fix(core): Keep the API version in the Gemini base URL for agent models (#37239)

Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>

packages/@n8n/agents/src/runtime/__tests__/model-factory.test.ts

@@ -64,6 +64,7 @@ vi.mock('@ai-sdk/google', () => ({
 		provider: 'google',
 		modelId: model,
 		apiKey: opts?.apiKey,
+		baseURL: opts?.baseURL,
 		fetch: opts?.fetch,
 		specificationVersion: 'v3',
 	}),
@@ -520,6 +521,41 @@ describe('createModel', () => {
 		});
 	});
 
+	describe('google baseURL normalization', () => {
+		const baseURLFor = (creds: Record<string, unknown>) =>
+			(
+				createModel({
+					id: 'google/gemini-3.7-flash',
+					apiKey: 'g-test',
+					...creds,
+				}) as unknown as Record<string, unknown>
+			).baseURL;
+
+		// `googlePalmApi.host` defaults to the bare host, which drops the API
+		// version from every request path — Google then 404s for any model.
+		it('appends the API version to the credential host', () => {
+			expect(baseURLFor({ url: 'https://generativelanguage.googleapis.com' })).toBe(
+				'https://generativelanguage.googleapis.com/v1beta',
+			);
+		});
+
+		it('leaves a baseURL that already targets the API version unchanged', () => {
+			expect(baseURLFor({ url: 'https://generativelanguage.googleapis.com/v1beta' })).toBe(
+				'https://generativelanguage.googleapis.com/v1beta',
+			);
+		});
+
+		it('appends to a proxy host', () => {
+			expect(baseURLFor({ url: 'https://proxy.example/gemini' })).toBe(
+				'https://proxy.example/gemini/v1beta',
+			);
+		});
+
+		it('leaves the SDK default in place when no host is configured', () => {
+			expect(baseURLFor({})).toBeUndefined();
+		});
+	});
+
 	describe('alibaba baseURL normalization', () => {
 		const baseURLFor = (creds: Record<string, unknown>) =>
 			(

packages/@n8n/agents/src/runtime/model/model-factory.ts

@@ -214,7 +214,15 @@ const LANGUAGE_PROVIDERS: ProviderRegistry = {
 	google: {
 		build: (creds, model, fetch) => {
 			const { createGoogle } = require('@ai-sdk/google') as typeof import('@ai-sdk/google');
-			return createGoogle({ ...creds, fetch })(model);
+			// The SDK expects a version-qualified base (its own default ends in
+			// `/v1beta`), but `googlePalmApi.host` stores the bare host — the Gemini
+			// node's SDK appends the API version itself. Passing the host through
+			// unqualified drops the version from every request path, and Google
+			// answers 404 for any model.
+			const normalizedBaseURL = creds.baseURL
+				? ensureUrlPathSuffix(creds.baseURL, '/v1beta')
+				: creds.baseURL;
+			return createGoogle({ ...creds, baseURL: normalizedBaseURL, fetch })(model);
 		},
 	},
 	xai: {