Fallow Code Analysis

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---
name: fallow
description: Codebase intelligence for TypeScript and JavaScript. Static analysis of code and styles reports changed-code risk, cleanup opportunities, duplication, circular dependencies, complexity hotspots, architecture boundaries, design-system drift, feature flags, and opt-in security candidates. Runtime coverage can merge production execution data for hot-path review, cold-path deletion confidence, and stale-flag evidence. 123 framework plugins, zero configuration, sub-second static analysis. Use when asked to audit PR risk, find unused code or dependencies, detect duplicates, check styling consistency, inspect architecture boundaries, merge runtime coverage, auto-fix supported issues, or run fallow.
license: MIT
---

# Fallow: codebase intelligence for TypeScript and JavaScript

Codebase intelligence for TypeScript and JavaScript. The static layer analyzes code and styles and reports quality, changed-code risk, cleanup opportunities, circular dependencies, code duplication, complexity hotspots, architecture boundary violations, design-system styling drift, feature flag patterns, and opt-in security candidates. Runtime coverage merges production execution data into the same `fallow health` report for hot-path review, cold-path deletion confidence, and stale-flag evidence, with a single local capture available by default and continuous/cloud runtime monitoring available as an optional mode. 123 framework plugins, zero configuration, sub-second static analysis.

## When to Use
- Find cleanup opportunities: unused files, exports, types, members, dependencies, or stale flags.
- Detect code duplication, circular dependencies, architecture boundary issues, and complexity hotspots.
- Check styling consistency, CSS dead surface, and design-token drift.
- Audit changed code before a commit, PR, release, or refactor.
- Set up CI quality gates, duplication thresholds, and regression baselines.
- Auto-fix supported unused exports and dependencies after `--dry-run`.
- Investigate why a specific export, dependency, file, or issue type was reported.
- Surface local security candidates for an agent to verify (`fallow security`).
- Find untested but runtime-reachable code (`fallow health --coverage-gaps`).
- Rank complexity hotspots, owners, and refactoring targets (`fallow health --hotspots --ownership --targets`).
- Review what fallow has surfaced over time (`fallow impact`).
- Confirm exact TypeScript symbol use, affected tests, API leaks, or public type coupling when syntactic evidence is insufficient (`--type-aware`).

## When NOT to Use
- Runtime error analysis or debugging
- Type checking (use `tsc` for that). Type-aware fallow consumes checker evidence for project-wide analysis but does not report compiler diagnostics.
- Linting style or formatting issues (use ESLint, Biome, Prettier)
- Verified security vulnerability scanning or SAST. `fallow security` surfaces local, deterministic security *candidates* for a downstream agent to verify; it does not prove exploitability. Use Snyk, CodeQL, or Semgrep for verified scanning, and an SCA tool for dependency CVEs.
- Bundle size analysis
- Projects that are not JavaScript or TypeScript

## Prerequisites

Fallow must be installed. If not available, install it:

```bash
npm install -g fallow      # prebuilt binaries (fastest, recommended)
npx fallow dead-code       # run without installing
cargo install fallow-cli   # build from source
```

## Agent Rules

1. **Always use `--format json --quiet 2>/dev/null`** for machine-readable output and parse it as JSON. Compact JSON is the default; never depend on whitespace or add `--pretty` in agent pipelines. The `2>/dev/null` discards stderr so progress messages and threshold warnings don't corrupt the JSON on stdout. Never use `2>&1`
2. **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 c

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---
name: fallow-review
description: >-
  Review AI-generated or human-written code changes with fallow's
  graph-grounded review brief. Subtracts deterministic concerns (unused code,
  complexity, duplication, styling) from the loop, ranks what to look at by
  blast radius and risk, and surfaces the few consequential structural
  decisions (new public-API contracts, coupling/boundary crossings, new
  dependencies) as framed judgment questions anchored to verifiable signals.
  Drives a closed agent-contract loop: fetch the walkthrough guide, return a
  judgment, and have fallow post-validate it against the live graph
  (hallucinated or stale judgments are rejected). Use when asked to review a
  PR, review a branch, review a diff, do a code review, or check changed code
  before merge.
license: MIT
---

# Fallow Review: graph-grounded code review

`fallow review` turns a changeset into a deterministic, graph-derived review brief and an agent-contract loop. It answers "where do I look, and what calls actually need human taste?" rather than "will CI block this?" (that is `fallow audit`, which gates). `review` always exits 0, so it is safe to run regardless of verdict.

The four jobs it does, in order:

- **subtract**: dead code, complexity, duplication, and styling for the changed files are reported and kept OUT of the judgment loop, so attention is not spent on what a deterministic check already owns.
- **focus**: changed-file units are ranked by a composite attention score (fan-in/out, risk zone, change shape) with a `review-here` / `not-prioritized` label and a full `deprioritized` escape-hatch list, so nothing is hidden.
- **structure**: the decision surface lifts the handful of consequential STRUCTURAL decisions out of the diff and frames each as a judgment question, capped to a working-memory-sized set, each anchored to a `signal_id` fallow emitted.
- **direct**: the walkthrough guide hands an agent a graph-derived digest, the review direction, a graph-snapshot pin, and the exact judgment schema to return.

## When to use

- Reviewing a PR, branch, or diff (AI-generated or human-written) before merge.
- After an agent has done work and removed the fallow findings it could; this surfaces what is left for human/agent taste.
- Producing inline-reviewable judgments that can flow back to the agent that wrote the code.

## When NOT to use

- Gating CI on a pass/fail verdict: use `fallow audit` (it exits non-zero on a fail verdict).
- Whole-project health, cleanup, or dead-code reports: use the `fallow` skill.

## Quick human brief

```bash
# Auto-detect the base (merge-base against the upstream / remote default):
fallow review

# Pin the base, or scope to a precise diff:
fallow review --base origin/main
git diff --find-renames origin/main...HEAD | fallow review --base origin/main --diff-stdin
```

The human brief prints the orientation facts, the focus map, and the decision surface ("Decisions to make"). `--format json` emits the full structured envelope (`decisions`, `focus`, `deltas`, `impact_closure`, `partition`, `graph_facts`). `--max-decisions N` tunes the cap (clamped to a small band). `--show-deprioritized` expands what the focus map collapsed.

## The decision surface

Each decision is a framed question anchored to a `signal_id` fallow deterministically derived from the graph (a delta key or a coordination-gap key). There are exactly three shippable categories:

- **coupling-boundary**: a new cross-zone dependency edge.
- **public-api-contract**: a new exported public-API surface, or a changed contract consumed by modules OUTSIDE this diff (a coordinate-or-confirm signal).
- **dependency**: a new third-party dependency (new maintenance + supply-chain surface).

A decision may carry `previous_signal_id` when its anchor file was renamed in the change: that is the `signal_id` the same decision would have had at the old path, so a review surface can re-attach a prior reviewer comment across a `git mv`.

## Eliciting the broa

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