# Stage 4 determinism oracle: the run and its negative control, 2026-08-15

The Stage 4 gate is the reference executor's serial-vs-parallel harness, run as a determinism
oracle. Both runs below were executed on this machine (WSL, Rust release build of
`aere-research/parallel-executor`), not asserted from documentation.

## Positive run: parallel Block-STM == sequential

    cargo build --release
    ./target/release/aere-block-stm harness

    mismatches            : 0
    RESULT: PASS -- parallel Block-STM == sequential on ALL cases

Across the harness profiles (mixed-moderate and others), seeds, and thread counts (4, 8, 16),
the state root produced by optimistic parallel Block-STM is byte-identical to the state root the
sequential oracle produces for the same block and pre-state. Zero mismatches.

## Negative control: disable validation, and the oracle goes red

Block-STM's validation phase is what catches a transaction that read a now-stale value and forces
it to re-execute. It is exactly the mechanism that prevents a silent divergence. The control
disables it (the validation match arm forced to report "matches" always) and rebuilds:

    src/parallel.rs:198  _ => false  ->  _ => true  /* PLANT: validation disabled */

    ./target/release/aere-block-stm harness

    MISMATCH profile=mixed-moderate seed=0 threads=4:  parallel != sequential
    MISMATCH profile=mixed-moderate seed=0 threads=8:  parallel != sequential
    MISMATCH profile=mixed-moderate seed=0 threads=16: parallel != sequential
    MISMATCH profile=mixed-moderate seed=1 threads=4:  parallel != sequential
    ...

With validation removed, parallel execution commits a divergent state on contended traffic and
the harness catches it on every profile. The source was restored immediately after.

## What this proves, and what it does not

PROVES: the determinism oracle is load-bearing. A green from it means parallel and serial agree,
because the same oracle demonstrably goes red the moment the safety mechanism that guarantees
agreement is removed. This is the D-150 discipline applied to parallel execution: the failure
mode of concern (silent state divergence under contention) is exactly the one the negative control
plants and the oracle catches.

DOES NOT PROVE: a throughput number (none is claimed; blocks on 2800 are empty, so 8-10x is proven
capacity, not realized debit), and does not put parallel execution on mainnet. It proves the
equality that makes turning it on a measured decision rather than a hope. Turning it on, if it
ever changes an observable, is one coordinated activation, the discipline proven at block
14,050,000.