feat(apple): Add docs for pre-warmed app starts

src/platform-includes/getting-started-config/apple.mdx

@@ -80,6 +80,7 @@ SentrySDK.start { options in
 
     // Enable all experimental features
     options.enableUserInteractionTracing = true
+    options.enablePreWarmedAppStartTracking = true
     options.attachScreenshot = true
     options.attachViewHierarchy = true
 }
@@ -92,6 +93,7 @@ SentrySDK.start { options in
 
     // Enable all experimental features
     options.enableUserInteractionTracing = YES;
+    options.enablePreWarmedAppStartTracking = YES;
     options.attachScreenshot = YES;
     options.attachViewHierarchy = YES;
 }];

src/platforms/apple/common/performance/instrumentation/automatic-instrumentation.mdx

@@ -55,12 +55,6 @@ This feature is available for iOS, tvOS, and Mac Catalyst.
 App Start Tracking is enabled by default once you <PlatformLink to="/performance/">set up performance monitoring</PlatformLink>. This feature provides insight into how long your application takes to launch. It adds spans for different phases, from the application launch to the first auto-generated UI transaction.
 To enable this feature, enable `AutoUIPerformanceTracking`.
 
-<Alert level="info" title="Important">
-
-Starting with iOS 15, the system might [pre-warm](https://developer.apple.com/documentation/uikit/app_and_environment/responding_to_the_launch_of_your_app/about_the_app_launch_sequence#3894431) your app by creating the process before the user opens it. In such cases, we can't reliably measure the app start, so we drop it as of [sentry-cocoa 7.18.0](https://github.com/getsentry/sentry-cocoa/releases/tag/7.18.0). We are working on a fix for this. Follow the [GitHub issue](https://github.com/getsentry/sentry-cocoa/issues/1897) for more details.
-
-</Alert>
-
 The SDK differentiates between a cold and a warm start, but doesn't track hot starts/resumes.
 
 * __Cold start__: App launched for the first time, after a reboot or update. The app is not in memory and no process exists.
@@ -75,6 +69,40 @@ The SDK uses the process start time as the beginning of the app start and the [`
 
 Cold and warm start are Mobile Vitals, which you can learn about in the [full documentation](/product/performance/mobile-vitals).
 
+### Prewarmed App Start Tracking
+
+Starting with iOS 15, the system might [prewarm](https://developer.apple.com/documentation/uikit/app_and_environment/responding_to_the_launch_of_your_app/about_the_app_launch_sequence#3894431) your app by creating the process before the user opens it. In such cases, we won’t be able to reliably measure the app start. But with [sentry-cocoa 7.31.0](https://github.com/getsentry/sentry-cocoa/releases/tag/7.31.0), we’ve introduced a `enablePreWarmedAppStartTracking` feature, (still in its experimental phase), which allows us to collect prewarmed app starts.
+
+Once enabled, the SDK will drop the first app start span if prewarming pauses. This approach will shorten the app start duration, but it will accurately represent the span of time from when a user clicks the app icon to when the app is responsive.
+With this feature, the SDK differentiates between four different app start types:
+
+* __Non-prewarmed cold start__ (See _cold start_  definition above.)
+* __Non-prewarmed warm start__ (See _warm start_  definition above.)
+* __Prewarmed cold start__
+* __Prewrmed warm start__
+
+You can filter for different app start types in Discover with `app_start_type:cold.prewarmed`, `app_start_type:warm.prewarmed`, `app_start_type:cold`, and `app_start_type:warm`.
+
+To enable pre-warmed app start tracking:
+
+```swift {tabTitle:Swift}
+import Sentry
+
+SentrySDK.start { options in
+    options.dsn = "___PUBLIC_DSN___"
+    options.enablePreWarmedAppStartTracking = true
+}
+```
+
+```objc {tabTitle:Objective-C}
+@import Sentry;
+
+[SentrySDK startWithConfigureOptions:^(SentryOptions *options) {
+    options.dsn = @"___PUBLIC_DSN___";
+    options.enablePreWarmedAppStartTracking = YES;
+}];
+```
+
 ## Slow and Frozen Frames
 
 This feature is available for iOS, tvOS, and Mac Catalyst.

src/wizard/apple/ios.md

@@ -118,6 +118,7 @@ SentrySDK.start { options in
 
     // Enable all experimental features
     options.enableUserInteractionTracing = true
+    options.enablePreWarmedAppStartTracking = true
     options.attachScreenshot = true
     options.attachViewHierarchy = true
 }