🛠️ MiMo-V2.6 update: tool-call repetition, diagnosed & fixed.
After the MiMo-V2.6 series models launched, we noticed them sometimes repeating identical or highly similar tool calls — burning context and stalling tasks, especially in MiMo Desktop, MiMo Code and OpenCode.
Root cause
A "reward blind spot" in scaling RL: when rewards only track final-answer correctness, inefficient behaviors along the way go unnoticed — and get amplified as training scales. Concretely, our flooding penalty only kicked in at >32 tool calls per turn, so anything below that threshold went completely unpunished.
The fix
We trained a light-weight repetition-specialized RL teacher — just 12 steps, ~7k examples — and merged it into the main model via MOPD, at roughly 4% of the cost of a full mixRL retrain. Repetition dropped sharply across harnesses and context lengths, while benchmarks held steady.
📦 Updated models, open-sourced (MOPD suffix):
📝 Full postmortem:
Huge thanks to our community for the patience and feedback 🙏 Updated models go live on our API platform Sep 25, 06:00 (UTC+8), names unchanged. And for MiMo Desktop users: everyone's remaining quota in the current window will be reset.