fix(core): Inject replayId into trace context for buffer mode errors

CHANGELOG.md

@@ -31,6 +31,7 @@
 ### Fixes
 
 - Session Replay: Fix first recording segment missing for replays in `buffer` mode ([#5753](https://github.com/getsentry/sentry-java/pull/5753))
+- Fix error-to-replay linkage in buffer mode ([#5754](https://github.com/getsentry/sentry-java/pull/5754))
 - Fix main thread identification for tombstone (native crash) events ([#5742](https://github.com/getsentry/sentry-java/pull/5742))
 
 ### Dependencies

sentry/api/sentry.api

@@ -37,6 +37,7 @@ public final class io/sentry/Baggage {
 	public fun <init> (Lio/sentry/Baggage;)V
 	public fun <init> (Lio/sentry/ILogger;)V
 	public fun <init> (Ljava/util/concurrent/ConcurrentHashMap;Ljava/lang/Double;Ljava/lang/Double;Ljava/lang/String;ZZLio/sentry/ILogger;)V
+	public fun forceSetReplayId (Lio/sentry/protocol/SentryId;)V
 	public fun forceSetSampleRate (Ljava/lang/Double;)V
 	public fun freeze ()V
 	public static fun fromEvent (Lio/sentry/SentryBaseEvent;Ljava/lang/String;Lio/sentry/SentryOptions;)Lio/sentry/Baggage;

sentry/src/main/java/io/sentry/Baggage.java

@@ -451,6 +451,19 @@ public void setReplayId(final @Nullable String replayId) {
     set(DSCKeys.REPLAY_ID, replayId);
   }
 
+  /**
+   * Sets replay_id on the baggage bypassing the freeze check. In buffer mode the replay_id is
+   * unknown when the baggage is frozen, so it must be injected after {@link
+   * ReplayController#captureReplay} sets it on scope. This mirrors the JS SDK's <a
+   * href="https://github.com/getsentry/sentry-javascript/blob/develop/packages/replay-internal/src/util/resetReplayIdOnDynamicSamplingContext.ts">setReplayIdOnDynamicSamplingContext</a>.
+   */
+  @ApiStatus.Internal
+  public void forceSetReplayId(final @NotNull SentryId replayId) {
+    if (!SentryId.EMPTY_ID.equals(replayId)) {
+      keyValues.put(DSCKeys.REPLAY_ID, replayId.toString());
+    }
+  }
+
   @ApiStatus.Internal
   public @Nullable String getOrgId() {
     return get(DSCKeys.ORG_ID);

sentry/src/main/java/io/sentry/SentryClient.java

@@ -250,6 +250,18 @@ private boolean shouldApplyScopeData(final @NotNull CheckIn event, final @NotNul
       }
       if (shouldCaptureReplay) {
         options.getReplayController().captureReplay(event.isCrashed());
+        if (scope != null) {
+          final @Nullable SentryId replayId = scope.getReplayId();
+          if (replayId != null && !replayId.equals(SentryId.EMPTY_ID)) {
+            final @Nullable ITransaction transaction = scope.getTransaction();
+            if (transaction != null) {
+              final @Nullable Baggage baggage = transaction.getSpanContext().getBaggage();
+              if (baggage != null) {
+                baggage.forceSetReplayId(replayId);
+              }
+            }
+          }
+        }
       }
     }