Google Gen AI SDK for Go 1.71.0

Apply the Go 1.27 baseline first. These rules cover google.golang.org/genai v1.71.0 with the Gemini Developer API and Vertex AI / Gemini Enterprise Agent Platform. The module's Go 1.24 minimum is a compilation requirement; use a supported, patched Go 1.27 toolchain. SDK types do not guarantee that every backend, API version, or model supports a feature.

Backend selection and credential resolution

• Set ClientConfig.Backend explicitly. With an unspecified backend, GOOGLE_GENAI_USE_ENTERPRISE takes precedence over GOOGLE_GENAI_USE_VERTEXAI, even when its value selects Gemini instead of Vertex; BackendEnterprise is normalized to BackendVertexAI.
• Supply the Gemini API key through trusted server configuration and keep long-lived keys out of browser and mobile clients. If environment fallback is used, set only the intended variable: GOOGLE_API_KEY wins over GEMINI_API_KEY, with a warning when both are present.
• Never set explicit Credentials and APIKey together; the constructor rejects them and includes the configuration in the error. Choose a reviewed Vertex authentication profile instead of mixing explicit and environment-derived settings whose precedence can clear the key or project/location. Explicit API key plus explicit project/location is supported in this tag.
• Use a workload identity with only the required project permissions for Vertex. Automatic credential detection uses the cloud-platform OAuth scope; that scope does not replace IAM restrictions on the identity.
• When supplying ClientConfig.HTTPClient for Vertex, provide its