diff --git a/contributing/samples/core/input_output_schema/tests/weather_cupertino.json b/contributing/samples/core/input_output_schema/tests/weather_cupertino.json
index a036ca8f..0502c9f7 100644
--- a/contributing/samples/core/input_output_schema/tests/weather_cupertino.json
+++ b/contributing/samples/core/input_output_schema/tests/weather_cupertino.json
@@ -42,7 +42,7 @@
     },
     {
       "author": "weather_agent",
-      "branch": "weather_agent@1",
+      "branch": "weather_agent@fc-1",
       "content": {
         "parts": [
           {
diff --git a/contributing/samples/core/input_output_schema/tests/weather_sanjose.json b/contributing/samples/core/input_output_schema/tests/weather_sanjose.json
index 8b76e47a..9888e02b 100644
--- a/contributing/samples/core/input_output_schema/tests/weather_sanjose.json
+++ b/contributing/samples/core/input_output_schema/tests/weather_sanjose.json
@@ -42,7 +42,7 @@
     },
     {
       "author": "weather_agent",
-      "branch": "weather_agent@1",
+      "branch": "weather_agent@fc-1",
       "content": {
         "parts": [
           {
diff --git a/contributing/samples/core/input_output_schema/tests/weather_tokyo.json b/contributing/samples/core/input_output_schema/tests/weather_tokyo.json
index e531c244..1b06901a 100644
--- a/contributing/samples/core/input_output_schema/tests/weather_tokyo.json
+++ b/contributing/samples/core/input_output_schema/tests/weather_tokyo.json
@@ -42,7 +42,7 @@
     },
     {
       "author": "weather_agent",
-      "branch": "weather_agent@1",
+      "branch": "weather_agent@fc-1",
       "content": {
         "parts": [
           {
diff --git a/contributing/samples/multi_agent/single_turn_sub_agent/tests/gaming_1000.json b/contributing/samples/multi_agent/single_turn_sub_agent/tests/gaming_1000.json
index 9112d546..c442c759 100644
--- a/contributing/samples/multi_agent/single_turn_sub_agent/tests/gaming_1000.json
+++ b/contributing/samples/multi_agent/single_turn_sub_agent/tests/gaming_1000.json
@@ -77,7 +77,7 @@
     },
     {
       "author": "phone_recommender",
-      "branch": "phone_recommender@1",
+      "branch": "phone_recommender@fc-1",
       "content": {
         "parts": [
           {
@@ -102,7 +102,7 @@
     },
     {
       "author": "phone_recommender",
-      "branch": "phone_recommender@1",
+      "branch": "phone_recommender@fc-1",
       "content": {
         "parts": [
           {
@@ -125,7 +125,7 @@
     },
     {
       "author": "phone_recommender",
-      "branch": "phone_recommender@1",
+      "branch": "phone_recommender@fc-1",
       "content": {
         "parts": [
           {
@@ -150,7 +150,7 @@
     },
     {
       "author": "phone_recommender",
-      "branch": "phone_recommender@1",
+      "branch": "phone_recommender@fc-1",
       "content": {
         "parts": [
           {
@@ -173,7 +173,7 @@
     },
     {
       "author": "phone_recommender",
-      "branch": "phone_recommender@1",
+      "branch": "phone_recommender@fc-1",
       "content": {
         "parts": [
           {
@@ -198,7 +198,7 @@
     },
     {
       "author": "phone_recommender",
-      "branch": "phone_recommender@1",
+      "branch": "phone_recommender@fc-1",
       "content": {
         "parts": [
           {
@@ -221,7 +221,7 @@
     },
     {
       "author": "phone_recommender",
-      "branch": "phone_recommender@1",
+      "branch": "phone_recommender@fc-1",
       "content": {
         "parts": [
           {
@@ -246,7 +246,7 @@
     },
     {
       "author": "phone_recommender",
-      "branch": "phone_recommender@1",
+      "branch": "phone_recommender@fc-1",
       "content": {
         "parts": [
           {
@@ -269,7 +269,7 @@
     },
     {
       "author": "phone_recommender",
-      "branch": "phone_recommender@1",
+      "branch": "phone_recommender@fc-1",
       "content": {
         "parts": [
           {
@@ -294,7 +294,7 @@
     },
     {
       "author": "phone_recommender",
-      "branch": "phone_recommender@1",
+      "branch": "phone_recommender@fc-1",
       "content": {
         "parts": [
           {
@@ -317,7 +317,7 @@
     },
     {
       "author": "phone_recommender",
-      "branch": "phone_recommender@1",
+      "branch": "phone_recommender@fc-1",
       "content": {
         "parts": [
           {
@@ -351,7 +351,7 @@
         }
       },
       "author": "phone_recommender",
-      "branch": "phone_recommender@1",
+      "branch": "phone_recommender@fc-1",
       "content": {
         "parts": [
           {
@@ -376,7 +376,7 @@
     },
     {
       "author": "phone_recommender",
-      "branch": "phone_recommender@1",
+      "branch": "phone_recommender@fc-1",
       "content": {
         "parts": [
           {
diff --git a/contributing/samples/multi_agent/single_turn_sub_agent/tests/gaming_1000_large.json b/contributing/samples/multi_agent/single_turn_sub_agent/tests/gaming_1000_large.json
index 93be74f9..9904bb65 100644
--- a/contributing/samples/multi_agent/single_turn_sub_agent/tests/gaming_1000_large.json
+++ b/contributing/samples/multi_agent/single_turn_sub_agent/tests/gaming_1000_large.json
@@ -44,7 +44,7 @@
     },
     {
       "author": "phone_recommender",
-      "branch": "phone_recommender@1",
+      "branch": "phone_recommender@fc-1",
       "content": {
         "parts": [
           {
@@ -69,7 +69,7 @@
     },
     {
       "author": "phone_recommender",
-      "branch": "phone_recommender@1",
+      "branch": "phone_recommender@fc-1",
       "content": {
         "parts": [
           {
@@ -92,7 +92,7 @@
     },
     {
       "author": "phone_recommender",
-      "branch": "phone_recommender@1",
+      "branch": "phone_recommender@fc-1",
       "content": {
         "parts": [
           {
@@ -117,7 +117,7 @@
     },
     {
       "author": "phone_recommender",
-      "branch": "phone_recommender@1",
+      "branch": "phone_recommender@fc-1",
       "content": {
         "parts": [
           {
@@ -140,7 +140,7 @@
     },
     {
       "author": "phone_recommender",
-      "branch": "phone_recommender@1",
+      "branch": "phone_recommender@fc-1",
       "content": {
         "parts": [
           {
@@ -165,7 +165,7 @@
     },
     {
       "author": "phone_recommender",
-      "branch": "phone_recommender@1",
+      "branch": "phone_recommender@fc-1",
       "content": {
         "parts": [
           {
@@ -188,7 +188,7 @@
     },
     {
       "author": "phone_recommender",
-      "branch": "phone_recommender@1",
+      "branch": "phone_recommender@fc-1",
       "content": {
         "parts": [
           {
@@ -213,7 +213,7 @@
     },
     {
       "author": "phone_recommender",
-      "branch": "phone_recommender@1",
+      "branch": "phone_recommender@fc-1",
       "content": {
         "parts": [
           {
@@ -236,7 +236,7 @@
     },
     {
       "author": "phone_recommender",
-      "branch": "phone_recommender@1",
+      "branch": "phone_recommender@fc-1",
       "content": {
         "parts": [
           {
@@ -270,7 +270,7 @@
         }
       },
       "author": "phone_recommender",
-      "branch": "phone_recommender@1",
+      "branch": "phone_recommender@fc-1",
       "content": {
         "parts": [
           {
@@ -295,7 +295,7 @@
     },
     {
       "author": "phone_recommender",
-      "branch": "phone_recommender@1",
+      "branch": "phone_recommender@fc-1",
       "content": {
         "parts": [
           {
diff --git a/contributing/samples/multi_agent/single_turn_sub_agent/tests/go.json b/contributing/samples/multi_agent/single_turn_sub_agent/tests/go.json
index 8eea2f7d..1c69be34 100644
--- a/contributing/samples/multi_agent/single_turn_sub_agent/tests/go.json
+++ b/contributing/samples/multi_agent/single_turn_sub_agent/tests/go.json
@@ -110,7 +110,7 @@
     },
     {
       "author": "phone_recommender",
-      "branch": "phone_recommender@1",
+      "branch": "phone_recommender@fc-1",
       "content": {
         "parts": [
           {
@@ -144,7 +144,7 @@
     },
     {
       "author": "phone_recommender",
-      "branch": "phone_recommender@1",
+      "branch": "phone_recommender@fc-1",
       "content": {
         "parts": [
           {
@@ -176,7 +176,7 @@
     },
     {
       "author": "phone_recommender",
-      "branch": "phone_recommender@1",
+      "branch": "phone_recommender@fc-1",
       "content": {
         "parts": [
           {
@@ -219,7 +219,7 @@
     },
     {
       "author": "phone_recommender",
-      "branch": "phone_recommender@1",
+      "branch": "phone_recommender@fc-1",
       "content": {
         "parts": [
           {
@@ -260,7 +260,7 @@
     },
     {
       "author": "phone_recommender",
-      "branch": "phone_recommender@1",
+      "branch": "phone_recommender@fc-1",
       "content": {
         "parts": [
           {
@@ -294,7 +294,7 @@
         }
       },
       "author": "phone_recommender",
-      "branch": "phone_recommender@1",
+      "branch": "phone_recommender@fc-1",
       "content": {
         "parts": [
           {
@@ -319,7 +319,7 @@
     },
     {
       "author": "phone_recommender",
-      "branch": "phone_recommender@1",
+      "branch": "phone_recommender@fc-1",
       "content": {
         "parts": [
           {
diff --git a/src/google/adk/tools/agent_tool.py b/src/google/adk/tools/agent_tool.py
index 8054d0ff..55fe7ff6 100644
--- a/src/google/adk/tools/agent_tool.py
+++ b/src/google/adk/tools/agent_tool.py
@@ -361,9 +361,18 @@ class _SingleTurnAgentTool(AgentTool):
     else:
       node_input = args.get('request')
 
+    # Align subagent branch scoping with node execution (Node as Tool) using function_call_id.
+    fc_id = tool_context.function_call_id
+    base_branch = tool_context.get_invocation_context().branch
+    segment = f'{self.agent.name}@{fc_id}'
+    tool_branch = f'{base_branch}.{segment}' if base_branch else segment
+
     try:
       return await tool_context.run_node(
-          self.agent, node_input=node_input, use_sub_branch=True
+          self.agent,
+          node_input=node_input,
+          override_branch=tool_branch,
+          use_sub_branch=False,
       )
     except Exception as e:
       return f'Error running sub-agent: {e}'