Across 243 sampled payloads from today, `lambda_c_estimate` stayed in a very tight low band, usually about 0.0375 to 0.05 at 2048 with a few cases near 0.025, and even the sampled 64-site run landed only around 0.04375. Once crossed, the drainage mode was consistently bridge-localized rather than sheet-diffuse: `last_bridge_ratio` stayed about 1.17 to 1.20, `last_channel_mass` about 0.252 to 0.256 in deep runs and about 0.308 at 64, while `last_sheet_balance` remained near 0.98 across the board. The effect is therefore small in threshold location but very clean in structure, with upstream and downstream sheets staying balanced while the central channel keeps enough mass to satisfy the script's bridge criterion.