GPT-5.6 Sol
OpenAI · Multimodal model
GPT-5.6 Sol was OpenAI's flagship from the GPT-5.6 family released in mid-2026, before the GPT-6 launch in September. It remains in the API but has been overtaken by GPT-6 Astra and GPT-6.1 Sol.
Legacy model
ReleasedJul 2026
Context window1.05M tokens (922K max input, 128K max output)
Input → outputtext, image → text
API price$4 / 1M input tokens, $0.40 / 1M cached input tokens, $20 / 1M output tokens
Consumer access—
Best for
Existing integrations built on the GPT-5.6 generation that have not yet migrated to GPT-6.
Overview
GPT-5.6 Sol was OpenAI's flagship from the GPT-5.6 family released in mid-2026, before the GPT-6 launch in September. It remains in the API but has been overtaken by GPT-6 Astra and GPT-6.1 Sol.
Strengths and limits
- Former OpenAI flagship for complex professional work
- Still available in the API with a 1M+ token context
- Some users prefer its depth of answers over GPT-6 models
- Scores well below GPT-6 Astra and Claude 5.x models on recent agentic benchmarks
- Costs more per token than GPT-6.1 Sol, which outperforms it
Published benchmark scores
Terminal-Bench 4.037.3%
Source: www.anthropic.com
HealthBench Professional60.5
Source: deploymentsafety.openai.com
Scores are as published by the source; settings (reasoning effort, tools, attempts) differ between labs, so compare with care. How to read benchmarks →