3.1.0 - 2026-04-20

Release Notes

Added

• C++ language support (.cpp, .cc, .cxx, .hpp, .hxx)
• Sui Move language support (.move)
• New mutation operators:
  • NR (Negation Removal) across languages
  • RDV (Return Default Value) for Solidity and C++
  • RCI (Require Condition Inversion) for Solidity
  • DAS, MR, and VR for C++

Changed

• Reworked mutation conformance tests into a shared, cross-language test harness
• Build and CI hardening updates (including pinned actions and improved release/test workflows)

Fixed

• Improved child-process termination handling in the test runner
• Fixed skipped arithmetic-operator-shuffle (AOS) mutations
• Expanded and corrected Go ER/CR mutation coverage

Install mewt 3.1.0

Install prebuilt binaries via shell script

curl --proto '=https' --tlsv1.2 -LsSf https://github.com/trailofbits/mewt/releases/download/v3.1.0/mewt-installer.sh | sh

Download mewt 3.1.0

File	Platform	Checksum
mewt-aarch64-apple-darwin.tar.xz	Apple Silicon macOS	checksum
mewt-x86_64-unknown-linux-gnu.tar.xz	x64 Linux	checksum

3.0.1 - 2026-03-24

Release Notes

Fixed

• Grammar cache directory now rooted in OUT_DIR instead of a relative target/ path, fixing panics during Nix sandbox builds

Install mewt 3.0.1

Install prebuilt binaries via shell script

curl --proto '=https' --tlsv1.2 -LsSf https://github.com/trailofbits/mewt/releases/download/v3.0.1/mewt-installer.sh | sh

Download mewt 3.0.1

File	Platform	Checksum
mewt-aarch64-apple-darwin.tar.xz	Apple Silicon macOS	checksum
mewt-x86_64-pc-windows-msvc.zip	x64 Windows	checksum
mewt-x86_64-unknown-linux-gnu.tar.xz	x64 Linux	checksum

3.0.0 - 2026-03-24

Release Notes

Added

• --severity filter for print mutants and results commands (comma-separated: high, medium, low)
• --mutation_type now accepts comma-separated values for multi-type filtering
• Glob pattern support for all target path arguments (e.g., **/*.rs, src/**/*.go)
• mewt purge --all flag to purge every target in the database regardless of config rules
• mewt mutate --verbose flag to restore detailed per-mutant output during mutation generation
• mewt print targets now shows a rich table with columns: in_db, on_disk, included, hash, path, mutants

Changed

• BREAKING: Global --cwd flag replaced with --config
  • Pass a path to the config file; the directory containing it becomes the working directory
  • Relative paths in the config are resolved from the config file's location
• BREAKING: mewt purge default behavior changed
  • Without --target, now purges targets absent from [targets].include or present in [targets].ignore (previously purged all targets)
  • Use mewt purge --all to purge every target unconditionally
• BREAKING: mewt mutate is quiet by default, showing per-target summaries instead of per-mutant lines
  • Use --verbose to restore the previous detailed output
• BREAKING: LanguageEngine trait simplified
  • tree_sitter_language() -> TsLanguage removed
  • apply_all_mutations(&self, target: &Target) -> Vec<Mutant> renamed to mutate
  • get_all_slugs() and get_severity_by_slug() default methods removed (derive from get_mutations() directly)
• Target CLI argument for run and mutate is now optional; falls back to [targets].include from config
• Targets are sorted consistently across all commands (run, mutate, print, results, status)

Fixed

• Improved grammar caches for faster repeated runs
• Improved monorepo support for vendored tree-sitter grammars
• Security dependency updates: rsa (0.9.8 → 0.9.10), bytes (1.10.1 → 1.11.1)
• Dependency updates: tree-sitter (0.25.8 → 0.25.10), toml (0.8.23 → 0.9.6)

Install mewt 3.0.0

Install prebuilt binaries via shell script

curl --proto '=https' --tlsv1.2 -LsSf https://github.com/trailofbits/mewt/releases/download/v3.0.0/mewt-installer.sh | sh

Download mewt 3.0.0

File	Platform	Checksum
mewt-aarch64-apple-darwin.tar.xz	Apple Silicon macOS	checksum
mewt-x86_64-pc-windows-msvc.zip	x64 Windows	checksum
mewt-x86_64-unknown-linux-gnu.tar.xz	x64 Linux	checksum

2.0.1 - 2026-02-05

Release Notes

Changed

• Added support for Rust edition 2021 by replacing let-chains with nested if statements
• Configured clippy to allow collapsible_if for broader edition compatibility

Install mewt 2.0.1

Install prebuilt binaries via shell script

curl --proto '=https' --tlsv1.2 -LsSf https://github.com/trailofbits/mewt/releases/download/v2.0.1/mewt-installer.sh | sh

Download mewt 2.0.1

File	Platform	Checksum
mewt-aarch64-apple-darwin.tar.xz	Apple Silicon macOS	checksum
mewt-x86_64-pc-windows-msvc.zip	x64 Windows	checksum
mewt-x86_64-unknown-linux-gnu.tar.xz	x64 Linux	checksum

2.0.0 - 2026-02-05

Release Notes

Added

• mewt print config command to display the effective configuration
• Dedicated TypeScript and TSX grammars for improved parsing accuracy

Changed

• BREAKING: Configuration system overhauled with unified CLI/file symmetry
  • Configuration now uses dotted notation for CLI flags (e.g., --log.level, --test.cmd, --test.timeout)
  • Config file structure reorganized with nested sections ([log], [targets], [run], [test])
  • Added support for per-target test rules via [[test.per_target]] array in config file
  • CLI overrides now replace (not merge) config file values
• BREAKING: Removed environment variable configuration support
  • Previously supported variables (MEWT_LOG_LEVEL, MEWT_DB, MEWT_TEST_CMD, etc.) are no longer recognized
• BREAKING: Removed mewt print results command
  • Use mewt results instead (promoted in v1.1.0)
• Status filtering is now case-insensitive for --status flag
• Improved filter implementation consistency across print mutants and results commands

Fixed

• Percentage complete display in status command campaign summary
• Internal namespacing improvements in core module

Install mewt 2.0.0

Install prebuilt binaries via shell script

curl --proto '=https' --tlsv1.2 -LsSf https://github.com/trailofbits/mewt/releases/download/v2.0.0/mewt-installer.sh | sh

Download mewt 2.0.0

File	Platform	Checksum
mewt-aarch64-apple-darwin.tar.xz	Apple Silicon macOS	checksum
mewt-x86_64-pc-windows-msvc.zip	x64 Windows	checksum
mewt-x86_64-unknown-linux-gnu.tar.xz	x64 Linux	checksum

1.1.0 - 2026-01-28

Release Notes

Added

• Go language support for mutation testing
• JavaScript and TypeScript language support (including JSX files)
• mewt status command for campaign overview with per-file breakdown and aggregates
  • --format option: "table" (default) or "json"
• mewt results command (promoted from print results subcommand)
  • Enhanced filtering with --status, --language, --mutation_type, --line, --file options
  • SARIF output format support (--format sarif)
  • JSON and "ids" output formats
• mewt test --ids-file option to read mutant IDs from file or stdin (use - for stdin)
• JSON output format support for multiple commands:
  • mewt print mutations --format json
  • mewt print targets --format json
  • mewt print mutants --format json
• Enhanced filtering for print results, print mutants, and results commands:
  • --status: Filter by outcome status (Uncaught, TestFail, Skipped, Timeout)
  • --language: Filter by programming language
  • --mutation_type: Filter by mutation slug (e.g., ER, CR, BR)
  • --line: Filter by line number
  • --file: Filter by file path (substring match)
• mewt print mutants filtering options:
  • --tested: Show only mutants with test outcomes
  • --untested: Show only mutants without test outcomes
  • --format ids: Output just mutant IDs, one per line

Changed

• mewt test --ids is now optional when using --ids-file
• Cleaner log output (removed info level prefix)

Removed

• BuildFail outcome status (simplified outcome types)

Install mewt 1.1.0

Install prebuilt binaries via shell script

curl --proto '=https' --tlsv1.2 -LsSf https://github.com/trailofbits/mewt/releases/download/v1.1.0/mewt-installer.sh | sh

Download mewt 1.1.0

File	Platform	Checksum
mewt-aarch64-apple-darwin.tar.xz	Apple Silicon macOS	checksum
mewt-x86_64-pc-windows-msvc.zip	x64 Windows	checksum
mewt-x86_64-unknown-linux-gnu.tar.xz	x64 Linux	checksum

v1.0.0

Install mewt 1.0.0

Install prebuilt binaries via shell script

curl --proto '=https' --tlsv1.2 -LsSf https://github.com/trailofbits/mewt/releases/download/v1.0.0/mewt-installer.sh | sh

Download mewt 1.0.0

File	Platform	Checksum
mewt-aarch64-apple-darwin.tar.xz	Apple Silicon macOS	checksum
mewt-x86_64-pc-windows-msvc.zip	x64 Windows	checksum
mewt-x86_64-unknown-linux-gnu.tar.xz	x64 Linux	checksum