diff --git a/openless-all/app/scripts/windows-ime-install-smoke.ps1 b/openless-all/app/scripts/windows-ime-install-smoke.ps1
index a3b25de7..7946c040 100644
--- a/openless-all/app/scripts/windows-ime-install-smoke.ps1
+++ b/openless-all/app/scripts/windows-ime-install-smoke.ps1
@@ -16,9 +16,9 @@ $KeyboardCategoryGuid = "{34745C63-B2F0-4784-8B67-5E12C8701A31}"
 $ImmersiveCategoryGuid = "{13A016DF-560B-46CD-947A-4C3AF1E0E35D}"
 $SystrayCategoryGuid = "{25504FB4-7BAB-4BC1-9C69-CF81890F0EF5}"
 
-# Keep this script aligned with the backend status check and the TSF IPC path
-# used by OpenLessImeSubmit-* named pipes.
-$ExpectedBackendKeys = @(
+# Keep this script aligned with the default Windows backend: OpenLess ships the
+# TSF DLLs for optional diagnostics, but installers must not register the TIP.
+$ExpectedUnregisteredKeys = @(
   "Software\Classes\CLSID\{6B9F3F4F-5EE7-42D6-9C61-9F80B03A5D7D}\InprocServer32",
   "Software\WOW6432Node\Classes\CLSID\{6B9F3F4F-5EE7-42D6-9C61-9F80B03A5D7D}\InprocServer32",
   "Software\Microsoft\CTF\TIP\{6B9F3F4F-5EE7-42D6-9C61-9F80B03A5D7D}\LanguageProfile\0x00000804\{9B5F5E04-23F6-47DA-9A26-D221F6C3F02E}",
@@ -103,7 +103,7 @@ function Assert-RegistryKey {
   Write-Host "[ok] $Label registry key present ($View)"
 }
 
-function Get-DefaultRegistryValue {
+function Assert-RegistryKeyAbsent {
   param(
     [Parameter(Mandatory = $true)]
     [Microsoft.Win32.RegistryView]$View,
@@ -114,54 +114,41 @@ function Get-DefaultRegistryValue {
   )
 
   $key = Open-LocalMachineSubKey -View $View -SubKey $SubKey
-  if ($null -eq $key) {
-    throw "Missing $Label registry key ($View): HKLM\$SubKey"
-  }
-  try {
-    $value = [string]$key.GetValue("")
-    if ([string]::IsNullOrWhiteSpace($value)) {
-      throw "$Label default registry value is empty ($View): HKLM\$SubKey"
-    }
-    return $value
-  } finally {
+  if ($null -ne $key) {
     $key.Close()
+    throw "Unexpected $Label registry key ($View): HKLM\$SubKey"
   }
+  Write-Host "[ok] $Label registry key absent ($View)"
 }
 
 function Assert-OpenLessImeInstalled {
-  $comKey = "Software\Classes\CLSID\$TextServiceClsid\InprocServer32"
-  $x64Dll = Get-DefaultRegistryValue -View Registry64 -SubKey $comKey -Label "x64 COM"
-  $x86Dll = Get-DefaultRegistryValue -View Registry32 -SubKey $comKey -Label "x86 COM"
+  $installRootCandidates = @(
+    (Join-Path $env:ProgramFiles "OpenLess")
+  )
+  if ($env:ProgramFiles -ne ${env:ProgramFiles(x86)}) {
+    $installRootCandidates += (Join-Path ${env:ProgramFiles(x86)} "OpenLess")
+  }
 
-  foreach ($dll in @($x64Dll, $x86Dll)) {
-    if (-not (Test-Path -LiteralPath $dll -PathType Leaf)) {
-      throw "Registered IME DLL path does not exist: $dll"
-    }
+  $installRoot = $installRootCandidates |
+    Where-Object { Test-Path -LiteralPath (Join-Path $_ "openless.exe") -PathType Leaf } |
+    Select-Object -First 1
+  if ([string]::IsNullOrWhiteSpace($installRoot)) {
+    throw "Installed OpenLess executable not found under: $($installRootCandidates -join ', ')"
   }
 
-  $installRoot = Split-Path -Parent (Split-Path -Parent (Split-Path -Parent $x64Dll))
   $expectedX64 = Join-Path $installRoot "windows-ime\x64\OpenLessIme.dll"
   $expectedX86 = Join-Path $installRoot "windows-ime\x86\OpenLessIme.dll"
-  if ($x64Dll -ne $expectedX64) {
-    throw "x64 COM DLL path points outside the installed IME directory. Expected '$expectedX64', got '$x64Dll'"
-  }
-  if ($x86Dll -ne $expectedX86) {
-    throw "x86 COM DLL path points outside the installed IME directory. Expected '$expectedX86', got '$x86Dll'"
-  }
-  if (-not (Test-Path -LiteralPath (Join-Path $installRoot "openless.exe") -PathType Leaf)) {
-    throw "Installed OpenLess executable not found under $installRoot"
+  foreach ($dll in @($expectedX64, $expectedX86)) {
+    if (-not (Test-Path -LiteralPath $dll -PathType Leaf)) {
+      throw "Packaged optional IME DLL path does not exist: $dll"
+    }
   }
 
-  Assert-RegistryKey -View Registry64 -SubKey "Software\Microsoft\CTF\TIP\$TextServiceClsid\LanguageProfile\$LangId\$ProfileGuid" -Label "TSF language profile"
-  Assert-RegistryKey -View Registry64 -SubKey "Software\Microsoft\CTF\TIP\$TextServiceClsid\Category\Category\$KeyboardCategoryGuid\$TextServiceClsid" -Label "TSF keyboard category"
-  Assert-RegistryKey -View Registry64 -SubKey "Software\Microsoft\CTF\TIP\$TextServiceClsid\Category\Category\$ImmersiveCategoryGuid\$TextServiceClsid" -Label "TSF immersive category"
-  Assert-RegistryKey -View Registry64 -SubKey "Software\Microsoft\CTF\TIP\$TextServiceClsid\Category\Category\$SystrayCategoryGuid\$TextServiceClsid" -Label "TSF systray category"
-
-  foreach ($key in $ExpectedBackendKeys) {
-    Assert-RegistryKey -View Registry64 -SubKey $key -Label "backend-required"
+  foreach ($key in $ExpectedUnregisteredKeys) {
+    Assert-RegistryKeyAbsent -View Registry64 -SubKey $key -Label "default-disabled TSF"
   }
 
-  Write-Host "[ok] Windows IME backend would report installed"
+  Write-Host "[ok] OpenLess installed with TSF registration disabled by default"
   return $installRoot
 }
 
diff --git a/openless-all/app/scripts/windows-package-msvc.test.mjs b/openless-all/app/scripts/windows-package-msvc.test.mjs
index ce5aa4ec..f48cbafb 100644
--- a/openless-all/app/scripts/windows-package-msvc.test.mjs
+++ b/openless-all/app/scripts/windows-package-msvc.test.mjs
@@ -96,7 +96,7 @@ assert.deepEqual(tauriConfig.bundle.windows.wix.componentRefs, [
   "OpenLessImeDllX86Component",
 ]);
 assert.equal(tauriConfig.bundle.windows.nsis.installMode, "perMachine", "NSIS must force a machine-wide install because TSF registration is machine-wide");
-assert.equal(tauriConfig.bundle.windows.nsis.installerHooks, "nsis/openless-ime-hooks.nsh", "NSIS must install and register the TSF DLLs");
+assert.equal(tauriConfig.bundle.windows.nsis.installerHooks, "nsis/openless-ime-hooks.nsh", "NSIS must stage the optional TSF DLLs and clean legacy registration");
 
 assert.match(imeSolution, /Release\|Win32/, "IME solution should include a Win32 Release configuration");
 assert.match(imeProject, /Release\|Win32/, "IME project should include a Win32 Release configuration");
@@ -113,16 +113,16 @@ assert.match(wixFragment, /Component Id="OpenLessImeDllX64Component"/, "WiX frag
 assert.match(wixFragment, /Component Id="OpenLessImeDllX86Component"/, "WiX fragment should define the x86 TSF DLL component");
 assert.match(wixFragment, /Source="src-tauri\\target\\windows-ime-msvc\\x64\\Release\\OpenLessIme\.dll"/, "WiX fragment should consume the package-built x64 IME DLL");
 assert.match(wixFragment, /Source="src-tauri\\target\\windows-ime-msvc\\x86\\Release\\OpenLessIme\.dll"/, "WiX fragment should consume the package-built x86 IME DLL");
-assert.match(wixFragment, /regsvr32\.exe/, "MSI should register and unregister the TSF DLL");
-assert.match(wixFragment, /\[System64Folder\]regsvr32\.exe/, "MSI should register the x64 IME with 64-bit regsvr32");
-assert.match(wixFragment, /\[WindowsFolder\]SysWOW64\\regsvr32\.exe/, "MSI should register the x86 IME with 32-bit regsvr32");
-assert.match(wixFragment, /RegisterOpenLessImeX64/, "MSI should register x64 OpenLess IME during install");
-assert.match(wixFragment, /RegisterOpenLessImeX86/, "MSI should register x86 OpenLess IME during install");
-assert.match(wixFragment, /UnregisterOpenLessImeX64/, "MSI should unregister x64 OpenLess IME during uninstall");
-assert.match(wixFragment, /UnregisterOpenLessImeX86/, "MSI should unregister x86 OpenLess IME during uninstall");
+assert.match(wixFragment, /regsvr32\.exe/, "MSI should retain regsvr32 custom actions for cleanup/diagnostics");
+assert.match(wixFragment, /\[System64Folder\]regsvr32\.exe/, "MSI should know how to unregister the x64 IME with 64-bit regsvr32");
+assert.match(wixFragment, /\[WindowsFolder\]SysWOW64\\regsvr32\.exe/, "MSI should know how to unregister the x86 IME with 32-bit regsvr32");
+assert.doesNotMatch(wixFragment, /<Custom Action="RegisterOpenLessImeX64"/, "MSI should not register x64 OpenLess IME during install by default");
+assert.doesNotMatch(wixFragment, /<Custom Action="RegisterOpenLessImeX86"/, "MSI should not register x86 OpenLess IME during install by default");
+assert.match(wixFragment, /<Custom Action="UnregisterOpenLessImeX64"/, "MSI should clean legacy x64 OpenLess IME registration during upgrade");
+assert.match(wixFragment, /<Custom Action="UnregisterOpenLessImeX86"/, "MSI should clean legacy x86 OpenLess IME registration during upgrade");
 
 assert.match(nsisHook, /NSIS_HOOK_PREINSTALL/, "NSIS should copy IME DLLs before install completes");
-assert.match(nsisHook, /NSIS_HOOK_POSTINSTALL/, "NSIS should register IME DLLs after files are installed");
+assert.match(nsisHook, /NSIS_HOOK_POSTINSTALL/, "NSIS should define a postinstall hook");
 assert.match(nsisHook, /NSIS_HOOK_PREUNINSTALL/, "NSIS should unregister IME DLLs before uninstall removes them");
 assert.match(nsisHook, /OPENLESS_IME_STAGE_AND_REPLACE "x64" "OPENLESS_IME_DLL_X64"/, "NSIS should consume the CI-built x64 IME DLL");
 assert.match(nsisHook, /OPENLESS_IME_STAGE_AND_REPLACE "x86" "OPENLESS_IME_DLL_X86"/, "NSIS should consume the CI-built x86 IME DLL");
@@ -131,10 +131,9 @@ assert.match(nsisHook, /File \/oname=OpenLessIme\.dll\.new "\$%\$\{ENV_VAR\}%"/,
 assert.match(nsisHook, /Sysnative\\regsvr32\.exe/, "NSIS should use 64-bit regsvr32 for the x64 IME");
 assert.match(nsisHook, /SysWOW64\\regsvr32\.exe/, "NSIS should use 32-bit regsvr32 for the x86 IME");
 assert.match(nsisHook, /System32\\regsvr32\.exe[\s\S]*windows-ime\\x86\\OpenLessIme\.dll/, "NSIS should use System32 regsvr32 for the x86 IME on 32-bit Windows");
-assert.match(nsisHook, /Abort/, "NSIS install should fail if TSF registration fails");
-assert.match(nsisHook, /OPENLESS_IME_ABORT_IF_FAILED \$0 "x64 registration"/, "NSIS install should fail if x64 TSF registration fails");
-assert.match(nsisHook, /OPENLESS_IME_ABORT_IF_FAILED \$0 "x86 registration"/, "NSIS install should fail if x86 TSF registration fails");
-assert.match(nsisHook, /OPENLESS_IME_REGISTER_X86[\s\S]*\$\{If\} \$0 != 0[\s\S]*StrCpy \$1 \$0[\s\S]*OPENLESS_IME_UNREGISTER_X64[\s\S]*StrCpy \$0 \$1[\s\S]*OPENLESS_IME_ABORT_IF_FAILED \$0 "x86 registration"/, "NSIS install should roll back x64 registration before aborting on x86 registration failure");
+assert.match(nsisHook, /TSF IME registration skipped/, "NSIS should skip default TSF registration");
+assert.doesNotMatch(nsisHook, /NSIS_HOOK_POSTINSTALL[\s\S]*OPENLESS_IME_REGISTER_X64[\s\S]*!macroend/, "NSIS postinstall should not register the x64 TSF IME");
+assert.doesNotMatch(nsisHook, /NSIS_HOOK_POSTINSTALL[\s\S]*OPENLESS_IME_REGISTER_X86[\s\S]*!macroend/, "NSIS postinstall should not register the x86 TSF IME");
 assert.doesNotMatch(nsisHook, /OPENLESS_IME_ABORT_IF_FAILED \$0 "x64 unregistration"/, "NSIS uninstall should not fail if x64 TSF unregistration fails");
 assert.doesNotMatch(nsisHook, /OPENLESS_IME_ABORT_IF_FAILED \$0 "x86 unregistration"/, "NSIS uninstall should not fail if x86 TSF unregistration fails");
 assert.match(nsisHook, /OpenLess x64 TSF IME unregister exit code \$0/, "NSIS uninstall should log x64 TSF unregistration failures");
@@ -144,13 +143,12 @@ assert.match(imeInstallSmoke, /\[ValidateSet\("nsis", "msi"\)\]/, "install smoke
 assert.match(imeInstallSmoke, /Join-ProcessArguments/, "install smoke should quote process arguments before Start-Process");
 assert.match(imeInstallSmoke, /\$commandLine = Join-ProcessArguments \$ArgumentList/, "install smoke should build a single quoted command line");
 assert.match(imeInstallSmoke, /Start-Process -FilePath \$FilePath -ArgumentList \$commandLine/, "install smoke should pass a single quoted command line to Start-Process");
-assert.match(imeInstallSmoke, /OpenLessImeSubmit/, "install smoke should preserve TSF backend context");
-assert.match(imeInstallSmoke, /Software\\Classes\\CLSID\\\{6B9F3F4F-5EE7-42D6-9C61-9F80B03A5D7D\}\\InprocServer32/, "install smoke should check x64 COM registration");
-assert.match(imeInstallSmoke, /Software\\WOW6432Node\\Classes\\CLSID\\\{6B9F3F4F-5EE7-42D6-9C61-9F80B03A5D7D\}\\InprocServer32/, "install smoke should check x86 COM registration");
-assert.match(imeInstallSmoke, /LanguageProfile\\0x00000804\\\{9B5F5E04-23F6-47DA-9A26-D221F6C3F02E\}/, "install smoke should check the TSF language profile");
-assert.match(imeInstallSmoke, /Category\\Category\\\{34745C63-B2F0-4784-8B67-5E12C8701A31\}/, "install smoke should check the keyboard TSF category");
-assert.match(imeInstallSmoke, /foreach \(\$key in \$ExpectedBackendKeys\) \{[\s\S]*Assert-RegistryKey -View Registry64 -SubKey \$key[\s\S]*\}/, "install smoke should assert every backend-required registry key exists");
-assert.doesNotMatch(imeInstallSmoke, /foreach \(\$key in \$ExpectedBackendKeys\) \{[\s\S]*Write-Host "\[trace\] backend-required key: HKLM\\\$key"[\s\S]*\}/, "install smoke must not only trace backend-required registry keys");
+assert.match(imeInstallSmoke, /ExpectedUnregisteredKeys/, "install smoke should track TSF keys that must stay absent by default");
+assert.match(imeInstallSmoke, /Software\\Classes\\CLSID\\\{6B9F3F4F-5EE7-42D6-9C61-9F80B03A5D7D\}\\InprocServer32/, "install smoke should check x64 COM registration absence");
+assert.match(imeInstallSmoke, /Software\\WOW6432Node\\Classes\\CLSID\\\{6B9F3F4F-5EE7-42D6-9C61-9F80B03A5D7D\}\\InprocServer32/, "install smoke should check x86 COM registration absence");
+assert.match(imeInstallSmoke, /LanguageProfile\\0x00000804\\\{9B5F5E04-23F6-47DA-9A26-D221F6C3F02E\}/, "install smoke should check the TSF language profile absence");
+assert.match(imeInstallSmoke, /Category\\Category\\\{34745C63-B2F0-4784-8B67-5E12C8701A31\}/, "install smoke should check the keyboard TSF category absence");
+assert.match(imeInstallSmoke, /Assert-RegistryKeyAbsent -View Registry64 -SubKey \$key/, "install smoke should assert every default-disabled TSF registry key is absent");
 assert.match(ciWorkflow, /windows-ime-install-smoke\.ps1[\s\S]*-InstallerKind nsis/, "CI should install and verify the NSIS artifact");
 assert.match(ciWorkflow, /windows-ime-install-smoke\.ps1[\s\S]*-InstallerKind msi/, "CI should install and verify the MSI artifact");
 assert.match(ciWorkflow, /InstallerKind nsis[\s\S]*\$LASTEXITCODE -ne 0[\s\S]*NSIS installer smoke failed/, "CI should fail immediately when the NSIS smoke run fails");
diff --git a/openless-all/app/src-tauri/nsis/openless-ime-hooks.nsh b/openless-all/app/src-tauri/nsis/openless-ime-hooks.nsh
index cdf6c9ff..67a5dbf0 100644
--- a/openless-all/app/src-tauri/nsis/openless-ime-hooks.nsh
+++ b/openless-all/app/src-tauri/nsis/openless-ime-hooks.nsh
@@ -89,8 +89,7 @@
 !macroend
 
 !macro NSIS_HOOK_POSTINSTALL
-  !insertmacro OPENLESS_IME_REGISTER_X64
-  !insertmacro OPENLESS_IME_REGISTER_X86
+  DetailPrint "OpenLess TSF IME registration skipped; Windows uses Unicode SendInput by default"
 !macroend
 
 !macro NSIS_HOOK_PREUNINSTALL
diff --git a/openless-all/app/src-tauri/src/coordinator.rs b/openless-all/app/src-tauri/src/coordinator.rs
index 3ee50c36..cca9b4db 100644
--- a/openless-all/app/src-tauri/src/coordinator.rs
+++ b/openless-all/app/src-tauri/src/coordinator.rs
@@ -1765,19 +1765,13 @@ fn insert_via_non_tsf_fallback(
 
     match status {
         InsertStatus::Inserted => {
-            log::warn!(
-                "[windows-ime] TSF unavailable; inserted via paced Unicode SendInput fallback"
-            );
+            log::info!("[windows-ime] inserted via paced Unicode SendInput");
         }
         InsertStatus::CopiedFallback => {
-            log::warn!(
-                "[windows-ime] TSF unavailable; Unicode SendInput failed, left text on clipboard"
-            );
+            log::warn!("[windows-ime] Unicode SendInput failed, left text on clipboard");
         }
         InsertStatus::PasteSent | InsertStatus::Failed => {
-            log::warn!(
-                "[windows-ime] TSF unavailable; Unicode SendInput fallback failed and copy fallback failed"
-            );
+            log::warn!("[windows-ime] Unicode SendInput failed and copy fallback failed");
         }
     }
 
@@ -1861,8 +1855,6 @@ mod non_tsf_fallback_tests {
 
 // ─────────────────────────── helpers ───────────────────────────
 
-
-
 fn read_whisper_credentials() -> (String, String, String) {
     let api_key = CredentialsVault::get(CredentialAccount::AsrApiKey)
         .ok()
@@ -1959,7 +1951,6 @@ fn enabled_hotwords(inner: &Arc<Inner>) -> Vec<DictionaryHotword> {
         .collect()
 }
 
-
 /// 读 Gemini 凭据。所有 LLM provider 共用 ark.* 槽位（persistence 没做 per-provider
 /// 隔离），所以这里也是从 `ArkApiKey` / `ArkModelId` / `ArkEndpoint` 三个槽读，
 /// 但回退默认值改成谷歌的：base_url 默认 `https://generativelanguage.googleapis.com/v1beta`，
@@ -3037,7 +3028,6 @@ fn schedule_capsule_idle(inner: &Arc<Inner>, delay_ms: u64) {
     });
 }
 
-
 // ─────────────────────────── audio bridge ───────────────────────────
 
 struct DeferredAsrBridge {
diff --git a/openless-all/app/src-tauri/src/coordinator/dictation.rs b/openless-all/app/src-tauri/src/coordinator/dictation.rs
index 8a86e65d..6df990c9 100644
--- a/openless-all/app/src-tauri/src/coordinator/dictation.rs
+++ b/openless-all/app/src-tauri/src/coordinator/dictation.rs
@@ -1004,10 +1004,7 @@ pub(super) async fn begin_session(inner: &Arc<Inner>) -> Result<(), String> {
 
 /// begin_session 的带参版本，voice_agent=true 时在 Starting 阶段就标记好，
 /// 防止 finish_starting_session 处理 pending_stop 时丢失标志。
-pub(super) async fn begin_session_as(
-    inner: &Arc<Inner>,
-    voice_agent: bool,
-) -> Result<(), String> {
+pub(super) async fn begin_session_as(inner: &Arc<Inner>, voice_agent: bool) -> Result<(), String> {
     let current_session_id = {
         let mut state = inner.state.lock();
         let Some(session_id) =
@@ -1025,9 +1022,13 @@ pub(super) async fn begin_session_as(
     };
     #[cfg(target_os = "windows")]
     {
-        let prepared = inner.windows_ime.prepare_session();
-        let mut slots = inner.prepared_windows_ime_session.lock();
-        store_prepared_windows_ime_session(&mut slots, current_session_id, prepared);
+        if inner.prefs.get().windows_tsf_backend_enabled {
+            let prepared = inner.windows_ime.prepare_session();
+            let mut slots = inner.prepared_windows_ime_session.lock();
+            store_prepared_windows_ime_session(&mut slots, current_session_id, prepared);
+        } else {
+            log::debug!("[windows-ime] TSF backend disabled; using Unicode SendInput insertion");
+        }
     }
     // 翻译模式标志重置；hotkey 监听器在 Shift down 时再 set true。
     inner
@@ -2301,6 +2302,7 @@ pub(super) async fn end_session(inner: &Arc<Inner>) -> Result<(), String> {
     let prefs = inner.prefs.get();
     let restore_clipboard = prefs.restore_clipboard_after_paste;
     let allow_non_tsf_insertion_fallback = prefs.allow_non_tsf_insertion_fallback;
+    let windows_tsf_backend_enabled = prefs.windows_tsf_backend_enabled;
     let paste_shortcut = prefs.paste_shortcut;
     // 流式路径下，字符已经通过 Unicode keystroke 落到光标处，跳过 inserter.insert。
     let status = if already_streamed {
@@ -2323,17 +2325,26 @@ pub(super) async fn end_session(inner: &Arc<Inner>) -> Result<(), String> {
         if focus_ready_for_paste {
             #[cfg(target_os = "windows")]
             {
-                let ime_target = capture_ime_submit_target();
-                insert_with_windows_ime_first(
-                    inner,
-                    current_session_id,
-                    &polished,
-                    restore_clipboard,
-                    allow_non_tsf_insertion_fallback,
-                    paste_shortcut,
-                    ime_target,
-                )
-                .await
+                if windows_tsf_backend_enabled {
+                    let ime_target = capture_ime_submit_target();
+                    insert_with_windows_ime_first(
+                        inner,
+                        current_session_id,
+                        &polished,
+                        restore_clipboard,
+                        allow_non_tsf_insertion_fallback,
+                        paste_shortcut,
+                        ime_target,
+                    )
+                    .await
+                } else if allow_non_tsf_insertion_fallback {
+                    insert_via_non_tsf_fallback(inner, &polished, restore_clipboard, paste_shortcut)
+                } else {
+                    log::warn!(
+                        "[windows-ime] TSF backend disabled and Unicode insertion fallback disabled"
+                    );
+                    InsertStatus::Failed
+                }
             }
             #[cfg(not(target_os = "windows"))]
             {
diff --git a/openless-all/app/src-tauri/src/hotkey.rs b/openless-all/app/src-tauri/src/hotkey.rs
index 7fa0eaea..d8f73d3c 100644
--- a/openless-all/app/src-tauri/src/hotkey.rs
+++ b/openless-all/app/src-tauri/src/hotkey.rs
@@ -996,7 +996,23 @@ mod platform {
             }
             _ => {}
         }
-        true
+        should_suppress_trigger(trigger)
+    }
+
+    fn should_suppress_trigger(trigger: HotkeyTrigger) -> bool {
+        // Modifier-only hotkeys on Windows are safer when the physical key state
+        // is still allowed to flow through to the foreground app. Swallowing the
+        // down/up edges for Ctrl/Alt can leave shell and Chromium-family apps in
+        // odd input states while OpenLess later submits text through TSF.
+        !matches!(
+            trigger,
+            HotkeyTrigger::LeftControl
+                | HotkeyTrigger::RightControl
+                | HotkeyTrigger::LeftOption
+                | HotkeyTrigger::RightOption
+                | HotkeyTrigger::RightAlt
+                | HotkeyTrigger::Fn
+        )
     }
 
     fn handle_optional_modifier_trigger(
@@ -1091,10 +1107,10 @@ mod platform {
             let shared = shared(HotkeyTrigger::RightControl);
             let (ctx, rx) = callback_context(shared);
 
-            assert!(dispatch_keyboard_event(&ctx, VK_RCONTROL, WM_KEYDOWN));
-            assert!(dispatch_keyboard_event(&ctx, VK_RCONTROL, WM_KEYDOWN));
-            assert!(dispatch_keyboard_event(&ctx, VK_RCONTROL, WM_KEYUP));
-            assert!(dispatch_keyboard_event(&ctx, VK_RCONTROL, WM_KEYUP));
+            assert!(!dispatch_keyboard_event(&ctx, VK_RCONTROL, WM_KEYDOWN));
+            assert!(!dispatch_keyboard_event(&ctx, VK_RCONTROL, WM_KEYDOWN));
+            assert!(!dispatch_keyboard_event(&ctx, VK_RCONTROL, WM_KEYUP));
+            assert!(!dispatch_keyboard_event(&ctx, VK_RCONTROL, WM_KEYUP));
 
             assert_eq!(
                 drain(&rx),
@@ -1108,10 +1124,10 @@ mod platform {
             let (ctx, rx) = callback_context(shared);
 
             assert!(!dispatch_keyboard_event(&ctx, VK_LCONTROL, WM_KEYDOWN));
-            assert!(dispatch_keyboard_event(&ctx, VK_RCONTROL, WM_KEYUP));
-            assert!(dispatch_keyboard_event(&ctx, VK_RCONTROL, WM_KEYDOWN));
-            assert!(dispatch_keyboard_event(&ctx, VK_RCONTROL, WM_KEYUP));
-            assert!(dispatch_keyboard_event(&ctx, VK_RCONTROL, WM_KEYDOWN));
+            assert!(!dispatch_keyboard_event(&ctx, VK_RCONTROL, WM_KEYUP));
+            assert!(!dispatch_keyboard_event(&ctx, VK_RCONTROL, WM_KEYDOWN));
+            assert!(!dispatch_keyboard_event(&ctx, VK_RCONTROL, WM_KEYUP));
+            assert!(!dispatch_keyboard_event(&ctx, VK_RCONTROL, WM_KEYDOWN));
 
             assert_eq!(
                 drain(&rx),
@@ -1155,8 +1171,8 @@ mod platform {
             let (left_ctx, left_rx) = callback_context(left_shared);
 
             assert!(!dispatch_keyboard_event(&left_ctx, VK_RMENU, WM_KEYDOWN));
-            assert!(dispatch_keyboard_event(&left_ctx, VK_LMENU, WM_KEYDOWN));
-            assert!(dispatch_keyboard_event(&left_ctx, VK_LMENU, WM_KEYUP));
+            assert!(!dispatch_keyboard_event(&left_ctx, VK_LMENU, WM_KEYDOWN));
+            assert!(!dispatch_keyboard_event(&left_ctx, VK_LMENU, WM_KEYUP));
             assert_eq!(
                 drain(&left_rx),
                 vec![HotkeyEvent::Pressed, HotkeyEvent::Released]
@@ -1169,7 +1185,7 @@ mod platform {
                 VK_LMENU,
                 WM_KEYDOWN
             ));
-            assert!(dispatch_keyboard_event(
+            assert!(!dispatch_keyboard_event(
                 &right_option_ctx,
                 VK_RMENU,
                 WM_KEYDOWN
@@ -1183,7 +1199,7 @@ mod platform {
                 VK_LMENU,
                 WM_KEYDOWN
             ));
-            assert!(dispatch_keyboard_event(
+            assert!(!dispatch_keyboard_event(
                 &right_alt_ctx,
                 VK_RMENU,
                 WM_KEYDOWN
diff --git a/openless-all/app/src-tauri/src/types.rs b/openless-all/app/src-tauri/src/types.rs
index 3348ee0e..2da63161 100644
--- a/openless-all/app/src-tauri/src/types.rs
+++ b/openless-all/app/src-tauri/src/types.rs
@@ -589,6 +589,11 @@ pub struct UserPreferences {
     /// 默认开启以保持可用性；关闭后可验证文本是否真正由 TSF 上屏。
     #[serde(default = "default_true")]
     pub allow_non_tsf_insertion_fallback: bool,
+    /// Windows: opt back into the in-process TSF IME backend. Disabled by
+    /// default because Chromium/Electron hosts can hang when a TIP DLL joins
+    /// their TSF/COM message chain.
+    #[serde(default)]
+    pub windows_tsf_backend_enabled: bool,
     /// 用户的工作语言（多选，原生名）。会作为前提注入 LLM polish/translate 的 system prompt 头部，
     /// 让模型知道该用户在哪些语言间工作。详见 issue #4。
     #[serde(default = "default_working_languages")]
@@ -885,6 +890,8 @@ struct UserPreferencesWire {
     #[serde(default)]
     paste_shortcut: PasteShortcut,
     allow_non_tsf_insertion_fallback: bool,
+    #[serde(default)]
+    windows_tsf_backend_enabled: bool,
     working_languages: Vec<String>,
     translation_target_language: String,
     chinese_script_preference: ChineseScriptPreference,
@@ -1006,6 +1013,7 @@ impl Default for UserPreferencesWire {
             restore_clipboard_after_paste: prefs.restore_clipboard_after_paste,
             paste_shortcut: prefs.paste_shortcut,
             allow_non_tsf_insertion_fallback: prefs.allow_non_tsf_insertion_fallback,
+            windows_tsf_backend_enabled: prefs.windows_tsf_backend_enabled,
             working_languages: prefs.working_languages,
             translation_target_language: prefs.translation_target_language,
             chinese_script_preference: prefs.chinese_script_preference,
@@ -1106,6 +1114,7 @@ impl<'de> Deserialize<'de> for UserPreferences {
             restore_clipboard_after_paste: wire.restore_clipboard_after_paste,
             paste_shortcut: wire.paste_shortcut,
             allow_non_tsf_insertion_fallback: wire.allow_non_tsf_insertion_fallback,
+            windows_tsf_backend_enabled: wire.windows_tsf_backend_enabled,
             working_languages: wire.working_languages,
             translation_target_language: wire.translation_target_language,
             chinese_script_preference: wire.chinese_script_preference,
@@ -1849,6 +1858,7 @@ impl Default for UserPreferences {
             restore_clipboard_after_paste: true,
             paste_shortcut: PasteShortcut::default(),
             allow_non_tsf_insertion_fallback: true,
+            windows_tsf_backend_enabled: false,
             working_languages: default_working_languages(),
             translation_target_language: String::new(),
             chinese_script_preference: ChineseScriptPreference::Auto,
@@ -2592,6 +2602,20 @@ mod tests {
         assert!(prefs.allow_non_tsf_insertion_fallback);
     }
 
+    #[test]
+    fn windows_tsf_backend_defaults_to_disabled() {
+        let prefs = UserPreferences::default();
+
+        assert!(!prefs.windows_tsf_backend_enabled);
+    }
+
+    #[test]
+    fn missing_windows_tsf_backend_pref_defaults_to_disabled() {
+        let prefs: UserPreferences = serde_json::from_str("{}").unwrap();
+
+        assert!(!prefs.windows_tsf_backend_enabled);
+    }
+
     #[test]
     fn missing_audio_cue_on_record_pref_defaults_to_enabled() {
         // 老用户的 preferences.json 没有这个字段 → 应默认开启（按下录音即提示）。
diff --git a/openless-all/app/src-tauri/src/windows_ime_profile.rs b/openless-all/app/src-tauri/src/windows_ime_profile.rs
index 8ec380f2..3b8f752b 100644
--- a/openless-all/app/src-tauri/src/windows_ime_profile.rs
+++ b/openless-all/app/src-tauri/src/windows_ime_profile.rs
@@ -408,13 +408,15 @@ mod windows_impl {
             RegistrationInspection::Installed { dll_path } => WindowsImeStatus {
                 state: WindowsImeInstallState::Installed,
                 using_tsf_backend: true,
-                message: "OpenLess TSF IME registration is present".to_string(),
+                message: "Experimental OpenLess TSF IME registration is present".to_string(),
                 dll_path: Some(dll_path),
             },
             RegistrationInspection::NotInstalled => WindowsImeStatus {
                 state: WindowsImeInstallState::NotInstalled,
                 using_tsf_backend: false,
-                message: "OpenLess TSF IME registration was not found".to_string(),
+                message:
+                    "OpenLess TSF IME is not registered; Windows uses Unicode SendInput by default"
+                        .to_string(),
                 dll_path: None,
             },
             RegistrationInspection::Broken { dll_path, reason } => WindowsImeStatus {
diff --git a/openless-all/app/src-tauri/wix/openless-ime.wxs b/openless-all/app/src-tauri/wix/openless-ime.wxs
index 8cec239d..553aac11 100644
--- a/openless-all/app/src-tauri/wix/openless-ime.wxs
+++ b/openless-all/app/src-tauri/wix/openless-ime.wxs
@@ -57,8 +57,6 @@
            uninstall and skipped the auto-update / minor-upgrade path. -->
       <Custom Action="UnregisterOpenLessImeX86" Before="InstallFiles"><![CDATA[Installed AND NOT REMOVE]]></Custom>
       <Custom Action="UnregisterOpenLessImeX64" Before="UnregisterOpenLessImeX86"><![CDATA[Installed AND NOT REMOVE]]></Custom>
-      <Custom Action="RegisterOpenLessImeX64" After="InstallFiles"><![CDATA[NOT REMOVE]]></Custom>
-      <Custom Action="RegisterOpenLessImeX86" After="RegisterOpenLessImeX64"><![CDATA[NOT REMOVE]]></Custom>
     </InstallExecuteSequence>
   </Fragment>
 </Wix>
diff --git a/openless-all/app/src/i18n/en.ts b/openless-all/app/src/i18n/en.ts
index fcf71ca3..f9547f89 100644
--- a/openless-all/app/src/i18n/en.ts
+++ b/openless-all/app/src/i18n/en.ts
@@ -682,8 +682,8 @@ export const en: typeof zhCN = {
       comboRecorded: 'Recorded',
       comboClear: 'Clear',
       comboConflict: 'This shortcut combination is not available',
-      allowNonTsfFallbackLabel: 'Allow non-TSF fallback',
-      allowNonTsfFallbackDesc: 'Windows: when TSF insertion fails, use paced Unicode SendInput; if that still fails, copy the text to the clipboard.',
+      allowNonTsfFallbackLabel: 'Allow Unicode SendInput insertion',
+      allowNonTsfFallbackDesc: 'Windows: use paced Unicode SendInput by default; if that fails, copy the text to the clipboard.',
       historyGroupTitle: 'History & context',
       historyRetentionLabel: 'History retention (days)',
       historyRetentionDesc: 'Entries older than this are pruned on new writes; 0 = no time-based pruning.',
@@ -847,7 +847,7 @@ export const en: typeof zhCN = {
       hotkeyStarting: 'Installing…',
       hotkeyFailed: 'Listener failed',
       windowsImeLabel: 'Windows input method backend',
-      windowsImeDesc: 'Temporarily switches to the OpenLess TSF IME during voice sessions to avoid clipboard insertion limits.',
+      windowsImeDesc: 'Optional experimental TSF IME backend. Windows uses Unicode SendInput by default to avoid in-process text-service hangs.',
       windowsImeInstalled: 'Installed',
       windowsImeUnavailable: 'Unavailable',
       androidImeLabel: 'Input method (IME)',
@@ -910,9 +910,9 @@ export const en: typeof zhCN = {
         down: 'Swipe down while recording to cancel without transcription or insertion.',
       },
       windowsIme: {
-        installed: 'Installed. Voice input temporarily switches to the OpenLess IME.',
-        notInstalled: 'Not installed. OpenLess is using the clipboard/WM_PASTE fallback.',
-        registrationBroken: 'Registration is broken. Reinstall the OpenLess IME.',
+        installed: 'Experimental TSF backend is registered.',
+        notInstalled: 'Not registered. OpenLess uses Unicode SendInput by default.',
+        registrationBroken: 'Experimental TSF registration is broken.',
         notWindows: 'Only available on Windows.',
       },
     },
diff --git a/openless-all/app/src/i18n/ja.ts b/openless-all/app/src/i18n/ja.ts
index 257bfb7f..0eceb288 100644
--- a/openless-all/app/src/i18n/ja.ts
+++ b/openless-all/app/src/i18n/ja.ts
@@ -684,8 +684,8 @@ export const ja: typeof zhCN = {
       comboRecorded: '記録済み',
       comboClear: 'クリア',
       comboConflict: 'このショートカットの組み合わせは使用できません',
-      allowNonTsfFallbackLabel: '非 TSF フォールバックを許可',
-      allowNonTsfFallbackDesc: 'Windows：TSF 入力が失敗した時は分割した Unicode SendInput を使い、それも失敗した場合はクリップボードへコピーします。',
+      allowNonTsfFallbackLabel: 'Unicode SendInput 入力を許可',
+      allowNonTsfFallbackDesc: 'Windows：既定で分割した Unicode SendInput を使い、失敗した場合はクリップボードへコピーします。',
       historyGroupTitle: '履歴とコンテキスト',
       historyRetentionLabel: '履歴保持期間（日）',
       historyRetentionDesc: '保持日数を超えた履歴は新規書き込み時に削除されます。0 = 時間で削除しない。',
@@ -849,7 +849,7 @@ export const ja: typeof zhCN = {
       hotkeyStarting: 'インストール中…',
       hotkeyFailed: '監視失敗',
       windowsImeLabel: 'Windows 入力メソッドバックエンド',
-      windowsImeDesc: '音声セッション中に OpenLess TSF IME へ一時的に切り替え、クリップボード入力の制限を回避します。',
+      windowsImeDesc: '任意の実験的 TSF IME バックエンドです。Windows では既定で Unicode SendInput を使い、プロセス内テキストサービスのハングを避けます。',
       windowsImeInstalled: 'インストール済み',
       windowsImeUnavailable: '利用不可',
       androidImeLabel: '入力メソッド (IME)',
@@ -878,9 +878,9 @@ export const ja: typeof zhCN = {
       androidOverlayCancelSwipeDirection: { up: '上へスワイプ', down: '下へスワイプ' },
       androidOverlayCancelSwipeDirectionHint: { up: '録音中に上へスワイプすると、文字起こしや挿入をせずにキャンセルします。', down: '録音中に下へスワイプすると、文字起こしや挿入をせずにキャンセルします。' },
       windowsIme: {
-        installed: 'インストール済み。音声入力時に OpenLess IME へ一時的に切り替えます。',
-        notInstalled: '未インストール。OpenLess は現在クリップボード / WM_PASTE フォールバックを使用しています。',
-        registrationBroken: '登録が破損しています。OpenLess IME を再インストールしてください。',
+        installed: '実験的 TSF バックエンドが登録されています。',
+        notInstalled: '未登録です。OpenLess は既定で Unicode SendInput を使用します。',
+        registrationBroken: '実験的 TSF 登録が破損しています。',
         notWindows: 'Windows のみ利用可能。',
       },
     },
diff --git a/openless-all/app/src/i18n/ko.ts b/openless-all/app/src/i18n/ko.ts
index 395f92e1..a060b840 100644
--- a/openless-all/app/src/i18n/ko.ts
+++ b/openless-all/app/src/i18n/ko.ts
@@ -684,8 +684,8 @@ export const ko: typeof zhCN = {
       comboRecorded: '녹화됨',
       comboClear: '지우기',
       comboConflict: '이 단축키 조합은 사용할 수 없습니다',
-      allowNonTsfFallbackLabel: '비 TSF 폴백 허용',
-      allowNonTsfFallbackDesc: 'Windows: TSF 입력이 실패하면 분할된 Unicode SendInput을 사용하고, 그래도 실패하면 텍스트를 클립보드에 복사합니다.',
+      allowNonTsfFallbackLabel: 'Unicode SendInput 입력 허용',
+      allowNonTsfFallbackDesc: 'Windows: 기본적으로 분할된 Unicode SendInput을 사용하고, 실패하면 텍스트를 클립보드에 복사합니다.',
       historyGroupTitle: '기록 및 컨텍스트',
       historyRetentionLabel: '기록 보관 기간(일)',
       historyRetentionDesc: '보관 기간을 초과한 기록은 새 항목 작성 시 정리됩니다. 0 = 시간 기반 정리 비활성화.',
@@ -849,7 +849,7 @@ export const ko: typeof zhCN = {
       hotkeyStarting: '설치 중…',
       hotkeyFailed: '감지 실패',
       windowsImeLabel: 'Windows 입력기 백엔드',
-      windowsImeDesc: '음성 세션 동안 OpenLess TSF 입력기로 일시적으로 전환하여 클립보드 입력 제한을 회피하기 위해 사용.',
+      windowsImeDesc: '선택적 실험용 TSF 입력기 백엔드입니다. Windows는 기본적으로 Unicode SendInput을 사용해 프로세스 내부 텍스트 서비스 멈춤을 피합니다.',
       windowsImeInstalled: '설치됨',
       windowsImeUnavailable: '사용 불가',
       androidImeLabel: '입력기 (IME)',
@@ -878,9 +878,9 @@ export const ko: typeof zhCN = {
       androidOverlayCancelSwipeDirection: { up: '위로 스와이프', down: '아래로 스와이프' },
       androidOverlayCancelSwipeDirectionHint: { up: '녹음 중 위로 밀면 전사와 삽입 없이 취소합니다.', down: '녹음 중 아래로 밀면 전사와 삽입 없이 취소합니다.' },
       windowsIme: {
-        installed: '설치됨. 음성 입력 시 OpenLess 입력기로 일시 전환됩니다.',
-        notInstalled: '설치되지 않음. OpenLess 는 현재 클립보드 / WM_PASTE 폴백을 사용합니다.',
-        registrationBroken: '등록이 손상되었습니다. OpenLess 입력기를 재설치하세요.',
+        installed: '실험용 TSF 백엔드가 등록되어 있습니다.',
+        notInstalled: '등록되지 않음. OpenLess는 기본적으로 Unicode SendInput을 사용합니다.',
+        registrationBroken: '실험용 TSF 등록이 손상되었습니다.',
         notWindows: 'Windows 만 사용 가능.',
       },
     },
diff --git a/openless-all/app/src/i18n/zh-CN.ts b/openless-all/app/src/i18n/zh-CN.ts
index 3147b416..6d5913a9 100644
--- a/openless-all/app/src/i18n/zh-CN.ts
+++ b/openless-all/app/src/i18n/zh-CN.ts
@@ -680,8 +680,8 @@ export const zhCN = {
       comboRecorded: '已录制',
       comboClear: '清除',
       comboConflict: '该快捷键组合不可用',
-      allowNonTsfFallbackLabel: '允许非 TSF 兜底',
-      allowNonTsfFallbackDesc: 'Windows：TSF 失败时使用分批 Unicode SendInput；如果仍失败，再复制到剪贴板。',
+      allowNonTsfFallbackLabel: '允许 Unicode SendInput 输入',
+      allowNonTsfFallbackDesc: 'Windows：默认使用分批 Unicode SendInput；如果失败，再复制到剪贴板。',
       historyGroupTitle: '历史与上下文',
       historyRetentionLabel: '历史保留天数',
       historyRetentionDesc: '超过保留天数的历史在写入新条目时被清理；0 = 不按时间清理。',
@@ -845,7 +845,7 @@ export const zhCN = {
       hotkeyStarting: '安装中…',
       hotkeyFailed: '监听失败',
       windowsImeLabel: 'Windows 输入法后端',
-      windowsImeDesc: '语音输入时临时切到 OpenLess TSF，绕过剪贴板限制。',
+      windowsImeDesc: '可选的实验性 TSF 输入法后端。Windows 默认使用 Unicode SendInput，避免进程内文本服务卡死。',
       windowsImeInstalled: '已安装',
       windowsImeUnavailable: '不可用',
       androidImeLabel: '输入法 (IME)',
@@ -908,9 +908,9 @@ export const zhCN = {
         down: '录音中向下滑取消本次听写，不转写、不插入。',
       },
       windowsIme: {
-        installed: '已安装，按需切到 OpenLess 输入法。',
-        notInstalled: '未安装，走剪贴板 / WM_PASTE 兜底。',
-        registrationBroken: '注册损坏，请重装 OpenLess 输入法。',
+        installed: '实验性 TSF 后端已注册。',
+        notInstalled: '未注册。OpenLess 默认使用 Unicode SendInput。',
+        registrationBroken: '实验性 TSF 注册已损坏。',
         notWindows: '仅 Windows 可用。',
       },
     },
diff --git a/openless-all/app/src/i18n/zh-TW.ts b/openless-all/app/src/i18n/zh-TW.ts
index 2fe58825..0e8e8c2b 100644
--- a/openless-all/app/src/i18n/zh-TW.ts
+++ b/openless-all/app/src/i18n/zh-TW.ts
@@ -682,8 +682,8 @@ export const zhTW: typeof zhCN = {
       pasteShortcutCtrlV: 'Ctrl+V（默認 / 多數應用）',
       pasteShortcutCtrlShiftV: 'Ctrl+Shift+V（kitty / alacritty / wezterm / 多數終端）',
       pasteShortcutShiftInsert: 'Shift+Insert（xterm / urxvt）',
-      allowNonTsfFallbackLabel: '允許非 TSF 兜底',
-      allowNonTsfFallbackDesc: 'Windows：TSF 失敗時使用分批 Unicode SendInput；如果仍失敗，再複製到剪貼簿。',
+      allowNonTsfFallbackLabel: '允許 Unicode SendInput 輸入',
+      allowNonTsfFallbackDesc: 'Windows：預設使用分批 Unicode SendInput；如果失敗，再複製到剪貼簿。',
       historyGroupTitle: '歷史與上下文',
       historyRetentionLabel: '歷史保留天數',
       historyRetentionDesc: '超過保留天數的歷史在寫入新條目時被清理；0 = 不按時間清理。',
@@ -847,7 +847,7 @@ export const zhTW: typeof zhCN = {
       hotkeyStarting: '安裝中…',
       hotkeyFailed: '監聽失敗',
       windowsImeLabel: 'Windows 輸入法後端',
-      windowsImeDesc: '用於在語音會話期間臨時切換到 OpenLess TSF 輸入法，避免剪貼板插入限制。',
+      windowsImeDesc: '可選的實驗性 TSF 輸入法後端。Windows 預設使用 Unicode SendInput，避免進程內文字服務卡死。',
       windowsImeInstalled: '已安裝',
       windowsImeUnavailable: '不可用',
       androidImeLabel: '輸入法 (IME)',
@@ -876,9 +876,9 @@ export const zhTW: typeof zhCN = {
       androidOverlayCancelSwipeDirection: { up: '向上滑', down: '向下滑' },
       androidOverlayCancelSwipeDirectionHint: { up: '錄音中向上滑取消本次聽寫，不轉寫、不插入。', down: '錄音中向下滑取消本次聽寫，不轉寫、不插入。' },
       windowsIme: {
-        installed: '已安裝。語音輸入時會臨時切換到 OpenLess 輸入法。',
-        notInstalled: '未安裝。OpenLess 正在使用剪貼板 / WM_PASTE 兜底。',
-        registrationBroken: '註冊已損壞。請重新安裝 OpenLess 輸入法。',
+        installed: '實驗性 TSF 後端已註冊。',
+        notInstalled: '未註冊。OpenLess 預設使用 Unicode SendInput。',
+        registrationBroken: '實驗性 TSF 註冊已損壞。',
         notWindows: '僅 Windows 可用。',
       },
     },
diff --git a/openless-all/app/src/lib/ipc/mock-data.ts b/openless-all/app/src/lib/ipc/mock-data.ts
index 402f8cc8..837e4e41 100644
--- a/openless-all/app/src/lib/ipc/mock-data.ts
+++ b/openless-all/app/src/lib/ipc/mock-data.ts
@@ -49,6 +49,7 @@ export let mockSettings: UserPreferences = {
     restoreClipboardAfterPaste: true,
     pasteShortcut: "ctrlV",
     allowNonTsfInsertionFallback: true,
+    windowsTsfBackendEnabled: false,
     workingLanguages: ["简体中文"],
     translationTargetLanguage: "",
     qaHotkey: defaultQaShortcut(),
diff --git a/openless-all/app/src/lib/stylePrefs.test.ts b/openless-all/app/src/lib/stylePrefs.test.ts
index d049a4a5..1692bba9 100644
--- a/openless-all/app/src/lib/stylePrefs.test.ts
+++ b/openless-all/app/src/lib/stylePrefs.test.ts
@@ -39,6 +39,7 @@ const previousPrefs: UserPreferences = {
   restoreClipboardAfterPaste: true,
   pasteShortcut: 'ctrlV',
   allowNonTsfInsertionFallback: true,
+  windowsTsfBackendEnabled: false,
   workingLanguages: ['简体中文'],
   translationTargetLanguage: '',
   chineseScriptPreference: 'auto',
diff --git a/openless-all/app/src/lib/types.ts b/openless-all/app/src/lib/types.ts
index fe8c8baa..4b8610f4 100644
--- a/openless-all/app/src/lib/types.ts
+++ b/openless-all/app/src/lib/types.ts
@@ -266,8 +266,9 @@ export interface UserPreferences {
    *  等终端只接受 Ctrl+Shift+V，硬编码 Ctrl+V 会被吞掉，听写文本只剩在剪贴板里。
    *  macOS 走 AX 直写不受影响。默认 'ctrlV' 与历史行为一致。 */
   pasteShortcut: PasteShortcut;
-  /** Windows：TSF 失败后是否允许快捷键粘贴 / 剪贴板兜底。仅在剪贴板写失败时才再试 SendInput。关闭后可验证是否真实 TSF 上屏。 */
+  /** Windows: allow paced Unicode SendInput insertion; if it fails, text is copied to the clipboard. */
   allowNonTsfInsertionFallback: boolean;
+  windowsTsfBackendEnabled: boolean;
   /** 用户的工作语言（多选，原生名）；作为前提注入 LLM polish/translate prompt 头部。 */
   workingLanguages: string[];
   /** 翻译模式目标语言（单选，原生名）；空串 = 不启用 Shift 翻译。详见 issue #4。 */
diff --git a/openless-all/app/windows-ime/src/dllmain.cpp b/openless-all/app/windows-ime/src/dllmain.cpp
index 624c79f7..da60c836 100644
--- a/openless-all/app/windows-ime/src/dllmain.cpp
+++ b/openless-all/app/windows-ime/src/dllmain.cpp
@@ -10,15 +10,49 @@ HINSTANCE g_module = nullptr;
 LONG g_lock_count = 0;
 LONG g_object_count = 0;
 
+namespace {
+
+bool IsBlockedShellProcess() {
+  wchar_t path[MAX_PATH] = {};
+  const DWORD length = GetModuleFileNameW(nullptr, path, ARRAYSIZE(path));
+  if (length == 0 || length >= ARRAYSIZE(path)) {
+    return false;
+  }
+
+  const wchar_t* name = path;
+  for (const wchar_t* cursor = path; *cursor != L'\0'; ++cursor) {
+    if (*cursor == L'\\' || *cursor == L'/') {
+      name = cursor + 1;
+    }
+  }
+
+  constexpr const wchar_t* kBlockedProcesses[] = {
+      L"explorer.exe",
+      L"searchhost.exe",
+      L"startmenuexperiencehost.exe",
+      L"shellexperiencehost.exe",
+      L"textinputhost.exe",
+  };
+  for (const wchar_t* blocked : kBlockedProcesses) {
+    if (_wcsicmp(name, blocked) == 0) {
+      return true;
+    }
+  }
+  return false;
+}
+
+}  // namespace
+
 BOOL APIENTRY DllMain(HINSTANCE instance, DWORD reason, LPVOID reserved) {
   UNREFERENCED_PARAMETER(reserved);
 
-  // 不调用 DisableThreadLibraryCalls：DLL 现在用 /MT 静态链接 CRT，CRT 需要
-  // DLL_THREAD_ATTACH / DLL_THREAD_DETACH 通知做 per-thread TLS 初始化与清理。
-  // 在 host 进程（如 QQ / Office）切输入法新建 input thread 时禁用通知，会让
-  // 静态 CRT 的 thread-local 资源泄漏 / 行为不稳定，反而把这次想修的崩溃问题
-  // 重新引回来。详见 Microsoft 文档 DisableThreadLibraryCalls 备注。
+  // Do not call DisableThreadLibraryCalls here. OpenLessIme is linked with the
+  // static CRT, and suppressing thread attach/detach callbacks can break CRT
+  // thread-local cleanup in host input processes.
   if (reason == DLL_PROCESS_ATTACH) {
+    if (IsBlockedShellProcess()) {
+      return FALSE;
+    }
     g_module = instance;
   }
 
@@ -39,6 +73,10 @@ STDAPI DllGetClassObject(REFCLSID clsid, REFIID iid, void** object) {
     return CLASS_E_CLASSNOTAVAILABLE;
   }
 
+  if (IsBlockedShellProcess()) {
+    return CLASS_E_CLASSNOTAVAILABLE;
+  }
+
   auto* factory = new (std::nothrow) OpenLessClassFactory();
   if (factory == nullptr) {
     return E_OUTOFMEMORY;
diff --git a/openless-all/app/windows-ime/src/text_service.cpp b/openless-all/app/windows-ime/src/text_service.cpp
index f303eac1..8e2ff348 100644
--- a/openless-all/app/windows-ime/src/text_service.cpp
+++ b/openless-all/app/windows-ime/src/text_service.cpp
@@ -41,6 +41,23 @@ HRESULT WaitForAsyncEditCompletion(
   return HRESULT_FROM_WIN32(GetLastError());
 }
 
+bool IsExplorerProcess() {
+  wchar_t path[MAX_PATH] = {};
+  const DWORD length = GetModuleFileNameW(nullptr, path, ARRAYSIZE(path));
+  if (length == 0 || length >= ARRAYSIZE(path)) {
+    return false;
+  }
+
+  const wchar_t* name = path;
+  for (const wchar_t* cursor = path; *cursor != L'\0'; ++cursor) {
+    if (*cursor == L'\\' || *cursor == L'/') {
+      name = cursor + 1;
+    }
+  }
+
+  return _wcsicmp(name, L"explorer.exe") == 0;
+}
+
 }  // namespace
 
 OpenLessTextService::OpenLessTextService() {
@@ -94,6 +111,11 @@ STDMETHODIMP OpenLessTextService::ActivateEx(ITfThreadMgr* thread_mgr,
     return E_INVALIDARG;
   }
 
+  if (IsExplorerProcess()) {
+    Deactivate();
+    return HRESULT_FROM_WIN32(ERROR_NOT_SUPPORTED);
+  }
+
   Deactivate();
 
   owner_thread_id_ = GetCurrentThreadId();