How to Configure Anthropic Models with OpenClaude: A Complete Guide

Set ANTHROPIC_API_KEY and use --provider anthropic --model <model-id> or OPENAI_MODEL=anthropic/<model-id> to route requests through OpenClaude's built-in Anthropic integration.

OpenClaude treats Anthropic as a first-party provider with dedicated routing, metadata, and transport layers. Whether you're calling Claude 3 Opus directly or routing through a custom proxy, configuration happens through environment variables and CLI flags defined in the provider system.

Selecting an Anthropic Model

You can specify Anthropic models through two primary mechanisms:

CLI Flag Method

openclaude \
  --provider anthropic \
  --model claude-3-opus-20240229 \
  --prompt "Write a TypeScript function that sums an array."

Environment Variable Method

export OPENAI_MODEL="anthropic/claude-sonnet-3.5"
openclaude --prompt "Explain quantum entanglement in plain English."

Both approaches resolve to the same internal route. In src/utils/providerValidation.ts, the validator checks that any model with the anthropic/* prefix belongs to the Anthropic vendor before processing.

Required Credentials

Anthropic integration requires minimal environment setup:

Variable	Required	Purpose
ANTHROPIC_API_KEY	Yes	Bearer token for API authentication
ANTHROPIC_BASE_URL	No	Custom proxy endpoint (defaults to https://api.anthropic.com)

These variables are declared in the Anthropic descriptor's envVarConfig and consumed by the transport layer. In src/utils/teleport/api.ts, the transport automatically injects required headers including anthropic-version and anthropic-beta at lines 274-280.

Minimal Configuration Example

# .env

ANTHROPIC_API_KEY="sk-ant-xxxxxxxxxxxxxxxxxxxx"

No base URL is needed for standard Anthropic API access.

Architecture: How Configuration Flows

OpenClaude separates Anthropic configuration into three distinct layers:

Layer	Responsibility	Key File
Metadata	Descriptor files declare defaults, env-var contracts, and capabilities	src/integrations/define.ts
Routing	Maps user config to concrete provider routes	src/utils/providerProfiles.ts
Transport	Executes HTTP requests with proper headers	src/utils/teleport/api.ts

The default Anthropic profile is identified by ANTHROPIC_DEFAULT_PROFILE_ID at lines 984-990 of providerProfiles.ts. When you specify --provider anthropic, this profile loads automatically.

Custom Anthropic Proxy Configuration

For organizations routing through an intermediate proxy, OpenClaude supports the anthropic-proxy transport kind.

Environment Setup for Custom Proxy

# .env

MY_PROXY_TOKEN="my-proxy-token"
MY_PROXY_BASE_URL="https://my-proxy.example/v1"
MY_PROXY_MODEL="claude-3-haiku-20240307"

export ANTHROPIC_API_KEY="$MY_PROXY_TOKEN"
export ANTHROPIC_BASE_URL="$MY_PROXY_BASE_URL"
export OPENAI_MODEL="anthropic/claude-3-haiku-20240307"

Creating a Custom Proxy Descriptor

Add a new TypeScript file under src/integrations/anthropicProxies/:

// src/integrations/anthropicProxies/my-proxy.ts
import { defineAnthropicProxy } from '../define.js';

export default defineAnthropicProxy({
  id: 'my-proxy',
  label: 'My Anthropic Proxy',
  classification: 'anthropic-proxy',
  defaultBaseUrl: 'https://my-proxy.example/v1',
  defaultModel: 'claude-3-sonnet-20240229',
  setup: {
    requiresAuth: true,
    authMode: 'token',
    credentialEnvVars: ['MY_PROXY_TOKEN'],
    setupPrompt: 'Paste your My-Proxy token.',
  },
  envVarConfig: {
    authTokenEnvVar: 'MY_PROXY_TOKEN',
    baseUrlEnvVar: 'MY_PROXY_BASE_URL',
    modelEnvVar: 'MY_PROXY_MODEL',
  },
  capabilities: {
    supportsStreaming: true,
    supportsVision: false,
    supportsFunctionCalling: true,
    supportsJsonMode: true,
    supportsReasoning: true,
  },
  transportConfig: {
    kind: 'anthropic-proxy',
  },
  usage: { supported: true },
});

After creating the descriptor, regenerate the integration loader:

bun run integrations:generate

Complete Configuration Examples

Direct Anthropic API Access

# .env

ANTHROPIC_API_KEY="sk-ant-abc123..."

# CLI

openclaude \
  --provider anthropic \
  --model claude-3-opus-20240229 \
  --prompt "Refactor this Python script for readability."

Enterprise Proxy with Custom Headers

# .env

ENTERPRISE_ANTHROPIC_KEY="ent-token-xyz789"
ENTERPRISE_BASE_URL="https://ai-gateway.company.internal/anthropic"

export ANTHROPIC_API_KEY="$ENTERPRISE_ANTHROPIC_KEY"
export ANTHROPIC_BASE_URL="$ENTERPRISE_BASE_URL"
export OPENAI_MODEL="anthropic/claude-3-5-sonnet-20240620"

openclaude --prompt "Generate a SQL query for monthly revenue trends."

Key Files for Anthropic Configuration

Understanding these source files helps debug configuration issues:

• src/utils/providerProfiles.ts — Contains ANTHROPIC_DEFAULT_PROFILE_ID and profile resolution logic
• src/utils/providerValidation.ts — Validates model vendor membership at line 525
• src/utils/teleport/api.ts — Builds requests with Anthropic-specific headers
• docs/integrations/how-to/add-anthropic-proxy.md — Authoring guide for custom proxies
• docs/integrations/overview.md — Explains the three-layer architecture

Summary

• Authentication: Set ANTHROPIC_API_KEY as the minimum requirement
• Model selection: Use --provider anthropic --model <id> or OPENAI_MODEL=anthropic/<id>
• Custom proxies: Set ANTHROPIC_BASE_URL or create a full proxy descriptor with transportConfig.kind: 'anthropic-proxy'
• Header injection: The transport layer in teleport/api.ts handles anthropic-version and anthropic-beta automatically
• Extensibility: New proxy configurations only require descriptor changes—no modifications to routing or transport code

Frequently Asked Questions

How do I switch between different Anthropic models?

Use the --model flag with any Anthropic model ID, or set OPENAI_MODEL=anthropic/<model-id>. The system validates the model against Anthropic's vendor list in providerValidation.ts before executing requests.

Can I use Anthropic through a corporate proxy or gateway?

Yes. Either set ANTHROPIC_BASE_URL to your gateway endpoint, or create a custom proxy descriptor in src/integrations/anthropicProxies/ using defineAnthropicProxy. The descriptor approach gives you full control over environment variable names and transport configuration.

Why does OpenClaude use OPENAI_MODEL for Anthropic models?

The OPENAI_MODEL environment variable accepts a vendor-prefixed format (anthropic/<model-id>) to maintain backward compatibility while supporting multiple providers. The parser routes anthropic/* values to the Anthropic provider profile automatically.

What headers does OpenClaude send to the Anthropic API?

The transport layer in src/utils/teleport/api.ts injects anthropic-version and anthropic-beta headers along with the standard Authorization: Bearer header containing your ANTHROPIC_API_KEY.

{
  "mcpServers": {
    "instagit": {
      "command": "npx",
      "args": ["-y", "instagit@latest"]
    }
  }
}