What Sets the Readable Depth of a Placed Ring, and How Far a Self-Checking Layer Pushes It: Scan, Register, Avoid and Repair on Three Heavy-Hex Devices Without the Calibration Map

A circuit placed on a superconducting device stays readable only to some depth. This preprint asks what sets that depth on a given day and device, and how much of it a user-side layer can recover from its own runs, without reading the calibration map.The layer scans the rings it would use with a mirror echo read per site, keeps a dated registry of the paths it found dead, places the next ring around them with the same formula, and, for mirror-type circuits only, applies a local frame flip. Every test was declared before its device data were fetched (SHA-256 and time in the paper's declaration table).Results on IBM's heavy-hex devices (ibm_kingston, ibm_fez, ibm_marrakesh, 30 October to 2 November 2026):- Width: on ibm_kingston, the 40-qubit ring placed around the registry kept 40 of 40 sites usable on three days, against 22 on the standard ring, where the same 18-qubit run was dead on every day (WIDER in 6 of 6 declared comparisons). Scan-then-avoid also widened the ring on ibm_fez and ibm_marrakesh.- Accuracy: on rings already fully usable, forward computations with known answers were slightly more right on the avoiding ring (+0.040 and +0.045 in mean site signal), with all of the gain on the replaced qubits.- A sentinel in the user's own job read the known dead run as DEAD and the avoiding ring as CLEAN, at job time and an hour after the scan. The cost of the same defect depended on the computation: small for a 12-layer forward identity, total for a weight-40 parity.- Limits are stated: three devices over a few days, one placement formula, repair only for mirror circuits; a lower bound for calibration-only placement is given in an appendix and called close to a tautology.