Modal releases Spindle, an open-source Tinker-compatible training server

Modal released Spindle, an open-source, Tinker-compatible training server that runs in a customer's Modal workspace, letting teams customize the stack and pay for GPU time instead of tokens. Spindle supports full-parameter training and multi-LoRA across open models, and Modal reports that sharing one trainer across 8 clients cut cost per 1M output tokens by up to 80% versus Tinker on a DAPO-math GRPO job. Modal says Spindle is still in beta and positions it between its Dojo training library and raw cluster primitives.