wireit

Wireit upgrades your npm scripts to make them smarter and more efficient.

Features

• 🙂 Use the npm run commands you already know
• ⛓️ Automatically run dependencies between npm scripts in parallel
• 👀 Watch any script and continuously re-run on changes
• 🥬 Skip scripts that are already fresh
• ♻️ Cache output locally and remotely on GitHub Actions for free
• 🛠️ Works with single packages, npm workspaces, and other monorepos
• ✏️ VSCode plugin gives suggestions, documentation, and warnings as you develop

Contents

• Features
• Install
• Setup
• VSCode Extension
• Discord
• Dependencies
  • Vanilla scripts
  • Cross-package dependencies
• Parallelism
• Extra arguments
• Input and output files
  • Example configuration
  • Default excluded paths
• Incremental build
• Caching
  • Local caching
  • GitHub Actions caching
• Cleaning output
• Watch mode
• Services
• Execution cascade
• Environment variables
• Failures and errors
• Package locks
• Recipes
  • TypeScript
  • ESLint
• Reference
  • Configuration
  • Dependency syntax
  • Environment variable reference
  • Glob patterns
  • Fingerprint
• Requirements
• Related tools
• Contributing

Install

npm i -D wireit

Setup

Wireit works with npm run, it doesn’t replace it. To configure an NPM script for Wireit, move the command into a new wireit section of your package.json, and replace the original script with the wireit command.

{
  "scripts": {
    "build": "tsc"
  }
}

{
  "scripts": {
    "build": "wireit"
  },
  "wireit": {
    "build": {
      "command": "tsc"
    }
  }
}

Now when you run npm run build, Wireit upgrades the script to be smarter and more efficient. Wireit also works with node --run, yarn, and pnpm.

You should also add .wireit to your .gitignore file. Wireit uses the .wireit directory to store caches and other data for your scripts.

echo .wireit >> .gitignore

VSCode Extension

If you use VSCode, consider installing the google.wireit extension. It adds documentation on hover, autocomplete, can diagnose a number of common mistakes, and even suggest a refactoring to convert an npm script to use wireit.

Install it from the marketplace or on the command line like:

code --install-extension google.wireit

Discord

Join the Wireit Discord to chat with the Wireit community and get support for your project.

Dependencies

To declare a dependency between two scripts, edit the wireit.<script>.dependencies list:

{
  "scripts": {
    "build": "wireit",
    "bundle": "wireit"
  },
  "wireit": {
    "build": {
      "command": "tsc"
    },
    "bundle": {
      "command": "rollup -c",
      "dependencies": ["build"]
    }
  }
}

Now when you run npm run bundle, the build script will automatically run first.

Vanilla scripts

The scripts you depend on don’t need to be configured for Wireit, they can be vanilla npm scripts. This lets you only use Wireit for some of your scripts, or to upgrade incrementally. Scripts that haven’t been configured for Wireit are always safe to use as dependencies; they just won’t be fully optimized.

Wireit-only scripts

It is valid to define a script in the wireit section that is not in the scripts section, but such scripts can only be used as dependencies from other wireit scripts, and can never be run directly.

Cross-package dependencies

Dependencies can refer to scripts in other npm packages by using a relative path with the syntax <relative-path>:<script-name>. All cross-package dependencies should start with a ".". Cross-package dependencies work well for npm workspaces, as well as in other kinds of monorepos.

{
  "scripts": {
    "build": "wireit"
  },
  "wireit": {
    "build": {
      "command": "tsc",
      "dependencies": ["../other-package:build"]
    }
  }
}

Parallelism

Wireit will run scripts in parallel whenever it is safe to do so according to the dependency graph.

For example, in this diagram, the B and C scripts will run in parallel, while the A script won’t start until both B and C finish.

By default, Wireit will run up to 2 scripts in parallel for every logical CPU core detected on your system. To change this default, set the WIREIT_PARALLEL environment variable to a positive integer, or infinity to run without a limit. You may want to lower this number if you experience resource starvation in large builds. For example, to run only one script at a time:

export WIREIT_PARALLEL=1
npm run build

If two or more separate npm run commands are run for the same Wireit script simultaneously, then only one instance will be allowed to run at a time, while the others wait their turn. This prevents coordination problems that can result in incorrect output files being produced. If output is set to an empty array, then this restriction is removed.

Extra arguments

As with plain npm scripts, you can pass extra arguments to a Wireit script by placing a -- double-dash argument in front of them. Any arguments after a -- are sent to the underlying command, instead of being interpreted as arguments to npm or Wireit:

npm run build -- --verbose

Or in general:

npm run {script} {npm args} {wireit args} -- {script args}

An additional -- is required when using node --run in order to distinguish between arguments intended for node, wireit, and the script itself:

node --run {script} {node args} -- {wireit args} -- {script args}

Input and output files

The files and output properties of wireit.<script> tell Wireit what your script’s input and output files are, respectively. They should be arrays of glob patterns, where paths are interpreted relative to the package directory. They can be set on some, all, or none of your scripts.

Setting these properties allow you to use more features of Wireit:

Example configuration

{
  "scripts": {
    "build": "wireit",
    "bundle": "wireit"
  },
  "wireit": {
    "build": {
      "command": "tsc",
      "files": ["src/**/*.ts", "tsconfig.json"],
      "output": ["lib/**"]
    },
    "bundle": {
      "command": "rollup -c",
      "dependencies": ["build"],
      "files": ["rollup.config.json"],
      "output": ["dist/bundle.js"]
    }
  }
}

Default excluded paths

By default, the following folders are excluded from the files and output arrays:

• .git/
• .hg/
• .svn/
• .wireit/
• .yarn/
• CVS/
• node_modules/

In the highly unusual case that you need to reference a file in one of those folders, set allowUsuallyExcludedPaths: true to remove all default excludes.

Incremental build

Wireit can automatically skip execution of a script if nothing has changed that would cause it to produce different output since the last time it ran. This is called incremental build.

To enable incremental build, configure the input and output files for each script by specifying glob patterns in the wireit.<script>.files and wireit.<script>.output arrays.

ℹ️ If a script doesn’t have a files or output list defined at all, then it will always run, because Wireit doesn’t know which files to check for changes. To tell Wireit it is safe to skip execution of a script that definitely has no input and/or files, set files and/or output to an empty array (files: [], output: []).

Caching

If a script has previously succeeded with the same configuration and input files, then Wireit can copy the output from a cache, instead of running the command. This can significantly improve build and test time.

To enable caching for a script, ensure you have defined both the files and output arrays.

ℹ️ If a script doesn’t produce any output files, it can still be cached by setting output to an empty array ("output": []). Empty output is common for tests, and is useful because it allows you to skip running tests if they previously passed with the exact same inputs.

Local caching

In local mode, Wireit caches output files to the .wireit folder inside each of your packages.

Local caching is enabled by default, unless the CI=true environment variable is detected. To force local caching, set WIREIT_CACHE=local. To disable local caching, set WIREIT_CACHE=none.

Each script retains its 10 most recently used cache entries. Whenever a new entry is written, any entries beyond that limit are evicted, least recently used first. Because an entry is a full copy of the script’s output files, this caps a script’s cache at roughly 10× the size of its output.

To change the limit, set WIREIT_CACHE_MAX_ENTRIES to a positive integer, or to infinity to retain every entry:

export WIREIT_CACHE_MAX_ENTRIES=2

Evicted entries are moved to .wireit/trash and deleted at the end of the run, so that a script is never held up by a large delete. Interrupting that with Ctrl-C is safe — whatever is left is deleted by the next run. Wireit then exits with status 130.

A cache that is already over the limit, such as one written by an earlier version of Wireit, shrinks by one entry per write instead of all at once, so that no single run is held up deleting it. While it holds more than twice the limit, Wireit reminds you once a day with the folders to delete.

Note the limit is applied per script, so a package with many cached scripts will still use a multiple of this space. To free all of it at once, use rm -rf .wireit/*/cache .wireit/*/temp .wireit/trash.

Linked Git worktrees (git worktree add) keep their own .wireit cache folders. Set WIREIT_CACHE_WORKTREES=true to store a linked worktree’s local cache in the main worktree’s corresponding .wireit folders. Shared entries are named from package-relative paths, so both worktrees hit the same entry. Any other value keeps each worktree’s own cache and the same entry names as before. Worktrees of bare clones, submodules, and checkouts with a separate git dir also keep their own cache, since the main git dir’s parent isn’t a checkout. Lock, fingerprint, and output-manifest files stay in the current worktree. Fingerprints and GitHub Actions caching are unchanged.

Restored files are copied verbatim. Wireit does not rewrite output contents that embed another checkout’s absolute path.

GitHub Actions caching

In GitHub Actions mode, Wireit caches output files to the GitHub Actions cache service. This service is available whenever running in GitHub Actions, and is free for all GitHub users.

ℹ️ GitHub Actions cache entries are automatically deleted after 7 days, or if total usage exceeds 10 GB (the least recently used cache entry is deleted first). See the GitHub Actions documentation for more details.

To enable caching on GitHub Actions, add the following uses clause to your workflow. It can appear anywhere before the first npm run or npm test command:

- uses: google/wireit@setup-github-actions-caching/v2

Example workflow

# File: .github/workflows/tests.yml

name: Tests
on: [push, pull_request]
jobs:
  tests:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v7
      - uses: actions/setup-node@v7
        with:
          node-version: 24
          cache: npm

      # Set up GitHub Actions caching for Wireit.
      - uses: google/wireit@setup-github-actions-caching/v2

      # Install npm dependencies.
      - run: npm ci

      # Run tests. Wireit will automatically use
      # the GitHub Actions cache whenever possible.
      - run: npm test

Cleaning output

Wireit can automatically delete output files from previous runs before executing a script. This is helpful for ensuring that every build is clean and free from outdated files created in previous runs from source files that have since been removed.

Cleaning is enabled by default as long as the output array is defined. To change this behavior, set the wireit.<script>.clean property to one of these values:

Watch mode

In watch mode, Wireit monitors all files of a script, and all files of its transitive dependencies, and when there is a change, it re-runs only the affected scripts. To enable watch mode, first ensure that the files array is defined, and then run:

WIREIT_WATCH=true npm run <script>

The benefit of Wireit’s watch mode over the built-in watch modes of Node and other programs are:

• Wireit watches the entire dependency graph, so a single watch command replaces many built-in ones.
• It prevents problems that can occur when running many separate watch commands simultaneously, such as build steps being triggered before all preceding steps have finished.

By default, watch mode uses whichever filesystem change API is available on your OS. This behavior can be changed with the WIREIT_WATCH_STRATEGY and WIREIT_WATCH_POLL_MS environment variables (see below).

Environment variables

Use the env setting to either directly set environment variables, or to indicate that an externally-defined environment variable affects the behavior of a script.

Setting environment variables directly

If a property value in the env object is a string, then that environment variable will be set to that value when the script’s command runs, overriding any value from the parent process.

Unlike built-in shell environment variable syntaxes, using env to set environment variables works the same in macOS/Linux vs Windows, and in all shells.

Note Setting an environment variable with env does not apply transitively through dependencies. If you need the same environment variable to be set for multiple scripts, you must configure it for each of them.

{
  "wireit": {
    "my-script": {
      "command": "my-command",
      "env": {
        "MY_VARIABLE": "my value"
      }
    }
  }
}

Indicating external environment variables

If an environment variable affects the behavior of a script but is set externally (i.e. it is passed to the wireit parent process), set the env property to {"external": true}. This tells Wireit that if the value of an environment variable changes across executions of a script, then its output should not be re-used. You may also set a default value for the variable to use when none is provided externally.

{
  "wireit": {
    "my-script": {
      "command": "my-command",
      "env": {
        "MY_VARIABLE": {
          "external": true
        },
        "MY_VARIABLE_2": {
          "external": true,
          "default": "foo"
        }
      }
    }
  }
}

Services

By default, Wireit assumes that your scripts will eventually exit by themselves. This is well suited for build and test scripts, but not for long-running processes like servers. To tell Wireit that a process is long-running and not expected to exit by itself, set "service": true.

{
  "scripts": {
    "start": "wireit",
    "build:server": "wireit"
  },
  "wireit": {
    "start": {
      "command": "node my-server.js",
      "service": true,
      "files": ["my-server.js"],
      "dependencies": [
        "build:server",
        {
          "script": "../assets:build",
          "cascade": false
        }
      ]
    },
    "build:server": {
      ...
    }
  }
}

Service lifetime

If a service is run directly (e.g. npm run serve), then it will stay running until the user kills Wireit (e.g. Ctrl-C).

If a service is a dependency of one or more other scripts, then it will start up before any depending script runs, and will shut down after all depending scripts finish.

Service readiness

By default, a service is considered ready as soon as its process spawns, allowing any scripts that depend on that service to start.

However, often times a service needs to perform certain actions before it is safe for dependents to interact with it, such as starting a server and listening on a network interface.

Use service.readyWhen.lineMatches to tell Wireit to monitor the stdout and stderr of the service and defer readiness until a line is printed that matches the given regular expression.

{
  "command": "node my-server.js",
  "service": {
    "readyWhen": {
      "lineMatches": "Server listening on port \\d+"
    }
  }
}

Service restarts

In watch mode, a service will be restarted whenever one of its input files or dependencies change, except for dependencies with cascade set to false.

Service output

Services cannot have output files, because there is no way for Wireit to know when a service has finished writing its output.

If you have a service that produces output, you should define a non-service script that depends on it, and which exits when the service’s output is complete.

Execution cascade

By default, a script always needs to run (or restart in the case of services) if any of its dependencies needed to run, regardless of whether the dependency produced new or relevant output.

This automatic cascade of script execution is the default behavior because it ensures that any possible output produced by a dependent script propagates to all other scripts that might depend on it. In other words, Wireit does not assume that the files array completely describes the inputs to a script with dependencies.

Disabling cascade

This execution cascade behavior can be disabled by expanding a dependency into an object, and setting the cascade property to false:

Note What really happens under the hood is that the cascade property simply controls whether the fingerprint of a script includes the fingerprints of its dependencies, which in turn determines whether a script needs to run or restart.

{
  "dependencies": [
    {
      "script": "foo",
      "cascade": false
    }
  ]
}

Reasons to disable cascade

There are two main reasons you might want to set cascade to false:

1. Your script only consumes a subset of a dependency’s output.

   For example, tsc produces both .js files and .d.ts files, but only the .js files might be consumed by rollup. There is no need to re-bundle when a typings-only changed occurred.

   Note In addition to setting cascade to false, the subset of output that does matter (lib/**/*.js) has been added to the files array.

   {
     "scripts": {
       "build": "wireit",
       "bundle": "wireit"
     },
     "wireit": {
       "build": {
         "command": "tsc",
         "files": ["src/**/*.ts", "tsconfig.json"],
         "output": ["lib/**"]
       },
       "bundle": {
         "command": "rollup -c",
         "dependencies": [
           {
             "script": "build",
             "cascade": false
           }
         ],
         "files": ["rollup.config.json", "lib/**/*.js"],
         "output": ["dist/bundle.js"]
       }
     }
   }
   

2. Your server doesn’t need to restart for certain changes.

   For example, a web server depends on some static assets, but the server reads those assets from disk dynamically on each request. In watch mode, there is no need to restart the server when the assets change.

   Note The build:server dependency uses the default cascade behavior (true), because changing the implementation of the server itself does require the server to be restarted.

   {
     "scripts": {
       "start": "wireit",
       "build:server": "wireit"
     },
     "wireit": {
       "start": {
         "command": "node lib/server.js",
         "service": true,
         "dependencies": [
           "build:server",
           {
             "script": "../assets:build",
             "cascade": false
           }
         ],
         "files": ["lib/**/*.js"]
       },
       "build:server": {
         "command": "tsc",
         "files": ["src/**/*.ts", "tsconfig.json"],
         "output": ["lib/**"]
       }
     }
   }
   

Failures and errors

By default, when a script fails (meaning it returned with a non-zero exit code), all scripts that are already running are allowed to finish, but new scripts are not started.

In some situations a different behavior may be better suited. There are 2 additional modes, which you can set with the WIREIT_FAILURES environment variable. Note that Wireit always ultimately exits with a non-zero exit code if there was a failure, regardless of the mode.

Continue

When a failure occurs in continue mode, running scripts continue, and new scripts are started as long as the failure did not affect their dependencies. This mode is useful if you want a complete picture of which scripts are succeeding and which are failing.

WIREIT_FAILURES=continue

Kill

When a failure occurs in kill mode, running scripts are immediately killed, and new scripts are not started. This mode is useful if you want to be notified as soon as possible about any failures.

WIREIT_FAILURES=kill

Package locks

By default, Wireit automatically treats package manager lock files as input files (package-lock.json for npm and node --run, yarn.lock for yarn, and pnpm-lock.yaml for pnpm). Wireit will look for these lock files in the script’s package, and all parent directories.

This is useful because installing or upgrading your dependencies can affect the behavior of your scripts, so it’s important to re-run them whenever your dependencies change.

To change the name of the package lock file Wireit should look for, specify it in the wireit.<script>.packageLocks array. You can specify multiple filenames here, if needed.

{
  "scripts": {
    "build": "wireit"
  },
  "wireit": {
    "build": {
      "command": "tsc",
      "files": ["src/**/*.ts", "tsconfig.json"],
      "output": ["lib/**"],
      "packageLocks": ["another-package-manager.lock"]
    }
  }
}

If you’re sure that a script isn’t affected by dependencies at all, you can turn off this behavior entirely to improve your cache hit rate by setting wireit.<script>.packageLocks to [].

Recipes

This section contains advice about integrating specific build tools with Wireit.

TypeScript

{
  "scripts": {
    "ts": "wireit"
  },
  "wireit": {
    "ts": {
      "command": "tsc --build --pretty",
      "clean": "if-file-deleted",
      "files": ["src/**/*.ts", "tsconfig.json"],
      "output": ["lib/**", "*.tsbuildinfo"]
    }
  }
}

• Set "incremental": true and use --build to enable incremental compilation, which significantly improves performance.
• Include .tsbuildinfo in output so that it is reset on clean builds. Otherwise tsc will get out of sync and produce incorrect output.
• Set "clean": "if-file-deleted" so that you get fast incremental compilation when sources are changed/added, but also stale outputs are cleaned up when a source is deleted (tsc does not clean up stale outputs by itself).
• Include tsconfig.json in files so that changing your configuration re-runs tsc.
• Use --pretty to get colorful output despite not being attached to a TTY.

ESLint

{
  "scripts": {
    "lint": "wireit"
  },
  "wireit": {
    "lint": {
      "command": "eslint --color --cache --cache-location .eslintcache .",
      "files": ["src/**/*.ts", ".eslintignore", ".eslintrc.cjs"],
      "output": []
    }
  }
}

• Use --cache so that eslint only lints the files that were added or changed since the last run, which significantly improves performance.
• Use --color to get colorful output despite not being attached to a TTY.
• Include config and ignore files in files so that changing your configuration re-runs eslint.

Reference

Configuration

The following properties can be set inside wireit.<script> objects in package.json files:

Dependency syntax

The following syntaxes can be used in the wireit.<script>.dependencies array:

Environment variable reference

The following environment variables affect the behavior of Wireit:

Glob patterns

The following glob syntaxes are supported in the files and output arrays:

Also note these details:

• Paths should always use / (forward-slash) delimiters, even on Windows.
• Paths are interpreted relative to the current package even if there is a leading / (e.g. /foo is the same as foo).
• Whenever a directory is matched, all recursive children of that directory are included.
• files are allowed to reach outside of the current package using e.g. ../foo. output files cannot reference files outside of the current package.
• Symlinks in input files are followed, so that they are identified by their content.
• Symlinks in output files are cached as symlinks, so that restoring from cache doesn’t create unnecessary copies.
• The order of !exclude patterns is significant.
• Hidden/dot files are matched by * and **.
• Patterns are case-sensitive (if supported by the filesystem).

Fingerprint

The following inputs determine the fingerprint for a script. This value is used to determine whether a script can be skipped for incremental build, and whether its output can be restored from cache.

• The command setting.
• The extra arguments set on the command-line.
• The clean setting.
• The output glob patterns.
• The SHA256 content hashes of all files matching files.
• The SHA256 content hashes of all files matching packageLocks in the current package and all parent directories.
• The name, main, type, exports, imports, types, typings, and typesVersions fields of the package’s package.json file.
• The environment variable values configured in env.
• The system platform (e.g. linux, win32).
• The system CPU architecture (e.g. x64).
• The system Node version (e.g. 24.11.1).
• The fingerprint of all transitive dependencies, unless cascade is set to false.

When using GitHub Actions caching, the following input also affects the fingerprint:

• The ImageOS environment variable (e.g. ubuntu20, macos11).

Requirements

Wireit is supported on Linux, macOS, and Windows.

Wireit is supported on Node 18+.

Wireit scripts can be launched via npm, node --run, pnpm, and yarn.

Related tools

Wireit shares a number of features with these other great tools, and we highly recommend you check them out too:

• Nx
• Turborepo
• Chomp
• Bazel
• [Nix] (https://nixos.org/)

Here are some things you might especially like about Wireit:

• Feels like npm. When you use Wireit, you’ll continue typing the same npm commands you already use, like npm run build and npm test. There are no new command-line tools to learn, and there’s only one way to run each script. Your script config stays in your package.json, too. Wireit is designed to be the minimal addition to npm needed to get script dependencies and incremental build.

• Caching with GitHub Actions. Wireit supports caching build artifacts and test results directly through GitHub Actions, without any extra third-party services. Just add a single uses: line to your workflows.

• Watch any script. Want to automatically re-run your build and tests whenever you make a change? Type npm test --watch. Any script you’ve configured using Wireit can be watched by typing --watch after it.

• Great for single packages and monorepos. Wireit has no opinion about how your packages are arranged. It works great with single packages, because you can link together scripts within the same package. It also works great with any kind of monorepo, because you can link together scripts across different packages using relative paths.

• Complements npm workspaces. We think Wireit could be the missing tool that unlocks the potential for npm workspaces to become the best way to set up monorepos. To use Wireit with npm workspaces, you’ll just use standard npm workspace commands like npm run build -ws.

• Adopt incrementally. Wireit scripts can depend on plain npm scripts, so they can be freely mixed. This means you can use Wireit only for the parts of your build that need it most, or you can try it out on a script-by-script basis without changing too much at the same time.

Contributing

See CONTRIBUTING.md