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Documentation Index

Fetch the complete documentation index at: https://code.claude.com/docs/llms.txt

Use this file to discover all available pages before exploring further.

LLM gateways provide a centralized proxy layer between Claude Code and model providers, often providing:
  • Centralized authentication - Single point for API key management
  • Usage tracking - Monitor usage across teams and projects
  • Cost controls - Implement budgets and rate limits
  • Audit logging - Track all model interactions for compliance
  • Model routing - Switch between providers without code changes

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Gateway requirements

For an LLM gateway to work with Claude Code, it must meet the following requirements: API format The gateway must expose to clients at least one of the following API formats:
  1. Anthropic Messages: /v1/messages, /v1/messages/count_tokens
    • Must forward request headers: anthropic-beta, anthropic-version
  2. Bedrock InvokeModel: /invoke, /invoke-with-response-stream
    • Must preserve request body fields: anthropic_beta, anthropic_version
  3. Vertex rawPredict: :rawPredict, :streamRawPredict, /count-tokens:rawPredict
    • Must forward request headers: anthropic-beta, anthropic-version
Failure to forward headers or preserve body fields may result in reduced functionality or inability to use Claude Code features.
Claude Code determines which features to enable based on the API format. When using the Anthropic Messages format with Bedrock or Vertex, you may need to set environment variable CLAUDE_CODE_DISABLE_EXPERIMENTAL_BETAS=1.
Request headers Claude Code includes the following headers on every API request:
HeaderDescription
X-Claude-Code-Session-IdA unique identifier for the current Claude Code session. Proxies can use this to aggregate all API requests from a single session without parsing the request body.
Claude Code also prepends a short attribution block to the system prompt containing the client version and a fingerprint derived from the conversation. The Anthropic API strips this block before processing, so it does not affect first-party prompt caching. If your gateway implements its own prompt cache keyed on the full request body, set CLAUDE_CODE_ATTRIBUTION_HEADER=0 to omit it.

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Configuration

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Model selection

By default, Claude Code uses standard model names for the selected API format. When ANTHROPIC_BASE_URL points at a gateway that exposes the Anthropic Messages format, Claude Code can query the gateway’s /v1/models endpoint at startup and add the returned models to the /model picker. Set CLAUDE_CODE_ENABLE_GATEWAY_MODEL_DISCOVERY=1 to enable this. Discovery is off by default so that gateways backed by a shared API key do not surface every model the key can access to every user. Each discovered entry is labeled “From gateway” and uses the display_name field from the response when one is provided. This requires Claude Code v2.1.129 or later. Discovery applies only to the Anthropic Messages format. It does not run for Bedrock or Vertex pass-through endpoints, and it does not run when ANTHROPIC_BASE_URL is unset or points at api.anthropic.com. The discovery request authenticates the same way as inference requests: it sends ANTHROPIC_AUTH_TOKEN as a bearer token, or ANTHROPIC_API_KEY as the x-api-key header when no auth token is set, along with any headers from ANTHROPIC_CUSTOM_HEADERS. Only models whose ID begins with claude or anthropic are added to the picker. Results are cached to ~/.claude/cache/gateway-models.json and refreshed on each startup. If the request fails or the gateway does not implement /v1/models, the picker falls back to the cached list from the previous startup or to the built-in model list. If your gateway uses model names that do not match the discovery filter, use the environment variables documented in Model configuration to add them manually.

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LiteLLM configuration

LiteLLM PyPI versions 1.82.7 and 1.82.8 were compromised with credential-stealing malware. Do not install these versions. If you have already installed them:
  • Remove the package
  • Rotate all credentials on affected systems
  • Follow the remediation steps in BerriAI/litellm#24518
LiteLLM is a third-party proxy service. Anthropic doesn’t endorse, maintain, or audit LiteLLM’s security or functionality. This guide is provided for informational purposes and may become outdated. Use at your own discretion.

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Prerequisites

  • Claude Code updated to the latest version
  • LiteLLM Proxy Server deployed and accessible
  • Access to Claude models through your chosen provider

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Basic LiteLLM setup

Configure Claude Code:

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Authentication methods

Static API key
Simplest method using a fixed API key: 
# Set in environment
export ANTHROPIC_AUTH_TOKEN=sk-litellm-static-key

# Or in Claude Code settings
{
  "env": {
    "ANTHROPIC_AUTH_TOKEN": "sk-litellm-static-key"
  }
}
This value will be sent as the Authorization header.
Dynamic API key with helper
For rotating keys or per-user authentication:
  1. Create an API key helper script:
#!/bin/bash
# ~/bin/get-litellm-key.sh

# Example: Fetch key from vault
vault kv get -field=api_key secret/litellm/claude-code

# Example: Generate JWT token
jwt encode \
  --secret="${JWT_SECRET}" \
  --exp="+1h" \
  '{"user":"'${USER}'","team":"engineering"}'
  1. Configure Claude Code settings to use the helper:
{
  "apiKeyHelper": "~/bin/get-litellm-key.sh"
}
  1. Set token refresh interval:
# Refresh every hour (3600000 ms)
export CLAUDE_CODE_API_KEY_HELPER_TTL_MS=3600000
This value will be sent as Authorization and X-Api-Key headers. The apiKeyHelper has lower precedence than ANTHROPIC_AUTH_TOKEN or ANTHROPIC_API_KEY. Using LiteLLM’s Anthropic format endpoint: 
export ANTHROPIC_BASE_URL=https://litellm-server:4000
Benefits of the unified endpoint over pass-through endpoints:
  • Load balancing
  • Fallbacks
  • Consistent support for cost tracking and end-user tracking

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Provider-specific pass-through endpoints (alternative)

Claude API through LiteLLM
Using pass-through endpoint: 
export ANTHROPIC_BASE_URL=https://litellm-server:4000/anthropic
Amazon Bedrock through LiteLLM
Using pass-through endpoint: 
export ANTHROPIC_BEDROCK_BASE_URL=https://litellm-server:4000/bedrock
export CLAUDE_CODE_SKIP_BEDROCK_AUTH=1
export CLAUDE_CODE_USE_BEDROCK=1
Google Vertex AI through LiteLLM
Using pass-through endpoint: 
export ANTHROPIC_VERTEX_BASE_URL=https://litellm-server:4000/vertex_ai/v1
export ANTHROPIC_VERTEX_PROJECT_ID=your-gcp-project-id
export CLAUDE_CODE_SKIP_VERTEX_AUTH=1
export CLAUDE_CODE_USE_VERTEX=1
export CLOUD_ML_REGION=us-east5
For more detailed information, refer to the LiteLLM documentation.

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Additional resources