Known-positive for case 4, in a scratch copy (never this tree):
brief-validator.mjs with the BRIEF_V51_MISSING_SIGNALS check made
'if (false)'. The case still passed 3 of 3: the child read the rule in
the command prose, halted, named phase_signals, and even found the
planted 'if (false)'. So the halt alone does not show the validator
fired, and no grader checked what expected_outcome already promised
('brief-validator ... reports BRIEF_V51_MISSING_SIGNALS').
New test: case 4 needs a names-code grader reading the validator's JSON
code from the trace (same form as the intent case). Red: 1 of 10.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>