diff --git a/apps/bootstrap-installer/src-tauri/src/paths.rs b/apps/bootstrap-installer/src-tauri/src/paths.rs
index 0eec8ccd319db..3a7b1b0dbf5fe 100644
--- a/apps/bootstrap-installer/src-tauri/src/paths.rs
+++ b/apps/bootstrap-installer/src-tauri/src/paths.rs
@@ -98,6 +98,12 @@ pub fn update_in_progress_marker() -> PathBuf {
 /// that path), where copying onto ourselves would be a Windows sharing
 /// violation. Best-effort: a failure here must not fail the install, so the
 /// caller logs and continues.
+///
+/// NOTE: because of that no-op, a user's staged installer is only ever written
+/// by a full install/repair. Every later `--update` runs the ORIGINAL binary,
+/// so an installer-protocol change can strand the whole installed base on a
+/// binary that predates it (see `restage_from_checkout`, which repairs this
+/// from the freshly-updated checkout).
 pub fn copy_self_to_hermes_home() -> std::io::Result<()> {
     let src = std::env::current_exe()?;
     let dest = installer_dest();
diff --git a/apps/desktop/electron/main.ts b/apps/desktop/electron/main.ts
index 785a1dc96e203..e0d43be1f6231 100644
--- a/apps/desktop/electron/main.ts
+++ b/apps/desktop/electron/main.ts
@@ -201,7 +201,11 @@ import {
   sandboxPreflight
 } from './update-relaunch'
 import { isOfficialSshRemote, OFFICIAL_REPO_HTTPS_URL } from './update-remote'
-import { resolveStagedUpdaterBinary, spawnUpdaterProcess } from './updater-process'
+import {
+  resolveStagedUpdaterBinary,
+  spawnUpdaterProcess,
+  stagedUpdaterSupportsPrewrittenMarker
+} from './updater-process'
 import { formatBlockerMessage, formatProbeFailedMessage, scanVenvBlockers } from './venv-blocker-scan'
 import { fetchMarketplaceThemes, searchMarketplaceThemes } from './vscode-marketplace'
 import { createWakeIndicatorWindowController } from './wake-indicator-window'
@@ -3012,8 +3016,20 @@ async function applyUpdates(opts = {}) {
     // the venv. By writing the marker ourselves the renderer's
     // waitForUpdateToFinish() gate sees a live update and parks instead.
     // The updater overwrites this with its own PID later; same format.
-    if (Number.isInteger(child.pid)) {
+    //
+    // SKIPPED for pre-#74782 staged updaters: those have no self-PID
+    // exclusion, so they read this very marker as a foreign live owner and
+    // abort with "Another Hermes update is already running (PID <itself>)" —
+    // an unbreakable loop, because the update that would replace the stale
+    // binary is the one being refused. Losing the anti-respawn hardening is
+    // strictly better than never updating again, and the updater still writes
+    // its own marker moments later.
+    if (Number.isInteger(child.pid) && stagedUpdaterSupportsPrewrittenMarker(updater)) {
       writeUpdateMarker(HERMES_HOME, child.pid)
+    } else if (Number.isInteger(child.pid)) {
+      rememberLog(
+        `[updates] skipping marker pre-write: staged updater predates self-adopt (${updater}); it would refuse its own claim`
+      )
     }
 
     rememberLog(`[updates] launched updater: ${updater} ${updaterArgs.join(' ')}; exiting desktop to release venv shim`)
@@ -3100,9 +3116,15 @@ async function handOffWindowsBootstrapRecovery(reason) {
 
   // Same marker pre-write as applyUpdates — see comment there. The recovery
   // hand-off has the same window where the renderer can respawn a backend
-  // before the updater writes its own marker.
-  if (Number.isInteger(child.pid)) {
+  // before the updater writes its own marker, and the same stale-updater
+  // exclusion: a pre-#74782 binary would refuse its own pre-written claim and
+  // strand the very recovery meant to heal the install.
+  if (Number.isInteger(child.pid) && stagedUpdaterSupportsPrewrittenMarker(updater)) {
     writeUpdateMarker(HERMES_HOME, child.pid)
+  } else if (Number.isInteger(child.pid)) {
+    rememberLog(
+      `[bootstrap] skipping marker pre-write: staged updater predates self-adopt (${updater}); it would refuse its own claim`
+    )
   }
 
   rememberLog(
diff --git a/apps/desktop/electron/updater-process.test.ts b/apps/desktop/electron/updater-process.test.ts
index 96f48eb9ff016..e781fe3efa3ec 100644
--- a/apps/desktop/electron/updater-process.test.ts
+++ b/apps/desktop/electron/updater-process.test.ts
@@ -4,7 +4,65 @@ import path from 'node:path'
 
 import { test } from 'vitest'
 
-import { resolveStagedUpdaterBinary, spawnUpdaterProcess } from './updater-process'
+import {
+  MARKER_SELF_ADOPT_EPOCH_MS,
+  resolveStagedUpdaterBinary,
+  spawnUpdaterProcess,
+  stagedUpdaterSupportsPrewrittenMarker
+} from './updater-process'
+
+const DAY_MS = 24 * 60 * 60 * 1000
+
+test('stagedUpdaterSupportsPrewrittenMarker rejects installers predating the self-adopt fix', () => {
+  // The real-world trap: an installer staged at first install months ago, never
+  // refreshed because copy_self_to_hermes_home no-ops during --update.
+  assert.equal(
+    stagedUpdaterSupportsPrewrittenMarker('C:\\Hermes\\hermes-setup.exe', {
+      stagedMtimeMs: () => MARKER_SELF_ADOPT_EPOCH_MS - 60 * DAY_MS
+    }),
+    false
+  )
+})
+
+test('stagedUpdaterSupportsPrewrittenMarker accepts installers from the fix onward', () => {
+  assert.equal(
+    stagedUpdaterSupportsPrewrittenMarker('C:\\Hermes\\hermes-setup.exe', {
+      stagedMtimeMs: () => MARKER_SELF_ADOPT_EPOCH_MS
+    }),
+    true
+  )
+  assert.equal(
+    stagedUpdaterSupportsPrewrittenMarker('C:\\Hermes\\hermes-setup.exe', {
+      stagedMtimeMs: () => MARKER_SELF_ADOPT_EPOCH_MS + 30 * DAY_MS
+    }),
+    true
+  )
+})
+
+test('stagedUpdaterSupportsPrewrittenMarker treats an unreadable mtime as unsupported', () => {
+  // Bias toward the path that can always make progress: a skipped pre-write
+  // loses anti-respawn hardening, a wedged updater can never update again.
+  assert.equal(
+    stagedUpdaterSupportsPrewrittenMarker('C:\\Hermes\\hermes-setup.exe', {
+      stagedMtimeMs: () => null
+    }),
+    false
+  )
+})
+
+test('resolveStagedUpdaterBinary still returns a stale staged updater on Windows', () => {
+  // Staleness gates only the marker PRE-WRITE, never the hand-off itself:
+  // the stale binary is the only updater these users have, and it works fine
+  // once it is allowed to write its own claim.
+  assert.equal(
+    resolveStagedUpdaterBinary('C:\\Hermes', {
+      fileExists: () => true,
+      isWindows: true,
+      stagedMtimeMs: () => MARKER_SELF_ADOPT_EPOCH_MS - 60 * DAY_MS
+    }),
+    path.join('C:\\Hermes', 'hermes-setup.exe')
+  )
+})
 
 test('spawnUpdaterProcess hides the updater console and detaches the child on Windows', () => {
   const calls: Array<{ args: string[]; command: string; options: SpawnOptions }> = []
diff --git a/apps/desktop/electron/updater-process.ts b/apps/desktop/electron/updater-process.ts
index 56352da3e8534..97b1d9651afa8 100644
--- a/apps/desktop/electron/updater-process.ts
+++ b/apps/desktop/electron/updater-process.ts
@@ -12,8 +12,20 @@ export interface UpdaterChild {
 export interface ResolveStagedUpdaterBinaryDeps {
   isWindows?: boolean
   fileExists?: (candidate: string) => boolean
+  stagedMtimeMs?: (candidate: string) => number | null
 }
 
+/**
+ * Staged installers older than this have no self-PID exclusion in
+ * `UpdateMarkerGuard::acquire` and will refuse an update whose marker was
+ * pre-written on their behalf.
+ *
+ * The self-adopt fix landed in #74782 / 160586ff8 (2026-07-30 17:57 +0700).
+ * We compare against the start of 2026-07-31 UTC so the boundary is
+ * unambiguous for binaries staged that same day.
+ */
+export const MARKER_SELF_ADOPT_EPOCH_MS = Date.UTC(2026, 6, 31)
+
 function stagedFileExists(candidate: string): boolean {
   try {
     return statSync(candidate).isFile()
@@ -22,6 +34,14 @@ function stagedFileExists(candidate: string): boolean {
   }
 }
 
+function stagedFileMtimeMs(candidate: string): number | null {
+  try {
+    return statSync(candidate).mtimeMs
+  } catch {
+    return null
+  }
+}
+
 /**
  * Decide which staged installer binary — if any — may be handed an update.
  *
@@ -61,6 +81,37 @@ export function resolveStagedUpdaterBinary(
   return fileExists(candidate) ? candidate : null
 }
 
+/**
+ * True when the staged installer is new enough to survive a pre-written marker.
+ *
+ * `copy_self_to_hermes_home` deliberately no-ops during `--update`
+ * (apps/bootstrap-installer/src-tauri/src/paths.rs), so the binary staged by a
+ * user's ORIGINAL install orchestrates every later update — forever. Installers
+ * predating #74782 have no self-PID exclusion in `UpdateMarkerGuard::acquire`,
+ * so when the desktop pre-writes the marker naming that very updater, the
+ * updater reads its own claim as a foreign live owner and aborts with
+ * "Another Hermes update is already running (PID <itself>, started 1s ago)" —
+ * the observed infinite "Install didn't finish" loop. Skipping the pre-write
+ * for those binaries lets them acquire cleanly and run `hermes update`, which
+ * pulls the permanent fixes. See shouldPrewriteUpdateMarker.
+ *
+ * We cannot ask the binary its version without executing it, so use its mtime:
+ * the installer is written to HERMES_HOME at install/repair time, making mtime
+ * a faithful stamp of which installer generation produced it.
+ *
+ * Unreadable mtime counts as UNSUPPORTED — the pre-write is a best-effort
+ * hardening, while a wedged updater is unrecoverable, so we bias toward the
+ * path that can always make progress.
+ */
+export function stagedUpdaterSupportsPrewrittenMarker(
+  candidate: string,
+  deps: ResolveStagedUpdaterBinaryDeps = {}
+): boolean {
+  const mtimeMs = (deps.stagedMtimeMs ?? stagedFileMtimeMs)(candidate)
+
+  return typeof mtimeMs === 'number' && Number.isFinite(mtimeMs) && mtimeMs >= MARKER_SELF_ADOPT_EPOCH_MS
+}
+
 export interface SpawnUpdaterProcessDeps {
   isWindows?: boolean
   spawnProcess?: (command: string, args: string[], options: SpawnOptions) => UpdaterChild