Recovery: Build #1868 FAT baseline first; scroll patch quarantined - #257

GOLDEN MASTER — DO NOT DRIFT

Exact bench-good source SHA:

aee3c34df3ca3126f4294575b4282a39387ba427

Reference runtime: original ARSAS 1.6.33 FAT IED Test EXE from CI artifact / Build ARSAS #1868.

Golden EXE fingerprint supplied from the physical bench-good artifact:

SHA-256 063751919b51ef1bf13f666441ec2fff7e1f5a54a5b647295c158abbd732a0d6

This is NOT interchangeable with the v1.6.33 release asset binary.

Physical-bench failure found on recovery attempt

The runtime patch that changed VirtualizingPanel.VirtualizationMode from a WPF Loaded class handler is invalid. Physical bench evidence produced:

System.InvalidOperationException: Cannot change the VirtualizationMode attached property on an ItemsControl after Measure is called on the ItemsHost panel.

That exception interrupted FAT rendering and produced an empty/partially initialized FAT table even though IEC 61850 reporting itself was alive.

Current recovery policy

Reliability first. The scroll fix is quarantined.

Current branch restores the golden XAML-owned virtualization behavior and removes all runtime mutation of VirtualizationMode from IoListTestingWindow.

Do not reintroduce a runtime virtualization patch from Loaded, OnInitialized, Dispatcher callbacks, or any other post-construction lifecycle seam.

A future scroll-only change is allowed only after the exact golden FAT workflow passes physical bench again, and it must be applied through a WPF lifecycle-safe mechanism with no change to FAT membership, session, acquisition, RCB/DataSet, evidence, or Engineering/FAT navigation.

Must remain identical to Build #1868

• Engineering → FAT workspace/data continuity after SCL import.
• Ability to return to Engineering exactly as in the bench-good build.
• FAT table population and row schema.
• TEST / SIGNAL / IEC REFERENCE / TYPE / LIVE VALUE / VALUE 1 / VALUE 2 / STATUS / RESULT.
• FAT capture/session/evidence behavior.
• RCB/DataSet behavior and acquisition semantics.
• SCL import lifecycle and workbook/device state.

Explicitly forbidden in this recovery

• Runtime VirtualizingPanel.SetVirtualizationMode mutation in IoListTestingWindow.
• Per-cell PropertyChanged/CollectionChanged subscriptions.
• Dispatcher polling loops.
• MMS read-path rewrite.
• RCB/DataSet mutation.
• Evidence/session mutation.
• Engineering/FAT navigation redesign.
• FAT table/schema redesign.
• Unrelated cleanup/refactor.

Physical bench gate before merge

1. Engineering opens normally.
2. Import SCL/CID.
3. Confirm Engineering Live Monitor receives the expected points.
4. Enter IO LIST FAT and confirm all expected rows render immediately.
5. Confirm V2 schema: TEST / SIGNAL / IEC REFERENCE / TYPE / LIVE VALUE / VALUE 1 / VALUE 2 / STATUS / RESULT.
6. Start/Continue FAT and verify rows do not disappear.
7. Capture VALUE 1 and VALUE 2 and verify status/result/evidence.
8. Return to Engineering, then return to FAT without unloading state.
9. Stress-scroll only after all gates above pass.
10. No UI exceptions in diagnostics.

Do not merge until this exact sequence passes on the physical relay bench.