Settles the long-standing lore that DatCollection is not thread-safe for reads,
for Chorizite.DatReaderWriter 2.1.7: replays acdream''s real four-population
access pattern (render / streamer / decode-pool / raw) against the live dats —
golden FNV-1a fingerprints taken single-threaded, then 8 threads x 25 shuffled
passes over ~2900 files spanning the cell heightmap/LBI/EnvCell set and the
portal texture chain (Environment -> Surface -> SurfaceTexture -> RenderSurface
incl. highres probes). Two layers: raw TryGetFileBytes (BTree + ReadBlock, no
caching) and typed TryGet with FileCachingStrategy.Never (full production
unpack path: ArrayPool + DatBinReader + ObjectFactory).
Result: ~1.1M concurrent reads, ZERO anomalies — byte-identical to golden.
Matches the line-level audit of the release/2.1.7 source (ReadBlock keeps all
cursor state in locals over a stable read-only mmap view; locked LRU BTree
node cache; ConcurrentDictionary file cache; fresh DatBinReader per call).
The real crash bug was dispose-during-read at teardown (fixed in 8fadf77).
Keep this as the regression guard for any future dat-reader version bump.
Skips cleanly when the dats are absent (CI), matching suite convention.
Full evidence: docs/research/2026-06-09-dat-reader-thread-safety-investigation.md
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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