Identifier

C4-ARCH-001

Severity

Error - High impact on architecture quality

Scope

General - This rule is evaluated against the overall architecture model.

Default expression

Explanation

Containers should form an acyclic dependency graph in which the direction of dependencies is unambiguous and consistent with architectural responsibilities. A cyclic dependency occurs when container A depends (directly or indirectly) on container B, and container B also depends on container A.

Container-level cyclic dependencies indicate a violation of separation of responsibility and a lack of clear architectural boundaries. They create strong coupling, preventing independent versioning, deployment, testing, and refactoring of containers. In extreme cases, cyclic dependencies can lead to problems with initialization, configuration, or dependency loading at system startup.

This rule enforces an architecture based on unidirectional dependencies, consistent with principles such as the Dependency Rule, the Stable Dependencies Principle, and the Clean Architecture.

Example of violation - direct cycle

Example of violation - indirect cycle

Recommendations

• Avoid direct dependencies between containers with equal responsibility.
• Use interfaces, contracts, or asynchronous mechanisms to break cycles.