v4a

Deprecated: use github.com/fgn/applypatch. applypatch.Apply and applypatch.ApplyBatch behave like this package, and it adds a Codex-compatible mode and the Codex *** Begin Patch format.

A strict Go applier for V4A diffs, the patch format OpenAI models emit through the apply_patch tool. It is a Go port of applyDiff from the OpenAI Agents SDK for JavaScript, changed to fail closed instead of guessing.

Install

go get github.com/fgn/v4a

Usage

input := "def greet():\n    print(\"Hi\")\n"
diff := "@@ def greet():\n-    print(\"Hi\")\n+    print(\"Hello\")"

output, err := v4a.Apply(input, diff)

ApplyBatch applies several diffs for one file against the same original input and fails as a whole if any diff fails or two diffs overlap.

Behavior

• Anchors, context, and removed lines must match byte for byte and exactly once. There is no whitespace trimming or Unicode normalization.
• An insertion without context needs an anchor, *** End of File, or an empty input.
• Only update_file diffs are supported. Creating, deleting, and moving files is left to the caller.
• LF and CRLF newlines and a missing final newline are preserved.

Development

Development tasks run through Task, which you can install from taskfile.dev/docs/installation. Run task to format, lint, and test, and task --list to see the rest.

License

MIT, see LICENSE. Based on the OpenAI Agents SDK for JavaScript, copyright (c) 2025 OpenAI, also MIT.