Using Claude Code Max Subscription

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Route Claude Code Max subscription traffic through LiteLLM AI Gateway.

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Why Claude Code Max over direct API?

• Lower costs — Claude Code Max subscriptions are cheaper for Claude Code power users than per-token API pricing

Why route through LiteLLM?

• Cost attribution — Track spend per user, team, or key
• Budgets & rate limits — Set spending caps and request limits
• Guardrails — Apply content filtering and safety controls to all requests

Quick Start Video

Watch the end-to-end walkthrough of setting up Claude Code with LiteLLM Gateway:

<iframe width="840" height="500" src="https://www.loom.com/embed/2d069b9e3bcc4cecaa5eb27a72ba7b3c" frameborder="0" webkitallowfullscreen mozallowfullscreen allowfullscreen></iframe>

Prerequisites

• Claude Code installed
• Claude Max subscription
• LiteLLM Gateway running

Step 1: Configure LiteLLM Proxy

Create a config.yaml with the critical forward_client_headers_to_llm_api: true setting:

model_list:
  - model_name: anthropic-claude
    litellm_params:
      model: anthropic/claude-sonnet-4-20250514

  - model_name: claude-3-5-sonnet-20241022
    litellm_params:
      model: anthropic/claude-3-5-sonnet-20241022

  - model_name: claude-3-5-haiku-20241022
    litellm_params:
      model: anthropic/claude-3-5-haiku-20241022

general_settings:
  forward_client_headers_to_llm_api: true  # Required: forwards OAuth token to Anthropic

litellm_settings:
  master_key: os.environ/LITELLM_MASTER_KEY

:::info Why forward_client_headers_to_llm_api?

This setting forwards the user's OAuth token (in the Authorization header) through LiteLLM to the Anthropic API, enabling per-user authentication with their Max subscription while LiteLLM handles tracking and controls.

:::

Step 2: Start LiteLLM Proxy

litellm --config /path/to/config.yaml

# RUNNING on http://0.0.0.0:4000

Walkthrough

Part 1: Create a Virtual Key in LiteLLM

Navigate to the LiteLLM Dashboard and create a new virtual key for Claude Code usage.

1.1 Open Virtual Keys Page

Navigate to the Virtual Keys section in the LiteLLM Dashboard.

1.2 Click "Create New Key"

1.3 Configure Key Details

Enter a key name (e.g., claude-code-test) and select the models you want to allow access to.

1.4 Select Models

Choose the Anthropic models that should be accessible via this key (e.g., anthropic-claude, claude-4.5-haiku).

1.5 Confirm Model Selection

1.6 Create the Key

Click "Create Key" to generate your virtual key. Copy the generated key value (e.g., sk-otsclFlEblQ-6D60ua2IZg).

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Part 2: Sign into Claude Code Max Plan (Client Side)

Set up Claude Code environment variables and authenticate with your Max subscription.

2.1 Set Environment Variables

Configure Claude Code to use LiteLLM Gateway with your virtual key:

Environment Variables Explained

2.2 Launch Claude Code

Start Claude Code:

claude

2.3 Select Login Method

Choose "Claude account with subscription" (Pro, Max, Team, or Enterprise).

2.4 Authorize in Browser

Claude Code opens your browser to authenticate. Click "Authorize" to connect your Claude Max account.

2.5 Login Successful

After authorization, you'll see the login success confirmation.

2.6 Complete Setup

Press Enter to continue past the security notes and complete the setup.

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Part 3: Use Claude Code with LiteLLM

Now you can use Claude Code normally, and all requests will be tracked in LiteLLM.

3.1 Make a Request in Claude Code

Start using Claude Code - requests will flow through LiteLLM Gateway.

3.2 View Logs in LiteLLM Dashboard

Navigate to the Logs page in LiteLLM Dashboard to see all Claude Code requests.

3.3 View Request Details

Click on a request to see detailed information including tokens, cost, duration, and model used.

The logs show:

• Key Name: claude-code-test (the virtual key you created)
• Model: anthropic/claude-sonnet-4-20250514
• Tokens: 65012 (64679 prompt + 333 completion)
• Cost: $0.249754
• Status: Success

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How It Works

LiteLLM Gateway handles two types of authentication:

1. x-litellm-api-key: Authenticates the request with LiteLLM (usage tracking, budgets, rate limits)
2. OAuth Token (via Authorization header): Forwarded to Anthropic API for Claude Max authentication

sequenceDiagram
    participant User as Claude Code User
    participant LiteLLM as LiteLLM AI Gateway
    participant Anthropic as Anthropic API

    User->>LiteLLM: Request with:<br/>- x-litellm-api-key (LiteLLM auth)<br/>- Authorization: Bearer {oauth_token}

    Note over LiteLLM: 1. Validate x-litellm-api-key<br/>2. Check budgets/rate limits<br/>3. Log request for tracking

    LiteLLM->>Anthropic: Forward request with:<br/>- Authorization: Bearer {oauth_token}<br/>(User's Claude Max OAuth token)

    Note over Anthropic: Authenticate user via<br/>OAuth token from Max plan

    Anthropic-->>LiteLLM: Response

    Note over LiteLLM: Log usage, tokens, cost

    LiteLLM-->>User: Response

Header Flow

Complete Request Flow Example

Here's what a typical request looks like when Claude Code makes a call through LiteLLM:

curl -X POST "http://localhost:4000/v1/messages" \\
  -H "x-litellm-api-key: Bearer sk-otsclFlEblQ-6D60ua2IZg" \\
  -H "Authorization: Bearer oauth_token_from_max_plan" \\
  -H "Content-Type: application/json" \\
  -d '{
    "model": "anthropic-claude",
    "max_tokens": 1024,
    "messages": [{"role": "user", "content": "Hello, Claude!"}]
  }'

LiteLLM then:

1. Validates x-litellm-api-key for gateway access
2. Logs the request for usage tracking
3. Forwards the request to Anthropic with the OAuth Authorization header (because of forward_client_headers_to_llm_api: true)

Advanced Configuration

Per-Model Header Forwarding

For more granular control, you can enable header forwarding only for specific models:

model_list:
  - model_name: anthropic-claude
    litellm_params:
      model: anthropic/claude-sonnet-4-20250514

  - model_name: claude-3-5-haiku-20241022
    litellm_params:
      model: anthropic/claude-3-5-haiku-20241022

litellm_settings:
  master_key: os.environ/LITELLM_MASTER_KEY
  model_group_settings:
    forward_client_headers_to_llm_api:
      - anthropic-claude
      - claude-3-5-haiku-20241022

Budget Controls

Set up per-user budgets while using Max subscriptions:

model_list:
  - model_name: anthropic-claude
    litellm_params:
      model: anthropic/claude-sonnet-4-20250514

general_settings:
  forward_client_headers_to_llm_api: true
  database_url: "postgresql://..."

litellm_settings:
  master_key: os.environ/LITELLM_MASTER_KEY

Then create virtual keys with budgets:

curl -X POST "http://localhost:4000/key/generate" \\
  -H "Authorization: Bearer $LITELLM_MASTER_KEY" \\
  -H "Content-Type: application/json" \\
  -d '{
    "key_alias": "developer-1",
    "max_budget": 100.00,
    "budget_duration": "monthly"
  }'

Troubleshooting

OAuth Token Not Being Forwarded

Symptom: Authentication errors from Anthropic API

Solution: Ensure forward_client_headers_to_llm_api: true is set in your config:

general_settings:
  forward_client_headers_to_llm_api: true

LiteLLM Authentication Failing

Symptom: 401 errors from LiteLLM Gateway

Solution: Verify x-litellm-api-key header is set correctly in ANTHROPIC_CUSTOM_HEADERS:

curl -X GET "http://localhost:4000/key/info" \\
  -H "Authorization: Bearer sk-otsclFlEblQ-6D60ua2IZg"

Model Not Found

Symptom: Model not found errors

Solution: Ensure the ANTHROPIC_MODEL matches a model name in your config:

curl "http://localhost:4000/v1/models" \\
  -H "Authorization: Bearer sk-otsclFlEblQ-6D60ua2IZg"

Related Documentation

• Forward Client Headers - Detailed header forwarding configuration
• Claude Code Quickstart - Basic Claude Code + LiteLLM setup
• Virtual Keys - Creating and managing API keys
• Budgets & Rate Limits - Setting up usage controls