diff --git a/docs/hooks.md b/docs/hooks.md
index 8ee53b9..47dfc4b 100644
--- a/docs/hooks.md
+++ b/docs/hooks.md
@@ -13,7 +13,7 @@ The adapters register these events:
 
 The main agent alone maintains canonical task state. Hooks never write or summarize it, print its contents, or infer completed verification. They use the hook event's `cwd`, falling back to the process working directory when no workspace is supplied. Malformed event data does not fall back to another project. An absent state file is a successful no-op. Legacy state under the installed configuration root is not automatically adopted; confirm its task before migrating it. The scripts do not grant permissions, bypass approvals, or replace client permission systems.
 
-When enabled during installation or update, Flashbang runs on `Stop`, after the main agent finishes responding. The default flash lasts about 500 milliseconds. The PowerShell command omits `-WindowStyle Hidden`, which can hide or minimize the shared terminal. The PowerShell hook creates a low-opacity click-through overlay without activating another window when its native GUI APIs are available; unsupported runtimes exit safely. The Bash hook uses Python's `tkinter`, uses `xrandr` for multi-monitor bounds when available, and falls back to `notify-send` when the overlay is unavailable. Registered hooks are best effort: errors do not fail a Claude session.
+When enabled during installation or update, Flashbang runs on `Stop`, after the main agent finishes responding. The default flash lasts about 500 milliseconds. The PowerShell command omits `-WindowStyle Hidden`, which can hide or minimize the shared terminal. The PowerShell hook creates a low-opacity click-through overlay without activating another window when its native GUI APIs are available; unsupported runtimes exit safely. Its native DLL cache is optional: a missing `LOCALAPPDATA` environment variable or an unusable cache falls back to in-process compilation instead of suppressing the notification. The Bash hook uses Python's `tkinter`, uses `xrandr` for multi-monitor bounds when available, and falls back to `notify-send` when the overlay is unavailable. Registered hooks are best effort: errors do not fail a Claude session.
 
 `Validate-CommandSafety`/`validate-command-safety.sh` and `Invoke-PostChangeVerification`/`invoke-post-change-verification.sh` are unregistered utilities. The safety utilities check command text for selected dangerous patterns; the PowerShell variant also checks some absolute paths. Neither is a complete security boundary. The verification utilities explicitly run the repository build when invoked; they are not an automatic requirement after each change.
 
diff --git a/scripts/tests/test-session-state.py b/scripts/tests/test-session-state.py
index 0b07db6..a276dfa 100644
--- a/scripts/tests/test-session-state.py
+++ b/scripts/tests/test-session-state.py
@@ -207,15 +207,45 @@ class SessionStateHookTests(unittest.TestCase):
             with self.subTest(shell=shell):
                 environment = dict(os.environ)
                 if shell == 'powershell':
-                    environment['LOCALAPPDATA'] = ''
-                    command = [executable, '-NoProfile', '-ExecutionPolicy', 'Bypass', '-File',
-                               str(ROOT / 'shared/hooks/flashbang.ps1')]
+                    environment['FLASHBANG_TEST_SCRIPT'] = str(ROOT / 'shared/hooks/flashbang.ps1')
+                    command = [executable, '-NoProfile', '-ExecutionPolicy', 'Bypass', '-Command',
+                               "function Add-Type { throw 'GUI runtime unavailable' }; & $env:FLASHBANG_TEST_SCRIPT"]
                 else:
                     environment['PATH'] = ''
                     command = [executable, str(ROOT / 'shared/hooks/flashbang.sh')]
                 result = subprocess.run(command, env=environment, capture_output=True, text=True, timeout=20)
                 self.assertEqual(result.returncode, 0, result.stderr)
 
+    @unittest.skipUnless(os.name == 'nt', 'Windows GUI runtime required')
+    def test_flashbang_cache_is_optional(self):
+        executable = shutil.which('powershell') or shutil.which('pwsh')
+        if not executable:
+            self.skipTest('PowerShell unavailable')
+        # Exercise native initialization, stopping at the UI boundary without flashing the screen.
+        probe = """
+function New-Object {
+    param([string]$TypeName)
+    if ($TypeName -eq 'System.Windows.Forms.Form' -and ('Flashbang.Native' -as [type])) {
+        [Console]::WriteLine('OVERLAY_READY')
+    }
+    throw 'Stop at UI boundary'
+}
+& $env:FLASHBANG_TEST_SCRIPT
+"""
+        with tempfile.TemporaryDirectory(prefix='.flashbang-test-', dir=ROOT) as directory:
+            blocked = Path(directory) / 'not-a-directory'
+            blocked.write_text('keep')
+            for cache in ('', str(blocked), directory):
+                with self.subTest(cache=cache):
+                    environment = dict(os.environ, LOCALAPPDATA=cache,
+                                       FLASHBANG_TEST_SCRIPT=str(ROOT / 'shared/hooks/flashbang.ps1'))
+                    result = subprocess.run([executable, '-NoProfile', '-ExecutionPolicy', 'Bypass',
+                                             '-Command', probe], env=environment, capture_output=True,
+                                            text=True, timeout=20)
+                    self.assertEqual(result.returncode, 0, result.stderr)
+                    self.assertIn('OVERLAY_READY', result.stdout, 'Flashbang exited before creating the overlay')
+            self.assertEqual(blocked.read_text(), 'keep')
+
 
 if __name__ == '__main__':
     unittest.main()
diff --git a/shared/hooks/flashbang.ps1 b/shared/hooks/flashbang.ps1
index e600453..fc5c44b 100644
--- a/shared/hooks/flashbang.ps1
+++ b/shared/hooks/flashbang.ps1
@@ -66,27 +66,27 @@ $nativeSource = @'
 if (-not ('Flashbang.Native' -as [type])) {
     # Keyed by host runtime: an assembly emitted by Windows PowerShell (.NET
     # Framework) is not guaranteed to load under pwsh (.NET), and vice versa.
-    $cacheDir = Join-Path $env:LOCALAPPDATA 'claude-flashbang'
-    $runtimeTag = '{0}{1}' -f $PSVersionTable.PSEdition, $PSVersionTable.PSVersion.Major
-    $cacheDll = Join-Path $cacheDir "Flashbang.Native.$runtimeTag.dll"
-    $loaded = $false
+    try {
+        $cacheDir = Join-Path $env:LOCALAPPDATA 'claude-flashbang'
+        $runtimeTag = '{0}{1}' -f $PSVersionTable.PSEdition, $PSVersionTable.PSVersion.Major
+        $cacheDll = Join-Path $cacheDir "Flashbang.Native.$runtimeTag.dll"
+        $loaded = $false
 
-    if (Test-Path -LiteralPath $cacheDll) {
-        try { Add-Type -Path $cacheDll; $loaded = $true } catch { $loaded = $false }
-    }
+        if (Test-Path -LiteralPath $cacheDll) {
+            try { Add-Type -Path $cacheDll; $loaded = $true } catch { $loaded = $false }
+        }
 
-    if (-not $loaded) {
-        try {
+        if (-not $loaded) {
             if (-not (Test-Path -LiteralPath $cacheDir)) {
                 New-Item -ItemType Directory -Path $cacheDir -Force | Out-Null
             }
             Add-Type -Namespace 'Flashbang' -Name 'Native' -MemberDefinition $nativeSource `
                      -OutputAssembly $cacheDll
             Add-Type -Path $cacheDll
-        } catch {
-            # Cache unavailable (locked file, no write access) - compile in-process.
-            Add-Type -Namespace 'Flashbang' -Name 'Native' -MemberDefinition $nativeSource
         }
+    } catch {
+        # Missing profile environment or unusable cache must not suppress the flash.
+        Add-Type -Namespace 'Flashbang' -Name 'Native' -MemberDefinition $nativeSource
     }
 }