Together Post-Training

Together AI launches Together Post-Training, a service for RL and SFT on open models where users write the training loop

Together AI published this on Oct 19, 2026 (source: together.ai).

Together AI introduced Together Post-Training, a service for building custom models from open-weight LLMs with reinforcement learning from environment rewards or supervised fine-tuning. Users define the training loop themselves, including custom losses, LoRA or full-weight training for select models, and their own data, environments and agent harnesses, while Together runs the trainer and rollout infrastructure on dedicated GPU allocations billed per GPU-minute. It launches with Muse Spark Open, GLM 5.3, Kimi K3 and Qwen 3.8-27B, and Together offers a one-line migration for scripts written for the Tinker API. For the first eight weeks, Together is charging a reduced $9 per B200 GPU-hour.