feat: add variant support for commands (#7713)

[koichincom]

What does this PR do?

Fixes #7713 by the following:

• Adds a variant field to the commands configuration.
• Variant needs to be specified with the model (throws an error if not)
• Invalid variant names show a help message and throw an error (no fuzzy search)

How did you verify your code works?

• Added model and variant fields to the existing packages/opencode/test/config/config.test.ts for config parsing.
• Performed three manual tests by creating an opencode.json in the root:
  • Valid: model and variant are specified (used a temporary toast to verify the variant change).
  • Without variant: only the model is specified.
  • Invalid variant: an invalid variant name was used.

Consideration

When #7156 or #7140 lands, its model-default variant feature might need to be integrated.

[github-actions]

Thanks for your contribution!

This PR doesn't have a linked issue. All PRs must reference an existing issue.

Please:

1. Open an issue describing the bug/feature (if one doesn't exist)
2. Add Fixes #<number> or Closes #<number> to this PR description

See CONTRIBUTING.md for details.

[github-actions]

The following comment was made by an LLM, it may be inaccurate:

I found related PRs that might be relevant to this variant support implementation:

Related PRs (Not exact duplicates, but related features):

1. Add default variant config per agent (Add default variant config per agent #7140) - Add default variant config per agent #7140

   • The current PR mentions that when Add default variant config per agent #7140 lands, its model-default variant feature might need to be integrated

2. feat: add variant support for subagents (feat: Support default variant configuration per agent #7138) [alt of Add default variant config per agent #7140] (feat: add variant support for subagents (#7138) [alt of #7140] #7156) - feat: add variant support for subagents (#7138) [alt of #7140] #7156

   • Similar variant support but for subagents; also mentioned in the PR as potentially needing integration

3. feat: Add variant cycle tooltip in session prompt (feat: Add variant cycle tooltip in session prompt #7743) - feat: Add variant cycle tooltip in session prompt #7743

   • Related variant feature, but focuses on UI tooltip display

These are complementary features rather than direct duplicates. The current PR (#7907) specifically adds variant support for commands, while #7140 and #7156 address variant support for agents/subagents. They may need to be coordinated during integration.

No exact duplicate PRs were found for this specific commands variant implementation.

[Copilot]

Pull request overview

This PR implements variant support for commands as requested in issue #7713. Users can now specify a variant field in command configurations to set a default variant for specific commands, enabling commands to have baked-in reasoning effort levels without requiring manual user selection.

Changes:

• Added optional variant field to command configuration schema
• Implemented validation to ensure variant is only specified with a model
• Added error handling with helpful messages for invalid variant names

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
packages/opencode/src/config/config.ts	Added variant field to Command schema as optional string
packages/opencode/src/command/index.ts	Added variant to Command.Info type and parsed it from config
packages/opencode/src/session/prompt.ts	Implemented validation for variant (requires model, checks validity) and passes variant to prompt execution
packages/opencode/test/config/config.test.ts	Added test case to verify variant field is correctly parsed from config

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