Splitting the agent into three interfaces — an append-only session log, a stateless 'brain' (the Claude agent loop), and on-demand 'hands' (sandboxes, MCP servers, customer VPCs) — cuts p90/p95 time-to-first-token by 90% because inference no longer waits on container boot; the session log is the sole join point between brain and hands.
Latency for agent startup is usually dominated by provisioning/booting the execution environment, not by model inference. If the log is the only shared state, the brain can start inferring before any hand exists, converting a boot-bound problem into an I/O-bound one.
Any agent runtime can decouple the reasoning loop from the execution environment by making a durable event log the contract, then provisioning executors lazily per tool call rather than per session.
Decoupling the brain from the hands reduced p90/p95 time-to-first-token by 90%.
one brain reaching multiple hands (sandbox containers, customer VPCs, MCP servers)
when a sandbox dies, inference retries immediately