Ox Alpha and Solar Pro 4 are available through the OpenRouter API, so switching between them takes a model slug change rather than a new integration.
Ox Alpha, from Stealth, has a 1,048,576-token context window and is free to use on OpenRouter.
Solar Pro 4, from upstage, has a 524,288-token context window and is priced at $0.03/M tokens input, $0.12/M tokens output on OpenRouter.