Biome is a web-development toolchain that formats and checks source code for languages such as JavaScript, TypeScript, JSX, and CSS. Developers use its command-line and language-server interfaces to maintain code quality in web projects. Catalogue add-ons extend workflows around the toolchain.
Borrowing it
Nothing to install: this file belongs to biomejs/biome. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/biomejs/biome/main/.claude/skills/eslint-migrate-options/SKILL.mdgit clone --depth 1 https://github.com/biomejs/biomeWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/biomejs/biome/eslint-migrate-options)<a href="https://agentmods.dev/skills/biomejs/biome/eslint-migrate-options"><img src="https://agentmods.dev/badge/skills/biomejs/biome/eslint-migrate-options/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/biomejs/biome/eslint-migrate-options"><img src="https://agentmods.dev/badge/skills/biomejs/biome/eslint-migrate-options.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- Snyk pass
- NVIDIA SkillSpector pass
What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00053 | $0.01139 |
| Opus 5 | $0.00026 | $0.00570 |
| Sonnet 5 | $0.00011 | $0.00228 |
| Haiku 4.5 | $0.00005 | $0.00114 |
Grade A, and why
eslint-migrate-options scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 10d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 133 lines — stays where its author put it; the contents beside it link to each section on GitHub.
ESLint Option Migration
Use a custom migrator only when an existing Biome rule should preserve meaningful ESLint options. Severity-only migration belongs to the generated rule mapping.
Preconditions
Confirm before editing:
- The Biome rule and its option type already exist.
- Rule metadata identifies the ESLint source rule.
- Generated severity migration already exists or will be regenerated.
- Official ESLint or plugin documentation establishes the exact option shape and defaults.
- The supported Biome semantics are clear, including unsupported source options.
Load lint-rule-development when the Biome rule or its own options still need implementation.
Pipeline
Custom migration has four parts:
- A plugin-specific type deserializes the ESLint payload.
- A conversion maps source semantics into the Biome option type.
- The shared ESLint
Ruleenum recognizes the rule as a typed variant. migrate_eslint_rule()installs the resulting Biome configuration after common severity handling.
Key Files
| File | Responsibility |
|---|---|
eslint_eslint.rs |
Shared config model, Rule, RuleConf<T>, and dispatch |
eslint_unicorn.rs |
Unicorn option types and conversions |
eslint_typescript.rs |
TypeScript ESLint option types and conversions |
eslint_jsxa11y.rs |
JSX accessibility option types and conversions |
eslint_to_biome.rs |
Main conversion and custom migration arms |
eslint_any_rule_to_biome.rs |
Generated severity mapping |
tests/specs/migrate_eslint/ |
Fixture-driven migration snapshots |
Use the plugin-specific module matching the source rule and inspect a current migrator with a similar payload and Biome configuration type.
Model Source Options
Model the ESLint JSON shape rather than the Biome destination shape.
- Preserve source nesting until conversion.
- Use optional fields where the source allows omission.
- Match current deserialization naming and default conventions from neighboring option types.
- Model fields needed to deserialize supported real configurations.
- Verify unsupported source fields do not make valid configurations fail; whether they need explicit fields depends on the current deserializer contract.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 10d ago First seen · 133 lines · 53 tokens per session scan A 70b39d6e6a17
eslint-migrate-options is a skill published in the GitHub repository biomejs/biome (25,752 stars, last pushed today), licensed Apache-2.0. It adds 53 tokens to every session and 1,139 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
Other skills, from other repositories
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Biome 2.x — fast all-in-one web toolchain in Rust. Formats, lints, assists. Replaces Prettier + ESLint.
prettier-docs
Prettier 3.9.5 — opinionated code formatter. CLI, API, config, plugins, editor integration, CI.
migrate-oxlint
Guide for migrating a project from ESLint to Oxlint. Use when asked to migrate, convert, or switch a JavaScript/TypeScript project's linter from ESLint to Oxlint.
eslint-docs
ESLint 10.x — flat config, rules, plugins, formatters, parsers, CLI, Node.js API, custom rules, migration.
migrate-oxfmt
Guide for migrating a project from Prettier or Biome to Oxfmt. Use when asked to migrate, convert, or switch a JavaScript/TypeScript project's formatter from Prettier or Biome to Oxfmt.
insta-snapshots
Guide for working with and updating insta snapshot tests in Oxc without terminal interaction.