GLM 5.3 Flash vs Claude Fable 5.1

Z.ai's first natively multimodal model in the GLM-5 family, built for efficient coding and visual work. GLM 5.3 Flash reads text, images, and video, and can observe interfaces and rendered output to test and refine its own code. A hybrid sparse-and-linear attention design keeps long-context work fast and cheap. It holds a very large context and approaches the larger GLM-5.3 on coding at a fraction of the cost. Open weights under an MIT license.

Anthropic's most capable generally available model, sitting above the Opus line. Fable 5.1 is built for long, unsupervised work: multi-day coding, agentic research, and tasks that run across dozens of tool calls. It reads text and images, maintains a very large context, and reasons before every answer at an adjustable depth. Its knowledge is the most recent of any Claude model. Anthropic positions Opus 5 as the starting point for most work, and Fable 5.1 for teams whose evaluations demand a higher ceiling.