What a production-ready .cursorrules covers for frontend, backend, SaaS, DevOps, mobile, data and AI/ML work — with a free example to copy. Brainfile itself is built for Claude Code, not Cursor.
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The Problem
Writing your own .cursorrules is hard
Every developer who opens Cursor for the first time faces the same wall: the default rules are too generic to be useful, and writing good ones from scratch takes longer than the work itself.
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Cursor doesn't know your stack
Without a strong .cursorrules file, Cursor keeps making the same wrong assumptions — suggesting the wrong framework, missing your naming conventions, and generating boilerplate you immediately delete.
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You re-explain your stack every session
You paste the same context into every new chat: "I use React, TypeScript, Tailwind, Postgres, deployed on Fly.io..." A good .cursorrules file encodes this once. Most devs never write one.
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Your rules drift and go stale
Even the devs who write a .cursorrules file from scratch end up with a patchwork of half-remembered rules that no longer reflect how they actually code. Cursor ignores stale rules — or worse, follows them.
The Solution
What a battle-tested .cursorrules looks like
Start from a structure instead of a blank file: role, stack, conventions, guardrails. The example below is free to copy. Fill in your stack, database and deploy target, and your Cursor session knows who you are, what you're building, and how you code.
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Role-aware from the start
Write it for your specific engineering role — not a generic "developer." A frontend file should cover component architecture. A SaaS file should cover multi-tenancy and Stripe webhooks.
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Three-field customization
The example has three blanks: your stack, your database, and your deploy target. Fill those in, then add the conventions your team actually enforces.
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Review it when Cursor changes
Cursor changes its rules format and capabilities every few months. Re-check your file when it does; stale rules quietly lower output quality. (Brainfile's weekly freshness feed covers Claude Code, not Cursor.)
# Role: Senior Frontend Engineer# Stack: React 18 + TypeScript + Tailwind CSS + Vite# Deploy: Vercel · DB: Supabase## Component Architecture- Always use function components with explicit TypeScript interfaces- Props interface named [ComponentName]Props, exported for reuse- Co-locate component, types, tests, and styles in /components/[Name]/- Prefer composition over prop drilling beyond 2 levels — use Context## TypeScript Conventions- Strict mode enabled — no implicit any, no non-null assertions without comment- Use discriminated unions for state machines, never boolean flags- API response types live in /types/api.ts, never inlined## Styling Rules- Tailwind utility classes only — no custom CSS except for animations- Mobile-first breakpoints: sm: md: lg: xl: — always in that order- Dark mode via class strategy ("dark" on html), not media query## Testing- Vitest + React Testing Library — test behavior, not implementation- Every component gets a smoke test. Business logic gets unit tests.
Configuration Library
What a .cursorrules should cover, by role
Eight engineering roles and the conventions, patterns and guardrails each file should encode. Use them as a checklist when you write yours. No fluff, no generic advice — only rules that change how Cursor behaves.
Three steps from zero to a Cursor that knows your codebase
Pick the role checklist that fits, write the file with your stack, and Cursor reads it on every request.
1
Pick your role checklist
Use the role list above that matches how you actually work: frontend, backend, SaaS, DevOps, mobile, data, or AI/ML.
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2
Add your stack in 3 lines
Fill in your framework, your database, and your deploy target, then write the conventions, patterns and guardrails your role cares about.
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3
Drop into Cursor → done
Save the file as .cursorrules in your project root. Open Cursor. It reads the file automatically. No setup, no config, no API keys. It just works.
Comparison
Where Brainfile fits
Brainfile is built for Claude Code, not Cursor. It ships no .cursorrules files. If you also use Claude Code, here is what it adds there.
Category
✦ Brainfile (Claude Code)
Write your own
What it ships
CLAUDE.md, .claude/rules/ and brain/ files, plus the Autopilot protocol
The .cursorrules you write for Cursor
Staying current
A weekly freshness feed for Claude Code changes
Manual — you research and update yourself
Role setup
15 role packs on Pro, including Software Developer and DevOps
Your one role
Cursor support
None — Brainfile ships no Cursor format
Native
Also using Claude Code?
Your Claude Code should know how you code. Not the other way around.
Brainfile for Claude Code: the Autopilot protocol, 10 pattern files and a weekly freshness feed. Pro adds 15 role packs. Start free — 30 days, no card.