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.windsurf/rules/project.md

Windsurf rules for T3

Windsurf rules tell the Cascade agent how this repo is built and tested. The current location is `.windsurf/rules`. Older setups still read a root `.windsurfrules` file. This copy is written for a T3 project. This repository is a T3 app: Next.js, tRPC, and the database client the repo already uses. Inputs are validated with Zod. The database is never imported into a client component.

The example uses a balanced, readable style, pragmatic tests, and comments only where the intent is not obvious. Open the generator to make the agent stricter, switch to test-first, quiet the comments, or pick a different file.

The example assumes a T3-style Next.js app with tRPC. It does not assume Prisma versus Drizzle, or a particular auth library. Use the one in the repo.

Customize in the generatorBrowse the library

Example file

Balanced strictness, readable style, pragmatic tests. Download name: project.md. Legacy path: .windsurfrules

# Windsurf rules

Rules for Windsurf Cascade in this T3 repository.
If the project still uses a root `.windsurfrules` file, keep the same rules there.

## Stack

This repository is a T3 app: Next.js, tRPC, and the database client the repo already uses. Inputs are validated with Zod. The database is never imported into a client component.

## Layout

- Routers live in the server API tree the project already uses.
- The database client is imported only from server code.
- Shared Zod schemas live next to the procedure or in a shared validators module.

## Commands

- Dev server: `npm run dev`
- Typecheck: `npm run typecheck`
- Tests: `npm test`

Use the script the repo already defines when it differs from the command above.

## Conventions

- Every mutation input is a Zod schema. Do not accept `unknown` and cast it.
- Use the public procedure or protected procedure the router already exports.
- Do not import the database into a file marked `use client`.
- Environment variables go through the project's env schema.
- Return typed data the client can infer. Do not throw plain strings.
- Match the existing app-router or pages-router entry. Do not add the other one.

## Testing

Add or update tests when behavior changes.

Call the procedure with a caller or the project's test helper. Cover one invalid Zod input.

## Style

- Optimize for the next reader over the shortest diff.
- Comment only when the why is non-obvious.
- Name things the way neighboring files already do.
- Do not reformat code you did not change.

## Errors

- Fail at the boundary. Do not swallow errors.
- Use TRPCError with a code for expected failures. Unexpected errors can propagate.

## Scope

- Do the requested task. Do not refactor unrelated code.
- Match the rigor already in the repo. Fix what you touch.
- Ask one clarifying question only when the task cannot be finished without it. Otherwise state the assumption and continue.

## Avoid

- Do not call the database from a React component to 'save a round trip'.
- Do not skip the protected procedure and read the session by hand in a new style.
- Do not add REST routes next to tRPC for the same resource.
- Do not commit `.env`. The env schema should fail fast when a variable is missing.

## Done when

- The requested behavior works.
- `npm run typecheck` passes and the procedure rejects an invalid input.
- The diff stays inside the task.
- You list anything you could not run.

Add it to the project

  1. 01

    Copy a starting file

    Copy the example Windsurf rules on this page, or open the generator if you want different testing, strictness, or comment rules.

  2. 02

    Save it at .windsurf/rules/project.md

    Save it at `.windsurf/rules/project.md` in the T3 repo. If the project still uses a single root file, save the same body as `.windsurfrules`.

  3. 03

    Start a fresh agent session

    Rules files are read when a session starts. A chat that is already open may still be using the old instructions.

  4. 04

    Give it one small task

    Ask for one change a T3 agent often gets wrong, such as a tRPC procedure that validates input with Zod and rejects a bad id. If it ignores the file, confirm the path and start a new session.

Questions about this file

Where do I put Windsurf rules in a T3 repo?

Save it at `.windsurf/rules/project.md` in the T3 repo. If the project still uses a single root file, save the same body as `.windsurfrules`.

Which tools read this Windsurf rules?

Windsurf reads `.windsurf/rules/*.md` and, on older projects, `.windsurfrules`. Cursor and Claude Code do not load this path.

What does the T3 example assume?

The example assumes a T3-style Next.js app with tRPC. It does not assume Prisma versus Drizzle, or a particular auth library. Use the one in the repo.

Does VibeSpell upload my repository?

No. Recipe pages are static, and the generator builds the file in your browser from the options you pick. Your source code never leaves the machine.

Other files for T3

Windsurf rules for other stacks