[masarray]

Baseline & scope

Engine PR #183 exact c85d4e20db722bd0c2729f2533b323b13d3ef735. This does not change default 400ms ApplicationErrorGracePeriod, command order, MMS writes, timeouts, subscriptions or release policy. The consumer remains pinned to #183 until an independently qualified engine commit exists.

Evidence-first root cause

Physical SIEBCU/CSWI4 traces: accepted SBOw MMS in 5.198–7.417ms, postResponseWaitMs 399.282–404.249ms, accepted Operate MMS 2.098–2.907ms. Source confirms SelectWithValueCoreAsync awaits WaitForApplicationErrorAsync(_options.ApplicationErrorGracePeriod) with a 400ms default. Shortening it alone would risk emitting Operate after an asynchronous SBOw rejection.

Engineering changes

1. Exact control wire-step diagnostics now label postResponseStage=sbo-application-error-observation and configuredApplicationErrorGraceMs alongside pre-existing service and monotonic elapsed evidence; Operate remains separately labelled operate-termination-observation. Diagnostic classification, not a new clock or control state machine.
2. Deterministic synthetic tests: successful SBOw response followed by immediate and delayed (35ms) negative LastApplError MUST NOT emit Operate. Preserve request-accepted vs application-rejected vs command-termination semantics and exact negative AddCause. Existing positive termination test asserts new stage fields.

Next gate

Exact-head engine CI and negative scenario suite. A future transaction-correlated observer may shorten the successful path only after proving late-negative, old transaction, ctlNum/origin, disconnect, timeout and duplicate controls. No unqualified immediate-Operate fast path is enabled here; no physical speed claim or main merge.

[masarray]

Cleanup of verified stacked Git ancestry on 2026-10-22: original source SHA 9c7cb40364023a7b217e5ec31ab3105ba90142eb is fully contained (0 missing commits) in canonical consolidated draft #190, currently 14b19d30466fd296ad1e6d0bddcdd574992bc464; exact merged-tree Windows CI #39778971482 passed 1,262/1,262 tests with no build warning/error.

Closing this now as consolidated/superseded, NOT merged to main; no branch deletion, no source history loss, no ARSAS repin, no mainline engine source promotion. Original physical validation and follow-ups still apply, and #190 remains draft. If #190 is discarded, this PR is available to reopen.