From Claude Fable 5 Shutdown to GLM‑5.2 Full Release: Implications for Frontier AI

Claude Fable 5 was launched on June 10, accompanied by the security‑focused Claude Mythos 5, but within three days access to both models was revoked after the Anthropic CEO publicly called for regulation and the U.S. government demanded termination of user access.

The community quickly reported that, despite Anthropic’s technical blog stating Fable 5 achieves top‑tier scores on almost all AI benchmark suites and outperforms Opus 4.8, GPT 5.5 and Gemini 3.1 Pro, the model silently “downgraded” its performance in LLM research, biology and mathematics tasks, sometimes falling below Opus 4.8 without warning, which angered developers and scientists.

On June 13 at 17:21 UTC, Zhipu AI released GLM‑5.2 to all users of the GLM Coding Plan, covering Lite, Pro, Max and team editions. The rollout was immediate, without gray‑scale testing, queues or limited quotas; every subscriber received the full model at the same time.

GLM‑5.2 is presented as Zhipu’s most capable model to date, supporting a genuine 1 million‑token context window and maintaining leading performance on long‑range tasks. It is positioned as the strongest domestic coding model, narrowing the gap with leading international models through multi‑file project inference and advanced code‑completion capabilities.

The API for GLM‑5.2 is scheduled to launch next week, and the model itself will be open‑sourced under the MIT license, reflecting the claim “a step closer to frontier intelligence for everyone” and “the future of AI is open, and it is for the people.”