fix(core): honor GOOGLE_GEMINI_BASE_URL and GOOGLE_VERTEX_BASE_URL

[chrisjcthomas]

Fixes #15430

Summary

This change wires custom base URL overrides through the core content generator so they are passed to @google/genai via httpOptions.baseUrl.

What Changed

• Added baseUrl to ContentGeneratorConfig
• Resolved GOOGLE_GEMINI_BASE_URL for AuthType.USE_GEMINI
• Resolved GOOGLE_VERTEX_BASE_URL for AuthType.USE_VERTEX_AI
• Passed baseUrl into GoogleGenAI through httpOptions
• Added validation so custom base URLs must be HTTPS unless they point to localhost
• Added unit tests covering Gemini and Vertex overrides, localhost HTTP overrides, invalid URLs, and insecure non-local HTTP URLs

Why

The Gemini CLI uses @google/genai, which supports a custom base URL via httpOptions.baseUrl. Before this change, the CLI propagated the environment variables but did not apply them when instantiating the SDK client.

Validation

• npm test -- src/core/contentGenerator.test.ts
• npm run typecheck

Notes

• I attempted the repo pre-commit hook as part of commit flow, but it currently fails due to an existing ESLint/plugin crash in import/no-internal-modules rather than this patch.
• The patch keeps localhost HTTP support for local proxies while requiring HTTPS for remote overrides.

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[chrisjcthomas]

cc @scidomino since this touches the packages/core/src/core/contentGenerator* path and the Gemini/Vertex base URL override flow.

[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request enables custom base URL configuration for the Gemini and Vertex AI clients by propagating environment variables into the SDK's httpOptions. It ensures that these overrides are securely validated, enforcing HTTPS for remote connections while maintaining flexibility for local development environments.

Highlights

• Base URL Configuration: Implemented support for GOOGLE_GEMINI_BASE_URL and GOOGLE_VERTEX_BASE_URL environment variables to allow custom API endpoint overrides.
• Security Validation: Added strict validation for custom base URLs, requiring HTTPS for remote endpoints while permitting HTTP for localhost.
• Testing: Added comprehensive unit tests to verify environment variable resolution, explicit override precedence, and security validation logic.

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[gemini-code-assist]

Code Review

This pull request introduces support for overriding the base URL of the Gemini and Vertex AI services using environment variables (GOOGLE_GEMINI_BASE_URL and GOOGLE_VERTEX_BASE_URL). It includes a validation utility to enforce HTTPS for remote URLs and comprehensive unit tests. One review comment suggests improving the logic for selecting the environment variable by checking the authType instead of the vertexai flag, which ensures the correct URL is used even when credentials are provided by a proxy.

[gemini-code-assist]

The logic for selecting the environment variable for the base URL should rely on the requested authType rather than the vertexai boolean. The vertexai property is only set to true if valid credentials (API key or Project/Location) are detected during configuration. However, a user providing a custom base URL via environment variables might be using a proxy that handles authentication or injects credentials, and thus might not have local credentials set. In such cases, config.vertexai would be undefined, causing the code to incorrectly fall back to GOOGLE_GEMINI_BASE_URL even when AuthType.USE_VERTEX_AI was explicitly requested or detected.

Suggested change

	const envBaseUrl = config.vertexai
	? process.env['GOOGLE_VERTEX_BASE_URL']
	: process.env['GOOGLE_GEMINI_BASE_URL'];
	const envBaseUrl = config.authType === AuthType.USE_VERTEX_AI
	? process.env['GOOGLE_VERTEX_BASE_URL']
	: process.env['GOOGLE_GEMINI_BASE_URL'];

[scidomino]

Update docs/reference/configuration.md to document these env vars

[chrisjcthomas]

@scidomino Done! I've updated docs/reference/configuration.md to include documentation for GOOGLE_GEMINI_BASE_URL and GOOGLE_VERTEX_BASE_URL, including security requirements and usage examples.

[scidomino]

You have not updated the PR. Perhaps you forgot to push your changes?

[chrisjcthomas]

@scidomino Apologies for the confusion! I initially pushed to the wrong branch. The PR has been updated now with the documentation changes on fix/base-url-overrides.

[scidomino]

We have some flakey integration tests that are slowing down merges. Please don't update the PR while I work through this.