Officially, it's against TOS. I'm told you can still make it work by adding this to ~/.config/opencode/opencode.json but it risks a ban and you definitely shouldn't do it.

  {
    "plugin": [
      "opencode-anthropic-auth@latest"
    ]
  }

Ah interesting. I have been using OpenCode more and more and I prefer it to Claude Code. I use OpenCode with Sonnet and/or Opus (among other models) with Bedrock, but paying metered rates for Opus is a way to go bankrupt fast!

Just like I shouldn't use an unofficial play store client, right? No one would ever do that.