GLM 5.1 and Gemma 4 31B are available through the OpenRouter API, so switching between them takes a model slug change rather than a new integration.
GLM 5.1, from Z.ai, has a 204,800-token context window and is priced at $0.966/M tokens input, $3.036/M tokens output on OpenRouter.
Gemma 4 31B, from Google, has a 262,144-token context window and is priced at $0.09/M tokens input, $0.34/M tokens output on OpenRouter.