C4AE: A Multi-Agent Engine for Automated C4 Modeling using Google ADK and Parallel Orchestration

The documentation of software architecture 
remains a persistent challenge in modern software engineering, 
characterized by the necessity for clear structural communication 
and the high operational cost of manual diagram maintenance. 
The C4 model decomposes systems into hierarchical layers of 
Context, Container, Component, and Code, emerging as a de facto 
standard for visualizing architectural abstractions. However, 
manual production of these artifacts is labor-intensive, error
prone, and suffers from "documentation drift." This paper 
presents C4AE (C4ArchitectEngine), a novel multi-agent system 
designed to automate C4 model artifact generation and dynamic 
sequence diagrams. Built upon the Google Agent Development Kit 
(ADK) and a Gemini LLM, C4AE introduces a Parallel 
Orchestration pattern that decouples architectural reasoning into 
specialized worker agents. These agents execute concurrently 
within a Parallel Agent construct to maximize throughput and 
minimize latency, followed by a sequential Merger Agent that 
synthesizes outputs into semantically coherent architectural 
definitions. This work details the system's architectural design, 
ADK framework utilization for state management and agent 
routing, Mermaid.js implementation as a standardized 
interchange format, and a hybrid evaluation framework for 
assessing structural and semantic integrity of LLM-generated 
software models.