From c777bb19bd580640b2d4eb32ef055063efb5b030 Mon Sep 17 00:00:00 2001
From: Brennan Benson <79079362+brennanb2025@users.noreply.github.com>
Date: Sun, 16 Aug 2026 20:50:32 -0700
Subject: [PATCH] fix(ssh): require matching PTY exit incarnation

---
 .../ssh-pty-provider-exit-race.test.ts        | 41 +++++++++++++++++++
 src/main/providers/ssh-pty-spawn-exit-race.ts |  4 +-
 2 files changed, 42 insertions(+), 3 deletions(-)

diff --git a/src/main/providers/ssh-pty-provider-exit-race.test.ts b/src/main/providers/ssh-pty-provider-exit-race.test.ts
index 22a19985d21..89b48042f84 100644
--- a/src/main/providers/ssh-pty-provider-exit-race.test.ts
+++ b/src/main/providers/ssh-pty-provider-exit-race.test.ts
@@ -130,6 +130,47 @@ it('rejects an SSH reattach whose matching exit shares the attach reply batch',
   })
 })
 
+it('does not classify a legacy exit as current while reattach resolves its incarnation', async () => {
+  const mux = {
+    request: vi.fn(),
+    notify: vi.fn(),
+    onNotification: vi.fn(),
+    dispose: vi.fn(),
+    isDisposed: vi.fn().mockReturnValue(false)
+  }
+  const provider = new SshPtyProvider('conn-1', mux as never)
+  let resolveAttach: (() => void) | undefined
+  mux.request.mockImplementation((method: string, _params, options) => {
+    if (method !== 'pty.attach') {
+      return Promise.resolve(undefined)
+    }
+    return new Promise((resolve) => {
+      resolveAttach = () => {
+        const result = { incarnationId: 'incarnation-current' }
+        options?.beforeResolve?.(result)
+        resolve(result)
+      }
+    })
+  })
+
+  const spawn = provider.spawn({
+    cols: 80,
+    rows: 24,
+    sessionId: 'ssh:conn-1@@pty-existing'
+  })
+  await vi.waitFor(() => expect(resolveAttach).toBeTypeOf('function'))
+  const notify = mux.onNotification.mock.calls[0]?.[0]
+  notify?.('pty.exit', { id: 'pty-existing', code: 0 })
+  resolveAttach?.()
+
+  await expect(spawn).resolves.toMatchObject({
+    id: 'ssh:conn-1@@pty-existing',
+    incarnationId: 'incarnation-current',
+    isReattach: true
+  })
+  await expect(provider.probePtyLiveness('ssh:conn-1@@pty-existing')).resolves.toBe(true)
+})
+
 it('returns a provisional source activation lease to reconnect authority', async () => {
   const mux = {
     request: vi.fn(),
diff --git a/src/main/providers/ssh-pty-spawn-exit-race.ts b/src/main/providers/ssh-pty-spawn-exit-race.ts
index 0658e3e23eb..a7c2dd51e76 100644
--- a/src/main/providers/ssh-pty-spawn-exit-race.ts
+++ b/src/main/providers/ssh-pty-spawn-exit-race.ts
@@ -29,9 +29,7 @@ export class SshPtySpawnExitRaceTracker {
     return operation.exits.some(
       (exit) =>
         exit.relayPtyId === result.id &&
-        (!exit.incarnationId ||
-          !result.incarnationId ||
-          exit.incarnationId === result.incarnationId)
+        (!result.incarnationId || exit.incarnationId === result.incarnationId)
     )
   }