OpenAI's GPT-5.6 Sol launches to rival Claude Mythos under government access rules it calls unsustainable

2026-06-26 · Source: The Decoder · Field: Technology & Digital — Artificial Intelligence & Machine Learning, Cybersecurity & Data Privacy · Depth: Intermediate, short

Summary

OpenAI has launched its new GPT-5.6 generation, featuring the flagship Sol, alongside cheaper Terra and Luna tiers. GPT-5.6 Sol claims to match or surpass Anthropic's Claude Mythos 5 across various benchmarks, notably leading in agentic coding with an 88.8 percent score on Terminal-Bench 2.1 (Sol Ultra reaching 91.9 percent) compared to Mythos 5's 88 percent. Sol also demonstrates improved token efficiency in cybersecurity on ExploitBench, matching Mythos Preview's performance using roughly a third of output tokens. Despite these advancements, access to GPT-5.6 Sol is currently restricted to select partners by the US government, a policy OpenAI publicly criticizes as detrimental to developers and businesses. The new models introduce a tiered pricing structure, with Sol costing \$5 input and \$30 output per million tokens, and are slated for a July launch on Cerebras, offering up to 750 tokens per second.

Key takeaway

For Directors of AI/ML evaluating next-generation models, OpenAI's GPT-5.6 Sol presents a compelling option, outperforming Claude Mythos 5 in agentic coding and demonstrating superior token efficiency in cybersecurity. While its \$5 input/\$30 output pricing per million tokens might seem high, its efficiency could lower your effective task costs. However, current US government restrictions mean you cannot widely deploy Sol yet. Monitor policy developments closely to capitalize on its capabilities once broader access becomes available.

Key insights

OpenAI's GPT-5.6 Sol rivals Claude Mythos in performance, but government restrictions limit its immediate availability.

Principles

• Agentic coding and cybersecurity are key AI model benchmarks.
• Token efficiency reduces effective LLM operational costs.
• Government policy can restrict advanced AI model access.

Method

GPT-5.6 offers "max" mode for deeper reasoning and "ultra" mode, which dispatches complex tasks to parallel sub-agents for enhanced performance.

In practice

• Utilize Sol for agentic coding tasks.
• Deploy Sol for cybersecurity flaw detection.
• Evaluate Sol's token efficiency for cost savings.

Topics

• OpenAI GPT-5.6 Sol
• Claude Mythos
• AI Benchmarking
• Agentic Coding
• Cybersecurity AI
• AI Regulation

Best for: AI Engineer, Machine Learning Engineer, Investor, Tech Journalist, AI Scientist, Director of AI/ML

Related on AIssential

• OpenAI just dropped GPT-5.5... (WOAH) — GPT 5.5 offers higher intelligence and token efficiency, especially for agentic coding and knowledge work, at a lower effective cost.
• #openai GPT 5.6 - What, Availability, Pricing — OpenAI's GPT 5.6 introduces tiered models and aggressive pricing, with its rollout subject to US government approval.
• Previewing GPT-5.6 Sol: a next-generation model — OpenAI's GPT-5.6 series enhances AI capabilities across domains while integrating a multi-layered safety framework and new reasoning modes.
• OpenAI launches GPT-5.4 Thinking and Pro combining coding, reasoning, and computer use in one model — GPT-5.4 unifies coding, reasoning, and computer operation, significantly boosting performance in professional knowledge work and desktop navigation.
• GPT 5.4 Mini in 5 mins! — OpenAI's new GPT 5.4 Mini offers competitive performance with significantly lower latency and cost for agentic and vision tasks.
• OpenAI's GPT-5.4-Cyber rejects Mythos playbook — OpenAI and Anthropic are pursuing divergent strategies for advanced AI model access in cybersecurity.

Open in AIssential →

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