Robostral Navigate's training is entirely conducted in simulation. Mistral built a data generation pipeline producing approximately 400,000 trajectories covering 6,000 virtual scenes. Training employs prefix caching, reducing the number of training tokens per time step by 22×, thus compressing what would have taken months into a few days.
After supervised training, Mistral introduced online reinforcement learning based on CISPO, allowing the model to learn self-correction and exploration through trial and error. On the R2R-CE benchmark, this step increased success rate by an additional 3.2 percentage points, and the company says no performance bottleneck has been observed. “We are confident that more training and experiments will continue to push this number higher.”
Notably, Mistral claims the model is entirely self-developed, not relying on any open-source vision-language model, but initialized from its internal vision-language model proficient in grounding tasks such as pointing, counting, and object localization.