[release/8.0-staging] Fix broken debugger/debuggee startup handshake protocol on macOS26. #118213
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jeffschwMSFT
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Aug 4, 2025
tommcdon
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leecow
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Backport of #118120 to release/8.0-staging
/cc @steveisok @lateralusX
Customer Impact
On the MacOS 26, we found the debugger startup handshake using named sempahores are now broken when the debugger and the debuggee are signed with different team id's. This casues the entire VS Code C# debugging experience to be non-functional.
Interestingly, the MacOS release notes only show this being depreicated on iOS. Perhaps this will end up being true on future betas, but I don't think we should hold out any hope.
The fix in this PR uses named pipes first in the handshake and will fall back to the previous implementation if necessary. Mostly on backwards compatibility grounds.
Regression
[If yes, specify when the regression was introduced. Provide the PR or commit if known.]
Testing
Manual before broken / after fixed testing on VSCode.
Risk
Low
IMPORTANT: If this backport is for a servicing release, please verify that:
release/X.0-staging, notrelease/X.0.Package authoring no longer needed in .NET 9
IMPORTANT: Starting with .NET 9, you no longer need to edit a NuGet package's csproj to enable building and bump the version.
Keep in mind that we still need package authoring in .NET 8 and older versions.