Claude Code - Fixing Invalid Beta Header Errors

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Claude Code - Fixing Invalid Beta Header Errors

When using Claude Code with LiteLLM and non-Anthropic providers (Bedrock, Azure AI, Vertex AI), you may encounter "invalid beta header" errors. This guide explains how to fix these errors locally or contribute a fix to LiteLLM.

What Are Beta Headers?

Anthropic uses beta headers to enable experimental features in Claude. When you use Claude Code, it may send beta headers like:

anthropic-beta: prompt-caching-scope-2026-01-05,advanced-tool-use-2025-11-20

However, not all providers support all Anthropic beta features. When an unsupported beta header is sent to a provider, you'll see an error.

Common Error Message

Error: The model returned the following errors: invalid beta flag

How LiteLLM Handles Beta Headers

LiteLLM automatically filters out unsupported beta headers using a configuration file:

litellm/litellm/anthropic_beta_headers_config.json

This JSON file lists which beta headers are unsupported for each provider. Headers not in the unsupported list are passed through to the provider.

Quick Fix: Update Config Locally

If you encounter an invalid beta header error, you can fix it immediately by updating the config file locally.

Step 1: Locate the Config File

Find the file in your LiteLLM installation:

# If installed via pip
cd $(python -c "import litellm; import os; print(os.path.dirname(litellm.__file__))")

# The config file is at:
# litellm/anthropic_beta_headers_config.json

Step 2: Add the Unsupported Header

Open anthropic_beta_headers_config.json and add the problematic header to the appropriate provider's list:

{
  "description": "Unsupported Anthropic beta headers for each provider. Headers listed here will be dropped. Headers not listed are passed through as-is.",
  "anthropic": [],
  "azure_ai": [],
  "bedrock_converse": [
    "prompt-caching-scope-2026-01-05",
    "bash_20250124",
    "bash_20241022",
    "text_editor_20250124",
    "text_editor_20241022",
    "compact-2026-01-12",
    "advanced-tool-use-2025-11-20",
    "web-fetch-2025-09-10",
    "code-execution-2025-08-25",
    "skills-2025-10-02",
    "files-api-2025-04-14"
  ],
  "bedrock": [
    "advanced-tool-use-2025-11-20",
    "prompt-caching-scope-2026-01-05",
    "structured-outputs-2025-11-13",
    "web-fetch-2025-09-10",
    "code-execution-2025-08-25",
    "skills-2025-10-02",
    "files-api-2025-04-14"
  ],
  "vertex_ai": [
    "prompt-caching-scope-2026-01-05"
  ]
}

Step 3: Restart Your Application

After updating the config file, restart your LiteLLM proxy or application:

# If using LiteLLM proxy
litellm --config config.yaml

# If using Python SDK
# Just restart your Python application

The updated configuration will be loaded automatically.

Contributing a Fix to LiteLLM

Help the community by contributing your fix! If your local changes work, please raise a PR with the addition of the header and we will merge it.

How Beta Header Filtering Works

When you make a request through LiteLLM:

sequenceDiagram
    participant CC as Claude Code
    participant LP as LiteLLM
    participant Config as Beta Headers Config
    participant Provider as Provider (Bedrock/Azure/etc)

    CC->>LP: Request with beta headers
    Note over CC,LP: anthropic-beta: header1,header2,header3
    
    LP->>Config: Load unsupported headers for provider
    Config-->>LP: Returns unsupported list
    
    Note over LP: Filter headers:<br/>- Remove unsupported<br/>- Keep supported
    
    LP->>Provider: Request with filtered headers
    Note over LP,Provider: anthropic-beta: header2<br/>(header1, header3 removed)
    
    Provider-->>LP: Success response
    LP-->>CC: Response