From 225b28199a6f23adfebca40c9843c2dc0174ef2d Mon Sep 17 00:00:00 2001
From: Neil <4138956+nwparker@users.noreply.github.com>
Date: Sun, 30 Aug 2026 23:04:17 -0700
Subject: [PATCH] perf(renderer): avoid remote PTY selector allocations
 (#17454)

---
 .../src/lib/tab-agent-remote-pty-selector.ts  | 23 +++++++
 .../use-tab-agent-remote-pty-selector.test.ts | 60 +++++++++++++++++++
 src/renderer/src/lib/use-tab-agent.ts         | 16 +++--
 3 files changed, 90 insertions(+), 9 deletions(-)
 create mode 100644 src/renderer/src/lib/tab-agent-remote-pty-selector.ts
 create mode 100644 src/renderer/src/lib/use-tab-agent-remote-pty-selector.test.ts

diff --git a/src/renderer/src/lib/tab-agent-remote-pty-selector.ts b/src/renderer/src/lib/tab-agent-remote-pty-selector.ts
new file mode 100644
index 00000000000..69091611d47
--- /dev/null
+++ b/src/renderer/src/lib/tab-agent-remote-pty-selector.ts
@@ -0,0 +1,23 @@
+import { parseRemoteRuntimePtyId } from '@/runtime/runtime-terminal-stream'
+
+/** Checks both PTY projections without allocating a dedupe set on each store notification. */
+export function hasRemoteRuntimePtyForTab(
+  tabPtyIds: readonly string[] | undefined,
+  leafPtyIdsById: Readonly<Record<string, string>> | undefined
+): boolean {
+  if (tabPtyIds?.some((ptyId) => parseRemoteRuntimePtyId(ptyId) !== null)) {
+    return true
+  }
+  if (!leafPtyIdsById) {
+    return false
+  }
+  for (const leafId in leafPtyIdsById) {
+    if (
+      Object.hasOwn(leafPtyIdsById, leafId) &&
+      parseRemoteRuntimePtyId(leafPtyIdsById[leafId]!) !== null
+    ) {
+      return true
+    }
+  }
+  return false
+}
diff --git a/src/renderer/src/lib/use-tab-agent-remote-pty-selector.test.ts b/src/renderer/src/lib/use-tab-agent-remote-pty-selector.test.ts
new file mode 100644
index 00000000000..8f7c870fc91
--- /dev/null
+++ b/src/renderer/src/lib/use-tab-agent-remote-pty-selector.test.ts
@@ -0,0 +1,60 @@
+import { describe, expect, it, vi } from 'vitest'
+import { hasRemoteRuntimePtyForTab } from './tab-agent-remote-pty-selector'
+
+const REMOTE_PTY = 'remote:environment-1@@terminal-1'
+
+describe('hasRemoteRuntimePtyForTab', () => {
+  it('short-circuits on a tab-level remote PTY', () => {
+    let leafReads = 0
+    const leafPtyIdsById = new Proxy(
+      { leaf: REMOTE_PTY },
+      {
+        ownKeys: () => {
+          leafReads += 1
+          return ['leaf']
+        }
+      }
+    )
+
+    expect(hasRemoteRuntimePtyForTab([REMOTE_PTY], leafPtyIdsById)).toBe(true)
+    expect(leafReads).toBe(0)
+  })
+
+  it('finds a remote PTY that is present only in the layout projection', () => {
+    expect(
+      hasRemoteRuntimePtyForTab(['local-pty'], { first: 'local-pty', second: REMOTE_PTY })
+    ).toBe(true)
+  })
+
+  it('ignores inherited layout properties like Object.values did', () => {
+    const inherited = { inherited: REMOTE_PTY }
+    const leafPtyIdsById = Object.create(inherited) as Record<string, string>
+    leafPtyIdsById.local = 'local-pty'
+
+    expect(hasRemoteRuntimePtyForTab(['local-pty'], leafPtyIdsById)).toBe(false)
+  })
+
+  it('avoids transient Set and Object.values allocations across repeated checks', () => {
+    const originalSet = globalThis.Set
+    const valuesSpy = vi.spyOn(Object, 'values').mockImplementation(() => {
+      throw new Error('unexpected Object.values allocation')
+    })
+    vi.stubGlobal(
+      'Set',
+      class UnexpectedSet {
+        constructor() {
+          throw new Error('unexpected Set allocation')
+        }
+      }
+    )
+
+    try {
+      for (let check = 0; check < 1_000; check += 1) {
+        expect(hasRemoteRuntimePtyForTab(['local-pty'], { first: 'local-pty-2' })).toBe(false)
+      }
+    } finally {
+      valuesSpy.mockRestore()
+      vi.stubGlobal('Set', originalSet)
+    }
+  })
+})
diff --git a/src/renderer/src/lib/use-tab-agent.ts b/src/renderer/src/lib/use-tab-agent.ts
index fef059ad616..21c00f4cc37 100644
--- a/src/renderer/src/lib/use-tab-agent.ts
+++ b/src/renderer/src/lib/use-tab-agent.ts
@@ -2,7 +2,7 @@ import { useEffect, useRef, useState } from 'react'
 import { useAppStore } from '@/store'
 import { isShellProcess } from '../../../shared/agent-detection'
 import { worktreeUsesRemoteConnection } from '@/store/terminals/terminal-workspace-routing'
-import { parseRemoteRuntimePtyId } from '@/runtime/runtime-terminal-stream'
+import { hasRemoteRuntimePtyForTab } from './tab-agent-remote-pty-selector'
 import { isTerminalLeafId, makePaneKey } from '../../../shared/stable-pane-id'
 import {
   resolveFocusedCompletedTabAgent,
@@ -254,14 +254,12 @@ export function useTabAgent(tab: TerminalTab): TuiAgent | null {
     }
     return (s.ptyIdsByTabId[tab.id] ?? []).length <= 1
   })
-  const hasRemoteRuntimePty = useAppStore((s) => {
-    const layout = s.terminalLayoutsByTabId[tab.id]
-    const ptyIds = new Set(s.ptyIdsByTabId[tab.id] ?? [])
-    for (const ptyId of Object.values(layout?.ptyIdsByLeafId ?? {})) {
-      ptyIds.add(ptyId)
-    }
-    return [...ptyIds].some((ptyId) => parseRemoteRuntimePtyId(ptyId) !== null)
-  })
+  const hasRemoteRuntimePty = useAppStore((s) =>
+    hasRemoteRuntimePtyForTab(
+      s.ptyIdsByTabId[tab.id],
+      s.terminalLayoutsByTabId[tab.id]?.ptyIdsByLeafId
+    )
+  )
   const isRemoteWorktree = useAppStore((s) => worktreeUsesRemoteConnection(s, tab.worktreeId))
   const isRemoteLike = isRemoteWorktree || hasRemoteRuntimePty