Aion-3.0 and Mistral Medium 3.5 are available through the OpenRouter API, so switching between them takes a model slug change rather than a new integration.
Aion-3.0, from Aion Labs, has a 131,072-token context window and is priced at $3/M tokens input, $6/M tokens output on OpenRouter.
Mistral Medium 3.5, from Mistral AI, has a 262,144-token context window and is priced at $1.50/M tokens input, $7.50/M tokens output on OpenRouter.