YC's Multiplayer Agent Harness: Great Decoupled Architecture, But It Kills KV Cache
Instance_Not_Found · reddit · 2026-08-05
A developer reviewed the source code of YC's multiplayer agent harness (QM), highlighting both its strengths and flaws:
- The Good (Decoupled Architecture): Qm separates session logs, headless agent runtimes, and sandboxes. Previously, a sandbox crash meant losing all progress; now, tasks can resume from the last checkpoint thanks to session logging.
- The Ugly (Performance Hit): The core orchestrator spawns a new Claude Code child process every turn, reconstructing all user, assistant, and tool-call records. This approach essentially gives up the KV Cache entirely, which will cause API bills to skyrocket.
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