anthropic api 404 model not found error

Encountering a 404 error when making a call to the Anthropic API typically means the system cannot locate the specific resource, endpoint, or model identifier you have requested. This guide explains how to correct your request configuration to resolve this error quickly.

1. Verify your model identifier string

Anthropic frequently deprecates older model strings to streamline backend operations. Check if you are using legacy identifiers such as claude-2 or claude-v1. Update your payload to use modern, active identifiers such as claude-3-5-sonnet-latest or claude-3-opus-latest to avoid the model not found error.

2. Check for endpoint base URL typos

Ensure your client is pointing to the correct API base URL and path. The Messages API endpoint should be https://api.anthropic.com/v1/messages. If you are manually constructing your HTTP requests or trying to access deprecated legacy endpoints like /v1/complete, your request may fail with a 404 code.

3. Handle service capacity interruptions

Sometimes, temporary backend routing issues on Anthropic's side can masquerade as a 404 error. If you are certain your model string and URL are correct, check if the wider system is experiencing issues. You can refer to our advice on handling the Anthropic API 529 Overloaded Error to see how to manage transient network routing drops.

4. Update your Anthropic SDK library

Outdated client SDKs can append incorrect paths or hardcode old model definitions that are no longer supported. Run npm update @anthropic-ai/sdk for Node.js projects or pip install --upgrade anthropic for Python environments to ensure your local libraries target the correct API paths.