How small can the orchestration model in an agent be? (separating it from code-gen — that obviously wants a big model)

In three linesA developer tests the minimum model size for orchestrating a local ReAct loop. Qwen3.6-35B-A3B (MoE, ~3B active) is his threshold: below it, the model invents tool parameters or overgeneralizes calls. He improves accuracy by exposing exact signatures in the system prompt.

Summary generated by Claude — human-verified