[rioyu123]

Summary

When a workflow task is appended, AgentContext.add_workflow_task and the reasoning-summary done handler in stream_agent_response compute task_index with workflow.tasks.index(task). Tasks are Pydantic models compared by value, so a task equal to an earlier one gets the earlier task's index. The second task is stored at position 1, but its WorkflowTaskAdded event says task_index=0.

Use len(tasks) - 1 immediately after the append, which is where the task was actually stored. Indices for distinct tasks are unchanged.

Tests

• Added coverage for both the queued custom-task event and the emitted reasoning-summary event, with equal-task cases and distinct-task controls.
• All four cases pass with the fix. On the base commit, the two equal-task cases fail and the controls pass.
• Full suite: 134 tests passed.
• Ruff check, changed-file formatting and Pyright pass.
• mypy . stops at the same duplicate-module discovery error for tests/_types.py on both base and this branch; no Mypy pass is claimed.

Scope

This fixes the index in the emitted WorkflowTaskAdded event. No browser or live model API run was performed. Index lookups for task updates are unchanged.