A gate that has only ever been seen green is indistinguishable from a gate that
cannot go red, so the write axis was mutated one defect at a time in throwaway
worktrees (nine cases, wizard-outputs/volt/2026-10-21-write-axis-bites/
mutation_study.py). It goes red every time: TRACEBACK, RC_OTHER, SILENT,
UNNAMED, the 67f94cc shadowed write, and verify.py's own write-axis leg -- while
the clean control stays green 21/21.
The study found two things this commit fixes and one it only states.
FIXED 1 -- the detail line on a red write-axis leg named a healthy tool. Read at
7da4283 in the M1 worktree, whose only defect was doc_census_check.py, verify.py
printed `FAULT: append_only_audit.py OK 2 cannot write --json ...`: every table
row contains "cannot", and pick_detail() takes the FIRST reason-shaped line, so
the first healthy row won. write_probe.py now prints a `FAULT <tool> ...` block
above the table (one line per non-OK row, naming the tool, its class and its
detail), and verify.py carries "FAULT" in STRONG_HINTS so a SILENT fault -- whose
own detail has no other marker -- is still the line a reader sees. Cell c11
grades the block: selftest 10 -> 11 cells, 11/11 rc 0.
FIXED 2 -- doc_command_check.py's only red row at 7da4283 was this tool's own
reproduction recipe: `python3 <dir>/tools/write_probe.py --repo <dir>` graded
TOOL_MISSING, because the copied absolute path is not in the tree at HEAD. The
recipe now reads `cd <dir> && python3 tools/write_probe.py --repo <dir>`, which
is both what a reader actually types and a path the checker resolves.
STATED, NOT CHANGED -- UNNAMED grades the TEXT, not the guard's sentence. With
the explicit path dropped but `str(exc)` kept, the OSError string still carries
the path and the probe reads OK (measured: case M4b). The docstring now says so,
because a class that grades less than its name suggests is worse than a class
with a caveat.
Measured before this commit, at 7da4283: write_probe --repo . 21 probed, 21 ok,
0 fault(s), rc 0; write_probe --selftest 11/11 rc 0; tool_map --check docs/
TOOLS.md rc 0; doc_census_check --tools tools/write_probe.py --fail 0 STALE rc
0. Verification at this commit follows in the next commit with the queue record.
Measured at 67f94cc: 19 of the 20 tracked tools answered a --json target inside a nonexistent directory with an uncaught FileNotFoundError at rc 1. Only queue_append_audit.py already refused (rc 2). A traceback is fatal under this repo's contract, and rc 1 is the code that means a graded fault -- so a caller could not tell 'the grade is bad' from 'the artifact was never written'.
Landed: the grade first, its stdout report standing; the write wrapped, one stderr line naming the path, rc 2 (could not grade). gate_blame.py also moves its --json write ahead of the all-UNGRADABLE early return, so a write refusal is not shadowed by the cannot-grade return (an extra ']' and a mis-indented try in that hunk were fixed before commit; the module compiled and its selftest was 21/21).
tools/write_probe.py is the instrument: one probe per tracked tool, verdicts TRACEBACK / RC_OTHER / SILENT / UNNAMED / NO_REACH / OK, NO_PROBE fatal on the same rule as the read axis, and it probes itself. It is leg 6 of verify.py, and selftest_sweep.py now carries both a read probe and a malformed probe for it.
Verification at this commit follows in the next commit with docs/TOOLS.md and the queue record.
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