NVFP4 forward, MXFP8 backward with stochastic rounding: how Inkling 2 Small was trained

snowclipsed · x · 2026-11-14

The author calls the recipe a small surprise versus other NVFP4 approaches but an agreeable, great decision. Quoting the blog: Inkling 2 Small uses NVFP4 precision in expert layers for forward passes with a dedicated kernel, MXFP8 for backward passes with re-quantization and stochastic rounding to reduce gradient bias, plus quantization techniques to accelerate GPU communications. It is the largest known model trained end-to-end with a native 4-bit forward pass, configured identically from pretraining through final RL rollouts, eliminating checkpoint calibration.

Related event: Thinking Machines Details End-to-End Native 4-Bit Training for Inkling 2 Small(7 posts)→

Original post →

More from Infra

Infra channel →