Custom model names can include the @ symbol by itself.

To specify the model's provider, append it after the model name using `@` as before.

This format supports cases like `google vertex ai` with a model name like `claude-3-5-sonnet@20240620`.

For instance, `claude-3-5-sonnet@20240620@vertex-ai` will be split by `split(/@(?!.*@)/)` into:

`[ 'claude-3-5-sonnet@20240620', 'vertex-ai' ]`, where the former is the model name and the latter is the custom provider.

app/api/common.ts

@@ -71,7 +71,7 @@ export async function requestOpenai(req: NextRequest) {
         .filter((v) => !!v && !v.startsWith("-") && v.includes(modelName))
         .forEach((m) => {
           const [fullName, displayName] = m.split("=");
-          const [_, providerName] = fullName.split("@");
+          const [_, providerName] = fullName.split(/@(?!.*@)/);
           if (providerName === "azure" && !displayName) {
             const [_, deployId] = (serverConfig?.azureUrl ?? "").split(
               "deployments/",