GLM-5.1: Towards Long-Horizon Tasks

2026-04-07 · Source: Simon Willison's Weblog · Field: Technology & Digital — Artificial Intelligence & Machine Learning, Software Development & Engineering · Depth: Intermediate, quick

Summary

Z.ai, a Chinese AI lab, released GLM-5.1 on April 7, 2026, a 754B parameter, 1.51TB model available on Hugging Face and OpenRouter under an MIT license. This model, the same size as its predecessor GLM-5, demonstrated an unexpected capability to generate not only SVG images but also accompanying CSS animations without explicit prompting. When tasked to generate an SVG of a pelican on a bicycle, GLM-5.1 produced an excellent SVG and CSS animations, though the initial animation broke the pelican's positioning. Upon receiving a follow-up prompt describing the issue, the model accurately diagnosed the CSS `transform` conflict with SVG `transform` attributes and provided a corrected HTML output, including a detailed explanation and a working animation. Further testing with an "opossum on an e-scooter" also yielded complex, animated SVG output.

Key takeaway

For AI Engineers exploring advanced content generation, GLM-5.1's ability to autonomously produce animated SVG with CSS and self-correct based on feedback suggests a powerful new paradigm. You should experiment with iterative prompting to refine complex outputs, as this model demonstrates a capacity for sophisticated debugging and understanding of web rendering mechanics, potentially streamlining creative workflows.

Key insights

GLM-5.1 autonomously generates complex animated SVG/CSS, demonstrating advanced multimodal reasoning and self-correction capabilities.

Principles

• Models can infer complex output formats.
• Self-correction improves output quality.

Method

The model generates initial SVG and CSS, then diagnoses and corrects animation positioning issues based on user feedback, separating SVG positioning from CSS animation for proper rendering.

In practice

• Use follow-up prompts for complex output debugging.
• Explore models for multi-format content generation.

Topics

• GLM-5.1
• Z.ai
• Large Language Models
• SVG Animation
• Code Generation

Best for: AI Engineer, Machine Learning Engineer, Software Engineer

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Editorial summary, takeaway, and curation by AIssential. Original article published by Simon Willison's Weblog.