pi-extension-codex-apply-patch

Pi extension that adds Codex-style apply_patch with:

• Remote constraint: sends apply_patch as a custom freeform tool with Lark grammar to Codex Responses API
• Local constraint: parses and verifies patch format before applying filesystem changes
• Model gating: activates only for gpt-5.2-codex* and gpt-5.3-codex*
• Hard tool policy:
  • on codex models, edit and write are disabled (use apply_patch)
  • apply_patch is disabled for non-codex models
  • warning is shown when switching from codex to non-codex after apply_patch has been used in the session
• Interrupted-turn recovery: orphaned custom tool calls are auto-completed with synthetic cancellation outputs so follow-up prompts do not fail with missing custom_tool_call_output
• Codex prompt parity (patch section): injects Codex ## apply_patch instructions for codex 5.2/5.3 turns
• Live patch counters: shows streaming +X -Y path lines while patch args arrive and while hunks/files are applied
• Diff UI: apply_patch renders a colored diff using pi's native diff renderer (expand tool output to view full diff)

Install

pi install npm:pi-extension-codex-apply-patch

Or for local dev in a project:

pi install ./

How it works

1. Registers an apply_patch tool in pi
2. Enforces tool policy:
   • on codex models, removes/blocks edit and write
   • when switching back to non-codex, restores edit/write if this extension removed them
   • exposes apply_patch only on codex 5.2/5.3 models
3. Overrides the openai-codex provider stream path via registerProvider(... streamSimple ... )
4. When model is codex 5.2/5.3 family, apply_patch is sent as:
   • type: "custom"
   • grammar format (syntax: "lark")
5. Parses Codex custom_tool_call events and maps them into pi tool calls
6. Sends tool results back as custom_tool_call_output

Local patch format

Expected patch envelope:

*** Begin Patch
*** Add File: hello.txt
+Hello
*** End Patch

Supports:

• *** Add File: <path>
• *** Delete File: <path>
• *** Update File: <path> (+ optional *** Move to: <path>)
• hunks with @@ and lines prefixed by , +, -

Path behavior:

• matches pi write semantics for relative/absolute paths
• relative paths resolve against current working directory

Development

pnpm install
pnpm typecheck
pnpm test