Sum of coupling

Change coupling (temporal coupling) is the tendency of files to change together — a dependency signal that no static analysis can see, because it captures logical coupling through copy-paste, shared conventions, or protocol mirroring, not just imports. Sum of Coupling (SoC) collapses the pairwise idea to a single number per file: how much company a file keeps when it changes. Files with a high SoC sit at the architectural center of gravity — change them and something else usually has to move too.

What mehen emits

Key	Type	Description
`history.sum_of_coupling`	int	For each commit touching the file, the number of other files in that commit, summed over the file’s history.

Semantics

Commits touching more than 30 files don’t contribute (code-maat’s changeset-noise threshold): bulk reformats and license-header sweeps would otherwise dominate every file’s score.
Merge commits don’t contribute (their changesets replay the merged commits).
Renames keep accumulating onto the surviving file’s identity.

mehen ships the per-file SoC aggregate rather than pairwise coupling percentages — SoC fits the per-file metric model, and the research recommends it as the pragmatic first step before full pairwise analysis.

How to read it

Signal	Interpretation
Top-of-ranking SoC	The file is an architectural hub. Interface changes here are expensive; treat its design with corresponding care.
High SoC on a file that “shouldn’t” be central	Hidden logical coupling — often duplicated knowledge that wants a shared abstraction.
Low SoC everywhere	Changes are well-localized; module boundaries are doing their job.

References

code-maat soc / coupling analyses (repo).
Tornhill, A. (2015). Your Code as a Crime Scene. Pragmatic Bookshelf — temporal coupling chapters.
CodeScene change-coupling documentation.

Overview

Change

People

Composites & risk

Sum of coupling

What mehen emits

Semantics

How to read it

References

See also

​What mehen emits

​Semantics

​How to read it

​References

​See also

What mehen emits

Semantics

How to read it

References

See also