GLM 5.3

Z.ai announced GLM-5.3 on August 14, 2026 as a post-training-only upgrade that reuses the GLM-5.2 base model while scaling long-horizon training via the IndexShare long-context stack, SAO reinforcement learning, and the slime asynchronous training framework. The company claims a 50% improvement over GLM-5.2 on its in-h Z.ai positioned the release as frontier coding with emergent cyber capabilities, noting that cyber ability grew faster than expected as post-training compute increased, with the largest gains further up the exploitation chain. The blog also references security-team collaboration in China that surfaced vulnerabilities a

GLM 5.3 is a large-scale reasoning model from Z.ai, built for complex software engineering and long-horizon agent tasks. The OpenRouter listing states it was released on Aug 18, 2026 and improves on its predecessor GLM-5.2 in coding and in the balance between performance and token efficiency, while handling text input and output. The model exposes a 1M-token context window and supports tool calling and structured outputs. Reasoning is always on and cannot be disabled, with low, high, and max reasoning efforts supported and max set as the default, giving developers predictable control over compute spent per request.

SemiAnalysis InferenceX published an independent technical analysis covering both GLM-5.2 and GLM-5.3, corroborating that GLM-5.3 is a post-training-only release on the GLM-5.2 base with every gain from additional training. The page confirms GLM-5.3 is text-only, always-reasoning, with a 1M-token context, 128K max outp For licensing and availability, InferenceX reiterates that GLM-5.2 shipped as MIT-licensed open weights on Hugging Face and ModelScope with no regional limits. It also surfaces Z.ai's security-team disclosures from the GLM-5.3 blog: 2,436 vulnerabilities across 269 projects, 1,097 medium-to-high severity issues, an ave