No release since v1.3.77-pre.6 (Oct 9): every main CI run since Oct 13 fails at pack on package validation (CP0014/CP0015/CP0016) after the Polyfill 11.4.5 bump #207

What's wrong

Every CI run on main since 2026-10-13 (merge of #203, Polyfill 11.4.3 → 11.4.5) fails in ci / .NET / Analyze & Release → Release: dotnet pack stops on package validation (Microsoft.NET.ApiCompat.ValidatePackage.targets(39,5)). Tests pass on all three OSes; only the pack/validate step fails. The last release is v1.3.77-pre.6 (2026-10-09), so nothing merged since has reached NuGet.

Errors in the latest run (2026-10-31): 30 × CP0014, 6 × CP0016, 3 × CP0015, plus "Unnecessary suppressions found".

The diagnostics are on Polyfill's embedded shim types rather than this library's own API, e.g.

error CP0015: Cannot change arguments of attribute 'System.Runtime.CompilerServices.NullableContextAttribute' on 'System.Diagnostics.CodeAnalysis.ExperimentalAttribute'.
error CP0014: Cannot remove attribute 'System.Runtime.CompilerServices.NullableContextAttribute(2)' from 'System.Runtime.CompilerServices.DefaultInterpolatedStringHandler'.

The existing SingleAppInstance/CompatibilitySuppressions.xml (15 lines) is stale as well: ApiCompat reports some of its entries as unnecessary.

The first red run coincides with the Polyfill 11.4.x → 11.4.5 bump landing on main. That's going by timing; I didn't bisect it.

Why it matters

• Unreleased on main right now: 14 commits of dependency bumps, Polyfill 11.4.5 and the system/MSTest groups included (VERSION.md already reads 1.3.77-pre.7).
• Any fix merged from here on also won't ship until pack is green again, and a daily red CI on main hides any new, real failure.

Suggested fix

Regenerate the API-compat suppressions the way ktsu-dev/Schema#295 did for the same failure. Build with the SDK and compiler CI uses (Windows runner, SDK 10.0.403), run dotnet pack -c Release -p:ApiCompatGenerateSuppressionFile=true on the library project, and commit the updated CompatibilitySuppressions.xml. That adds the Polyfill shim entries and removes stale ones.

Acceptance criteria

• dotnet pack -c Release of the library succeeds with package validation on and no suppression generation.
• The next scheduled CI run on main passes Analyze & Release and publishes a release.

Generated by Claude Code