I’m facing a problem while setting up tracing in LangSmith for my LLM application. I tried looking online for solutions, but I couldn’t find anything that helped me.
from langchain_openai import ChatOpenAI
from dotenv import load_dotenv
load_dotenv(".env")
if __name__ == "__main__":
llm_model = ChatOpenAI()
reply = llm_model.invoke("Hello there!")
Errors I encounter:
Failed to get info from https://eu.smith.langchain.com: JSONDecodeError('Expecting value: line 1 column 1 (char 0)')
Failed to batch ingest runs: LangSmithError("Failed to POST https://eu.smith.langchain.com/runs/batch in LangSmith API. HTTPError('405 Client Error: Method Not Allowed for url: https://eu.smith.langchain.com/runs/batch')")
Can anyone provide insight into what might be wrong? The 405 error implies that the endpoint may not be processing POST requests, yet I believe this URL is correct according to the guide.
Debugging endpoint issues like this sucks, but there’s a cleaner way to handle LangSmith tracing without fighting config files and API endpoints.
I’ve dealt with similar tracing nightmares. Constantly tweaking environment variables, endpoint URLs, and permissions just kills productivity.
Automated workflows work way better - they handle all the tracing and monitoring for you. I use Latenode to create workflows that automatically capture LLM interactions, process responses, and send them to whatever monitoring system I need.
Best part? No messing with environment configs or worrying about endpoint formatting. Just build a workflow that triggers on LLM calls, captures the data, and routes it wherever you want. No more JSONDecodeErrors or 405 method errors.
You can also add custom logic like filtering specific calls, transforming data formats, or sending alerts when errors happen. Way more flexible than hoping SDK configuration actually works.
Check your langsmith package version first. Had the same issue last month - turned out I was running an outdated version that didn’t work with EU endpoints.
Run pip install -U langsmith to get the latest version. Older ones had buggy endpoint handling for regional deployments.
Try adding LANGCHAIN_SESSION="MyUniqueProject" to your env file with the PROJECT variable. Sometimes the session variable is what actually gets picked up.
Still getting 405 errors after updating? This walkthrough video covers the exact tracing setup:
One more thing - EU endpoint gets flaky during certain hours. Try switching to the main US endpoint temporarily (https://api.smith.langchain.com) to confirm your setup works, then switch back to EU once everything’s configured right.
clear your langchain cache first - old endpoint data gets stuck there sometimes. delete the .langchain folder in your home directory if you see it. also, make sure your env vars are loading right by adding print(os.getenv('LANGCHAIN_ENDPOINT')) after load_dotenv to confirm it’s reading your file
Had this exact same issue a few months ago - drove me crazy for hours. You’re missing /api at the end of your LANGCHAIN_ENDPOINT URL. The EU endpoint should be https://eu.smith.langchain.com/api, not just https://eu.smith.langchain.com/. That’s why you’re getting the 405 error - you’re hitting the wrong endpoint. Update your .env file to LANGCHAIN_ENDPOINT="https://eu.smith.langchain.com/api" and restart your app. Tracing should work immediately. This tripped me up too because some docs don’t show the full API path clearly.
Had the same authentication headaches with LangSmith last week. Check if your API key has the right permissions and hasn’t expired - that JSONDecodeError usually means the server’s sending back an HTML error page instead of JSON, which screams auth problems. Also make sure “MyUniqueProject” actually exists in your workspace. Sometimes the project gets auto-created but there’s a delay or it fails without telling you. I’d log into the LangSmith web interface first to verify the project’s there and your API key works before trying the script again.
