turborepo

Turborepo Skill

Build system for JavaScript/TypeScript monorepos. Turborepo caches task outputs and runs tasks in parallel based on dependency graph.

IMPORTANT: Package Tasks, Not Root Tasks

DO NOT create Root Tasks. ALWAYS create package tasks.

When creating tasks/scripts/pipelines, you MUST:

1. Add the script to each relevant package's package.json
2. Register the task in root turbo.json
3. Root package.json only delegates via turbo run <task>

DO NOT put task logic in root package.json. This defeats Turborepo's parallelization.

// DO THIS: Scripts in each package
// apps/web/package.json
{ "scripts": { "build": "next build", "lint": "eslint .", "test": "vitest" } }

// apps/api/package.json
{ "scripts": { "build": "tsc", "lint": "eslint .", "test": "vitest" } }

// packages/ui/package.json
{ "scripts": { "build": "tsc", "lint": "eslint .", "test": "vitest" } }

// turbo.json - register tasks
{
  "tasks": {
    "build": { "dependsOn": ["^build"], "outputs": ["dist/**"] },
    "lint": {},
    "test": { "dependsOn": ["build"] }
  }
}

// Root package.json - ONLY delegates, no task logic
{
  "scripts": {
    "build": "turbo run build",
    "lint": "turbo run lint",
    "test": "turbo run test"
  }
}

// DO NOT DO THIS - defeats parallelization
// Root package.json
{
  "scripts": {
    "build": "cd apps/web && next build && cd ../api && tsc",
    "lint": "eslint apps/ packages/",
    "test": "vitest"
  }
}

Root Tasks (//#taskname) are ONLY for tasks that truly cannot exist in packages (rare).

Secondary Rule: turbo run vs turbo

Always use turbo run when the command is written into code:

// package.json - ALWAYS "turbo run"
{
  "scripts": {
    "build": "turbo run build"
  }
}

# CI workflows - ALWAYS "turbo run"
- run: turbo run build --affected

The shorthand turbo <tasks> is ONLY for one-off terminal commands typed directly by humans or agents. Never write turbo build into package.json, CI, or scripts.

Quick Decision Trees

"I need to configure a task"

Configure a task?
├─ Define task dependencies → references/configuration/tasks.md
├─ Lint/check-types (parallel + caching) → Use Transit Nodes pattern (see below)
├─ Specify build outputs → references/configuration/tasks.md#outputs
├─ Handle environment variables → references/environment/RULE.md
├─ Set up dev/watch tasks → references/configuration/tasks.md#persistent
├─ Package-specific config → references/configuration/RULE.md#package-configurations
└─ Global settings (cacheDir, daemon) → references/configuration/global-options.md

"My cache isn't working"

Cache problems?
├─ Tasks run but outputs not restored → Missing `outputs` key
├─ Cache misses unexpectedly → references/caching/gotchas.md
├─ Need to debug hash inputs → Use --summarize or --dry
├─ Want to skip cache entirely → Use --force or cache: false
├─ Remote cache not working → references/caching/remote-cache.md
└─ Environment causing misses → references/environment/gotchas.md

"I want to run only changed packages"

Run only what changed?
├─ Changed packages + dependents (RECOMMENDED) → turbo run build --affected
├─ Custom base branch → --affected --affected-base=origin/develop
├─ Manual git comparison → --filter=...[origin/main]
└─ See all filter options → references/filtering/RULE.md

--affected is the primary way to run only changed packages. It automatically compares against the default branch and includes dependents.

"I want to filter packages"

Filter packages?
├─ Only changed packages → --affected (see above)
├─ By package name → --filter=web
├─ By directory → --filter=./apps/*
├─ Package + dependencies → --filter=web...
├─ Package + dependents → --filter=...web
└─ Complex combinations → references/filtering/patterns.md

"Environment variables aren't working"

Environment issues?
├─ Vars not available at runtime → Strict mode filtering (default)
├─ Cache hits with wrong env → Var not in `env` key
├─ .env changes not causing rebuilds → .env not in `inputs`
├─ CI variables missing → references/environment/gotchas.md
└─ Framework vars (NEXT_PUBLIC_*) → Auto-included via inference

"I need to set up CI"

CI setup?
├─ GitHub Actions → references/ci/github-actions.md
├─ Vercel deployment → references/ci/vercel.md
├─ Remote cache in CI → references/caching/remote-cache.md
├─ Only build changed packages → --affected flag
├─ Skip unnecessary builds → turbo-ignore (references/cli/commands.md)
└─ Skip container setup when no changes → turbo-ignore

"I want to watch for changes during development"

Watch mode?
├─ Re-run tasks on change → turbo watch (references/watch/RULE.md)
├─ Dev servers with dependencies → Use `with` key (references/configuration/tasks.md#with)
├─ Restart dev server on dep change → Use `interruptible: true`
└─ Persistent dev tasks → Use `persistent: true`

"I need to create/structure a package"

Package creation/structure?
├─ Create an internal package → references/best-practices/packages.md
├─ Repository structure → references/best-practices/structure.md
├─ Dependency management → references/best-practices/dependencies.md
├─ Best practices overview → references/best-practices/RULE.md
├─ JIT vs Compiled packages → references/best-practices/packages.md#compilation-strategies
└─ Sharing code between apps → references/best-practices/RULE.md#package-types

"How should I structure my monorepo?"

Monorepo structure?
├─ Standard layout (apps/, packages/) → references/best-practices/RULE.md
├─ Package types (apps vs libraries) → references/best-practices/RULE.md#package-types
├─ Creating internal packages → references/best-practices/packages.md
├─ TypeScript configuration → references/best-practices/structure.md#typescript-configuration
├─ ESLint configuration → references/best-practices/structure.md#eslint-configuration
├─ Dependency management → references/best-practices/dependencies.md
└─ Enforce package boundaries → references/boundaries/RULE.md

"I want to enforce architectural boundaries"

Enforce boundaries?
├─ Check for violations → turbo boundaries
├─ Tag packages → references/boundaries/RULE.md#tags
├─ Restrict which packages can import others → references/boundaries/RULE.md#rule-types
└─ Prevent cross-package file imports → references/boundaries/RULE.md

Critical Anti-Patterns

Using turbo Shorthand in Code

turbo run is recommended in package.json scripts and CI pipelines. The shorthand turbo <task> is intended for interactive terminal use.

// WRONG - using shorthand in package.json
{
  "scripts": {
    "build": "turbo build",
    "dev": "turbo dev"
  }
}

// CORRECT
{
  "scripts": {
    "build": "turbo run build",
    "dev": "turbo run dev"
  }
}

# WRONG - using shorthand in CI
- run: turbo build --affected

# CORRECT
- run: turbo run build --affected

Root Scripts Bypassing Turbo

Root package.json scripts MUST delegate to turbo run, not run tasks directly.

// WRONG - bypasses turbo entirely
{
  "scripts": {
    "build": "bun build",
    "dev": "bun dev"
  }
}

// CORRECT - delegates to turbo
{
  "scripts": {
    "build": "turbo run build",
    "dev": "turbo run dev"
  }
}

Using && to Chain Turbo Tasks

Don't chain turbo tasks with &&. Let turbo orchestrate.

// WRONG - turbo task not using turbo run
{
  "scripts": {
    "changeset:publish": "bun build && changeset publish"
  }
}

// CORRECT
{
  "scripts": {
    "changeset:publish": "turbo run build && changeset publish"
  }
}

prebuild Scripts That Manually Build Dependencies

Scripts like prebuild that manually build other packages bypass Turborepo's dependency graph.

// WRONG - manually building dependencies
{
  "scripts": {
    "prebuild": "cd ../../packages/types && bun run build && cd ../utils && bun run build",
    "build": "next build"
  }
}

However, the fix depends on whether workspace dependencies are declared:

1. If dependencies ARE declared (e.g., "@repo/types": "workspace:*" in package.json), remove the prebuild script. Turbo's dependsOn: ["^build"] handles this automatically.

2. If dependencies are NOT declared, the prebuild exists because ^build won't trigger without a dependency relationship. The fix is to:

   • Add the dependency to package.json: "@repo/types": "workspace:*"
   • Then remove the prebuild script

// CORRECT - declare dependency, let turbo handle build order
// package.json
{
  "dependencies": {
    "@repo/types": "workspace:*",
    "@repo/utils": "workspace:*"
  },
  "scripts": {
    "build": "next build"
  }
}

// turbo.json
{
  "tasks": {
    "build": {
      "dependsOn": ["^build"]
    }
  }
}

Key insight: ^build only runs build in packages listed as dependencies. No dependency declaration = no automatic build ordering.

Overly Broad globalDependencies

globalDependencies affects ALL tasks in ALL packages. Be specific.

// WRONG - heavy hammer, affects all hashes
{
  "globalDependencies": ["**/.env.*local"]
}

// BETTER - move to task-level inputs
{
  "globalDependencies": [".env"],
  "tasks": {
    "build": {
      "inputs": ["$TURBO_DEFAULT$", ".env*"],
      "outputs": ["dist/**"]
    }
  }
}

Repetitive Task Configuration

Look for repeated configuration across tasks that can be collapsed. Turborepo supports shared configuration patterns.

// WRONG - repetitive env and inputs across tasks
{
  "tasks": {
    "build": {
      "env": ["API_URL", "DATABASE_URL"],
      "inputs": ["$TURBO_DEFAULT$", ".env*"]
    },
    "test": {
      "env": ["API_URL", "DATABASE_URL"],
      "inputs": ["$TURBO_DEFAULT$", ".env*"]
    },
    "dev": {
      "env": ["API_URL", "DATABASE_URL"],
      "inputs": ["$TURBO_DEFAULT$", ".env*"],
      "cache": false,
      "persistent": true
    }
  }
}

// BETTER - use globalEnv and globalDependencies for shared config
{
  "globalEnv": ["API_URL", "DATABASE_URL"],
  "globalDependencies": [".env*"],
  "tasks": {
    "build": {},
    "test": {},
    "dev": {
      "cache": false,
      "persistent": true
    }
  }
}

When to use global vs task-level:

• globalEnv / globalDependencies - affects ALL tasks, use for truly shared config
• Task-level env / inputs - use when only specific tasks need it

NOT an Anti-Pattern: Large env Arrays

A large env array (even 50+ variables) is not a problem. It usually means the user was thorough about declaring their build's environment dependencies. Do not flag this as an issue.

Using --parallel Flag

The --parallel flag bypasses Turborepo's dependency graph. If tasks need parallel execution, configure dependsOn correctly instead.

# WRONG - bypasses dependency graph
turbo run lint --parallel

# CORRECT - configure tasks to allow parallel execution
# In turbo.json, set dependsOn appropriately (or use transit nodes)
turbo run lint

Package-Specific Task Overrides in Root turbo.json

When multiple packages need different task configurations, use Package Configurations (turbo.json in each package) instead of cluttering root turbo.json with package#task overrides.

// WRONG - root turbo.json with many package-specific overrides
{
  "tasks": {
    "test": { "dependsOn": ["build"] },
    "@repo/web#test": { "outputs": ["coverage/**"] },
    "@repo/api#test": { "outputs": ["coverage/**"] },
    "@repo/utils#test": { "outputs": [] },
    "@repo/cli#test": { "outputs": [] },
    "@repo/core#test": { "outputs": [] }
  }
}

// CORRECT - use Package Configurations
// Root turbo.json - base config only
{
  "tasks": {
    "test": { "dependsOn": ["build"] }
  }
}

// packages/web/turbo.json - package-specific override
{
  "extends": ["//"],
  "tasks": {
    "test": { "outputs": ["coverage/**"] }
  }
}

// packages/api/turbo.json
{
  "extends": ["//"],
  "tasks": {
    "test": { "outputs": ["coverage/**"] }
  }
}

Benefits of Package Configurations:

• Keeps configuration close to the code it affects
• Root turbo.json stays clean and focused on base patterns
• Easier to understand what's special about each package
• Works with $TURBO_EXTENDS$ to inherit + extend arrays

When to use package#task in root:

• Single package needs a unique dependency (e.g., "deploy": { "dependsOn": ["web#build"] })
• Temporary override while migrating

See references/configuration/RULE.md#package-configurations for full details.

Using ../ to Traverse Out of Package in inputs

Don't use relative paths like ../ to reference files outside the package. Use $TURBO_ROOT$ instead.

// WRONG - traversing out of package
{
  "tasks": {
    "build": {
      "inputs": ["$TURBO_DEFAULT$", "../shared-config.json"]
    }
  }
}

// CORRECT - use $TURBO_ROOT$ for repo root
{
  "tasks": {
    "build": {
      "inputs": ["$TURBO_DEFAULT$", "$TURBO_ROOT$/shared-config.json"]
    }
  }
}

Missing outputs for File-Producing Tasks

Before flagging missing outputs, check what the task actually produces:

1. Read the package's script (e.g., "build": "tsc", "test": "vitest")
2. Determine if it writes files to disk or only outputs to stdout
3. Only flag if the task produces files that should be cached

// WRONG: build produces files but they're not cached
{
  "tasks": {
    "build": {
      "dependsOn": ["^build"]
    }
  }
}

// CORRECT: build outputs are cached
{
  "tasks": {
    "build": {
      "dependsOn": ["^build"],
      "outputs": ["dist/**"]
    }
  }
}

Common outputs by framework:

• Next.js: [".next/**", "!.next/cache/**"]
• Vite/Rollup: ["dist/**"]
• tsc: ["dist/**"] or custom outDir

TypeScript --noEmit can still produce cache files:

When incremental: true in tsconfig.json, tsc --noEmit writes .tsbuildinfo files even without emitting JS. Check the tsconfig before assuming no outputs:

// If tsconfig has incremental: true, tsc --noEmit produces cache files
{
  "tasks": {
    "typecheck": {
      "outputs": ["node_modules/.cache/tsbuildinfo.json"] // or wherever tsBuildInfoFile points
    }
  }
}

To determine correct outputs for TypeScript tasks:

1. Check if incremental or composite is enabled in tsconfig
2. Check tsBuildInfoFile for custom cache location (default: alongside outDir or in project root)
3. If no incremental mode, tsc --noEmit produces no files

^build vs build Confusion

{
  "tasks": {
    // ^build = run build in DEPENDENCIES first (other packages this one imports)
    "build": {
      "dependsOn": ["^build"]
    },
    // build (no ^) = run build in SAME PACKAGE first
    "test": {
      "dependsOn": ["build"]
    },
    // pkg#task = specific package's task
    "deploy": {
      "dependsOn": ["web#build"]
    }
  }
}

Envir

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