Subagent Model Selector

An OpenCode plugin that routes direct subagent tasks to models based on the primary session's selected model and variant.

Use it to give the same subagent a different speed, cost, or capability profile for each primary model you use.

Compatibility

Use OpenCode v1.18.9 or later. Earlier versions might work but have not been tested.

Install And Configure

Before you begin, make sure OpenCode is installed, the providers you need are configured, and the target subagents are available.

1. Choose your models on Models.dev, then run opencode models to confirm the exact provider/model IDs available in your OpenCode installation.
2. Add the plugin to your project opencode.json or global ~/.config/opencode/opencode.json. See the OpenCode configuration documentation for configuration locations and precedence.

{
  "$schema": "https://opencode.ai/config.json",
  "plugin": [
    [
      "@idrisgit/opencode-subagent-model-selector",
      {
        "routes": [
          {
            "primary": {
              "model": "openai/gpt-5.6-sol"
            },
            "subagents": {
              "explore": {
                "model": "openai/gpt-5.6-luna",
                "variant": "medium"
              },
              "general": {
                "model": "openai/gpt-5.6-terra",
                "variant": "medium"
              }
            }
          }
        ]
      }
    ]
  ]
}

1. Restart OpenCode. This route sends direct explore tasks from openai/gpt-5.6-sol to Luna Medium and direct general tasks to Terra Medium.

For a complete, real-world routing setup, see the maintainer's personal opencode.jsonc.

OpenCode installs npm plugins automatically when it starts. See the OpenCode plugin documentation for other plugin-loading options.

Use This Plugin When

• A primary model should delegate exploration or research to a faster, lower-cost model.
• A high-reasoning primary variant should use a stronger subagent model.
• Built-in or custom subagents need different models without changing their prompts or permissions.

For a fixed model that never depends on the primary session, use OpenCode's native agent model configuration.

Routing Rules

• A route matches an exact primary provider/model ID and, optionally, its variant.
• Subagent keys are exact OpenCode agent IDs, such as explore, general, or code-review.
• Routes are evaluated in order. The last matching assignment for an agent wins. A route without primary.variant is a wildcard that matches every variant.
• If no route matches, OpenCode resolves the subagent model normally.
• Only subagents launched directly by a primary session are routed. Nested subagents are unchanged.

Configuration Reference

routes is an ordered array. Every route needs a primary descriptor and a non-empty subagents object.

Field	Required	Description
routes	No	Array of routing rules. Omit it or use [] to make no changes.
routes[].primary.model	Yes	Primary model ID in provider/model form.
routes[].primary.variant	No	A variant string or non-empty array of variants to match. Omit it to match every variant.
routes[].subagents	Yes	Non-empty object keyed by exact OpenCode subagent ID.
routes[].subagents.<agent>.model	Yes	Target model ID in provider/model form.
routes[].subagents.<agent>.variant	No	Target model variant. Omit it to use the target model's default variant.

Models And Variants

Use provider/model for every model value. Find model names on Models.dev, but use the output of opencode models as the final source of truth for your OpenCode installation.

Use the separate variant field rather than adding a variant to a model ID. An omitted primary.variant matches every variant; a string matches one variant; an array matches any listed variant. Use "default" to match the default primary variant.

Put a wildcard base route before variant-specific overrides for the same primary model and subagent. The later variant-specific route then overrides the base assignment. Reversing the order makes the wildcard route win for every variant.

Examples

Override A Base Route For High-Reasoning Sessions

Add this as a second item in routes after the wildcard base route. It routes explore to Terra Medium and general to Terra High for high, xhigh, and max. Other variants continue to use the wildcard route.

{
  "primary": {
    "model": "openai/gpt-5.6-sol",
    "variant": ["high", "xhigh", "max"]
  },
  "subagents": {
    "explore": {
      "model": "openai/gpt-5.6-terra",
      "variant": "medium"
    },
    "general": {
      "model": "openai/gpt-5.6-terra",
      "variant": "high"
    }
  }
}

Override A Terra Session

Place a wildcard route before the xhigh and max override:

[
  {
    "primary": {
      "model": "openai/gpt-5.6-terra"
    },
    "subagents": {
      "explore": {
        "model": "openai/gpt-5.6-luna",
        "variant": "low"
      }
    }
  },
  {
    "primary": {
      "model": "openai/gpt-5.6-terra",
      "variant": ["xhigh", "max"]
    },
    "subagents": {
      "explore": {
        "model": "openai/gpt-5.6-terra",
        "variant": "medium"
      }
    }
  }
]

The later route upgrades direct explore tasks to Terra Medium for xhigh and max; other Terra variants use Luna Low.

Route A Custom Subagent

Use the custom agent ID as a subagent key:

{
  "primary": {
    "model": "openai/gpt-5.6-sol"
  },
  "subagents": {
    "code-review": {
      "model": "anthropic/claude-sonnet-4-6"
    }
  }
}

Configure the agent itself with OpenCode agent configuration.

Schema Validation

Use this JSON Schema to validate the plugin options object:

• Latest release: https://unpkg.com/@idrisgit/opencode-subagent-model-selector/schema.json
• Pinned release: https://unpkg.com/@idrisgit/opencode-subagent-model-selector@<version>/schema.json

OpenCode cannot validate nested plugin options through its main configuration schema. Use this schema in your editor or validation tooling for routes.

Only routes is accepted at the top level. Invalid individual routes are ignored so valid routes can still apply. Invalid top-level options disable all plugin routes.

Troubleshooting

If a subagent is not using the expected model:

1. Run opencode models and verify the primary and target model IDs.
2. Confirm the selected primary variant matches the route, if one is configured.
3. Confirm the subagent ID matches the route key exactly.
4. Check that wildcard base routes appear before variant-specific overrides and that no later matching route overrides the assignment.
5. Confirm the subagent was launched directly by a primary session.
6. Restart OpenCode after changing configuration.
7. If a newly published version is still not loading, quit OpenCode, run rm -rf ~/.cache/opencode/packages/@idrisgit/opencode-subagent-model-selector@latest, then restart. This clears only this plugin's stale npm cache.

The plugin warns in the TUI and OpenCode application log when malformed configuration leaves a subagent without a selected route. For more detail, run opencode --log-level DEBUG and consult the OpenCode troubleshooting guide.

Star The Repository

If this plugin is useful, please star the repository to help others find it.

Report Bugs And Request Features

Open a GitHub issue for bugs or feature requests. Include your OpenCode version, plugin version, redacted configuration, selected primary model and variant, expected result, actual result, and relevant logs.

Development

Clone the repository and install dependencies:

git clone https://github.com/IdrisGit/opencode-subagent-model-selector.git
cd opencode-subagent-model-selector
bun install

Use the local source file in your OpenCode configuration while developing:

{
  "plugin": [
    [
      "file:///path/to/opencode-subagent-model-selector/src/index.ts",
      {
        "routes": []
      }
    ]
  ]
}

Run these checks before publishing:

bun run typecheck
bun run generate-schema
bun run check
bun run build
npm pack --dry-run

License

Licensed under the Apache License 2.0.