Merge pull request #3104 from DataDog/marroz/RUM-17867-fix-onSessionStart-call-order

RUM-17867: Fixes wrong order setting up session sampler and calling `onSessionStart`.

Author: arroz

CHANGELOG.md

@@ -1,6 +1,7 @@
 # Unreleased
 
 - [FEATURE] Add support for UK1 Datadog Site. See [#3087][]
+- [FIX] onSessionStart is now called only after sampling information used by WebView Tracking is in place, avoiding missing traces in early requests. See [#3104][]
 
 # 3.14.0 / 15-07-2026
 
@@ -1200,6 +1201,7 @@ Release `2.0` introduces breaking changes. Follow the [Migration Guide](MIGRATIO
 [#3019]: https://github.com/DataDog/dd-sdk-ios/pull/3019
 [#3051]: https://github.com/DataDog/dd-sdk-ios/pull/3051
 [#3087]: https://github.com/DataDog/dd-sdk-ios/pull/3087
+[#3104]: https://github.com/DataDog/dd-sdk-ios/pull/3104
 
 [@00fa9a]: https://github.com/00FA9A
 [@britton-earnin]: https://github.com/Britton-Earnin

DatadogRUM/Sources/Feature/RUMFeature.swift

@@ -111,12 +111,12 @@ internal final class RUMFeature: DatadogRemoteFeature, RUMSessionSamplerProvider
         }()
 
         let onSessionUpdate: RUM.SessionUpdater = { [onSessionStart = configuration.onSessionStart, _rumSessionSampler] sessionScope in
+            _rumSessionSampler.mutate { $0 = sessionScope?.sampler }
             if let sessionScope {
                 let sessionID = sessionScope.sessionUUID.toRUMDataFormat
                 let isDiscarded = !sessionScope.sampler.isSampled
                 onSessionStart?(sessionID, isDiscarded)
             }
-            _rumSessionSampler.mutate { $0 = sessionScope?.sampler }
         }
 
         let dependencies = RUMScopeDependencies(