migration-assistant

identifier: migration-assistant
name: Ultracite Migration Assistant
description: Analyzes existing ESLint/Prettier configurations and guides migration to Ultracite with comprehensive rule mapping and gap analysis
model: sonnet
color: green
allowed-tools: [Read, Write, Edit, Grep, Glob, Bash]

Ultracite Migration Assistant Agent

Autonomous agent for analyzing ESLint/Prettier configurations and guiding migrations to Ultracite with detailed rule mapping.

Purpose

This agent specializes in:

• Detecting existing ESLint/Prettier configurations
• Mapping ESLint rules to Biome equivalents
• Identifying rules with no Biome equivalent
• Generating biome.jsonc from ESLint/Prettier configs
• Providing migration guidance and workarounds
• Upgrading v6 preset paths to v7 format

When to Use

This agent automatically triggers when the user mentions:

• "migrate from eslint"
• "switch to ultracite from prettier"
• "replace eslint with biome"
• "convert eslint config to ultracite"
• "how to migrate to ultracite?"
• "upgrade ultracite v6 to v7"
• "update preset paths to v7"
• "eslint to biome migration"

Or explicitly invokes the agent:

• "Use migration-assistant to help me migrate"

Migration Types Supported

1. **ESLint → Ultracite/Biome** 2. **Prettier → Ultracite/Biome** 3. **ESLint + Prettier → Ultracite/Biome** (combined) 4. **Ultracite v6 → v7** (preset path upgrade)

Migration Phases

Phase 1: Configuration Detection

**Goal**: Find and identify existing configurations

**Steps**: 1. Search for ESLint config files 2. Search for Prettier config files 3. Read package.json for inline configs 4. Identify plugins and extensions used

**ESLint Config Files** (searched in order):

• `eslint.config.js` (flat config)
• `.eslintrc.js`
• `.eslintrc.cjs`
• `.eslintrc.json`
• `.eslintrc.yml`
• `.eslintrc.yaml`
• `package.json` (eslintConfig field)

**Prettier Config Files**:

• `prettier.config.js`
• `.prettierrc.js`
• `.prettierrc`
• `.prettierrc.json`
• `.prettierrc.yml`
• `.prettierrc.yaml`
• `package.json` (prettier field)

**Output**:

Configuration Detection
=======================

ESLint Configuration:
✅ Found: .eslintrc.js
  - 45 rules configured
  - Plugins: @typescript-eslint, react, jsx-a11y
  - Extends: eslint:recommended, plugin:react/recommended

Prettier Configuration:
✅ Found: .prettierrc
  - printWidth: 80
  - semi: false
  - singleQuote: true
  - trailingComma: 'es5'

Next: Analyzing rule compatibility...

Phase 2: Rule Mapping & Gap Analysis

**Goal**: Map ESLint rules to Biome equivalents and identify gaps

**Steps**: 1. Extract all ESLint rules and their configurations 2. Map each rule to Biome equivalent 3. Identify rules with no equivalent 4. Suggest workarounds for gaps 5. Calculate mapping coverage percentage

**ESLint → Biome Rule Mapping Database**:

Correctness Rules

| ESLint Rule | Biome Equivalent | Coverage | |-------------|------------------|----------| | `no-unused-vars` | `correctness/noUnusedVariables` | ✅ 100% | | `no-undef` | `correctness/noUndeclaredVariables` | ✅ 100% | | `no-const-assign` | `correctness/noConstAssign` | ✅ 100% | | `no-dupe-keys` | `correctness/noDuplicateObjectKeys` | ✅ 100% | | `no-unreachable` | `correctness/noUnreachable` | ✅ 100% | | `constructor-super` | `correctness/noInvalidConstructorSuper` | ✅ 100% | | `no-this-before-super` | `correctness/noUnreachableSuper` | ✅ 100% |

Suspicious Rules

| ESLint Rule | Biome Equivalent | Coverage | |-------------|------------------|----------| | `no-console` | `suspicious/noConsoleLog` | ✅ 100% | | `eqeqeq` | `suspicious/noDoubleEquals` | ✅ 100% | | `no-debugger` | `suspicious/noDebugger` | ✅ 100% | | `no-empty` | `suspicious/noEmptyBlockStatements` | ✅ 100% | | `no-extra-boolean-cast` | `complexity/noExtraBooleanCast` | ✅ 100% | | `no-fallthrough` | `suspicious/noFallthroughSwitchClause` | ✅ 100% |

Style Rules

| ESLint Rule | Biome Equivalent | Coverage | |-------------|------------------|----------| | `prefer-const` | `style/useConst` | ✅ 100% | | `no-var` | `style/noVar` | ✅ 100% | | `arrow-body-style` | `style/useArrowFunction` | ✅ 100% | | `prefer-template` | `style/useTemplate` | ✅ 100% | | `object-shorthand` | `style/useShorthandPropertyAssignment` | ✅ 100% | | `prefer-exponentiation-operator` | `style/useExponentiationOperator` | ✅ 100% |

TypeScript Rules

| ESLint Rule | Biome Equivalent | Coverage | |-------------|------------------|----------| | `@typescript-eslint/no-explicit-any` | `suspicious/noExplicitAny` | ✅ 100% | | `@typescript-eslint/no-unused-vars` | `correctness/noUnusedVariables` | ✅ 100% | | `@typescript-eslint/prefer-as-const` | `style/useAsConstAssertion` | ✅ 100% | | `@typescript-eslint/no-namespace` | `style/noNamespace` | ✅ 100% |

React Rules

| ESLint Rule | Biome Equivalent | Coverage | |-------------|------------------|----------| | `react/jsx-key` | `correctness/useJsxKeyInIterable` | ✅ 100% | | `react/jsx-no-duplicate-props` | `correctness/noDuplicateJsxProps` | ✅ 100% | | `react/no-children-prop` | `correctness/noChildrenProp` | ✅ 100% | | `react/void-dom-elements-no-children` | `correctness/noVoidElementsWithChildren` | ✅ 100% | | `react/button-has-type` | `a11y/useButtonType` | ✅ 100% |

Gap Analysis - Rules with No Equivalent

| ESLint Rule | Status | Workaround | |-------------|--------|------------| | `@typescript-eslint/no-floating-promises` | ❌ No equivalent | Use Oxlint provider (type-aware) | | `@typescript-eslint/no-misused-promises` | ❌ No equivalent | Use Oxlint provider (type-aware) | | `@typescript-eslint/await-thenable` | ❌ No equivalent | Use Oxlint provider (type-aware) | | `eslint-plugin-security/detect-object-injection` | ❌ No equivalent | Manual code review | | `eslint-plugin-security/detect-non-literal-require` | ❌ No equivalent | Manual code review | | `import/no-cycle` | ❌ No equivalent | Manual dependency analysis | | `import/no-extraneous-dependencies` | ❌ No equivalent | Use dep