[Bug]: Multi-select question with nothing checked cannot be submitted#31991

Before submitting

• I searched existing issues and did not find a duplicate.
• I included enough detail to reproduce or investigate the problem.

Area

apps/web

Steps to reproduce

1. In a Claude thread, have the agent ask an AskUserQuestion with a multiSelect: true question whose options are all optional (none of them means "none").
2. On that question, leave every box unchecked.

Expected behavior

An empty selection is a valid answer to a multi-select question, so the user can submit it or move on.

Actual behavior

With no box checked the user cannot advance or submit. resolvePendingUserInputAnswer (packages/client-runtime/src/state/pendingUserInput.ts) returns null for a multi-select question with no selected options, so derivePendingUserInputProgress (apps/web/src/pendingUserInput.ts) sets canAdvance: false.

The only way through is typing text into "Type your own answer, or leave this blank to use the selected option", which becomes that question's custom answer. The card does not say this. The placeholder reads as if it were the normal composer, so a user who wants none of the options cannot tell whether typing there answers the question or sends a new prompt.

Impact

Minor bug or occasional failure

Version or commit

0.1.8-nightly.20261106.4262 (T3 Code Nightly desktop)

Environment

macOS 26.6.2, Claude Code provider

Workaround

Type "none" in the box. Agents can also add their own "none" option to every multi-select question.