prebuilts hitl: fix branching logic + add structural snapshot tests (#4767)

libs/langgraph/uv.lock

@@ -1,4 +1,5 @@
 version = 1
+revision = 1
 requires-python = ">=3.9"
 resolution-markers = [
     "python_full_version >= '3.13' and python_full_version < '4.0'",
@@ -1441,6 +1442,7 @@ dev = [
     { name = "pytest-mock" },
     { name = "pytest-watcher" },
     { name = "ruff" },
+    { name = "syrupy" },
 ]
 
 [[package]]

libs/prebuilt/langgraph/prebuilt/chat_agent_executor.py

@@ -670,13 +670,16 @@ def create_react_agent(
     # This means that this node is the first one called
     workflow.set_entry_point(entrypoint)
 
-    agent_paths = ["tools", END]
-    post_model_hook_paths = [entrypoint, "tools", END]
+    agent_paths = []
+    post_model_hook_paths = [entrypoint, "tools"]
 
     # Add a post model hook node if post_model_hook is provided
     if post_model_hook is not None:
         workflow.add_node("post_model_hook", post_model_hook)
         agent_paths.append("post_model_hook")
+        workflow.add_edge("agent", "post_model_hook")
+    else:
+        agent_paths.append("tools")
 
     # Add a structured output node if response_format is provided
     if response_format is not None:
@@ -690,6 +693,11 @@ def create_react_agent(
             post_model_hook_paths.append("generate_structured_response")
         else:
             agent_paths.append("generate_structured_response")
+    else:
+        if post_model_hook is not None:
+            post_model_hook_paths.append(END)
+        else:
+            agent_paths.append(END)
 
     if post_model_hook is not None:
 

libs/prebuilt/pyproject.toml

@@ -32,6 +32,7 @@ dev = [
     "langgraph-checkpoint",
     "langgraph-checkpoint-sqlite",
     "langgraph-checkpoint-postgres",
+    "syrupy",
 ]
 
 [tool.uv]

libs/prebuilt/tests/__snapshots__/test_react_agent_graph.ambr

@@ -0,0 +1,173 @@
+# serializer version: 1
+# name: test_react_agent_graph_structure[None-None-None-tools0]
+  '''
+  graph TD;
+  	__start__ --> agent;
+  	agent --> __end__;
+  
+  '''
+# ---
+# name: test_react_agent_graph_structure[None-None-None-tools1]
+  '''
+  graph TD;
+  	__start__ --> agent;
+  	agent -.-> __end__;
+  	agent -.-> tools;
+  	tools --> agent;
+  
+  '''
+# ---
+# name: test_react_agent_graph_structure[None-None-pre_model_hook-tools0]
+  '''
+  graph TD;
+  	__start__ --> pre_model_hook;
+  	pre_model_hook --> agent;
+  	agent --> __end__;
+  
+  '''
+# ---
+# name: test_react_agent_graph_structure[None-None-pre_model_hook-tools1]
+  '''
+  graph TD;
+  	__start__ --> pre_model_hook;
+  	agent -.-> __end__;
+  	agent -.-> tools;
+  	pre_model_hook --> agent;
+  	tools --> pre_model_hook;
+  
+  '''
+# ---
+# name: test_react_agent_graph_structure[None-post_model_hook-None-tools0]
+  '''
+  graph TD;
+  	__start__ --> agent;
+  	agent --> post_model_hook;
+  	post_model_hook --> __end__;
+  
+  '''
+# ---
+# name: test_react_agent_graph_structure[None-post_model_hook-None-tools1]
+  '''
+  graph TD;
+  	__start__ --> agent;
+  	agent --> post_model_hook;
+  	post_model_hook -.-> __end__;
+  	post_model_hook -.-> agent;
+  	post_model_hook -.-> tools;
+  	tools --> agent;
+  
+  '''
+# ---
+# name: test_react_agent_graph_structure[None-post_model_hook-pre_model_hook-tools0]
+  '''
+  graph TD;
+  	__start__ --> pre_model_hook;
+  	agent --> post_model_hook;
+  	pre_model_hook --> agent;
+  	post_model_hook --> __end__;
+  
+  '''
+# ---
+# name: test_react_agent_graph_structure[None-post_model_hook-pre_model_hook-tools1]
+  '''
+  graph TD;
+  	__start__ --> pre_model_hook;
+  	agent --> post_model_hook;
+  	post_model_hook -.-> __end__;
+  	post_model_hook -.-> pre_model_hook;
+  	post_model_hook -.-> tools;
+  	pre_model_hook --> agent;
+  	tools --> pre_model_hook;
+  
+  '''
+# ---
+# name: test_react_agent_graph_structure[ResponseFormat-None-None-tools0]
+  '''
+  graph TD;
+  	__start__ --> agent;
+  	agent --> generate_structured_response;
+  	generate_structured_response --> __end__;
+  
+  '''
+# ---
+# name: test_react_agent_graph_structure[ResponseFormat-None-None-tools1]
+  '''
+  graph TD;
+  	__start__ --> agent;
+  	agent -.-> generate_structured_response;
+  	agent -.-> tools;
+  	tools --> agent;
+  	generate_structured_response --> __end__;
+  
+  '''
+# ---
+# name: test_react_agent_graph_structure[ResponseFormat-None-pre_model_hook-tools0]
+  '''
+  graph TD;
+  	__start__ --> pre_model_hook;
+  	agent --> generate_structured_response;
+  	pre_model_hook --> agent;
+  	generate_structured_response --> __end__;
+  
+  '''
+# ---
+# name: test_react_agent_graph_structure[ResponseFormat-None-pre_model_hook-tools1]
+  '''
+  graph TD;
+  	__start__ --> pre_model_hook;
+  	agent -.-> generate_structured_response;
+  	agent -.-> tools;
+  	pre_model_hook --> agent;
+  	tools --> pre_model_hook;
+  	generate_structured_response --> __end__;
+  
+  '''
+# ---
+# name: test_react_agent_graph_structure[ResponseFormat-post_model_hook-None-tools0]
+  '''
+  graph TD;
+  	__start__ --> agent;
+  	agent --> post_model_hook;
+  	post_model_hook --> generate_structured_response;
+  	generate_structured_response --> __end__;
+  
+  '''
+# ---
+# name: test_react_agent_graph_structure[ResponseFormat-post_model_hook-None-tools1]
+  '''
+  graph TD;
+  	__start__ --> agent;
+  	agent --> post_model_hook;
+  	post_model_hook -.-> agent;
+  	post_model_hook -.-> generate_structured_response;
+  	post_model_hook -.-> tools;
+  	tools --> agent;
+  	generate_structured_response --> __end__;
+  
+  '''
+# ---
+# name: test_react_agent_graph_structure[ResponseFormat-post_model_hook-pre_model_hook-tools0]
+  '''
+  graph TD;
+  	__start__ --> pre_model_hook;
+  	agent --> post_model_hook;
+  	post_model_hook --> generate_structured_response;
+  	pre_model_hook --> agent;
+  	generate_structured_response --> __end__;
+  
+  '''
+# ---
+# name: test_react_agent_graph_structure[ResponseFormat-post_model_hook-pre_model_hook-tools1]
+  '''
+  graph TD;
+  	__start__ --> pre_model_hook;
+  	agent --> post_model_hook;
+  	post_model_hook -.-> generate_structured_response;
+  	post_model_hook -.-> pre_model_hook;
+  	post_model_hook -.-> tools;
+  	pre_model_hook --> agent;
+  	tools --> pre_model_hook;
+  	generate_structured_response --> __end__;
+  
+  '''
+# ---

libs/prebuilt/tests/test_react_agent_graph.py

@@ -0,0 +1,52 @@
+from typing import Callable, Union
+
+import pytest
+from pydantic import BaseModel
+from syrupy import SnapshotAssertion
+
+from langgraph.prebuilt import create_react_agent
+from tests.model import FakeToolCallingModel
+
+model = FakeToolCallingModel()
+
+
+def tool() -> None:
+    """Testing tool."""
+    ...
+
+
+def pre_model_hook() -> None:
+    """Pre-model hook."""
+    ...
+
+
+def post_model_hook() -> None:
+    """Post-model hook."""
+    ...
+
+
+class ResponseFormat(BaseModel):
+    """Response format for the agent."""
+
+    result: str
+
+
+@pytest.mark.parametrize("tools", [[], [tool]])
+@pytest.mark.parametrize("pre_model_hook", [None, pre_model_hook])
+@pytest.mark.parametrize("post_model_hook", [None, post_model_hook])
+@pytest.mark.parametrize("response_format", [None, ResponseFormat])
+def test_react_agent_graph_structure(
+    snapshot: SnapshotAssertion,
+    tools: list[Callable],
+    pre_model_hook: Union[Callable, None],
+    post_model_hook: Union[Callable, None],
+    response_format: Union[type[BaseModel], None],
+) -> None:
+    agent = create_react_agent(
+        model,
+        tools=tools,
+        pre_model_hook=pre_model_hook,
+        post_model_hook=post_model_hook,
+        response_format=response_format,
+    )
+    assert agent.get_graph().draw_mermaid(with_styles=False) == snapshot

libs/prebuilt/uv.lock

@@ -1,4 +1,5 @@
 version = 1
+revision = 1
 requires-python = ">=3.9"
 resolution-markers = [
     "python_full_version >= '3.12.4'",
@@ -480,6 +481,7 @@ dev = [
     { name = "pytest-mock" },
     { name = "pytest-watcher" },
     { name = "ruff" },
+    { name = "syrupy" },
 ]
 
 [package.metadata]
@@ -501,6 +503,7 @@ dev = [
     { name = "pytest-mock" },
     { name = "pytest-watcher" },
     { name = "ruff" },
+    { name = "syrupy" },
 ]
 
 [[package]]
@@ -1084,6 +1087,18 @@ wheels = [
     { url = "https://files.pythonhosted.org/packages/6a/98/e8bc58b178266eae2fcf4c9c7a8303a8d41164d781b32d71097924a6bebe/sqlite_vec-0.1.6-py3-none-win_amd64.whl", hash = "sha256:c65bcfd90fa2f41f9000052bcb8bb75d38240b2dae49225389eca6c3136d3f0c", size = 281540 },
 ]
 
+[[package]]
+name = "syrupy"
+version = "4.9.1"
+source = { registry = "https://pypi.org/simple" }
+dependencies = [
+    { name = "pytest" },
+]
+sdist = { url = "https://files.pythonhosted.org/packages/8c/f8/022d8704a3314f3e96dbd6bbd16ebe119ce30e35f41aabfa92345652fceb/syrupy-4.9.1.tar.gz", hash = "sha256:b7d0fcadad80a7d2f6c4c71917918e8ebe2483e8c703dfc8d49cdbb01081f9a4", size = 52492 }
+wheels = [
+    { url = "https://files.pythonhosted.org/packages/ec/9d/aef9ec5fd5a4ee2f6a96032c4eda5888c5c7cec65cef6b28c4fc37671d88/syrupy-4.9.1-py3-none-any.whl", hash = "sha256:b94cc12ed0e5e75b448255430af642516842a2374a46936dd2650cfb6dd20eda", size = 52214 },
+]
+
 [[package]]
 name = "tenacity"
 version = "9.1.2"

libs/scheduler-kafka/uv.lock

@@ -584,6 +584,7 @@ dev = [
     { name = "pytest-mock" },
     { name = "pytest-watcher" },
     { name = "ruff" },
+    { name = "syrupy" },
 ]
 
 [[package]]