💡 The elevator pitch

Copilot Chat is great — but its premium models cost $39/mo (Pro+), and the free tier is rate-limited. This extension plugs OpenCode's model gateway into Copilot Chat's model picker. OpenCode Zen gives you 2-5 rotating free models (Big Pickle is always free; DeepSeek V4 Flash, MiMo-V2.5, and others rotate) plus paid models like Claude Opus, GPT-5.5, and Gemini at pay-as-you-go rates. OpenCode Go ($10/mo, $5 first month promo) gives you a curated set of open models (DeepSeek V4 Pro, Kimi K2.6, GLM-5.1, Qwen3.7 Max, MiMo V2.5 Pro) with generous usage limits. You keep the native Copilot UI, tool-calling, and Agent Mode — you just get way more models, often cheaper than Copilot Pro+.

🔥 Why you'll love it

⚡ Quick Start (60 sec)

1.  Install GitHub Copilot Chat (free) ──────────────────────────── ✓
2.  Install this extension ──────────────────────────────────────── ✓
3.  Get an OpenCode Zen API key → opencode.ai/auth ─────────────── ✓
4.  Open Copilot Chat → click model → "Add Models" → OpenCode Zen ── ✓
5.  Paste API key → pick a free model → CHAT 🎉

🎬 Demo

Selecting an OpenCode model from the Copilot Chat model picker.

🧠 Models

The extension fetches live model lists on every startup from:

⭐ OpenCode Go (subscription — $10/mo, $5 first month promo)

🆓 OpenCode Zen — Free models (no payment needed)

OpenCode Zen offers 2-5 rotating free models — no balance required. Big Pickle is always free; other models rotate (DeepSeek V4 Flash Free, MiMo-V2.5 Free, Nemotron, etc.). Without a balance, rate limits are low. Adding $20+ to your Zen balance significantly improves rate limits on free models.

Note: Free models rotate periodically. The table below shows current offerings, but availability may change. Big Pickle is the only model guaranteed to always be free.

💰 OpenCode Zen — Paid models (requires balance)

Add a payment method to your Zen account to unlock these models at pay-as-you-go rates.

Set opencodego.freeOnly: false to show paid Zen models in the picker (default shows only free models).

📊 GitHub Copilot vs This Extension

GitHub Copilot has four tiers now — Free, Pro ($10/mo), Pro+ ($39/mo), and Max ($100/mo). Here's how BYOK via OpenCode compares:

Not a replacement — this extension extends Copilot Chat. You still need the (free) Copilot Chat extension + a GitHub account. BYOK models bypass the Copilot subscription billing entirely — you pay OpenCode directly (or nothing, on Zen free).

💡 When to use which?

• Copilot Free + OpenCode Zen → $0 total. Best for students, hobbyists, and trying frontier models.
• Copilot Pro + OpenCode Go → $10/mo for Copilot's polish + $10/mo for DeepSeek Pro, Kimi K2.6, Qwen3.7 Max.
• This extension alone → Already works with just Copilot Free. Keep Copilot for autocomplete, use OpenCode models for chat/agent when you need variety or free tier.

✨ Features Deep Dive

🧠 Thinking & Reasoning Controls

Per-model reasoning configuration, dynamically enhanced with reasoning_options from models.dev:

opencodego.debugReasoning — writes provider reasoning_content to Output → OpenCode for debugging.

📊 Usage Tracking

• Go Usage Tracker — real-time burn-rate of OpenCode Go subscription:
  • Tracks 5-hour rolling ($12), weekly ($30), monthly ($60) tiers.
  • Client-side cost calc: token usage × per-model pricing (input/output/cache_read).
  • Status bar: Go: 27%·62%·75% — ⚠ warning when any tier exceeds 80%.
  • Persisted in VS Code globalState — survives restarts.
• Response usage bar — latest prompt/output/total/cache summary after each response.
• Normalized usage DataPart — emits usage MIME so Copilot Chat's context widget shows accurate token counts.

🪟 Agents Window (Copilot CLI) Support

OpenCode models appear in the VS Code Agents window model picker when starting a Copilot CLI / Background agent session — not just the regular Chat view. Two sets of models are available:

How it works:

Setup:

1. Agent models are enabled by default (agentsWindow: true). No changes needed for basic usage.
2. Add this to your VS Code settings.json to enable the extension in the Agents window process:

   "extensions.supportAgentsWindow": {
     "ltmoerdani.opencode-copilot-chat": true
   }
   

3. Reload the window (Developer: Reload Window).
4. Open the Agents window → start a new session → select Copilot CLI as the agent type.
5. Open the model picker — OpenCode models appear under Local (normal models) and Copilot (agent-host variants).

Normal OpenCode models (opencodego, opencodezen) appear in the Local section of the Agents window picker from VS Code ≥1.126 onwards. On ≤1.125 they may require the supportAgentsWindow setting. Agent-host variants (opencodego-agent, opencodezen-agent) appear under Copilot because they carry targetChatSessionType: "copilotcli" and are matched by CopilotChatSessionsProvider.

To manage agent API keys separately or see agent vendors in the Manage panel, enable:

"opencodego.showAgentModelsInManagePanel": true

🛠️ Smart Routing & Reliability

• Native endpoint routing per family (see Models table)
• Tool-calling forwarded in correct format per endpoint (OpenAI tool_calls vs Anthropic tool_use)
• Sticky gateway headers (x-opencode-session, x-opencode-request, x-opencode-client) for affinity
• Request & stream timeouts — defaults 600s total / 120s idle; configurable
• ground tag filtering — opencodego.stripThinkTags (auto strips MiniMax only, always, never)

🔍 Diagnostics

🔧 Settings

🎛️ Commands

The easiest way to manage your key is Settings → Language Models (gear ⚙). For advanced use, open the Command Palette (Cmd/Ctrl+Shift+P):

❓ FAQ

"extensions.supportAgentsWindow": {
  "ltmoerdani.opencode-copilot-chat": true
}

🏗️ Architecture

flowchart LR
    A[VS Code Copilot Chat] -->|model picker| B{Which vendor?}
    B -->|Copilot| C[GitHub models]
    B -->|OpenCode Go| D[Go API Key]
    B -->|OpenCode Zen| E[Zen API Key]

    D --> F[Smart Router]
    E --> F

    F -->|GPT| G[" /responses "]
    F -->|Gemini| H[" :streamGenerateContent "]
    F -->|Claude + MiniMax| I[" /messages "]
    F -->|Qwen/DeepSeek/GLM/Kimi/MiMo| J[" /chat/completions "]

    G & H & I & J --> K[opencode.ai gateway]
    K --> L[SSE Stream]
    L -->|tool_calls / tool_use| A
    L -->|usage DataPart| M[Status Bar]
    L -->|context hook| N[Context Widget]

See docs/architecture/ for the full provider architecture, routing, and metadata resolution docs.

🤝 Contributing

Contributions welcome! Whether it's a typo fix, new model support, or a screenshot — every PR counts.

📋 See CONTRIBUTING.md for guidelines. 💬 Discussions: GitHub Discussions 🐞 Bugs: Issue Tracker

Development

npm install      # install deps
npm run compile  # build TypeScript
npm run watch    # watch mode
npm run package  # build .vsix

Press F5 in VS Code to launch an Extension Development Host.

📈 Roadmap

• [ ] 🎥 Demo GIF + screenshots
• [ ] 🌐 GitHub Pages landing page
• [ ] 📦 Publish to VS Code Marketplace
• [ ] 🏷️ Verified publisher badge
• [ ] 🔔 Webhook for new OpenCode models
• [ ] 🎨 Custom model aliases / favorites
• [ ] 📊 Usage charts webview panel
• [ ] 🌍 i18n (id, zh, ja)

Have an idea? Start a discussion or open a feature request.

⭐ Star History

 👆 Star this repo if it saved you money or unlocked a model you needed!

💬 Community

If this saves you money or unlocks a model you needed — ⭐ star the repo and share it!

📄 License

MIT © 2026 ltmoerdani

OpenCode is a trademark of opencode.ai. This project is independent and not affiliated with GitHub, Microsoft, Anthropic, OpenAI, Google, or any model provider.