diff --git a/src/main/providers/local-pty-provider-shutdown.test.ts b/src/main/providers/local-pty-provider-shutdown.test.ts
index cccede7186b..950a7e9cbae 100644
--- a/src/main/providers/local-pty-provider-shutdown.test.ts
+++ b/src/main/providers/local-pty-provider-shutdown.test.ts
@@ -566,6 +566,20 @@ describe('LocalPtyProvider', () => {
       expect(list).toHaveLength(0)
     })
 
+    it('force-kills an OMP PTY root during app quit', async () => {
+      const killSpy = vi.fn()
+      spawnMock.mockReturnValue({
+        ...mockProc,
+        kill: killSpy
+      })
+
+      await provider.spawn({ cols: 80, rows: 24, launchAgent: 'omp' })
+
+      provider.killAll()
+
+      expect(killSpy).toHaveBeenCalledWith('SIGKILL')
+    })
+
     it('does not destroy after intentional Windows orphan kills', async () => {
       Object.defineProperty(process, 'platform', { configurable: true, value: 'win32' })
       const destroySpy = vi.fn()
diff --git a/src/main/providers/local-pty-termination.ts b/src/main/providers/local-pty-termination.ts
index 7a19e9d7326..426a7aad346 100644
--- a/src/main/providers/local-pty-termination.ts
+++ b/src/main/providers/local-pty-termination.ts
@@ -243,7 +243,13 @@ export function killAllLocalPtys(): void {
     disposePtyExitListener(id)
     if (!(process.platform === 'win32' && ptyTerminationMode.has(id))) {
       try {
-        proc.kill()
+        if (ptyAgentSessionIds.has(id) && process.platform !== 'win32') {
+          // App quit is synchronous, so sweep attached agent process groups before
+          // releasing node-pty; otherwise OMP workers can outlive the foreground PTY.
+          forceKillPosixPtyProcessGroups(proc.pid, () => proc.kill('SIGKILL'))
+        } else {
+          proc.kill()
+        }
       } catch {
         /* Process may already be dead. */
       }