Root cause: Codex MCP sends BOTH direct events (agent_message,
agent_reasoning_delta) AND item events (item.started/updated/completed)
for the same message content.
- User messages were emitted once by us in stream() and again 3 times
from Codex MCP's item.started/updated/completed events (4x total)
- Agent messages were emitted from both the agent_message direct event
AND the item.completed event (2x total)
Fix:
- Skip user_message items in threadItemToTimeline (we emit in stream())
- Only emit agent_message/reasoning on item.completed (skip started/updated)
- Skip direct agent_message/agent_reasoning events (use item.completed path)
Added test to verify exactly 1 user_message and 1 assistant_message per turn.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
