[BUG]: fix(github-copilot): xhigh reasoning variant missing from GPT-5.x models #30092

Description

GitHub Copilot GPT-5.x models (gpt-5.2, gpt-5.4, gpt-5.5, codex variants) only show low, medium, high in the variant picker. xhigh was available previously and the Copilot API still accepts it — it just no longer appears in the reasoning_effort array the /models endpoint returns.

The build() function in packages/opencode/src/plugin/github-copilot/models.ts replaces model.variants entirely from the live API response, so any catalog-defined variants not in that array are silently dropped.

Proposed fix — merge prev variants instead of replacing:

- if (Object.keys(variants).length > 0) {
-   model.variants = variants
- }
+ const merged = { ...(prev?.variants ?? {}), ...variants }
+ if (Object.keys(merged).length > 0) {
+   model.variants = merged
+ }

This means the live API wins on conflicts but catalog-defined variants (e.g. xhigh) aren't lost when the endpoint stops advertising them. Also needs xhigh added to the models.dev catalog entries for GPT-5.x Copilot models.

Plugins

superpowers

OpenCode version

1.15.11

Steps to reproduce

1. Set model to github-copilot/gpt-5.5 (or any GPT-5.x Copilot model)
2. Open variant picker
3. Only see Default, low, medium, high — no xhigh

Operating System

macOS

Terminal

ghostty