.NET: Make GitHub.Copilot.SDK build targets reach transitive consumers (#6455)

[tamirdresher]

Motivation and Context

Fixes #6455.

Consumers who reference Microsoft.Agents.AI.GitHub.Copilot (the normal way to use the adapter) currently get only the managed .dll — no copilot.exe in their output, and the SDK throws InvalidOperationException: Copilot CLI not found at runtimes\{rid}\native\copilot.exe on the first RunAsync. Root cause is purely packaging: GitHub.Copilot.SDK ships its CLI binary-download MSBuild targets under build/, which NuGet only auto-imports for projects with a direct PackageReference to the SDK. Transitive consumers never see those targets and the binary never lands.

The SDK targets themselves are correct — adding <PackageReference Include="GitHub.Copilot.SDK" /> directly to a consumer alongside the MAF reference makes the SDK targets fire and ~115 MB copilot.exe shows up at the right path. So the fix here is to make those targets reachable to consumers of the adapter package as well.

Long-term, relocating the targets from build/ to buildTransitive/ in github/copilot-sdk itself is the cleaner SDK-side fix and would benefit every downstream package, not just this one. Issue #6455 covers both options; this PR implements the adapter-side fix (Option A) so MAF users get unblocked immediately without an SDK-side coordination cycle.

Description

Adds a tiny buildTransitive/ bridge to Microsoft.Agents.AI.GitHub.Copilot so the SDK's binary-download targets reach transitive consumers.

Files added:

• dotnet/src/Microsoft.Agents.AI.GitHub.Copilot/buildTransitive/Microsoft.Agents.AI.GitHub.Copilot.targets — static bridge. Imports the SDK's build/GitHub.Copilot.SDK.targets from the NuGet cache ($(NuGetPackageRoot)/github.copilot.sdk/$(_MicrosoftAgentsAICopilotSdkVersion)/build/...). The version-pin condition no-ops gracefully when the resolved SDK version differs from what we baked, so this is purely additive — consumers already pinning the SDK directly see no behavior change.
• dotnet/src/Microsoft.Agents.AI.GitHub.Copilot/buildTransitive/.gitignore — ignores the auto-generated props file (regenerated on every pack, similar to how GitHub.Copilot.SDK itself generates build/GitHub.Copilot.SDK.props at pack time).

Files modified:

• dotnet/src/Microsoft.Agents.AI.GitHub.Copilot/Microsoft.Agents.AI.GitHub.Copilot.csproj — adds a _GenerateBuildTransitiveProps target that runs BeforeTargets="_GetPackageFiles". It resolves the SDK version from @(PackageVersion) items (Central Package Management surface) and writes buildTransitive/Microsoft.Agents.AI.GitHub.Copilot.props setting $(_MicrosoftAgentsAICopilotSdkVersion). Both files are then packed under buildTransitive/. Same pattern the SDK uses for its own props (_GenerateVersionProps in GitHub.Copilot.SDK.csproj).

Compatibility:

• No API surface change — public surface of the assembly is untouched.
• No behavior change for projects with a direct <PackageReference Include="GitHub.Copilot.SDK" />. The SDK's build/ targets still fire for them as today; our bridge's condition Exists($(_MicrosoftAgentsAICopilotSdkBuildDir)/GitHub.Copilot.SDK.targets) succeeds and re-imports the same file — <Import> is idempotent in MSBuild and only schedules each target once.
• Consumers can opt out of the binary download via the SDK's existing $(CopilotSkipCliDownload)=true, which our bridge passes through unchanged.

Verification:

Built the package locally on this branch (Microsoft.Agents.AI.GitHub.Copilot 1.9.0-preview.260603.1), confirmed both buildTransitive/*.props and buildTransitive/*.targets ship in the resulting nupkg, then created a brand-new console app with only:

<PackageReference Include="Microsoft.Agents.AI.GitHub.Copilot" Version="1.9.0-preview.260603.1" />

(no direct SDK reference) restored from a local feed pointed at the freshly-built nupkgs. On dotnet build, the bridge fired, the SDK's _DownloadCopilotCli target downloaded @github/copilot-win32-x64/1.0.57.tgz from npm, extracted, and copilot.exe (141.8 MB) landed at bin\Debug\net10.0\runtimes\win-x64\native\copilot.exe. copilot --version reports 1.0.61 as expected (the npm subpackage version differs from the bundled binary's self-reported version, both correct).

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the Contribution Guidelines
• All unit tests pass, and I have added new tests where possible (MSBuild packaging change — no managed surface to unit-test; verification covered end-to-end via the consumer test above)
• Is this a breaking change? No. Pure addition, no API surface change, no behavior change for existing consumers.

[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

Adds a buildTransitive bridge so transitive consumers of Microsoft.Agents.AI.GitHub.Copilot also import GitHub.Copilot.SDK’s build/ targets, ensuring the Copilot CLI binary download/copy steps run without requiring a direct PackageReference to the SDK.

Changes:

• Added a transitive .targets file that locates the SDK in the NuGet cache and imports GitHub.Copilot.SDK.targets.
• Added pack-time generation of a buildTransitive .props file to bake in the resolved GitHub.Copilot.SDK version.
• Added a .gitignore entry for the generated .props file.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
dotnet/src/Microsoft.Agents.AI.GitHub.Copilot/buildTransitive/Microsoft.Agents.AI.GitHub.Copilot.targets	Imports SDK build targets for transitive consumers based on a generated SDK version property.
dotnet/src/Microsoft.Agents.AI.GitHub.Copilot/buildTransitive/.gitignore	Ignores the generated buildTransitive props file.
dotnet/src/Microsoft.Agents.AI.GitHub.Copilot/Microsoft.Agents.AI.GitHub.Copilot.csproj	Generates and packs the transitive .props, and packs the static transitive .targets.