Introduction

editkit is a TypeScript toolkit for applying the edits an LLM emits to your local files. It ports aider's edit-format design to a clean public API and ships an adapter for the Vercel AI SDK, so you can stop rewriting "search/replace block parser" for the third time.

Why this exists

Every TS coding agent today (Continue, Cline, Mastra, custom AI SDK apps) ends up reinventing the same logic: take an LLM's response, find the edits inside it, and apply them to local files. Aider has the most battle-tested implementation in any language — it just happens to be Python.

editkit is that logic, in TypeScript, exported as a library.

Three edit formats

Read about the formats →

What it handles

• Indent-shift fuzzy matching — when the model dropped the indentation of a nested block, the search still locates it and the replace is re-indented to fit.
• Trailing-whitespace tolerance — finds matches when the file has trailing spaces the model didn't quote.
• Hunk drift — unified diffs locate their target even when line numbers are off.
• Overlay semantics — multiple edits to the same file see each other's output, in source order.
• Structured failures — every failure has a reason code and a model-readable message you can pipe back into a retry prompt.

Zero runtime dependencies. ESM-only. Node 18+.

Quick start

npm i editkit
# or: pnpm add editkit / bun add editkit

import { applyEdits } from "editkit";
import { readFile, writeFile } from "node:fs/promises";

const results = await applyEdits(llmOutput, async (path) => {
  return await readFile(path, "utf8");
});

for (const r of results) {
  if (r.ok) {
    await writeFile(r.path, r.after);
  } else {
    console.error(`✗ ${r.path}: ${r.message}`);
  }
}

Full getting-started guide →

Next steps

• Run a working example — three workspace packages, one runs offline with no API key.
• Recipes — ten real-world patterns: test-fix loops, bulk codemods, multi-file refactors, PR review bots, Slack bots, framework migrations, and more.
• Edit formats — when to use SEARCH/REPLACE vs unified diff vs whole-file, and the trade-offs.
• System prompts — the exact prompts aider uses, ported for you to copy.