Claude Mythos 5: Most Powerful Model Ever! AGI, GLM 5.1, Claude Code Update & Codex Plugins! AI NEWS

2026-03-28 · Source: WorldofAI · Field: Technology & Digital — Artificial Intelligence & Machine Learning, Software Development & Engineering, Robotics & Autonomous Systems · Depth: Intermediate, long

Summary

This week saw significant developments in AI, including a major leak from Anthropic revealing two new models: Claude Mythos and Capybara. Mythos is described as a "new frontier tier" with enhanced coding, academic reasoning, and cybersecurity capabilities, reportedly surpassing the current flagship Opus model. Anthropic is planning a slow rollout due to misuse concerns. Concurrently, GLM 5.1, an open-source agentic model, was released, demonstrating strong performance in long-running tasks and scoring 45.3 on coding benchmarks, close to proprietary models like Opus 4.6. Google DeepMind introduced Gemini 3.1 Flash Live, a real-time multimodal model for voice and vision agents, featuring lower latency. OpenAI launched plugins for Codex, transforming it into a full execution environment for pre-built AI workflows, directly competing with Claude Code. Additionally, the Arc AGI 3 benchmark was introduced to measure agentic reasoning in interactive environments, with current AI models scoring under 1%, while Mistral AI released Vauxhall TTS for expressive, low-latency text-to-speech in nine languages.

Key takeaway

For AI Engineers evaluating new model capabilities, the rapid advancements from Anthropic's leaked Mythos and the release of GLM 5.1 signal a critical shift. You should prioritize exploring agentic models for complex, multi-step tasks and consider integrating real-time multimodal AI like Gemini 3.1 Flash Live into your applications. The new Arc AGI 3 benchmark also provides a more robust measure of true AI intelligence, guiding future development efforts.

Key insights

Frontier AI models are rapidly advancing in capabilities, pushing boundaries in agentic behavior, real-time multimodal interaction, and coding.

Principles

• Open-source models are closing the gap with proprietary AI.
• Agentic AI requires robust multi-step workflow reliability.
• Benchmarks should test interactive reasoning, not just memorization.

Method

OpenAI's Codex plugins create a full execution environment, allowing users to launch pre-built, modifiable AI workflows for tasks like app building and data analysis with one click.

In practice

• Explore GLM 5.1 for affordable, agentic open-source AI.
• Utilize OpenAI Codex plugins for pre-built coding workflows.
• Consider Gemini 3.1 Flash Live for real-time voice/vision agents.

Topics

• Claude Mythos
• Capybara
• GLM 5.1
• Gemini 3.1 Flash Live
• OpenAI Codex Plugins

Best for: AI Engineer, NLP Engineer, CTO, AI Scientist, Machine Learning Engineer, Director of AI/ML

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Editorial summary, takeaway, and curation by AIssential. Original article published by WorldofAI.