How to design a multi-agent system that skips the LLM

Github repo → https://goo.gle/race-condition Previous episode → https://goo.gle/marathonagent A thousand AI agents run a marathon, and almost none of them ever call the LLM. In this multi-agent system deep dive, Casey West breaks down the one architectural decision behind Race Condition: a 1000-agent system built on Google's Agent Development Kit (ADK). The question every AI engineer is wrestling with: when do you let an LLM decide, and when do you just write the code in a multiagent system? We trace one decision end to end, planning a marathon route, then show how the same idea (skip the LLM where you don't need it) scales to a thousand agents running on deterministic code. What you'll learn: * When to use an LLM vs deterministic logic * The before_model_callback trick, keep the agent, skip the model * Why route planning is deterministic (NP-hard + the Spine & Sprout algorithm) * How 1,000 autopilot runners make 0 LLM calls * Where the tokens actually go (the AI decides, the code runs) * Scaling 1,000 stateless sessions with Redis Chapters 00:00 - Intro: 1,000 AI agents that don't call the LLM 00:41 - When should an agent use an LLM? 01:02 - [Demo] Planning a marathon route 01:59 - Why Google Maps can't route a marathon 05:08 - Why the LLM Is the wrong tool (NP-hard) 05:40 - The deterministic spine & sprout algorithm 06:58 - Using AI Studio to choose the algorithm 09:00 - The trick: Skip the LLM with a callback 12:26 - before_model_callback — the reveal 17:50 - Autopilot runners: 1,000 agents, 0 LLM calls 21:31 - How many tokens? Where they actually go 23:28 - The second cost: Session state & redis 29:05 - Wrap up More resources: Google Agent Development Kit (ADK) → https://goo.gle/3PItVzL Google ADK Community (Redis session service) → https://goo.gle/4ugzmUw Agent Runtime → https://goo.gle/4nXDhnX Google Cloud Memory Store → https://goo.gle/4nXxBtT Agent2Agent Protocol (A2A) protocol → https://goo.gle/4u5x8HF Casey West on LinkedIn → https://goo.gle/4dXnsJr Annie Wang on LinkedIn → https://goo.gle/43GCXAo Watch more Hands on AI → https://www.youtube.com/playlist?list=PLIivdWyY5sqKnJOvP89yF8t9mWuzMTcbM 🔔 Subscribe to Google Cloud Tech → https://goo.gle/GoogleCloudTech #AIAgent #GoogleADK #Gemini #MultiAgentSystem #AgenticAI #GoogleCloud Speakers: Casey West, Annie Wang Products Mentioned: Google Agent Development Kit, Gemini API, Agent Runtime, Google Cloud Pub/Sub, AlloyDB, Agent2Agent Protocol