Claude Code × OpenCode Zen API — Cross-Platform Setup Guide, no proxy, no rate limiting, no bs.

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Privacy notice first: Free models on OpenCode Zen or ANY OTHER FREE LLM PROVIDER may use your prompts to improve their models. Avoid sending sensitive code, credentials, or proprietary information. See the Zen privacy docs and privacy policy for details.

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What is OpenCode Zen?

OpenCode Zen is a free, Anthropic-compatible API gateway that benchmarks the best models and providers for coding agents. While it is designed to pair with OpenCode, it works with any agent — including Claude Code — by simply pointing ANTHROPIC_BASE_URL at https://opencode.ai/zen.

Its stated goal is:

"Benchmark the best models/providers for coding agents." — opencode.ai/docs/zen/#goals

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Working Models

Only two models are currently confirmed to work reliably:

Model	Notes
big-pickle	Recommended. Map all Anthropic model slots to this.
minimax-m2.5-free	Free tier alternative. Data may be used for model training.

Other models won't not work for now. If you care enough, report it as an issues here.

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Known Limitations

• ❌ Claude for Chrome extension is not supported — as Zen is an API backend only, yet playwright works well.
• ❌ Slack, Telegram, etc channels integrations are not supported
• ❌ Only big-pickle and minimax-m2.5-free models work.
• ❌ Again, as these are free models, prompts may be used for training — do not send sensitive or proprietary code.

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Best Known Configuration

This is the recommended config that maps all Anthropic model tiers to big-pickle:

{
  "env": {
    "ANTHROPIC_BASE_URL": "https://opencode.ai/zen",
    "ANTHROPIC_AUTH_TOKEN": "sk-In....", # paste your opencode zen api key here 
    "ANTHROPIC_DEFAULT_SONNET_MODEL": "big-pickle",
    "ANTHROPIC_DEFAULT_OPUS_MODEL": "big-pickle",
    "ANTHROPIC_DEFAULT_HAIKU_MODEL": "big-pickle"
  },
  "model": "big-pickle"
}

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Setup Guide

Step 1 — Install Claude Code

Visit claude-code github repo

Step 2 — Get Your Zen API Key

Visit opencode.ai/zen , create an account and copy your API key, no need to enable billing. Place it in PASTE_YOUR_KEY in settings.json file.

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Step 3 — Configure Your Environment

This config file method is the only method I recommend as it is portable and platform-agnostic.

Fisrt back up you existing config , as you will need to overwrite your existing one.

# macOS / Linux
~/.claude/settings.json

# Windows
%USERPROFILE%\.claude\settings.json

Create or edit settings.json in your home directory:

{
  "env": {
    "ANTHROPIC_BASE_URL": "https://opencode.ai/zen",
    "ANTHROPIC_AUTH_TOKEN": "PASTE_YOUR_KEY",
    "ANTHROPIC_DEFAULT_SONNET_MODEL": "big-pickle",
    "ANTHROPIC_DEFAULT_OPUS_MODEL": "big-pickle",
    "ANTHROPIC_DEFAULT_HAIKU_MODEL": "big-pickle"
  },
  "model": "big-pickle"
}

---

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Step 4 — Launch Claude Code

cd /your/project
claude /logout
claude

Claude Code will automatically use Zen as its backend. Ask it something simple to confirm it is working.

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How It Works

Zen acts as a drop-in replacement for Anthropic's API. Claude Code never knows the difference — all three model tiers (Sonnet, Opus, Haiku) are mapped to big-pickle, which is an alias Zen uses internally. Also it delegate any potential SubAgents errors. The actual underlying model may vary, as Zen benchmarks models anonymously to remove bias.

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Links

• Zen dashboard
• Zen privacy docs
• Zen goals
• Privacy policy
• Terms of service
• Report an issue