
AI Gateway logs now show session affinity
Quick Answer
Vercel AI's AI Gateway now features a Sessions view in logs, allowing users to track session affinity for requests.
Quick Take
This includes details on coding agents like Claude Code and Codex, along with metrics such as cache hit rates and session costs, enhancing request routing efficiency.
Key Points
- Sessions view groups requests by session, showing details like model and cost.
- Session affinity routes requests to the same provider for better cache utilization.
- Users can filter sessions by various criteria, including client and model.
- Single-turn sessions are hidden until the minimum turns filter is cleared.
- Default session affinity applies to text and chat requests.
📖 Reader Mode
~1 min readAI Gateway logs now have a Sessions view that groups requests into sessions and shows how session affinity routed each one. Each row shows the coding agent or app that ran the session, such as Claude Code, Codex, or Cursor, along with its cost, models, providers, and how much of its input was cached across every turn.
Open a session to see its cache hit rate, duration, and path. The path lists each turn with its model and timing, and names the provider serving the session along with any earlier ones. Session affinity sends each turn to the provider that served the one before it, so the provider already has most of the prompt in cache. A session that stays on one provider reads more of each prompt from cache.
Filter sessions by turns, client, model, provider, authentication, or cost. Single-turn sessions are hidden until you clear the minimum turns filter.
Session affinity runs by default on text and chat requests. To group requests yourself, send the same sessionId in providerOptions.gateway, or the same x-session-id header, on every request in a conversation. Requests without one are grouped by a fingerprint of the conversation's opening and appear as fingerprinted sessions.
Read the session affinity documentation for more information on how AI Gateway identifies sessions.
— Originally published at vercel.com
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The Agent Stack
The Agent Stack by Vercel AI provides essential building blocks for creating production-grade agents, enabling seamless integration across multiple AI models and secure operations. It features components like AI Gateway for model routing, Workflow SDK for durable execution, and Vercel Connect for scoped access, streamlining agent development and deployment across various platforms.

