How to Fix Claude API 404 Not Found Error

An Anthropic API 404 error (represented as a not_found_error or a standard HTTP 404 Not Found response) indicates that the server could not locate the resource you requested. This typically happens when you reference an invalid or retired model identifier, use an incorrect API endpoint, or run outdated SDK libraries.

Follow these troubleshooting steps to verify your request configuration and fix the error.

What Does a Claude API 404 Error Mean?

Unlike a 401 (Unauthorized) or 403 (Forbidden) error, a 404 error means your credentials may be perfectly valid, but the path or model name you specified does not exist in Anthropic’s current system.

Most frequently, developers encounter this when copy-pasting code snippets containing outdated model strings or when they misconfigure custom routing setups.

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Step 1: Audit Your Model Identifier String

Anthropic utilizes highly specific model naming conventions. If you have any typographical errors, or if you use a model name that has been deprecated and removed, the API will throw a 404 error.

Check your API call's model parameter against the valid string identifiers: * Claude 3.5 Sonnet (New): claude-3-5-sonnet-20241022 (or simply claude-3-5-sonnet-latest in supported SDKs) * Claude 3.5 Haiku: claude-3-5-haiku-20241022 * Claude 3 Opus: claude-3-opus-20240229 * Claude 3 Sonnet: claude-3-sonnet-20240229 * Claude 3 Haiku: claude-3-haiku-20240307

Avoid using generic names like claude-3 or claude-v3-sonnet as they are invalid and will yield a 404 error. Also, confirm that you aren't referencing older Claude 2.x models that have been fully decommissioned.

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Step 2: Upgrade Your Anthropic SDK Library

If you use an outdated version of the SDK, requesting a newer model like claude-3-5-sonnet-20241022 or helper methods (such as the Messages API class instead of legacy TextCompletions) can result in a local or remote 404 route resolution failure.

Upgrade your SDK library to the latest version to ensure all active models and API endpoints are mapped correctly.

For Python environments: ```bash pip install --upgrade anthropic ``` To verify your installed version in Python, run: ```python import anthropic print(anthropic.__version__) ``` Ensure this is at least `0.30.0` or higher to properly support the latest Claude 3.5 models.

For Node.js/JavaScript environments: ```bash npm install @anthropic-ai/sdk@latest ```

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Step 3: Inspect Base URL and Proxy Configurations

If your organization uses custom proxy routing, an API gateway, or local development mocks (like LocalStack or custom mock servers), the HTTP client might be pointing to a path that doesn't exist on Anthropic's gateway.

If you are manually initializing the client, ensure the base URL matches the official Anthropic API endpoint. Check your code for configuration overrides:

Correct Python Client Initialization: ```python from anthropic import Anthropic

By default, base_url is "https://api.anthropic.com" client = Anthropic( api_key="your_api_key", ) ``` If you have specified a custom `base_url` parameter, ensure it does not include trailing paths like `/v1/messages` if your SDK already appends those endpoints internally. The base URL should be strictly `https://api.anthropic.com`.

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Step 4: Verify Workspace and API Key Permissions

Occasionally, a 404 error is thrown if your API key belongs to an isolated workspace that does not have access to the specific model you are requesting (for example, if you are attempting to access a private beta model or an enterprise-only deployment).

1. Go to the Anthropic Console.
2. Navigate to Workspaces and select the workspace containing the API key in use.
3. Click on the Limits tab.
4. Scroll through the listed models. If the model you are calling (e.g., claude-3-5-sonnet-20241022) is not listed in your limits table, that specific workspace cannot access it, resulting in a 404 error when called.

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When to Escalate

If you have updated your SDK, verified your endpoint matches https://api.anthropic.com, confirmed that your model name matches the official docs exactly, and yet you still receive a 404 error, your account may have a unique provisioning issue. Log into the Anthropic Console, click the Help / Support icon in the bottom right, and provide the exact request payload and x-request-id header from your failing response logs.