Module stability

What it means

Module stability considers dependency direction, interface volatility, and the cost of changing a module. A stable module often has many consumers and a carefully managed contract, while a volatile module may be under active development. Stability is contextual and should not be confused with inactivity.

Example

A tax policy module changes weekly while many services consume it. The team adds a versioned contract and isolates volatile rules from the stable calculation interface.

Limitations

A stable interface may preserve a poor design, and a volatile module may simply reflect legitimate product evolution. Include consumer behavior, compatibility tests, and ownership in the assessment.

How to use the signal

Document whether stability refers to interface compatibility, implementation churn, or consumer effort, because those properties can diverge.

Evaluate consumer impact and interface volatility together, because inactivity can look like stability while hiding neglect.

Weave can help relate stability concerns to breaking changes, review load, and rework. Use API history and dependency analysis for the underlying evidence.