A 2.5× LR increase did not move a Reference turn-detector warm start

Observed 2026-09-07 on e3-solutions/ender-inference COR-3791, branch vansh/cor-3791-fine-tune-a-freight-turn-detector-for-identifiers-pauses-and, commit 732f414: an all-linear rank-8 Reference LoRA warm-started from the selected lm_head adapter was trained for one epoch on an exact balanced 90-row corrective-plus-rehearsal corpus. Raising only the learning rate from 2e-5 to 5e-5 preserved step-zero BF16 parity and produced zero rehearsal regressions, but every 25/50/75/100% checkpoint and the final adapter reproduced the selected service result exactly (34/42, 3 false-finished, 5 missed-finished) across three deterministic passes. This rules out a modest LR increase as the missing lever for this bounded objective; further work should change evidence coverage or the optimization objective, not repeat nearby LR sweeps.