diff --git a/electron/build/installer-recovery.nsh b/electron/build/installer-recovery.nsh
index f5dbd123..778235d2 100644
--- a/electron/build/installer-recovery.nsh
+++ b/electron/build/installer-recovery.nsh
@@ -79,8 +79,18 @@
   ; the install still completes; user just pays the cold-start tax on
   ; first launch, same as before this macro existed.
 
-  nsExec::Exec '"$INSTDIR\OpenSwarm.exe" --prewarm'
-  Pop $0  ; discard exit code; prewarm is best-effort
+  ; Skip prewarm on SILENT installs. CI's installer verification AND production
+  ; auto-updates both run the installer with /S, and nsExec::Exec is synchronous
+  ; with no upper bound - launching the freshly-extracted, not-yet-signed
+  ; OpenSwarm.exe (which loads python.exe + node.exe) provokes a cold Windows
+  ; Defender scan that can stall the silent install for minutes (it hung the CI
+  ; installer check, and would do the same to a user's auto-update). Interactive
+  ; first-time installs, where the cold-start win actually lands, still prewarm.
+  ${If} ${Silent}
+  ${Else}
+    nsExec::Exec '"$INSTDIR\OpenSwarm.exe" --prewarm'
+    Pop $0  ; discard exit code; prewarm is best-effort
+  ${EndIf}
 !macroend
 
 !macro customRemoveFiles
diff --git a/scripts/ci/verify-installer.js b/scripts/ci/verify-installer.js
index 6c0d91b3..683e7d86 100644
--- a/scripts/ci/verify-installer.js
+++ b/scripts/ci/verify-installer.js
@@ -99,15 +99,24 @@ function runDestructive(setup) {
   }
   process.stdout.write('\n[destructive] installing silently...\n');
   killRunning();
-  const inst = spawnSync(setup, ['/S'], { stdio: 'inherit' });
-  if (inst.status !== 0 && inst.status !== null) bad(`Setup.exe /S exited ${inst.status}`);
-  // oneClick installer returns before files settle; wait for the exe to appear.
-  const deadline = Date.now() + 120000;
-  while (Date.now() < deadline && !exists(path.join(INSTALL_DIR, 'OpenSwarm.exe'))) { execSync('powershell -NoProfile -Command "Start-Sleep -Milliseconds 1000"'); }
+  const installedExe = path.join(INSTALL_DIR, 'OpenSwarm.exe');
+  // Blocking: spawnSync returns only once the installer has fully finished
+  // (files + registry uninstall entry + shortcuts are all written, the last of
+  // which assertInstalled checks). The timeout is the safety net: the silent
+  // path now skips the unbounded --prewarm step (see installer-recovery.nsh), so
+  // a clean extract finishes well inside this, but if a future installer change
+  // reintroduces a synchronous stall this fails the gate in minutes instead of
+  // hanging the whole job until it is force-cancelled.
+  const inst = spawnSync(setup, ['/S'], { stdio: 'inherit', timeout: 300000 });
+  if (inst.error) bad(`Setup.exe /S did not complete: ${inst.error.message}`);
+  else if (inst.status !== 0 && inst.status !== null) bad(`Setup.exe /S exited ${inst.status}`);
+  // oneClick installer can return microseconds before the exe handle settles.
+  const deadline = Date.now() + 30000;
+  while (Date.now() < deadline && !exists(installedExe)) { execSync('powershell -NoProfile -Command "Start-Sleep -Milliseconds 1000"'); }
+  killRunning();   // defensive: ensure nothing the installer launched is holding the dir
   assertInstalled();
 
   // Launch the INSTALLED exe through the full gate (boot/serve/provenance/etc.).
-  const installedExe = path.join(INSTALL_DIR, 'OpenSwarm.exe');
   if (exists(installedExe)) {
     process.stdout.write('\n[destructive] verifying the INSTALLED app...\n');
     const v = spawnSync(process.execPath, [path.join(__dirname, 'verify-all.js'), '--app', installedExe], { stdio: 'inherit' });