[Agents Extension] Better handling for protocol flag

[trangevi]

Handles silent failure due to missing protocol. Also addresses bug where multiple protocols would always use the first one if no flag was provided

[Copilot]

Pull request overview

Note

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

Improves agent invocation protocol resolution by surfacing actionable errors when a protocol can’t be determined and fixing incorrect selection behavior when multiple protocols are declared.

Changes:

• Makes resolveProtocol/resolveAgentProtocol return errors instead of silently defaulting.
• Consolidates protocol auto-detection logic to use a single azd client path for local/remote resolution.
• Updates unit test(s) to handle the new (protocol, error) return shape.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 4 comments.

File	Description
cli/azd/extensions/azure.ai.agents/internal/cmd/invoke.go	Propagates protocol resolution errors and consolidates local/remote protocol detection into one flow.
cli/azd/extensions/azure.ai.agents/internal/cmd/helpers.go	Changes protocol resolution to return contextual validation errors when agent.yaml can’t be read/parsed or is ambiguous.
cli/azd/extensions/azure.ai.agents/internal/cmd/invoke_test.go	Updates existing test to handle the new error-returning API.

[jongio]

The approach is solid - converting silent defaults to explicit exterrors.Validation errors is the right fix. Users with misconfigured agent.yaml now get clear guidance instead of mysterious wrong-protocol behavior.

The resolveLocalProtocol/resolveRemoteProtocol consolidation is clean. They only differed on the name parameter, so the single if/else on a.flags.local is simpler and correct.

Two things before this merges:

1. The case 1 path should validate that hosted.Protocols[0].Protocol isn't empty - a protocols: [{ version: v1 }] entry (missing protocol field) returns "" with nil error, which silently falls through to responses downstream. The bot's suggestion here is valid.

2. The five new error scenarios in resolveAgentProtocol are the core value of this PR and need test coverage. This is non-trivial since it requires mocking the azdClient, but the existing TestResolveProtocol_ExplicitFlag pattern could be extended with a test fixture that writes temp agent.yaml files.

Side note: the author's rejection of the error-wrapping suggestion on invoke.go:167 is correct. The exterrors package docs say not to wrap structured errors with fmt.Errorf, and the fmt.Errorf("failed to create azd client: %%w", err) pattern on line 205 matches 7+ other call sites in this extension.

[github-actions]

📋 Prioritization Note

Thanks for the contribution! The linked issue isn't in the current milestone yet.
Review may take a bit longer — reach out to @rajeshkamal5050 or @kristenwomack if you'd like to discuss prioritization.