Support full Google GenAI client options (support Vertex AI as alternative to Gemini API key)

[mcndt]

why

1. In my organisation, we use Vertex AI for authenticated LLM calls using Google Cloud service accounts instead of the Gemini API keys.
2. I also need control over the Vertex AI location being used for data residency guarantees.

what changed

I updated the typing of ClientOptions to support the full Google GenAI client constructor options, just like the Anthropic and OpenAI client options are already passed verbatim.

Because the Google GenAI client options don't have a baseUrl key, I also added explicit typing for the client options used for the ai-sdk model provider.

test plan

As this is only a typing change, I foresaw no immediate need for unit tests. Authentication with VertexAI is already tested as part of the GenAI client package.

[changeset-bot]

🦋 Changeset detected

Latest commit: 108b73a

The changes in this PR will be included in the next version bump.

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[greptile-apps]

Greptile Overview

Summary

This PR updates the Google GenAI client to accept the full GoogleGenAIOptions type instead of a simplified ClientOptions interface, enabling Vertex AI authentication and region control.

Key Changes:

• Updated ClientOptions type in types/model.ts to include GoogleGenAIClientOptions as a union member
• Added intersection type with aisdk options (apiKey?, baseURL?) to support AI SDK language model providers
• Modified GoogleClient.ts to import GoogleGenAIOptions directly from @google/genai and pass the full options object to the client constructor
• Implementation now matches the pattern used by AnthropicClient and OpenAIClient, which pass their full client options verbatim

Potential Concern:
The intersection type on lines 48-57 of types/model.ts adds apiKey?: string and baseURL?: string to all client options. If GoogleGenAIOptions already defines these properties with different types, this could cause type conflicts. However, since the PR author states this is a typing-only change with no runtime impact, this suggests the properties are compatible.

Confidence Score: 4/5

• This PR is safe to merge with minimal risk - it's a type-only change that expands functionality without breaking existing code.
• Score reflects the low-risk nature of the change (type definitions only), proper documentation via changeset, and consistent pattern matching with other client implementations. One point deducted due to potential type intersection conflicts with the added apiKey? and baseURL? properties in the union type - while likely compatible, this wasn't explicitly verified in the PR.
• Pay attention to types/model.ts - verify that the intersection type with aisdk options doesn't conflict with existing GoogleGenAIOptions properties.

Important Files Changed

File Analysis

Filename	Score	Overview
types/model.ts	4/5	Updated ClientOptions type to include full GoogleGenAIClientOptions and added intersection with aisdk options (apiKey, baseURL). The intersection type may cause type conflicts if GoogleGenAIOptions already defines these properties.
lib/llm/GoogleClient.ts	5/5	Switched from local ClientOptions import to GoogleGenAIOptions directly from @google/genai. Changed constructor to pass full clientOptions to GoogleGenAI instead of just apiKey. Clean implementation that matches the pattern used by Anthropic and OpenAI clients.

Sequence Diagram

sequenceDiagram
    participant User
    participant Stagehand
    participant LLMProvider
    participant GoogleClient
    participant GoogleGenAI

    User->>Stagehand: Initialize with modelClientOptions
    Stagehand->>LLMProvider: getClient(modelName, clientOptions)
    LLMProvider->>GoogleClient: new GoogleClient({clientOptions})
    Note over GoogleClient: clientOptions now supports full GoogleGenAIOptions
    GoogleClient->>GoogleClient: Check for apiKey in clientOptions
    alt apiKey missing
        GoogleClient->>GoogleClient: loadApiKeyFromEnv()
    end
    GoogleClient->>GoogleGenAI: new GoogleGenAI(clientOptions)
    Note over GoogleGenAI: Full options passed (apiKey, location, project, etc.)
    GoogleGenAI-->>GoogleClient: client instance
    GoogleClient-->>LLMProvider: GoogleClient instance
    LLMProvider-->>Stagehand: LLMClient
    User->>Stagehand: createChatCompletion()
    Stagehand->>GoogleClient: createChatCompletion()
    GoogleClient->>GoogleGenAI: models.generateContent()
    GoogleGenAI-->>GoogleClient: response
    GoogleClient-->>Stagehand: LLMResponse
    Stagehand-->>User: result

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