diff --git a/agentscope-core/src/main/java/io/agentscope/core/tool/DefaultToolEmitter.java b/agentscope-core/src/main/java/io/agentscope/core/tool/DefaultToolEmitter.java
index d003893fc..8121a865c 100644
--- a/agentscope-core/src/main/java/io/agentscope/core/tool/DefaultToolEmitter.java
+++ b/agentscope-core/src/main/java/io/agentscope/core/tool/DefaultToolEmitter.java
@@ -22,10 +22,14 @@
 /**
  * Default implementation of ToolEmitter that delivers chunks to a callback.
  *
- * <p>This class is package-private and created internally by the framework when a tool method
- * declares a ToolEmitter parameter. Each tool invocation gets its own DefaultToolEmitter instance.
+ * <p>Created internally by the framework when a tool method declares a ToolEmitter parameter. Each
+ * tool invocation gets its own DefaultToolEmitter instance.
+ *
+ * <p>Users can cast a {@link ToolEmitter} to {@code DefaultToolEmitter} to access the underlying
+ * {@link ToolUseBlock} (e.g. to obtain the {@code toolCallId} for asynchronous session restoration
+ * after a {@link ToolSuspendException}).
  */
-class DefaultToolEmitter implements ToolEmitter {
+public class DefaultToolEmitter implements ToolEmitter {
 
     private final ToolUseBlock toolUseBlock;
     private final BiConsumer<ToolUseBlock, ToolResultBlock> chunkCallback;
@@ -36,12 +40,21 @@ class DefaultToolEmitter implements ToolEmitter {
      * @param toolUseBlock The tool use block identifying the tool call
      * @param chunkCallback Callback to deliver chunks to hooks (may be null)
      */
-    DefaultToolEmitter(
+    public DefaultToolEmitter(
             ToolUseBlock toolUseBlock, BiConsumer<ToolUseBlock, ToolResultBlock> chunkCallback) {
         this.toolUseBlock = toolUseBlock;
         this.chunkCallback = chunkCallback;
     }
 
+    /**
+     * Returns the tool use block containing the tool call ID and metadata.
+     *
+     * @return the tool use block
+     */
+    public ToolUseBlock getToolUseBlock() {
+        return toolUseBlock;
+    }
+
     /**
      * Emits a tool result chunk to the registered callback.
      *
diff --git a/agentscope-core/src/test/java/io/agentscope/core/tool/DefaultToolEmitterTest.java b/agentscope-core/src/test/java/io/agentscope/core/tool/DefaultToolEmitterTest.java
new file mode 100644
index 000000000..a229afb4c
--- /dev/null
+++ b/agentscope-core/src/test/java/io/agentscope/core/tool/DefaultToolEmitterTest.java
@@ -0,0 +1,82 @@
+/*
+ * Copyright 2024-2026 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package io.agentscope.core.tool;
+
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertSame;
+
+import io.agentscope.core.message.ToolResultBlock;
+import io.agentscope.core.message.ToolUseBlock;
+import java.util.Map;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+/** Tests for DefaultToolEmitter. */
+@DisplayName("DefaultToolEmitter Tests")
+class DefaultToolEmitterTest {
+
+    private final ToolUseBlock testToolUseBlock =
+            ToolUseBlock.builder()
+                    .id("call_test")
+                    .name("test_tool")
+                    .input(Map.of())
+                    .content("{}")
+                    .build();
+
+    @Test
+    @DisplayName("getToolUseBlock() should return the ToolUseBlock with tool call ID")
+    void testGetToolUseBlock() {
+        DefaultToolEmitter emitter = new DefaultToolEmitter(testToolUseBlock, null);
+
+        assertNotNull(emitter.getToolUseBlock());
+        assertSame(testToolUseBlock, emitter.getToolUseBlock());
+        assertEquals("call_test", emitter.getToolUseBlock().getId());
+        assertEquals("test_tool", emitter.getToolUseBlock().getName());
+    }
+
+    @Test
+    @DisplayName("emit() should not throw when callback is null")
+    void testEmitWithNullCallback() {
+        DefaultToolEmitter emitter = new DefaultToolEmitter(testToolUseBlock, null);
+        assertDoesNotThrow(() -> emitter.emit(ToolResultBlock.text("test")));
+    }
+
+    @Test
+    @DisplayName("emit() should not throw when chunk is null")
+    void testEmitWithNullChunk() {
+        DefaultToolEmitter emitter =
+                new DefaultToolEmitter(
+                        testToolUseBlock,
+                        (useBlock, chunk) -> {
+                            throw new RuntimeException("should not be called");
+                        });
+        assertDoesNotThrow(() -> emitter.emit(null));
+    }
+
+    @Test
+    @DisplayName("emit() should invoke callback with correct ToolUseBlock")
+    void testEmitWithCallback() {
+        ToolUseBlock[] captured = {null};
+        DefaultToolEmitter emitter =
+                new DefaultToolEmitter(
+                        testToolUseBlock, (useBlock, chunk) -> captured[0] = useBlock);
+
+        emitter.emit(ToolResultBlock.text("hello"));
+        assertSame(testToolUseBlock, captured[0]);
+    }
+}