# Biome Grit Rules

> Use when creating, reviewing, or modifying custom Biome Grit plugins in plugins/*.grit, especially deterministic agent-correction rules for stale Effect v3 patterns, local style hazards, and diagnostic messages that tell agents what to do next.

- **Type:** Skill
- **Install:** `agentstack add skill-theseus-run-theseus-biome-grit-rules`
- **Verified:** Yes — security-reviewed for prompt injection and unsafe behavior
- **Seller:** [theseus-run](https://agentstack.voostack.com/s/theseus-run)
- **Installs:** 0
- **Category:** [Agent Skills](https://agentstack.voostack.com/c/agent-skills)
- **Latest version:** 0.1.0
- **License:** MIT
- **Upstream author:** [theseus-run](https://github.com/theseus-run)
- **Source:** https://github.com/theseus-run/theseus/tree/master/.agents/skills/biome-grit-rules
- **Website:** https://www.theseus.run

## Install

```sh
agentstack add skill-theseus-run-theseus-biome-grit-rules
```

Requires the [AgentStack CLI](https://agentstack.voostack.com/docs/cli). Works with Claude Code, Cursor, and any MCP-compatible agent.

## About

# Biome Grit Rules

Use this skill for repo custom lint rules under `plugins/*.grit`.

## Purpose

Custom rules turn repeated agent mistakes into deterministic feedback. In this repo, Effect v3 patterns are a primary target because they are common in model training data while Theseus uses Effect v4 patterns.

## Before Adding A Rule

Add or tighten a rule only when:

- the bad pattern is syntactically recognizable
- the desired replacement is deterministic or clearly explainable
- false positives are low
- the pattern has appeared more than once, is high-risk, or reflects stale API training data
- the rule can produce a useful diagnostic at the exact bad span

Propose first instead of editing when the rule could affect many files or needs semantic judgment.

## Diagnostic Messages

Every diagnostic message should act as a small prompt:

- name the repo rule or API generation, such as `Effect v4`
- say what is wrong
- say what to do instead
- mention the relevant skill when the mistake implies a stale mental model

Example shape:

```text
Effect v4: Effect.catchAll was renamed to Effect.catch. Use Effect.catch for all typed errors, Effect.catchTag/Effect.catchTags for specific tags, or Effect.catchCause for cause-level handling. Load skill: effect-v4.
```

Do not hard-code exact dependency versions unless the version itself is the rule.

## Severity

- Use `error` for stale APIs, known unsafe patterns, and hard repo invariants.
- Use `warning` for style guidance or patterns with legitimate exceptions.
- Avoid broad rules that force taste when the repo does not have a stable invariant.

## Verification

After changing a rule:

1. Run `bunx biome check ` against a file that should trigger or currently triggered the rule.
2. Confirm the diagnostic span and message are clear.
3. Run the focused check against at least one nearby clean file when false positives are plausible.
4. Run `bun run lint` when the rule is broad or touches shared config.

## Maintenance

- Keep plugin filenames specific and negative: `no-effect-v3-catchall.grit`.
- Keep messages short enough to read in terminal output.
- Prefer rules that remove a whole class of future fixes.
- If a rule fires too broadly, narrow the pattern before lowering severity.

## Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

- **Author:** [theseus-run](https://github.com/theseus-run)
- **Source:** [theseus-run/theseus](https://github.com/theseus-run/theseus)
- **License:** MIT
- **Homepage:** https://www.theseus.run

Install and usage instructions live in the source repository linked above.

## Pricing

- **Free** — Free

## Security capabilities

Automated source analysis of v0.1.0 — what this tool can access:

- **Network access:** no
- **Filesystem access:** no
- **Shell / process execution:** no
- **Environment & secrets:** no
- **Dynamic code execution:** no

*"Yes" means the capability is present in the source — more access means more to trust, not that it is unsafe.*


## Versions

- **0.1.0** — security scan: passed — Imported from the upstream source.

## Links

- Listing page: https://agentstack.voostack.com/l/skill-theseus-run-theseus-biome-grit-rules
- Seller: https://agentstack.voostack.com/s/theseus-run
- Browse the marketplace: https://agentstack.voostack.com/browse

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Listed on AgentStack — the marketplace for AI agent skills and MCP servers. Every listing is security-reviewed. Creators keep 70%.