Automated Codebase Refactoring with AI Agents: TypeScript Patterns & Safety
Automated Codebase Refactoring with AI Agents: TypeScript Patterns & Safety: Designed as a zero-dependency, open-source TypeScript architecture under the MIT License with native Model Context Protocol (MCP) support and deterministic phase state machines.
- Rename exports across hundreds of files with semantic understanding
- Migrate from deprecated APIs to new versions automatically
- Enforce consistent patterns across the entire codebase in one run
- Run TypeScript compiler after each change to validate correctness
The Safe Refactoring Loop
Safe large-scale refactoring follows a validate-edit-validate cycle:
- Baseline — Run
tsc --noEmitand record the initial error count (should be 0). - Refactor — Agent edits files per the refactoring plan.
- Validate — Run
tsc --noEmitagain and verify error count hasn't increased. - Test — Run the test suite and confirm all tests still pass.
- Repeat — Continue with the next batch of files.
This loop ensures the agent never leaves the codebase in a broken state.
import { createAgent } from 'smoke-monkey-harness';const agent = createAgent({provider: 'anthropic',model: 'claude-3-7-sonnet',workspacePath: process.cwd(),autoApprove: true,});await agent.run(`We are migrating from our old fetch wrapper (src/utils/api.ts → fetchData())to the new typed client (src/lib/client.ts → apiClient.get/post/put/delete()).Steps:1. Find all usages of fetchData() across the codebase using grep.2. Replace each usage with the equivalent apiClient method.3. After every 10 files, run npx tsc --noEmit and fix any errors before continuing.4. Run npm test at the end and fix any failing tests.5. Report a summary of all changes made.`);
Common Migration Patterns
Dependency upgrades: Instruct the agent to read the migration guide for a major library version, find all usages of deprecated APIs, and update them to the new equivalents.
Naming convention enforcement: Ask the agent to rename all React components from PascalCase files to kebab-case filenames, updating all import paths accordingly.
Pattern extraction: Identify repeated inline logic (e.g., error handling boilerplate) and extract it into shared utilities, then replace all instances with calls to the new utility.
Frequently Asked Questions
Q:How do I handle refactoring that spans 500+ files?
Use the multi-agent orchestration pattern: a supervisor agent creates a file-by-file refactoring plan, then parallel worker agents process batches of 20-50 files concurrently.
Q:Can the agent handle refactoring that changes public API signatures?
Yes, but provide a clear migration contract: "function X(a: string) becomes X(options: { name: string }). Update all 47 call sites." The more explicit the contract, the more accurate the agent.
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