a formatter hook substitutes smart quotes into edited source comments which passes gofmt and every gate and is visible only in a diff

a formatter hook substitutes smart quotes into edited source comments which passes gofmt and every gate and is visible only in a diff

Reported by the itd-189 delta builder, which hit it and caught it. Writing !!str \'\' into a Go // comment came back with the straight pair replaced by a typographic quote -- inside a comment that was ABOUT YAML spellings, so the substitution silently falsified the very thing the sentence documented.

What makes it worth a major rather than a note is the detection profile. The result compiles, gofmt is silent, every gate passes, and reading the file back looks right, because the glyphs are nearly indistinguishable at a glance. Only a diff shows it. So the failure mode is a comment or a string that quietly stops saying what its author wrote, in a repository whose standing defect class this cycle is a claim asserting something that is not the case.

Scope, measured rather than assumed: grep -rP for the four curly glyphs across internal/ and cmd/ in all four worktrees finds the SAME four files in each, and all four uses are legitimate -- a regex matching a curly apostrophe in a name, a rune-index helper for curly quotes, the positioning normaliser that maps smart to straight, and a test comment using them deliberately. Nothing corrupt is committed today.

The reach is what is unknown. It fires on an editing tool's write path, so agent-authored edits are exposed and shell-authored ones (heredocs, cat) are not. Every agent this session wrote through the editing path.

Two cheap mitigations, neither implemented: a lint rule refusing the four curly glyphs in Go source outside an allow-list of the four files above, which would be armed and deterministic; and a line in agent briefs to diff their own edits before committing rather than reading them back. Same family as iss-2608301715040589, the interactive cp hazard: a machine-local property that silently breaks an otherwise correct instruction.

Grounds

• pursued: any doc comment gofmt rewrites to a typographic quote now fails go test; a curly quote landing in a Go file outside the allowlist with the suite still green would show it wrong