OpenAI released GPT-6.1 Sol on September 29 for complex coding and professional work at a lower cost than GPT-6 Astra. It also introduced beta multi-agent support, allowing the model to delegate work to subagents within a Responses API request.
The dated API changelog lists standard rates of $2 per million input tokens and $10 per million output tokens for prompts with up to 272,000 input tokens. Cached input costs $0.10 per million tokens; cache writes cost $2.50. Those figures are not flat prices for every prompt length or processing tier.
OpenAI describes Sol as offering near-Astra performance. Its DevDay summary lists API and Codex access where available, plus EU data residency for Standard, Flex and Batch processing.
Tool-using integrations need the Responses API. Chat Completions is available without tool calling. Multi-agent support was released as a beta, so applications still need to check delegated work rather than assume that multiple agents produce a correct result.