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.cursor/rules/security.mdc

Cursor security rule for Go

A focused Cursor `.mdc` rule for auth, secrets, and untrusted input. It attaches when those files change, instead of repeating security policy in every chat. This copy is written for a Go project. This repository is a Go module. Format with gofmt, keep the standard library first, and pass context through exported I/O.

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 Go module that gofmt can format. It does not assume a web framework. If the repo uses chi, gin, or the standard net/http, stay with that router.

Customize in the generatorBrowse the library

Example file

Balanced strictness, readable style, pragmatic tests. Download name: security.mdc

---
description: "Security rules for a Go repository"
globs: "**/*{auth,Auth,secret,config,Config}*"
alwaysApply: false
---

# Security rules

Attach these rules when editing auth, config, or secret-handling code in this Go repository.
This repository is a Go module. Format with gofmt, keep the standard library first, and pass context through exported I/O.

## Secrets and trust

- Do not log secrets when wrapping errors.
- Set timeouts on outbound HTTP. Do not use http.DefaultClient for untrusted URLs.
- Compare secrets with subtle.ConstantTimeCompare when the value is a token.

## Errors

- Fail at the boundary. Do not swallow errors.
- Return `error`. Wrap it with enough context to know which operation failed. Do not log and return the same error unless the caller cannot see the log.

## Done when

- Untrusted input is validated before a side effect.
- No secret was added to source, logs, or a client bundle.
- `gofmt` leaves the tree clean and `go test ./...` passes.

Add it to the project

  1. 01

    Copy a starting file

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

  2. 02

    Save it at .cursor/rules/security.mdc

    Save it at `.cursor/rules/security.mdc` in the Go repo. Narrow the globs if your auth and config files live in a known folder.

  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 Go agent often gets wrong, such as an exported function that takes context and returns a wrapped error. If it ignores the file, confirm the path and start a new session.

Questions about this file

Where do I put Cursor security rule in a Go repo?

Save it at `.cursor/rules/security.mdc` in the Go repo. Narrow the globs if your auth and config files live in a known folder.

Which tools read this Cursor security rule?

Cursor loads `.cursor/rules/security.mdc` for files that match its globs. Pair it with the always-on project rule. It is not a substitute for code review.

What does the Go example assume?

The example assumes a Go module that gofmt can format. It does not assume a web framework. If the repo uses chi, gin, or the standard net/http, stay with that router.

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 Go

Cursor security rule for other stacks