[masarray]

Physical symptom

BCUGE Browser SGCB Last changed displays 1970-01-01... (q=0x3F). A zero UTC-Time with actual eight-byte raw provenance is an unset relay timestamp, not evidence of a settings-group change at epoch.

Narrow consumer-only remediation

• Preserve pinned engine raw UTC-Time evidence on exact LActTm leaf in addition to standard .t leaves.
• Keep proof in the existing association-fenced canonical live-values ledger (no parallel cache or second decoder).
• Display Not initialized only for exact typed wire SecondsSinceEpoch=0 and FractionOfSecond24=0. Arbitrary 1970 text, nonzero time, and other pages are untouched.
• Preserve the wire hex and IEC time-quality in the SGCB field tooltip. No new reads, GI, writes or settings operations.

Regression and safety

Typed raw-evidence fixture proves canonical storage, zero time vs true/non-proven timestamp presentation. Field acceptance on BCUGE required. No engine pin/main/release changes. CI must pass on the exact PR HEAD before integration.

[masarray]

Reconciliation D4 — historic SGCB LActTm raw UTC wire semantics retained

Disposition: A — superseded by pinned protected RC, safely close unmerged. Old head 5ef905ecefbe1a3bccbec28dfc89f71f9f374a15 is exact ancestor of RC 817c3910e8223fa2ac531a4426ada5d2d4bbbe50; compare ahead 1345 / behind 0, merge-base old head. This is NOT ancestry-only: five paths reviewed for original semantics.

Canonical: protected RC #727 / #729 at 817c3910e8223fa2ac531a4426ada5d2d4bbbe50.

Unique delta proved, path-by-path:

• Models/IedBrowserControlStateEvidence.cs historic blob c50073eeae8a90123accc96bc9a4d9e8295ba614 → RC cbaae22d81b27fbff4e14ce20a864b8f3c19a850: exact FormatObservedField guard preserved, only SGCB LActTm with actually decoded, wire-proven UTC epoch seconds 0 and fraction 0 displays Not initialized; unverified text and real timestamps remain untouched.
• Models/IedBrowserLiveValues.cs historic 6bc971fe37df6cc24f4870b491d33bf91bc3f2d1 → RC 2980e831dbc0cbf8d5b9b0a4c836f94f32133653: canonical IsTimeReference covers both .t and .LActTm; no timestamp fabricated.
• Services/NativeIec61850Client.cs historic 727c9324fc5aedbac9155e2b3a45489234343adb → RC b74398faf4d206286ab1dcac8b6e5ab414783393: raw .LActTm / $LActTm recognized only for actual MmsDataKind.UtcTime, decoded with Iec61850UtcTimeEvidence.Decode(raw); time evidence attached only when actually decoded and wire-proven.
• MainWindow.IedBrowser.cs historic 511bfcb5480cca086b2deb32371314246ff0a246 → RC 21a0551413a5437a562c463f011204868aab7b3e: live SGCB state uses FormatObservedField(pageKind,field,observed), then local-time presentation, retaining stale/actual MMS Read provenance. UI never treats a textual “1970” string as wire proof.
• tests/ARSAS.Tests/M214SgLastChangedWireEvidenceTests.cs exact identical old+RC blob 7d0fafd60c54e0be6c11c6cefd33d5c4c420d7b7, both zero-time and unverified/real-time regressions retained.

Safety: Pure historical closure; no MMS write/SG edit group/change command, no source edits, no engine repin, no main/stable release promotion. Automated pinned RC Windows regression previously passed on exact #753 head, not physical SGCB FAT.

Follow-up: Actual relay SGCB active-group read/association and field acceptance remain separate; no fake “1970 last change” for raw-zero wire evidence, no fabricated time if q/t absent; original branch and source retained.