fix(langgraph): restore currency agent sample (Gemini model, LangChain 1.x, Frankfurter API)

samples/python/agents/langgraph/README.md

@@ -478,7 +478,7 @@ data: {"id":"6d12d159-ec67-46e6-8d43-18480ce7f6ca","jsonrpc":"2.0","result":{"co
 
 - [A2A Protocol Documentation](https://a2a-protocol.org/)
 - [LangGraph Documentation](https://langchain-ai.github.io/langgraph/)
-- [Frankfurter API](https://www.frankfurter.app/docs/)
+- [Frankfurter API](https://frankfurter.dev/docs/)
 - [Google Gemini API](https://ai.google.dev/gemini-api)
 
 

samples/python/agents/langgraph/app/agent.py

@@ -5,18 +5,17 @@
 
 import httpx
 
+from langchain.agents import create_agent
+from langchain.agents.structured_output import ToolStrategy
 from langchain_core.messages import AIMessage, ToolMessage
 from langchain_core.tools import tool
 from langchain_google_genai import ChatGoogleGenerativeAI
 from langchain_openai import ChatOpenAI
 from langgraph.checkpoint.memory import MemorySaver
-from langgraph.prebuilt import create_react_agent
+from langgraph.checkpoint.serde.jsonplus import JsonPlusSerializer
 from pydantic import BaseModel
 
 
-memory = MemorySaver()
-
-
 @tool
 def get_exchange_rate(
     currency_from: str = 'USD',
@@ -37,7 +36,7 @@ def get_exchange_rate(
     """
     try:
         response = httpx.get(
-            f'https://api.frankfurter.app/{currency_date}',
+            f'https://api.frankfurter.dev/v1/{currency_date}',
             params={'from': currency_from, 'to': currency_to},
         )
         response.raise_for_status()
@@ -59,6 +58,14 @@ class ResponseFormat(BaseModel):
     message: str
 
 
+# Allow the checkpointer to restore the structured response between turns.
+memory = MemorySaver(
+    serde=JsonPlusSerializer(
+        allowed_msgpack_modules=[(ResponseFormat.__module__, ResponseFormat.__name__)]
+    )
+)
+
+
 class CurrencyAgent:
     """CurrencyAgent - a specialized assistant for currency convesions."""
 
@@ -79,7 +86,7 @@ class CurrencyAgent:
     def __init__(self):
         model_source = os.getenv('model_source', 'google')
         if model_source == 'google':
-            self.model = ChatGoogleGenerativeAI(model='gemini-2.0-flash')
+            self.model = ChatGoogleGenerativeAI(model='gemini-3.8-flash')
         else:
             self.model = ChatOpenAI(
                 model=os.getenv('TOOL_LLM_NAME'),
@@ -89,12 +96,12 @@ def __init__(self):
             )
         self.tools = [get_exchange_rate]
 
-        self.graph = create_react_agent(
+        self.graph = create_agent(
             self.model,
             tools=self.tools,
             checkpointer=memory,
-            prompt=self.SYSTEM_INSTRUCTION,
-            response_format=(self.FORMAT_INSTRUCTION, ResponseFormat),
+            system_prompt=f'{self.SYSTEM_INSTRUCTION} {self.FORMAT_INSTRUCTION}',
+            response_format=ToolStrategy(ResponseFormat),
         )
 
     async def stream(self, query, context_id) -> AsyncIterable[dict[str, Any]]:

samples/python/agents/langgraph/app/test_client.py

@@ -27,7 +27,7 @@ async def main() -> None:
 
     base_url = 'http://localhost:10000'
 
-    async with httpx.AsyncClient() as httpx_client:
+    async with httpx.AsyncClient(timeout=60.0) as httpx_client:
         # Initialize A2ACardResolver
         resolver = A2ACardResolver(
             httpx_client=httpx_client,

samples/python/agents/langgraph/pyproject.toml

@@ -7,9 +7,10 @@ requires-python = ">=3.12"
 dependencies = [
     "click>=8.1.8",
     "httpx>=0.28.1",
-    "langchain-google-genai>=2.0.10",
-    "langgraph>=0.3.18",
-    "langchain-openai>=0.1.0",
+    "langchain>=1.0.0",
+    "langchain-google-genai>=3.0.0",
+    "langgraph>=1.0.0",
+    "langchain-openai>=1.0.0",
     "pydantic>=2.10.6",
     "python-dotenv>=1.1.0",
     "uvicorn>=0.34.2",