fix(ai/core): properly handle custom separator in provider registry (#5713) (#5732)

Co-authored-by: Anatol Zakrividoroga <53095479+anatolzak@users.noreply.github.com>

Author: lgrammel

.changeset/six-moose-know.md

@@ -0,0 +1,5 @@
+---
+'ai': patch
+---
+
+fix(ai/core): properly handle custom separator in provider registry

packages/ai/core/registry/provider-registry.test.ts

@@ -109,6 +109,30 @@ describe('languageModel', () => {
 
     expect(modelRegistry.languageModel('provider|model')).toEqual(model);
   });
+
+  it('should support custom separator with multiple characters', () => {
+    const model = new MockLanguageModelV2();
+
+    const modelRegistry = createProviderRegistry(
+      {
+        provider: {
+          languageModel: id => {
+            expect(id).toEqual('model');
+            return model;
+          },
+          textEmbeddingModel: () => {
+            return null as any;
+          },
+          imageModel: () => {
+            return null as any;
+          },
+        },
+      },
+      { separator: ' > ' },
+    );
+
+    expect(modelRegistry.languageModel('provider > model')).toEqual(model);
+  });
 });
 
 describe('textEmbeddingModel', () => {

packages/ai/core/registry/provider-registry.ts

@@ -126,7 +126,7 @@ class DefaultProviderRegistry<
       });
     }
 
-    return [id.slice(0, index), id.slice(index + 1)];
+    return [id.slice(0, index), id.slice(index + this.separator.length)];
   }
 
   languageModel<KEY extends keyof PROVIDERS>(