Concurrency was two multiplicative gates in two processes: entrypoint.sh capped MODELS-at-once per provider (GADFLY_PROVIDER_CONCURRENCY) while each model's binary separately capped its own lenses (GADFLY_LENS_CONCURRENCY). A model therefore held its whole model-slot until its LAST lens finished, stalling the next model even with idle lens capacity. Collapse to one throttle: a provider-wide lens budget shared across all of that provider's models. entrypoint now runs every model in a lane at once and seeds a single cross-process permit pool per lane (a dir of N flock files, sized by GADFLY_PROVIDER_LENS_CONCURRENCY -> GADFLY_LENS_CONCURRENCY). Each lens pass (review+recheck) acquires a permit before it runs and releases it after, so a model winding down immediately yields its freed permits to another model's queued lenses. flock auto-releases on process death, so a killed/crashed model can't leak budget. - cmd/gadfly/lenssem.go: the flock permit pool (+ lenssem_test.go). - main.go: runSpecialists holds a shared permit per lens; fanout sized to the budget so a lone model can use all of it. Falls back to the in-process limit when no pool is set (local runs, tests). - entrypoint.sh: drop provider_cap/DEFAULT_CONC; run_lane runs all models and seeds the per-lane pool. - GADFLY_PROVIDER_CONCURRENCY / GADFLY_CONCURRENCY are now ignored; the reusable workflow marks provider_concurrency deprecated and stops forwarding it. Docs (README, CLAUDE.md, examples) updated per the maintenance rule. Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>