Connect Claude (Anthropic)

Claude is Anthropic's large language model, excellent at complex coding tasks with a 200K tokens context window.

In regions with network restrictions, you typically need to complete 1.3 Network Configuration first, otherwise you may experience connection timeouts.

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What You'll Be Able to Do

• Get an Anthropic API Key and configure it in OpenCode
• Understand the features of Claude 3.5 Sonnet, Claude 3.7 Sonnet, and other models
• Complete your first conversation using Claude models

Your Current Situation

You might have already:

• Heard about Claude's strong code generation capabilities
• Have an Anthropic API Key or Claude Max subscription
• Want to use Claude models in OpenCode

But don't know how to configure it, or which model to choose.

When to Use This

• You have an Anthropic API Key or Claude Max subscription
• You need Claude's long context capabilities (200K tokens)
• You have high requirements for code quality and reasoning ability

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🎒 Before You Start

Prerequisites

• Anthropic Account: Register at console.anthropic.com
• API Key or Claude Max subscription: Choose one
• Network Environment: Need access to Anthropic API (may require VPN)

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Core Concept

The workflow for configuring Anthropic Claude provider:

Get API Key → Configure in OpenCode → Verify Connection

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Follow Along

Step 1: Get Anthropic API Key

Visit the Anthropic console to get your API Key:

1. Open console.anthropic.com
2. Log in or register an account
3. Click API Keys → Create Key
4. Copy the generated API Key (format: sk-ant-...)

Security Tips

• The API Key is only shown once, save it immediately
• Do not commit the API Key to code repositories
• Rotate API Keys regularly

You should see: A string similar to sk-ant-api03-xxxx-xxxx-xxxx

Step 2: Configure in OpenCode

OpenCode provides two configuration methods, choose the one that suits you:

Method 1: Use Environment Variable (Recommended)

Set the API Key as an environment variable:

macOS/Linux (Temporary)

export ANTHROPIC_API_KEY=sk-ant-api03-your-key-here
opencode

macOS/Linux (Permanent)

# Add to ~/.bashrc or ~/.zshrc
echo 'export ANTHROPIC_API_KEY=sk-ant-api03-your-key-here' >> ~/.zshrc
source ~/.zshrc
opencode

Windows (Temporary)

$env:ANTHROPIC_API_KEY="sk-ant-api03-your-key-here"
opencode

Windows (Permanent)

# Add to system environment variables
[System.Environment]::SetEnvironmentVariable("ANTHROPIC_API_KEY", "sk-ant-api03-your-key-here", "User")

Method 2: Use OpenCode Auth Command

Run the authentication command, OpenCode will save the API Key locally:

opencode auth login

Then:

1. Select Anthropic
2. Paste the API Key
3. Press Enter to complete

You should see: Done or Login successful

Auth Storage Location

OpenCode stores authentication information at:

• All platforms: ~/.local/share/opencode/auth.json (follows XDG specification)

Step 3: Verify Configuration

Verify if the Anthropic provider is configured successfully:

opencode auth list

You should see:

Credentials ~/.local/share/opencode/auth.json
● Anthropic api

Environment
● Anthropic ANTHROPIC_API_KEY

This indicates you have successfully configured the Anthropic provider.

Step 4: View Available Models

View all models provided by Anthropic:

opencode models

You should see something like:

anthropic/claude-3-5-haiku-20241022
anthropic/claude-3-5-sonnet-20241022
anthropic/claude-3-7-sonnet-20250219
anthropic/claude-opus-4-20250514
...

View Complete Model Information

Use opencode models --verbose to see detailed metadata like model names and costs.

Step 5: Have Your First Conversation

Start OpenCode and select a Claude model:

cd /path/to/your/project
opencode

In the OpenCode interface, enter your first question:

Help me write a simple HTTP server

You should see:

1. AI starts generating a response (using Claude model)
2. May invoke tools to create files
3. Provides complete code and explanation

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Claude Model Selection Guide

Anthropic provides multiple Claude models, choose based on your needs:

Model	Model ID	Context Window	Features	Best For
Claude 3.7 Sonnet	claude-3-7-sonnet-20250219	200K	Latest and most powerful, excellent reasoning	Complex tasks, code generation, refactoring
Claude 3.5 Sonnet	claude-3-5-sonnet-20241022	200K	Balanced performance and cost	Daily development, code review
Claude Opus 4	claude-opus-4-20250514	200K	Flagship performance, most expensive	Ultra-complex tasks, research work
Claude 3.5 Haiku	claude-3-5-haiku-20241022	200K	Fast response, low cost	Simple tasks, quick Q&A

Recommended Choices

• Default choice: Claude 3.7 Sonnet (most powerful)
• Cost-sensitive: Claude 3.5 Sonnet (best value)
• Fast response: Claude 3.5 Haiku (fastest)

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Checklist ✅

After completing the above steps, you should be able to:

• [ ] See Anthropic provider in opencode auth list
• [ ] See Claude series models in opencode models
• [ ] Start OpenCode and have a conversation using Claude model
• [ ] See the model return with Claude identification

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Common Issues

Invalid API Key

Symptoms: Shows Authentication failed or Invalid API Key

Causes:

• API Key format error (doesn't start with sk-ant-)
• API Key expired or revoked
• API Key doesn't have permission to access the specified model

Solutions:

1. Check if API Key format is correct
2. Regenerate API Key in Anthropic console
3. Confirm account has sufficient balance or valid subscription

Network Connection Failed

Symptoms: Shows Network error or Connection timeout

Causes:

• Cannot access Anthropic API (may need VPN)
• Unstable network

Solutions:

1. Check network connection
2. Configure proxy (if needed):

export HTTP_PROXY=http://your-proxy:port
export HTTPS_PROXY=http://your-proxy:port

Model Unavailable

Symptoms: Shows Model not found or model list is empty

Causes:

• API Key doesn't have permission to access this model
• Model has been discontinued or renamed

Solutions:

1. Check model access permissions in Anthropic console
2. Use opencode models to view available models
3. Upgrade account plan to access more models

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Lesson Summary

In this lesson you learned:

1. Get API Key: Obtain API Key from Anthropic console
2. Configure Authentication: Use environment variable or opencode auth login
3. Verify Connection: Confirm successful configuration and view available models
4. Model Selection: Understand features and use cases of different Claude models

Key Commands:

Command	Purpose
opencode auth login	Configure provider authentication
opencode auth list	View configured providers
opencode models	View available models

Claude Model Features:

• ✅ Long context window (200K tokens)
• ✅ Strong code generation capability
• ✅ Excellent reasoning ability (Claude 3.7 Sonnet)

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Next Lesson Preview

Next lesson we'll learn about Claude Code Relay.

You'll learn:

• What is Claude Code relay service
• How to configure relay endpoint
• Differences between relay and official API

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Appendix: Source Code Reference

Click to expand source code locations

Last updated: 2026-02-14

Feature	File Path	Line Number
Anthropic provider definition	src/provider/provider.ts	93-103
Environment variable detection	src/provider/provider.ts	841-850
Model data loading	src/provider/models.ts	87-104
Authentication management	src/auth/index.ts	37-70

Key Configuration:

• Environment variable name: ANTHROPIC_API_KEY
• Auth type: API Key only (OAuth not supported)
• Auto-load: false (requires manual API Key configuration)