# The Change-Log Starter (Chapter 15)

**Use when:** an artifact other people rely on starts living. The change log is the second gate: one line for every edit, forever, and the known-good copy is the only thing it diffs against.

The change log is how the reviewer answers the second question, "what changed since the last version," line by line, and how the file explains every difference between the frozen copy and the working file.

## The format, one line per edit

```
date | change | why | by
```

Filled rows, synthetic (the compliance sheet rebuild):

```
2026-08-03 | Rebuilt categories from the source log | Old sheet had merged categories that hid errors | Ana
2026-08-05 | Added the shift-variance column | The time system added the field on 8/4 | Ana
2026-08-06 | Corrected row 41 rate | Hand check against source: 18.75, not 19.75 | Ana
2026-08-06 | Froze known-good copy v3 | After signed review by Dana | Reviewer Dana signed
2026-09-01 | Recomputed one number by hand | First-Monday audit, result matched | Ana
```

## The rules

- One line per edit. The unlogged tiny fix is exactly the skip that shows up later; a wrong number found by someone else is the shape it takes.
- The known-good copy never gets edited. It only gets replaced, after a signed review, and the replacement is a change-log line.
- Every difference between the copy and the working file has a changelog line explaining it. If a difference has no line, the file is not done.
- Change it in place with the edit, not at the end of the week. A changelog written from memory is a story, not a log.

## The rhythm

Freeze the copy on a signed review. On the next first Monday, recompute one number by hand, log the result, and keep the file proving itself. The file is more checkable on Friday than it was on Monday.