diff --git a/config/scripts/ensure-native-runtime.mjs b/config/scripts/ensure-native-runtime.mjs
index fd1d0385cfb..d77dcf1f707 100644
--- a/config/scripts/ensure-native-runtime.mjs
+++ b/config/scripts/ensure-native-runtime.mjs
@@ -295,8 +295,8 @@ function loadNativeModule(moduleName) {
     return
   }
   if (moduleName === '@orca/windows-security') {
-    // Why: the package defers loading its .node addon until the first call.
-    require(moduleName).currentUserSid()
+    // Why: the addon loads on first call; the newest export also rejects a stale build that loads.
+    require(moduleName).clearStdHandleInheritance()
     return
   }
   if (moduleName === 'node-pty') {
diff --git a/config/scripts/ensure-native-runtime.test.mjs b/config/scripts/ensure-native-runtime.test.mjs
index 4514fab0eae..20ebbfab40f 100644
--- a/config/scripts/ensure-native-runtime.test.mjs
+++ b/config/scripts/ensure-native-runtime.test.mjs
@@ -423,7 +423,10 @@ function writeFakeWindowsRegistry(projectDir, { requiresMarker = false } = {}) {
   )
   const securityDir = join(projectDir, 'node_modules', '@orca', 'windows-security')
   mkdirSync(securityDir, { recursive: true })
-  writeFileSync(join(securityDir, 'index.js'), "exports.currentUserSid = () => 'S-1-5-18'\n")
+  writeFileSync(
+    join(securityDir, 'index.js'),
+    "exports.currentUserSid = () => 'S-1-5-18'; exports.clearStdHandleInheritance = () => []\n"
+  )
 }
 
 function writeNodePtyPatchFile(projectDir) {
diff --git a/config/scripts/pr-package-test-paths.mjs b/config/scripts/pr-package-test-paths.mjs
index 9a82fa1d3d7..1e6261e4cb4 100644
--- a/config/scripts/pr-package-test-paths.mjs
+++ b/config/scripts/pr-package-test-paths.mjs
@@ -95,6 +95,7 @@ export const WINDOWS_BOUNDARY_TESTS = [
   'src/main/orca-profiles/profile-index-store.test.ts',
   'src/main/startup/windows-install-dir-acl-repair.win32.test.ts',
   'src/main/startup/windows-app-data-path.test.ts',
+  'src/main/startup/windows-std-handle-inheritance.win32.test.ts',
   'src/main/runtime/repo-worktree-admin-fingerprint.test.ts',
   'src/main/runtime/worktree-scan-admin-fingerprint-gate.test.ts',
   'src/shared/secure-file-fsync-flags.test.ts',
diff --git a/config/scripts/rebuild-native-deps-test-fixtures.mjs b/config/scripts/rebuild-native-deps-test-fixtures.mjs
index 1d346bfd674..4066d0c62ac 100644
--- a/config/scripts/rebuild-native-deps-test-fixtures.mjs
+++ b/config/scripts/rebuild-native-deps-test-fixtures.mjs
@@ -400,7 +400,10 @@ export function writeFakeWindowsRegistry(projectDir) {
 export function writeFakeWindowsSecurity(projectDir) {
   const securityDir = join(projectDir, 'node_modules', '@orca', 'windows-security')
   mkdirSync(securityDir, { recursive: true })
-  writeFileSync(join(securityDir, 'index.js'), "exports.currentUserSid = () => 'S-1-5-18'\n")
+  writeFileSync(
+    join(securityDir, 'index.js'),
+    "exports.currentUserSid = () => 'S-1-5-18'; exports.clearStdHandleInheritance = () => []\n"
+  )
 }
 
 // Healthy patched addon must report CreationTime; no exports represents upstream tarball prebuild to the probe.
diff --git a/config/scripts/rebuild-native-deps.mjs b/config/scripts/rebuild-native-deps.mjs
index 3f974b5a28d..36c23e9ef98 100644
--- a/config/scripts/rebuild-native-deps.mjs
+++ b/config/scripts/rebuild-native-deps.mjs
@@ -577,8 +577,8 @@ function loadNativeModule(moduleName) {
     return
   }
   if (moduleName === '@orca/windows-security') {
-    // Why: the package defers loading its .node addon until the first call.
-    projectRequire(moduleName).currentUserSid()
+    // Why: the addon loads on first call; the newest export also rejects a stale build that loads.
+    projectRequire(moduleName).clearStdHandleInheritance()
     return
   }
   if (moduleName === 'node-pty') {
diff --git a/native/windows-security/index.d.ts b/native/windows-security/index.d.ts
index 298ff1a8f4e..c64267337de 100644
--- a/native/windows-security/index.d.ts
+++ b/native/windows-security/index.d.ts
@@ -51,3 +51,11 @@ export declare function grantAccessAsync(
   accessMask: number,
   options: GrantAccessOptions
 ): Promise<void>
+
+export type StdHandleInheritanceFailure = { stream: 'stdin' | 'stdout' | 'stderr'; code: number }
+
+/**
+ * Makes the process's std handles non-inheritable, skipping absent ones. Never throws; returns the
+ * handles SetHandleInformation rejected (e.g. a legacy console pseudo-handle) with their Win32 code.
+ */
+export declare function clearStdHandleInheritance(): StdHandleInheritanceFailure[]
diff --git a/native/windows-security/index.js b/native/windows-security/index.js
index d96c2ecfe01..b7cc64f82bb 100644
--- a/native/windows-security/index.js
+++ b/native/windows-security/index.js
@@ -17,5 +17,6 @@ module.exports = {
   createFileWithDacl: (path, sddl, data) => getAddon().createFileWithDacl(path, sddl, data),
   grantAccess: (path, sid, mask, options) => getAddon().grantAccess(path, sid, mask, options),
   grantAccessAsync: (path, sid, mask, options) =>
-    getAddon().grantAccessAsync(path, sid, mask, options)
+    getAddon().grantAccessAsync(path, sid, mask, options),
+  clearStdHandleInheritance: () => getAddon().clearStdHandleInheritance()
 }
diff --git a/native/windows-security/src/addon.cc b/native/windows-security/src/addon.cc
index 76edd13bffd..649d29628c1 100644
--- a/native/windows-security/src/addon.cc
+++ b/native/windows-security/src/addon.cc
@@ -384,6 +384,34 @@ Napi::Value GrantAccessAsync(const Napi::CallbackInfo& info) {
   return promise;
 }
 
+// Clear HANDLE_FLAG_INHERIT on the std handles so a spawn with bInheritHandles=TRUE can't leak them
+// to a long-lived child; libuv duplicates an inheritable copy for an explicit stdio 'inherit'.
+// Returns only failures, as [{ stream, code }]; absent handles are skipped.
+Napi::Value ClearStdHandleInheritance(const Napi::CallbackInfo& info) {
+  auto env = info.Env();
+  struct Stream {
+    DWORD id;
+    const char* name;
+  };
+  const Stream streams[] = {{STD_INPUT_HANDLE, "stdin"},
+                            {STD_OUTPUT_HANDLE, "stdout"},
+                            {STD_ERROR_HANDLE, "stderr"}};
+  auto failures = Napi::Array::New(env);
+  for (const auto& stream : streams) {
+    HANDLE handle = GetStdHandle(stream.id);
+    if (handle == nullptr || handle == INVALID_HANDLE_VALUE) {
+      continue;
+    }
+    if (!SetHandleInformation(handle, HANDLE_FLAG_INHERIT, 0)) {
+      auto failure = Napi::Object::New(env);
+      failure.Set("stream", stream.name);
+      failure.Set("code", static_cast<double>(GetLastError()));
+      failures.Set(failures.Length(), failure);
+    }
+  }
+  return failures;
+}
+
 }  // namespace
 
 Napi::Object Init(Napi::Env env, Napi::Object exports) {
@@ -394,6 +422,7 @@ Napi::Object Init(Napi::Env env, Napi::Object exports) {
   exports.Set("createFileWithDacl", Napi::Function::New(env, CreateFileWithDaclJs));
   exports.Set("grantAccess", Napi::Function::New(env, GrantAccessJs));
   exports.Set("grantAccessAsync", Napi::Function::New(env, GrantAccessAsync));
+  exports.Set("clearStdHandleInheritance", Napi::Function::New(env, ClearStdHandleInheritance));
   return exports;
 }
 
diff --git a/src/main/index.ts b/src/main/index.ts
index c153fe7d745..0cd411e0582 100644
--- a/src/main/index.ts
+++ b/src/main/index.ts
@@ -40,6 +40,7 @@ import { wslHostsServing } from './wsl/wsl-host-gate'
 import { configureWslHostsGateFromDisk } from './wsl/wsl-host-gate-startup'
 import { ignoreInheritedWslHostsGateState } from '../shared/wsl-host-internal-gate'
 import { registerOrcaProtocolClient } from './startup/orca-protocol-registration'
+import { clearWindowsStdHandleInheritance } from './startup/windows-std-handle-inheritance'
 
 function openMainWindow(options: { revealOnDidFinishLoad?: boolean } = {}): BrowserWindow {
   return openMainWindowController(options)
@@ -107,6 +108,8 @@ const handleMacAppActivation = createMacAppActivationHandler({
   requestActivation: requestDesktopActivation
 })
 
+// Before anything spawns: no child may inherit Orca's std handles.
+clearWindowsStdHandleInheritance()
 // A relaunch or installer inherits the parent's published WSL gate state; this process recomputes.
 ignoreInheritedWslHostsGateState()
 // The uninstaller's holder release and hook removal run instead of the app, never alongside it.
diff --git a/src/main/startup/windows-install-dir-package-acl-grant.test.ts b/src/main/startup/windows-install-dir-package-acl-grant.test.ts
index 88a1370cec4..d170d08cf5a 100644
--- a/src/main/startup/windows-install-dir-package-acl-grant.test.ts
+++ b/src/main/startup/windows-install-dir-package-acl-grant.test.ts
@@ -42,6 +42,7 @@ function installFakeAddon(
     setDaclSddlAsync: unexpected,
     createFileWithDacl: unexpected,
     grantAccess: unexpected,
+    clearStdHandleInheritance: unexpected,
     grantAccessAsync: async (path, sid, accessMask, options) => {
       calls.push({ path: plain(path), sid, accessMask, options })
       if (fail(plain(path))) {
@@ -189,6 +190,7 @@ describe('install-dir package grant passes', () => {
         setDaclSddlAsync: unexpected,
         createFileWithDacl: unexpected,
         grantAccess: unexpected,
+        clearStdHandleInheritance: unexpected,
         grantAccessAsync: async (path) => {
           seen.push(path)
         }
diff --git a/src/main/startup/windows-std-handle-inheritance.test.ts b/src/main/startup/windows-std-handle-inheritance.test.ts
new file mode 100644
index 00000000000..e4d01492384
--- /dev/null
+++ b/src/main/startup/windows-std-handle-inheritance.test.ts
@@ -0,0 +1,69 @@
+import { afterEach, describe, expect, it, vi } from 'vitest'
+
+const { loadWindowsSecurity } = vi.hoisted(() => ({ loadWindowsSecurity: vi.fn() }))
+vi.mock('../../shared/windows-security-addon', () => ({ loadWindowsSecurity }))
+
+import { clearWindowsStdHandleInheritance } from './windows-std-handle-inheritance'
+
+function addonWith(clearStdHandleInheritance: () => unknown) {
+  return { userSid: 'S-1-5-18', addon: { clearStdHandleInheritance } }
+}
+
+describe('clearWindowsStdHandleInheritance', () => {
+  afterEach(() => {
+    vi.restoreAllMocks()
+    loadWindowsSecurity.mockReset()
+  })
+
+  it('is a no-op off Windows', () => {
+    clearWindowsStdHandleInheritance('darwin')
+    clearWindowsStdHandleInheritance('linux')
+
+    expect(loadWindowsSecurity).not.toHaveBeenCalled()
+  })
+
+  it('clears the std handles through the addon on Windows', () => {
+    const clear = vi.fn(() => [])
+    loadWindowsSecurity.mockReturnValue(addonWith(clear))
+    const warn = vi.spyOn(console, 'warn').mockImplementation(() => {})
+
+    clearWindowsStdHandleInheritance('win32')
+
+    expect(clear).toHaveBeenCalledOnce()
+    expect(warn).not.toHaveBeenCalled()
+  })
+
+  it('logs each handle the addon could not clear', () => {
+    loadWindowsSecurity.mockReturnValue(addonWith(() => [{ stream: 'stdout', code: 6 }]))
+    const warn = vi.spyOn(console, 'warn').mockImplementation(() => {})
+
+    clearWindowsStdHandleInheritance('win32')
+
+    expect(warn).toHaveBeenCalledWith('[startup] stdout stays inheritable; Win32 error 6')
+  })
+
+  it('logs instead of throwing when the addon is unavailable', () => {
+    loadWindowsSecurity.mockReturnValue({ error: 'missing binary' })
+    const warn = vi.spyOn(console, 'warn').mockImplementation(() => {})
+
+    expect(() => clearWindowsStdHandleInheritance('win32')).not.toThrow()
+    expect(warn).toHaveBeenCalledWith(
+      '[startup] std handles stay inheritable; addon unavailable: missing binary'
+    )
+  })
+
+  it('logs instead of throwing when the addon call throws, e.g. a stale binary', () => {
+    loadWindowsSecurity.mockReturnValue(
+      addonWith(() => {
+        throw new TypeError('clearStdHandleInheritance is not a function')
+      })
+    )
+    const warn = vi.spyOn(console, 'warn').mockImplementation(() => {})
+
+    expect(() => clearWindowsStdHandleInheritance('win32')).not.toThrow()
+    expect(warn).toHaveBeenCalledWith(
+      '[startup] std handles stay inheritable:',
+      expect.any(TypeError)
+    )
+  })
+})
diff --git a/src/main/startup/windows-std-handle-inheritance.ts b/src/main/startup/windows-std-handle-inheritance.ts
new file mode 100644
index 00000000000..224068740f3
--- /dev/null
+++ b/src/main/startup/windows-std-handle-inheritance.ts
@@ -0,0 +1,23 @@
+import { loadWindowsSecurity } from '../../shared/windows-security-addon'
+
+/** libuv spawns with bInheritHandles=TRUE, so an inheritable std handle reaches every child, and a
+ * long-lived one (the WSL holder, the daemon) keeps a launcher's pipe open after Orca exits. */
+export function clearWindowsStdHandleInheritance(
+  platform: NodeJS.Platform = process.platform
+): void {
+  if (platform !== 'win32') {
+    return
+  }
+  try {
+    const security = loadWindowsSecurity()
+    if ('error' in security) {
+      console.warn(`[startup] std handles stay inheritable; addon unavailable: ${security.error}`)
+      return
+    }
+    for (const failure of security.addon.clearStdHandleInheritance()) {
+      console.warn(`[startup] ${failure.stream} stays inheritable; Win32 error ${failure.code}`)
+    }
+  } catch (error) {
+    console.warn('[startup] std handles stay inheritable:', error)
+  }
+}
diff --git a/src/main/startup/windows-std-handle-inheritance.win32.test.ts b/src/main/startup/windows-std-handle-inheritance.win32.test.ts
new file mode 100644
index 00000000000..4f940c8d516
--- /dev/null
+++ b/src/main/startup/windows-std-handle-inheritance.win32.test.ts
@@ -0,0 +1,103 @@
+import { once } from 'node:events'
+import { mkdtempSync, readFileSync, rmSync, writeFileSync } from 'node:fs'
+import { createRequire } from 'node:module'
+import { tmpdir } from 'node:os'
+import { join, resolve } from 'node:path'
+import { afterAll, describe, expect, it } from 'vitest'
+import { spawnProcess } from '@orca/process-host'
+
+const describeOnWindows = process.platform === 'win32' ? describe : describe.skip
+const ADDON = resolve(__dirname, '..', '..', '..', 'native', 'windows-security', 'index.js')
+const root = mkdtempSync(join(tmpdir(), 'orca-std-handles-'))
+const entry = join(root, 'main.cjs')
+
+/** Optionally clears, writes through a stdio:'inherit' grandchild, then leaves a detached
+ * stdio:'ignore' holder behind, like the WSL holder or the daemon. */
+writeFileSync(
+  entry,
+  `
+const { spawn, spawnSync } = require('node:child_process')
+const { writeFileSync } = require('node:fs')
+const [mode, holderMs, pidFile] = process.argv.slice(-3)
+if (mode === 'clear') {
+  const failures = require(${JSON.stringify(ADDON)}).clearStdHandleInheritance()
+  if (failures.length > 0) { writeFileSync(pidFile, JSON.stringify(failures)); process.exit(3) }
+}
+const env = { ...process.env, ELECTRON_RUN_AS_NODE: '1' }
+spawnSync(process.execPath, ['-e', 'process.stdout.write("inherited-output\\\\n")'], { stdio: 'inherit', env, windowsHide: true })
+const holder = spawn(process.execPath, ['-e', 'setTimeout(() => {}, ' + holderMs + ')'], { stdio: 'ignore', detached: true, env, windowsHide: true })
+holder.unref()
+writeFileSync(pidFile, String(holder.pid))
+if (process.type === 'browser') require('electron').app.exit(0)
+`
+)
+
+afterAll(() => rmSync(root, { recursive: true, force: true }))
+
+function isAlive(pid: number): boolean {
+  try {
+    process.kill(pid, 0)
+    return true
+  } catch {
+    return false
+  }
+}
+
+/** Electron main is Orca's real shape: it keeps std handles inheritable (kEnableStdioInheritance),
+ * where plain Node clears them itself at startup. */
+async function runChild(host: 'electron' | 'node', mode: 'clear' | 'keep', holderMs: number) {
+  const electron: unknown = createRequire(import.meta.url)('electron')
+  if (typeof electron !== 'string') {
+    throw new Error('Electron executable is unavailable')
+  }
+  const env: NodeJS.ProcessEnv = { ...process.env, ORCA_BACKGROUND_LAUNCH: '1' }
+  delete env.ELECTRON_RUN_AS_NODE
+  const pidFile = join(root, `${host}-${mode}.pid`)
+  const child = spawnProcess({
+    program: host === 'electron' ? electron : process.execPath,
+    args: [entry, mode, String(holderMs), pidFile],
+    env,
+    stdio: ['ignore', 'pipe', 'pipe']
+  })
+  let output = ''
+  child.stdout?.on('data', (chunk) => (output += chunk))
+  child.stderr?.on('data', (chunk) => (output += chunk))
+  const [code] = await once(child, 'close', { signal: AbortSignal.timeout(holderMs + 30_000) })
+  const pidText = readFileSync(pidFile, 'utf8')
+  const holderPid = Number(pidText)
+  const holderAliveAtClose = isAlive(holderPid)
+  if (holderAliveAtClose) {
+    process.kill(holderPid)
+  }
+  return { code, output, pidText, holderAliveAtClose }
+}
+
+describeOnWindows('clearing std handle inheritance', () => {
+  // A regression pins the pipe for the 60 s holder; fail on the assertion, not the 5 s default.
+  it('keeps stdio inherit output and frees the pipe while a detached holder lives', async () => {
+    const run = await runChild('electron', 'clear', 60_000)
+
+    expect(run.code, run.output).toBe(0)
+    expect(run.pidText).toMatch(/^\d+$/)
+    expect(run.output).toContain('inherited-output')
+    expect(run.holderAliveAtClose).toBe(true)
+  }, 90_000)
+
+  // Cold Electron start on a CI runner plus the 3 s holder exceeds the 5 s default.
+  it('without it, Electron main lets the holder keep the pipe open until it exits', async () => {
+    const run = await runChild('electron', 'keep', 3_000)
+
+    expect(run.code, run.output).toBe(0)
+    expect(run.output).toContain('inherited-output')
+    expect(run.holderAliveAtClose).toBe(false)
+  }, 60_000)
+
+  // A regression pins the pipe for the 60 s holder; fail on the assertion, not the 5 s default.
+  it('plain Node already clears its own std handles, so it is no model for Orca', async () => {
+    const run = await runChild('node', 'keep', 60_000)
+
+    expect(run.code, run.output).toBe(0)
+    expect(run.output).toContain('inherited-output')
+    expect(run.holderAliveAtClose).toBe(true)
+  }, 90_000)
+})
diff --git a/src/shared/windows-security-addon.test-fixture.ts b/src/shared/windows-security-addon.test-fixture.ts
index 44ad6329a6b..3f4ee1978e5 100644
--- a/src/shared/windows-security-addon.test-fixture.ts
+++ b/src/shared/windows-security-addon.test-fixture.ts
@@ -106,6 +106,7 @@ export function createFakeWindowsSecurity(): FakeWindowsSecurity {
     callsFor: (op, path) =>
       fake.calls.filter((call) => call.op === op && (path === undefined || call.path === path)),
     currentUserSid: () => FAKE_USER_SID,
+    clearStdHandleInheritance: () => [],
     getDaclAces: (addonPath) => {
       const path = record('get', addonPath)
       return daclFromSddl(fake.dacls.get(path) ?? INHERITED_SDDL)
diff --git a/src/shared/windows-security-addon.ts b/src/shared/windows-security-addon.ts
index 055e731991c..4d41faedfb3 100644
--- a/src/shared/windows-security-addon.ts
+++ b/src/shared/windows-security-addon.ts
@@ -4,7 +4,12 @@ import { basename, isAbsolute, join, relative, toNamespacedPath } from 'node:pat
 import type * as WindowsSecurityModule from '@orca/windows-security'
 import { ORCAD_WINDOWS_SECURITY_FILENAME } from './orcad-artifacts'
 
-export type { GrantAccessOptions, WindowsAce, WindowsDacl } from '@orca/windows-security'
+export type {
+  GrantAccessOptions,
+  StdHandleInheritanceFailure,
+  WindowsAce,
+  WindowsDacl
+} from '@orca/windows-security'
 export type WindowsSecurityAddon = typeof WindowsSecurityModule
 
 /** The addon (every path namespaced, async writes ordered per path) and the token's user SID. */
@@ -105,7 +110,8 @@ function prepare(raw: WindowsSecurityAddon): WindowsSecurity {
       grantAccess: (path, sid, mask, options) =>
         raw.grantAccess(toNamespacedPath(path), sid, mask, options),
       grantAccessAsync: (path, sid, mask, options) =>
-        inPathOrder(path, (namespaced) => raw.grantAccessAsync(namespaced, sid, mask, options))
+        inPathOrder(path, (namespaced) => raw.grantAccessAsync(namespaced, sid, mask, options)),
+      clearStdHandleInheritance: () => raw.clearStdHandleInheritance()
     }
   }
 }