gate: an unchecked file is not a clean file - #296
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A detector that opens a file has a third outcome besides hit and clean: input it could not read. A size cap that silently skips anything larger reports an unchecked file as clean, which is the opposite of what a guard is for. check_hook_test_coverage now requires any file-reading detector to have a test that pins its unreadable-input behavior. Fail open or fail closed stays the hook's own documented choice; leaving it untested does not. scope-lock was the one real gap the new rule found: its state file fails open and its transcript read fails closed, both now asserted. The evidence rules gain the general form, grounded in Saltzer and Schroeder's fail-safe defaults. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01KU2pPKob4MJ1NqjsfTNyYJ Change-Id: Ifa24ac4d096e44be20c30733c5beea8d9218e578
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Summary
A detector that opens a file has three possible outcomes, not two: it found the thing, it did not find the thing, or it could not read the input at all. Collapsing the third into the second is how a guard reports an unchecked file as clean.
That is not hypothetical. The first version of
ui-input-guardin this stack skipped any wrapper script over 64 KB and any path holding an unresolved shell variable, and returned "clean" for both. The user caught it in review with "why would you submit a rule or principle that would ignore files straight up".check_hook_test_coveragenow requires any file-reading detector to carry a test that pins its unreadable-input behavior. Fail open or fail closed remains the hook's own documented choice; leaving it untested does not.scope-lockwas the single real gap the new rule found across 23 hooks. Its two reads resolve in opposite directions on purpose: a corrupt state file means no lock is in force, while an unreadable transcript means no scope contract was recorded, so an existing lock is not released by a file that could not be read. Both are now asserted.Review Claim
A file-reading hook detector cannot land without a test pinning what it does with input it could not read.
Review Lane
behavior
Review Unit
tooling-policy
Safety Invariant
The gate only adds a third requirement alongside the existing positive and negative ones, and only for detectors whose source opens or sizes a file. An inline-only detector is unaffected, a missing or unreadable
detect.pymakes the new check answer no rather than raise, and the accepted test names include the fail-open vocabulary already in use, so no existing hook had to change its behavior to pass. Onescope-locktest file gained assertions; no detector logic changed.Slice Rationale
The general rule and its enforcement are separable from the hook that motivated them, and this slice is the one a future detector actually collides with.
Non-goals
Does not decide direction for anyone: the gate never asserts that a given hook must fail closed. Does not inspect what a test body proves, only that a test named for the unreadable case exists. Does not extend the same rule to skills or scripts outside
engine/hooks/.Test Plan
Test Plan
python3 -m unittest discover -s tests -p "test_check_hook_test_coverage.py"— 8 tests, OK (fires on a file-reading detector with no unreadable test, silent once one exists, silent for an inline-only detector, and asserts the real repo passes)python3 -m unittest discover -s engine/hooks/scope-lock/tests— 35 tests, OK (4 new)python3 scripts/check_hook_test_coverage.py— OK (23 hooks)python3 scripts/check_no_dated_provenance.py --base origin/main— okpython3 scripts/check_codify_has_code.py --base origin/main— okRevert Plan
Revert Plan
git revert <sha>🤖 Generated with Claude Code
https://claude.ai/code/session_01KU2pPKob4MJ1NqjsfTNyYJ