diff --git a/Client/tauri-client/src-tauri/Cargo.toml b/Client/tauri-client/src-tauri/Cargo.toml
index 69a06d1b..bda73835 100644
--- a/Client/tauri-client/src-tauri/Cargo.toml
+++ b/Client/tauri-client/src-tauri/Cargo.toml
@@ -11,8 +11,12 @@ crate-type = ["lib", "cdylib", "staticlib"]
 [build-dependencies]
 tauri-build = { version = "2", features = [] }
 
+[features]
+default = ["devtools"]
+devtools = ["tauri/devtools"]
+
 [dependencies]
-tauri = { version = "2", features = ["tray-icon", "devtools"] }
+tauri = { version = "2", features = ["tray-icon"] }
 tauri-plugin-store = "2"
 tauri-plugin-global-shortcut = "2"
 tauri-plugin-notification = "2"
diff --git a/Client/tauri-client/src-tauri/src/commands.rs b/Client/tauri-client/src-tauri/src/commands.rs
index 52394ade..67634e51 100644
--- a/Client/tauri-client/src-tauri/src/commands.rs
+++ b/Client/tauri-client/src-tauri/src/commands.rs
@@ -1,10 +1,33 @@
 use serde_json::Value;
-use tauri::Manager;
 use tauri_plugin_store::StoreExt;
 
 const SETTINGS_STORE: &str = "settings.json";
 const CERTS_STORE: &str = "certs.json";
 
+/// Maximum length for a settings key to prevent denial-of-service.
+const MAX_SETTINGS_KEY_LEN: usize = 128;
+
+/// Allowed key prefixes and exact keys for the settings store.
+/// Keys must either match an exact entry or start with an allowed prefix.
+const ALLOWED_SETTINGS_PREFIXES: &[&str] = &[
+    "owncord:",      // owncord:profiles, owncord:settings:*, owncord:recent-emoji
+    "userVolume_",   // per-user volume: userVolume_{userId}
+];
+
+const ALLOWED_SETTINGS_EXACT: &[&str] = &[
+    "windowState",
+];
+
+fn is_settings_key_allowed(key: &str) -> bool {
+    if key.len() > MAX_SETTINGS_KEY_LEN || key.is_empty() {
+        return false;
+    }
+    if ALLOWED_SETTINGS_EXACT.contains(&key) {
+        return true;
+    }
+    ALLOWED_SETTINGS_PREFIXES.iter().any(|prefix| key.starts_with(prefix))
+}
+
 // ---------------------------------------------------------------------------
 // Settings commands
 // ---------------------------------------------------------------------------
@@ -27,6 +50,10 @@ pub fn get_settings(app: tauri::AppHandle) -> Result<Value, String> {
 
 #[tauri::command]
 pub fn save_settings(app: tauri::AppHandle, key: String, value: Value) -> Result<(), String> {
+    if !is_settings_key_allowed(&key) {
+        return Err(format!("unknown settings key: {key}"));
+    }
+
     let store = app
         .store(SETTINGS_STORE)
         .map_err(|e| format!("failed to open settings store: {e}"))?;
@@ -55,6 +82,20 @@ pub fn store_cert_fingerprint(
         return Err("fingerprint must not be empty".into());
     }
 
+    // Validate SHA-256 colon-hex format: "AA:BB:CC:..." (95 chars, 32 hex pairs)
+    if fingerprint.len() != 95 {
+        return Err("fingerprint must be a SHA-256 colon-hex string (95 chars)".into());
+    }
+    for (i, ch) in fingerprint.chars().enumerate() {
+        if i % 3 == 2 {
+            if ch != ':' {
+                return Err("fingerprint must use colon-separated hex pairs".into());
+            }
+        } else if !ch.is_ascii_hexdigit() {
+            return Err("fingerprint contains invalid hex character".into());
+        }
+    }
+
     let store = app
         .store(CERTS_STORE)
         .map_err(|e| format!("failed to open certs store: {e}"))?;
@@ -95,7 +136,10 @@ pub fn get_cert_fingerprint(
 // ---------------------------------------------------------------------------
 
 #[tauri::command]
-pub fn open_devtools(window: tauri::WebviewWindow) {
+pub fn open_devtools(_window: tauri::WebviewWindow) {
     #[cfg(feature = "devtools")]
-    window.open_devtools();
+    {
+        use tauri::Manager;
+        _window.open_devtools();
+    }
 }
diff --git a/Client/tauri-client/src-tauri/src/credentials.rs b/Client/tauri-client/src-tauri/src/credentials.rs
index 26e0ef31..1a78fe21 100644
--- a/Client/tauri-client/src-tauri/src/credentials.rs
+++ b/Client/tauri-client/src-tauri/src/credentials.rs
@@ -8,7 +8,7 @@ use windows::Win32::Security::Credentials::{
 };
 
 /// Data returned from `load_credential`.
-#[derive(Serialize, Clone, Debug)]
+#[derive(Serialize, Clone)]
 pub struct CredentialData {
     pub username: String,
     pub token: String,
@@ -16,6 +16,16 @@ pub struct CredentialData {
     pub password: Option<String>,
 }
 
+impl std::fmt::Debug for CredentialData {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("CredentialData")
+            .field("username", &self.username)
+            .field("token", &"[REDACTED]")
+            .field("password", &self.password.as_ref().map(|_| "[REDACTED]"))
+            .finish()
+    }
+}
+
 /// Build the target name used in Windows Credential Manager.
 fn target_name(host: &str) -> Vec<u16> {
     let name = format!("OwnCord/{host}");
@@ -129,12 +139,12 @@ pub fn load_credential(host: String) -> Result<Option<CredentialData>, String> {
         let username = parsed
             .get("username")
             .and_then(|v| v.as_str())
-            .unwrap_or_default()
+            .ok_or("credential blob missing 'username' field")?
             .to_string();
         let token = parsed
             .get("token")
             .and_then(|v| v.as_str())
-            .unwrap_or_default()
+            .ok_or("credential blob missing 'token' field")?
             .to_string();
         let password = parsed
             .get("password")
diff --git a/Client/tauri-client/src-tauri/src/update_commands.rs b/Client/tauri-client/src-tauri/src/update_commands.rs
index e404ab6d..6e9057ab 100644
--- a/Client/tauri-client/src-tauri/src/update_commands.rs
+++ b/Client/tauri-client/src-tauri/src/update_commands.rs
@@ -33,10 +33,14 @@ pub async fn check_client_update(
         .parse()
         .map_err(|e: url::ParseError| format!("bad endpoint URL: {e}"))?;
 
+    // OwnCord is self-hosted and commonly uses self-signed TLS certs.
+    // The updater connects to the user's own server, so accept invalid certs
+    // (the update artifact itself is verified via Ed25519 signature).
     let updater = app
         .updater_builder()
         .endpoints(vec![url])
         .map_err(|e| format!("failed to set endpoints: {e}"))?
+        .configure_client(|client| client.danger_accept_invalid_certs(true))
         .build()
         .map_err(|e| format!("failed to build updater: {e}"))?;
 
@@ -87,6 +91,7 @@ pub async fn download_and_install_update(
         .updater_builder()
         .endpoints(vec![url])
         .map_err(|e| format!("failed to set endpoints: {e}"))?
+        .configure_client(|client| client.danger_accept_invalid_certs(true))
         .build()
         .map_err(|e| format!("failed to build updater: {e}"))?;
 
diff --git a/Client/tauri-client/src-tauri/tauri.conf.json b/Client/tauri-client/src-tauri/tauri.conf.json
index 23d127d1..410031ec 100644
--- a/Client/tauri-client/src-tauri/tauri.conf.json
+++ b/Client/tauri-client/src-tauri/tauri.conf.json
@@ -48,8 +48,6 @@
     "updater": {
       "pubkey": "dW50cnVzdGVkIGNvbW1lbnQ6IG1pbmlzaWduIHB1YmxpYyBrZXk6IEJCQkQ0NzM1MjkxRTlGQTIKUldTaW54NHBOVWU5dTRqYW0yalI5VTJBd0NXOUZwM2UrcDM4YkhCSmlMZWJKWWVXaGJWdHBaSHgK",
       "endpoints": [],
-      "dangerousAcceptInvalidCerts": true,
-      "dangerousAcceptInvalidHostnames": true,
       "windows": {
         "installMode": "passive"
       }
diff --git a/Client/tauri-client/src/components/ChannelSidebar.ts b/Client/tauri-client/src/components/ChannelSidebar.ts
index c8a5fefc..88abbae3 100644
--- a/Client/tauri-client/src/components/ChannelSidebar.ts
+++ b/Client/tauri-client/src/components/ChannelSidebar.ts
@@ -101,7 +101,6 @@ function showUserVolumeMenu(
 
   // Close on click outside
   const dismissAc = new AbortController();
-  const combinedSignal = signal;
   setTimeout(() => {
     document.addEventListener("mousedown", (e: MouseEvent) => {
       if (!menu.contains(e.target as Node)) {
@@ -112,7 +111,7 @@ function showUserVolumeMenu(
   }, 0);
 
   // Also clean up if the parent component is destroyed
-  combinedSignal.addEventListener("abort", () => {
+  signal.addEventListener("abort", () => {
     menu.remove();
     dismissAc.abort();
   });
diff --git a/Client/tauri-client/src/components/VideoGrid.ts b/Client/tauri-client/src/components/VideoGrid.ts
index 7b575e35..2cbee92e 100644
--- a/Client/tauri-client/src/components/VideoGrid.ts
+++ b/Client/tauri-client/src/components/VideoGrid.ts
@@ -31,9 +31,22 @@ export function createVideoGrid(): VideoGridComponent {
   function addStream(userId: number, username: string, stream: MediaStream): void {
     if (root === null) return;
 
-    // Remove existing cell for this user first
-    if (cells.has(userId)) {
-      removeStream(userId);
+    // If a cell already exists for this user, update it in place
+    const existing = cells.get(userId);
+    if (existing) {
+      const video = existing.querySelector("video");
+      if (video !== null) {
+        // Only replace srcObject if the underlying tracks changed
+        const oldTracks = (video.srcObject as MediaStream | null)?.getTracks() ?? [];
+        const newTracks = stream.getTracks();
+        const tracksMatch =
+          oldTracks.length === newTracks.length &&
+          oldTracks.every((t, i) => t.id === newTracks[i]?.id);
+        if (!tracksMatch) {
+          video.srcObject = stream;
+        }
+      }
+      return;
     }
 
     const video = createElement("video", {
diff --git a/Client/tauri-client/src/components/settings/VoiceAudioTab.ts b/Client/tauri-client/src/components/settings/VoiceAudioTab.ts
index b6c68eec..88b6e72b 100644
--- a/Client/tauri-client/src/components/settings/VoiceAudioTab.ts
+++ b/Client/tauri-client/src/components/settings/VoiceAudioTab.ts
@@ -269,6 +269,7 @@ function buildVoiceAudioTabInner(signal: AbortSignal, registerMic: MicRegistrar,
 
       const dataArray = new Uint8Array(analyser.frequencyBinCount);
 
+      let latestFrame = 0;
       function updateMeter(): void {
         if (signal.aborted) return;
         analyser.getByteFrequencyData(dataArray);
@@ -291,11 +292,11 @@ function buildVoiceAudioTabInner(signal: AbortSignal, registerMic: MicRegistrar,
           meterLevel.style.background = "#faa61a"; // yellow — below threshold
         }
 
-        const frame = requestAnimationFrame(updateMeter);
-        registerMic(stream, audioCtx, frame);
+        latestFrame = requestAnimationFrame(updateMeter);
+        registerMic(stream, audioCtx, latestFrame);
       }
-      const firstFrame = requestAnimationFrame(updateMeter);
-      registerMic(stream, audioCtx, firstFrame);
+      latestFrame = requestAnimationFrame(updateMeter);
+      registerMic(stream, audioCtx, latestFrame);
     } catch {
       // Mic access denied or unavailable — meter stays empty
     }
diff --git a/Client/tauri-client/src/lib/livekitSession.ts b/Client/tauri-client/src/lib/livekitSession.ts
index bec77ede..12723369 100644
--- a/Client/tauri-client/src/lib/livekitSession.ts
+++ b/Client/tauri-client/src/lib/livekitSession.ts
@@ -625,6 +625,9 @@ export async function enableCamera(): Promise<void> {
     return;
   }
 
+  // Optimistic UI update — highlight button immediately
+  setLocalCamera(true);
+
   try {
     await room.localParticipant.setCameraEnabled(true);
 
@@ -634,10 +637,11 @@ export async function enableCamera(): Promise<void> {
       await room.switchActiveDevice("videoinput", savedVideoDevice);
     }
 
-    setLocalCamera(true);
     ws.send({ type: "voice_camera", payload: { enabled: true } });
     log.info("Camera enabled");
   } catch (err) {
+    // Revert optimistic update on failure
+    setLocalCamera(false);
     log.error("Failed to enable camera", err);
     if (err instanceof DOMException && err.name === "NotAllowedError") {
       onErrorCallback?.("Camera permission denied");
@@ -759,7 +763,8 @@ export function getUserVolume(userId: number): number {
  *  High sensitivity (100) = low threshold (picks up quiet sounds).
  *  Low sensitivity (0) = high threshold (only loud sounds). */
 export function setVoiceSensitivity(sensitivity: number): void {
-  speakingThreshold = ((100 - sensitivity) / 100) * 0.15;
+  const clamped = Math.max(0, Math.min(100, sensitivity));
+  speakingThreshold = ((100 - clamped) / 100) * 0.15;
 }
 
 /** Get the local camera stream for self-view display. */
diff --git a/Client/tauri-client/src/main.ts b/Client/tauri-client/src/main.ts
index 64724202..af6cca6c 100644
--- a/Client/tauri-client/src/main.ts
+++ b/Client/tauri-client/src/main.ts
@@ -332,6 +332,8 @@ authStore.subscribe((state) => {
     dispatcherCleanup?.();
     dispatcherCleanup = null;
     ws.disconnect();
+    lastConnectToken = "";
+    lastConnectHost = "";
     // Clear stored credential on logout
     const host = api.getConfig().host;
     if (host) {
diff --git a/Client/tauri-client/src/pages/MainPage.ts b/Client/tauri-client/src/pages/MainPage.ts
index 5aae27a0..b869da48 100644
--- a/Client/tauri-client/src/pages/MainPage.ts
+++ b/Client/tauri-client/src/pages/MainPage.ts
@@ -496,8 +496,27 @@ export function createMainPage(options: MainPageOptions): MountableComponent {
     });
     unsubscribers.push(() => clearOnRemoteVideo());
 
-    // Subscribe to voice store for camera state changes
-    unsubscribers.push(voiceStore.subscribe(() => videoModeCtrl?.checkVideoMode()));
+    // Subscribe to voice store for camera state changes only (not speaking ticks)
+    let prevLocalCamera = voiceStore.getState().localCamera;
+    let prevCameraSignature = "";
+    unsubscribers.push(voiceStore.subscribe((state) => {
+      // Build a lightweight signature of camera-relevant state
+      let sig = state.localCamera ? "1" : "0";
+      const channelId = state.currentChannelId;
+      if (channelId !== null) {
+        const users = state.voiceUsers.get(channelId);
+        if (users) {
+          for (const [uid, u] of users) {
+            if (u.camera) sig += `:${uid}`;
+          }
+        }
+      }
+      if (sig !== prevCameraSignature || state.localCamera !== prevLocalCamera) {
+        prevCameraSignature = sig;
+        prevLocalCamera = state.localCamera;
+        videoModeCtrl?.checkVideoMode();
+      }
+    }));
 
     // Auto-update notifier — checks server for newer client version
     if (apiConfig.host) {
diff --git a/Client/tauri-client/src/pages/main-page/VideoModeController.ts b/Client/tauri-client/src/pages/main-page/VideoModeController.ts
index a91fbab4..b974487c 100644
--- a/Client/tauri-client/src/pages/main-page/VideoModeController.ts
+++ b/Client/tauri-client/src/pages/main-page/VideoModeController.ts
@@ -46,6 +46,8 @@ export function createVideoModeController(
 ): VideoModeController {
   const { slots, videoGrid, getCurrentUserId } = opts;
   let videoMode = false;
+  /** Track whether we've already added the local self-view tile. */
+  let localTileAdded = false;
 
   function showVideoGrid(): void {
     if (videoMode) return;
@@ -94,20 +96,26 @@ export function createVideoModeController(
       showChat();
     }
 
-    // Manage local self-view tile
+    // Manage local self-view tile — only add once, skip if already showing
     const currentUserId = getCurrentUserId();
     if (voice.localCamera) {
-      const localStream = getLocalCameraStream();
-      if (localStream !== null) {
-        const me = channelUsers.get(currentUserId);
-        videoGrid.addStream(
-          currentUserId,
-          me?.username ? `${me.username} (You)` : "You",
-          localStream,
-        );
+      if (!localTileAdded) {
+        const localStream = getLocalCameraStream();
+        if (localStream !== null) {
+          const me = channelUsers.get(currentUserId);
+          videoGrid.addStream(
+            currentUserId,
+            me?.username ? `${me.username} (You)` : "You",
+            localStream,
+          );
+          localTileAdded = true;
+        }
       }
     } else {
-      videoGrid.removeStream(currentUserId);
+      if (localTileAdded) {
+        videoGrid.removeStream(currentUserId);
+        localTileAdded = false;
+      }
     }
 
     // Remove remote video tiles for users who turned off their camera
@@ -126,6 +134,7 @@ export function createVideoModeController(
 
   function destroy(): void {
     if (videoMode) showChat();
+    localTileAdded = false;
   }
 
   return {
diff --git a/Server/config/config.go b/Server/config/config.go
index a77fbade..b4d68047 100644
--- a/Server/config/config.go
+++ b/Server/config/config.go
@@ -3,6 +3,7 @@ package config
 
 import (
 	"fmt"
+	"log/slog"
 	"os"
 	"strings"
 
@@ -207,6 +208,14 @@ func Load(cfgPath string) (*Config, error) {
 	// the YAML section is present but fields are commented out / omitted).
 	applyVoiceDefaults(&cfg.Voice)
 
+	// Warn if using default dev credentials — these are public and insecure.
+	if cfg.Voice.LiveKitAPISecret == "owncord-dev-secret-key-min-32chars" {
+		slog.Warn("using default LiveKit API secret — change voice.livekit_api_secret in config.yaml for production")
+	}
+	if cfg.Voice.LiveKitAPIKey == "devkey" {
+		slog.Warn("using default LiveKit API key — change voice.livekit_api_key in config.yaml for production")
+	}
+
 	return &cfg, nil
 }
 
diff --git a/Server/ws/client.go b/Server/ws/client.go
index bfdd02b2..e6687ca5 100644
--- a/Server/ws/client.go
+++ b/Server/ws/client.go
@@ -108,6 +108,13 @@ func NewTestClientWithTokenHash(hub *Hub, user *db.User, tokenHash string, chann
 	}
 }
 
+// getChannelID returns the currently focused channel ID under mu.
+func (c *Client) getChannelID() int64 {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	return c.channelID
+}
+
 // getVoiceChID returns the voice channel ID under voiceMu.
 func (c *Client) getVoiceChID() int64 {
 	c.voiceMu.Lock()
@@ -146,6 +153,22 @@ func (c *Client) sendMsg(msg []byte) {
 	}
 }
 
+// trySendMsg queues a message and returns true if it was accepted, false if
+// the buffer is full or the channel is closed.
+func (c *Client) trySendMsg(msg []byte) bool {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	if c.sendClosed {
+		return false
+	}
+	select {
+	case c.send <- msg:
+		return true
+	default:
+		return false
+	}
+}
+
 // closeSend marks the send channel closed and closes it exactly once.
 // Safe to call from any goroutine.
 func (c *Client) closeSend() {
diff --git a/Server/ws/handlers.go b/Server/ws/handlers.go
index e5be58a9..a2430f58 100644
--- a/Server/ws/handlers.go
+++ b/Server/ws/handlers.go
@@ -483,13 +483,10 @@ func (h *Hub) broadcastExclude(channelID, excludeUserID int64, msg []byte) {
 		if uid == excludeUserID {
 			continue
 		}
-		if channelID != 0 && c.channelID != channelID {
+		if channelID != 0 && c.getChannelID() != channelID {
 			continue
 		}
-		select {
-		case c.send <- msg:
-		default:
-		}
+		c.sendMsg(msg)
 	}
 }
 
diff --git a/Server/ws/hub.go b/Server/ws/hub.go
index 97d0db98..6618d361 100644
--- a/Server/ws/hub.go
+++ b/Server/ws/hub.go
@@ -258,13 +258,7 @@ func (h *Hub) SendToUser(userID int64, msg []byte) bool {
 	if !ok {
 		return false
 	}
-	select {
-	case c.send <- msg:
-		return true
-	default:
-		// send buffer full — drop rather than block.
-		return false
-	}
+	return c.trySendMsg(msg)
 }
 
 // ClientCount returns the number of currently registered clients (test helper).
@@ -295,17 +289,12 @@ func (h *Hub) deliverBroadcast(bm broadcastMsg) {
 	skipped := 0
 	for _, c := range h.clients {
 		// channelID == 0 → broadcast to everyone.
-		if bm.channelID != 0 && c.channelID != bm.channelID && c.getVoiceChID() != bm.channelID {
+		if bm.channelID != 0 && c.getChannelID() != bm.channelID && c.getVoiceChID() != bm.channelID {
 			skipped++
 			continue
 		}
-		select {
-		case c.send <- bm.msg:
-			delivered++
-		default:
-			slog.Warn("broadcast dropped: client send buffer full",
-				"user_id", c.userID, "channel_id", bm.channelID)
-		}
+		c.sendMsg(bm.msg)
+		delivered++
 	}
 	if bm.channelID != 0 {
 		slog.Debug("hub: channel broadcast",
diff --git a/Server/ws/livekit.go b/Server/ws/livekit.go
index 9134d8e2..36bb528d 100644
--- a/Server/ws/livekit.go
+++ b/Server/ws/livekit.go
@@ -19,7 +19,7 @@ import (
 )
 
 // tokenTTL is the validity duration for generated LiveKit access tokens.
-const tokenTTL = 24 * time.Hour
+const tokenTTL = 4 * time.Hour
 
 // LiveKitClient provides token generation and room management via
 // the LiveKit server SDK.
diff --git a/Server/ws/livekit_process.go b/Server/ws/livekit_process.go
index 74a49f67..e6e1429c 100644
--- a/Server/ws/livekit_process.go
+++ b/Server/ws/livekit_process.go
@@ -64,7 +64,7 @@ logging:
 	if err := os.MkdirAll(p.dataDir, 0o755); err != nil {
 		return "", fmt.Errorf("creating data dir: %w", err)
 	}
-	if err := os.WriteFile(cfgPath, []byte(content), 0o644); err != nil {
+	if err := os.WriteFile(cfgPath, []byte(content), 0o600); err != nil {
 		return "", fmt.Errorf("writing livekit config: %w", err)
 	}
 
diff --git a/Server/ws/voice_handlers.go b/Server/ws/voice_handlers.go
index 98410d8f..7067fd01 100644
--- a/Server/ws/voice_handlers.go
+++ b/Server/ws/voice_handlers.go
@@ -96,6 +96,11 @@ func (h *Hub) handleVoiceJoin(c *Client, payload json.RawMessage) {
 
 	// Generate LiveKit token if LiveKit client is available.
 	if h.livekit != nil {
+		if c.user == nil {
+			slog.Error("handleVoiceJoin: nil user on client", "user_id", c.userID)
+			c.sendMsg(buildErrorMsg("INTERNAL", "not authenticated"))
+			return
+		}
 		canPublish := true
 		canSubscribe := true
 		token, tokenErr := h.livekit.GenerateToken(c.userID, c.user.Username, channelID, canPublish, canSubscribe)