How to use OpenCode with a custom Anthropic or OpenAI-compatible provider

OpenCode is an open-source coding agent for the terminal. It talks to models through the Vercel AI SDK's provider packages, which means it can reach CCSub over either the Anthropic protocol or the OpenAI-compatible protocol. Everything lives in one JSON file; edit it and restart OpenCode.

Where the config lives

Option 1: Anthropic protocol (for Claude model IDs)

{
  "$schema": "https://opencode.ai/config.json",
  "provider": {
    "ccsub": {
      "npm": "@ai-sdk/anthropic",
      "name": "CCSub",
      "options": {
        "baseURL": "https://www.ccsub.net/api/v1",
        "apiKey": "{env:CCSUB_API_KEY}"
      },
      "models": {
        "claude-sonnet-5": { "name": "claude-sonnet-5" }
      }
    }
  },
  "model": "ccsub/claude-sonnet-5"
}

Option 2: OpenAI-compatible protocol (for GPT model IDs)

{
  "$schema": "https://opencode.ai/config.json",
  "provider": {
    "ccsub-openai": {
      "npm": "@ai-sdk/openai-compatible",
      "name": "CCSub OpenAI",
      "options": {
        "baseURL": "https://www.ccsub.net/api/v1",
        "apiKey": "{env:CCSUB_API_KEY}"
      },
      "models": {
        "gpt-5.5": { "name": "gpt-5.5" }
      }
    }
  },
  "model": "ccsub-openai/gpt-5.5"
}

@ai-sdk/openai-compatible appends /chat/completions to the base URL. You can keep both providers side by side in the same provider object and switch between them with /models inside OpenCode.

What the fields mean

• The key under provider (ccsub, ccsub-openai) is the provider ID. Name it whatever you like; you will reference it in model names and in /connect.
• {env:CCSUB_API_KEY} reads the key from an environment variable. Add export CCSUB_API_KEY="sk-your-key" to your shell profile and open a new terminal.
• models declares the model IDs you want to use. The model field takes IDs such as claude-sonnet-5; every available ID is on the models page. You can add a limit object (context, output) to each model so OpenCode can track how much context is left — without it, OpenCode cannot warn you before the context fills up.
• The top-level model uses the providerID/modelID form, e.g. ccsub/claude-sonnet-5.

Keeping the key out of the file: /connect

Inside OpenCode, run /connect, choose Other, type the provider ID exactly as it appears in your config (for example ccsub) and paste the key. OpenCode saves it to ~/.local/share/opencode/auth.json, and you can drop apiKey from the config. opencode auth list shows what is stored.

Verify

Run opencode in a project, send a message, and look for the request on the Usage page of your CCSub dashboard. If you manage several tools, CC Switch also has a CCSub preset for OpenCode. For Anthropic's own CLI, see the Claude Code guide.