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 serially. 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 (exact for Rust via cargo-mutants --list; 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.