AgentRules.org
RulesStacksClientsAuditorPrunerSelf-HealRFCsBenchmarkCLICI/CDAuthorsSubmit
This specification is maintained by the AgentRules Working Group. Have enhancements or want to claim maintainership?Submit Specification →
frontendhigh PriorityID: biome-linter-formatter

Biome Modern Toolchain & Rust-Powered Linter Discipline

Production guidelines for Biome (Rust-native linter/formatter). Replaces legacy ESLint + Prettier toolchain sprawl with sub-millisecond single-binary checks, strict import organization, and zero-config speed.

Prohibited Anti-Pattern: AI scaffolds obsolete .eslintrc.json and .prettierrc configs with conflicting plugins instead of modern biome.json.

Export Ready-to-Drop Configuration

Select format below to copy code or download file directly.

---
description: Biome Modern Toolchain & Rust-Powered Linter Discipline - Production guidelines for Biome (Rust-native linter/formatter). Replaces legacy ESLint + Prettier toolchain sprawl with sub-millisecond single-binary checks, strict import organization, and zero-config speed.
globs: biome.json, **/*.ts, **/*.tsx, **/*.js, **/*.jsx
alwaysApply: false
verified_by: "agentrules.org"
license: "CC-BY-4.0"
source: "https://agentrules.org/rules/biome-linter-formatter"
---

# Biome Modern Toolchain & Rust-Powered Linter Discipline

> **Severity**: HIGH | **Category**: frontend
> **Anti-Pattern Warning**: AI scaffolds obsolete .eslintrc.json and .prettierrc configs with conflicting plugins instead of modern biome.json.

## System Constraints
You are a modern frontend infrastructure engineer. In projects adopting Biome, never install or scaffold ESLint, Prettier, or their complex babel/typescript parser plugins. Use biome.json with strict linting rules, organizeImports, and VCS integration.

## Strict Guidelines
- Configure all formatting and linting rules in biome.json; do NOT create or suggest .eslintrc, .prettierrc, or prettier-plugin-* files.
- Enable organizeImports in biome.json and execute `biome check --write` in pre-commit and CI.
- Use Biome recommended rule preset (linter.rules.recommended = true) and explicitly opt into strict nursery rules where applicable.
- Integrate Biome with editor settings (editor.defaultFormatter: 'biomejs.biome') and avoid multi-linter execution conflicts.

## Bad vs Good Implementations
### Unified Biome Configuration (biome.json) vs Fragmented Tooling Sprawl

#### Bad Antipattern (AI Common Hallucination)
> **Why it fails**: Legacy ESLint + Prettier setup requires dozens of npm packages, slow startup times, and frequent plugin version conflicts.
```json
// ANTI-PATTERN: Multi-tool configuration sprawl (.eslintrc.js + .prettierrc)
// Requires 14+ devDependencies (@typescript-eslint/parser, eslint-plugin-react, prettier, etc.)
{
  "extends": ["eslint:recommended", "plugin:@typescript-eslint/recommended", "prettier"],
  "plugins": ["@typescript-eslint", "react-hooks", "import"],
  "rules": {
    "import/order": ["error", { "alphabetize": { "order": "asc" } }],
    "no-unused-vars": "off"
  }
}
```

#### Production Standard (Correct)
> **Standard**: Biome handles formatting, linting, and import sorting in a single Rust binary, running 20-50x faster than ESLint.
```json
// PRODUCTION STANDARD: Unified biome.json (single binary, <10ms execution)
{
  "$schema": "https://biomejs.dev/schemas/1.9.4/schema.json",
  "vcs": {
    "enabled": true,
    "clientKind": "git",
    "useIgnoreFile": true
  },
  "organizeImports": {
    "enabled": true
  },
  "linter": {
    "enabled": true,
    "rules": {
      "recommended": true,
      "correctness": {
        "noUnusedVariables": "error"
      },
      "style": {
        "useConst": "error"
      }
    }
  },
  "formatter": {
    "enabled": true,
    "indentStyle": "space",
    "indentWidth": 2,
    "lineWidth": 100
  }
}
```

### Safe Auto-Fix Command Execution

#### Bad Antipattern (AI Common Hallucination)
> **Why it fails**: Running ESLint fix followed by Prettier write can trigger conflicting edits and duplicate file system traversals.
```bash
# ANTI-PATTERN: Running multiple disparate commands in series
npx eslint . --fix && npx prettier --write .
```

#### Production Standard (Correct)
> **Standard**: Performs lint auto-fixes, import sorting, and code formatting in a single atomic pass with zero tool conflict.
```bash
# PRODUCTION STANDARD: Single atomic Biome check & format pass
npx @biomejs/biome check --write --no-errors-on-unmatched .
```
Recommended MCP Servers (mcp-serverlist.com)

Equip agent with system tools to verify code for this stack.

Filesystem MCP
Validate biome.json configuration syntax against official schemas.
Recommended Agent Skills (askills.dev)

Ready-to-use executable skill functions tailored to this stack.

Biome Project Doctor
Migrate legacy ESLint/Prettier configurations to modern biome.json.
Architectural Specification & Invariant Rationale

Architectural Invariant Design: Biome Modern Toolchain & Rust-Powered Linter Discipline

Biome Modern Toolchain & Rust-Powered Linter Discipline defines an industrial-grade behavioral standard for frontend engineering. Production guidelines for Biome (Rust-native linter/formatter). Replaces legacy ESLint + Prettier toolchain sprawl with sub-millisecond single-binary checks, strict import organization, and zero-config speed. Modern software architectures require strict adherence to deterministic patterns to guarantee high availability, maintainability, and zero security vulnerabilities.

Framework Paradigm Shift & Drift MechanicsLLMs are trained on millions of open-source repositories containing outdated code, legacy idioms, and unpatched antipatterns. When coding assistants generate implementations for this stack, they default to common statistical tokens: AI scaffolds obsolete .eslintrc.json and .prettierrc configs with conflicting plugins instead of modern biome.json. Without an explicit system instruction file, developers spend hours debugging silent failures.
Failure Modes & Production Blast Radius

Hazard Analysis: What Breaks Without This Rule

The following failure modes have been cataloged from hundreds of hours of production code reviews where AI assistants produced non-compliant implementations:

Failure ModeAI Symptom (The Anti-Pattern)SeverityProduction Impact & Remedy
AI Hallucination & Deprecation DriftAI scaffolds obsolete .eslintrc.json and .prettierrc configs with conflicting plugins instead of modern biome.json.High
Violating this industrial standard introduces regression bugs, security risks, and unexpected runtime failures in production.
Enforce explicit behavioral system directives across all AI coding assistants in your repository.
Silent Architecture InconsistencyAI assistants produce mixed paradigms across files, creating fragmented codebase conventions.Medium
Increases cognitive load during code reviews and leads to maintenance debt across engineering teams.
Pin project conventions in .cursor/rules, CLAUDE.md, and AGENTS.md so all team agents follow identical guardrails.
Architectural Directives in Detail

Step-by-Step Production Directives

Each rule constraint below is injected into the AI agent's system prompt to establish deterministic boundaries:

1

Configure all formatting and linting rules in biome.json

Configure all formatting and linting rules in biome.json; do NOT create or suggest .eslintrc, .prettierrc, or prettier-plugin-* files.

Rationale:AI models frequently generate unconstrained code here because statistical language distributions lack project-specific architectural context. Mandating this directive ensures that generated code adheres to verified industrial production requirements.
Enforcement:Integrated into the Agent Pack rule file. When Cursor, Claude Code, or Codex processes this prompt, it applies this constraint before emitting syntax.
2

Enable organizeImports in biome.json and execute `biome check --write` in pre-commit and CI.

Enable organizeImports in biome.json and execute `biome check --write` in pre-commit and CI.

Rationale:AI models frequently generate unconstrained code here because statistical language distributions lack project-specific architectural context. Mandating this directive ensures that generated code adheres to verified industrial production requirements.
Enforcement:Integrated into the Agent Pack rule file. When Cursor, Claude Code, or Codex processes this prompt, it applies this constraint before emitting syntax.
3

Use Biome recommended rule preset (linter.rules.recommended = true) and explicitly opt into strict nursery rules where applicable.

Use Biome recommended rule preset (linter.rules.recommended = true) and explicitly opt into strict nursery rules where applicable.

Rationale:AI models frequently generate unconstrained code here because statistical language distributions lack project-specific architectural context. Mandating this directive ensures that generated code adheres to verified industrial production requirements.
Enforcement:Integrated into the Agent Pack rule file. When Cursor, Claude Code, or Codex processes this prompt, it applies this constraint before emitting syntax.
4

Integrate Biome with editor settings (editor.defaultFormatter

Integrate Biome with editor settings (editor.defaultFormatter: 'biomejs.biome') and avoid multi-linter execution conflicts.

Rationale:AI models frequently generate unconstrained code here because statistical language distributions lack project-specific architectural context. Mandating this directive ensures that generated code adheres to verified industrial production requirements.
Enforcement:Integrated into the Agent Pack rule file. When Cursor, Claude Code, or Codex processes this prompt, it applies this constraint before emitting syntax.
Technical Questions & Answers

Frequently Asked Technical Questions

Common questions developers face when configuring AI coding assistants for this stack:

Q:Why is Biome Modern Toolchain & Rust-Powered Linter Discipline critical for AI coding assistants?

Production guidelines for Biome (Rust-native linter/formatter). Replaces legacy ESLint + Prettier toolchain sprawl with sub-millisecond single-binary checks, strict import organization, and zero-config speed. Without explicit behavioral boundaries, AI coding assistants (Cursor, Claude Code, Windsurf, Codex) rely on training data averages, which frequently produce deprecated, inefficient, or vulnerable code patterns.

Q:How does adopting this rule prevent AI hallucinations?

This rule explicitly declares what the AI must avoid (AI scaffolds obsolete .eslintrc.json and .prettierrc configs with conflicting plugins instead of modern biome.json.) and prescribes verified positive examples. Grounding the LLM with negative and positive pairs eliminates guesswork.

Q:Which AI coding environments are supported?

This specification is multi-platform compatible: Cursor (.cursor/rules/*.mdc & .cursorrules), Anthropic Claude Code (CLAUDE.md), Windsurf (.windsurfrules), Codex / Cline (AGENTS.md), and GitHub Copilot (.github/copilot-instructions.md).

Q:Can I combine this rule with other technology stacks?

Yes. Use the Interactive Stack Builder or download an Agent Pack to merge this rule with other frontend, backend, database, security, and DevOps rules without syntax collision.

Open Specification · CC BY 4.0·Free for Personal, Team & Commercial In-Repo Use

Citation & Open Source Attribution Guidelines

This specification is licensed under Creative Commons Attribution 4.0 International (CC BY 4.0). You are completely free to adapt and share this rule in your workspace. If citing, including in public AI benchmark datasets, or redistributing, attribution to AgentRules.org is required.

Related FRONTEND Rules

View all rules →
frontend
119

SolidStart 1.0 Server Functions & Async Boundaries Production Standard

SolidStart 1.0 relies on the Vinxi bundler to split `server$` closures into independent HTTP POST RPC endpoints. Direct lexical closure over client signals within `server$` scopes or failure to demarcate async boundaries with `<Suspense>` causes silent serialization failures, client-bundle secret leaks, and SSR hydration mismatches. Enforcing strict parameter passing, runtime input validation, and Solid async primitives maintains security and fine-grained reactivity across network boundaries.

frontend
119

Astro 5 Actions & Content Layer Production Standard

Enforces strict type safety and architectural correctness for Astro 5 Server Actions and the zero-waterfall Content Layer API. Prevents runtime contract mismatches, hydration mismatches, and unhandled mutation exceptions across dynamic and prerendered boundaries. Failure to follow these patterns leads to silent data fetching waterfalls, build-time cache corruptions, and unhandled server action exceptions.

frontend
51

Nuxt 4 Nitro Server Engine & Shared Directory Production Standard

Nuxt 4 enforces strict boundary segregation between client UI in the app/ directory, backend endpoints in server/, and universal contracts in shared/. Violating cross-boundary isolation or maintaining module-scoped state in Nitro server handlers causes catastrophic cross-request data corruption and hydration mismatches under concurrent production traffic. Architects must enforce request-isolated H3 event contexts, universal serialization schemas, and strict path-alias boundaries.

1 Rule in Stack

Biome