V 2 Sessions Create

V2 agent chat — single loop with two-tier tool loading.

POST /agents/v2/sessions/ (auto-generates session_id) POST /agents/v2/sessions/<session_id>/turns/ (explicit session_id)

Request body: same as v1 (input, timezone, conversation, parent_message_id, model). Response: Server-Sent Events stream.

Differences from v1:

• Single loop instead of multi-agent graph
• Two-tier tool loading (~20 core, ~70 deferred via tool_search)