Fallow - Codebase Health

April 3, 2026

Version updated for https://github.com/fallow-rs/fallow to version v2.11.0.

This action is used across all versions by 1 repositories.

Action Type

This is a Composite action.

Go to the GitHub Marketplace to find the latest changes.

Action Summary

This GitHub Action, “Fallow,” is a Rust-based codebase analyzer designed for TypeScript and JavaScript projects. It automates the detection of dead code, code duplication, complexity issues, and architectural violations, providing quick and actionable insights to optimize and maintain code quality. Key capabilities include sub-second analysis, zero configuration, automated dead code removal, duplication detection, and health audits for efficient development workflows.

What’s Changed

Group dead code by team ownership or directory

The last Tier 1 feature is here: --group-by owner|directory partitions all analysis output into labeled groups for team-level triage, dashboards, and operational workflows.

`--group-by owner` — CODEOWNERS integration

Group issues by team using your existing .github/CODEOWNERS file:

fallow check --group-by owner

7 groups: @types-team 174 · @community 57 · @preact-core 29 · @compat-team 25 · ...

@types-team (174 issues: 8 files · 9 exports · 115 types · 40 unresolved imports) — matched by *.ts, *.tsx
● Unused files (8)
  compat/test/ts/forward-ref.tsx
  ...

@community (57 issues: 18 files · 27 exports · 12 unlisted deps)
● Unused files (18)
  ...

Auto-probes CODEOWNERS, .github/CODEOWNERS, .gitlab/CODEOWNERS, docs/CODEOWNERS
Last-match-wins pattern matching (gitignore-style globs)
First owner on multi-owner lines is the assigned owner
Rule annotations show which CODEOWNERS pattern matched (e.g., matched by *.tsx)
Summary line at top shows all groups sorted by issue count
Breakdown headers show per-type counts (3 files · 21 exports · 1 dep)
Doc URL dedup — each explanation link appears once across all groups

`--group-by directory` — no CODEOWNERS needed

Group by first path component for quick structural triage:

fallow check --group-by directory

Works on any project without setup. Great for monorepos where directory = package.

All 6 output formats

Format	Grouping style
Human	Colored group headers with summary + breakdown
JSON	`{ "grouped_by": "owner", "groups": [{key, total_issues, ...}] }`
Compact	Tab-prefixed lines: `@team\tunused-file:path`
Markdown	`## @team (N issues)` sections
SARIF	`properties.owner` on each result
CodeClimate	`owner` field on each issue

MCP + Config

MCP: group_by: "owner" | "directory" parameter on the analyze tool
Config: optional codeowners field in .fallowrc.json for custom CODEOWNERS path

Also in this release

GitHub Action review comments now filtered to PR diff hunks, preventing ARG_MAX crashes on large PRs (50+ files)
Improved review comment hunk filtering UX and robustness

Full Changelog: https://github.com/fallow-rs/fallow/compare/v2.10.1...v2.11.0