eslint

name	eslint
description	ESLint 10 — JS/TS linter with flat config, typescript-eslint, framework plugins, Prettier/Biome coexistence. Use when: eslint, eslint.config.js, eslint.config.ts, flat config, typescript-eslint, eslint-plugin-react, eslint-plugin-vue, next/core-web-vitals, @nuxt/eslint, eslint-config-prettier, .eslintrc migration, custom rules, eslint --fix, --cache, lint-staged. SKIP: Biome-only projects (→biome), Prettier-only formatting, Standard JS, dprint.
stacks	["lint-format"]
packages	["eslint","typescript-eslint","@eslint/js"]
tags	["eslint","lint","flat-config","javascript","typescript","dx"]
source	vechkasov-global-skills
risk	medium-stakes

🎯 Version Requirements (May 2026)

Primary pins:

• ESLint: 10.x
• TypeScript: 6.0.x

Source of truth: STACK_VERSIONS.md — verified 2026-05-16

Usage

Loaded automatically when its description matches the active task. Read only the section you need, then follow the link to the relevant reference file for full detail.

Use this skill when

• Configuring ESLint 10 from scratch with flat config (eslint.config.js / eslint.config.ts)
• Migrating an existing project from .eslintrc.* legacy config to flat config (@eslint/migrate-config or manual)
• Wiring typescript-eslint (parser + plugin) with type-aware rules (parserOptions.projectService)
• Adding framework plugins: eslint-plugin-react, eslint-plugin-react-hooks, eslint-plugin-vue, eslint-plugin-jsx-a11y, @next/eslint-plugin-next, @nuxt/eslint
• Layering next/core-web-vitals or @nuxt/eslint-config on top of @eslint/js recommended
• Coexisting with Prettier via eslint-config-prettier (turn off conflicting style rules)
• Coexisting with Biome (ESLint handles framework rules, Biome handles format + base lint)
• Setting up eslint --fix, eslint --cache, and incremental lint in CI
• Configuring editor integration (VS Code dbaeumer.vscode-eslint, JetBrains)
• Writing custom rules or sharing config across a monorepo
• Investigating "Parsing error", "no-undef on TypeScript", or tsconfig.json include mismatches

Do not use this skill when

• The project uses Biome as the single linter/formatter with no ESLint — use biome
• The task is Prettier-only formatting (no ESLint involved) — handled as cascade dep of eslint or skip
• The task is TypeScript type-checking (tsc --noEmit) — that is typescript
• The task is dprint, Standard JS, or XO — different tools
• The task is ESLint plugin authoring at the AST level for a niche rule — load this skill but expect to also load typescript for AST/typing detail

Purpose

ESLint 10 is the mainstream JavaScript/TypeScript linter when Biome's rule set is insufficient — specifically when a project needs React, Vue, Next.js, Nuxt, Storybook, jsx-a11y, or custom-authored rules that have no Biome equivalent. Flat config (eslint.config.js) is the only supported config format in v10; legacy .eslintrc.* has been removed.

This skill covers the full ESLint 10 lifecycle: flat config authoring (JS or TS), typescript-eslint integration, framework plugin composition, Prettier coexistence, migration from v8/v9 .eslintrc, CI integration with caching, and editor setup. It hands off to biome for projects that have already adopted Biome end-to-end, and to typescript for type-system questions.

What this skill does NOT do: Biome configuration, Prettier-only formatting, or tsc type-checking.

Capabilities

Each line below points to the canonical reference. The reference owns code, edge cases, and gotchas.

• Flat config — array of config objects, no extends (composition via spread). eslint.config.ts supported natively in v10 (no tsx/ts-node needed). defineConfig helper from eslint/config for type-safe definition. → references/flat-config.md
• Recommended rules — three baseline presets: js.configs.recommended + tseslint.configs.recommended (or recommendedTypeChecked) + framework preset. → references/recommended-rules.md
• typescript-eslint — tseslint.config() helper; use parserOptions.projectService: true (NOT legacy project: "./tsconfig.json"); requires tsconfigRootDir: import.meta.dirname in monorepos. → references/typescript-eslint.md
• Framework plugins — React (eslint-plugin-react + react-hooks), Vue (eslint-plugin-vue flat), Next (next/core-web-vitals), Nuxt (@nuxt/eslint module-generated), a11y (eslint-plugin-jsx-a11y). → references/framework-plugins.md
• Prettier coexistence — eslint-config-prettier LAST in array; NEVER eslint-plugin-prettier (slow, noisy). → references/prettier-coexistence.md
• Migration v8 → 10 — npx @eslint/migrate-config .eslintrc.json generates eslint.config.js; manually review plugins/extends/overrides. ESLint 10 removed legacy config entirely. → references/migration-from-v8.md
• CI — eslint . --max-warnings 0 --cache --cache-location node_modules/.cache/eslint; restore cache between runs. → references/ci-integration.md
• Editor — dbaeumer.vscode-eslint extension; eslint.useFlatConfig: true (default in recent versions); editor.codeActionsOnSave.source.fixAll.eslint: explicit. → references/editor-integration.md
• Biome coexistence — Biome format + base lint; ESLint for framework rules with no Biome equivalent. Use eslint-config-prettier at end to neutralise style rules duplicated by Biome's formatter. → references/prettier-coexistence.md

Behavioral Traits

• Defaults to eslint.config.ts (typed config) over eslint.config.js when the project already uses TypeScript
• Always pins eslint, typescript-eslint, and @eslint/js together — version drift between them causes obscure errors
• Uses projectService: true over the legacy project: field for type-aware linting
• Puts eslint-config-prettier last in the array — order matters, it must override earlier style rules
• Adds --cache to every eslint invocation in CI and pre-commit
• Prefers tseslint.config() helper over hand-spreading arrays — gives type safety and better error messages
• Scopes type-aware rules to **/*.{ts,tsx} via files glob — avoids parsing .js files with TS parser
• Treats next/core-web-vitals as the source of truth for Next.js — does not override its rules without justification
• Does not run Prettier through ESLint (eslint-plugin-prettier is anti-pattern in 2026)

Important Constraints

• NEVER mix .eslintrc.* and eslint.config.js in the same project — ESLint 10 ignores legacy config entirely
• NEVER use eslint-plugin-prettier — slow, noisy diagnostics; use eslint-config-prettier only
• NEVER omit tsconfigRootDir when using projectService — relative path resolution fails in monorepos
• NEVER lint generated files (dist/, .next/, node_modules/) — always ignores them at the top of the config
• ALWAYS run eslint --fix before committing — catches auto-fixable rule violations
• ALWAYS scope React/Vue plugin configs with files: ["**/*.{jsx,tsx}"] or ["**/*.vue"] — avoid parsing every file with framework parsers
• NEVER add eslint-plugin-import for module resolution in 2026 — typescript-eslint's consistent-type-imports and TypeScript's verbatimModuleSyntax cover the same ground faster
• ALWAYS verify typescript-eslint major version matches the typescript major version range it supports

Related Skills

90%-filter applied — cascade markers for mainstream stacks only.

Language / type-checking

• ✓ typescript — TS type system (ESLint enforces style + bug-class rules, tsc does type-check)

Framework cascades (ESLint plugins live here)

• ✓ react — React 19 + eslint-plugin-react-hooks
• ✓ nextjs — Next.js 16 + next/core-web-vitals
• ✓ vue — Vue 3.5 + eslint-plugin-vue
• ✓ nuxt — Nuxt 4 + @nuxt/eslint

Runtime / tooling

• ✓ nodejs — Node.js 24 (runtime for ESLint binary, hooks)

Alternative

• ✓ biome — Biome 2 (faster all-in-one alternative; common partial-coexistence pattern)

Cascade markers (loaded only if active)

• prettier — formatting peer (use eslint-config-prettier)

API Reference

Domain-specific references (Pattern 2) — load only what's relevant:

Topic	File
Index, decision map, CLI quick-lookup	references/REFERENCE.md
Flat config (eslint.config.js / eslint.config.ts) full reference	references/flat-config.md
Recommended rule presets and severity tuning	references/recommended-rules.md
typescript-eslint parser + plugin + type-aware rules	references/typescript-eslint.md
Framework plugins: React, Vue, Next.js, Nuxt, jsx-a11y	references/framework-plugins.md
Prettier coexistence via eslint-config-prettier	references/prettier-coexistence.md
Migration from v8 .eslintrc.* to flat config	references/migration-from-v8.md
CI integration: GitHub Actions, caching, --max-warnings	references/ci-integration.md
Editor integration: VS Code, JetBrains, format-on-save	references/editor-integration.md
Eval cases (routing tests) — positive/negative/edge prompts	references/eval-cases.md

Templates

Production-ready configs — copy and adjust:

Template	File
eslint.config.ts — TS strict + React + typescript-eslint	templates/eslint.config.react.ts.template
eslint.config.ts — Node.js backend (no React)	templates/eslint.config.node.ts.template
package.json lint/CI scripts	templates/package.json.scripts.json

Examples

Scenario	File
Full migration walkthrough: .eslintrc.json → eslint.config.ts	examples/migrate-eslintrc-to-flat.md

How to use: navigate to the specific file for the topic you need. Don't read all files — look up only what's relevant to the current task.