perf: PERF-1/2/3 scrollback bulk write, RDP binary IPC, settings dedup

- Scrollback: bulk copy_from_slice replaces byte-by-byte loop
- RDP frames: tauri::ipc::Response for zero-overhead binary transfer
- SettingsService: derive Clone, eliminate duplicate instance

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

src-tauri/src/commands/rdp_commands.rs

@@ -4,6 +4,7 @@
 //! delegate to the `RdpService` via `State<AppState>`.
 
 use tauri::{AppHandle, State};
+use tauri::ipc::Response;
 
 use crate::rdp::{RdpConfig, RdpSessionInfo};
 use crate::AppState;
@@ -18,16 +19,18 @@ pub fn connect_rdp(
     state.rdp.connect(config, app_handle)
 }
 
-/// Get the current frame buffer as raw RGBA bytes (binary IPC — no base64).
+/// Get the current frame buffer as raw RGBA bytes via binary IPC.
 ///
+/// Uses `tauri::ipc::Response` to return raw bytes without JSON serialization.
 /// Pixel format: RGBA, 4 bytes per pixel, row-major, top-left origin.
-/// Returns empty Vec if frame hasn't changed since last call.
+/// Returns empty payload if frame hasn't changed since last call.
 #[tauri::command]
 pub async fn rdp_get_frame(
     session_id: String,
     state: State<'_, AppState>,
-) -> Result<Vec<u8>, String> {
+) -> Result<Response, String> {
-    state.rdp.get_frame(&session_id).await
+    let frame = state.rdp.get_frame(&session_id).await?;
+    Ok(Response::new(frame))
 }
 
 /// Send a mouse event to an RDP session.

src-tauri/src/lib.rs

@@ -60,17 +60,18 @@ impl AppState {
         std::fs::create_dir_all(&data_dir)?;
         let database = Database::open(&data_dir.join("wraith.db"))?;
         database.migrate()?;
+        let settings = SettingsService::new(database.clone());
         Ok(Self {
             db: database.clone(),
             vault: Mutex::new(None),
-            settings: SettingsService::new(database.clone()),
             connections: ConnectionService::new(database.clone()),
             credentials: Mutex::new(None),
             ssh: SshService::new(database.clone()),
             sftp: SftpService::new(),
             rdp: RdpService::new(),
-            theme: ThemeService::new(database.clone()),
+            theme: ThemeService::new(database),
-            workspace: WorkspaceService::new(SettingsService::new(database.clone())),
+            workspace: WorkspaceService::new(settings.clone()),
+            settings,
             pty: PtyService::new(),
             scrollback: ScrollbackRegistry::new(),
             error_watcher: std::sync::Arc::new(ErrorWatcher::new()),

src-tauri/src/mcp/scrollback.rs

@@ -40,13 +40,25 @@ impl ScrollbackBuffer {
 
     /// Append bytes to the buffer. Old data is overwritten when full.
     pub fn push(&self, bytes: &[u8]) {
-        let mut buf = self.inner.lock().unwrap();
+        if bytes.is_empty() {
-        for &b in bytes {
+            return;
-            let pos = buf.write_pos;
-            buf.data[pos] = b;
-            buf.write_pos = (pos + 1) % buf.capacity;
-            buf.total_written += 1;
         }
+        let mut buf = self.inner.lock().unwrap();
+        let cap = buf.capacity;
+        // If input exceeds capacity, only keep the last `cap` bytes
+        let data = if bytes.len() > cap {
+            &bytes[bytes.len() - cap..]
+        } else {
+            bytes
+        };
+        let write_pos = buf.write_pos;
+        let first_len = (cap - write_pos).min(data.len());
+        buf.data[write_pos..write_pos + first_len].copy_from_slice(&data[..first_len]);
+        if first_len < data.len() {
+            buf.data[..data.len() - first_len].copy_from_slice(&data[first_len..]);
+        }
+        buf.write_pos = (write_pos + data.len()) % cap;
+        buf.total_written += bytes.len();
     }
 
     /// Read the last `n` lines from the buffer, with ANSI escape codes stripped.
@@ -192,4 +204,42 @@ mod tests {
         buf.push(b"ABCD"); // 4 more, wraps
         assert_eq!(buf.total_written(), 12);
     }
+
+    #[test]
+    fn push_empty_is_noop() {
+        let buf = ScrollbackBuffer::with_capacity(8);
+        buf.push(b"hello");
+        buf.push(b"");
+        assert_eq!(buf.total_written(), 5);
+        assert!(buf.read_raw().contains("hello"));
+    }
+
+    #[test]
+    fn push_larger_than_capacity() {
+        let buf = ScrollbackBuffer::with_capacity(4);
+        buf.push(b"ABCDEFGH"); // 8 bytes into 4-byte buffer
+        let raw = buf.read_raw();
+        assert_eq!(raw, "EFGH"); // only last 4 bytes kept
+        assert_eq!(buf.total_written(), 8);
+    }
+
+    #[test]
+    fn push_exact_capacity() {
+        let buf = ScrollbackBuffer::with_capacity(8);
+        buf.push(b"12345678");
+        let raw = buf.read_raw();
+        assert_eq!(raw, "12345678");
+        assert_eq!(buf.total_written(), 8);
+    }
+
+    #[test]
+    fn push_wrap_around_boundary() {
+        let buf = ScrollbackBuffer::with_capacity(8);
+        buf.push(b"123456"); // write_pos = 6
+        buf.push(b"ABCD");  // wraps: 2 at end, 2 at start
+        let raw = buf.read_raw();
+        // Buffer: [C, D, 3, 4, 5, 6, A, B], write_pos=2
+        // Read from pos 2: "3456AB" + wrap: no, read from write_pos to end then start
+        assert_eq!(raw, "3456ABCD");
+    }
 }

src-tauri/src/settings/mod.rs

@@ -8,6 +8,7 @@ use crate::db::Database;
 ///
 /// All operations acquire the shared DB mutex for their duration and
 /// return immediately — no async needed for a local SQLite store.
+#[derive(Clone)]
 pub struct SettingsService {
     db: Database,
 }

src/composables/useRdp.ts

@@ -184,7 +184,7 @@ export interface UseRdpReturn {
  * Composable that manages an RDP session's rendering and input.
  *
  * Uses Tauri's invoke() to call Rust commands:
- *   rdp_get_frame   → base64 RGBA string
+ *   rdp_get_frame   → raw RGBA ArrayBuffer (binary IPC)
  *   rdp_send_mouse  → fire-and-forget
  *   rdp_send_key    → fire-and-forget
  *   rdp_send_clipboard → fire-and-forget
@@ -208,16 +208,16 @@ export function useRdp(): UseRdpReturn {
     width: number,
     height: number,
   ): Promise<ImageData | null> {
-    let raw: number[];
+    let raw: ArrayBuffer;
     try {
-      raw = await invoke<number[]>("rdp_get_frame", { sessionId });
+      raw = await invoke<ArrayBuffer>("rdp_get_frame", { sessionId });
     } catch {
       return null;
     }
 
-    if (!raw || raw.length === 0) return null;
+    if (!raw || raw.byteLength === 0) return null;
 
-    // Binary IPC — Tauri returns Vec<u8> as number array
+    // Binary IPC — tauri::ipc::Response delivers raw bytes as ArrayBuffer
     const bytes = new Uint8ClampedArray(raw);
 
     const expected = width * height * 4;