# Source comments — what stays in the file and what moves to docs

Load when: writing or sweeping source-file comments, or cutting a comment whose claim belongs in a document. Not needed to write a document.

**In `docs/`, never in the file's comments** — and this skill is the half of that rule that makes it safe. A source file carries a repo-relative path header of two or three present-tense sentences and one third-person sentence above each non-obvious function; the canonical shape is the harness's `CLAUDE.md` § File Structure. That header's `docs/…` path is also the file's edge into the knowledge graph: the header pointer names the document that speaks for the file, which is how ownership is computed ([`frontmatter.md`](frontmatter.md)). What lands **here** is everything that shape displaces: design rationale, the alternatives weighed, the measurement behind a constant, the reason an obvious-looking change is wrong.

**Cutting a comment is a move, not a deletion.** A claim taken out of a source file is owed one of two things before the cut is done, and the choice is per claim, not per file:

| The claim is | What it earns |
| --- | --- |
| Worth keeping, and its doc does not state it | A section in the **owning feature doc** (the ownership index resolves which), carrying the claim and the argument for why the codebase is worse without it — never the comment's wording, which was written for a reader holding the code |
| Already stated in its doc | Nothing, once you **open that doc and find the sentence**. An assumed duplicate is how a claim is lost |
| History, a ticket or decision-record reference, a dated note, a divider, or narration of code that no longer exists | Nothing, and no record. A record lives in `docs/history/`; these are not claims about the present |

**Count what you cut, and prove the cut was only comments.** A comment sweep states comment lines before and after per file, so an unaccounted drop shows as a number. [`scripts/comment-strip.mjs`](../scripts/comment-strip.mjs) turns that from a claim into a check: it strips comments from both revisions — honouring strings, template and character literals, regex literals, raw strings and JSX comment braces — and diffs what is left, so a sweep that quietly changed executable code cannot pass as a cleanup. `comment-strip.mjs --rev <before> --to <after> <paths…>` exits 0 for "no executable code changed" and 1 naming the file and the first diverging line. Run it over any pass that touches more than a handful of files; a sweep without it is an assertion.

**The mechanical half of the shape is checked, not remembered.** [`scripts/source-lint.mjs`](../scripts/source-lint.mjs) `--changed` reports a header that names another path or none, a change whose added lines are over a quarter comments, and the four shapes the convention deletes outright — narration, ALL-CAPS emphasis, an over-long header, a comment block that has become a document. Block-severity findings must be fixed; the escape hatch is a `source-lint-disable: <id>` comment with the reason in a second comment beside it, and the only finding that legitimately takes one is a booby trap. The harness detector raises a bookkeeping row for the same condition, so an unfixed breach outlives the session that wrote it.

**Never convert a booby trap into a one-liner.** A comment whose subject is a danger on an edge that looks safe — a pinned dependency's limitation, a measurement that justifies a narrow allowlist, a two-clock interaction — is load-bearing where it sits, because the reader who needs it is mid-edit and will not go looking. Compress it if it rambles; do not relocate it. The tell is that the comment names a version, a measurement, or a condition under which it expires.