Coverage ratchet baseline dropped during v17 release preflight

[flyingrobots]

Migrated from Method backlog

GitHub Issues are now the live work tracker. Repository docs remain Method evidence.

Field	Value
Source backlog	docs/method/backlog/bad-code/SPEC_coverage-ratchet-baseline-drop.md
Archived source	docs/archive/backlog/github-issue-migration-2026-06-01/docs/method/backlog/bad-code/SPEC_coverage-ratchet-baseline-drop.md
Original lane	bad-code
Original id	SPEC_coverage-ratchet-baseline-drop
Original legend	SPEC
Original feature	tooling-release
Original release home	v19.0.0

Original backlog card

Coverage ratchet baseline dropped during v17 release preflight

Effort: L

What's Wrong

Cycle 0144-release-preflight-and-rc had to reset the global line coverage
ratchet to the current v17 full-suite baseline of 91.74% so release
preflight could honestly pass from the current branch. The previous threshold
was 95.43%, and the drop is concentrated in newer or under-exercised
surfaces such as optics, trust-chain storage, snapshot helpers, and several
type-heavy capability modules.

This is not a unit-test failure; npm run test:coverage still executes the
full unit suite successfully. The bad code is the amount of production code now
below the old coverage bar.

Suggested Fix

Run a post-v17 coverage paydown cycle that starts from
coverage/coverage-final.json, ranks low-coverage executable files by
statement count and release risk, and adds behavioral tests for the highest
value gaps first. Avoid ratcheting by vanity percentage alone; prioritize
optic/read-basis behavior, trust-chain adapter failure paths, snapshot
immutability, and current public API compatibility.