desktop: model tooltip shows "No reasoning" for openai-compatible models configured with reasoning: true #51846

Description

In the desktop app, the model picker tooltip reports "No reasoning" for custom openai-compatible models that are explicitly configured with reasoning: true and have working reasoning variants. Reasoning itself works fine at runtime (variants apply and thinking output is returned) — only the tooltip's reasoning check is wrong.

Root cause (from the bundled v2.0.18 renderer): the tooltip reads capabilities.reasoning, but the backend never populates a reasoning key inside capabilities — config merge only copies tools/input/output, so capabilities.reasoning is always falsy and the legacy model.reasoning fallback is never reached.

Possible fixes: populate capabilities.reasoning from the model's reasoning config field when building/merging models, and/or have the tooltip fall back to model.reasoning || model.variants?.length > 0.

Plugins

None

OpenCode version

v2.0.18 (desktop app + CLI, channel: latest)

Steps to reproduce

1. Define a custom openai-compatible provider in ~/.config/opencode/opencode.jsonc with a model configured with "reasoning": true and reasoning variants:

   {
     "provider": {
       "llm-provider": {
         "npm": "@ai-sdk/openai-compatible",
         "options": { "baseURL": "https://<internal-endpoint>/model/v1" },
         "models": {
           "GLM-Flash": {
             "reasoning": true,
             "interleaved": { "field": "reasoning" },
             "variants": {
               "low":  { "chat_template_kwargs": { "thinking_mode": "enabled", "thinking_level": "low" } },
               "high": { "chat_template_kwargs": { "thinking_mode": "enabled", "thinking_level": "high" } }
             }
           }
         }
       }
     }
   }

2. Restart OpenCode, open the model picker, and hover the model.

3. The tooltip shows 推理 不支持推理 (No reasoning) — even though the variant selector (High/Low/Max) is available and reasoning works in practice.

Screenshot and/or share link

N/A — text-only tooltip; tooltip shows "No reasoning" while the variant selector is present.

Operating System

macOS (Darwin 27.2.0, arm64)

Terminal

Apple_Terminal (issue observed in the desktop app UI)

Possibly related / same root cause as #50257, #50557, #50608 (capabilities.reasoning is never set).