Surgical Edit

Make the smallest possible diff that satisfies the approved plan.

The rules

1. In-scope files only. Before any Edit/Write, read the plan's In-scope files list. If the target file isn't listed, stop and ask: "This file isn't in the plan. Extend scope, or is this the wrong file?"

2. In-scope functions only. Before editing within a file, read the plan's In-scope functions list. Only modify functions on that list. Adjacent functions — even if they look wrong — must not be changed.

3. No ambient cleanup. Do not reformat, rename, reorder imports, or tidy unrelated code. Even whitespace changes in unrelated regions pollute the diff.

4. No speculative refactors. "This would be cleaner if…" belongs in a separate task. Write the idea to .claude/sdlc/followups/<task-slug>.md and move on.

5. Unrelated bugs → follow-ups. Noticing a bug while working on something else is valuable. Fixing it in this change is not. Log it.

6. Prefer edit over create. New files require justification: a new module, a new test file for a new function, a new template referenced by the plan. Otherwise, extend existing files.

7. Match surrounding style. Indentation, naming, quote style, import order — mirror what's already there. This is not the place to introduce "better" conventions.

The scope-extension protocol

When you legitimately need a file or function not in the plan (you discovered something during implementation):

1. Stop editing.
2. Propose the extension: "The change requires modifying auth.py::refresh_token because validate_token depends on it. Extend scope?"
3. Wait for human approval.
4. Update the plan's in-scope list with the approved additions and a one-line reason.
5. Resume.

This preserves discipline without blocking honest discovery.

Hooks that enforce this

• hooks/diff-scope-check.sh — after each Edit/Write, runs git diff --name-only and flags any files not in the plan's in-scope list.
• hooks/adjacent-function-detector.sh — after each Edit/Write, parses the diff's function-level hunks (via git diff function context or tree-sitter per config/tools.json) and flags any functions not in the plan's in-scope list.

The hooks are deterministic. Arguing with them is not productive — either the plan is right or the plan needs updating via the scope-extension protocol.

What this skill must NEVER do

• Silently modify an adjacent function.
• Reformat a whole file.
• Introduce a new abstraction not called for in the plan.
• Combine a refactor with a behavior change in the same commit.

References

• skills/plan/SKILL.md
• hooks/diff-scope-check.sh
• hooks/adjacent-function-detector.sh