 1 typo fix + 1 migration correction)

Head-to-Head Comparison

Dimension	Windsurf Cascade	Cursor Composer
Completion time	~15 minutes	~120 minutes
Manual interventions	2	6
New files	6	6
Modified files	6	6
Test cases	12	18
First-run pass rate	100%	94% → 100% (after fix)
Role assignment quality	Moderate (conservative)	Higher (business-aware)
Code style consistency	Good	Good
Invasiveness	One unauthorized edit	One typo

On paper, Windsurf wins convincingly. But hold on before making a decision.

Three Real Pitfalls

Pitfall 1: Windsurf Cascade Modified Files It Shouldn’t Have

What happened: While adding decorators to Controllers, Cascade also modified auth.service.ts, injecting role-loading logic into the validateUser method. This wasn’t in the prompt.

Why: Cascade’s context analysis was too aggressive. It reasoned that since RBAC was being implemented, user roles should be loaded during login. The logic itself isn’t wrong, but directly modifying the existing method changes behavior.

Fix: Add an explicit constraint to the prompt:

Do not modify any existing method implementations. If you need to extend functionality, do so through new methods or files.

With this constraint, Windsurf’s second run had no unauthorized modifications.

Pitfall 2: Cursor Composer “Freezes” on Large Projects

What happened: Sometimes Composer would show “Thinking…” for 2-3 minutes with zero output. This happened more frequently with larger projects.

Why: Composer re-analyzes the entire project context before each operation. With 152 files consuming significant context window space, responses slowed considerably. Windsurf’s Cascade seems to handle context caching better.

Fix:

1. Use .cursorignore to exclude unnecessary directories (node_modules, dist, static assets)
2. Reference specific Controller files with @file in Composer instead of letting it scan the whole project
3. Break large tasks into smaller steps — have Composer create infrastructure first, then handle Controllers individually

Pitfall 3: Both Tools “Forget” Earlier Context

What happened: In multi-turn conversations, if the conversation grew too long, both tools forgot earlier modifications. For instance, after creating a Role entity, when asked to write tests later, it created a different Role entity structure.

Why: Context window limitations. Long conversations push out earlier information.

Fix:

1. Commit after each phase. Let the tool re-read the latest state from the filesystem
2. Repeat key context in your prompts
3. Try to complete tasks within a single conversation — don’t span across sessions

Cost Analysis

Plan	Cursor Pro	Windsurf Pro
Monthly	$20	$15
Yearly	$240	$180
AI Models	GPT-4o, Claude 3.5 Sonnet, etc.	Cascade (proprietary) + Claude
Composer/Cascade	✅ Unlimited	✅ Unlimited
Free tier	Limited Composer uses	Limited Cascade uses

Is it worth paying for?

If you code more than 10 hours per week, a Pro AI IDE will likely save you 20-30% of your time. At an average developer’s hourly rate, the monthly time savings far exceeds the subscription cost.

If you only occasionally write scripts or tweak configs, the free tiers are sufficient.

Which one to choose?

• Need to quickly complete well-defined bulk tasks → Windsurf (fast, autonomous)
• Need fine-grained control over every change → Cursor (high control, suited for careful refactoring)
• Frequent team collaboration and code reviews → Cursor (better Git integration, clearer diffs)
• Personal projects, speed-focused → Windsurf

Reproducible Prompt Template

Here’s the refined prompt template validated during this test — feel free to use it directly:

Add a complete RBAC permission system to this NestJS project:

1. Create Role and Permission entities (TypeORM) with many-to-many relationships
2. Create a @RequireRoles('admin') decorator
3. Create a RolesGuard that extracts and validates roles from JWT tokens
4. Add appropriate role requirements to every method in all Controllers under src/modules/
5. Create the corresponding migration file
6. Write unit tests for the new Guard and Decorator
7. [KEY] Do not modify any existing method implementations. Extend functionality through new methods or files only.

The project uses TypeORM + PostgreSQL + Passport JWT.

The critical part is that final constraint. Without it, the AI will likely “helpfully” modify things it shouldn’t.

Project Structure Reference

The test project structure looked roughly like this:

src/
├── common/
│   ├── decorators/
│   ├── filters/
│   └── guards/          ← AI created roles.guard.ts here
├── entities/
│   ├── user.entity.ts
│   ├── role.entity.ts   ← New
│   └── permission.entity.ts  ← New
├── modules/
│   ├── auth/
│   │   ├── auth.controller.ts
│   │   ├── auth.service.ts
│   │   └── auth.module.ts
│   ├── users/
│   │   ├── users.controller.ts  ← Modified
│   │   └── users.service.ts
│   ├── orders/
│   │   ├── orders.controller.ts ← Modified
│   │   └── orders.service.ts
│   └── ... (other modules)
├── migrations/
│   └── xxx_add_rbac.ts   ← New
└── app.module.ts

Final Thoughts

This isn’t a sponsored post or a hit piece. I’ve been a paying user of both tools for at least two months.

AI IDEs are still early. Both Cursor and Windsurf perform beautifully on simple tasks and occasionally stumble on complex ones. The difference lies in how they stumble:

• Cursor’s failure mode: slow + frequent confirmations required
• Windsurf’s failure mode: fast + occasionally overstepping bounds

Which one you choose depends on which failure mode you can better tolerate.

I’d recommend trying both on a real project yourself. Both have free tiers — spend 30 minutes and form your own judgment.

After all, someone else’s benchmark is secondhand information. Your own experience is what matters.

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Found this useful? Share it with a friend who’s deciding between AI IDEs. Got technical questions? Drop them in the comments — I reply to all of them.