JM 💙 JUNERS Another GPT-5.6 model has arrived on @askjuneai and this one completes the lineup with OpenAI's most capable reasoning model: GPT 5.6 Sol. After reviewing the official specifications and updating my article, these are the highlights that stand out the most. 🧠 Built for frontier reasoning GPT 5.6 Sol isn't just an incremental upgrade. It's designed for the kind of work where other models begin to struggle: long-running reasoning, complex software engineering, deep research, cybersecurity, scientific analysis, and multi-step agentic workflows. Its objective is simple: stay focused on difficult problems for much longer while producing reliable, high-quality results. ⚙️ Technical highlights • 1M token context window • Up to 128K output tokens • Knowledge cutoff: February 16, 2026 • Optimized for sustained multi-step reasoning • Lower token usage and faster execution than several competing frontier models 📊 Performance According to the published benchmarks, GPT 5.6 Sol establishes new state-of-the-art results across multiple professional evaluations. It achieves: • 53.6 on Agents' Last Exam • 80 on the Artificial Analysis Coding Agent Index • 92.2% on BrowseComp • 62.6% on OSWorld 2.0 Beyond benchmark scores, one detail is particularly interesting: OpenAI reports that Sol completes many complex workflows using less than half the output tokens, in less time, and at roughly one-third of the cost compared with Claude Fable 5 for the evaluated scenarios. 🎯 When would I choose GPT 5.6 Sol? If the task involves: • Advanced system architecture • Complex coding projects • Long research sessions • Multi-day agentic workflows • Scientific or technical analysis • Problems where accuracy matters more than raw speed This is the model I would reach for first. The combination of a massive context window, frontier reasoning, and sustained focus makes it the strongest option in the GPT-5.6 family for demanding professional workloads. If you're interested in the complete technical breakdown—including architecture, benchmarks, reasoning profile, strengths, pricing, and recommended use cases—you can find it in my updated Chat Models article on June. The GPT-5.6 family is now complete on June, and it's been interesting to watch how consistently the team has expanded the platform over the past few days. Privacy 🔏 first One platform. Multiple models. Consistency compounds.