test(windows): cover teardown decisions deterministically

packages/lsp/lsp-local/src/connection.ts

@@ -110,6 +110,25 @@ export function signalProcessGroup(
   run(target, signal)
 }
 
+/**
+ * Wait until a process-tree liveness probe reports exit.
+ * @param isAlive - process-tree liveness probe.
+ * @param signal - optional bound for the wait.
+ * @param yieldNow - event-loop yield primitive.
+ * @returns `true` when the tree exited, or `false` when the signal aborted first.
+ */
+export async function waitForTreeExit(
+  isAlive: () => boolean,
+  signal?: AbortSignal,
+  yieldNow: () => Promise<unknown> = yieldToEventLoop,
+): Promise<boolean> {
+  while (isAlive()) {
+    if (signal?.aborted) return false
+    await yieldNow()
+  }
+  return true
+}
+
 /**
  * Signal a detached process tree with platform-correct semantics and a direct-child fallback.
  * @param platform - host platform.
@@ -269,11 +288,7 @@ export class LspConnection {
    * @returns `true` when the tree exited, or `false` when the signal aborted first.
    */
   async waitForProcessTreeExit(signal?: AbortSignal): Promise<boolean> {
-    while (this.processTreeAlive()) {
-      if (signal?.aborted) return false
-      await yieldToEventLoop()
-    }
-    return true
+    return await waitForTreeExit(this.processTreeAlive.bind(this), signal)
   }
 
   /**

packages/lsp/lsp-local/src/index.ts

@@ -221,10 +221,6 @@ class LocalLspProvider implements LspProvider {
       // synchronous get-or-create so every spawned process remains owned by teardown.
       this.assertActive(signal)
       let instance = this.instanceFor(workspace)
-      if (instance.dead) {
-        this.evictIfCurrent(workspace, instance)
-        instance = this.instanceFor(workspace)
-      }
       try {
         return await instance.query(request, source, signal)
       } catch (error) {

packages/lsp/lsp-local/src/instance.ts

@@ -39,6 +39,15 @@ export interface InstanceSpec extends ConnectionSpec {
   readonly killGraceMs: number
 }
 
+/**
+ * Force-kill a process tree only when graceful termination did not make it exit.
+ * @param treeExited - whether the tree exited within its grace period.
+ * @param forceKill - forceful process-tree termination primitive.
+ */
+export function escalateProcessTree(treeExited: boolean, forceKill: () => void): void {
+  if (!treeExited) forceKill()
+}
+
 /**
  * A single initialized server process. Not exported as a provider — the provider single-flights and
  * pools these. `query()` serializes; `dispose()` rejects queued work and tears the process down.
@@ -297,7 +306,7 @@ export class LspInstance {
     } finally {
       graceDeadline[Symbol.dispose]()
     }
-    if (!treeExited) this.connection.kill()
+    escalateProcessTree(treeExited, this.connection.kill.bind(this.connection))
     await Promise.all([
       this.connection.closed,
       this.connection.waitForProcessTreeExit(),

packages/lsp/lsp-local/tests/connection.spec.ts

@@ -5,6 +5,7 @@ import {
   signalProcessGroup,
   signalProcessTree,
   taskkillProcessTree,
+  waitForTreeExit,
 } from '@deepseek-ai/dsh-lsp-local/src/connection.ts'
 import type {
   ConnectionWriter,
@@ -248,6 +249,19 @@ describe('process-tree signaling', () => {
     expect(run).toHaveBeenCalledWith(-42, 'SIGKILL')
   })
 
+  it('waits for tree exit and stops when its bound aborts', async () => {
+    const isAlive = vi.fn()
+      .mockReturnValueOnce(true)
+      .mockReturnValue(false)
+    const yieldNow = vi.fn(() => Promise.resolve())
+    await expect(waitForTreeExit(isAlive, undefined, yieldNow)).resolves.toBe(true)
+    expect(yieldNow).toHaveBeenCalledOnce()
+
+    const controller = new AbortController()
+    controller.abort()
+    await expect(waitForTreeExit(() => true, controller.signal, yieldNow)).resolves.toBe(false)
+  })
+
   it('uses taskkill for a Windows tree and a negative pid for a POSIX group', () => {
     const operations = fakeProcessTreeOperations()
     signalProcessTree('win32', 42, 'SIGTERM', operations)

packages/lsp/lsp-local/tests/instance.spec.ts

@@ -1,4 +1,4 @@
-import { afterEach, beforeEach, describe, expect, it } from 'vitest'
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 import { mkdtemp, mkdir, readFile, rm, writeFile, realpath } from 'node:fs/promises'
 import { tmpdir } from 'node:os'
 import { join } from 'node:path'
@@ -6,6 +6,7 @@ import { pathToFileURL, fileURLToPath } from 'node:url'
 import { LspInstance, readHostSource } from '@deepseek-ai/dsh-lsp-local'
 import { encodeMessage } from '@deepseek-ai/dsh-lsp-local'
 import type { ConnectionWriter } from '@deepseek-ai/dsh-lsp-local/src/connection.ts'
+import { escalateProcessTree } from '@deepseek-ai/dsh-lsp-local/src/instance.ts'
 import type { InstanceSpec } from '@deepseek-ai/dsh-lsp-local/src/instance.ts'
 import type { LspProviderQuery, LspQueryResult } from '@deepseek-ai/dsh-lsp'
 
@@ -242,6 +243,14 @@ describe('LspInstance query and abort', () => {
 })
 
 describe('LspInstance disposal', () => {
+  it('escalates only when the process tree survives its grace period', () => {
+    const forceKill = vi.fn()
+    escalateProcessTree(false, forceKill)
+    expect(forceKill).toHaveBeenCalledOnce()
+    escalateProcessTree(true, forceKill)
+    expect(forceKill).toHaveBeenCalledOnce()
+  })
+
   it('lets a server finish protocol exit before signal escalation', async () => {
     const marker = join(root, 'graceful-exit.log')
     const instance = makeInstance({