diff --git a/vscode/src/webhook/relay.ts b/vscode/src/webhook/relay.ts
index 38c7f33..5b662b4 100644
--- a/vscode/src/webhook/relay.ts
+++ b/vscode/src/webhook/relay.ts
@@ -36,9 +36,13 @@ function processAlive(pid: number): boolean {
 export class PeerRegistry {
   constructor(private readonly dir: string) {}
 
+  /** 先写进临时文件再改名成端口号，别的窗口列登记时就不会读到还没写进 pid 的空文件、把它当成已退出的窗口删掉。 */
   async add(port: number): Promise<void> {
     await fsp.mkdir(this.dir, { recursive: true })
-    await fsp.writeFile(path.join(this.dir, String(port)), String(process.pid))
+    const file = path.join(this.dir, String(port))
+    const temp = `${file}.${process.pid}.tmp`
+    await fsp.writeFile(temp, String(process.pid))
+    await fsp.rename(temp, file)
   }
 
   async remove(port: number): Promise<void> {
diff --git a/vscode/src/webhook/server.test.ts b/vscode/src/webhook/server.test.ts
index 4507546..e72edfe 100644
--- a/vscode/src/webhook/server.test.ts
+++ b/vscode/src/webhook/server.test.ts
@@ -2,10 +2,11 @@ import type { IncomingHttpHeaders } from 'node:http'
 import type { WebhookEvent } from './eventParser'
 import { Buffer } from 'node:buffer'
 import { createHmac } from 'node:crypto'
-import { mkdirSync, mkdtempSync, readdirSync, rmSync, writeFileSync } from 'node:fs'
+import { promises as fsp, mkdirSync, mkdtempSync, readdirSync, rmSync, writeFileSync } from 'node:fs'
 import { tmpdir } from 'node:os'
 import path from 'node:path'
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
+import { PeerRegistry } from './relay'
 import { handleWebhookRequest, WebhookServer } from './server'
 
 const mocks = vi.hoisted(() => ({ log: vi.fn() }))
@@ -206,6 +207,26 @@ describe('同一台机器多个窗口共用端口', () => {
     await vi.waitFor(() => expect(readdirSync(dir)).toEqual([]))
   })
 
+  it('登记文件写到一半时别的窗口来列登记，不会把它当成陈旧条目删掉', async () => {
+    const registry = new PeerRegistry(path.join(peerRoot, '17421'))
+    const remove = vi.spyOn(registry, 'remove')
+    const realWriteFile = fsp.writeFile.bind(fsp)
+    const write = vi.spyOn(fsp, 'writeFile').mockImplementation(async (file, data) => {
+      // 文件已经建好、pid 还没写进去的那一刻，占着端口的窗口正好来列登记。
+      await realWriteFile(file, '')
+      await registry.ports()
+      await realWriteFile(file, data)
+    })
+    try {
+      await registry.add(50000)
+    }
+    finally {
+      write.mockRestore()
+    }
+    expect(remove).not.toHaveBeenCalled()
+    expect(await registry.ports()).toEqual([50000])
+  })
+
   it('同一端口重复 start 不会自己挤掉自己', async () => {
     const hub = open()
     await hub.server.start(0)