Genkit for Go 1.12.0

Apply the Go 1.27 baseline first. These rules cover github.com/firebase/genkit/go v1.12.0, whose module requires Go 1.25 or later. Enable genkit.WithExperimental() only for deliberately adopted preview APIs; agent, session, and durable-streaming rules below apply when those features are used.

Configuration and prompt authority

• Construct genkit.Init, model references, schemas, tools, resources, and middleware from trusted server configuration. Review the final merged options: repeated ai.WithTools and ai.WithUse accumulate, while later model, config, system-prompt, and output-schema options replace earlier values. Do not expose raw generation options as a public request contract.
• Load .prompt files, partials, helpers, and genkit.WithPromptDir or WithPromptFS assets only from trusted deployment sources. Pass user values through ai.WithInput or typed content functions; never construct template source from user text. WithPrompt and WithSystem compile templates in prompt definitions, while content-function results and WithMessages text are used verbatim.
• Build message roles and privileged metadata on the server. Keep user text, retrieved documents, tool results, and imported conversations as untrusted content; reject client-supplied system messages, fabricated tool results, and approval metadata before accepting ai.Message objects or agent inputs.
• Control Prompt.Execute overrides explicitly. Execution-time WithDocs replaces the prompt's documents and suppresses WithDocsFn; do not let a caller substitute documents for an authorized