diff --git a/core/src/main/java/com/google/adk/flows/llmflows/BaseLlmFlow.java b/core/src/main/java/com/google/adk/flows/llmflows/BaseLlmFlow.java
index 79066b213..ab5f6567a 100644
--- a/core/src/main/java/com/google/adk/flows/llmflows/BaseLlmFlow.java
+++ b/core/src/main/java/com/google/adk/flows/llmflows/BaseLlmFlow.java
@@ -190,20 +190,23 @@ private Flowable<LlmResponse> callLlm(
                                       context, llmRequestBuilder, eventForCallbackUsage, exception)
                                   .switchIfEmpty(Single.error(exception))
                                   .toFlowable())
-                      .doOnNext(
-                          llmResp ->
-                              Tracing.traceCallLlm(
-                                  context,
-                                  eventForCallbackUsage.id(),
-                                  llmRequestBuilder.build(),
-                                  llmResp))
                       .doOnError(
                           error -> {
                             Span span = Span.current();
                             span.setStatus(StatusCode.ERROR, error.getMessage());
                             span.recordException(error);
                           })
-                      .compose(Tracing.<LlmResponse>trace("call_llm").setParent(spanContext))
+                      .compose(
+                          Tracing.<LlmResponse>trace("call_llm")
+                              .setParent(spanContext)
+                              .onSuccess(
+                                  (span, llmResp) ->
+                                      Tracing.traceCallLlm(
+                                          span,
+                                          context,
+                                          eventForCallbackUsage.id(),
+                                          llmRequestBuilder.build(),
+                                          llmResp)))
                       .concatMap(
                           llmResp ->
                               handleAfterModelCallback(context, llmResp, eventForCallbackUsage)
diff --git a/core/src/main/java/com/google/adk/telemetry/Tracing.java b/core/src/main/java/com/google/adk/telemetry/Tracing.java
index 7f338fdcf..35bf3cc96 100644
--- a/core/src/main/java/com/google/adk/telemetry/Tracing.java
+++ b/core/src/main/java/com/google/adk/telemetry/Tracing.java
@@ -54,6 +54,7 @@
 import java.util.Map;
 import java.util.Objects;
 import java.util.Optional;
+import java.util.function.BiConsumer;
 import java.util.function.Consumer;
 import java.util.function.Supplier;
 import org.reactivestreams.Publisher;
@@ -292,58 +293,49 @@ private static Map<String, Object> buildLlmRequestForTrace(LlmRequest llmRequest
    * @param llmResponse The LLM response object.
    */
   public static void traceCallLlm(
+      Span span,
       InvocationContext invocationContext,
       String eventId,
       LlmRequest llmRequest,
       LlmResponse llmResponse) {
-    traceWithSpan(
-        "traceCallLlm",
-        span -> {
-          span.setAttribute(GEN_AI_SYSTEM, "gcp.vertex.agent");
-          llmRequest
-              .model()
-              .ifPresent(modelName -> span.setAttribute(GEN_AI_REQUEST_MODEL, modelName));
-
-          setInvocationAttributes(span, invocationContext, eventId);
-
-          setJsonAttribute(span, ADK_LLM_REQUEST, buildLlmRequestForTrace(llmRequest));
-          setJsonAttribute(span, ADK_LLM_RESPONSE, llmResponse);
-
-          llmRequest
-              .config()
-              .ifPresent(
-                  config -> {
-                    config
-                        .topP()
-                        .ifPresent(
-                            topP -> span.setAttribute(GEN_AI_REQUEST_TOP_P, topP.doubleValue()));
-                    config
-                        .maxOutputTokens()
-                        .ifPresent(
-                            maxTokens ->
-                                span.setAttribute(
-                                    GEN_AI_REQUEST_MAX_TOKENS, maxTokens.longValue()));
-                  });
-          llmResponse
-              .usageMetadata()
-              .ifPresent(
-                  usage -> {
-                    usage
-                        .promptTokenCount()
-                        .ifPresent(
-                            tokens -> span.setAttribute(GEN_AI_USAGE_INPUT_TOKENS, (long) tokens));
-                    usage
-                        .candidatesTokenCount()
-                        .ifPresent(
-                            tokens -> span.setAttribute(GEN_AI_USAGE_OUTPUT_TOKENS, (long) tokens));
-                  });
-          llmResponse
-              .finishReason()
-              .map(reason -> reason.knownEnum().name().toLowerCase(Locale.ROOT))
-              .ifPresent(
-                  reason ->
-                      span.setAttribute(GEN_AI_RESPONSE_FINISH_REASONS, ImmutableList.of(reason)));
-        });
+    span.setAttribute(GEN_AI_SYSTEM, "gcp.vertex.agent");
+    llmRequest.model().ifPresent(modelName -> span.setAttribute(GEN_AI_REQUEST_MODEL, modelName));
+
+    setInvocationAttributes(span, invocationContext, eventId);
+
+    setJsonAttribute(span, ADK_LLM_REQUEST, buildLlmRequestForTrace(llmRequest));
+    setJsonAttribute(span, ADK_LLM_RESPONSE, llmResponse);
+
+    llmRequest
+        .config()
+        .ifPresent(
+            config -> {
+              config
+                  .topP()
+                  .ifPresent(topP -> span.setAttribute(GEN_AI_REQUEST_TOP_P, topP.doubleValue()));
+              config
+                  .maxOutputTokens()
+                  .ifPresent(
+                      maxTokens ->
+                          span.setAttribute(GEN_AI_REQUEST_MAX_TOKENS, maxTokens.longValue()));
+            });
+    llmResponse
+        .usageMetadata()
+        .ifPresent(
+            usage -> {
+              usage
+                  .promptTokenCount()
+                  .ifPresent(tokens -> span.setAttribute(GEN_AI_USAGE_INPUT_TOKENS, (long) tokens));
+              usage
+                  .candidatesTokenCount()
+                  .ifPresent(
+                      tokens -> span.setAttribute(GEN_AI_USAGE_OUTPUT_TOKENS, (long) tokens));
+            });
+    llmResponse
+        .finishReason()
+        .map(reason -> reason.knownEnum().name().toLowerCase(Locale.ROOT))
+        .ifPresent(
+            reason -> span.setAttribute(GEN_AI_RESPONSE_FINISH_REASONS, ImmutableList.of(reason)));
   }
 
   /**
@@ -455,6 +447,7 @@ public static final class TracerProvider<T>
     private final String spanName;
     private Context explicitParentContext;
     private final List<Consumer<Span>> spanConfigurers = new ArrayList<>();
+    private BiConsumer<Span, T> onSuccessConsumer;
 
     private TracerProvider(String spanName) {
       this.spanName = spanName;
@@ -474,6 +467,16 @@ public TracerProvider<T> setParent(Context parentContext) {
       return this;
     }
 
+    /**
+     * Registers a callback to be executed with the span and the result item when the stream emits a
+     * success value.
+     */
+    @CanIgnoreReturnValue
+    public TracerProvider<T> onSuccess(BiConsumer<Span, T> consumer) {
+      this.onSuccessConsumer = consumer;
+      return this;
+    }
+
     private Context getParentContext() {
       return explicitParentContext != null ? explicitParentContext : Context.current();
     }
@@ -504,7 +507,11 @@ public Publisher<T> apply(Flowable<T> upstream) {
       return Flowable.defer(
           () -> {
             TracingLifecycle lifecycle = new TracingLifecycle();
-            return upstream.doOnSubscribe(s -> lifecycle.start()).doFinally(lifecycle::end);
+            Flowable<T> pipeline = upstream.doOnSubscribe(s -> lifecycle.start());
+            if (onSuccessConsumer != null) {
+              pipeline = pipeline.doOnNext(t -> onSuccessConsumer.accept(lifecycle.span, t));
+            }
+            return pipeline.doFinally(lifecycle::end);
           });
     }
 
@@ -513,7 +520,11 @@ public SingleSource<T> apply(Single<T> upstream) {
       return Single.defer(
           () -> {
             TracingLifecycle lifecycle = new TracingLifecycle();
-            return upstream.doOnSubscribe(s -> lifecycle.start()).doFinally(lifecycle::end);
+            Single<T> pipeline = upstream.doOnSubscribe(s -> lifecycle.start());
+            if (onSuccessConsumer != null) {
+              pipeline = pipeline.doOnSuccess(t -> onSuccessConsumer.accept(lifecycle.span, t));
+            }
+            return pipeline.doFinally(lifecycle::end);
           });
     }
 
@@ -522,7 +533,11 @@ public MaybeSource<T> apply(Maybe<T> upstream) {
       return Maybe.defer(
           () -> {
             TracingLifecycle lifecycle = new TracingLifecycle();
-            return upstream.doOnSubscribe(s -> lifecycle.start()).doFinally(lifecycle::end);
+            Maybe<T> pipeline = upstream.doOnSubscribe(s -> lifecycle.start());
+            if (onSuccessConsumer != null) {
+              pipeline = pipeline.doOnSuccess(t -> onSuccessConsumer.accept(lifecycle.span, t));
+            }
+            return pipeline.doFinally(lifecycle::end);
           });
     }
 
diff --git a/core/src/test/java/com/google/adk/telemetry/ContextPropagationTest.java b/core/src/test/java/com/google/adk/telemetry/ContextPropagationTest.java
index 9439fe718..f809193cf 100644
--- a/core/src/test/java/com/google/adk/telemetry/ContextPropagationTest.java
+++ b/core/src/test/java/com/google/adk/telemetry/ContextPropagationTest.java
@@ -503,7 +503,7 @@ public void testTraceCallLlm() {
                       .totalTokenCount(30)
                       .build())
               .build();
-      Tracing.traceCallLlm(buildInvocationContext(), "event-1", llmRequest, llmResponse);
+      Tracing.traceCallLlm(span, buildInvocationContext(), "event-1", llmRequest, llmResponse);
     } finally {
       span.end();
     }