# Dev Server

URL: /docs/usage/dev/
Section: usage
Tags: dev, hot-reload, development

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Milo includes a lightweight dev server that watches template files and live-reloads your app when they change. No watchdog dependency — just filesystem polling. CLI usage milo dev myapp:app milo dev myapp:app --watch ./templates --poll 0.25 The myapp:app argument follows the module:attribute convention. Milo imports the module and looks up the App instance. Programmatic usage from milo import App, DevServer app = App(template="dashboard.kida", reducer=reducer, initial_state=None) server = DevServer(app, watch_dirs=("./templates",), poll_interval=0.5) server.run() How it works flowchart LR FS[Filesystem] -->|poll mtime| DS[DevServer] DS -->|"@@HOT_RELOAD"| Store Store --> Reducer Reducer --> Render[Re-render] 1PollDevServer watches directories for *.kida changes The server polls watched directories at a configurable interval, comparing file mtimes. 2DetectWhen a template file changes When a file's mtime changes, DevServer dispatches @@HOT_RELOAD with the changed file path. 3ReloadTemplate environment re-reads the file Your reducer can handle @@HOT_RELOAD to trigger re-rendering or state updates. The template environment re-reads the file on next render. The polling approach has no native dependencies and works identically across macOS, Linux, and Windows. Configuration Parameter Default Description watch_dirs () Directories to watch for template changes poll_interval 0.5 Seconds between filesystem polls Tip Tip Set --poll 0.1 for faster feedback during active template iteration. The default 0.5s is a good balance between responsiveness and CPU usage.

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Metadata:
- Author: lbliii
- Word Count: 207
- Reading Time: 1 minutes