test_proof_corner_reveal drove moves back-to-back. The Gauntlet player is
Walk stance (ticks_per_move=2, server stance.rs), so a move arriving within
the cooldown window is silently throttled (movement.rs::apply_move ->
PlayerMoveCooldown::try_move). _send_and_receive returned the instant a move
landed, so the next send raced the cooldown and an occasional move was
dropped — leaving the player one tile short, which (via the test's cumulative
expectations) cascaded into the corner-reveal perception assert. A different
move dropped each run = flaky; exposed by the heavier post-cascade tick timing.
Test-side fix only — game behaviour is correct and the Gauntlet world is
immutable: after a move lands, wait for the server clock to advance
COOLDOWN_TICKS past the landing tick before the next send. Full client suite
2538/2538 green; the proof suite drops from ~28s (timeouts) to ~4s.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>