Add VertexAI, simplify provider creation.

docs/assets/api/schemas.json

@@ -2743,6 +2743,10 @@
               "const": "GEMINI",
               "type": "string"
             },
+            {
+              "const": "VERTEX_AI",
+              "type": "string"
+            },
             {
               "const": "OPENAI",
               "type": "string"
@@ -2769,6 +2773,10 @@
           "const": "GEMINI",
           "type": "string"
         },
+        {
+          "const": "VERTEX_AI",
+          "type": "string"
+        },
         {
           "const": "OPENAI",
           "type": "string"

docs/researchers/add-agent-participant.md

@@ -11,9 +11,9 @@ same way as a human would.
 
 ## Preparing an Experiment for Agent Participants
 
-You can add agent participants to any experiment, as long as you have a Google
-API key configured. (Right now, only Gemini models can be selected for agent
-participants.) No other experiment-level config is necessary. However, we
+You can add agent participants to any experiment, as long as you have an
+API key configured for your chosen provider (Gemini, Vertex AI, OpenAI,
+Claude, or Ollama). No other experiment-level config is necessary. However, we
 recommend setting up your experiments with an eye for how agent participants
 will see each stage.
 

docs/researchers/getting-started.md

@@ -68,7 +68,8 @@ Once you're logged in, you should be able to see a home page with
 both your experiments and any shared public experiments.
 
 > Tip: If you plan to set up LLM mediators, add relevant API keys
-(e.g., [Gemini API key](https://ai.google.dev/gemini-api/docs/api-key))
+(e.g., [Gemini API key](https://ai.google.dev/gemini-api/docs/api-key),
+Vertex AI, OpenAI, Claude, or Ollama)
 on the Settings page now. Your key must be present in order to effectively
 run LLM agents during experiments. We store it in a Firebase document
 that only you (and the backend function making the LLM calls

frontend/src/components/experiment_builder/agent_persona_editor.ts

@@ -175,6 +175,11 @@ export class AgentPersonaEditorComponent extends MobxLitElement {
             'Gemini',
             ApiKeyType.GEMINI_API_KEY,
           )}
+          ${this.renderApiTypeButton(
+            agentConfig,
+            'Vertex AI',
+            ApiKeyType.VERTEX_AI_API_KEY,
+          )}
           ${this.renderApiTypeButton(
             agentConfig,
             'OpenAI or compatible API',

frontend/src/components/experimenter/experimenter_data_editor.ts

@@ -71,6 +71,8 @@ export class ExperimenterDataEditor extends MobxLitElement {
       </div>
       ${this.renderGeminiKey()}
       <div class="divider"></div>
+      ${this.renderVertexAISettings()}
+      <div class="divider"></div>
       ${this.renderOpenAISettings()}
       <div class="divider"></div>
       ${this.renderClaudeSettings()}
@@ -158,6 +160,67 @@ export class ExperimenterDataEditor extends MobxLitElement {
     `;
   }
 
+  // ============ Vertex AI ============
+  private renderVertexAISettings() {
+    const updateVertexAISettings = (
+      e: InputEvent,
+      field: 'apiKey' | 'project' | 'location' | 'serviceAccountJson',
+    ) => {
+      const oldData = this.authService.experimenterData;
+      if (!oldData) return;
+
+      const value = (e.target as HTMLInputElement).value;
+      this.setApiKeyResult(ApiKeyType.VERTEX_AI_API_KEY, {
+        status: CheckApiKeyStatus.NONE,
+      });
+
+      const newData = updateExperimenterData(oldData, {
+        apiKeys: {
+          ...oldData.apiKeys,
+          vertexAIConfig: {
+            ...(oldData.apiKeys?.vertexAIConfig ?? {}),
+            [field]: value,
+          },
+        },
+      });
+
+      this.authService.writeExperimenterData(newData);
+    };
+
+    const data = this.authService.experimenterData;
+    const config = data?.apiKeys.vertexAIConfig;
+    return html`
+      <div class="section">
+        <h3>Vertex AI API settings</h3>
+        <p>
+          Use either an API key (express mode) or service account credentials.
+        </p>
+        <md-filled-text-field
+          label="API key (express mode)"
+          placeholder="Add Vertex AI API key"
+          .value=${config?.apiKey ?? ''}
+          @input=${(e: InputEvent) => updateVertexAISettings(e, 'apiKey')}
+        ></md-filled-text-field>
+        <p>Or use a service account:</p>
+        <md-filled-text-field
+          type="textarea"
+          label="Service account JSON"
+          placeholder="Paste the full JSON key file contents"
+          .value=${config?.serviceAccountJson ?? ''}
+          @input=${(e: InputEvent) =>
+            updateVertexAISettings(e, 'serviceAccountJson')}
+        ></md-filled-text-field>
+        <md-filled-text-field
+          label="Location (optional, defaults to us-central1)"
+          placeholder="us-central1"
+          .value=${config?.location ?? ''}
+          @input=${(e: InputEvent) => updateVertexAISettings(e, 'location')}
+        ></md-filled-text-field>
+        ${this.renderCheckApiKey(ApiKeyType.VERTEX_AI_API_KEY)}
+      </div>
+    `;
+  }
+
   // ============ Claude ============
 
   private renderClaudeSettings() {

functions/package.json

@@ -25,6 +25,7 @@
   "dependencies": {
     "@ai-sdk/anthropic": "^3.0.59",
     "@ai-sdk/google": "^3.0.46",
+    "@ai-sdk/google-vertex": "^4.0.73",
     "@ai-sdk/openai": "^3.0.44",
     "@deliberation-lab/utils": "file:../utils",
     "@sinclair/typebox": "^0.34.48",

functions/src/api/ai-sdk.api.test.ts

@@ -37,7 +37,6 @@ const {
   mapResultToModelResponse,
   extractContentFromMessages,
   mapErrorToModelResponse,
-  getCredentials,
   API_TYPE_TO_PROVIDER,
 } = _testing;
 
@@ -951,57 +950,6 @@ describe('mapErrorToModelResponse', () => {
   });
 });
 
-// ============================================================================
-// CREDENTIAL TESTS
-// ============================================================================
-
-describe('getCredentials', () => {
-  const apiKeyConfig: APIKeyConfig = {
-    geminiApiKey: 'gemini-key',
-    openAIApiKey: {apiKey: 'openai-key', baseUrl: 'https://custom.openai.com'},
-    claudeApiKey: {apiKey: 'claude-key', baseUrl: 'https://custom.claude.com'},
-    ollamaApiKey: {url: 'http://localhost:11434', apiKey: 'ollama-key'},
-  };
-
-  it('extracts Gemini credentials', () => {
-    const creds = getCredentials(apiKeyConfig, ApiKeyType.GEMINI_API_KEY);
-    expect(creds).toEqual({apiKey: 'gemini-key'});
-  });
-
-  it('extracts OpenAI credentials with baseURL', () => {
-    const creds = getCredentials(apiKeyConfig, ApiKeyType.OPENAI_API_KEY);
-    expect(creds).toEqual({
-      apiKey: 'openai-key',
-      baseURL: 'https://custom.openai.com',
-    });
-  });
-
-  it('extracts Claude credentials with baseURL', () => {
-    const creds = getCredentials(apiKeyConfig, ApiKeyType.CLAUDE_API_KEY);
-    expect(creds).toEqual({
-      apiKey: 'claude-key',
-      baseURL: 'https://custom.claude.com',
-    });
-  });
-
-  it('extracts Ollama credentials', () => {
-    const creds = getCredentials(apiKeyConfig, ApiKeyType.OLLAMA_CUSTOM_URL);
-    expect(creds).toEqual({
-      apiKey: 'ollama-key',
-      baseURL: 'http://localhost:11434',
-    });
-  });
-
-  it('handles missing optional baseUrl', () => {
-    // Create a partial config - getCredentials handles missing fields gracefully
-    const config = {
-      openAIApiKey: {apiKey: 'key', baseUrl: ''},
-    } as APIKeyConfig;
-    const creds = getCredentials(config, ApiKeyType.OPENAI_API_KEY);
-    expect(creds).toEqual({apiKey: 'key', baseURL: undefined});
-  });
-});
-
 describe('API_TYPE_TO_PROVIDER', () => {
   it('maps all ApiKeyType values', () => {
     expect(API_TYPE_TO_PROVIDER[ApiKeyType.GEMINI_API_KEY]).toBe('google');

functions/src/api/ai-sdk.api.ts

@@ -18,6 +18,7 @@ import type {AssistantContent, FilePart} from '@ai-sdk/provider-utils';
 import {createOpenAI} from '@ai-sdk/openai';
 import {createAnthropic} from '@ai-sdk/anthropic';
 import {createGoogleGenerativeAI} from '@ai-sdk/google';
+import {createVertex} from '@ai-sdk/google-vertex';
 import {createOllama} from 'ollama-ai-provider-v2';
 
 // Re-export ModelMessage for use throughout functions package
@@ -32,6 +33,7 @@ import {
   APIKeyConfig,
   AgentModelSettings,
   ApiKeyType,
+  VertexAIConfig,
   isAlwaysThinkingModel,
   schemaToObject,
 } from '@deliberation-lab/utils';
@@ -44,32 +46,68 @@ import {
  * Provider factory creates a language model instance from configuration.
  * Returns LanguageModel (which can be a string or a model object).
  */
-type ProviderFactory = (config: {
-  apiKey?: string;
-  baseURL?: string;
-}) => (modelId: string) => LanguageModel;
+type ProviderFactory = (
+  config: APIKeyConfig,
+) => (modelId: string) => LanguageModel;
 
 /**
  * Registry of available AI providers.
  * Adding a new provider requires:
  * 1. npm install @ai-sdk/[provider]
  * 2. Add one line to this registry
  */
+/**
+ * Creates a Vertex AI model factory.
+ * Supports express mode (API key) and service account auth.
+ */
+function getVertexModelFactory(
+  config?: VertexAIConfig,
+): (modelId: string) => LanguageModel {
+  if (config?.apiKey) {
+    const provider = createVertex({apiKey: config.apiKey});
+    return (modelId: string) => provider(modelId) as LanguageModel;
+  }
+  // Parse service account JSON to extract credentials
+  const serviceAccount = config?.serviceAccountJson
+    ? JSON.parse(config.serviceAccountJson)
+    : {};
+  const provider = createVertex({
+    project: config?.project || serviceAccount.project_id,
+    location: config?.location,
+    googleAuthOptions: {
+      credentials: {
+        client_email: serviceAccount.client_email,
+        private_key: serviceAccount.private_key,
+      },
+    },
+  });
+  return (modelId: string) => provider(modelId) as LanguageModel;
+}
+
 const PROVIDER_REGISTRY: Record<string, ProviderFactory> = {
-  google: ({apiKey}) => {
-    const provider = createGoogleGenerativeAI({apiKey});
+  google: (config) => {
+    const provider = createGoogleGenerativeAI({apiKey: config.geminiApiKey});
     return (modelId: string) => provider(modelId) as LanguageModel;
   },
-  openai: ({apiKey, baseURL}) => {
-    const provider = createOpenAI({apiKey, baseURL});
+  vertex: (config) => getVertexModelFactory(config.vertexAIConfig),
+  openai: (config) => {
+    const provider = createOpenAI({
+      apiKey: config.openAIApiKey?.apiKey,
+      baseURL: config.openAIApiKey?.baseUrl || undefined,
+    });
     return (modelId: string) => provider(modelId) as LanguageModel;
   },
-  anthropic: ({apiKey, baseURL}) => {
-    const provider = createAnthropic({apiKey, baseURL});
+  anthropic: (config) => {
+    const provider = createAnthropic({
+      apiKey: config.claudeApiKey?.apiKey,
+      baseURL: config.claudeApiKey?.baseUrl || undefined,
+    });
     return (modelId: string) => provider(modelId) as LanguageModel;
   },
-  ollama: ({baseURL}) => {
-    const provider = createOllama({baseURL});
+  ollama: (config) => {
+    const provider = createOllama({
+      baseURL: config.ollamaApiKey?.url,
+    });
     return (modelId: string) => provider(modelId) as LanguageModel;
   },
 };
@@ -79,41 +117,12 @@ const PROVIDER_REGISTRY: Record<string, ProviderFactory> = {
  */
 const API_TYPE_TO_PROVIDER: Record<ApiKeyType, string> = {
   [ApiKeyType.GEMINI_API_KEY]: 'google',
+  [ApiKeyType.VERTEX_AI_API_KEY]: 'vertex',
   [ApiKeyType.OPENAI_API_KEY]: 'openai',
   [ApiKeyType.CLAUDE_API_KEY]: 'anthropic',
   [ApiKeyType.OLLAMA_CUSTOM_URL]: 'ollama',
 };
 
-/**
- * Extracts credentials from APIKeyConfig based on API type.
- */
-function getCredentials(
-  apiKeyConfig: APIKeyConfig,
-  apiType: ApiKeyType,
-): {apiKey?: string; baseURL?: string} {
-  switch (apiType) {
-    case ApiKeyType.GEMINI_API_KEY:
-      return {apiKey: apiKeyConfig.geminiApiKey};
-    case ApiKeyType.OPENAI_API_KEY:
-      return {
-        apiKey: apiKeyConfig.openAIApiKey?.apiKey,
-        baseURL: apiKeyConfig.openAIApiKey?.baseUrl || undefined,
-      };
-    case ApiKeyType.CLAUDE_API_KEY:
-      return {
-        apiKey: apiKeyConfig.claudeApiKey?.apiKey,
-        baseURL: apiKeyConfig.claudeApiKey?.baseUrl || undefined,
-      };
-    case ApiKeyType.OLLAMA_CUSTOM_URL:
-      return {
-        apiKey: apiKeyConfig.ollamaApiKey?.apiKey || undefined,
-        baseURL: apiKeyConfig.ollamaApiKey?.url,
-      };
-    default:
-      return {};
-  }
-}
-
 /**
  * Gets a language model instance from the provider registry.
  */
@@ -135,8 +144,7 @@ function getModel(
     );
   }
 
-  const credentials = getCredentials(apiKeyConfig, modelSettings.apiType);
-  return providerFactory(credentials)(modelSettings.modelName);
+  return providerFactory(apiKeyConfig)(modelSettings.modelName);
 }
 
 // ============================================================================
@@ -355,7 +363,8 @@ function getProviderOptions(
   const overrides = generationConfig.providerOptions;
 
   switch (apiType) {
-    case ApiKeyType.GEMINI_API_KEY: {
+    case ApiKeyType.GEMINI_API_KEY:
+    case ApiKeyType.VERTEX_AI_API_KEY: {
       const mapped = buildGoogleOptions(generationConfig, modelName);
       const merged = {...mapped, ...overrides?.google};
       return {google: merged};
@@ -966,6 +975,5 @@ export const _testing = {
   mapResultToModelResponse,
   extractContentFromMessages,
   mapErrorToModelResponse,
-  getCredentials,
   API_TYPE_TO_PROVIDER,
 };