Lint Sync

Purpose

Two workflows in one skill:

Migrate — Move ESLint/Prettier rules to Biome or Oxc with rule-by-rule comparison
Modernize — Update existing Biome/Oxc configs: promote nursery rules, enable new quality flags, apply latest formatter options

When to Use This Skill

Trigger phrases: "lint sync", "lint-sync", "eslint biome overlap", "biome migration", "oxlint migration", "migrate to oxc", "disable eslint rules", "modernize biome config", "update biome rules", "promote nursery rules", "update oxlint config"

Modes

Mode	Trigger	Description
sync	No mode or `sync`	Quick overlap check (migrate) or nursery/feature check (modernize).
audit	`audit`	Full analysis with performance data, coverage stats, migration/modernization checklist.
update	`update`	Refresh mapping and version reference files from upstream sources.

Documentation

Before fetching docs from the web, check

references/docs.md

for Context7 library IDs and direct URLs. This saves tokens significantly.

Context7 IDs for quick lookups:

Biome:
```
/biomejs/website
```
(5357 snippets)
Oxc:
```
/oxc-project/website
```
(5057 snippets)
Vite+:
```
/websites/viteplus_dev
```
(210 snippets)

Asking the User

Every question in this skill is written as

AskUserQuestion

options. Use that tool where the host offers it, or the host's nearest structured-choice equivalent. Where the host has neither, ask the same question in normal chat as a numbered list of 2–5 options — recommended first, one short line of description each — and wait for the user to reply with a number.

Workflow

Step 1: Detect All Configs

Find all relevant configuration files:

bash

# Source tools (ESLint / Prettier)
fd -t f '(eslint\.config\.(js|ts|mjs|cjs)|\.eslintrc\..*)' --max-depth 2
fd -t f '(\.prettierrc(\.(js|cjs|mjs|json|yaml|yml|toml))?|prettier\.config\.(js|cjs|mjs|ts))' --max-depth 2

# Target tools (Biome / Oxc)
fd -t f 'biome\.json(c)?$' --max-depth 2
fd -t f '(\.oxlintrc\.(json|jsonc)|oxlint\.config\.(ts|js))' --max-depth 2
fd -t f '(\.oxfmtrc\.(json|jsonc)|oxfmt\.config\.(ts|js))' --max-depth 2

# Vite+ (unified Oxc config)
fd -t f 'vite\.config\.(ts|js|mjs)$' --max-depth 2

Vite+ detection: If

vite.config.ts

exists, check if it imports from

'vite-plus'

. Also check

package.json

for

vite-plus

in dependencies. If Vite+ is in use, its

lint

and

fmt

blocks in

vite.config.ts

replace standalone

.oxlintrc.json

and

.oxfmtrc.json

. Set

$VITEPLUS=true

and treat Oxc config as found.

bash

# Quick Vite+ detection
grep -l "from ['\"]vite-plus['\"]" vite.config.ts 2>/dev/null

Step 2: Determine Workflow

ESLint/Prettier	Biome	Oxc/Vite+	Workflow
Found	Found	-	Migrate to Biome
Found	-	Found	Migrate to Oxc
Found	Found	Found	Ask user which target
Found	-	-	Ask user which target to migrate to
-	Found	-	Modernize Biome
-	-	Found	Modernize Oxc
-	Found	Found	Modernize both (ask which first)
-	-	-	Nothing to do — inform user

Vite+ counts as Oxc in the table above. When

$VITEPLUS=true

, all Oxc config reads/writes target the

lint

and

fmt

blocks in

vite.config.ts

instead of standalone config files.

Ask the target choice per Asking the User:

Which tool would you like to migrate to?
1. Biome (Recommended) — All-in-one linter + formatter, single config file
2. Oxc (Oxlint + Oxfmt) — Separate linter and formatter, ESLint-compatible rule names
3. Skip — Don't migrate, just show the analysis

Migration Workflow

Runs when ESLint/Prettier configs are present.

M1: Get Tool Versions

bash

pnpm exec eslint --version 2>/dev/null || npx eslint --version 2>/dev/null

# Target-specific
pnpm exec biome --version 2>/dev/null || npx biome --version 2>/dev/null
# or
pnpm exec oxlint --version 2>/dev/null || npx oxlint --version 2>/dev/null
pnpm exec oxfmt --version 2>/dev/null || npx oxfmt --version 2>/dev/null

Read the appropriate mapping and check version staleness:

Biome:

references/biome-eslint-mapping.json

→

_meta.biomeVersion

Oxc:

references/oxc-eslint-mapping.json

→

_meta.oxlintVersion

Compare installed version against

_meta

version. If installed is newer, warn that mappings may be stale and suggest running

update

mode.

M2: Gather Active Rules

bash

bash scripts/get-eslint-rules.sh
bash scripts/get-biome-rules.sh   # or get-oxlint-rules.sh

If a script fails, fall back to reading configs manually.

M3: Load References

bash

cat references/biome-eslint-mapping.json   # or oxc-eslint-mapping.json
cat references/type-aware-rules.json

For Oxc, also load

references/oxc-defaults.json

M4: Cross-Reference (Core Analysis)

For each active ESLint rule, classify it:

Category	Meaning	Action
DISABLE	Target has "same" equivalent AND it's active	Safe to turn off in ESLint
REVIEW	Target has "inspired" equivalent AND it's active	Check behavior before disabling
ENABLE_TARGET	Target has equivalent but it's NOT active	Can switch by enabling in target config
ESLINT_ONLY	No target equivalent exists	Must keep in ESLint
TYPE_AWARE	Requires TypeScript type info	Expensive; check if target supports it

Biome classification:

for each active ESLint rule:
  1. Look up in biome-eslint-mapping.json
     - Resolution: exact → "eslint-plugin-" prefix → scoped (@scope/rule)
     - Core ESLint rules match directly: "no-debugger"
  2. No mapping → check type-aware-rules.json → TYPE_AWARE or ESLINT_ONLY
  3. Mapping exists:
     a. Check if Biome rule is active (match by RULE NAME only, not category)
     b. Active + "same" → DISABLE
     c. Active + "inspired" → REVIEW
     d. Not active → ENABLE_TARGET

Oxc classification:

for each active ESLint rule:
  1. Look up in oxc-eslint-mapping.json (same resolution order)
  2. No mapping → TYPE_AWARE (if in type-aware list) or ESLINT_ONLY
     - Oxlint supports type-aware rules via tsgolint (check "typeAware" field)
  3. Mapping exists:
     a. Check if active; all Oxlint mappings are "same" relationship
     b. Active → DISABLE
     c. Not active → ENABLE_TARGET

M5: Prettier Migration Analysis

If Prettier config found:

Biome: Map Prettier options → Biome equivalents (see table in

references/docs.md

). Note:

biome migrate prettier --write

automates this.

Oxc: Oxfmt uses Prettier-compatible option names. Key differences:

```
printWidth
```
defaults to
```
100
```
(Prettier:
```
80
```
)
```
endOfLine: "auto"
```
not supported

Built-in:

sortImports

sortTailwindcss

sortPackageJson

Note:

oxfmt --migrate=prettier

automates this.

Import sorting (both targets): Check if the project uses

eslint-plugin-import

sort rules,

@trivago/prettier-plugin-sort-imports

prettier-plugin-organize-imports

, or

@ianvs/prettier-plugin-sort-imports

. If so, recommend enabling the native import sorter:

Biome:

"organizeImports": { "enabled": true }

biome.json

Oxfmt:
```
"sortImports": { ... }
```
(see defaults in
```
oxc-defaults.json
```
)

Tailwind class sorting (both targets): Check if

tailwindcss

is in project deps. If so, and if

prettier-plugin-tailwindcss

was in use, recommend enabling native sorting:

Biome: not built-in — keep the Prettier plugin or use
```
biome-plugin-tailwindcss
```
if available

Oxfmt:

"sortTailwindcss": { ... }

built-in (see

oxc-defaults.json

→

oxfmt_ifTailwind

)

M6: Oxc Config Initialization (Oxc Only)

If no Oxc config exists, offer to create from

references/oxc-defaults.json

Before writing config, check project dependencies:

bash

# Check for React
jq -r '.dependencies.react // .devDependencies.react // empty' package.json
# Check for Tailwind CSS
jq -r '.dependencies.tailwindcss // .devDependencies.tailwindcss // empty' package.json

Config assembly from defaults:

Always:
```
categories
```
,
```
rules
```
,
```
env
```
,
```
options
```
from
```
oxlint
```
section

Always:

plugins.always

(

eslint

typescript

unicorn

oxc

import

)

If React in deps: add
```
plugins.ifReact
```
(
```
react
```
,
```
react-hooks
```
,
```
jsx-a11y
```
)
Oxfmt:
```
singleQuote
```
,
```
sortImports
```
from
```
oxfmt
```
section
If Tailwind in deps: merge
```
oxfmt_ifTailwind
```
→ enables
```
sortTailwindcss
```
with class sorting for
```
className
```
,
```
class
```
, and common helpers (
```
clsx
```
,
```
cn
```
,
```
cva
```
,
```
tw
```
,
```
twMerge
```
,
```
twJoin
```
)

Vite+ projects (
$VITEPLUS=true
): Write into

vite.config.ts

lint

and

fmt

blocks. Do NOT create standalone config files. Example:

typescript

import { defineConfig } from 'vite-plus';

export default defineConfig({
  lint: {
    categories: { correctness: 'error', suspicious: 'warn', perf: 'warn' },
    plugins: ['eslint', 'typescript', 'unicorn', 'oxc', 'import', 'react', 'react-hooks', 'jsx-a11y'],
    rules: {
      'no-console': 'warn',
      'eqeqeq': 'error',
      'import/no-cycle': 'error',
    },
    options: { typeAware: true, typeCheck: true },
  },
  fmt: {
    singleQuote: true,
    sortImports: { ignoreCase: true, order: 'asc', newlinesBetween: true },
    sortTailwindcss: { functions: ['clsx', 'cn', 'cva', 'tw'] }, // if Tailwind
  },
});

Standalone Oxc projects: Write

.oxlintrc.json

and

.oxfmtrc.json

M7: Performance Analysis (Audit Mode Only)

bash

TIMING=1 pnpm exec eslint 'src/**/*.{ts,tsx}' 2>&1 | tee "$SCRATCHPAD/eslint-timing.txt"

Cross-reference slowest rules against mapping and type-aware list.

M8: Generate Migration Report

See Report Templates below.

Modernize Workflow

Runs when no ESLint/Prettier configs exist but Biome and/or Oxc configs are present.

N1: Read Current Config

Read and parse the tool's config file:

Biome:
```
biome.json
```
or
```
biome.jsonc
```
Oxc standalone:
```
.oxlintrc.json
```
and
```
.oxfmtrc.json
```
Vite+ (
```
$VITEPLUS=true
```
): parse
```
lint
```
and
```
fmt
```
blocks from
```
vite.config.ts
```

N2: Get Installed Version

bash

pnpm exec biome --version 2>/dev/null || npx biome --version 2>/dev/null
# or
pnpm exec oxlint --version 2>/dev/null || npx oxlint --version 2>/dev/null

N3: Load Version History

bash

cat references/biome-versions.json   # or oxc-versions.json

Determine which versions the user has passed through since their config was last updated. Use the installed version to find applicable changes.

N4: Check Nursery Promotions (Biome)

Scan the user's config for any rules referencing

nursery/

category. Cross-reference against

biome-versions.json

→

promotedFromNursery

entries for the installed version and all prior tracked versions.

For each stale nursery reference found:

Current (stale)	Should be	Promoted in
`nursery/noConsole`	`suspicious/noConsole`	v2.4
`nursery/noSecrets`	`security/noSecrets`	v2.3

Generate a ready-to-apply diff or config patch.

N5: Suggest New Quality Rules

Biome: Check

biome-versions.json

for

newRules

in versions newer than user's mapping date. Highlight rules that are:

Promoted to stable (non-nursery) — safe to enable

Commonly useful (e.g.,

noUnusedExpressions

noImportCycles

noFloatingPromises

)

New formatter options (e.g.,
```
trailingNewline
```
in v2.4)

Oxc: Check

oxc-versions.json

for

recommendedConfig

rules not yet in user's config. Suggest:

Categories worth enabling (
```
suspicious
```
,
```
perf
```
)

High-value rules from

oxc-versions.json

→

recommendedConfig.rules

New features (type-aware linting, Vue support, config extends)

N6: Suggest New Formatter Options and Sorting

Check project dependencies first:

bash

jq -r '.dependencies.tailwindcss // .devDependencies.tailwindcss // empty' package.json

Biome: Check

biome-versions.json

for

newFormatterOptions

. Highlight useful additions:

```
formatter.trailingNewline
```
(v2.4)
```
formatter.lineEnding: "auto"
```
(v2.3)
```
formatter.expand
```
for array/object control
```
organizeImports.enabled: true
```
if not already on — replaces import-sort plugins
Note: Biome does not have built-in Tailwind class sorting

Oxc/Vite+: Check if Oxfmt features are underutilized:

```
sortImports
```
(off by default, high value — replaces import-sort plugins)

sortTailwindcss

(if Tailwind in deps — replaces

prettier-plugin-tailwindcss

)

```
jsdoc
```
formatting (off by default)

For Vite+:

lint.options.typeAware

and

lint.options.typeCheck

(recommended on)

N7: Generate Modernize Report

markdown

## Modernize Report

### Environment
- Tool: Biome vX.x / Oxlint vX.x / Vite+ vX.x
- Config: biome.json / .oxlintrc.json / vite.config.ts (lint + fmt)
- Reference version: X.x (installed: Y.y)

### Nursery Promotions (Biome)
X rules in your config still reference nursery/ but have been promoted:

| Current | Updated | Version |
|---------|---------|---------|
| `nursery/noSecrets` | `security/noSecrets` | v2.3 |

### New Rules Available
These rules are stable and recommended but not in your config:

| Rule | Category | Description |
|------|----------|-------------|
| `noImportCycles` | suspicious | Detect circular imports |

### New Formatter Options
| Option | Value | Since |
|--------|-------|-------|
| `trailingNewline` | `true` | v2.4 |

### Ready-to-Apply Config Patch
(JSON diff to paste into config)

Update Workflow

Refreshes all reference files from upstream.

U1: Update biome-eslint-mapping.json

Fetch

https://biomejs.dev/linter/rules-sources/

Parse ESLint → Biome rule mappings
Diff against existing, show added/removed
Update
```
_meta.biomeVersion
```
and
```
_meta.updatedAt
```

U2: Update oxc-eslint-mapping.json

Fetch

https://oxc.rs/docs/guide/usage/linter/rules

Parse supported rules by plugin
Diff against existing, show added/removed
Update
```
_meta.oxlintVersion
```
and
```
_meta.updatedAt
```

U3: Update type-aware-rules.json

bash

gh api repos/typescript-eslint/typescript-eslint/contents/packages/eslint-plugin/src/configs/flat/disable-type-checked.ts --jq '.content' | base64 -d

Parse, diff, update

_meta.updatedAt

U4: Update version files

Check Biome and Oxc changelogs for new versions not yet tracked:

Biome:
```
https://biomejs.dev/blog/
```
— look for new
```
biome-vX-Y
```
posts
Oxc:
```
https://oxc.rs/blog/
```
— look for new release posts

For each new version found, add entry to

biome-versions.json

oxc-versions.json

with:

Promoted rules
New rules
New formatter options
New features

Report Templates

Sync Mode (Migration)

markdown

## Lint Sync Report

### Environment
- ESLint: vX.x (flat/legacy config)
- Target: Biome vX.x / Oxlint vX.x + Oxfmt vX.x
- Mapping version: YYYY-MM-DD (current / stale)
- Prettier config: found / not found

### Summary
| Category | Count |
|----------|-------|
| DISABLE (safe to remove) | X |
| REVIEW (check before removing) | X |
| ENABLE_TARGET (can migrate) | X |
| ESLINT_ONLY (must keep) | X |
| TYPE_AWARE | X |

### DISABLE — Safe to Turn Off in ESLint
| ESLint Rule | Target Equivalent |
|-------------|------------------|

### REVIEW — Check Before Disabling
| ESLint Rule | Target Equivalent | Notes |
|-------------|------------------|-------|

### ENABLE_TARGET — Available to Migrate
| ESLint Rule | Target Equivalent | Relationship |
|-------------|------------------|--------------|

### ESLINT_ONLY — Must Keep
| ESLint Rule | Type-Aware? |
|-------------|-------------|

### Prettier Migration (if applicable)
| Prettier Option | Current Value | Target Option | Target Default | Action |
|----------------|--------------|--------------|----------------|--------|

### Ready-to-Paste Config

Audit Mode (adds to Sync)

markdown

### Performance Analysis

#### Top 10 Slowest Rules
| Rule | Time (ms) | Type-Aware? | Target Equivalent? |
|------|-----------|-------------|-------------------|

#### Coverage Statistics
- Total active ESLint rules: X
- Covered by target: X (Y%)
- ESLint-only: X (Y%)
- Type-aware: X (Y%)

#### Migration Checklist
- [ ] Disable X covered rules
- [ ] Review X "inspired" rules (Biome)
- [ ] Enable X additional target rules
- [ ] Migrate Prettier config
- [ ] Run both linters and compare output

Important Notes

Scripts require the respective tools installed in the project
Scripts auto-detect the package manager (pnpm/yarn/bun/npm)
Version files track which Biome/Oxc versions introduced which changes
Modernize workflow uses version files to detect stale nursery refs and suggest new features
For doc lookups, use Context7 IDs from
```
references/docs.md
```
before web search
Vite+ projects embed Oxlint/Oxfmt config in
```
vite.config.ts
```
(
```
lint
```
/
```
fmt
```
blocks) — do not create standalone
```
.oxlintrc.json
```
/
```
.oxfmtrc.json
```
alongside Vite+
External repos accessed:
```
typescript-eslint/typescript-eslint
```
(public)

Bundled References

```
references/biome-eslint-mapping.json
```
— ESLint → Biome rule mapping (~260 entries)
```
references/oxc-eslint-mapping.json
```
— ESLint → Oxlint rule mapping (~520 entries)
```
references/biome-versions.json
```
— Biome version changelog: promotions, new rules, new options
```
references/oxc-versions.json
```
— Oxc version changelog: new rules, features, recommended config
```
references/oxc-defaults.json
```
— Opinionated Oxlint/Oxfmt defaults for initialization
```
references/type-aware-rules.json
```
— TypeScript-ESLint type-aware rules (~60 entries)
```
references/docs.md
```
— Context7 library IDs and documentation URLs

scripts/get-eslint-rules.sh

— Extract active ESLint rules via

--print-config

scripts/get-biome-rules.sh

— Extract active Biome rules via

biome rage --linter

```
scripts/get-oxlint-rules.sh
```
— Extract active Oxlint rules

lint-sync

NPX Install

Tags

SKILL.md Content

Lint Sync

Purpose

When to Use This Skill

Modes

Documentation

Asking the User

Workflow

Step 1: Detect All Configs

Step 2: Determine Workflow

Migration Workflow

M1: Get Tool Versions

M2: Gather Active Rules

M3: Load References

M4: Cross-Reference (Core Analysis)

M5: Prettier Migration Analysis

M6: Oxc Config Initialization (Oxc Only)

M7: Performance Analysis (Audit Mode Only)

M8: Generate Migration Report

Modernize Workflow

N1: Read Current Config

N2: Get Installed Version

N3: Load Version History

N4: Check Nursery Promotions (Biome)

N5: Suggest New Quality Rules

N6: Suggest New Formatter Options and Sorting

N7: Generate Modernize Report

Update Workflow

U1: Update biome-eslint-mapping.json

U2: Update oxc-eslint-mapping.json

U3: Update type-aware-rules.json

U4: Update version files

Report Templates

Sync Mode (Migration)

Audit Mode (adds to Sync)

Important Notes

Bundled References