Apply Patch

The built-in edit_file does an exact string match on a single file and has no fuzzy tolerance. For multi-file changes, or when edit_file keeps failing to find the string, construct a unified diff and apply it atomically with git.

Procedure

1. Write the unified diff to a file in the sandbox (use write_file or a heredoc via execute):

   diff --git a/path/to/file b/path/to/file
   --- a/path/to/file
   +++ b/path/to/file
   @@ -10,7 +10,7 @@ context line
   -old line
   +new line

2. Validate before applying: git apply --check changes.patch

3. Apply: git apply changes.patch (use -p0 if paths are not a/...b/...).

4. If git apply rejects the hunk, the surrounding context is stale — read_file the exact lines again, regenerate the diff with correct context, and retry.

When to prefer this

• Editing 3+ files for one logical change (atomic, all-or-nothing).
• Repetitive or whitespace-sensitive edits where edit_file exact-match struggles.
• Re-applying a patch produced elsewhere (e.g. from a PR or git diff).

Always run the verify-changes skill afterwards.