Anthropic Credentials validation returns 404 "Resource not found" despite valid API key

[fischer-lindemeier]

Bug Description

When testing Anthropic API credentials in n8n, the validation always fails with the error:
"The resource you are requesting could not be found"
This happens even though the API key is valid and works correctly via HTTP Request Node.

To Reproduce

1. Go to Credentials → Add new → Anthropic
2. Enter a valid Anthropic API key
3. Try different Base URL configurations
4. Click "Retry" or save credentials
5. Error appears: "Couldn't connect with these settings - The resource you are requesting could not be found"

Expected behavior

Credential validation should succeed when a valid API key is provided, allowing the Anthropic Chat Model node to be used in AI Agent workflows.

Debug Info

n8n Version: 2.9.4 (also reproduced on 2.8.3)
Node.js Version: (check via: node -v in your terminal)
Database: SQLite (default) or your DB type
Running n8n via: Docker
Operating System: Linux

Operating System

Docker 13

n8n Version

2.9.4

Node.js Version

Credentials

Database

SQLite (default)

Execution mode

main (default)

Hosting

n8n cloud

[n8n-assistant]

Hey @fischer-lindemeier,

Thank you for reaching out! We’ve received your issue and are looking into it. To help us track this internally, we’ve created a Linear ticket with the reference: "GHC-7062".

We’ll keep you updated as we make progress, but if you have any additional details or context to share, feel free to add them here - it’s always helpful!

Thanks for your patience and for bringing this to our attention.

---

For INTERNAL use only: GHC-7062

[krisn0x]

Please double check if the base URL has any trailing / and remove them. It should look like https://api.anthropic.com

[divazuc]

I'm also experiencing the same issue. Please fix it, this is crucial for the integration with claude.