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fallow dead-code enforces architecture boundaries by checking that imports between directories follow your rules. Define and declare which zones may import from which. 
fallow dead-code --boundary-violations
Boundary violations are included in fallow dead-code output by default. Use --boundary-violations to show only boundary issues.

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Quick start with presets

The fastest way to add boundaries is with a built-in preset. Fallow ships four presets for common architecture patterns: 
{
  "boundaries": {
    "preset": "bulletproof"
  }
}
Run fallow list --boundaries to see the expanded zones and rules:
$ fallow list --boundaries
Boundaries: 4 zones, 4 rules

Zones:
  app                  3 files  src/app/**
  features             12 files src/features/**
  shared               8 files  src/components/**, src/hooks/**, src/lib/**, ...
  server               4 files  src/server/**

Rules:
  app                  → features, shared, server
  features             → shared, server
  server               → shared
  shared               (isolated — no imports allowed)

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Presets

The dominant React/Next.js pattern. Feature modules are isolated from each other; shared utilities and server infrastructure form the base layers.4 zones: app, features, shared, server
app       → features, shared, server
features  → shared, server
server    → shared
shared    (isolated)
The shared zone covers: components, hooks, lib, utils, utilities, providers, shared, types, styles, i18n.
This preset matches the architecture from Bulletproof React and is the most common pattern in modern React and Next.js projects.

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Source root detection

Preset zone patterns use {rootDir}/{zone}/**. Fallow auto-detects the source root from tsconfig.json:
tsconfig.json
{
  "compilerOptions": {
    "rootDir": "./lib"  // zones become lib/app/**, lib/features/**, etc.
  }
}
If no rootDir is found, fallow falls back to src.

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Custom zones and rules

For full control, define zones and rules directly: 
{
  "boundaries": {
    "zones": [
      { "name": "ui", "patterns": ["src/components/**", "src/pages/**"] },
      { "name": "data", "patterns": ["src/db/**", "src/api/**"] },
      { "name": "shared", "patterns": ["src/lib/**", "src/utils/**"] }
    ],
    "rules": [
      { "from": "ui", "allow": ["shared"] },
      { "from": "data", "allow": ["shared"] },
      { "from": "shared", "allow": [] }
    ]
  }
}

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How zones work

  • A file belongs to the first zone whose pattern matches (first-match wins)
  • Files that don’t match any zone are unrestricted: they can import from and be imported by any zone
  • Self-imports are always allowed (files in the same zone can freely import each other)
  • A zone with no rule entry is unrestricted: it can import from any zone
  • A zone with a rule and an empty allow list is isolated: it cannot import from other zones

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Overriding preset zones

Start from a preset and customize specific zones or rules. Zones with the same name replace the preset zone; rules with the same from replace the preset rule. 
{
  "boundaries": {
    "preset": "hexagonal",
    "zones": [
      { "name": "domain", "patterns": ["src/core/**"] }
    ]
  }
}
This keeps adapters and ports from the hexagonal preset but replaces the domain zone pattern with src/core/**.

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Suppressing violations

Suppress individual findings with inline comments: 
// fallow-ignore-next-line boundary-violation
import { db } from '../data/client';
Or suppress all boundary violations in a file: 
// fallow-ignore-file boundary-violation
To suppress boundary checking entirely, set the rule severity to off: 
{
  "rules": {
    "boundary-violation": "off"
  }
}
When introducing boundaries to an existing codebase, start with "warn" severity. Fix violations incrementally, then switch to "error" once the codebase is clean.

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Output formats

Boundary violations appear in all output formats:
$ fallow dead-code --boundary-violations
Boundary violations (2)

  src/features/auth/login.ts:3 → src/features/billing/api.ts (features → features)
  src/components/Button.tsx:1 → src/server/db/client.ts (shared → server)

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Inspecting your boundaries

Use fallow list --boundaries to verify your configuration before running analysis: 
# Human-readable summary
fallow list --boundaries

# JSON for scripting or MCP tools
fallow list --boundaries --format json --quiet
Fallow warns when a zone matches zero files. This usually means the glob pattern doesn’t match your directory structure. Run fallow list --boundaries to check file counts per zone.

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See also

fallow dead-code

CLI reference for the dead code command, including all issue type filters.

Rules & Severity

Set boundary violations to error, warn, or off.

Inline Suppression

Suppress individual findings in source code.