[michaldengusiak]

Adding SAM.Core.Diagnostic in SAM#201 changes unqualified Diagnostic resolution inside SAM.Core.Multitasker, so unchanged script compilation fails with CS0029. Use a distinct RoslynDiagnostic alias in both compilation and result types, preserving the historical public Roslyn APIs and all algorithms.

Proven cause

• Latest preserved successful full BuildAll: morning 2026-10-15; SAM 0649e15ee9c1727af5834d9206017da9860917c5 + Multitasker aa126fa. Full 26-repository configuration is committed. SHAs were reconstructed from reflogs with contemporaneous clean-tree evidence; the original build log did not record them.
• Exact boundary with unchanged Multitasker: SAM a71435dd88d28c9b0da0bca43c21fbca5e1038b9 passes; its immediate child 967a8639eb6f7f614ff4168d62ab3dfd979efbe4 fails. Isolated builds vary only SAM.Core.
• SAM Q4 6b12e2a65817556693ba408674211610f4a20dda before SAM#204 also fails. SAM#204 is independent and unchanged.

Validation

Tested content: cfe9d11. Final PR head: e245510; subsequent commits contain records only, final diff check passes.

• Affected project builds, 0 errors. Four NUnit tests pass, 0 failed/skipped: historical public Roslyn types, same-object diagnostic transfer, invalid-script diagnostics, and existing icon test.
• Fix builds against exact first-breaking SAM dependency; API/behavior probes pass against both good and fixed configurations.
• Full BuildAlls_v5.bat nopause: PASS, exit 0, 00:07:41.6286121, all 26 active repositories, Revit 2025/2026/2027 and final OCCT ABI/dependency/hash checks. Original CS0029 absent; no new build failures. Existing warnings remain.
• Similar-collision audit across active repositories found no equivalent remaining collision.
• Initial GitHub Build and SPDX passed at 7f95bfb. Build logs confirm SAM dependency selection sow/2026-Q4 and actual Multitasker compilation. Final-head Build 38792606241 and SPDX 38792606472 PASS at e245510. Final build log also confirms Q4 dependency selection, actual Multitasker compilation and no compiler/MSBuild errors.

Evidence: documentation/Diagnostic-Collision-Validation-2026-10-15.md and documentation/evidence/diagnostic-collision-2026-10-15/*.json record exact configurations, boundary, timing and retained local log hashes. Raw local logs and the archive harness are machine-local as labeled in the record.

Base sow/2026-Q4. No algorithm/component/workflow/shared SAM.Core changes. PROJECT_PROGRESS is unchanged under the post-merge-only policy. Owner authorized merging once green on 2026-10-15. Final-head checks and compilation logs verified before merge.