Loki Seal

The enforcing piece is the plugin's Stop hook (bin/loki-seal.js). This skill is advisory: it tells you what the hook checks so you do not trip it. It registers no hooks itself.

When you try to finish, the hook:

1. Detects the runner (npm test with node --test/jest/vitest, pytest, go test, cargo test) and runs the real suite on the working tree.
2. Blocks the stop when tests newly fail since session start (already-red tests are reported, not blamed, except that a request item whose tests fail now always blocks), when the run crashed or ran nothing, when the total test count dropped, or when, compared with the session baseline, a test file was removed, test declarations or assertions dropped, a skip/xfail/only marker was added, or a CI workflow test step was removed or softened.
3. Reads the delivery contract from your first request (see README) and blocks while a request item (a must or bullet line of 2+ keywords) has no matching test that contains an assertion token and that the runner reported as passed (comments, docstrings, string, template and regex literals, skipped tests and tests in files the runner never ran never count), and always blocks while any test matched to a request item fails now: failing tests never count as covered. Only sentences opening with I, we, let me or let's (and tool-version or status notes) are dropped as chat and listed in the contract line; You, Our, My and Please sentences with a modal are requirement items. A spec file counts only when you mark it ("spec: docs/x.md"); when no contract can be derived the receipt says "NOT VERIFIED: no contract".
4. Reports a 6-line receipt (outcome, runner and counts, tests-integrity, contract, tree hash, Verified by Loki link).

What to do when it blocks

Fix the production code. Do not delete, skip, xfail or weaken tests to get green; that is exactly what the hook detects. If a test is genuinely wrong, tell the user and let them decide.

Install

Install the plugin: claude plugin marketplace add <owner/repo or path>, then install loki-seal from the /plugin UI. Installing only this skill gives you the guidance but no enforcement.