Module instability 

instability analysis — Robert C. Martin’s package-coupling metrics per file (Martin 1994, “OO Design Quality Metrics: An Analysis of Dependencies”; canonised in Clean Architecture 2017).

• Afferent coupling ca — how many files import this one (the in-degree of the resolved import graph). High ca = widely depended upon.
• Efferent coupling ce — how many files this one imports (the out-degree). High ce = depends on a lot.
• Instability I = ce / (ca + ce) ∈ [0, 1]. I = 0 is maximally stable (much depends on it, it depends on nothing — hard and risky to change); I = 1 is maximally unstable (it depends on much, nothing depends on it — cheap to change).

The Stable-Dependencies Principle says a file should only depend on files more stable than itself; a widely-depended-on file (low I, high ca) that is nonetheless unstable is the dangerous shape.

Abstractness A and Distance-from-the-Main-Sequence D (the “Zone of Pain”) need symbol-level abstract-type counts the file-level import graph doesn’t carry, so they are out of scope here.

Computed on the resolved import graph, so accuracy follows the resolver’s language coverage (Rust + Python + JS/TS).

Structs

InstabilityRow

One file’s Martin coupling metrics.

Functions

run_instability

Run the instability analysis. Returns one row per file in the import graph, ranked by afferent coupling (most depended-upon first), where instability is most consequential.