[T-Gro]

Description

Add opt-in regression investigations that reproduce reported failures against released and historical F# toolchains, then bisect and confirm the source boundary. Resumable, authenticated checkpoints and retained evidence let maintainers recover interrupted investigations without publishing unverified results.

Checklist

• Test cases added (not rerun for this PR-creation and release-note-only update)

• Performance benchmarks added in case of performance changes

• Release notes entry updated:

  Please make sure to add an entry with short succinct description of the change as well as link to this pull request to the respective release notes file, if applicable.

  Release notes files:

  • If anything under src/Compiler has been changed, please make sure to make an entry in docs/release-notes/.FSharp.Compiler.Service/<version>.md, where <version> is usually "highest" one, e.g. 42.8.200
  • If language feature was added (i.e. LanguageFeatures.fsi was changed), please add it to docs/release-notes/.Language/preview.md
  • If a change to FSharp.Core was made, please make sure to edit docs/release-notes/.FSharp.Core/<version>.md where version is "highest" one, e.g. 8.0.200.

  Information about the release notes entries format can be found in the documentation.
  Example:

  • More inlines for Result module. (PR #16106)
  • Correctly handle assembly imports with public key token of 0 length. (Issue #16359, PR #16363)
    *while! (Language suggestion #1038, PR #14238)

  If you believe that release notes are not necessary for this PR, please add NO_RELEASE_NOTES label to the pull request.

[T-Gro]

🤖 🕵️ AI review — verify independently.

[T-Gro]

🤖 🕵️ [P2] Valid transitive graphs rejected as wrong-identity — with all four project/TFM cells declared, this expects Leaf/net10.0-windows7.0 instead of MSBuild's Leaf/net10.0. Resolve each edge against current.tfm, not the root cell's TFM.

<!-- App.fsproj -->
<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup><TargetFramework>net10.0-windows7.0</TargetFramework><DisableTransitiveProjectReferences>true</DisableTransitiveProjectReferences></PropertyGroup>
  <ItemGroup><ProjectReference Include="Library.fsproj" /></ItemGroup>
</Project>
<!-- Library.fsproj -->
<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup><TargetFramework>net10.0</TargetFramework><DisableTransitiveProjectReferences>true</DisableTransitiveProjectReferences></PropertyGroup>
  <ItemGroup><ProjectReference Include="Leaf.fsproj" /></ItemGroup>
</Project>
<!-- Leaf.fsproj -->
<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup><TargetFrameworks>net10.0;net10.0-windows7.0</TargetFrameworks></PropertyGroup>
</Project>

[T-Gro]

🤖 🕵️ [P2] Source-derived sample SDK rejected despite graph-verified host compatibility — in the supported workspace FSI lane, verifyToolchainIdentity accepts win10-x64 for requested win-x64, but this prefix check returns wrong host OS (untestable/wrong-identity) before FSI starts. Use the verified requested platform rather than reclassifying the measured host RID.

// Source-derived sample SDK identity:
// requested.platform = { os: "windows", architecture: "x64", rid: "win-x64" }
// rid = "win10-x64"
// Acquired RuntimeIdentifierGraph.json:
// { "runtimes": { "win10-x64": { "#import": ["win-x64"] } } }
verifyToolchainIdentity({ policy, toolchain: identity.requested, identity });
// { status: "verified" }
await runReproduction({ ...repro, toolchain: identity });
// untestable/wrong-identity: "wrong host OS"