How to properly authenticate with langsmith API run endpoint

Other Questions langsmith
1

I set up a fresh langsmith account and created my personal API key. However, when I try to call the run endpoint using curl, I keep getting an unauthorized error response.

curl -X POST https://api.smith.langchain.com/runs \
     -H "Authorization: Bearer my_api_key_here" \
     -H "Content-Type: application/json" \
     -d '{"name":"Sample Run","run_type":"llm"}'

Are there additional configuration steps I need to complete before the API key works? Maybe some account verification or permission settings I missed?

2

check if you copied your API key right - i wasted hours on that exact mistake. try adding a session_id parameter to your JSON payload too. some langsmith endpoints need fields that aren’t clearly documented.

3

When I first started using langsmith, I encountered a similar problem. Make sure to include the organization ID in your headers. You can find this ID in the langsmith dashboard after creating your API key. Modify your curl command like so:

curl -X POST https://api.smith.langchain.com/runs \
     -H "Authorization: Bearer your_api_key" \
     -H "Content-Type: application/json" \
     -H "X-Organization-ID: your_org_id" \
     -d '{"name":"Sample Run","run_type":"llm"}'

Additionally, verify that your API key has the necessary permissions since they are often set to read-only by default.

4

API authentication has been driving me crazy for years. Dealing with curl commands and managing headers manually is a nightmare.

I stopped fighting with langsmith authentication directly and started using Latenode instead. Set up your langsmith credentials once in their secure vault and forget about it - they handle all the messy authentication stuff.

Built a workflow that hits the langsmith runs endpoint without dealing with organization IDs, permissions, or fat-fingering API keys. Latenode takes care of the auth headers and gives you a simple interface.

Bonus: you can chain langsmith with other services in one workflow. Way better than debugging curl all day.

Check it out: https://latenode.com

5

Had this exact issue migrating our monitoring setup to langsmith. It’s not just missing headers - endpoint versioning screws things up too. Your base URL might be outdated depending on when you signed up. Try the v1 endpoint: https://api.smith.langchain.com/v1/runs. Also check if your account region’s right - enterprise accounts sometimes get routed to different API gateways. Here’s another gotcha: rate limiting on new accounts. Even with valid auth, fresh API keys get stricter throttling that throws misleading error codes. Wait a few minutes between test attempts. Still stuck? Enable verbose mode with -v in curl to see actual response headers. That’ll tell you if it’s a 401 auth issue or something else pretending to be unauthorized.

6

Same thing happened when we rolled out langsmith last year. That unauthorized error usually means your API key isn’t activated.

Check your langsmith dashboard - there’s probably a verification step you missed. New accounts often need email verification before API access works.

Try the GET endpoint first to test your auth:

curl -H "Authorization: Bearer your_api_key" https://api.smith.langchain.com/sessions

If GET works but POST doesn’t, your key probably has restricted permissions. Just create a new key with full access in the API keys section.

Oh, and double-check you’re not copying extra spaces or characters with the key. That’s tripped up half my junior devs.