feat: Enforce events ordering

[bartek-gralewicz]

Description

This PR introduces a stream ordering enforcement as stated in protocol spec 3.1.2 ("Behavior" section).

The stream should distinguish 2 cases:

• The Message is the first streamed object.
  • In such case, the stream should not accept any more objects and close right after the initial message. The UnsupportedOperationError is thrown if such case occurs.
• The Task is the first streamed object.
  • After the initial task, only TaskStatusUpdateEvent or TaskArtifactUpdateEvent can occur. In other cases, a UnsupportedOperationError is thrown.

[github-actions]

🧪 Code Coverage

⬇️ Download Full Report

	Base	PR	Delta
src/server/request_handler/default_request_handler.ts	82.02%	81.88%	🔴 -0.14%
src/server/utils.ts	63.63%	69.23%	🟢 +5.60%
Total	87.81%	87.76%	🔴 -0.05%

Generated by coverage-comment.yml

[gemini-code-assist]

Code Review

This pull request introduces stream ordering enforcement for agent responses, ensuring they follow either a message-only or a task-lifecycle pattern. While the logic correctly filters events in the response stream, two significant issues were identified: invalid events are still being persisted to the TaskStore because validation occurs after processing, and the message-only pattern check is currently unreachable due to the underlying event queue's termination behavior. Additionally, one of the new unit tests needs to be updated to actually simulate the out-of-order events it intends to verify.

[gemini-code-assist]

Code Review

This pull request introduces stream ordering validation within the DefaultRequestHandler to enforce specific patterns for streaming responses, such as 'message-only' or 'task-lifecycle'. It includes a new StreamPattern enum and logic to skip events that violate the expected sequence. The review feedback suggests that protocol violations should result in an explicit UnsupportedOperationError being thrown rather than just logging a warning and skipping the event, ensuring the client is properly notified of the failure.

[gemini-code-assist]

Code Review

This pull request implements stream ordering enforcement in the DefaultRequestHandler to align with protocol specifications. It introduces a StreamPattern state machine that tracks whether a response follows a message-only or task-lifecycle pattern, throwing errors for invalid event transitions. Feedback focuses on strictly prohibiting subsequent 'task' events within a task-lifecycle stream and refining error messages to correctly identify valid initial event types.

[gemini-code-assist]

Code Review

This pull request implements stream ordering enforcement for agent execution events by introducing a StreamPattern enum and validation logic. The changes ensure streams follow either a message-only or task-lifecycle pattern, throwing errors for invalid sequences. Review feedback correctly identified a bug in the error handling logic that would cause an ordering violation and a potential hang, along with an incomplete test case that failed to properly verify the message-only enforcement.