feat: add custom base URL support for VertexAI provider

- Add vertexBaseUrl field to provider settings schema
- Update VertexHandler to use custom base URL via GeminiHandler
- Update AnthropicVertexHandler to use custom base URL
- Add UI checkbox and input field for custom base URL in Vertex.tsx
- Add comprehensive tests for the new functionality

Fixes #7899

packages/types/src/provider-settings.ts

@@ -168,6 +168,7 @@ const vertexSchema = apiModelIdProviderModelSchema.extend({
 	vertexJsonCredentials: z.string().optional(),
 	vertexProjectId: z.string().optional(),
 	vertexRegion: z.string().optional(),
+	vertexBaseUrl: z.string().optional(),
 	enableUrlContext: z.boolean().optional(),
 	enableGrounding: z.boolean().optional(),
 })

src/api/providers/__tests__/anthropic-vertex.spec.ts

@@ -809,4 +809,95 @@ describe("VertexHandler", () => {
 			)
 		})
 	})
+
+	describe("custom base URL", () => {
+		it("should use custom base URL when provided with JSON credentials", () => {
+			const customBaseUrl = "https://custom-vertex-endpoint.example.com"
+
+			const handler = new AnthropicVertexHandler({
+				apiModelId: "claude-3-5-sonnet-v2@20241022",
+				vertexProjectId: "test-project",
+				vertexRegion: "us-central1",
+				vertexBaseUrl: customBaseUrl,
+				vertexJsonCredentials: JSON.stringify({
+					type: "service_account",
+					project_id: "test-project",
+					private_key_id: "key-id",
+					private_key: "-----BEGIN PRIVATE KEY-----\ntest\n-----END PRIVATE KEY-----\n",
+					client_email: "test@test.iam.gserviceaccount.com",
+					client_id: "123456789",
+					auth_uri: "https://accounts.google.com/o/oauth2/auth",
+					token_uri: "https://oauth2.googleapis.com/token",
+					auth_provider_x509_cert_url: "https://www.googleapis.com/oauth2/v1/certs",
+					client_x509_cert_url:
+						"https://www.googleapis.com/robot/v1/metadata/x509/test%40test.iam.gserviceaccount.com",
+				}),
+			})
+
+			// Verify that AnthropicVertex was called with baseURL
+			expect(AnthropicVertex).toHaveBeenCalledWith(
+				expect.objectContaining({
+					baseURL: customBaseUrl,
+					projectId: "test-project",
+					region: "us-central1",
+				}),
+			)
+		})
+
+		it("should use custom base URL when provided with key file", () => {
+			const customBaseUrl = "https://custom-vertex-endpoint.example.com"
+
+			const handler = new AnthropicVertexHandler({
+				apiModelId: "claude-3-5-sonnet-v2@20241022",
+				vertexProjectId: "test-project",
+				vertexRegion: "us-central1",
+				vertexBaseUrl: customBaseUrl,
+				vertexKeyFile: "/path/to/keyfile.json",
+			})
+
+			// Verify that AnthropicVertex was called with baseURL
+			expect(AnthropicVertex).toHaveBeenCalledWith(
+				expect.objectContaining({
+					baseURL: customBaseUrl,
+					projectId: "test-project",
+					region: "us-central1",
+				}),
+			)
+		})
+
+		it("should use custom base URL when provided without credentials", () => {
+			const customBaseUrl = "https://custom-vertex-endpoint.example.com"
+
+			const handler = new AnthropicVertexHandler({
+				apiModelId: "claude-3-5-sonnet-v2@20241022",
+				vertexProjectId: "test-project",
+				vertexRegion: "us-central1",
+				vertexBaseUrl: customBaseUrl,
+			})
+
+			// Verify that AnthropicVertex was called with baseURL
+			expect(AnthropicVertex).toHaveBeenCalledWith(
+				expect.objectContaining({
+					baseURL: customBaseUrl,
+					projectId: "test-project",
+					region: "us-central1",
+				}),
+			)
+		})
+
+		it("should not include baseURL when no custom URL is provided", () => {
+			const handler = new AnthropicVertexHandler({
+				apiModelId: "claude-3-5-sonnet-v2@20241022",
+				vertexProjectId: "test-project",
+				vertexRegion: "us-central1",
+			})
+
+			// Verify that AnthropicVertex was called without baseURL
+			expect(AnthropicVertex).toHaveBeenCalledWith(
+				expect.not.objectContaining({
+					baseURL: expect.anything(),
+				}),
+			)
+		})
+	})
 })

src/api/providers/__tests__/vertex.spec.ts

@@ -138,4 +138,59 @@ describe("VertexHandler", () => {
 			expect(modelInfo.info.contextWindow).toBe(1048576)
 		})
 	})
+
+	describe("custom base URL", () => {
+		it("should use custom base URL when provided", async () => {
+			const customBaseUrl = "https://custom-vertex-endpoint.example.com"
+
+			handler = new VertexHandler({
+				apiModelId: "gemini-1.5-pro-001",
+				vertexProjectId: "test-project",
+				vertexRegion: "us-central1",
+				vertexBaseUrl: customBaseUrl,
+			})
+
+			// Mock the generateContent method
+			const mockGenerateContent = vitest.fn().mockResolvedValue({
+				text: "Test response with custom URL",
+			})
+			handler["client"].models.generateContent = mockGenerateContent
+
+			await handler.completePrompt("Test prompt")
+
+			// Verify that the custom base URL was passed in the config
+			expect(mockGenerateContent).toHaveBeenCalledWith(
+				expect.objectContaining({
+					config: expect.objectContaining({
+						httpOptions: { baseUrl: customBaseUrl },
+					}),
+				}),
+			)
+		})
+
+		it("should not include httpOptions when no custom base URL is provided", async () => {
+			handler = new VertexHandler({
+				apiModelId: "gemini-1.5-pro-001",
+				vertexProjectId: "test-project",
+				vertexRegion: "us-central1",
+			})
+
+			// Mock the generateContent method
+			const mockGenerateContent = vitest.fn().mockResolvedValue({
+				text: "Test response without custom URL",
+			})
+			handler["client"].models.generateContent = mockGenerateContent
+
+			await handler.completePrompt("Test prompt")
+
+			// Verify that httpOptions is undefined when no custom URL
+			expect(mockGenerateContent).toHaveBeenCalledWith(
+				expect.objectContaining({
+					config: expect.objectContaining({
+						httpOptions: undefined,
+					}),
+				}),
+			)
+		})
+	})
 })

src/api/providers/anthropic-vertex.ts

@@ -34,10 +34,19 @@ export class AnthropicVertexHandler extends BaseProvider implements SingleComple
 		const projectId = this.options.vertexProjectId ?? "not-provided"
 		const region = this.options.vertexRegion ?? "us-east5"
 
+		const baseOptions: any = {
+			projectId,
+			region,
+		}
+
+		// Add custom base URL if provided
+		if (this.options.vertexBaseUrl) {
+			baseOptions.baseURL = this.options.vertexBaseUrl
+		}
+
 		if (this.options.vertexJsonCredentials) {
 			this.client = new AnthropicVertex({
-				projectId,
-				region,
+				...baseOptions,
 				googleAuth: new GoogleAuth({
 					scopes: ["https://www.googleapis.com/auth/cloud-platform"],
 					credentials: safeJsonParse<JWTInput>(this.options.vertexJsonCredentials, undefined),
@@ -45,15 +54,14 @@ export class AnthropicVertexHandler extends BaseProvider implements SingleComple
 			})
 		} else if (this.options.vertexKeyFile) {
 			this.client = new AnthropicVertex({
-				projectId,
-				region,
+				...baseOptions,
 				googleAuth: new GoogleAuth({
 					scopes: ["https://www.googleapis.com/auth/cloud-platform"],
 					keyFile: this.options.vertexKeyFile,
 				}),
 			})
 		} else {
-			this.client = new AnthropicVertex({ projectId, region })
+			this.client = new AnthropicVertex(baseOptions)
 		}
 	}
 

src/api/providers/gemini.ts

@@ -78,9 +78,13 @@ export class GeminiHandler extends BaseProvider implements SingleCompletionHandl
 			tools.push({ googleSearch: {} })
 		}
 
+		// Use vertexBaseUrl if this is a Vertex handler, otherwise use googleGeminiBaseUrl
+		const baseUrl =
+			this.constructor.name === "VertexHandler" ? this.options.vertexBaseUrl : this.options.googleGeminiBaseUrl
+
 		const config: GenerateContentConfig = {
 			systemInstruction,
-			httpOptions: this.options.googleGeminiBaseUrl ? { baseUrl: this.options.googleGeminiBaseUrl } : undefined,
+			httpOptions: baseUrl ? { baseUrl } : undefined,
 			thinkingConfig,
 			maxOutputTokens: this.options.modelMaxTokens ?? maxTokens ?? undefined,
 			temperature: this.options.modelTemperature ?? 0,
@@ -220,10 +224,14 @@ export class GeminiHandler extends BaseProvider implements SingleCompletionHandl
 			if (this.options.enableGrounding) {
 				tools.push({ googleSearch: {} })
 			}
+			// Use vertexBaseUrl if this is a Vertex handler, otherwise use googleGeminiBaseUrl
+			const baseUrl =
+				this.constructor.name === "VertexHandler"
+					? this.options.vertexBaseUrl
+					: this.options.googleGeminiBaseUrl
+
 			const promptConfig: GenerateContentConfig = {
-				httpOptions: this.options.googleGeminiBaseUrl
-					? { baseUrl: this.options.googleGeminiBaseUrl }
-					: undefined,
+				httpOptions: baseUrl ? { baseUrl } : undefined,
 				temperature: this.options.modelTemperature ?? 0,
 				...(tools.length > 0 ? { tools } : {}),
 			}

webview-ui/src/components/settings/providers/Vertex.tsx

@@ -1,4 +1,4 @@
-import { useCallback } from "react"
+import { useCallback, useState } from "react"
 import { Checkbox } from "vscrui"
 import { VSCodeLink, VSCodeTextField } from "@vscode/webview-ui-toolkit/react"
 
@@ -18,6 +18,8 @@ type VertexProps = {
 export const Vertex = ({ apiConfiguration, setApiConfigurationField, fromWelcomeView }: VertexProps) => {
 	const { t } = useAppTranslation()
 
+	const [vertexBaseUrlSelected, setVertexBaseUrlSelected] = useState(!!apiConfiguration?.vertexBaseUrl)
+
 	const handleInputChange = useCallback(
 		<K extends keyof ProviderSettings, E>(
 			field: K,
@@ -94,6 +96,28 @@ export const Vertex = ({ apiConfiguration, setApiConfigurationField, fromWelcome
 				</Select>
 			</div>
 
+			<div className="mt-4">
+				<Checkbox
+					checked={vertexBaseUrlSelected}
+					onChange={(checked: boolean) => {
+						setVertexBaseUrlSelected(checked)
+						if (!checked) {
+							setApiConfigurationField("vertexBaseUrl", "")
+						}
+					}}>
+					{t("settings:providers.useCustomBaseUrl")}
+				</Checkbox>
+				{vertexBaseUrlSelected && (
+					<VSCodeTextField
+						value={apiConfiguration?.vertexBaseUrl || ""}
+						type="url"
+						onInput={handleInputChange("vertexBaseUrl")}
+						placeholder="https://us-central1-aiplatform.googleapis.com"
+						className="w-full mt-1"
+					/>
+				)}
+			</div>
+
 			{!fromWelcomeView && apiConfiguration.apiModelId?.startsWith("gemini") && (
 				<div className="mt-6">
 					<Checkbox