Readable Depth Without the Calibration Map: Formula Placement on Heavy-Hex Devices, and a Defect the Calibration Does Not Show

Compilers for today's quantum processors choose a layout by reading the day's calibration. We ask how deep a circuit stays readable when no placement reads a quality number. We place a ring of CZ gates on IBM's heavy-hex devices in three ways that see only the coupling graph, the basis and which elements have failed: a formula that puts the ring on a lattice cycle (the rule), the ring folded onto the same qubits (zipper), and Qiskit's level-2 search without error rates (blind Qiskit). The workload is the kicked Ising ring at J = pi/4; the probes are a weight-2 charge conserved by the circuit, a mirror echo with a longitudinal field that breaks integrability, and the global parity. In declared tests on ibm_marrakesh and ibm_kingston (29-30 October 2026), the rule kept more of the charge than both other placements in all 24 comparisons (readable depth 56-90 steps against 15-26), and in the non-integrable echo it won 71, tied 11 and lost none of 144 comparisons, at sizes up to n = 72. Several declared predictions failed, and we report them with the results. On ibm_kingston the rule's n = 40 ring carried a run of 18 sites whose echo was near random or inverted: the same 18 sites in three runs of the byte-identical circuit over three hours, while the calibration showed nothing there and the same qubits were healthy on the n = 20 ring. Gate twirling, which leaves the ideal circuit unchanged, turned the inverted part random, so the cause is on the device, not in the circuit; a light-cone argument bounds how far one fault reaches. These sites set the readable depth at n >= 40 and erased the parity at n = 40. A map read from the calibration could not have avoided them. All declarations, records and raw counts are public in TOQB.