diff --git a/adk/common/prints/util.go b/adk/common/prints/util.go
index adcd564c..f7c60188 100644
--- a/adk/common/prints/util.go
+++ b/adk/common/prints/util.go
@@ -24,8 +24,6 @@ import (
 
 	"github.com/cloudwego/eino/adk"
 	"github.com/cloudwego/eino/schema"
-
-	"github.com/cloudwego/eino-examples/internal/logs"
 )
 
 func Event(event *adk.AgentEvent) {
@@ -46,7 +44,7 @@ func Event(event *adk.AgentEvent) {
 				}
 			}
 		} else if s := event.Output.MessageOutput.MessageStream; s != nil {
-			toolMap := map[int][]*schema.Message{}
+			var toolMessages []*schema.Message
 			var contentStart bool
 			charNumOfOneRow := 0
 			maxCharNumOfOneRow := 120
@@ -81,11 +79,7 @@ func Event(event *adk.AgentEvent) {
 
 				if len(chunk.ToolCalls) > 0 {
 					for _, tc := range chunk.ToolCalls {
-						index := tc.Index
-						if index == nil {
-							logs.Fatalf("index is nil")
-						}
-						toolMap[*index] = append(toolMap[*index], &schema.Message{
+						toolMessages = append(toolMessages, &schema.Message{
 							Role: chunk.Role,
 							ToolCalls: []schema.ToolCall{
 								{
@@ -103,14 +97,16 @@ func Event(event *adk.AgentEvent) {
 				}
 			}
 
-			for _, msgs := range toolMap {
-				m, err := schema.ConcatMessages(msgs)
+			if len(toolMessages) > 0 {
+				m, err := schema.ConcatMessages(toolMessages)
 				if err != nil {
 					log.Fatalf("ConcatMessage failed: %v", err)
 					return
 				}
-				fmt.Printf("\ntool name: %s", m.ToolCalls[0].Function.Name)
-				fmt.Printf("\narguments: %s", m.ToolCalls[0].Function.Arguments)
+				for _, tc := range m.ToolCalls {
+					fmt.Printf("\ntool name: %s", tc.Function.Name)
+					fmt.Printf("\narguments: %s", tc.Function.Arguments)
+				}
 			}
 		}
 	}
diff --git a/adk/common/prints/util_test.go b/adk/common/prints/util_test.go
new file mode 100644
index 00000000..fe276863
--- /dev/null
+++ b/adk/common/prints/util_test.go
@@ -0,0 +1,137 @@
+/*
+ * Copyright 2025 CloudWeGo 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 prints
+
+import (
+	"io"
+	"os"
+	"os/exec"
+	"strings"
+	"testing"
+
+	"github.com/cloudwego/eino/adk"
+	"github.com/cloudwego/eino/schema"
+)
+
+func TestEventHandlesStreamingToolCallWithoutIndex(t *testing.T) {
+	if os.Getenv("EINO_PRINTS_NIL_INDEX_SUBPROCESS") == "1" {
+		Event(eventWithNilIndexToolCallStream())
+		return
+	}
+
+	cmd := exec.Command(os.Args[0], "-test.run=TestEventHandlesStreamingToolCallWithoutIndex")
+	cmd.Env = append(os.Environ(), "EINO_PRINTS_NIL_INDEX_SUBPROCESS=1")
+
+	output, err := cmd.CombinedOutput()
+	if err != nil {
+		t.Fatalf("Event should not exit when a streaming tool call has nil index, err=%v, output=%s", err, output)
+	}
+	if !strings.Contains(string(output), "tool name: lookup_contract") {
+		t.Fatalf("Event should print the streaming tool call name, output=%s", output)
+	}
+	if !strings.Contains(string(output), `arguments: {"supplier":"acme"}`) {
+		t.Fatalf("Event should print the streaming tool call arguments, output=%s", output)
+	}
+}
+
+func TestEventPrintsMultipleStreamingToolCallsWithoutIndex(t *testing.T) {
+	output := captureStdout(t, func() {
+		Event(eventWithMultipleNilIndexToolCallStream())
+	})
+
+	if !strings.Contains(output, "tool name: lookup_contract") {
+		t.Fatalf("Event should print the first streaming tool call name, output=%s", output)
+	}
+	if !strings.Contains(output, `arguments: {"supplier":"acme"}`) {
+		t.Fatalf("Event should print the first streaming tool call arguments, output=%s", output)
+	}
+	if !strings.Contains(output, "tool name: notify_owner") {
+		t.Fatalf("Event should print the second streaming tool call name, output=%s", output)
+	}
+	if !strings.Contains(output, `arguments: {"owner":"legal"}`) {
+		t.Fatalf("Event should print the second streaming tool call arguments, output=%s", output)
+	}
+}
+
+func eventWithNilIndexToolCallStream() *adk.AgentEvent {
+	chunk := schema.AssistantMessage("", []schema.ToolCall{
+		{
+			ID: "call_1",
+			Function: schema.FunctionCall{
+				Name:      "lookup_contract",
+				Arguments: `{"supplier":"acme"}`,
+			},
+		},
+	})
+
+	return adk.EventFromMessage(
+		nil,
+		schema.StreamReaderFromArray([]*schema.Message{chunk}),
+		schema.Assistant,
+		"",
+	)
+}
+
+func eventWithMultipleNilIndexToolCallStream() *adk.AgentEvent {
+	chunk := schema.AssistantMessage("", []schema.ToolCall{
+		{
+			ID: "call_1",
+			Function: schema.FunctionCall{
+				Name:      "lookup_contract",
+				Arguments: `{"supplier":"acme"}`,
+			},
+		},
+		{
+			ID: "call_2",
+			Function: schema.FunctionCall{
+				Name:      "notify_owner",
+				Arguments: `{"owner":"legal"}`,
+			},
+		},
+	})
+
+	return adk.EventFromMessage(
+		nil,
+		schema.StreamReaderFromArray([]*schema.Message{chunk}),
+		schema.Assistant,
+		"",
+	)
+}
+
+func captureStdout(t *testing.T, fn func()) string {
+	t.Helper()
+
+	originalStdout := os.Stdout
+	r, w, err := os.Pipe()
+	if err != nil {
+		t.Fatalf("create stdout pipe failed: %v", err)
+	}
+	os.Stdout = w
+
+	fn()
+
+	if err := w.Close(); err != nil {
+		t.Fatalf("close stdout pipe writer failed: %v", err)
+	}
+	os.Stdout = originalStdout
+
+	output, err := io.ReadAll(r)
+	if err != nil {
+		t.Fatalf("read stdout pipe failed: %v", err)
+	}
+	return string(output)
+}