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Library source only: lib/, src/, workers/, bin/ and top-level source files. Tests, examples, tooling, type declarations and generated or minified files are left out.

Source lines are lines carrying code, with blank lines and comments dropped.

Cyclomatic complexity (CC) counts the independent paths through a function: 1 plus every if, loop, case, catch, ternary, && / || / ??, optional chain and default parameter. Above 10 a function is commonly considered hard to test, above 20 hard to understand.

Maintainability index (MI) is computed per function as max(0, (171 - 5.2 ln(Halstead volume) - 0.23 CC - 16.2 ln(lines)) * 100 / 171), the 0 to 100 scale Visual Studio uses, where below 20 is poor. The repository figure weights each function by its lines. Code outside any function (lookup tables, schemas, declarations) counts toward size only. MI is driven mostly by size, so read it as a trend, not a grade.

A move from JavaScript to TypeScript adds type annotations to every function, which raises the Halstead volume and lowers MI without the logic changing. Expect a step at that release.