Step 3.5 Flash and GTE-Large are available through the OpenRouter API, so switching between them takes a model slug change rather than a new integration.
Step 3.5 Flash, from stepfun, has a 262,144-token context window and is priced at $0.10/M tokens input, $0.30/M tokens output on OpenRouter.
GTE-Large, from thenlper, has a 512-token context window and is priced at $0.01/M tokens on OpenRouter.