[FEATURE]: Interactive custom provider registration flow in /connect command palette

Feature hasn't been suggested before.

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Describe the enhancement you want to request

Add a complete, interactive provider registration flow in the TUI /connect command palette that lets users register any OpenAI-compatible provider end-to-end — entering an endpoint URL, optional API key, auto-discovering available models, and selecting which models to enable — all without manually editing opencode.jsonc.

Motivation

OpenCode has many built-in providers, but users frequently need to add self-hosted models (Ollama, vLLM, LocalAI), third-party platforms (DeepSeek, Qwen, Kimi), or corporate API gateways. Currently this requires manually editing opencode.jsonc with the correct npm package name, schema, and model capabilities — which is error-prone and not discoverable.

Proposed Flow

Step 1 — Endpoint

Provider endpoint URL: https://api.deepseek.com/v1

• Accept any URL (local or remote)
• Validate the URL is reachable

Step 2 — API Key (optional)

API key (leave empty for no auth): ****

• Optional because local providers (Ollama, LocalAI) typically don't need a key
• Some platforms return different model lists based on whether a key is provided

Step 3 — Auto-fetch Models
After entering endpoint + key, call the provider's /v1/models endpoint to discover available models:

Fetching models from https://api.deepseek.com/v1/models ...

Available models:
  [x] deepseek-chat          (context: 64000, output: 8000)
  [x] deepseek-reasoner      (context: 64000, output: 8000)
  [ ] deepseek-v3            (context: 128000, output: 16000)

Select models to enable (space to toggle, enter to confirm):

• Pre-select all models, let user deselect unwanted ones
• Show model name and basic info when available
• Fall back to manual model name input if /v1/models is not supported

Step 4 — Confirm & Save

Provider: deepseek
Endpoint: https://api.deepseek.com/v1
Models: deepseek-chat, deepseek-reasoner

Save to: [Global ~/.config/opencode/opencode.jsonc] / [Project .opencode/opencode.jsonc]
Confirm? (y/n)

Expected Config Output

{
  "providers": {
    "deepseek": {
      "npm": "@ai-sdk/openai-compatible",
      "options": {
        "apiKey": "sk-xxx",
        "baseURL": "https://api.deepseek.com/v1"
      },
      "models": {
        "deepseek-chat": {
          "name": "deepseek-chat",
          "tool_call": true,
          "limit": { "context": 64000, "output": 8000 }
        }
      }
    }
  }
}

Relationship to Existing Issues

This request builds on and unifies several related issues:

• #44450 — Requests a URL textbox in /connect for custom connectors (Step 1)
• #6231 — Requests auto-discovery of models from OpenAI-compatible endpoints (Step 3)
• #33704 — Requests GUI options to edit custom providers and manage model lists

This proposal differs by providing a single, cohesive, step-by-step interactive flow in the TUI that covers the full lifecycle (endpoint → auth → model discovery → config generation → save), rather than isolated pieces. Ideally this could serve as the implementation plan that ties those three issues together.

Technical Notes

• The /v1/models endpoint is part of the OpenAI API spec and supported by most compatible providers
• The config should use @ai-sdk/openai-compatible as the default adapter, with future support for other adapters (@ai-sdk/anthropic, @ai-sdk/google) if the endpoint is detected
• Consider supporting both global and project-level config save locations

Environment

• opencode version: 2.0.3
• OS: Windows_NT 10.0.26200 (win32 x64)
• Terminal: TUI mode