Router

@async/web/router owns pure structured route specs. It does not execute requests, implement cache stores, own platform APIs, or provision providers.

Use common route helpers from @async/web when authoring an app:

import {
  defineApp,
  mount,
  toApp
} from '@async/web';

Use @async/web/router directly for richer route composition and inspection:

import {
  host,
  method,
  mount,
  printRouteTable,
  splitTraffic,
  toApp,
  tryApp
} from '@async/web/router';

const routes = [
  host('admin.acme.async.run', toApp('admin')),
  method('GET', '/api/health', toApp('api')),
  mount('/api', tryApp({}, [
    toApp('bff'),
    toApp('api')
  ])),
  splitTraffic([
    {
      name: 'stable',
      weight: 90,
      to: toApp('web')
    },
    {
      name: 'preview',
      weight: 10,
      to: toApp('preview')
    }
  ])
];

console.log(printRouteTable(routes));

Route specs use type, not kind, so they are inspectable and serializable. Helper functions use config-first options where they need options; for example tryApp({}, [toApp('bff'), toApp('api')]) falls through on 404 by default. WebRuntime remains responsible for execution, cache behavior, platform fetch re-entry, runtime context, tracing, streaming, virtual filesystem, provider placement, and browser/service-worker simulation.

Distribution is not a route type. Author logical routes such as mount('/api', toApp('api')), then express physical intent through app/runtime policy such as runtime, placement, and region.