bug: /model slash command crashes when provider has >25 models (Discord Select Menu limit)

[sammylch]

Bug Description

The /model Discord slash command fails when the ACP agent backend (OpenCode) reports more than 25 available models. Discord's StringSelectMenu component has a hard limit of 25 options.

Error

From bot.log:

ERROR openab::discord: failed to respond to slash command
  error=Invalid Form Body (data.components.0.components.0.options: Must be between 1 and 25 in length.)
  category="model"

Discord shows: "The application did not respond"

Environment

• OpenAB: built from source (latest main)
• Agent: OpenCode (opencode acp)
• Provider: OpenCode Go (reports 25+ models including GLM, Kimi, DeepSeek, Qwen, MiniMax, MiMo variants)
• Platform: Discord

Steps to Reproduce

1. Configure OpenAB with OpenCode as the agent backend
2. Authenticate OpenCode with OpenCode Go provider (which has 25+ models)
3. Type /model in a Discord channel
4. Discord shows "The application did not respond"

Expected Behavior

The /model command should handle providers with >25 models gracefully.

Suggested Fix

1. Truncate to 25 most relevant models (prioritize current provider)
2. Paginate with multiple Select Menus or "Next page" button
3. Text input — accept /model <name> as direct switch without Select Menu
4. Filter by provider — show providers first, then models within that provider

[CHC-Agent]

Issue at a Glance

User types /model
       │
       ▼
  pool.get_config_options(thread_key)
       │
       ▼
  build_config_select(options, "model")     ← discord.rs L669-700
       │
       ▼
  maps ALL options → CreateSelectMenuKind::String
       │
       ▼
  options.len() > 25?
       │
  YES ─┤
       ▼
  Discord API rejects:
  "Invalid Form Body
   (data.components.0.components.0.options:
    Must be between 1 and 25 in length.)"
       │
       ▼
  User sees: "The application did not respond"

Hi @sammylch,

Confirmed — build_config_select() at discord.rs L669-700 maps all ACP configOptions directly into CreateSelectMenuKind::String without any truncation or pagination. Discord's StringSelectMenu has a hard limit of 25 options.

Related:

• No existing PRs or duplicate issues found.

Suggested approach: keep the Select Menu but add button-based pagination when options exceed 25. Each page shows up to 25 models in a Select Menu, with ◀/▶ buttons to switch pages. This preserves the current UX for providers with ≤25 models (no change) and scales for larger providers. PR welcome.