Runs on-demand, sandbox-isolated mutation testing against a single source file to identify gaps in unit test coverage. Chaos-MCP generates mutants (logical faults like changing > to >=) and checks whether the local test suite catches them. Surviving mutants indicate test coverage holes. Supports TypeScript/JavaScript (StrykerJS), Python (cosmic-ray), Rust (cargo-mutants), and PHP (Infection).

Batch triage: audit a set of files and/or directories and return a weakest-first ranked leaderboard of mutation scores, so you can see where the test suite is most fragile in one call. Directories are recursively expanded to supported source files (.ts/.js/.py/.rs/.php), skipping test files. Files are audited in parallel (see fileConcurrency, default min(4, cpus-1)), under a shared wall-clock budget (see totalTimeoutMs). Drill into a weak file with audit_code_resilience for per-mutant survivor detail.

Cheap pre-flight estimate of how big/long auditing a file will be, WITHOUT running the full mutation test cycle. Returns an approximate mutant count (for Rust, an exact count of the mutants cargo-mutants --list GENERATES — the audit scores fewer, excluding unviable ones as incompetent; a source heuristic for TS/JS/Python/PHP, labeled fidelity:"approx"). Set withTiming:true to also run the test suite once and estimate wall-clock time. Use this before audit_code_resilience to decide whether to audit now, scope down, or skip.