diff --git a/VoidLink/Localization/Localizable.xcstrings b/VoidLink/Localization/Localizable.xcstrings
index 19880a6e..edf4111d 100644
--- a/VoidLink/Localization/Localizable.xcstrings
+++ b/VoidLink/Localization/Localizable.xcstrings
@@ -5090,6 +5090,29 @@
         }
       }
     },
+    "Apply" : {
+      "extractionState" : "stale",
+      "localizations" : {
+        "zh-Hans" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "应用"
+          }
+        },
+        "zh-Hant" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "套用"
+          }
+        },
+        "zh-HK" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "套用"
+          }
+        }
+      }
+    },
     "Arrow direction pad" : {
       "extractionState" : "manual",
       "localizations" : {
@@ -8208,6 +8231,29 @@
         }
       }
     },
+    "Enable Metal Renderer?" : {
+      "extractionState" : "stale",
+      "localizations" : {
+        "zh-Hans" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "启用 Metal 渲染？"
+          }
+        },
+        "zh-Hant" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "啟用 Metal 渲染？"
+          }
+        },
+        "zh-HK" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "啟用 Metal 渲染？"
+          }
+        }
+      }
+    },
     "enableOswForNativeTouchSwitchTip" : {
       "extractionState" : "manual",
       "localizations" : {
@@ -10923,6 +10969,98 @@
         }
       }
     },
+    "Interpolation failed for an unknown reason." : {
+      "extractionState" : "manual",
+      "localizations" : {
+        "zh-Hans" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "未知原因导致的插帧失败"
+          }
+        },
+        "zh-Hant" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "未知原因導致插幀失敗"
+          }
+        },
+        "zh-HK" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "未知原因導致插幀失敗"
+          }
+        }
+      }
+    },
+    "Interpolation overhead is too high. Falling back to normal mode." : {
+      "extractionState" : "manual",
+      "localizations" : {
+        "zh-Hans" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "插帧性能开销过大，回退普通模式"
+          }
+        },
+        "zh-Hant" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "插幀效能開銷過大，回退至一般模式"
+          }
+        },
+        "zh-HK" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "插幀效能開銷過大，回退至一般模式"
+          }
+        }
+      }
+    },
+    "Interpolator error:" : {
+      "extractionState" : "manual",
+      "localizations" : {
+        "zh-Hans" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "插帧器错误："
+          }
+        },
+        "zh-Hant" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "插幀器錯誤："
+          }
+        },
+        "zh-HK" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "插幀器錯誤："
+          }
+        }
+      }
+    },
+    "Interpolator started." : {
+      "extractionState" : "manual",
+      "localizations" : {
+        "zh-Hans" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "插帧器已启动。"
+          }
+        },
+        "zh-Hant" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "插幀器已啟動。"
+          }
+        },
+        "zh-HK" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "插幀器已啟動。"
+          }
+        }
+      }
+    },
     "Interval of Multi-Touch Move Events: %d μs" : {
       "extractionState" : "manual",
       "localizations" : {
@@ -12233,25 +12371,25 @@
         "en" : {
           "stringUnit" : {
             "state" : "translated",
-            "value" : "\nHold up! \n\n- Standard render has better performance on most devices now.\n\n- Changing the rendering mode requires restarting the application to ensure a clean start.\n\n- Metal rendering is an experimental feature that may cause performance degradation on some devices.\n\n- Metal render currently is unable to handle HDR content correctly on most devices.\n\n- Metal rendering mode does not support PiP.\n\n- Tapping “Quit Now” means I acknowledge the above information."
+            "value" : "\nHold up! \n\n- Standard render has better performance on most devices now.\n\n- The change takes effect the next time you start a stream. No app restart is needed.\n\n- Metal rendering is an experimental feature that may cause performance degradation on some devices.\n\n- Metal render currently is unable to handle HDR content correctly on most devices.\n\n- Metal rendering mode does not support PiP.\n\n- Tapping “Apply” means I acknowledge the above information."
           }
         },
         "zh-Hans" : {
           "stringUnit" : {
             "state" : "translated",
-            "value" : "\n等等！\n\n- 标准渲染模式目前在大多数设备上具有更好的性能。\n\n- 切换渲染模式需要重启应用程序，以确保一次干净的启动。\n\n- Metal 渲染是一项实验性功能，在某些设备上可能会导致性能下降。\n\n- Metal 渲染模式下不支持画中画。\n\n- 目前 Metal 渲染器在大多数设备上无法正确处理 HDR 内容。\n\n点击“立即退出”表示我已知晓并认可以上信息。"
+            "value" : "\n等等！\n\n- 标准渲染模式目前在大多数设备上具有更好的性能。\n\n- 渲染模式的更改将在下次开始串流时生效，无需重启应用程序。\n\n- Metal 渲染是一项实验性功能，在某些设备上可能会导致性能下降。\n\n- Metal 渲染模式下不支持画中画。\n\n- 目前 Metal 渲染器在大多数设备上无法正确处理 HDR 内容。\n\n点击“应用”表示我已知晓并认可以上信息。"
           }
         },
         "zh-Hant" : {
           "stringUnit" : {
             "state" : "translated",
-            "value" : "\n等等！\n\n- 目前在大多数装置上，標準渲染模式具有较佳的效能。\n\n- 变更渲染模式需要重新启动应用程式，以确保干净的启动流程。\n\n- Metal 渲染为实验性功能，可能在某些装置上造成效能下降。\n\n- Metal 渲染模式下不支援画中画。\n\n- Metal 渲染器目前在大多数装置上无法正确处理 HDR 内容。\n\n点选「立即结束」表示我已了解并同意上述说明。"
+            "value" : "\n等等！\n\n- 目前在大多数装置上，標準渲染模式具有较佳的效能。\n\n- 变更渲染模式将在下次开始串流时生效，无需重新启动应用程式。\n\n- Metal 渲染为实验性功能，可能在某些装置上造成效能下降。\n\n- Metal 渲染模式下不支援画中画。\n\n- Metal 渲染器目前在大多数装置上无法正确处理 HDR 内容。\n\n点选「套用」表示我已了解并同意上述说明。"
           }
         },
         "zh-HK" : {
           "stringUnit" : {
             "state" : "translated",
-            "value" : "\n等等！\n\n- 目前在大多数装置上，標準渲染模式具有较佳的效能。\n\n- 变更渲染模式需要重新启动应用程式，以确保干净的启动流程。\n\n- Metal 渲染为实验性功能，可能在某些装置上造成效能下降。\n\n- Metal 渲染模式下不支援画中画。\n\n- Metal 渲染器目前在大多数装置上无法正确处理 HDR 内容。\n\n点选「立即结束」表示我已了解并同意上述说明。"
+            "value" : "\n等等！\n\n- 目前在大多数装置上，標準渲染模式具有较佳的效能。\n\n- 变更渲染模式将在下次开始串流时生效，无需重新启动应用程式。\n\n- Metal 渲染为实验性功能，可能在某些装置上造成效能下降。\n\n- Metal 渲染模式下不支援画中画。\n\n- Metal 渲染器目前在大多数装置上无法正确处理 HDR 内容。\n\n点选「套用」表示我已了解并同意上述说明。"
           }
         }
       }
@@ -15659,25 +15797,25 @@
         "en" : {
           "stringUnit" : {
             "state" : "translated",
-            "value" : "- Standard render has better performance on most devices now.\n\n- Changing the rendering mode requires restarting the application to ensure a clean start.\n\n- Metal rendering is an experimental feature that may cause performance degradation on some devices.\n\n- Metal render currently is unable to handle HDR content correctly on most devices.\n\n- Metal rendering mode does not support PiP."
+            "value" : "- Standard render has better performance on most devices now.\n\n- Changing the rendering mode takes effect the next time you start a stream.\n\n- Metal rendering is an experimental feature that may cause performance degradation on some devices.\n\n- Metal render currently is unable to handle HDR content correctly on most devices.\n\n- Metal rendering mode does not support PiP."
           }
         },
         "zh-Hans" : {
           "stringUnit" : {
             "state" : "translated",
-            "value" : "- 目前, 标准渲染模式在大多数设备上具有更好的性能。\n\n- 切换渲染模式需要重启应用程序，以确保一次干净的启动。\n\n- Metal 渲染是一项实验性功能，在某些设备上可能会导致性能下降。\n\n- Metal 渲染模式下不支持画中画。\n\n- 目前 Metal 渲染器在大多数设备上无法正确处理 HDR 内容。\n"
+            "value" : "- 目前, 标准渲染模式在大多数设备上具有更好的性能。\n\n- 渲染模式的更改将在下次开始串流时生效。\n\n- Metal 渲染是一项实验性功能，在某些设备上可能会导致性能下降。\n\n- Metal 渲染模式下不支持画中画。\n\n- 目前 Metal 渲染器在大多数设备上无法正确处理 HDR 内容。"
           }
         },
         "zh-Hant" : {
           "stringUnit" : {
             "state" : "translated",
-            "value" : "- 目前，在大多数装置上，標準渲染模式具有较佳的效能。\n\n- 变更渲染模式需要重新启动应用程式，以确保干净的启动流程。\n\n- Metal 渲染为实验性功能，可能在某些装置上造成效能下降。\n\n- Metal 渲染模式下不支援画中画。\n\n- Metal 渲染器目前在大多数装置上无法正确处理 HDR 内容。"
+            "value" : "- 目前，在大多数装置上，標準渲染模式具有较佳的效能。\n\n- 变更渲染模式将在下次开始串流时生效。\n\n- Metal 渲染为实验性功能，可能在某些装置上造成效能下降。\n\n- Metal 渲染模式下不支援画中画。\n\n- Metal 渲染器目前在大多数装置上无法正确处理 HDR 内容。"
           }
         },
         "zh-HK" : {
           "stringUnit" : {
             "state" : "translated",
-            "value" : "- 目前，在大多数装置上，標準渲染模式具有较佳的效能。\n\n- 变更渲染模式需要重新启动应用程式，以确保干净的启动流程。\n\n- Metal 渲染为实验性功能，可能在某些装置上造成效能下降。\n\n- Metal 渲染模式下不支援画中画。\n\n- Metal 渲染器目前在大多数装置上无法正确处理 HDR 内容。"
+            "value" : "- 目前，在大多数装置上，標準渲染模式具有较佳的效能。\n\n- 变更渲染模式将在下次开始串流时生效。\n\n- Metal 渲染为实验性功能，可能在某些装置上造成效能下降。\n\n- Metal 渲染模式下不支援画中画。\n\n- Metal 渲染器目前在大多数装置上无法正确处理 HDR 内容。"
           }
         }
       }
@@ -17613,25 +17751,25 @@
         "en" : {
           "stringUnit" : {
             "state" : "translated",
-            "value" : "\n- Standard render has better performance on most devices now.\n\n- Changing the rendering mode requires restarting the application to ensure a clean start."
+            "value" : "\n- Standard render has better performance on most devices now.\n\n- The change takes effect the next time you start a stream."
           }
         },
         "zh-Hans" : {
           "stringUnit" : {
             "state" : "translated",
-            "value" : "\n- 标准渲染模式目前在大多数设备上具有更好的性能。\n\n- 更改渲染模式需要重启应用以确保干净启动。您是否要立即退出应用？"
+            "value" : "\n- 目前, 标准渲染模式在大多数设备上具有更好的性能。\n\n- 渲染模式的更改将在下次开始串流时生效。"
           }
         },
         "zh-Hant" : {
           "stringUnit" : {
             "state" : "translated",
-            "value" : "\n- 目前在大多数装置上，標準渲染模式具有较佳的效能。\n\n- 更改渲染模式需要重新啟動應用程式以確保乾淨啟動。您是否要立即退出應用程式？"
+            "value" : "\n- 目前，在大多数装置上，標準渲染模式具有较佳的效能。\n\n- 变更渲染模式将在下次开始串流时生效。"
           }
         },
         "zh-HK" : {
           "stringUnit" : {
             "state" : "translated",
-            "value" : "\n- 目前在大多数装置上，標準渲染模式具有较佳的效能。\n\n- 更改渲染模式需要重新啟動應用程式以確保乾淨啟動。您是否要立即退出應用程式？"
+            "value" : "\n- 目前，在大多数装置上，標準渲染模式具有较佳的效能。\n\n- 变更渲染模式将在下次开始串流时生效。"
           }
         }
       }
diff --git a/VoidLink/Metal/MetalVideoRenderer.m b/VoidLink/Metal/MetalVideoRenderer.m
index 715499e4..55d72125 100644
--- a/VoidLink/Metal/MetalVideoRenderer.m
+++ b/VoidLink/Metal/MetalVideoRenderer.m
@@ -106,7 +106,17 @@ static const NSUInteger MaxFramesInFlight = 3;
 // best to tone-map Windows content
 static BOOL useEDR = YES;
 
-CFStringRef __currentColorSpace;
+// Name of the colorspace most recently applied to the layer, for the stats overlay.
+// Class-level because the stats path only has access to the class; guarded by a lock
+// since it is written on the render thread and read from other threads, and multiple
+// renderer instances can briefly overlap during a session switch.
+static NSString *__currentColorSpace;
+
+static void setCurrentColorSpaceName(NSString *name) {
+    @synchronized ([MetalVideoRenderer class]) {
+        __currentColorSpace = name;
+    }
+}
 
 @implementation MetalVideoRenderer {
     dispatch_queue_t _sq;
@@ -225,11 +235,9 @@ CFStringRef __currentColorSpace;
     if (_renderPassDescriptor) {
         _renderPassDescriptor = nil;
     }
-    
-    if (__currentColorSpace) {
-        CFRelease(__currentColorSpace);
-        __currentColorSpace = NULL;
-    }
+
+    // Do NOT clear __currentColorSpace here: a new renderer instance may already be
+    // live (session switch) and have set its own value.
 }
 
 #if !TARGET_OS_TV
@@ -405,9 +413,11 @@ CFStringRef __currentColorSpace;
                 paramBuffer.cscParams = (fullRange ? k_CscParams_Bt709Full : k_CscParams_Bt709Lim);
                 break;
             case COLORSPACE_REC_2020: {
+                // Frames without a format description (e.g. produced for the AVSB
+                // backend) must not crash us here
                 CFDictionaryRef ext = [frame getFormatDescExtensions];
-                CFStringRef frame_trc = CFDictionaryGetValue(ext, kCVImageBufferTransferFunctionKey);
-                if (CFEqual(frame_trc, kCVImageBufferTransferFunction_SMPTE_ST_2084_PQ)) {
+                CFStringRef frame_trc = ext ? CFDictionaryGetValue(ext, kCVImageBufferTransferFunctionKey) : NULL;
+                if (frame_trc && CFEqual(frame_trc, kCVImageBufferTransferFunction_SMPTE_ST_2084_PQ)) {
                     isHDR = YES;
                     newColorSpace = CGColorSpaceCreateWithName(_nonFullHdrColorSpace);
                     newPixelFormat = _nonFullHdrPixelFormat;
@@ -478,11 +488,7 @@ CFStringRef __currentColorSpace;
                 });
             }
 #endif
-            if (__currentColorSpace) {
-                CFRelease(__currentColorSpace);
-                __currentColorSpace = NULL;
-            }
-            __currentColorSpace = CGColorSpaceCopyName(newColorSpace);
+            setCurrentColorSpaceName(newColorSpace ? CFBridgingRelease(CGColorSpaceCopyName(newColorSpace)) : nil);
             CGColorSpaceRelease(newColorSpace);
         }
 
@@ -904,10 +910,9 @@ CFStringRef __currentColorSpace;
 }
 
 + (NSString *)currentColorSpace {
-    if (__currentColorSpace) {
-        return (__bridge NSString *)__currentColorSpace;
+    @synchronized ([MetalVideoRenderer class]) {
+        return __currentColorSpace;
     }
-    return nil;
 }
 
 @end
diff --git a/VoidLink/Metal/MetalView.h b/VoidLink/Metal/MetalView.h
index 4564f51d..b93212b2 100644
--- a/VoidLink/Metal/MetalView.h
+++ b/VoidLink/Metal/MetalView.h
@@ -24,7 +24,9 @@
 @interface MetalView : UIView <CALayerDelegate>
 
 @property (nonatomic, nonnull, readonly) CAMetalLayer *metalLayer;
-@property (nonatomic, nullable) id<MetalViewDelegate> delegate;
+// weak: the delegate (MetalViewController) strongly owns this view; a strong
+// reference here creates a retain cycle that leaks the whole Metal stack.
+@property (nonatomic, weak, nullable) id<MetalViewDelegate> delegate;
 @property (nonatomic) float framerate;
 
 - (void)initCommon;
diff --git a/VoidLink/Metal/MetalView.m b/VoidLink/Metal/MetalView.m
index ca967738..361d3e38 100644
--- a/VoidLink/Metal/MetalView.m
+++ b/VoidLink/Metal/MetalView.m
@@ -45,10 +45,20 @@
         Log(LOG_I, @"[MetalView] sending renderThread a cancel message");
         [_renderThread cancel];
         Log(LOG_I, @"[MetalView] waiting on renderThread to finish");
-        while (!_renderThread.isFinished) {
+        // Bounded wait only: shutdown typically runs on the main thread, and the render
+        // thread may be blocked in a dispatch_sync onto the main queue (layer colorspace
+        // changes). Spinning here forever would deadlock; if we time out, the thread
+        // exits on its own once the main queue is serviced again (it retains the view
+        // via its block, so this is safe).
+        CFTimeInterval deadline = CACurrentMediaTime() + 1.0;
+        while (!_renderThread.isFinished && CACurrentMediaTime() < deadline) {
             usleep(100);
         }
-        Log(LOG_I, @"[MetalView] renderThread has finished");
+        if (_renderThread.isFinished) {
+            Log(LOG_I, @"[MetalView] renderThread has finished");
+        } else {
+            Log(LOG_W, @"[MetalView] renderThread still busy after 1s, letting it exit asynchronously");
+        }
         _renderThread = nil;
     }
 }
@@ -68,6 +78,13 @@
         return;
     }
 
+    // Never run two render loops at once (the view can move between windows,
+    // e.g. external display or re-parenting)
+    if (_renderThread) {
+        Log(LOG_W, @"[MetalView] movedToWindow with a live renderThread, restarting it");
+        [self shutdown];
+    }
+
     // Render on a new thread
     _renderThread = [[NSThread alloc] initWithBlock:^{
         while (![NSThread currentThread].isCancelled) {
diff --git a/VoidLink/Metal/MetalViewController.h b/VoidLink/Metal/MetalViewController.h
index c9264a39..c240f520 100644
--- a/VoidLink/Metal/MetalViewController.h
+++ b/VoidLink/Metal/MetalViewController.h
@@ -24,4 +24,8 @@
 - (void)pauseRendering;
 - (void)resumeRendering;
 
+// Idempotent teardown: stops the render thread, display link and renderer.
+// Must be called when the stream session ends; also runs from viewDidDisappear.
+- (void)shutdown;
+
 @end
diff --git a/VoidLink/Metal/MetalViewController.m b/VoidLink/Metal/MetalViewController.m
index 2f4b56b9..d8496fe4 100644
--- a/VoidLink/Metal/MetalViewController.m
+++ b/VoidLink/Metal/MetalViewController.m
@@ -109,13 +109,18 @@
 }
 
 - (void)waitToRenderTo:(nonnull CAMetalLayer *)layer {
-    // Skip waiting when renderer is paused
-    if (_renderer.isStopping) {
+    // Snapshot into a strong local: shutdown (main thread) can nil _renderer while
+    // the render thread is inside this method.
+    MetalVideoRenderer *renderer = _renderer;
+
+    // Skip waiting when renderer is paused or gone
+    if (!renderer || renderer.isStopping) {
+        _frameSlotAcquired = NO;
         return;
     }
 
     if (@available(iOS 13.0, *)) {
-        _frameSlotAcquired = [_renderer waitToRenderTo:layer];
+        _frameSlotAcquired = [renderer waitToRenderTo:layer];
     }
 
     if (_frameSlotAcquired) {
@@ -128,22 +133,27 @@
     if (!_frameSlotAcquired) {
         return;
     }
-    CFTimeInterval timeout = (1.0f / _framerate) - _renderer.averageGPUTime;
+    // Snapshot for the same reason as in waitToRenderTo
+    MetalVideoRenderer *renderer = _renderer;
+    if (!renderer) {
+        return;
+    }
+    CFTimeInterval timeout = (1.0f / _framerate) - renderer.averageGPUTime;
     Frame *frame = [_frameQueue dequeueWithTimeoutSync:timeout];
 
-    if (!_renderer.isStopping) {
+    if (!renderer.isStopping) {
         // Only render if not paused
         if (frame) {
             //if (@available(iOS 13.0, *)) {
-                [_renderer renderFrame:frame toLayer:layer];
+                [renderer renderFrame:frame toLayer:layer];
             //}
         } else {
-            dispatch_semaphore_signal([_renderer inFlightSemaphore]);
+            dispatch_semaphore_signal([renderer inFlightSemaphore]);
         }
     } else {
         // When paused, we still dequeue frames to prevent accumulation
         // but don't render them. Also sleep a bit to reduce CPU usage
-        dispatch_semaphore_signal([_renderer inFlightSemaphore]);
+        dispatch_semaphore_signal([renderer inFlightSemaphore]);
         usleep(100000);
     }
 }
@@ -177,11 +187,18 @@
 
     Log(LOG_I, @"[MetalViewController] viewDidDisappear");
 
+    [self shutdown];
+}
+
+- (void)shutdown {
     if (_displayLink) {
         [_displayLink invalidate];
         _displayLink = nil;
     }
 
+    // Stop the renderer before the render thread: isStopping makes the thread's
+    // renderFrame return early, so it can't enter the dispatch_sync-to-main path
+    // while we wait for it below.
     if (_renderer) {
         [_renderer shutdown];
         _renderer = nil;
diff --git a/VoidLink/Stream/Connection.m b/VoidLink/Stream/Connection.m
index 0354a405..b51d6f8a 100644
--- a/VoidLink/Stream/Connection.m
+++ b/VoidLink/Stream/Connection.m
@@ -80,6 +80,10 @@ int DrDecoderSetup(int videoFormat, int width, int height, int redrawRate, void*
 void DrCleanup(void)
 {
     [renderer cleanup];
+    // Drop the static reference so the old renderer (and its decoder resources)
+    // doesn't outlive the session; otherwise it stays alive until the next
+    // Connection init overwrites it, which can interleave with a new session.
+    renderer = nil;
 }
 
 -(BandwidthTracker *) getBwTracker
diff --git a/VoidLink/Stream/VideoDecoderRenderer.m b/VoidLink/Stream/VideoDecoderRenderer.m
index 9c7e9099..f1b8d73e 100644
--- a/VoidLink/Stream/VideoDecoderRenderer.m
+++ b/VoidLink/Stream/VideoDecoderRenderer.m
@@ -77,6 +77,12 @@ extern int ff_isom_write_av1c(AVIOContext *pb, const uint8_t *buf, int size,
     FramePacingMode _framePacingMode;
     bool _enableTimebase;
     bool _asyncFrameDequeue;
+
+    // Cached UIApplication background state. UIKit's applicationState must only be
+    // read on the main thread, but the decode path needs it on the VTDecoder queue.
+    // Updated on the main thread via notifications; a stale read here is harmless
+    // (it only gates metrics collection).
+    volatile BOOL _appInBackground;
         
     // CMTime playTime;
     // NSTimeInterval previousLinkTime;
@@ -207,7 +213,7 @@ extern int ff_isom_write_av1c(AVIOContext *pb, const uint8_t *buf, int size,
     _needRequeuing = _queueSize>0;
 
     _frameQueue = [FrameQueue sharedInstance];
-    [_frameQueue start];
+    [_frameQueue startForOwner:self];
     [_frameQueue setHighWaterMark:MAX(1, _queueSize)];
 
     [self reinitializeDisplayLayer];
@@ -222,6 +228,18 @@ extern int ff_isom_write_av1c(AVIOContext *pb, const uint8_t *buf, int size,
         sActiveRenderer = self;
     }
 
+    // Renderer init runs on the main thread, so reading applicationState here is legal.
+    // The decode queue reads the cached flag instead (UIKit forbids off-main reads).
+    _appInBackground = ([UIApplication sharedApplication].applicationState == UIApplicationStateBackground);
+    [[NSNotificationCenter defaultCenter] addObserver:self
+                                             selector:@selector(appDidEnterBackground)
+                                                 name:UIApplicationDidEnterBackgroundNotification
+                                               object:nil];
+    [[NSNotificationCenter defaultCenter] addObserver:self
+                                             selector:@selector(appWillEnterForeground)
+                                                 name:UIApplicationWillEnterForegroundNotification
+                                               object:nil];
+
     return self;
 }
 
@@ -327,6 +345,14 @@ extern int ff_isom_write_av1c(AVIOContext *pb, const uint8_t *buf, int size,
     });
 }
 
+- (void)appDidEnterBackground {
+    _appInBackground = YES;
+}
+
+- (void)appWillEnterForeground {
+    _appInBackground = NO;
+}
+
 # pragma mark DisplayLink vsync callback
 
 - (void)setupWithVideoFormat:(int)videoFormat width:(int)videoWidth height:(int)videoHeight frameRate:(int)frameRate fullRange:(BOOL)fullRange request10BitCodec:(BOOL)request10BitCodec
@@ -570,7 +596,7 @@ int DrSubmitDecodeUnit(PDECODE_UNIT decodeUnit);
                         // we missed a callback
                         // Log(LOG_W, @"*** slow frametime %.3f ms", frametime * 1000.0);
                     }
-                    if ([[UIApplication sharedApplication] applicationState] != UIApplicationStateBackground) {
+                    if (!self->_appInBackground) {
                         [[ImGuiPlots sharedInstance] observeFloat:PLOT_FRAMETIME value:frametime * 1000.0];
                     }
                 }
@@ -675,7 +701,7 @@ int DrSubmitDecodeUnit(PDECODE_UNIT decodeUnit);
     }
 
     dispatch_async(dispatch_get_main_queue(), ^{
-        [self->_frameQueue stop];
+        [self->_frameQueue stopForOwner:self];
         
         if (self->_renderingBackend == RENDER_AVSB) {
             [self->_displayLink invalidate];
@@ -1310,7 +1336,7 @@ int DrSubmitDecodeUnit(PDECODE_UNIT decodeUnit);
                                     framesDropped += [self->_frameQueue enqueue:outputFrame withSlackSize:3];
                                 }
 
-                                if ([[UIApplication sharedApplication] applicationState] != UIApplicationStateBackground) {
+                                if (!self->_appInBackground) {
                                     static PlotMetrics frameQueueMetrics = {};
                                     [[ImGuiPlots sharedInstance] observeFloatReturnMetrics:PLOT_QUEUED_FRAMES value:[self->_frameQueue count] plotMetrics:&frameQueueMetrics];
                                     [self safeCopyMetricsTo:&self->_frameQueueMetrics from:&frameQueueMetrics];
@@ -1334,7 +1360,7 @@ int DrSubmitDecodeUnit(PDECODE_UNIT decodeUnit);
 
                     int framesDropped = [self->_frameQueue enqueue:frame withSlackSize:3];
 
-                    if ([[UIApplication sharedApplication] applicationState] != UIApplicationStateBackground) {
+                    if (!self->_appInBackground) {
                         static PlotMetrics frameQueueMetrics = {};
                         [[ImGuiPlots sharedInstance] observeFloatReturnMetrics:PLOT_QUEUED_FRAMES value:[self->_frameQueue count] plotMetrics:&frameQueueMetrics];
                         [self safeCopyMetricsTo:&self->_frameQueueMetrics from:&frameQueueMetrics];
diff --git a/VoidLink/Utility/Frame.m b/VoidLink/Utility/Frame.m
index f69c25af..c7c34707 100644
--- a/VoidLink/Utility/Frame.m
+++ b/VoidLink/Utility/Frame.m
@@ -108,7 +108,11 @@ static char FrameInterpolatedKey;
 
 - (CFDictionaryRef)getFormatDescExtensions {
     if (!_formatDescExt && _formatDesc) {
-        _formatDescExt = CFRetain(CMFormatDescriptionGetExtensions(_formatDesc));
+        // Can legitimately be NULL, and CFRetain(NULL) crashes
+        CFDictionaryRef ext = CMFormatDescriptionGetExtensions(_formatDesc);
+        if (ext) {
+            _formatDescExt = CFRetain(ext);
+        }
     }
     return _formatDescExt;
 }
diff --git a/VoidLink/Utility/FrameQueue.h b/VoidLink/Utility/FrameQueue.h
index 610d7e0d..d70d8a60 100644
--- a/VoidLink/Utility/FrameQueue.h
+++ b/VoidLink/Utility/FrameQueue.h
@@ -29,8 +29,8 @@ NS_ASSUME_NONNULL_BEGIN
 - (CFTimeInterval)estimatedFramerate;
 - (int)currentSoftCap;
 - (void)waitForEnqueue;
-- (void)start;
-- (void)stop;
+- (void)startForOwner:(id)owner;
+- (void)stopForOwner:(id)owner;
 
 @end
 
diff --git a/VoidLink/Utility/FrameQueue.m b/VoidLink/Utility/FrameQueue.m
index f59e1281..d47177e6 100644
--- a/VoidLink/Utility/FrameQueue.m
+++ b/VoidLink/Utility/FrameQueue.m
@@ -24,6 +24,10 @@
     int _currentSoftCap;
     dispatch_queue_t _sq;
     dispatch_semaphore_t _frameSemaphore;
+
+    // The renderer session currently consuming from the queue. A stale session's
+    // async stop must not pause a newer session's queue.
+    __weak id _owner;
 }
 
 + (instancetype)sharedInstance {
@@ -301,7 +305,14 @@
 
 - (void)clear {
     os_unfair_lock_lock(&_lock);
+    // Release any frames still held in the ring buffer, otherwise their
+    // pixel/sample buffers stay retained for the lifetime of the singleton.
+    for (int i = 0; i < _capacity; i++) {
+        [_buffer replaceObjectAtIndex:i withObject:[NSNull null]];
+    }
     _head = _tail = _count = 0;
+    _droppedLast = NO;
+    _ptsCorrection = CMTimeMake(0, 90000);
     _frameDropMetrics = [[FloatBuffer alloc] initWithCapacity:512];
     os_unfair_lock_unlock(&_lock);
 }
@@ -336,15 +347,31 @@
     return cap;
 }
 
-- (void)stop {
+- (void)stopForOwner:(id)owner {
+    @synchronized (self) {
+        // Ignore stops from a previous session: cleanup is dispatched async and can
+        // land after a new renderer has already (re)started the queue.
+        if (_owner != nil && owner != _owner) {
+            Log(LOG_W, @"FrameQueue stop ignored: %p is not the current owner", owner);
+            return;
+        }
+        _owner = nil;
+    }
     // new frames will no longer be coming in, make sure consumer side is not left waiting
     self.paused = YES;
     Log(LOG_I, @"FrameQueue stopped");
     dispatch_semaphore_signal(_frameSemaphore);
+    // Don't keep the previous session's frames (and their pixel buffers) alive
+    [self clear];
 }
 
-- (void)start {
-    // (re)start for a new renderer
+- (void)startForOwner:(id)owner {
+    @synchronized (self) {
+        _owner = owner;
+    }
+    // Drop any frames left over from a previous renderer session; feeding them to a
+    // renderer with a different backend or video format can crash it.
+    [self clear];
     self.paused = NO;
     Log(LOG_I, @"FrameQueue started");
 }
diff --git a/VoidLink/ViewControllers/SettingsViewController.m b/VoidLink/ViewControllers/SettingsViewController.m
index 19b89071..be63526b 100644
--- a/VoidLink/ViewControllers/SettingsViewController.m
+++ b/VoidLink/ViewControllers/SettingsViewController.m
@@ -2681,39 +2681,55 @@ BOOL isCustomResolution(int resolutionSelected) {
 
     // Check if the rendering backend has actually changed
     if (previousBackend != sender.selectedSegmentIndex) {
-        // Show alert to prompt user to restart the app
-        NSString *message = [LocalizationHelper localizedStringForKey: sender.selectedSegmentIndex == 1 ? @"metalRenderTip" : @"standardRenderTip"];
-        
-        UIAlertController *alertController = [UIAlertController alertControllerWithTitle:[LocalizationHelper localizedStringForKey:@"Restart Required"]
-                                                                                 message:message
-                                                                          preferredStyle:UIAlertControllerStyleAlert];
-        
-        UIAlertAction *quitAction = [UIAlertAction actionWithTitle:[LocalizationHelper localizedStringForKey:@"Quit Now"]
-                                                              style:UIAlertActionStyleDefault
-                                                            handler:^(UIAlertAction * _Nonnull action) {
-
+        // The renderer is picked up fresh at every stream start, so the change takes
+        // effect on the next session — no app restart needed.
+        void (^applyChange)(void) = ^{
             Settings* directSettings = [self->dataMan retrieveSettings];
             directSettings.renderingBackend = [NSNumber numberWithInteger:sender.selectedSegmentIndex];
             [self->dataMan saveData];
             [self saveSettings];
-            
-            exit(0);
-        }];
-        
-        UIAlertAction *laterAction = [UIAlertAction actionWithTitle:[LocalizationHelper localizedStringForKey:@"Learn More"]
-                                                               style:UIAlertActionStyleCancel
-                                                             handler:^(UIAlertAction * _Nonnull action) {
-            self.renderingBackendSelector.selectedSegmentIndex = 0;
+        };
+
+        void (^revertChange)(void) = ^{
+            self.renderingBackendSelector.selectedSegmentIndex = previousBackend;
             [self.renderingBackendSelector sendActionsForControlEvents:UIControlEventValueChanged];
-            NSURL *url = [NSURL URLWithString:[LocalizationHelper localizedStringForKey:@"betterPerformanceLink"]];
-            if ([[UIApplication sharedApplication] canOpenURL:url]) {
-                [[UIApplication sharedApplication] openURL:url options:@{} completionHandler:nil];
-            }
-        }];
-        
-        [alertController addAction:laterAction];
-        [alertController addAction:quitAction];
-        [self presentViewController:alertController animated:YES completion:nil];
+        };
+
+        if (sender.selectedSegmentIndex == RENDER_METAL) {
+            // Metal is experimental: confirm its caveats before applying
+            NSString *message = [LocalizationHelper localizedStringForKey:@"metalRenderTip"];
+
+            UIAlertController *alertController = [UIAlertController alertControllerWithTitle:[LocalizationHelper localizedStringForKey:@"Enable Metal Renderer?"]
+                                                                                     message:message
+                                                                              preferredStyle:UIAlertControllerStyleAlert];
+
+            [alertController addAction:[UIAlertAction actionWithTitle:[LocalizationHelper localizedStringForKey:@"Apply"]
+                                                                style:UIAlertActionStyleDefault
+                                                              handler:^(UIAlertAction * _Nonnull action) {
+                applyChange();
+            }]];
+
+            [alertController addAction:[UIAlertAction actionWithTitle:[LocalizationHelper localizedStringForKey:@"Learn More"]
+                                                                style:UIAlertActionStyleDefault
+                                                              handler:^(UIAlertAction * _Nonnull action) {
+                revertChange();
+                NSURL *url = [NSURL URLWithString:[LocalizationHelper localizedStringForKey:@"betterPerformanceLink"]];
+                if ([[UIApplication sharedApplication] canOpenURL:url]) {
+                    [[UIApplication sharedApplication] openURL:url options:@{} completionHandler:nil];
+                }
+            }]];
+
+            [alertController addAction:[UIAlertAction actionWithTitle:[LocalizationHelper localizedStringForKey:@"Cancel"]
+                                                                style:UIAlertActionStyleCancel
+                                                              handler:^(UIAlertAction * _Nonnull action) {
+                revertChange();
+            }]];
+
+            [self presentViewController:alertController animated:YES completion:nil];
+        } else {
+            // Switching back to the standard renderer needs no confirmation
+            applyChange();
+        }
     }
 }
 
diff --git a/VoidLink/ViewControllers/StreamFrameViewController.m b/VoidLink/ViewControllers/StreamFrameViewController.m
index f974420d..d51b0aec 100644
--- a/VoidLink/ViewControllers/StreamFrameViewController.m
+++ b/VoidLink/ViewControllers/StreamFrameViewController.m
@@ -1244,8 +1244,8 @@ static __weak StreamFrameViewController *VLSharedStreamFrameViewController = nil
 - (void)willMoveToParentViewController:(UIViewController *)parent {
     // Only cleanup when we're being destroyed
     if (parent == nil) {
-        _streamView = nil;
         [_streamView cleanUp];
+        _streamView = nil;
         [_controllerSupport cleanup];
 
         [UIApplication sharedApplication].idleTimerDisabled = NO;
@@ -1255,6 +1255,10 @@ static __weak StreamFrameViewController *VLSharedStreamFrameViewController = nil
             _inactivityTimer = nil;
         }
         if (self.metalViewController) {
+            // Explicit shutdown: viewDidDisappear is not guaranteed to fire here
+            // (e.g. teardown while backgrounded), and it's what stops the render
+            // thread, display link and renderer.
+            [self.metalViewController shutdown];
             [self.metalViewController.view removeFromSuperview];
             [self.metalViewController removeFromParentViewController];
             self.metalViewController = nil;