pi-apply-patch

Codex-style apply_patch tool extension for the pi coding agent. It registers a freeform grammar patch tool for OpenAI GPT-family models and swaps out write / edit while those models are active.

Behavior

The extension registers one LLM-callable tool: apply_patch. The tool accepts Codex patch envelopes and applies file additions, updates, deletions, and moves after resolving file paths against the current workspace.

Case	Result
OpenAI GPT provider active	replaces write and edit with apply_patch
Custom openai-responses GPT provider active	replaces write and edit with apply_patch
Non-GPT model active	restores the original write and edit toolset
Raw freeform patch input	accepted and applied
JSON { "input": "..." } patch input	accepted and applied
Absolute or parent-escaping path	accepted and resolved by Node path semantics

Tool

apply_patch

Use this tool to edit files with the Codex patch format.

*** Begin Patch
*** Add File: hello.txt
+Hello world
*** Update File: src/app.py
@@ def greet():
-print("Hi")
+print("Hello, world!")
*** Delete File: obsolete.txt
*** End Patch

Pi exposes this as a freeform grammar tool. Models with compat.supportsOpenAIGrammarTools enabled receive an OpenAI custom grammar tool; other Responses-compatible models fall back to a function tool with an input string.

Custom provider names are supported when the model id starts with gpt- and its Pi API is openai-responses or openai-codex-responses. For example, a model registered as my-proxy/gpt-5 with api: "openai-responses" activates apply_patch without adding the provider name to a hard-coded allowlist.

Installation

The package targets the pi coding agent. Pi loads extensions from ~/.pi/agent/extensions/, project .pi/extensions/, or via the --extension / -e CLI flag.

# 1. From npm (once published)
pi install npm:@code-yeongyu/pi-apply-patch

# 2. From git
pi install git:github.com/code-yeongyu/pi-apply-patch

# 3. Manual placement
git clone https://github.com/code-yeongyu/pi-apply-patch ~/.pi/agent/extensions/pi-apply-patch
cd ~/.pi/agent/extensions/pi-apply-patch && npm install

# 4. Dev / one-shot test
pi -e /path/to/pi-apply-patch/src/index.ts

After installation, restart pi or run /reload inside an interactive session.

Development

npm install
npm test
npm run typecheck
npm run check
npm pack --dry-run
pi -e ./src/index.ts

The test suite uses vitest. TypeScript is strict, Node-only, and uses ESM imports with .js suffixes.

Origin

Ported from packages/coding-agent/src/core/extensions/builtin/gpt-apply-patch.ts in code-yeongyu/senpi-mono. The patch grammar and tool descriptions mirror Codex.

License

MIT.

Related

• senpi — the fork/runtime these extensions are extracted from.
• Ultraworkers Discord — community link from the senpi README.
• Dori — the product powered by senpi under the hood.

Acknowledgements

• Mario Zechner (@badlogic) — author of pi-mono and the pi-coding-agent extension API this package targets.
• OpenAI Codex — reference apply_patch tool grammar and patch language.