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The loadtest harness never modelled game.evaluate — the debounced per-tile play preview a real client fires several times per turn, the hottest gameplay call. Model it (one evaluate per placed tile + reconsideration re-previews + draft.save, human-paced; --eval / --eval-recon toggle it). That realistic load surfaced the real bottleneck: the gateway's backend HTTP client used the default transport (MaxIdleConnsPerHost=2), so every sync call to the single backend host churned a fresh TCP connection — ~26500 TIME_WAIT sockets at 500 players (near the ephemeral-port ceiling), burning ~1.75 gateway cores while the backend sat near-idle. It was the unfixed root of the residual transport_error the earlier passes chased on the client side. Widen the keep-alive pool (backendMaxIdleConns=512, ~2x the observed 225-conn peak). At 500 players the churn collapses to ~0 and peak gateway CPU drops ~7x (~1.75 -> ~0.26 cores); postgres (~1.65 cores) becomes the busiest service. This overturns the earlier "gateway is the binding constraint, scale it horizontally" sizing — that was sizing around this bug, not a real floor. Consolidate the loadtest trip reports into one loadtest/REPORT.md (drop the R2/R7 split) and bake the finding into README / PRERELEASE / ARCHITECTURE / TESTING.