GPT-5.6 Sol

GPT-5.6 Sol is the flagship in OpenAI's GPT-5.6 family, previewed on June 26, 2026 and generally available since July 9, 2026. Access at launch was intentionally narrow: at the request of the US Government, only roughly 20 pre-approved organizations were granted entry to the limited preview. On August 21, 2026 OpenAI cut the Sol rate for the first time since GPT-5.5 set $5/$30 back in April. Input fell from $5 to $4 per million tokens, output from $30 to $20, and cached input from $0.50 to $0.40. OpenAI lists the new rate as promotional and good through at least November 21, 2026, so budget for a revert rather than treating it as the new floor. The cut covers the pay-as-you-go API, Codex credits, and eligible ChatGPT Work plans; Pro, Plus, and Business subscription prices are unchanged. The context window is 1 million tokens. OpenAI positioned Sol for frontier reasoning and agentic work and disclosed partial benchmarks at preview (Sol Ultra at 91.9 percent on Terminal-Bench 2.1, base Sol at 88.8 percent), with a fast mode available at twice the standard rate for roughly 2.5 times the throughput. On September 22, 2026 OpenAI released GPT-6 Sol at $2/$10, half the promotional GPT-5.6 Sol rate and permanent rather than promotional.