The defect found merging S7 and P6: under P6's dedup the notice's bytes resolve to the record already on file, and the one-receipt-one- entry rule refused it only after the write-off had journaled its entry. The store now checks the deduplicated record before the journal line (`6c26160e`'s companion fix in `write_off_invoice`); this test pins it: the refusal names the record and its entry, the head and the journal are unchanged, no entry posts, the invoice stays open, and the books verify. Also formats the B-27 test `ci-fixes` brought in. Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01HS8WZziDnyxunC23MUxrLp