- Executable: `./jq -c ''`; compact JSON lines on stdout. - Exit codes: `0` success, `3` compile failure, `5` runtime failure; diagnostics on stderr. - Standard-library Python only; no external jq, dependencies, networking, or persistence. - Modules: CLI, lexer, parser/AST, evaluator streams, runtime values, builtins, paths/assignment, diagnostics. - Preserve generator ordering, multiplicity, backtracking, immutable transformations, and partial output.