Granite 4.2 8B and GPT-5.6 Terra are available through the OpenRouter API, so switching between them takes a model slug change rather than a new integration.
Granite 4.2 8B, from ibm-granite, has a 131,072-token context window and is priced at $0.10/M tokens input, $0.15/M tokens output on OpenRouter.
GPT-5.6 Terra, from OpenAI, has a 1,050,000-token context window and is priced at $2/M tokens input, $12/M tokens output on OpenRouter.