Together AI said GLM-5.3 now beats GPT-5.6 Sol and Claude Fable 5 on agentic benchmarks, with GLM-5.3 Flash close behind. Zhipu kept the GLM-5.2 base and scaled post-training—more long-horizon environments, more diverse tasks, and more RL compute—rather than training a new foundation model. For coding agents, that is a claim that post-training stack height can overtake closed flagships, and that the cheaper open-weight default is already on Together’s API.

Key Takeaways

  • ✓Together reports GLM-5.3 ahead of GPT-5.6 Sol and Claude Fable 5 on agentic benchmarks; Flash is next.
  • ✓The gain is post-training on the GLM-5.2 base: more long-horizon RL, not a new pretrained model.
  • ✓Coding agents can switch to a cheaper open-weight default without waiting on a new foundation run.
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