Claude Opus 5 and GPT-5.6 Sol Pro are available through the OpenRouter API, so switching between them takes a model slug change rather than a new integration.
Claude Opus 5, from Anthropic, has a 1,000,000-token context window and is priced at $5/M tokens input, $25/M tokens output on OpenRouter.
GPT-5.6 Sol Pro, from OpenAI, has a 1,050,000-token context window and is priced at $5/M tokens input, $30/M tokens output on OpenRouter.