diff --git a/src/main/services/infrastructure/CliInstallerService.ts b/src/main/services/infrastructure/CliInstallerService.ts
index f8f62b84..61948121 100644
--- a/src/main/services/infrastructure/CliInstallerService.ts
+++ b/src/main/services/infrastructure/CliInstallerService.ts
@@ -17,7 +17,7 @@
  * - Human-readable error messages per phase
  */
 
-import { execCli, spawnCli } from '@main/utils/childProcess';
+import { execCli, killProcessTree, spawnCli } from '@main/utils/childProcess';
 import { getHomeDir } from '@main/utils/pathDecoder';
 import { getErrorMessage } from '@shared/utils/errorHandling';
 import { createLogger } from '@shared/utils/logger';
@@ -467,7 +467,7 @@ export class CliInstallerService {
       });
 
       const timeout = setTimeout(() => {
-        child.kill();
+        killProcessTree(child);
         reject(
           new Error(
             `Timed out after ${INSTALL_TIMEOUT_MS / 1000}s. ` +
diff --git a/src/main/services/team/TeamProvisioningService.ts b/src/main/services/team/TeamProvisioningService.ts
index 53845dd7..402f5d08 100644
--- a/src/main/services/team/TeamProvisioningService.ts
+++ b/src/main/services/team/TeamProvisioningService.ts
@@ -1,6 +1,6 @@
 /* eslint-disable no-param-reassign -- ProvisioningRun object is intentionally mutated as a state tracker throughout the provisioning lifecycle */
 import { ConfigManager } from '@main/services/infrastructure/ConfigManager';
-import { spawnCli } from '@main/utils/childProcess';
+import { killProcessTree, spawnCli } from '@main/utils/childProcess';
 import {
   encodePath,
   extractBaseDir,
@@ -1035,7 +1035,7 @@ export class TeamProvisioningService {
         void (async () => {
           const readyOnTimeout = await this.tryCompleteAfterTimeout(run);
           run.child?.stdin?.end();
-          run.child?.kill();
+          killProcessTree(run.child);
           if (readyOnTimeout) {
             return; // cleanupRun already called inside tryCompleteAfterTimeout
           }
@@ -1344,7 +1344,7 @@ export class TeamProvisioningService {
         void (async () => {
           const readyOnTimeout = await this.tryCompleteAfterTimeout(run);
           run.child?.stdin?.end();
-          run.child?.kill();
+          killProcessTree(run.child);
           if (readyOnTimeout) {
             return;
           }
@@ -1395,7 +1395,7 @@ export class TeamProvisioningService {
     run.cancelRequested = true;
     run.processKilled = true;
     run.child?.stdin?.end();
-    run.child?.kill();
+    killProcessTree(run.child);
     const progress = updateProgress(run, 'cancelled', 'Provisioning cancelled by user');
     run.onProgress(progress);
     this.cleanupRun(run);
@@ -1824,7 +1824,7 @@ export class TeamProvisioningService {
     run.processKilled = true;
     run.cancelRequested = true;
     run.child?.stdin?.end();
-    run.child?.kill();
+    killProcessTree(run.child);
     const progress = updateProgress(run, 'disconnected', 'Team stopped by user');
     run.onProgress(progress);
     this.cleanupRun(run);
@@ -1966,7 +1966,7 @@ export class TeamProvisioningService {
           // Kill the process on provisioning error
           run.processKilled = true;
           run.child?.stdin?.end();
-          run.child?.kill();
+          killProcessTree(run.child);
           this.cleanupRun(run);
         } else if (run.provisioningComplete) {
           // Post-provisioning error: process alive, waiting for input
@@ -2028,7 +2028,7 @@ export class TeamProvisioningService {
       run.onProgress(progress);
       run.processKilled = true;
       run.child?.stdin?.end();
-      run.child?.kill();
+      killProcessTree(run.child);
       this.cleanupRun(run);
       return;
     }
@@ -3137,7 +3137,7 @@ export class TeamProvisioningService {
       const stderrChunks: Buffer[] = [];
 
       const timeoutHandle = setTimeout(() => {
-        child.kill();
+        killProcessTree(child);
         reject(new Error(`Timeout running: claude ${args.join(' ')}`));
       }, timeoutMs);
 
diff --git a/src/main/utils/childProcess.ts b/src/main/utils/childProcess.ts
index a1f49e85..7a420ab2 100644
--- a/src/main/utils/childProcess.ts
+++ b/src/main/utils/childProcess.ts
@@ -1,4 +1,5 @@
 import {
+  type ChildProcess,
   exec,
   execFile,
   type ExecFileOptions,
@@ -6,6 +7,7 @@ import {
   spawn,
   type SpawnOptions,
 } from 'child_process';
+import path from 'path';
 
 /**
  * Promise wrapper for execFile that always returns { stdout, stderr }.
@@ -156,3 +158,41 @@ export function spawnCli(
     throw err;
   }
 }
+
+/**
+ * Kill a child process and its entire process tree.
+ *
+ * On Windows with `shell: true`, `child.kill()` only kills the intermediate
+ * `cmd.exe` shell, leaving the actual process (e.g. `claude.cmd`) orphaned.
+ * `taskkill /T /F /PID` recursively kills the entire process tree.
+ *
+ * On macOS/Linux, processes are killed directly (no shell wrapper), so
+ * the standard `child.kill(signal)` works correctly.
+ */
+export function killProcessTree(
+  child: ChildProcess | null | undefined,
+  signal?: NodeJS.Signals
+): void {
+  if (!child?.pid) {
+    // Process is null, never started, or already exited
+    return;
+  }
+
+  if (process.platform === 'win32') {
+    try {
+      const taskkillPath = path.join(
+        process.env.SystemRoot ?? 'C:\\Windows',
+        'System32',
+        'taskkill.exe'
+      );
+      execFile(taskkillPath, ['/T', '/F', '/PID', String(child.pid)], () => {
+        // Best-effort — ignore errors (process may have already exited)
+      });
+      return;
+    } catch {
+      // taskkill failed, fall through to standard kill
+    }
+  }
+
+  child.kill(signal);
+}