wxt/docs/guide/essentials/config/hooks.md

Hooks

WXT includes a system that lets you hook into the build process and make changes.

Here's an example hook that modifies the manifest.json file before it is written to the output directory:

// wxt.config.ts
export default defineConfig({
  hooks: {
    'build:manifestGenerated': (wxt, manifest) => {
      if (wxt.config.mode === 'development') {
        manifest.title += ' (DEV)';
      }
    },
  },
});

Most hooks provide the wxt object as the first argument. It contains the resolved config and other info about the current build.

Putting one-off hooks like this in your config file is simple, but if you find yourself writing lots of hooks, you should extract them into WXT Modules instead.