ACP doesn't respect default model from `opencode.json` config

[AlvaroParker]

Description

I have this config on ~/.config/opencode/opencode.json:

{
  "$schema": "https://opencode.ai/config.json",
  "model": "openai/gpt-5.4",
  "agent": {
    "build": {
      "model": "openai/gpt-5.4",
      "variant": "high"
    },
    "plan": {
      "model": "openai/gpt-5.4",
      "variant": "low"
    }
  }
}

When I run opencode on the terminal, the default model loads correctly. However on ACP (zed), the default model variant is not respected:

I would expect OpenAI/GPT-5.4 (high) to load, since it's my default variant when using the build agent

Plugins

No response

OpenCode version

1.3.13

Steps to reproduce

1. Put this on your opencode.json config:

{
  "$schema": "https://opencode.ai/config.json",
  "model": "openai/gpt-5.4",
  "agent": {
    "build": {
      "model": "openai/gpt-5.4",
      "variant": "high"
    },
    "plan": {
      "model": "openai/gpt-5.4",
      "variant": "low"
    }
  }
}

2. Open an ACP client (for example Zed)
3. The default model variant is not respected

Screenshot and/or share link

No response

Operating System

Arch Linux

Terminal

acp

[github-actions]

This issue might be a duplicate of existing issues. Please check:

• Configure default model is not used in ACP #4001: "Configure default model is not used in ACP" — same problem: default model from opencode.json not respected when using ACP (Zed)
• ACP: session/set_mode does not activate the agent's configured model #18620: "ACP: session/set_mode does not activate the agent's configured model" — same root cause: ACP doesn't apply agent-configured model/variant from config

If your issue is specifically about the agent variant (e.g., high/low) not being applied (rather than just the model itself), it may still warrant a separate report, but please check the above issues first.