diff --git a/build/register.js b/build/register.js
index a74813f041..39e94721cc 100644
--- a/build/register.js
+++ b/build/register.js
@@ -68,7 +68,7 @@ require.extensions['.ts'] = (module, filename) => {
     format: 'cjs',
     loader: 'ts',
     charset: 'utf8',
-    target: 'es2020',
+    target: 'es2019',
     define,
   })
   cache[filename] = code
diff --git a/packages/cli/src/worker/index.ts b/packages/cli/src/worker/index.ts
index d972e7cc8f..5dfe84b8a4 100644
--- a/packages/cli/src/worker/index.ts
+++ b/packages/cli/src/worker/index.ts
@@ -76,4 +76,4 @@ app.start().then(() => {
   for (const name in loader.cache) {
     loader.diagnose(name)
   }
-})
+}, handleException)
diff --git a/packages/koishi/package.json b/packages/koishi/package.json
index 702bba20ec..676dad8bcd 100644
--- a/packages/koishi/package.json
+++ b/packages/koishi/package.json
@@ -49,6 +49,7 @@
     "ns-require": "^1.1.2",
     "parseurl": "^1.3.3",
     "path-to-regexp": "^6.2.0",
+    "portfinder": "^1.0.28",
     "proxy-agent": "^5.0.0",
     "ws": "^8.6.0"
   }
diff --git a/packages/koishi/src/patch.ts b/packages/koishi/src/patch.ts
index 453fd53dc4..e18486de76 100644
--- a/packages/koishi/src/patch.ts
+++ b/packages/koishi/src/patch.ts
@@ -1,5 +1,6 @@
 import { App, Context } from '@koishijs/core'
 import { trimSlash } from '@koishijs/utils'
+import { getPortPromise } from 'portfinder'
 import ns from 'ns-require'
 
 declare module '@koishijs/core' {
@@ -43,9 +44,16 @@ Context.prototype.plugin = function (this: Context, entry: any, config?: any) {
 
 const start = App.prototype.start
 App.prototype.start = async function (this: App, ...args) {
-  const { host, port, selfUrl } = this.options
-  if (selfUrl) this.options.selfUrl = trimSlash(selfUrl)
-  if (port) {
+  if (this.options.selfUrl) {
+    this.options.selfUrl = trimSlash(this.options.selfUrl)
+  }
+
+  if (this.options.port) {
+    this.options.port = await getPortPromise({
+      port: this.options.port,
+      stopPort: this.options.maxPort || this.options.port,
+    })
+    const { host, port } = this.options
     await new Promise<void>(resolve => this._httpServer.listen(port, host, resolve))
     this.logger('app').info('server listening at %c', `http://${host}:${port}`)
     this.on('dispose', () => {
@@ -54,5 +62,6 @@ App.prototype.start = async function (this: App, ...args) {
       this._httpServer?.close()
     })
   }
+
   return start.call(this, ...args)
 }
diff --git a/packages/koishi/src/router.ts b/packages/koishi/src/router.ts
index 743092ca97..31ec2105cb 100644
--- a/packages/koishi/src/router.ts
+++ b/packages/koishi/src/router.ts
@@ -32,6 +32,7 @@ declare module '@koishijs/core' {
       interface Network {
         host?: string
         port?: number
+        maxPort?: number
         selfUrl?: string
       }
     }
@@ -41,6 +42,7 @@ declare module '@koishijs/core' {
 defineProperty(App.Config, 'Network', Schema.object({
   host: Schema.string().default('localhost').description('要监听的 IP 地址。如果将此设置为 `0.0.0.0` 将监听所有地址，包括局域网和公网地址。'),
   port: Schema.natural().max(65535).description('要监听的端口。'),
+  maxPort: Schema.natural().max(65535).description('允许监听的最大端口号。'),
   selfUrl: Schema.string().role('url').description('应用暴露在公网的地址。部分插件 (例如 github 和 telegram) 需要用到。'),
 }).description('网络设置'))