OpenAI Launches GPT-6.1 Sol API with Lower Cache Pricing and Revised Reasoning Options

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OpenAI introduced GPT-6.1 Sol at DevDay on September 29, 2026, as an updated successor to the GPT-6 Sol model. The new model is accessible via a POST request to the Responses API endpoint using the model ID 'gpt-6.1-sol', with standard input and output pricing unchanged at $2 and $10 per million tokens respectively. However, cached input pricing has been halved from $0.20 to $0.10 per million tokens. A key breaking change for developers migrating from GPT-6 Sol is that the 'none' and 'minimal' values for the reasoning.effort parameter are no longer accepted and must be remapped to 'low'. Additionally, function calling via the Chat Completions endpoint is no longer supported in GPT-6.1 Sol, requiring developers to shift tool calls to the Responses API.

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