fix(ai): forward google vertex base url

closes #3619

packages/ai/test/google-vertex-api-key-resolution.test.ts

@@ -32,6 +32,9 @@ vi.mock("@google/genai", () => {
 
 	return {
 		GoogleGenAI,
+		ResourceScope: {
+			COLLECTION: "COLLECTION",
+		},
 		ThinkingLevel: {
 			THINKING_LEVEL_UNSPECIFIED: "THINKING_LEVEL_UNSPECIFIED",
 			MINIMAL: "MINIMAL",
@@ -44,7 +47,7 @@ vi.mock("@google/genai", () => {
 
 import { getModel } from "../src/models.js";
 import { streamGoogleVertex } from "../src/providers/google-vertex.js";
-import type { Context } from "../src/types.js";
+import type { Context, Model } from "../src/types.js";
 
 const model = getModel("google-vertex", "gemini-3-flash-preview");
 const context: Context = {
@@ -141,4 +144,80 @@ describe("google-vertex api key resolution", () => {
 		expect(googleGenAiMock.constructorCalls[0]).not.toHaveProperty("project");
 		expect(googleGenAiMock.constructorCalls[0]).not.toHaveProperty("location");
 	});
+
+	it("does not forward generated Vertex base URL placeholders", async () => {
+		const stream = streamGoogleVertex(model, context, {
+			project: "test-project",
+			location: "us-central1",
+		});
+
+		await stream.result();
+
+		expect(googleGenAiMock.constructorCalls).toHaveLength(1);
+		expect(googleGenAiMock.constructorCalls[0]?.httpOptions).toBeUndefined();
+	});
+
+	it("forwards custom baseUrl to the ADC client", async () => {
+		const customModel: Model<"google-vertex"> = { ...model, baseUrl: "https://proxy.example.com" };
+		const stream = streamGoogleVertex(customModel, context, {
+			project: "test-project",
+			location: "us-central1",
+		});
+
+		await stream.result();
+
+		expect(googleGenAiMock.constructorCalls).toHaveLength(1);
+		expect(googleGenAiMock.constructorCalls[0]).toMatchObject({
+			vertexai: true,
+			project: "test-project",
+			location: "us-central1",
+			apiVersion: "v1",
+			httpOptions: {
+				baseUrl: "https://proxy.example.com",
+				baseUrlResourceScope: "COLLECTION",
+			},
+		});
+	});
+
+	it("forwards custom baseUrl to the API key client", async () => {
+		const customModel: Model<"google-vertex"> = { ...model, baseUrl: "https://proxy.example.com" };
+		const stream = streamGoogleVertex(customModel, context, {
+			apiKey: "AIzaSyExampleRealisticLookingApiKey123456",
+		});
+
+		await stream.result();
+
+		expect(googleGenAiMock.constructorCalls).toHaveLength(1);
+		expect(googleGenAiMock.constructorCalls[0]).toMatchObject({
+			vertexai: true,
+			apiKey: "AIzaSyExampleRealisticLookingApiKey123456",
+			apiVersion: "v1",
+			httpOptions: {
+				baseUrl: "https://proxy.example.com",
+				baseUrlResourceScope: "COLLECTION",
+			},
+		});
+	});
+
+	it("does not append apiVersion when custom baseUrl already includes one", async () => {
+		const customModel: Model<"google-vertex"> = {
+			...model,
+			baseUrl: "https://proxy.example.com/v1/projects/test-project/locations/global",
+		};
+		const stream = streamGoogleVertex(customModel, context, {
+			project: "test-project",
+			location: "us-central1",
+		});
+
+		await stream.result();
+
+		expect(googleGenAiMock.constructorCalls).toHaveLength(1);
+		expect(googleGenAiMock.constructorCalls[0]).toMatchObject({
+			httpOptions: {
+				baseUrl: "https://proxy.example.com/v1/projects/test-project/locations/global",
+				baseUrlResourceScope: "COLLECTION",
+				apiVersion: "",
+			},
+		});
+	});
 });