ADK Frontend & Client Integration Playbook

This reference guide serves as an operational AI Skill for downstream coding agents and developers building decoupled frontends (CLI, Textual TUI, Web Dashboards) that interact with custom Agent Development Kit (ADK) agents running on GCP Agent Runtime (Vertex AI Reasoning Engines).

🧭 Architectural Architecture: The Passthrough Gateway

When an ADK agent is deployed to Vertex AI, the platform exposes the FastAPI container behind a secure external gateway:

https://{location}-aiplatform.googleapis.com/reasoningEngines/v1/projects/{project}/locations/{location}/reasoningEngines/{engine_id}/api

💡 Golden Rule: Communicate via Pure HTTP, bypass ReasoningEngine SDK classes

Do NOT use GenAI or preview ReasoningEngine Python classes to invoke queries in the client. Interact directly with the REST endpoints (like /run or /run_sse) over standard HTTP/HTTPS.