fix(cloud-files): Pin loest Hydration aus, Icon-Refresh via SHChangeNotify

CfSetPinState aendert nur das Pin-Flag - ohne expliziten Call
passiert am Disk-Inhalt nichts und das Explorer-Icon bleibt
unveraendert. Darum klickte "Immer offline verfuegbar" scheinbar
ins Leere.

- Bei Pin: CfHydratePlaceholder triggert FETCH_DATA und laedt die
  Datei komplett herunter
- Bei Unpin: CfDehydratePlaceholder (war schon da)
- Nach jeder Zustandsaenderung SHChangeNotify(SHCNE_UPDATEITEM)
  damit das Overlay-Icon sofort neu gezeichnet wird, ohne dass
  der User F5 druecken muss
- Log bekommt zusaetzlich hydrate_err fuer Debugging

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/app/api/files.py

@@ -1254,32 +1254,79 @@ def list_locks():
 @api_bp.route('/sync/tree', methods=['GET'])
 @token_required
 def sync_tree():
-    """Returns complete file tree with checksums for sync clients."""
+    """Returns complete file tree with checksums for sync clients.
+
+    Includes both files owned by the user (under 'tree') and files
+    shared WITH the user (as a virtual 'Geteilt mit mir' folder under
+    'shared'). The client merges both.
+    """
     user = request.current_user
 
+    def _entry(f):
+        entry = {
+            'id': f.id,
+            'name': f.name,
+            'is_folder': f.is_folder,
+            'size': f.size,
+            'checksum': f.checksum,
+            'updated_at': f.updated_at.isoformat() if f.updated_at else None,
+            'modified_at': f.updated_at.isoformat() if f.updated_at else None,
+        }
+        lock = FileLock.get_lock(f.id)
+        if lock:
+            entry['locked'] = True
+            entry['locked_by'] = lock.user.username
+        return entry
+
     def _build_tree(parent_id):
         files = File.query.filter_by(owner_id=user.id, parent_id=parent_id, is_trashed=False)\
             .order_by(File.is_folder.desc(), File.name).all()
         result = []
         for f in files:
-            entry = {
-                'id': f.id,
-                'name': f.name,
-                'is_folder': f.is_folder,
-                'size': f.size,
-                'checksum': f.checksum,
-                'updated_at': f.updated_at.isoformat() if f.updated_at else None,
-            }
-            lock = FileLock.get_lock(f.id)
-            if lock:
-                entry['locked'] = True
-                entry['locked_by'] = lock.user.username
+            e = _entry(f)
             if f.is_folder:
-                entry['children'] = _build_tree(f.id)
-            result.append(entry)
+                e['children'] = _build_tree(f.id)
+            result.append(e)
         return result
 
-    return jsonify({'tree': _build_tree(None)}), 200
+    def _build_shared_children(parent_id):
+        files = File.query.filter_by(parent_id=parent_id, is_trashed=False)\
+            .order_by(File.is_folder.desc(), File.name).all()
+        out = []
+        for f in files:
+            e = _entry(f)
+            if f.is_folder:
+                e['children'] = _build_shared_children(f.id)
+            out.append(e)
+        return out
+
+    shared_perms = FilePermission.query.filter_by(user_id=user.id).all()
+    shared_roots = []
+    seen = set()
+    for perm in shared_perms:
+        f = perm.file
+        if not f or f.is_trashed or f.id in seen:
+            continue
+        seen.add(f.id)
+        # Nur "Top-Level"-Shares: wenn der Eltern-Ordner NICHT auch geteilt
+        # ist, ist dieses Item die Wurzel des Shares beim Empfaenger.
+        parent_shared = any(
+            p.file_id == f.parent_id for p in shared_perms
+        ) if f.parent_id else False
+        if parent_shared:
+            continue
+        e = _entry(f)
+        owner = f.owner.display_name if hasattr(f, 'owner') and f.owner else None
+        if owner:
+            e['name'] = f'{f.name} (von {owner})'
+        if f.is_folder:
+            e['children'] = _build_shared_children(f.id)
+        shared_roots.append(e)
+
+    return jsonify({
+        'tree': _build_tree(None),
+        'shared': shared_roots,
+    }), 200
 
 
 @api_bp.route('/sync/events', methods=['GET'])

clients/desktop/CLOUD_FILES.md

@@ -0,0 +1,70 @@
+# Native File-Provider-Integration (Platzhalter-Modus)
+
+Zusaetzlich zum klassischen "alles-kopieren"-Sync bietet der Desktop-Client
+einen **OneDrive-aehnlichen Platzhalter-Modus**: Dateien erscheinen im
+Dateimanager als kleine Metadata-Dateien (Platzhalter) und werden erst
+bei Doppelklick vom Server geladen.
+
+## Status
+
+| Plattform | Status    | Technologie                          |
+| --------- | --------- | ------------------------------------ |
+| Windows   | **MVP**   | Cloud Files API (`cfapi.dll`)        |
+| Linux     | Skelett   | FUSE (libfuse3) - feature `linux_fuse` |
+| macOS     | Geplant   | `NSFileProviderExtension` + Signatur |
+
+## Windows
+
+### Voraussetzungen
+
+- Windows 10 1709 (Build 16299) oder neuer
+- Der Client laeuft als regulaerer Benutzerprozess (keine Admin-Rechte noetig)
+
+### Was funktioniert
+
+- `CfRegisterSyncRoot` registriert einen Ordner als Sync-Root, der Explorer
+  zeigt Wolken-Overlay-Icons an.
+- `CfCreatePlaceholders` legt fuer jede Mini-Cloud-Datei einen Platzhalter
+  mit korrekter Groesse und Aenderungszeit an.
+- `FETCH_DATA`-Callback laedt per Range-Request vom Server, sobald der
+  Explorer Dateidaten anfordert (z.B. beim Oeffnen).
+- `CfSetPinState` erlaubt manuelles "Immer offline halten" / "Nur in Cloud".
+
+### Was noch fehlt
+
+- Upload-Callback (`NOTIFY_FILE_CLOSE_COMPLETION`) fuer lokal geaenderte Dateien
+- Context-Menue "Ein-/Auschecken" via Shell-Extension
+- Delta-Updates (neue/geloeschte Dateien auf dem Server -> lokale Placeholder)
+- Konflikt-Aufloesung
+
+### Einschalten
+
+Im Client-UI den Schalter **"Cloud-Files-Modus"** aktivieren (ruft intern
+`cloud_files_enable`-Command auf). Alternativ per Kommandozeile beim Build:
+
+```powershell
+# Aus clients/desktop/src-tauri:
+cargo build --release
+```
+
+Windows-Targets brauchen das Windows-SDK (uebersetzt aber sauber mit
+cross-compile via `cargo xwin` aus Linux, wenn `build.sh windows` laeuft).
+
+## Linux
+
+FUSE-Provider ist optional und mit einem Feature-Flag versehen, damit
+normale Linux-Builds nicht `libfuse3-dev` voraussetzen:
+
+```bash
+cargo build --features linux_fuse
+```
+
+Overlay-Icons im Dateimanager (Nautilus / Dolphin / Caja) brauchen
+zusaetzlich eine native Extension pro DE - folgt in einem spaeteren
+Commit.
+
+## macOS
+
+Braucht eine Apple Developer ID + Notarization, da `NSFileProviderExtension`
+sonst vom Finder nicht geladen wird. Wird angegangen, sobald ein
+Apple-Dev-Zugang verfuegbar ist.

clients/desktop/src-tauri/Cargo.toml

@@ -19,7 +19,7 @@ tauri-plugin-dialog = "2"
 tauri-plugin-notification = "2"
 serde = { version = "1", features = ["derive"] }
 serde_json = "1"
-reqwest = { version = "0.12", features = ["json", "multipart", "rustls-tls"], default-features = false }
+reqwest = { version = "0.12", features = ["json", "multipart", "rustls-tls", "blocking"], default-features = false }
 tokio = { version = "1", features = ["full"] }
 notify = "7"
 sha2 = "0.10"
@@ -28,3 +28,30 @@ rusqlite = { version = "0.34", features = ["bundled"] }
 chrono = { version = "0.4", features = ["serde"] }
 base64 = "0.22"
 open = "5"
+once_cell = "1"
+
+# Plattform-spezifische File-Provider-Integration (OneDrive-artig).
+# Nur auf Windows gegen die Cloud Files API (cfapi.dll) linken.
+[target.'cfg(windows)'.dependencies]
+windows = { version = "0.58", features = [
+    "Win32_Foundation",
+    "Win32_Storage_FileSystem",
+    "Win32_Storage_CloudFilters",
+    "Win32_System_IO",
+    "Win32_System_Com",
+    "Win32_System_CorrelationVector",  # gate fuer CF_CALLBACK_INFO / CfExecute / CfConnectSyncRoot
+    "Win32_UI_Shell",
+    "Win32_Security",
+    "Win32_System_Registry",
+] }
+widestring = "1"
+winreg = "0.52"
+
+# Linux: FUSE-basiertes Virtual-Filesystem (optional, cargo build --features linux_fuse)
+[target.'cfg(target_os = "linux")'.dependencies]
+fuser = { version = "0.15", optional = true }
+libc = "0.2"
+
+[features]
+default = []
+linux_fuse = ["fuser"]

clients/desktop/src-tauri/src/cloud_files/linux.rs

@@ -0,0 +1,25 @@
+//! Linux FUSE-basierte File-Provider-Integration (Platzhalter-Modus).
+//!
+//! Status: Skelett. Funktioniert nur wenn mit `--features linux_fuse`
+//! gebaut wird und `libfuse3-dev` installiert ist. Overlay-Icons im
+//! Dateimanager (Nautilus/Dolphin) werden spaeter als separate Extension
+//! nachgereicht - das FUSE-Filesystem selbst kann die nicht setzen.
+
+#![cfg(all(target_os = "linux", feature = "linux_fuse"))]
+
+use super::RemoteEntry;
+use std::path::PathBuf;
+
+pub fn mount(mount_point: &PathBuf) -> Result<(), String> {
+    std::fs::create_dir_all(mount_point).map_err(|e| e.to_string())?;
+    // TODO: fuser::Filesystem-Impl mit auf-Abruf-Download
+    Err("Linux FUSE-Provider: noch nicht implementiert (MVP folgt)".into())
+}
+
+pub fn unmount(_mount_point: &PathBuf) -> Result<(), String> {
+    Err("Linux FUSE-Provider: noch nicht implementiert".into())
+}
+
+pub fn populate(_mount_point: &PathBuf, _entries: &[RemoteEntry]) -> Result<(), String> {
+    Err("Linux FUSE-Provider: noch nicht implementiert".into())
+}

clients/desktop/src-tauri/src/cloud_files/mod.rs

@@ -0,0 +1,121 @@
+//! Native File-Provider-Integration (Platzhalter-Dateien wie bei OneDrive).
+//!
+//! Auf Windows realisiert ueber die Cloud Files API (cfapi.dll), auf Linux
+//! ueber FUSE (optional, hinter `linux_fuse`-Feature). macOS folgt spaeter
+//! ueber NSFileProviderExtension (braucht Apple-Signatur).
+//!
+//! Der bestehende `sync::engine` bleibt unberuehrt und bietet weiterhin
+//! den klassischen "kopiere-alles-lokal"-Modus. Der Cloud-Files-Modus
+//! ist sozusagen "files-on-demand": Datei wird erst bei Zugriff geladen.
+
+use serde::{Deserialize, Serialize};
+use std::path::PathBuf;
+
+/// Ein Eintrag aus dem Mini-Cloud-Syncbaum, so wie er vom Server kommt.
+/// Wird von beiden Plattformen genutzt, um Platzhalter / FUSE-Inodes zu
+/// erzeugen.
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct RemoteEntry {
+    pub id: i64,
+    pub name: String,
+    pub parent_id: Option<i64>,
+    pub is_folder: bool,
+    pub size: i64,
+    /// UTC-ISO8601
+    pub modified_at: String,
+    /// SHA-256 falls vom Server ausgeliefert, sonst None.
+    pub checksum: Option<String>,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum SyncState {
+    /// Datei existiert nur als Platzhalter (online-only).
+    Cloud,
+    /// Datei ist vollstaendig lokal vorhanden und aktuell.
+    InSync,
+    /// Lokal geaendert, Upload ausstehend.
+    PendingUpload,
+    /// Auf dem Server gesperrt (durch anderen Nutzer).
+    LockedByOther,
+    /// Durch diesen Client gesperrt.
+    LockedLocal,
+}
+
+#[cfg(windows)]
+pub mod windows;
+#[cfg(windows)]
+pub mod shell_integration;
+#[cfg(all(target_os = "linux", feature = "linux_fuse"))]
+pub mod linux;
+pub mod sync_loop;
+pub mod watcher;
+
+/// Registriere den Sync-Root beim Betriebssystem. Ruft je nach Plattform
+/// cfapi/CfRegisterSyncRoot bzw. mountet ein FUSE-Dateisystem.
+#[allow(unused_variables)]
+pub fn register_sync_root(
+    mount_point: &PathBuf,
+    provider_name: &str,
+    account_id: &str,
+) -> Result<(), String> {
+    #[cfg(windows)]
+    return windows::register_sync_root(mount_point, provider_name, account_id);
+
+    #[cfg(all(target_os = "linux", feature = "linux_fuse"))]
+    return linux::mount(mount_point);
+
+    #[cfg(not(any(windows, all(target_os = "linux", feature = "linux_fuse"))))]
+    Err("File-Provider-Integration fuer diese Plattform noch nicht verfuegbar".into())
+}
+
+#[allow(unused_variables)]
+pub fn unregister_sync_root(mount_point: &PathBuf) -> Result<(), String> {
+    #[cfg(windows)]
+    return windows::unregister_sync_root(mount_point);
+
+    #[cfg(all(target_os = "linux", feature = "linux_fuse"))]
+    return linux::unmount(mount_point);
+
+    #[cfg(not(any(windows, all(target_os = "linux", feature = "linux_fuse"))))]
+    Err("File-Provider-Integration fuer diese Plattform noch nicht verfuegbar".into())
+}
+
+/// Erzeuge fuer alle Remote-Eintraege Platzhalter (cloud-only Dateien).
+/// Ordner werden als echte Verzeichnisse angelegt, Dateien als
+/// Platzhalter mit gespeicherten Metadaten (Groesse, Mtime, ID).
+#[allow(unused_variables)]
+pub fn populate_placeholders(
+    mount_point: &PathBuf,
+    entries: &[RemoteEntry],
+) -> Result<(), String> {
+    #[cfg(windows)]
+    return windows::populate_placeholders(mount_point, entries);
+
+    #[cfg(all(target_os = "linux", feature = "linux_fuse"))]
+    return linux::populate(mount_point, entries);
+
+    #[cfg(not(any(windows, all(target_os = "linux", feature = "linux_fuse"))))]
+    Err("File-Provider-Integration fuer diese Plattform noch nicht verfuegbar".into())
+}
+
+/// Ist File-Provider-Integration auf dieser Plattform grundsaetzlich verfuegbar?
+pub fn is_supported() -> bool {
+    cfg!(windows) || cfg!(all(target_os = "linux", feature = "linux_fuse"))
+}
+
+/// Markiere eine lokal bereits vorhandene Datei als "immer offline halten".
+#[allow(unused_variables)]
+pub fn pin_file(path: &PathBuf) -> Result<(), String> {
+    #[cfg(windows)]
+    return windows::set_pin_state(path, true);
+    #[cfg(not(windows))]
+    Err("Nur auf Windows unterstuetzt".into())
+}
+
+#[allow(unused_variables)]
+pub fn unpin_file(path: &PathBuf) -> Result<(), String> {
+    #[cfg(windows)]
+    return windows::set_pin_state(path, false);
+    #[cfg(not(windows))]
+    Err("Nur auf Windows unterstuetzt".into())
+}

clients/desktop/src-tauri/src/cloud_files/shell_integration.rs

@@ -0,0 +1,206 @@
+//! Explorer-Sidebar-Integration fuer Windows (ohne Admin-Rechte).
+//!
+//! Registriert den Sync-Ordner als Shell-Namespace-Extension unter
+//! HKEY_CURRENT_USER, sodass er mit eigenem Icon in der Navigation
+//! des Datei-Explorers erscheint (wie OneDrive/Dropbox).
+//!
+//! Anders als die eigentliche Cloud Files API ist das reine Registry-
+//! Kosmetik - der Ordner funktioniert auch ohne Sidebar-Eintrag,
+//! nur sieht man ihn dann nicht in der linken Leiste.
+
+#![cfg(windows)]
+
+use std::path::Path;
+use winreg::enums::*;
+use winreg::RegKey;
+
+// Stabile GUID fuer Mini-Cloud - gleiche wie in windows.rs als ProviderId.
+const CLSID_GUID: &str = "{4D696E69-436C-6F75-6444-7566667944AB}";
+
+// Standard-CLSID fuer "Generic Shell Folder Implementation".
+const SHELL_FOLDER_CLSID: &str = "{0E5AAE11-A475-4c5b-AB00-C66DE400274E}";
+
+/// Registriere den Mount-Ordner in der Explorer-Navigation.
+/// `icon_source`: Pfad zu ICO oder EXE mit Icon-Index (z.B. "C:\\app.exe,0")
+pub fn install(
+    display_name: &str,
+    mount_point: &Path,
+    icon_source: &str,
+) -> Result<(), String> {
+    let hkcu = RegKey::predef(HKEY_CURRENT_USER);
+
+    // 1) CLSID-Eintrag unter Software\Classes\CLSID\{GUID}
+    let clsid_path = format!("Software\\Classes\\CLSID\\{}", CLSID_GUID);
+    let (clsid, _) = hkcu
+        .create_subkey(&clsid_path)
+        .map_err(|e| format!("create CLSID: {e}"))?;
+    clsid
+        .set_value("", &display_name.to_string())
+        .map_err(|e| format!("set displayname: {e}"))?;
+    clsid
+        .set_value("System.IsPinnedToNameSpaceTree", &1u32)
+        .map_err(|e| format!("set pinned: {e}"))?;
+    clsid
+        .set_value("SortOrderIndex", &0x42u32)
+        .map_err(|e| format!("set sortorder: {e}"))?;
+
+    // 2) DefaultIcon
+    let (icon_key, _) = clsid
+        .create_subkey("DefaultIcon")
+        .map_err(|e| format!("create DefaultIcon: {e}"))?;
+    icon_key
+        .set_value("", &icon_source.to_string())
+        .map_err(|e| format!("set icon: {e}"))?;
+
+    // 3) InProcServer32 -> shell32.dll (Standard Shell-Folder-Host)
+    let (inproc, _) = clsid
+        .create_subkey("InProcServer32")
+        .map_err(|e| format!("create InProcServer32: {e}"))?;
+    inproc
+        .set_value("", &"%SystemRoot%\\system32\\shell32.dll".to_string())
+        .map_err(|e| format!("set shell32: {e}"))?;
+    inproc
+        .set_value("ThreadingModel", &"Both".to_string())
+        .map_err(|e| format!("set threading: {e}"))?;
+
+    // 4) Instance -> zeigt auf generischen Shell-Folder
+    let (instance, _) = clsid
+        .create_subkey("Instance")
+        .map_err(|e| format!("create Instance: {e}"))?;
+    instance
+        .set_value("CLSID", &SHELL_FOLDER_CLSID.to_string())
+        .map_err(|e| format!("set inst clsid: {e}"))?;
+
+    let (pb, _) = instance
+        .create_subkey("InitPropertyBag")
+        .map_err(|e| format!("create InitPropertyBag: {e}"))?;
+    pb.set_value("Attributes", &0x11u32)
+        .map_err(|e| format!("set attrs pb: {e}"))?;
+    pb.set_value(
+        "TargetFolderPath",
+        &mount_point.to_string_lossy().into_owned(),
+    )
+    .map_err(|e| format!("set target: {e}"))?;
+
+    // 5) ShellFolder-Flags
+    let (sf, _) = clsid
+        .create_subkey("ShellFolder")
+        .map_err(|e| format!("create ShellFolder: {e}"))?;
+    sf.set_value("FolderValueFlags", &0x28u32)
+        .map_err(|e| format!("set folderflags: {e}"))?;
+    sf.set_value("Attributes", &0xF080004Du32)
+        .map_err(|e| format!("set attrs sf: {e}"))?;
+
+    // 6) In die Navigation einhaengen
+    let ns_path = format!(
+        "Software\\Microsoft\\Windows\\CurrentVersion\\Explorer\\Desktop\\NameSpace\\{}",
+        CLSID_GUID
+    );
+    let (ns, _) = hkcu
+        .create_subkey(&ns_path)
+        .map_err(|e| format!("create NameSpace: {e}"))?;
+    ns.set_value("", &display_name.to_string())
+        .map_err(|e| format!("set ns name: {e}"))?;
+
+    // 7) Kontext-Menue-Verben (Rechtsklick) fuer Dateien unter dem Mount
+    install_context_menu(mount_point)?;
+
+    // 8) Explorer informieren (SHChangeNotify)
+    notify_shell();
+
+    Ok(())
+}
+
+/// Registriert "Immer offline halten" / "Speicher freigeben" als
+/// Rechtsklick-Menuepunkte, die nur fuer Dateien unterhalb des Mounts
+/// angezeigt werden (AppliesTo-Filter).
+fn install_context_menu(mount_point: &Path) -> Result<(), String> {
+    let hkcu = RegKey::predef(HKEY_CURRENT_USER);
+    let exe = std::env::current_exe()
+        .map_err(|e| format!("current_exe: {e}"))?
+        .to_string_lossy()
+        .into_owned();
+    // Trailing Backslash wegstrippen, dann eine saubere AQS-Query bauen.
+    // Registry-Werte sind normale Strings; Backslashes bleiben einfach.
+    let mount_clean = mount_point
+        .to_string_lossy()
+        .trim_end_matches('\\')
+        .to_string();
+    // AppliesTo: nur Dateien, deren Pfad mit dem Mount-Ordner beginnt.
+    let applies_to = format!("System.ItemPathDisplay:~< \"{}\"", mount_clean);
+
+    for (verb, label, flag) in [
+        ("MiniCloudPin", "Immer offline verfuegbar", "--pin"),
+        ("MiniCloudUnpin", "Speicher freigeben", "--unpin"),
+    ] {
+        // Unter AllFilesystemObjects statt * - das greift auch fuer
+        // Ordner und vermeidet Konflikte mit Dateityp-spezifischen Verben.
+        let key_path = format!("Software\\Classes\\AllFilesystemObjects\\shell\\{}", verb);
+        let (k, _) = hkcu
+            .create_subkey(&key_path)
+            .map_err(|e| format!("verb {verb}: {e}"))?;
+        k.set_value("", &label.to_string())
+            .map_err(|e| format!("default: {e}"))?;
+        k.set_value("MUIVerb", &label.to_string())
+            .map_err(|e| format!("MUIVerb: {e}"))?;
+        k.set_value("AppliesTo", &applies_to)
+            .map_err(|e| format!("AppliesTo: {e}"))?;
+        k.set_value("Icon", &exe)
+            .map_err(|e| format!("Icon: {e}"))?;
+
+        let (cmd, _) = k
+            .create_subkey("command")
+            .map_err(|e| format!("cmd: {e}"))?;
+        cmd.set_value("", &format!("\"{}\" {} \"%1\"", exe, flag))
+            .map_err(|e| format!("cmdline: {e}"))?;
+    }
+    Ok(())
+}
+
+fn uninstall_context_menu() {
+    let hkcu = RegKey::predef(HKEY_CURRENT_USER);
+    for verb in ["MiniCloudPin", "MiniCloudUnpin"] {
+        // alte (falsche) Stelle ebenfalls aufraeumen
+        let _ = hkcu.delete_subkey_all(format!("Software\\Classes\\*\\shell\\{}", verb));
+        let _ = hkcu.delete_subkey_all(format!(
+            "Software\\Classes\\AllFilesystemObjects\\shell\\{}",
+            verb
+        ));
+    }
+}
+
+/// Entferne die Shell-Integration wieder.
+pub fn uninstall() -> Result<(), String> {
+    let hkcu = RegKey::predef(HKEY_CURRENT_USER);
+
+    let ns_path = format!(
+        "Software\\Microsoft\\Windows\\CurrentVersion\\Explorer\\Desktop\\NameSpace\\{}",
+        CLSID_GUID
+    );
+    let _ = hkcu.delete_subkey_all(&ns_path);
+
+    let clsid_path = format!("Software\\Classes\\CLSID\\{}", CLSID_GUID);
+    let _ = hkcu.delete_subkey_all(&clsid_path);
+
+    uninstall_context_menu();
+
+    notify_shell();
+    Ok(())
+}
+
+/// Teilt Explorer mit, dass sich die Shell-Namespace-Liste geaendert hat.
+/// Ohne das sieht man den neuen Eintrag erst nach Explorer-Neustart.
+fn notify_shell() {
+    use windows::Win32::UI::Shell::{SHChangeNotify, SHCNE_ASSOCCHANGED, SHCNF_IDLIST};
+    unsafe {
+        SHChangeNotify(SHCNE_ASSOCCHANGED, SHCNF_IDLIST, None, None);
+    }
+}
+
+/// Standard-Icon-Quelle: die laufende .exe mit Index 0.
+pub fn default_icon_source() -> String {
+    std::env::current_exe()
+        .ok()
+        .and_then(|p| p.to_str().map(|s| format!("{},0", s)))
+        .unwrap_or_else(|| "%SystemRoot%\\system32\\imageres.dll,2".to_string())
+}

clients/desktop/src-tauri/src/cloud_files/sync_loop.rs

@@ -0,0 +1,221 @@
+//! Hintergrund-Synchronisation fuer den Cloud-Files-Modus.
+//!
+//! Zwei Aufgaben:
+//! 1. Lokale Aenderungen im Mount-Point beobachten (notify-Watcher) und
+//!    geaenderte Dateien hochladen. Neu angelegte Dateien werden als
+//!    neue Datei beim Server registriert und als Platzhalter markiert.
+//! 2. Serverseitige Aenderungen pollen (/api/sync/changes?since=...) und
+//!    fehlende Platzhalter erzeugen bzw. entfernte loeschen.
+//!
+//! Der Loop laeuft in einem dedizierten Tokio-Task; ein gespeicherter
+//! `Stop`-Channel beendet ihn sauber beim Deaktivieren.
+
+use super::RemoteEntry;
+use serde::Deserialize;
+use std::path::PathBuf;
+use std::sync::atomic::{AtomicBool, Ordering};
+use std::sync::Arc;
+use std::time::Duration;
+use tokio::sync::mpsc;
+
+#[derive(Clone)]
+pub struct SyncLoopConfig {
+    pub server_url: String,
+    pub access_token: String,
+    pub mount_point: PathBuf,
+    pub poll_interval_secs: u64,
+}
+
+pub struct SyncLoopHandle {
+    pub stop_flag: Arc<AtomicBool>,
+    pub tx: mpsc::UnboundedSender<LoopMessage>,
+}
+
+pub enum LoopMessage {
+    LocalChange(PathBuf),
+    Shutdown,
+}
+
+/// Starte den Sync-Loop. Gibt einen Handle zurueck, mit dem man ihn
+/// stoppen oder externe Events (z.B. vom Watcher) einspeisen kann.
+pub fn start(cfg: SyncLoopConfig) -> SyncLoopHandle {
+    let stop_flag = Arc::new(AtomicBool::new(false));
+    let (tx, mut rx) = mpsc::unbounded_channel::<LoopMessage>();
+    let stop = stop_flag.clone();
+    let cfg_task = cfg.clone();
+    tokio::spawn(async move {
+        let client = reqwest::Client::new();
+        let mut since: Option<String> = None;
+        let mut interval = tokio::time::interval(Duration::from_secs(cfg_task.poll_interval_secs));
+        loop {
+            if stop.load(Ordering::Relaxed) {
+                break;
+            }
+            tokio::select! {
+                _ = interval.tick() => {
+                    if let Err(e) = poll_server_changes(&client, &cfg_task, &mut since).await {
+                        eprintln!("[cloud_files] poll error: {e}");
+                    }
+                }
+                Some(msg) = rx.recv() => {
+                    match msg {
+                        LoopMessage::Shutdown => break,
+                        LoopMessage::LocalChange(path) => {
+                            if let Err(e) = upload_local_change(&client, &cfg_task, &path).await {
+                                eprintln!("[cloud_files] upload error: {e}");
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    });
+    SyncLoopHandle { stop_flag, tx }
+}
+
+#[derive(Debug, Deserialize)]
+struct ChangesResponse {
+    #[serde(default)]
+    created: Vec<RemoteEntry>,
+    #[serde(default)]
+    updated: Vec<RemoteEntry>,
+    #[serde(default)]
+    deleted: Vec<i64>,
+    timestamp: Option<String>,
+}
+
+async fn poll_server_changes(
+    client: &reqwest::Client,
+    cfg: &SyncLoopConfig,
+    since: &mut Option<String>,
+) -> Result<(), String> {
+    let base = cfg.server_url.trim_end_matches('/');
+    let mut url = format!("{}/api/sync/changes", base);
+    if let Some(s) = since.as_deref() {
+        url.push_str(&format!("?since={}", urlencode(s)));
+    }
+    let resp = client
+        .get(&url)
+        .bearer_auth(&cfg.access_token)
+        .send()
+        .await
+        .map_err(|e| e.to_string())?;
+    if !resp.status().is_success() {
+        return Err(format!("HTTP {}", resp.status()));
+    }
+    let body: ChangesResponse = resp.json().await.map_err(|e| e.to_string())?;
+
+    // Created + Updated: jeweils passendes Verzeichnis sichern, dann
+    // Platzhalter (neu) anlegen. Bei Updates muss der alte Platzhalter
+    // erst geloescht werden - Windows erlaubt kein "replace in place".
+    for e in body.created.iter().chain(body.updated.iter()) {
+        let rel = build_relative_path(e);
+        let full = cfg.mount_point.join(&rel);
+        if e.is_folder {
+            let _ = std::fs::create_dir_all(&full);
+            continue;
+        }
+        let parent = full.parent().map(|p| p.to_path_buf()).unwrap_or_else(|| cfg.mount_point.clone());
+        let _ = std::fs::create_dir_all(&parent);
+        let _ = std::fs::remove_file(&full); // ignoriert falls nicht da
+        #[cfg(windows)]
+        {
+            let identity = e.id.to_string();
+            if let Err(err) = super::windows::create_placeholder_at(
+                &parent,
+                &e.name,
+                e.size,
+                &e.modified_at,
+                identity.as_bytes(),
+            ) {
+                eprintln!("[cloud_files] placeholder {}: {}", e.name, err);
+            }
+        }
+    }
+
+    // Deleted: nur per ID vom Server - wir kennen den Pfad nicht mehr.
+    // MVP: ignorieren. In Version 2 fuehren wir ein lokales Mapping.
+    let _ = body.deleted;
+
+    if let Some(ts) = body.timestamp {
+        *since = Some(ts);
+    }
+    Ok(())
+}
+
+async fn upload_local_change(
+    client: &reqwest::Client,
+    cfg: &SyncLoopConfig,
+    path: &PathBuf,
+) -> Result<(), String> {
+    if !path.is_file() {
+        return Ok(());
+    }
+    // cfapi-Platzhalter oder gerade hydrierende Dateien NICHT hochladen -
+    // sonst wird jede Wolken-Datei sofort komplett gesynct und wir haben
+    // keinen On-Demand-Modus mehr.
+    #[cfg(windows)]
+    {
+        if super::windows::is_cfapi_placeholder(path) {
+            super::windows::log_msg(
+                &cfg.mount_point,
+                &format!("skip upload (placeholder): {}", path.display()),
+            );
+            return Ok(());
+        }
+    }
+    // Eigene Log-Datei nicht mit hochladen.
+    if path
+        .file_name()
+        .and_then(|n| n.to_str())
+        .map(|n| n.starts_with(".minicloud-"))
+        .unwrap_or(false)
+    {
+        return Ok(());
+    }
+    // Relativer Pfad im Mount = Ziel-Pfad auf Server
+    let rel = path
+        .strip_prefix(&cfg.mount_point)
+        .map_err(|_| "path outside mount".to_string())?
+        .to_string_lossy()
+        .replace('\\', "/");
+    let bytes = std::fs::read(path).map_err(|e| e.to_string())?;
+    let base = cfg.server_url.trim_end_matches('/');
+    let url = format!("{}/api/files/upload", base);
+    let file_name = path
+        .file_name()
+        .and_then(|s| s.to_str())
+        .unwrap_or("unnamed")
+        .to_string();
+    let form = reqwest::multipart::Form::new()
+        .text("path", rel.clone())
+        .part(
+            "file",
+            reqwest::multipart::Part::bytes(bytes).file_name(file_name),
+        );
+    let resp = client
+        .post(&url)
+        .bearer_auth(&cfg.access_token)
+        .multipart(form)
+        .send()
+        .await
+        .map_err(|e| e.to_string())?;
+    if !resp.status().is_success() {
+        return Err(format!("HTTP {}", resp.status()));
+    }
+    Ok(())
+}
+
+fn build_relative_path(e: &RemoteEntry) -> PathBuf {
+    // Achtung: RemoteEntry hat nur parent_id, nicht den kompletten Pfad.
+    // Fuer diesen einfachen Fall nehmen wir nur den Namen. Bei geschachtelten
+    // Ordnern muesste man die Hierarchie ueber /api/sync/tree vor-laden -
+    // das passiert einmal beim Aktivieren; Delta-Updates kommen meistens
+    // flach (oder in einer gemeinsamen Wurzel).
+    PathBuf::from(&e.name)
+}
+
+fn urlencode(s: &str) -> String {
+    // Sehr minimalistisch: wir ersetzen nur problematische Zeichen.
+    s.replace(' ', "%20").replace(':', "%3A").replace('+', "%2B")
+}

clients/desktop/src-tauri/src/cloud_files/watcher.rs

@@ -0,0 +1,43 @@
+//! Leichtgewichtiger Callback-basierter FS-Watcher fuer den Cloud-Files-Modus.
+//!
+//! Anders als `sync::watcher::FileWatcher` gibt dieser hier einen Closure
+//! direkt an notify weiter, sodass wir kein Channel-Pumpen brauchen.
+
+use notify::{Event, EventKind, RecommendedWatcher, RecursiveMode, Watcher, Config};
+use std::path::{Path, PathBuf};
+
+pub struct CallbackWatcher {
+    _watcher: RecommendedWatcher,
+}
+
+impl CallbackWatcher {
+    pub fn new<F>(watch_dir: &Path, mut on_change: F) -> Result<Self, String>
+    where
+        F: FnMut(PathBuf, EventKind) + Send + 'static,
+    {
+        let mut watcher = RecommendedWatcher::new(
+            move |res: Result<Event, notify::Error>| {
+                if let Ok(ev) = res {
+                    for path in ev.paths {
+                        let name = path.file_name().and_then(|n| n.to_str()).unwrap_or("");
+                        if name.starts_with('.')
+                            || name.starts_with('~')
+                            || name.ends_with(".tmp")
+                        {
+                            continue;
+                        }
+                        on_change(path, ev.kind.clone());
+                    }
+                }
+            },
+            Config::default(),
+        )
+        .map_err(|e| format!("Watcher-Fehler: {e}"))?;
+
+        watcher
+            .watch(watch_dir, RecursiveMode::Recursive)
+            .map_err(|e| format!("Watch-Fehler: {e}"))?;
+
+        Ok(Self { _watcher: watcher })
+    }
+}

clients/desktop/src-tauri/src/cloud_files/windows.rs

@@ -0,0 +1,639 @@
+//! Windows Cloud Files API Integration.
+//!
+//! Registriert den Sync-Ordner als Sync-Root, legt Platzhalter-Dateien an
+//! und reicht Zugriffe auf Dateidaten als HTTPS-Download durch. Der
+//! Explorer zeigt Wolken-/Haken-Overlays automatisch an, solange die
+//! Pin-Stati korrekt gesetzt sind.
+//!
+//! Voraussetzung: Windows 10 1709+ (cfapi.dll). Der Account-Identifier
+//! sollte stabil sein (z.B. Hash(Server-URL + Username)).
+
+#![cfg(windows)]
+
+use super::RemoteEntry;
+use once_cell::sync::Lazy;
+use std::path::{Path, PathBuf};
+use std::ptr;
+use std::sync::{Arc, Mutex};
+use widestring::U16CString;
+
+use windows::core::PCWSTR;
+use windows::Win32::Storage::CloudFilters as CF;
+use windows::Win32::Storage::FileSystem::FILE_ATTRIBUTE_NORMAL;
+use windows::Win32::System::Com::{CoInitializeEx, COINIT_MULTITHREADED};
+
+#[derive(Default, Clone)]
+pub struct CloudContext {
+    pub server_url: String,
+    pub access_token: String,
+    pub mount_point: PathBuf,
+}
+
+static CONTEXT: Lazy<Arc<Mutex<CloudContext>>> =
+    Lazy::new(|| Arc::new(Mutex::new(CloudContext::default())));
+
+static CONNECTION_KEY: Lazy<Mutex<Option<CF::CF_CONNECTION_KEY>>> =
+    Lazy::new(|| Mutex::new(None));
+
+pub fn set_context(server_url: String, access_token: String, mount_point: PathBuf) {
+    let mut ctx = CONTEXT.lock().unwrap();
+    ctx.server_url = server_url;
+    ctx.access_token = access_token;
+    ctx.mount_point = mount_point;
+}
+
+fn ctx_snapshot() -> CloudContext {
+    CONTEXT.lock().unwrap().clone()
+}
+
+const PROVIDER_VERSION: &str = "1.0";
+
+// Windows-FILETIME: 100ns-Ticks seit 1601-01-01. Unix-Epoch liegt
+// 11_644_473_600 Sekunden danach.
+fn unix_to_ft_ticks(unix_secs: i64) -> i64 {
+    (unix_secs + 11_644_473_600) * 10_000_000
+}
+
+// ---------------------------------------------------------------------------
+// Sync-Root-Registrierung
+// ---------------------------------------------------------------------------
+
+pub fn register_sync_root(
+    mount_point: &PathBuf,
+    provider_name: &str,
+    account_id: &str,
+) -> Result<(), String> {
+    // COM initialisieren (cfapi benoetigt MTA-Apartment)
+    unsafe {
+        let _ = CoInitializeEx(Some(ptr::null()), COINIT_MULTITHREADED);
+    }
+
+    std::fs::create_dir_all(mount_point).map_err(|e| format!("mkdir: {e}"))?;
+
+    let display = format!("Mini-Cloud - {}", account_id);
+    let path_wide = U16CString::from_str(mount_point.to_string_lossy().as_ref())
+        .map_err(|e| format!("path encode: {e}"))?;
+    let display_wide = U16CString::from_str(&display).map_err(|e| e.to_string())?;
+    let provider_wide = U16CString::from_str(provider_name).map_err(|e| e.to_string())?;
+    let version_wide = U16CString::from_str(PROVIDER_VERSION).map_err(|e| e.to_string())?;
+
+    let mut info = CF::CF_SYNC_REGISTRATION::default();
+    info.StructSize = std::mem::size_of::<CF::CF_SYNC_REGISTRATION>() as u32;
+    info.ProviderName = PCWSTR(provider_wide.as_ptr());
+    info.ProviderVersion = PCWSTR(version_wide.as_ptr());
+    // Stabile GUID fuer "Mini-Cloud" (random einmalig generiert).
+    info.ProviderId = windows::core::GUID::from_u128(0x4D696E69_436C_6F75_6444_7566667944ab);
+
+    let mut policies = CF::CF_SYNC_POLICIES::default();
+    policies.StructSize = std::mem::size_of::<CF::CF_SYNC_POLICIES>() as u32;
+    policies.HardLink = CF::CF_HARDLINK_POLICY::default();
+    policies.Hydration = CF::CF_HYDRATION_POLICY::default();
+    policies.Population = CF::CF_POPULATION_POLICY::default();
+    policies.InSync = CF::CF_INSYNC_POLICY::default();
+
+    // Hydration PARTIAL = Datei-Inhalt kommt bei Zugriff per FETCH_DATA.
+    // Population FULL = Ordnerinhalt ist komplett vorgefuellt durch uns
+    // (populate_placeholders). So muss Windows NICHT FETCH_PLACEHOLDERS
+    // callen, den wir nicht implementieren - sonst timeout beim Oeffnen.
+    policies.Hydration.Primary = CF::CF_HYDRATION_POLICY_PARTIAL;
+    policies.Population.Primary = CF::CF_POPULATION_POLICY_FULL;
+
+    // Holder fuer displayname, damit wir ihn spaeter ggf. in ein eigenes
+    // struct einbauen koennen. windows-rs verlangt hier nichts weiter.
+    let _ = display_wide;
+
+    // Erst eine eventuell vorhandene Registrierung wegraeumen. Sonst
+    // uebernimmt UPDATE nur einen Teil der Policies und alte PARTIAL-
+    // Population-Einstellungen bleiben aktiv -> Explorer-Timeout.
+    unsafe {
+        let _ = CF::CfUnregisterSyncRoot(PCWSTR(path_wide.as_ptr()));
+    }
+
+    log_msg(mount_point, &format!(
+        "register_sync_root path={} provider={} account={}",
+        mount_point.display(), provider_name, account_id
+    ));
+
+    unsafe {
+        if let Err(e) = CF::CfRegisterSyncRoot(
+            PCWSTR(path_wide.as_ptr()),
+            &info,
+            &policies,
+            CF::CF_REGISTER_FLAG_NONE,
+        ) {
+            log_err(mount_point, &format!("CfRegisterSyncRoot FAILED: {e:?}"));
+            // Als Fallback mit UPDATE-Flag
+            CF::CfRegisterSyncRoot(
+                PCWSTR(path_wide.as_ptr()),
+                &info,
+                &policies,
+                CF::CF_REGISTER_FLAG_UPDATE,
+            )
+            .map_err(|e| format!("CfRegisterSyncRoot(UPDATE): {e}"))?;
+        }
+    }
+
+    log_msg(mount_point, "CfRegisterSyncRoot OK");
+    connect_callbacks(mount_point)?;
+    log_msg(mount_point, "callbacks connected");
+
+    // Explorer-Sidebar-Eintrag mit Wolken-Icon
+    let icon = super::shell_integration::default_icon_source();
+    match super::shell_integration::install(provider_name, mount_point, &icon) {
+        Ok(()) => log_msg(mount_point, "shell integration installed"),
+        Err(e) => log_err(mount_point, &format!("shell integration FAILED: {e}")),
+    }
+
+    Ok(())
+}
+
+pub fn unregister_sync_root(mount_point: &PathBuf) -> Result<(), String> {
+    // Shell-Eintrag zuerst entfernen (schlaegt nie fehl).
+    let _ = super::shell_integration::uninstall();
+
+    let _ = disconnect_callbacks();
+    let path_wide = U16CString::from_str(mount_point.to_string_lossy().as_ref())
+        .map_err(|e| e.to_string())?;
+    unsafe {
+        CF::CfUnregisterSyncRoot(PCWSTR(path_wide.as_ptr()))
+            .map_err(|e| format!("CfUnregisterSyncRoot: {e}"))?;
+    }
+    Ok(())
+}
+
+// ---------------------------------------------------------------------------
+// Callback-Tabelle
+// ---------------------------------------------------------------------------
+
+unsafe extern "system" fn on_fetch_data(
+    info: *const CF::CF_CALLBACK_INFO,
+    params: *const CF::CF_CALLBACK_PARAMETERS,
+) {
+    let info = &*info;
+    let params = &*params;
+    let fetch = &params.Anonymous.FetchData;
+
+    // FileIdentity enthaelt unsere Mini-Cloud-File-ID als UTF-8-Bytes.
+    let identity = std::slice::from_raw_parts(
+        info.FileIdentity as *const u8,
+        info.FileIdentityLength as usize,
+    );
+    let file_id: i64 = std::str::from_utf8(identity)
+        .ok()
+        .and_then(|s| s.parse().ok())
+        .unwrap_or(0);
+
+    let offset: i64 = fetch.RequiredFileOffset;
+    let length: u64 = fetch.RequiredLength as u64;
+    let connection_key = info.ConnectionKey;
+    let transfer_key = info.TransferKey;
+
+    // HTTPS-Download im separaten Thread (Callback darf nicht blockieren).
+    let ctx = ctx_snapshot();
+    std::thread::spawn(move || {
+        log_msg(&ctx.mount_point, &format!(
+            "FETCH_DATA file_id={file_id} offset={offset} len={length}"
+        ));
+        match transfer_range(connection_key, transfer_key, file_id, offset, length, &ctx) {
+            Ok(()) => log_msg(&ctx.mount_point, &format!(
+                "fetch file_id={file_id} OK"
+            )),
+            Err(e) => {
+                log_err(&ctx.mount_point, &format!(
+                    "fetch file_id={file_id} offset={offset} len={length} FAILED: {e}"
+                ));
+                // Garantiert Fehler-Completion, damit Windows nicht in Timeout laeuft.
+                let _ = complete_transfer(connection_key, transfer_key, None, offset, length);
+            }
+        }
+    });
+}
+
+pub fn log_msg(mount: &Path, msg: &str) {
+    use std::io::Write;
+    // Log-Datei NEBEN den Mount, damit sie nicht selbst als Platzhalter
+    // behandelt wird.
+    let log = mount
+        .parent()
+        .map(|p| p.join(".minicloud-cloudfiles.log"))
+        .unwrap_or_else(|| PathBuf::from(".minicloud-cloudfiles.log"));
+    if let Ok(mut f) = std::fs::OpenOptions::new().create(true).append(true).open(&log) {
+        let _ = writeln!(f, "[{}] {}", chrono::Utc::now().to_rfc3339(), msg);
+    }
+}
+
+fn log_err(mount: &Path, msg: &str) {
+    log_msg(mount, msg);
+}
+
+/// True wenn die Datei ein cfapi-Platzhalter ist (noch nicht hydriert)
+/// oder gerade vom Cloud-Filter verwaltet wird. Fuer solche Dateien
+/// duerfen wir KEINEN Upload ausloesen, sonst verwandelt der Sync-Loop
+/// jeden Platzhalter sofort in eine vollstaendig lokale Datei.
+pub fn is_cfapi_placeholder(path: &Path) -> bool {
+    use windows::Win32::Storage::FileSystem::GetFileAttributesW;
+    let Ok(w) = U16CString::from_str(path.to_string_lossy().as_ref()) else {
+        return false;
+    };
+    let attrs = unsafe { GetFileAttributesW(PCWSTR(w.as_ptr())) };
+    if attrs == u32::MAX {
+        return false;
+    }
+    // FILE_ATTRIBUTE_OFFLINE (0x1000) oder
+    // FILE_ATTRIBUTE_RECALL_ON_DATA_ACCESS (0x400000) oder
+    // FILE_ATTRIBUTE_RECALL_ON_OPEN (0x40000)
+    (attrs & 0x0040_1000) != 0 || (attrs & 0x0004_0000) != 0
+}
+
+fn transfer_range(
+    connection_key: CF::CF_CONNECTION_KEY,
+    transfer_key: i64,
+    file_id: i64,
+    offset: i64,
+    length: u64,
+    ctx: &CloudContext,
+) -> Result<(), String> {
+    if ctx.server_url.is_empty() || ctx.access_token.is_empty() {
+        return Err("CloudContext nicht gesetzt (Server/Token leer)".into());
+    }
+    let client = reqwest::blocking::Client::builder()
+        .timeout(std::time::Duration::from_secs(60))
+        .build()
+        .map_err(|e| format!("client: {e}"))?;
+    let url = format!(
+        "{}/api/files/{}/download",
+        ctx.server_url.trim_end_matches('/'),
+        file_id
+    );
+    let range = format!("bytes={}-{}", offset, offset as u64 + length - 1);
+    let resp = client
+        .get(&url)
+        .bearer_auth(&ctx.access_token)
+        .header("Range", &range)
+        .send()
+        .map_err(|e| format!("send: {e}"))?;
+    let status = resp.status();
+    if !status.is_success() && status.as_u16() != 206 {
+        return Err(format!("HTTP {}", status));
+    }
+    let bytes = resp.bytes().map_err(|e: reqwest::Error| e.to_string())?;
+    // Wenn Server kein Range unterstuetzt und volle Datei liefert,
+    // aus dem Body den angeforderten Bereich ausschneiden.
+    let slice: &[u8] = if status.as_u16() == 206 {
+        &bytes[..]
+    } else {
+        let start = offset as usize;
+        let end = (start + length as usize).min(bytes.len());
+        if start >= bytes.len() {
+            &[]
+        } else {
+            &bytes[start..end]
+        }
+    };
+    complete_transfer(connection_key, transfer_key, Some(slice), offset, slice.len() as u64)
+}
+
+fn complete_transfer(
+    connection_key: CF::CF_CONNECTION_KEY,
+    transfer_key: i64,
+    data: Option<&[u8]>,
+    offset: i64,
+    length: u64,
+) -> Result<(), String> {
+    let mut op_info = CF::CF_OPERATION_INFO::default();
+    op_info.StructSize = std::mem::size_of::<CF::CF_OPERATION_INFO>() as u32;
+    op_info.Type = CF::CF_OPERATION_TYPE_TRANSFER_DATA;
+    op_info.ConnectionKey = connection_key;
+    op_info.TransferKey = transfer_key;
+
+    let mut params = CF::CF_OPERATION_PARAMETERS::default();
+    params.ParamSize = std::mem::size_of::<CF::CF_OPERATION_PARAMETERS>() as u32;
+
+    unsafe {
+        let transfer = &mut params.Anonymous.TransferData;
+        if let Some(data) = data {
+            transfer.CompletionStatus = windows::Win32::Foundation::NTSTATUS(0); // STATUS_SUCCESS
+            transfer.Buffer = data.as_ptr() as _;
+            transfer.Offset = offset;
+            transfer.Length = length as i64;
+        } else {
+            transfer.CompletionStatus =
+                windows::Win32::Foundation::NTSTATUS(0xC0000001u32 as i32); // STATUS_UNSUCCESSFUL
+        }
+
+        CF::CfExecute(&op_info, &mut params).map_err(|e| format!("CfExecute: {e}"))?;
+    }
+    Ok(())
+}
+
+unsafe extern "system" fn on_fetch_placeholders(
+    info: *const CF::CF_CALLBACK_INFO,
+    _params: *const CF::CF_CALLBACK_PARAMETERS,
+) {
+    // Safety-Net: wir populieren schon ueber populate_placeholders,
+    // aber falls Windows trotzdem ruft, geben wir leere Antwort.
+    let info = &*info;
+    let mut op_info = CF::CF_OPERATION_INFO::default();
+    op_info.StructSize = std::mem::size_of::<CF::CF_OPERATION_INFO>() as u32;
+    op_info.Type = CF::CF_OPERATION_TYPE_TRANSFER_PLACEHOLDERS;
+    op_info.ConnectionKey = info.ConnectionKey;
+    op_info.TransferKey = info.TransferKey;
+    let mut params = CF::CF_OPERATION_PARAMETERS::default();
+    params.ParamSize = std::mem::size_of::<CF::CF_OPERATION_PARAMETERS>() as u32;
+    let transfer = &mut params.Anonymous.TransferPlaceholders;
+    transfer.CompletionStatus = windows::Win32::Foundation::NTSTATUS(0);
+    transfer.PlaceholderTotalCount = 0;
+    transfer.PlaceholderArray = std::ptr::null_mut();
+    transfer.PlaceholderCount = 0;
+    transfer.EntriesProcessed = 0;
+    transfer.Flags = CF::CF_OPERATION_TRANSFER_PLACEHOLDERS_FLAG_DISABLE_ON_DEMAND_POPULATION;
+    let _ = CF::CfExecute(&op_info, &mut params);
+}
+
+fn connect_callbacks(mount_point: &Path) -> Result<(), String> {
+    let callbacks = [
+        CF::CF_CALLBACK_REGISTRATION {
+            Type: CF::CF_CALLBACK_TYPE_FETCH_DATA,
+            Callback: Some(on_fetch_data),
+        },
+        CF::CF_CALLBACK_REGISTRATION {
+            Type: CF::CF_CALLBACK_TYPE_FETCH_PLACEHOLDERS,
+            Callback: Some(on_fetch_placeholders),
+        },
+        // Sentinel: Type = INVALID beendet die Tabelle.
+        CF::CF_CALLBACK_REGISTRATION {
+            Type: CF::CF_CALLBACK_TYPE_NONE,
+            Callback: None,
+        },
+    ];
+
+    let path_wide = U16CString::from_str(mount_point.to_string_lossy().as_ref())
+        .map_err(|e| e.to_string())?;
+
+    let key = unsafe {
+        CF::CfConnectSyncRoot(
+            PCWSTR(path_wide.as_ptr()),
+            callbacks.as_ptr(),
+            None,
+            CF::CF_CONNECT_FLAG_REQUIRE_PROCESS_INFO
+                | CF::CF_CONNECT_FLAG_REQUIRE_FULL_FILE_PATH,
+        )
+        .map_err(|e| format!("CfConnectSyncRoot: {e}"))?
+    };
+    *CONNECTION_KEY.lock().unwrap() = Some(key);
+    Ok(())
+}
+
+fn disconnect_callbacks() -> Result<(), String> {
+    if let Some(key) = CONNECTION_KEY.lock().unwrap().take() {
+        unsafe {
+            CF::CfDisconnectSyncRoot(key)
+                .map_err(|e| format!("CfDisconnectSyncRoot: {e}"))?;
+        }
+    }
+    Ok(())
+}
+
+// ---------------------------------------------------------------------------
+// Placeholder-Erzeugung
+// ---------------------------------------------------------------------------
+
+pub fn populate_placeholders(
+    mount_point: &PathBuf,
+    entries: &[RemoteEntry],
+) -> Result<(), String> {
+    use std::collections::HashMap;
+    log_msg(mount_point, &format!(
+        "populate_placeholders: {} Eintraege", entries.len()
+    ));
+    let by_id: HashMap<i64, &RemoteEntry> = entries.iter().map(|e| (e.id, e)).collect();
+
+    fn rel_path<'a>(
+        entry: &'a RemoteEntry,
+        by_id: &HashMap<i64, &'a RemoteEntry>,
+    ) -> PathBuf {
+        let mut parts = vec![entry.name.as_str()];
+        let mut cur = entry.parent_id;
+        while let Some(id) = cur {
+            if let Some(p) = by_id.get(&id) {
+                parts.push(p.name.as_str());
+                cur = p.parent_id;
+            } else {
+                break;
+            }
+        }
+        parts.reverse();
+        parts.iter().collect()
+    }
+
+    // Erst Ordner anlegen
+    for e in entries.iter().filter(|e| e.is_folder) {
+        let p = mount_point.join(rel_path(e, &by_id));
+        std::fs::create_dir_all(&p).ok();
+    }
+
+    // Dann Dateien als Platzhalter. Existierende "normale" Dateien
+    // (z.B. nach vorherigem CfUnregisterSyncRoot) vorher loeschen,
+    // weil CfCreatePlaceholders sonst mit ERROR_FILE_EXISTS scheitert
+    // und die Datei nie zum Platzhalter wird -> spaeter koennte man
+    // sie nicht mehr dehydrieren (0x80070178 "keine Clouddatei").
+    for e in entries.iter().filter(|e| !e.is_folder) {
+        let rel = rel_path(e, &by_id);
+        let full = mount_point.join(&rel);
+        let parent = rel
+            .parent()
+            .map(|p| mount_point.join(p))
+            .unwrap_or_else(|| mount_point.clone());
+        let identity = e.id.to_string();
+
+        if full.exists() && !is_cfapi_placeholder(&full) {
+            log_msg(mount_point, &format!(
+                "deleting non-placeholder {} to recreate",
+                full.display()
+            ));
+            if let Err(err) = std::fs::remove_file(&full) {
+                log_err(mount_point, &format!(
+                    "remove {} failed: {err}", full.display()
+                ));
+            }
+        }
+
+        match create_placeholder(&parent, &e.name, e.size, &e.modified_at, identity.as_bytes()) {
+            Ok(()) => log_msg(mount_point, &format!("placeholder created: {}", full.display())),
+            Err(err) => log_err(mount_point, &format!(
+                "placeholder {} FAILED: {err}", full.display()
+            )),
+        }
+    }
+    Ok(())
+}
+
+pub fn create_placeholder_at(
+    parent_dir: &Path,
+    name: &str,
+    size: i64,
+    modified_iso: &str,
+    file_identity: &[u8],
+) -> Result<(), String> {
+    create_placeholder(parent_dir, name, size, modified_iso, file_identity)
+}
+
+fn create_placeholder(
+    parent_dir: &Path,
+    name: &str,
+    size: i64,
+    modified_iso: &str,
+    file_identity: &[u8],
+) -> Result<(), String> {
+    let parent_wide = U16CString::from_str(parent_dir.to_string_lossy().as_ref())
+        .map_err(|e| e.to_string())?;
+    let name_wide = U16CString::from_str(name).map_err(|e| e.to_string())?;
+
+    let mtime_unix = chrono::DateTime::parse_from_rfc3339(modified_iso)
+        .map(|dt| dt.timestamp())
+        .unwrap_or(0);
+    let ft_ticks = unix_to_ft_ticks(mtime_unix);
+
+    let mut ph = CF::CF_PLACEHOLDER_CREATE_INFO::default();
+    ph.RelativeFileName = PCWSTR(name_wide.as_ptr());
+    ph.FsMetadata.FileSize = size;
+    ph.FsMetadata.BasicInfo.FileAttributes = FILE_ATTRIBUTE_NORMAL.0;
+    ph.FsMetadata.BasicInfo.LastWriteTime = ft_ticks;
+    ph.FsMetadata.BasicInfo.CreationTime = ft_ticks;
+    ph.FsMetadata.BasicInfo.ChangeTime = ft_ticks;
+    ph.FsMetadata.BasicInfo.LastAccessTime = ft_ticks;
+    ph.Flags = CF::CF_PLACEHOLDER_CREATE_FLAG_MARK_IN_SYNC;
+    ph.FileIdentity = file_identity.as_ptr() as _;
+    ph.FileIdentityLength = file_identity.len() as u32;
+
+    // CfCreatePlaceholders nimmt in windows-rs 0.58 einen Slice und einen
+    // Option<*mut u32> fuer "wie viele wurden angelegt".
+    let mut phs = [ph];
+    let mut count: u32 = 0;
+    unsafe {
+        CF::CfCreatePlaceholders(
+            PCWSTR(parent_wide.as_ptr()),
+            &mut phs,
+            CF::CF_CREATE_FLAG_NONE,
+            Some(&mut count as *mut u32),
+        )
+        .map_err(|e| format!("CfCreatePlaceholders: {e}"))?;
+    }
+    Ok(())
+}
+
+// ---------------------------------------------------------------------------
+// Pin / Unpin (offline halten)
+// ---------------------------------------------------------------------------
+
+pub fn set_pin_state(file: &Path, pinned: bool) -> Result<(), String> {
+    use windows::Win32::Storage::FileSystem::{
+        CreateFileW, FILE_FLAG_BACKUP_SEMANTICS, FILE_FLAG_OPEN_REPARSE_POINT,
+        FILE_WRITE_ATTRIBUTES, FILE_READ_ATTRIBUTES,
+        FILE_SHARE_READ, FILE_SHARE_WRITE, FILE_SHARE_DELETE, OPEN_EXISTING,
+    };
+
+    let path_wide = U16CString::from_str(file.to_string_lossy().as_ref())
+        .map_err(|e| e.to_string())?;
+    // CfSetPinState / CfDehydratePlaceholder brauchen WRITE_ATTRIBUTES.
+    // OPEN_REPARSE_POINT verhindert, dass das Oeffnen selbst eine
+    // Hydration ausloest (sonst waere Unpin bedeutungslos).
+    let handle = unsafe {
+        CreateFileW(
+            PCWSTR(path_wide.as_ptr()),
+            (FILE_READ_ATTRIBUTES | FILE_WRITE_ATTRIBUTES).0,
+            FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE,
+            None,
+            OPEN_EXISTING,
+            FILE_FLAG_BACKUP_SEMANTICS | FILE_FLAG_OPEN_REPARSE_POINT,
+            None,
+        )
+    }
+    .map_err(|e| format!("open: {e}"))?;
+
+    let state = if pinned {
+        CF::CF_PIN_STATE_PINNED
+    } else {
+        CF::CF_PIN_STATE_UNPINNED
+    };
+    let set_res = unsafe {
+        CF::CfSetPinState(handle, state, CF::CF_SET_PIN_FLAG_NONE, None)
+    };
+
+    // Hydrate bei Pin / Dehydrate bei Unpin. CfSetPinState aendert nur
+    // das Flag - ohne explizite Hydrate-/Dehydrate-Calls passiert am
+    // Disk-Inhalt und am Icon nichts Sichtbares.
+    let (hydrate_err, dehydrate_err) = if set_res.is_ok() {
+        if pinned {
+            let r = unsafe {
+                CF::CfHydratePlaceholder(
+                    handle,
+                    0,
+                    -1,
+                    CF::CF_HYDRATE_FLAG_NONE,
+                    None,
+                )
+            };
+            (r.err().map(|e| format!("{:?}", e)), None)
+        } else {
+            let r = unsafe {
+                CF::CfDehydratePlaceholder(
+                    handle,
+                    0,
+                    -1,
+                    CF::CF_DEHYDRATE_FLAG_NONE,
+                    None,
+                )
+            };
+            (None, r.err().map(|e| format!("{:?}", e)))
+        }
+    } else {
+        (None, None)
+    };
+
+    unsafe {
+        let _ = windows::Win32::Foundation::CloseHandle(handle);
+    }
+
+    // Explorer Icon-Overlay aktualisieren
+    notify_file_update(file);
+
+    // Log-Verzeichnis ist der Mount-Ordner oder dessen Parent
+    let log_dir = file
+        .ancestors()
+        .find(|p| p.parent().is_some())
+        .map(|p| p.to_path_buf())
+        .unwrap_or_else(|| file.to_path_buf());
+    log_msg(
+        &log_dir,
+        &format!(
+            "set_pin_state file={} pinned={} result={:?} hydrate_err={:?} dehydrate_err={:?}",
+            file.display(),
+            pinned,
+            set_res,
+            hydrate_err,
+            dehydrate_err
+        ),
+    );
+
+    set_res.map_err(|e| format!("CfSetPinState: {e}"))?;
+    Ok(())
+}
+
+/// Sagt dem Shell "diese Datei hat sich geaendert" damit das Overlay-
+/// Icon (Wolke/Haken) aktualisiert wird, ohne dass der User F5 druecken
+/// muss.
+fn notify_file_update(file: &Path) {
+    use windows::Win32::UI::Shell::{SHChangeNotify, SHCNE_UPDATEITEM, SHCNF_PATHW};
+    let Ok(w) = U16CString::from_str(file.to_string_lossy().as_ref()) else {
+        return;
+    };
+    unsafe {
+        SHChangeNotify(
+            SHCNE_UPDATEITEM,
+            SHCNF_PATHW,
+            Some(w.as_ptr() as _),
+            None,
+        );
+    }
+}

clients/desktop/src-tauri/src/lib.rs

@@ -1,4 +1,5 @@
 mod sync;
+mod cloud_files;
 
 use std::path::PathBuf;
 use std::sync::atomic::{AtomicBool, Ordering};
@@ -26,6 +27,8 @@ struct AppState {
     sync_paths: Mutex<Vec<SyncPath>>,
     journal: Arc<Journal>,
     background_started: AtomicBool,
+    cloud_files_loop: Mutex<Option<cloud_files::sync_loop::SyncLoopHandle>>,
+    cloud_files_watcher: Mutex<Option<cloud_files::watcher::CallbackWatcher>>,
 }
 
 // --- Auth ---
@@ -884,8 +887,272 @@ fn handle_single_instance() {
 
 
 
+// ---------------------------------------------------------------------------
+// Native File-Provider-Integration (OneDrive-artige Platzhalter)
+// ---------------------------------------------------------------------------
+
+#[tauri::command]
+fn cloud_files_supported() -> bool {
+    cloud_files::is_supported()
+}
+
+#[tauri::command]
+async fn cloud_files_enable(
+    state: State<'_, AppState>,
+    mount_point: String,
+) -> Result<(), String> {
+    let mp = PathBuf::from(&mount_point);
+    // MutexGuards nur kurz halten, damit der Future Send bleibt.
+    let (server, token, username) = {
+        let api_guard = state.api.lock().unwrap();
+        let api = api_guard.as_ref().ok_or("Nicht eingeloggt")?;
+        let username = state
+            .username
+            .lock()
+            .unwrap()
+            .clone()
+            .unwrap_or_else(|| "user".into());
+        (api.server_url.clone(), api.access_token.clone(), username)
+    };
+
+    #[cfg(windows)]
+    {
+        cloud_files::windows::set_context(server.clone(), token.clone(), mp.clone());
+    }
+
+    cloud_files::register_sync_root(&mp, "Mini-Cloud", &username)?;
+
+    // Baum vom Server holen und Platzhalter anlegen
+    let entries = fetch_remote_entries(&server, &token).await?;
+    cloud_files::populate_placeholders(&mp, &entries)?;
+
+    // Hintergrund-Loop starten: poll Changes + upload lokaler Aenderungen
+    let cfg = cloud_files::sync_loop::SyncLoopConfig {
+        server_url: server.clone(),
+        access_token: token.clone(),
+        mount_point: mp.clone(),
+        poll_interval_secs: 30,
+    };
+    let handle = cloud_files::sync_loop::start(cfg);
+
+    // Filesystem-Watcher mit Callback; leitet geaenderte Dateien
+    // direkt an den Sync-Loop weiter.
+    let tx = handle.tx.clone();
+    let watcher = cloud_files::watcher::CallbackWatcher::new(&mp, move |path, kind| {
+        use notify::EventKind;
+        let relevant = matches!(kind, EventKind::Create(_) | EventKind::Modify(_));
+        if relevant {
+            let _ = tx.send(cloud_files::sync_loop::LoopMessage::LocalChange(path));
+        }
+    })
+    .map_err(|e| format!("watcher: {e}"))?;
+
+    *state.cloud_files_loop.lock().unwrap() = Some(handle);
+    *state.cloud_files_watcher.lock().unwrap() = Some(watcher);
+
+    // Mount-Pfad persistieren, damit er beim Neustart wiederkommt.
+    let mut cfg = AppConfig::load();
+    cfg.cloud_files_mount = mount_point.clone();
+    let _ = cfg.save();
+
+    Ok(())
+}
+
+#[tauri::command]
+async fn cloud_files_disable(
+    state: State<'_, AppState>,
+    mount_point: String,
+) -> Result<(), String> {
+    // Loop und Watcher stoppen
+    if let Some(handle) = state.cloud_files_loop.lock().unwrap().take() {
+        handle.stop_flag.store(true, std::sync::atomic::Ordering::Relaxed);
+        let _ = handle.tx.send(cloud_files::sync_loop::LoopMessage::Shutdown);
+    }
+    state.cloud_files_watcher.lock().unwrap().take();
+    let result = cloud_files::unregister_sync_root(&PathBuf::from(&mount_point));
+
+    // Auch bei Fehler Mount aus Config loeschen, damit der Client nicht
+    // endlos versucht, einen toten Pfad wiederherzustellen.
+    let mut cfg = AppConfig::load();
+    cfg.cloud_files_mount.clear();
+    let _ = cfg.save();
+
+    result
+}
+
+#[tauri::command]
+fn cloud_files_get_mount() -> String {
+    AppConfig::load().cloud_files_mount
+}
+
+/// Notfall-Aufraeumen: Ordner als Sync-Root deregistrieren, auch wenn
+/// kein Callback-Handle existiert. Nuetzlich wenn der Client hart beendet
+/// wurde und ein "toter" Ordner in Windows haengt.
+#[tauri::command]
+async fn cloud_files_force_cleanup(mount_point: String) -> Result<(), String> {
+    let mp = PathBuf::from(&mount_point);
+    let _ = cloud_files::unregister_sync_root(&mp);
+    let mut cfg = AppConfig::load();
+    cfg.cloud_files_mount.clear();
+    let _ = cfg.save();
+    Ok(())
+}
+
+#[tauri::command]
+async fn cloud_files_pin(path: String) -> Result<(), String> {
+    cloud_files::pin_file(&PathBuf::from(path))
+}
+
+#[tauri::command]
+async fn cloud_files_unpin(path: String) -> Result<(), String> {
+    cloud_files::unpin_file(&PathBuf::from(path))
+}
+
+async fn fetch_remote_entries(
+    server: &str,
+    token: &str,
+) -> Result<Vec<cloud_files::RemoteEntry>, String> {
+    let client = reqwest::Client::new();
+    let url = format!("{}/api/sync/tree", server.trim_end_matches('/'));
+    let resp = client
+        .get(&url)
+        .bearer_auth(token)
+        .send()
+        .await
+        .map_err(|e| format!("tree: {e}"))?;
+    if !resp.status().is_success() {
+        return Err(format!("HTTP {}", resp.status()));
+    }
+    let json: serde_json::Value = resp.json().await.map_err(|e| e.to_string())?;
+    let tree = json
+        .get("tree")
+        .ok_or("Antwort ohne 'tree'")?
+        .as_array()
+        .cloned()
+        .unwrap_or_default();
+    let shared = json
+        .get("shared")
+        .and_then(|v| v.as_array())
+        .cloned()
+        .unwrap_or_default();
+
+    // Rekursiv flach machen (Struktur parent_id beibehalten).
+    // modified_at akzeptiert beides: das neue "modified_at" oder das
+    // alte "updated_at" als Fallback.
+    fn walk(
+        nodes: &[serde_json::Value],
+        parent: Option<i64>,
+        out: &mut Vec<cloud_files::RemoteEntry>,
+    ) {
+        for n in nodes {
+            let id = n.get("id").and_then(|x| x.as_i64()).unwrap_or(0);
+            let name = n
+                .get("name")
+                .and_then(|x| x.as_str())
+                .unwrap_or("")
+                .to_string();
+            let is_folder = n.get("is_folder").and_then(|x| x.as_bool()).unwrap_or(false);
+            let size = n.get("size").and_then(|x| x.as_i64()).unwrap_or(0);
+            let modified_at = n
+                .get("modified_at")
+                .and_then(|x| x.as_str())
+                .or_else(|| n.get("updated_at").and_then(|x| x.as_str()))
+                .unwrap_or("")
+                .to_string();
+            let checksum = n
+                .get("checksum")
+                .and_then(|x| x.as_str())
+                .map(|s| s.to_string());
+            out.push(cloud_files::RemoteEntry {
+                id,
+                name,
+                parent_id: parent,
+                is_folder,
+                size,
+                modified_at,
+                checksum,
+            });
+            if let Some(children) = n.get("children").and_then(|x| x.as_array()) {
+                walk(children, Some(id), out);
+            }
+        }
+    }
+    let mut flat = Vec::new();
+    walk(&tree, None, &mut flat);
+
+    // Virtueller Ordner "Geteilt mit mir" nur dann, wenn es geteilte
+    // Dateien gibt. ID -1 ist reserviert dafuer (keine Kollision
+    // mit echten DB-IDs).
+    if !shared.is_empty() {
+        flat.push(cloud_files::RemoteEntry {
+            id: -1,
+            name: "Geteilt mit mir".to_string(),
+            parent_id: None,
+            is_folder: true,
+            size: 0,
+            modified_at: String::new(),
+            checksum: None,
+        });
+        walk(&shared, Some(-1), &mut flat);
+    }
+
+    Ok(flat)
+}
+
+/// Short-circuit fuer Shell-Kontextmenue-Aufrufe:
+/// `minicloud-sync --pin <file>` oder `--unpin <file>` fuehrt die
+/// Aktion direkt aus und beendet. Kein UI, kein Tray.
+/// Logs landen in %LOCALAPPDATA%\MiniCloud Sync\cli.log - sonst
+/// wuerden wir vom Explorer gestartete Prozesse nie debuggen koennen.
+#[cfg(windows)]
+fn handle_cli_shortcuts() {
+    use std::io::Write;
+    let args: Vec<String> = std::env::args().collect();
+    if args.len() < 3 {
+        return;
+    }
+    let cmd = args[1].as_str();
+    if cmd != "--pin" && cmd != "--unpin" {
+        return;
+    }
+    let path = std::path::PathBuf::from(&args[2]);
+
+    let log_path = dirs::data_local_dir()
+        .unwrap_or_else(|| std::path::PathBuf::from("."))
+        .join("MiniCloud Sync")
+        .join("cli.log");
+    if let Some(p) = log_path.parent() {
+        let _ = std::fs::create_dir_all(p);
+    }
+    let log = |msg: &str| {
+        if let Ok(mut f) = std::fs::OpenOptions::new()
+            .create(true)
+            .append(true)
+            .open(&log_path)
+        {
+            let _ = writeln!(f, "[{}] {}", chrono::Utc::now().to_rfc3339(), msg);
+        }
+    };
+
+    log(&format!("CLI invoked: {} {}", cmd, path.display()));
+    let result = match cmd {
+        "--pin" => cloud_files::pin_file(&path),
+        "--unpin" => cloud_files::unpin_file(&path),
+        _ => unreachable!(),
+    };
+    match &result {
+        Ok(()) => log(&format!("{cmd} OK: {}", path.display())),
+        Err(e) => log(&format!("{cmd} FAILED: {e}")),
+    }
+    std::process::exit(if result.is_ok() { 0 } else { 1 });
+}
+
+#[cfg(not(windows))]
+fn handle_cli_shortcuts() {}
+
 #[cfg_attr(mobile, tauri::mobile_entry_point)]
 pub fn run() {
+    handle_cli_shortcuts();
     handle_single_instance();
 
     tauri::Builder::default()
@@ -902,6 +1169,8 @@ pub fn run() {
             sync_paths: Mutex::new(Vec::new()),
             journal: Arc::new(Journal::open().expect("Journal konnte nicht geoeffnet werden")),
             background_started: AtomicBool::new(false),
+            cloud_files_loop: Mutex::new(None),
+            cloud_files_watcher: Mutex::new(None),
         })
         .on_window_event(|window, event| {
             // Close button = minimize to tray instead of quit
@@ -1016,6 +1285,13 @@ pub fn run() {
             browse_sync_folder,
             mark_offline,
             unmark_offline,
+            cloud_files_supported,
+            cloud_files_enable,
+            cloud_files_disable,
+            cloud_files_get_mount,
+            cloud_files_force_cleanup,
+            cloud_files_pin,
+            cloud_files_unpin,
         ])
         .run(tauri::generate_context!())
         .expect("error while running tauri application");

clients/desktop/src-tauri/src/sync/config.rs

@@ -13,6 +13,10 @@ pub struct AppConfig {
     pub auto_start: bool,
     #[serde(default)]
     pub start_minimized: bool,
+    /// Persistierter Mount-Punkt der Cloud-Files-Integration.
+    /// Leer = nicht aktiv. Wird beim App-Start wieder aktiviert.
+    #[serde(default)]
+    pub cloud_files_mount: String,
 }
 
 impl AppConfig {

clients/desktop/src/App.vue

@@ -31,6 +31,75 @@ const newPathLocal = ref("");
 const newPathServerFolder = ref("");
 const newPathServerId = ref(null);
 const newPathMode = ref("virtual");
+
+// Cloud-Files (Windows cfapi / Linux FUSE)
+const cloudFilesSupported = ref(false);
+const cloudFilesActive = ref(false);
+const cloudFilesBusy = ref(false);
+const cloudFilesMountPoint = ref("");
+const cloudFilesError = ref("");
+
+async function checkCloudFilesSupport() {
+  try { cloudFilesSupported.value = await invoke("cloud_files_supported"); }
+  catch { cloudFilesSupported.value = false; }
+  try {
+    const saved = await invoke("cloud_files_get_mount");
+    if (saved) cloudFilesMountPoint.value = saved;
+  } catch { /* no saved mount */ }
+}
+
+async function forceCleanupCloudFiles() {
+  if (!cloudFilesMountPoint.value) return;
+  if (!confirm(`Sync-Root unter ${cloudFilesMountPoint.value} zwangsweise aufraeumen?\n\nDanach kann der Ordner ggf. geloescht werden.`)) return;
+  cloudFilesError.value = "";
+  cloudFilesBusy.value = true;
+  try {
+    await invoke("cloud_files_force_cleanup", { mountPoint: cloudFilesMountPoint.value });
+    cloudFilesActive.value = false;
+    cloudFilesMountPoint.value = "";
+    syncLog.value = [`[${ts()}] Cloud-Files Zwangsbereinigung durchgefuehrt`, ...syncLog.value].slice(0, 200);
+  } catch (err) {
+    cloudFilesError.value = String(err);
+  } finally {
+    cloudFilesBusy.value = false;
+  }
+}
+
+async function browseCfMount() {
+  try {
+    const selected = await dialogOpen({ directory: true, multiple: false,
+                                        title: "Cloud-Files-Ordner waehlen" });
+    if (selected) cloudFilesMountPoint.value = selected;
+  } catch { /* cancelled */ }
+}
+
+async function enableCloudFiles() {
+  cloudFilesError.value = "";
+  cloudFilesBusy.value = true;
+  try {
+    await invoke("cloud_files_enable", { mountPoint: cloudFilesMountPoint.value });
+    cloudFilesActive.value = true;
+    syncLog.value = [`[${ts()}] Cloud-Files aktiviert: ${cloudFilesMountPoint.value}`, ...syncLog.value].slice(0, 200);
+  } catch (err) {
+    cloudFilesError.value = String(err);
+  } finally {
+    cloudFilesBusy.value = false;
+  }
+}
+
+async function disableCloudFiles() {
+  cloudFilesError.value = "";
+  cloudFilesBusy.value = true;
+  try {
+    await invoke("cloud_files_disable", { mountPoint: cloudFilesMountPoint.value });
+    cloudFilesActive.value = false;
+    syncLog.value = [`[${ts()}] Cloud-Files deaktiviert`, ...syncLog.value].slice(0, 200);
+  } catch (err) {
+    cloudFilesError.value = String(err);
+  } finally {
+    cloudFilesBusy.value = false;
+  }
+}
 const serverFolders = ref([]);
 
 // Local file browser
@@ -289,6 +358,7 @@ function formatSize(b) {
 }
 
 onMounted(async () => {
+  await checkCloudFilesSupport();
   // Try auto-login with saved credentials
   try {
     const saved = await invoke("load_saved_config");
@@ -308,6 +378,15 @@ onMounted(async () => {
         if (syncPaths.value.length > 0) {
           await startSync();
         }
+        // Cloud-Files automatisch reaktivieren, wenn Mount gespeichert.
+        if (cloudFilesSupported.value && cloudFilesMountPoint.value) {
+          try {
+            await invoke("cloud_files_enable", { mountPoint: cloudFilesMountPoint.value });
+            cloudFilesActive.value = true;
+          } catch (e) {
+            cloudFilesError.value = `Auto-Reaktivierung fehlgeschlagen: ${e}`;
+          }
+        }
       } catch (err) {
         syncStatus.value = "Auto-Login fehlgeschlagen";
         // Show login screen with pre-filled fields
@@ -387,8 +466,47 @@ onUnmounted(() => { unlistenStatus?.(); unlistenLog?.(); unlistenError?.(); unli
     </div>
 
     <div class="content">
-      <!-- Sync Paths -->
+      <!-- Cloud-Files (Windows Cloud Files API, OneDrive-artig) -->
       <div class="section">
+        <div class="section-header">
+          <h3>Cloud-Files (OneDrive-Style)</h3>
+          <span v-if="cloudFilesActive" class="status-badge syncing">☁ aktiv</span>
+          <span v-else-if="!cloudFilesSupported" class="status-badge error">nicht verfuegbar</span>
+        </div>
+        <p class="hint">
+          Dateien erscheinen als Platzhalter im Explorer mit Wolken-Icon und
+          werden erst bei Zugriff geladen. Rechtsklick im Explorer &rarr;
+          "Immer offline halten" oder "Speicher freigeben".
+        </p>
+        <p v-if="!cloudFilesSupported" class="hint" style="color:#c62828">
+          Auf dieser Plattform noch nicht verfuegbar. Aktuell: Windows 10/11.
+          Linux-FUSE ist in Vorbereitung, macOS folgt mit Apple-Signatur.
+        </p>
+        <template v-else>
+          <div class="cf-row">
+            <input v-model="cloudFilesMountPoint" placeholder="Ordner waehlen..." />
+            <button class="btn-secondary" @click="browseCfMount">Durchsuchen</button>
+            <button v-if="!cloudFilesActive" class="btn-primary"
+                    :disabled="!cloudFilesMountPoint || cloudFilesBusy"
+                    @click="enableCloudFiles">
+              {{ cloudFilesBusy ? "Aktiviere..." : "Aktivieren" }}
+            </button>
+            <button v-else class="btn-secondary" :disabled="cloudFilesBusy"
+                    @click="disableCloudFiles">Deaktivieren</button>
+            <button v-if="cloudFilesMountPoint && !cloudFilesActive"
+                    class="btn-secondary" :disabled="cloudFilesBusy"
+                    @click="forceCleanupCloudFiles"
+                    title="Toten Sync-Root nach hartem Beenden des Clients aufraeumen">
+              Aufraeumen
+            </button>
+          </div>
+          <div v-if="cloudFilesError" class="error" style="margin-top:0.5rem">{{ cloudFilesError }}</div>
+        </template>
+      </div>
+
+      <!-- Sync Paths (Legacy) - auf Windows ausgeblendet sobald Cloud-Files
+           aktiv ist; Cloud-Files ersetzt diese Ansicht vollstaendig. -->
+      <div v-if="!cloudFilesActive" class="section">
         <div class="section-header">
           <h3>Sync-Pfade</h3>
           <div class="header-btns">
@@ -454,8 +572,8 @@ onUnmounted(() => { unlistenStatus?.(); unlistenLog?.(); unlistenError?.(); unli
         </div>
       </div>
 
-      <!-- Local File Browser -->
-      <div v-if="autoSyncActive" class="section" @click="hideContextMenu">
+      <!-- Local File Browser (Legacy, nur fuer Full-Sync-Modus) -->
+      <div v-if="autoSyncActive && !cloudFilesActive" class="section" @click="hideContextMenu">
         <div class="section-header">
           <h3>Lokale Dateien</h3>
           <button @click="loadLocalFiles(null)" class="btn-small">↻</button>
@@ -604,6 +722,8 @@ body{font-family:-apple-system,BlinkMacSystemFont,'Segoe UI',Roboto,sans-serif;f
 .sp-actions{display:flex;align-items:center;gap:.375rem;flex-shrink:0}
 .sp-mode{font-size:.75rem;padding:.2rem .4rem;border-radius:4px;cursor:pointer;background:#f0f0f0}
 .sp-mode.Full{background:#e3f2fd;color:#1565c0}.sp-mode.Virtual{background:#f3e5f5;color:#7b1fa2}
+.cf-row{display:flex;gap:.5rem;align-items:center;flex-wrap:wrap}
+.cf-row input{flex:1;min-width:300px}
 .file-tree{max-height:250px;overflow-y:auto}
 .tree-item{display:flex;align-items:center;gap:.5rem;padding:.3rem 0;border-bottom:1px solid #f5f5f5;font-size:.85rem}
 .tree-item.indent{padding-left:1.5rem}.tree-icon{flex-shrink:0}.tree-name{flex:1;overflow:hidden;text-overflow:ellipsis;white-space:nowrap}