Block-STM enters the kernel through the MachineInterface seam, not beside it. The
one guarantee, stated as a contract and proven: parallel execution produces the
byte-identical state root that serial execution produces, or the kernel refuses
it. The feared failure mode is a silent state divergence under contention, and
that is exactly what the negative control plants.
Run 2026-08-15 (WSL, Rust release build of parallel-executor):
- positive: harness reports 0 mismatches, parallel Block-STM == sequential on
all profiles, seeds, and thread counts 4/8/16.
- negative control: disable the validation phase (the mechanism that catches a
stale read and forces re-execution) and the harness reports MISMATCH on every
contended profile. So the oracle is load-bearing, not applause.
No throughput number is claimed; 8-10x is proven capacity while chain 2800
blocks are empty. Parallel execution is not put on mainnet in this stage; the
equality that would make that safe is proven, so the switch becomes a measured
decision. One coordinated activation if it ever changes an observable, the
discipline proven at block 14,050,000.
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