Fix Claude API Model Not Found Error

Why Does the "Model Not Found" Error Happen?

An HTTP 400 Bad Request or 404 Not Found response with a message declaring that a model was not found indicates that the Anthropic API gateway does not recognize or support the value passed in your request's model parameter.

This failure is almost always caused by one of four specific integration oversights: * An outdated client-side SDK library that does not recognize newer model string constants. * A syntactical error, misspelling, or deprecated naming convention in your code's model parameter string. * API keys configured for a workspace or account tier that does not yet have access to high-tier or preview models. * Incorrect API routing when interfacing with Claude through cloud provider proxies like AWS Bedrock or Google Vertex AI.

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Step 1: Verify and Format the Exact Model String

Anthropic does not support generic, un-versioned model names in its production API endpoints. For example, passing claude-3-5-sonnet or claude-3-opus directly as a parameter will trigger a validation error. You must explicitly reference the specific model date version string.

Update your API payload to use the correct canonical model naming strings:

• Claude 3.5 Sonnet (New/V2): claude-3-5-sonnet-20241022
• Claude 3.5 Sonnet (V1): claude-3-5-sonnet-20240620
• 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

Ensure there are no leading or trailing whitespaces, double quotes within variables, or spelling errors in your parameter initialization.

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Step 2: Update the Anthropic SDK Package

If you are using Anthropic's official SDK libraries (such as @anthropic-ai/sdk in Node.js or anthropic in Python) and referencing a newer model via a built-in helper class or model object, an outdated SDK package will throw an error before the request even leaves your system, or it will construct an invalid payload.

Run the appropriate upgrade command in your terminal depending on your development environment:

Python Environment Upgrade your package using `pip`: ```bash pip install --upgrade anthropic ``` Verify the installed version is current: ```bash python -c "import anthropic; print(anthropic.__version__)" ```

Node.js / JavaScript Environment Update your dependencies using your package manager: ```bash npm install @anthropic-ai/sdk@latest # Or if using Yarn yarn add @anthropic-ai/sdk@latest ```

Restart your runtime environment (Docker containers, local server, or serverless functions) after executing the upgrade to ensure the cached dependencies are cleared.

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Step 3: Check Your Account Tier and Workspace Permissions

Certain cutting-edge or resource-intensive models (such as Claude 3 Opus or specific high-throughput preview endpoints) are gated by Anthropic based on your account's Usage Tier.

If your API key belongs to a newly registered account in Tier 0 (Free Trial), you will receive a "model not found" or access denied error if you attempt to call commercial-tier models.

1. Log into the Anthropic Console.
2. Navigate to your Billing overview.
3. Verify your Usage Tier. To unlock all current-generation models, deposit a minimum of $5.00 to transition your account to Tier 1.
4. If you are operating inside an enterprise workspace, verify with your Administrator that your specific API key has been granted permissions to use the model in question under the Workspaces Settings menu.

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Step 4: Correct Routing for AWS Bedrock or Google Vertex AI

If you are accessing Claude models through cloud service integrations, you cannot use Anthropic's direct API endpoint strings. Cloud providers host models under proprietary ID paths.

• AWS Bedrock: Use the Bedrock model IDs. For Claude 3.5 Sonnet, use us.anthropic.claude-3-5-sonnet-20241022-v2:0 (or your local region equivalent).
• Google Cloud Vertex AI: Use the Vertex model pathways, such as claude-3-5-sonnet@20241022.

Additionally, confirm that you have manually accepted the EULA model terms of service within the AWS Bedrock Model Access console or Google Cloud Console. Without enabling access inside your cloud provider account, the hosting service will return a "model not found" or resource error back to your integration.

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When to Escalate

If you have confirmed your SDK is up-to-date, your naming string is perfectly correct, and your account holds active credits but you still receive the error, check the Anthropic Status Page to verify if there is an active incident or partial outage impacting that specific model's endpoint. If status services are normal, open a support ticket within the Developer Console and provide your target model name, SDK version, and the request_id from your failed response headers.