[dotnet] SendAndWaitAsync throws timeout for cancelled tokens

[juscelinotanaka]

Ref:

copilot-sdk/dotnet/src/Session.cs

Lines 204 to 205 in c263dfc

	tcs.TrySetException(new TimeoutException($"SendAndWaitAsync timed out after {effectiveTimeout}")));
	return await tcs.Task;

If the cancellation token passed to SendAndWaitAsync is cancelled externally it always throws a TimeoutException - instead of a OperationCanceledException.

This make it hard to tell to the user what's the real issue - if it's just a user cancellation or if the action indeed timed out.

[github-actions]

Thank you for opening this issue, @juscelinotanaka!

You're absolutely right — this is a bug in the .NET SDK. The SendAndWaitAsync method should throw OperationCanceledException when the cancellation token is cancelled externally, not TimeoutException. This will help callers distinguish between user-initiated cancellations and actual timeouts.

Applied labels: sdk/dotnet, bug

We'll investigate and address this issue.

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