App config

Experimental

The app config is experimental: the file name, the options and their behavior may change.

The app config is a file with the options of the LikeC4 application, its build and the dev server.
The CLI reads it, so you do not have to repeat the same flags in every command:

likec4.app.config.ts

import { defineAppConfig } from 'likec4/config'

export default defineAppConfig({
  title: 'My Architecture',
  theme: 'dark',
  customization: './likec4.customization.tsx',
  build: {
    outDir: './dist',
  },
  server: {
    port: 3000,
  },
})

# Both commands use the title, the theme and the customization file
likec4 start
likec4 build

Nota

The app config is not the project configuration. likec4.config.json describes a LikeC4 project (its name, styles, includes). likec4.app.config.ts describes how the CLI builds and serves the application. The Vite plugin does not read the app config: pass the same options to LikeC4VitePlugin. To see which config file sets what, read Configuration files.

Config file

The file is JavaScript or TypeScript, with one of these names:

• likec4.app.config.ts, likec4.app.config.mts, likec4.app.config.cts
• likec4.app.config.js, likec4.app.config.mjs, likec4.app.config.cjs

It must default-export an object. defineAppConfig only adds types, a plain object works too.
The CLI provides likec4/config when it loads the file, so the import works even if likec4 is not installed next to it (for example, with npx likec4).

The CLI takes the first file it finds:

1. The file given by --app-config <file>. It is an error if this file does not exist.
2. The workspace, if you give it to the command (as the [path] argument or the LIKEC4_WORKSPACE environment variable).
3. The current directory.

--no-app-config skips the file. When a file is loaded, the command prints its path.

likec4 build --app-config ./configs/likec4.app.config.ts
likec4 build --no-app-config

Options

Option	Default	Description
title	'LikeC4'	Title of the application. Used where there is no project, e.g. on the list of projects, and on the pages of a project without a title in its project config
theme	follows the system preference	Default color scheme of the application: 'light' or 'dark'
useHashHistory	false	Hash-based navigation, e.g. /#/view instead of /view
webcomponentPrefix	'likec4'	Prefix for web components, e.g. 'c4' generates <c4-view/>
customization	none	Path to the file with UI customization
workspace	current directory	Directory with LikeC4 sources
graphviz	'binary' inside a container, 'wasm' otherwise	Layout engine: bundled WebAssembly ('wasm') or the dot binary from PATH ('binary')
base	/	Base URL the application is served from, e.g. /pages/
publicDir	none	Directory whose files are copied to the output as-is
build		Options of the production build, see below
server		Options of the dev server, see below

build

Options of likec4 build.

Option	Default	Description
outDir	dist in the workspace	Output directory
singleFile	false	Output a single self-contained HTML file. Such a build always uses hash-based navigation
webcomponent	true	Build web components. likec4 start uses this option too

server

Options of likec4 start.

Option	Default	Description
host	localhost, or 0.0.0.0 inside a container	Address of the network interface to listen on
port	5173, or another free port if it is taken	Port of the dev server
hmrPort	auto-discovered from 24678–24690	Port of the HMR WebSocket server
allowedHosts	all hosts	Hostnames allowed to access the dev server

Validation

Unknown options are errors, at the top level and inside build and server.
The command stops and reports the file and the invalid options.

Paths

• Paths in the config file (workspace, customization, publicDir, build.outDir) are relative to the directory of the file.
• Paths in command-line flags are relative to the current directory.

Flags and environment variables

Every option has a command-line flag, and some have an environment variable.
The first value that is set wins:

1. Command-line flag
2. Environment variable
3. App config
4. Default

Option	Flag	Environment variable
workspace	[path] argument	LIKEC4_WORKSPACE
graphviz	--use-dot, --no-use-dot
title	--title, -t
theme	--theme
useHashHistory	--use-hash-history
webcomponentPrefix	--webcomponent-prefix, -w
customization	--customization
base	--base, --base-url
publicDir	--public, --public-dir
build.outDir	--output, -o
build.singleFile	--output-single-file
build.webcomponent	--build-webcomponent, --no-build-webcomponent
server.host	--listen, -l
server.port	--port	PORT
server.hmrPort	--hmr-port	HMR_PORT
server.allowedHosts	--allowed-host

--allowed-host replaces the list from the config, it does not add to it.

Commands

These commands read the app config:

Command	What it takes from the config
likec4 start	All top-level options, build.webcomponent and server
likec4 build	All top-level options and build
likec4 preview	workspace, base, build.outDir
likec4 export png, likec4 export jpg	workspace, graphviz, customization
likec4 gen react	workspace, graphviz, customization
likec4 gen webcomponent	workspace, graphviz, customization, webcomponentPrefix

Other commands ignore the file.

Two things to know about the export to PNG and JPEG:

• --theme of the export is the color scheme of the images (light by default). The theme option of the config is not used.
• With --server-url the export does not start a server and takes screenshots from the one you point it to. customization has no effect then.

Changes in the config

The config is read when the command starts.
likec4 start watches the file and prints a warning when it changes:

likec4.app.config.ts changed, restart to apply

Restart the command to apply the changes. The customization file is different: its changes are applied on the fly.