diff --git a/core/src/main/java/com/google/adk/agents/CallbackContext.java b/core/src/main/java/com/google/adk/agents/CallbackContext.java
index a29783769..da5b0d794 100644
--- a/core/src/main/java/com/google/adk/agents/CallbackContext.java
+++ b/core/src/main/java/com/google/adk/agents/CallbackContext.java
@@ -19,12 +19,12 @@
 import com.google.adk.artifacts.ListArtifactsResponse;
 import com.google.adk.events.EventActions;
 import com.google.adk.sessions.State;
+import com.google.common.base.Preconditions;
 import com.google.genai.types.Part;
 import io.reactivex.rxjava3.core.Completable;
 import io.reactivex.rxjava3.core.Maybe;
 import io.reactivex.rxjava3.core.Single;
 import java.util.List;
-import java.util.Optional;
 
 /** The context of various callbacks for an agent invocation. */
 public class CallbackContext extends ReadonlyContext {
@@ -94,22 +94,19 @@ public Single<List<String>> listArtifacts() {
 
   /** Loads the latest version of an artifact from the service. */
   public Maybe<Part> loadArtifact(String filename) {
-    return loadArtifact(filename, Optional.empty());
+    checkArtifactServiceInitialized();
+    return invocationContext
+        .artifactService()
+        .loadArtifact(
+            invocationContext.appName(),
+            invocationContext.userId(),
+            invocationContext.session().id(),
+            filename);
   }
 
   /** Loads a specific version of an artifact from the service. */
   public Maybe<Part> loadArtifact(String filename, int version) {
-    return loadArtifact(filename, Optional.of(version));
-  }
-
-  /**
-   * @deprecated Use {@link #loadArtifact(String)} or {@link #loadArtifact(String, int)} instead.
-   */
-  @Deprecated
-  public Maybe<Part> loadArtifact(String filename, Optional<Integer> version) {
-    if (invocationContext.artifactService() == null) {
-      throw new IllegalStateException("Artifact service is not initialized.");
-    }
+    checkArtifactServiceInitialized();
     return invocationContext
         .artifactService()
         .loadArtifact(
@@ -120,6 +117,11 @@ public Maybe<Part> loadArtifact(String filename, Optional<Integer> version) {
             version);
   }
 
+  private void checkArtifactServiceInitialized() {
+    Preconditions.checkState(
+        invocationContext.artifactService() != null, "Artifact service is not initialized.");
+  }
+
   /**
    * Saves an artifact and records it as a delta for the current session.
    *
diff --git a/core/src/main/java/com/google/adk/tools/LoadArtifactsTool.java b/core/src/main/java/com/google/adk/tools/LoadArtifactsTool.java
index c5ae8af37..399079af5 100644
--- a/core/src/main/java/com/google/adk/tools/LoadArtifactsTool.java
+++ b/core/src/main/java/com/google/adk/tools/LoadArtifactsTool.java
@@ -169,7 +169,7 @@ private Completable loadAndAppendIndividualArtifact(
       LlmRequest.Builder llmRequestBuilder, ToolContext toolContext, String artifactName) {
 
     return toolContext
-        .loadArtifact(artifactName, Optional.empty())
+        .loadArtifact(artifactName)
         .flatMapCompletable(
             actualArtifact ->
                 Completable.fromAction(
diff --git a/core/src/test/java/com/google/adk/tools/LoadArtifactsToolTest.java b/core/src/test/java/com/google/adk/tools/LoadArtifactsToolTest.java
index 89014175d..5ed7a1f40 100644
--- a/core/src/test/java/com/google/adk/tools/LoadArtifactsToolTest.java
+++ b/core/src/test/java/com/google/adk/tools/LoadArtifactsToolTest.java
@@ -3,7 +3,6 @@
 import static com.google.common.truth.Truth.assertThat;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.ArgumentMatchers.anyString;
-import static org.mockito.ArgumentMatchers.eq;
 import static org.mockito.ArgumentMatchers.nullable;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.never;
@@ -163,12 +162,11 @@ public void processLlmRequest_artifactsInContext_withLoadArtifactsFunctionCall_l
     Part loadedArtifactPart = Part.fromText("This is the content of doc1.txt");
     ToolContext spiedToolContext = spy(ToolContext.builder(mockInvocationContext).build());
     when(spiedToolContext.listArtifacts()).thenReturn(Single.just(availableArtifacts));
-    when(spiedToolContext.loadArtifact(eq("doc1.txt"), eq(Optional.empty())))
-        .thenReturn(Maybe.just(loadedArtifactPart));
+    when(spiedToolContext.loadArtifact("doc1.txt")).thenReturn(Maybe.just(loadedArtifactPart));
 
     loadArtifactsTool.processLlmRequest(llmRequestBuilder, spiedToolContext).blockingAwait();
 
-    verify(spiedToolContext).loadArtifact(eq("doc1.txt"), eq(Optional.empty()));
+    verify(spiedToolContext).loadArtifact("doc1.txt");
 
     LlmRequest finalRequest = llmRequestBuilder.build();
     List<Content> finalContents = finalRequest.contents();