Maple agent tracing: eve

Goal

One eve session (wrun_...) = one Maple Agent Session. One user message = one turn = one trace rooted at invoke_agent <agent>, with agent.step spans holding a chat <model> span (model, provider, tokens, messages) and execute_tool <tool> spans (arguments, result, failures). Subagents nest inside the caller's trace and show as their own lanes.

eve owns the tracer provider and writes gen_ai.conversation.id (the root session id) on every agent span. You add a destination; you never start an SDK and never pass a conversation id.

Known gaps (tell the user, don't try to fix):

• Outside eve dev, message content is exported only for public conversations (Step 4).
• Cost shows as unpriced with a model called directly at its provider. With Vercel AI Gateway, eve writes gen_ai.usage.cost on the agent.step span; Maple counts it in the session total (the per-model table has tokens, not cost).
• eve does not log failed exports (Step 6).

Step 0: Detect