[initial-d]

Repeated native gathers previously decompressed the same blocks on every call. Add an optional per-handle decoded-block LRU with an explicit payload-byte budget and a 64-entry cap. Opening still disables caching; files, original row IDs and dtype bytes stay unchanged. Raw/oversized blocks bypass caching, failed decodes are not inserted, and budget changes clear entries.

Expose additive C cache configuration/usage/hit counters and native_cache_bytes through NativeRows, Engram factory/gather and ordinary embedding loaders. Zero-budget loading stays compatible with older compiled libraries; opting in requires a rebuilt library. Handles remain immutable and single-worker. Scratch, metadata and query buffers are additional memory beyond the decoded payload budget.

Validation:

• 35 tests pass with PyTorch, including LRU eviction, budget reset, tail blocks, oversize/raw bypass, failed decode, invalid-query recovery, 64-entry cap, old-library loading and special float bit patterns. System Python passes with 17 optional tests skipped.
• ASan/UBSan exercise enabled caches, repeated calls, changing budgets, versions 1/2 and 128 deterministic mutated/truncated files.
• Official Engram and proposed factory each preserve full output bytes in nine tiny random CPU cases, including cached repeated forwards. These are interface fixtures, not trained Engram evidence.
• All 81 trained-table/trace/budget cases preserve original rows/query bytes and respect payload limits. A 2 MiB cache improves warm corpus-replay p50 ~6.9× at order 4 and ~1.7× at orders 8/12; 256 KiB gets no hits on that replay and adds overhead. The deliberately favorable eight-block hotspot control is reported separately, without a model-speedup claim.

Raw samples, hashes, commands, initial pilot and negative capacity results are retained in docs/native_cache_evidence_20261022/, summarized in docs/native_cache_20261022.md. Small English SGNS tables and short repeated traces; no real Engram workload, cold I/O, total process RSS, GPU or task-quality claim.