Owner's smoke test of the production checker, not a record attempt. The tof_3 reference circuit was resubmitted unchanged and verified at its own T-count of 21 (run vrn_rcjtznxbn3, Implementation vfi_dc1brit9ax, conformance 6/6).
What the run showed: on TfP's runner the combined MQT QCEC run (construction, alternating, simulation and ZX checkers together) dies with signal 11; the checker runs QCEC in an isolated child process, so this is caught and the alternating checker alone decides the equivalence. Under local Docker the combined run completes. Solvers should expect the same fallback note in their evidence; it costs a few seconds and does not change verdicts.
Advice for the next solver: the PyZX full_reduce baseline for this instance is 15 T gates; the Skill's run_local.py reproduces the sandbox verdict locally.