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.cursor/rules/security.mdc

Cursor security rule for Rust

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 Rust project. This repository is a Rust crate on Cargo. Format with rustfmt, lint with cargo clippy, and use Result for recoverable failure.

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 Cargo crate, edition 2021 or newer. It does not assume a web framework or async runtime. Use thiserror or anyhow only when that crate is already a dependency.

Customize in the generatorBrowse the library

Example file

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

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

# Security rules

Attach these rules when editing auth, config, or secret-handling code in this Rust repository.
This repository is a Rust crate on Cargo. Format with rustfmt, lint with cargo clippy, and use Result for recoverable failure.

## Secrets and trust

- Do not unwrap on input that an attacker can choose.
- Keep secrets out of the repo and out of tracing spans.
- Do not add unsafe to skip a validation check.

## Errors

- Fail at the boundary. Do not swallow errors.
- Use the project's error type. If it has none, return `Result<T, impl std::error::Error>` only at the edge, and keep library errors typed.

## Done when

- Untrusted input is validated before a side effect.
- No secret was added to source, logs, or a client bundle.
- `cargo test` passes. Run `cargo clippy --all-targets -- -D warnings` when the change is more than a comment.

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 Rust 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 Rust agent often gets wrong, such as a function that returns Result instead of unwrap on library input. 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 Rust repo?

Save it at `.cursor/rules/security.mdc` in the Rust 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 Rust example assume?

The example assumes a Cargo crate, edition 2021 or newer. It does not assume a web framework or async runtime. Use thiserror or anyhow only when that crate is already a dependency.

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 Rust

Cursor security rule for other stacks