Together AI launches Together Post-Training: write your own RL or SFT loop on open models like GLM 5.3, Kimi K3 and Qwen 3.8-27B while Together runs the GPUs, Tinker-compatible, $9 per B200 GPU-hour for eight weeks

Why it matters

【Key points】

On Oct 19 (posted by @togethercompute at 17:07 UTC), Together AI launched Together Post-Training, a managed service for post-training open-weight models with reinforcement learning (RL) or supervised fine-tuning (SFT). Users write the whole training loop (data, rewards, environments, agent harnesses); Together runs the GPU, training and rollout infrastructure.

Launch models are Muse Spark Open, GLM 5.3, Kimi K3 and Qwen 3.8-27B, with more promised in the coming weeks. Experiments run on dedicated GPUs, with LoRA (adapters can share GPUs), full-weight training for select models, built-in losses such as GRPO, CISPO and DPPO, custom losses and asynchronous RL. Billing is per GPU-minute, with a launch price of $9 per B200 GPU-hour for the first eight weeks.

Projects built on the Tinker API can switch by changing one import line. Trained adapters can share one deployment or be merged and served in FP4. A beta has run with select customers since April.

【Verifiable】

Together AI blog: https://www.together.ai/blog/together-post-training

Docs: https://docs.together.ai/docs/post-training/overview

Tinker migration guide: https://docs.together.ai/docs/post-training/migrate-from-tinker

Cookbook repo: https://github.com/togethercomputer/post-training-cookbook

Together AI on X: https://x.com/togethercompute/status/2112229246802301248

【Our read】

1. Managed post-training is becoming its own market: Together is matching Thinking Machines' Tinker interface to win its users, a sign that "you write the loop, we run the GPUs" has real demand.

2. Three of the four launch models are Chinese open-weight models (GLM, Kimi, Qwen). Open weights plus custom post-training is becoming a main way for companies to move off closed APIs.

3. Quality, speed and cost claims are Together's own, with no comparison numbers. The $9 rate is an eight-week promotion; long-term pricing is not yet stated.