Python: [Bug]: ClaudeAgent.run_stream() silently ignores API errors and AssistantMessage responses

[droideronline]

Description

The run_stream() method in ClaudeAgent only processes StreamEvent and ResultMessage types from self._client.receive_response(), but:

1. AssistantMessage is completely ignored - When the Claude SDK returns an AssistantMessage (which contains the actual response text or error messages), it's silently dropped because there's no handler for it.

2. ResultMessage.is_error is never checked - The code only extracts session_id from ResultMessage and ignores the is_error flag and error content.

Impact

When an API error occurs (e.g., invalid model name returning 404), the agent returns empty results (result.text = "", result.messages = []) with no exception raised. The error message is buried in an AssistantMessage that gets silently dropped.

Expected Behavior

• Check ResultMessage.is_error and raise ServiceException when true
• Process AssistantMessage to extract response text or propagate errors
• Surface API errors as exceptions instead of returning empty results

Code Sample

# Using invalid model claude-sonnet-4.5
async with ClaudeAgent(default_options={"model": "claude-sonnet-4.5"}) as agent:
    response = await agent.run("Hello")
    # Returns empty response instead of raising error
    print(response.text)  # ""

Error Messages / Stack Traces

No error is raised - that's the bug. The API returns a 404 error but it's silently ignored.

Package Versions

agent-framework-claude: latest (main branch)

Python Version

Python 3.13

Operating System

macOS