diff --git a/core/src/main/java/com/google/adk/agents/LlmAgent.java b/core/src/main/java/com/google/adk/agents/LlmAgent.java
index e03c0d25..2528f7d5 100644
--- a/core/src/main/java/com/google/adk/agents/LlmAgent.java
+++ b/core/src/main/java/com/google/adk/agents/LlmAgent.java
@@ -875,8 +875,8 @@ private Model resolveModelInternal() {
     }
     BaseAgent current = this.parentAgent();
     while (current != null) {
-      if (current instanceof LlmAgent) {
-        return ((LlmAgent) current).resolvedModel();
+      if (current instanceof LlmAgent agent) {
+        return agent.resolvedModel();
       }
       current = current.parentAgent();
     }
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 34114d00..64d602ca 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
@@ -208,10 +208,7 @@ private Flowable<LlmResponse> callLlm(
               if (beforeResponse.isPresent()) {
                 return Flowable.just(beforeResponse.get());
               }
-              BaseLlm llm =
-                  agent.resolvedModel().model().isPresent()
-                      ? agent.resolvedModel().model().get()
-                      : LlmRegistry.getLlm(agent.resolvedModel().modelName().get());
+              BaseLlm llm = agent.resolvedModel().model().get();
               return Flowable.defer(
                       () -> {
                         Span llmCallSpan =
@@ -464,10 +461,7 @@ public Flowable<Event> runLive(InvocationContext invocationContext) {
 
               String eventIdForSendData = Event.generateEventId();
               LlmAgent agent = (LlmAgent) invocationContext.agent();
-              BaseLlm llm =
-                  agent.resolvedModel().model().isPresent()
-                      ? agent.resolvedModel().model().get()
-                      : LlmRegistry.getLlm(agent.resolvedModel().modelName().get());
+              BaseLlm llm = agent.resolvedModel().model().get();
               BaseLlmConnection connection = llm.connect(llmRequestAfterPreprocess);
               Completable historySent =
                   llmRequestAfterPreprocess.contents().isEmpty()
diff --git a/core/src/main/java/com/google/adk/flows/llmflows/Basic.java b/core/src/main/java/com/google/adk/flows/llmflows/Basic.java
index fa447625..4ef08a17 100644
--- a/core/src/main/java/com/google/adk/flows/llmflows/Basic.java
+++ b/core/src/main/java/com/google/adk/flows/llmflows/Basic.java
@@ -33,14 +33,10 @@ public Basic() {}
   @Override
   public Single<RequestProcessor.RequestProcessingResult> processRequest(
       InvocationContext context, LlmRequest request) {
-    if (!(context.agent() instanceof LlmAgent)) {
+    if (!(context.agent() instanceof LlmAgent agent)) {
       throw new IllegalArgumentException("Agent in InvocationContext is not an instance of Agent.");
     }
-    LlmAgent agent = (LlmAgent) context.agent();
-    String modelName =
-        agent.resolvedModel().model().isPresent()
-            ? agent.resolvedModel().model().get().model()
-            : agent.resolvedModel().modelName().get();
+    String modelName = agent.resolvedModel().modelName().get();
 
     LiveConnectConfig.Builder liveConnectConfigBuilder =
         LiveConnectConfig.builder().responseModalities(context.runConfig().responseModalities());