Fallow: codebase intelligence for JavaScript and TypeScript Codebase intelligence for JavaScript and TypeScript. The free static layer finds unused code, circular dependencies, code duplication, complexity hotspots, architecture boundary violations, and feature flag patterns. The optional paid runtime layer (Fallow Runtime) merges production execution data into the same fallow health report for hot-path review, cold-path deletion confidence, and stale-flag evidence. 90 framework plugins, zero configuration, sub-second static analysis. When to Use Finding dead code (unused files, exports, types, enum/class members) Finding unused or unlisted dependencies Detecting code duplication and clones Checking code health and complexity hotspots Cleaning up a codebase before a release or refactor Auditing a project for structural issues Setting up CI checks for dead code or duplication thresholds Auto-fixing unused exports and dependencies Detecting feature flag patterns (environment gates, SDK calls, config objects) Investigating why a specific export or file appears unused When NOT to Use Runtime error analysis or debugging Type checking (use tsc for that) Linting style or formatting issues (use ESLint, Biome, Prettier) Security vulnerability scanning Bundle size analysis Projects that are not JavaScript or TypeScript Prerequisites Fallow must be installed. If not available, install it: npm install -g fallow

prebuilt binaries (fastest)

or

npx fallow dead-code

run without installing

or

cargo install fallow-cli

build from source

Agent Rules

Always use

--format json --quiet 2>/dev/null

for machine-readable output. The

2>/dev/null

discards stderr so progress messages and threshold warnings don't corrupt the JSON on stdout. Never use

2>&1

Always append

|| true

to every fallow command. Exit code 1 means "issues found" (normal), not a runtime error. Without

|| true

, the Bash tool treats exit 1 as failure and cancels parallel commands. Only exit code 2 is a real error (invalid config, parse failure)

Use

--explain

to include a

_meta

object in JSON output with metric definitions, ranges, and interpretation hints

Use issue type filters

(

--unused-exports

,

--unused-files

, etc.) to limit output scope

Always

--dry-run

before

fix

, then

fix --yes

to apply

All output paths are relative

to the project root

Never run

fallow watch

. It is interactive and never exits

Commands

Command

Purpose

Key Flags

fallow

Run all analyses: dead code + duplication + complexity (default)

--only

,

--skip

,

--production

,

--production-dead-code

,

--production-health

,

--production-dupes

,

--ci

,

--fail-on-issues

,

--group-by

,

--summary

,

--fail-on-regression

,

--tolerance

,

--regression-baseline

,

--save-regression-baseline

,

--score

,

--trend

,

--save-snapshot

dead-code

Dead code analysis (

check

is an alias)

--unused-exports

,

--changed-since

,

--changed-workspaces

,

--production

,

--file

,

--include-entry-exports

,

--stale-suppressions

,

--ci

,

--group-by

,

--summary

,

--fail-on-regression

,

--tolerance

,

--regression-baseline

,

--save-regression-baseline

dupes

Code duplication detection

--mode

,

--threshold

,

--top

,

--changed-since

,

--workspace

,

--changed-workspaces

,

--skip-local

,

--cross-language

,

--ignore-imports

,

--fail-on-regression

,

--tolerance

,

--regression-baseline

,

--save-regression-baseline

fix

Auto-remove unused exports/deps

--dry-run

,

--yes

(required in non-TTY)

init

Generate config file or pre-commit hook

--toml

,

--hooks

,

--branch

migrate

Convert knip/jscpd config

--dry-run

,

--from PATH

list

Inspect project structure

--files

,

--entry-points

,

--plugins

,

--boundaries

health

Function complexity analysis (also covers Angular templates as synthetic