Two tests proved "these two unrelated DAT reads ran concurrently" by
racing a fixed Thread.Sleep(40) window against .NET thread-pool
scheduling latency for a second Task.Run. Under the CPU contention of
a full `dotnet test AcDream.slnx` run (all 9 test projects' VSTest
hosts launch concurrently) plus a busy machine, thread-pool injection
can occasionally miss the window, making MaxConcurrentReads read 1
instead of 2 and failing the assertion with no underlying code defect.
RetailAnimationLoader and RetailPhysicsScriptLoader both coalesce
same-key reads correctly via ConcurrentDictionary<K, Lazy<T>>.GetOrAdd,
which is atomic and timing-independent (verified by reading, not just
running) - only the test's method of proving cross-key overlap was
timing-fragile. DecodedTextureCacheTests already uses the correct
deterministic-gate pattern; this brings RetailDatLoaderTests in line
with it via a Barrier-backed rendezvous instead of a sleep race.
Filed as #248 (docs/ISSUES.md) with the full attempt matrix: could not
catch the originally-reported AcDream.Content.Tests failure in the act
despite ~72 Content.Tests executions across four contention strategies
over ~30 full-suite-equivalent runs, though the general mechanism
reproduced 3x in AcDream.App.Tests's already-known zero-allocation
flake class (left untouched, out of scope here).
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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