Listbox

# Implement Listbox in your agent

## Objective
Implement Listbox for this verified behavior: A composite widget of named options that supports one or multiple selections and can be standalone or used as a combobox popup.

## Prerequisites
- Inspect the repository, design system, and existing tests first.
- Preserve unrelated changes and keep the file scope bounded.
- Confirm that Listbox matches the need before writing code.

## Required behavior
- Arrow keys navigate according to the declared control model; focus and selection states are exposed consistently, including when selection follows focus.
- The control exposes whether one or multiple values can be selected and updates every selected state consistently.

## States to cover
- Default preset selected
- Last 30 days selected

## Accessibility
- ARIA role: listbox > option
- The primary control or named region for Listbox has a stable accessible name from visible text or an explicit programmatic label; placeholder text and tooltips are not names.
- The native sized select is one tab stop. In this single-select specimen, selection follows keyboard focus, so active and selected state move together; custom listboxes must declare their own model.
- In this standalone specimen, leaving with Tab preserves the selected value; when a listbox is a popup, dismissal is coordinated by its owning control.
- The list name, four-option count, selected state, disabled state, and this specimen's single-selection mode are exposed by native semantics.
- Tab enters the composite control once
- In this native single-select specimen, arrow navigation updates selection as focus moves
- There is no separate commit command in this specimen
- Platform-supported Home and End keys reach boundaries

## When not to use
- Screen space is scarce and a native Select is sufficient
- Items are commands instead of values

## Acceptance criteria
- Options belong to one named list, whether standalone or used as a popup
- The relationship between focus and selection is declared, including whether selection follows focus
- Arrow, Home, and End behavior is consistent
- The selection mode is explicit

## Guardrails
- Show the proposed changes before any external action.
- Do not publish, send, delete, pay for, or change remote state without explicit authorization.
- Preserve unrelated changes and stop if the scope becomes ambiguous.

## Output format
- Outcome or verdict.
- Files or actions involved.
- Checks run and observable evidence.
- Remaining blockers or limitations.

• Web platform
• Requires · Access to the repository, design system, and tests

# Verify Listbox after implementation

## Objective
Audit the Listbox implementation against its behavior, states, and accessibility requirements without changing it automatically.

## Checks
- Replay the smallest representative journey.
- Check keyboard behavior, focus, accessible name, and announcements.
- Tie each gap to a specific acceptance criterion.

## Guardrails
- Show the proposed changes before any external action.
- Do not publish, send, delete, pay for, or change remote state without explicit authorization.
- Preserve unrelated changes and stop if the scope becomes ambiguous.

## Output format
- Outcome or verdict.
- Files or actions involved.
- Checks run and observable evidence.
- Remaining blockers or limitations.

sha256:1af496920d6ad89f44563ae70e70b921be1fc7525384891cd41d25fa930a50d6

# Debug Listbox in your agent

## Observed symptom
[DESCRIBE THE SYMPTOM HERE]

## Observable checks
- Reproduce the issue with the smallest relevant journey.
- Compare behavior with the documented states and transitions for Listbox.
- Verify keyboard behavior, focus, accessible name, and announcements.

## Possible causes
- The chosen primitive does not match the expected behavior.
- A state, transition, or focus return is missing.
- A neighboring component captures an event or hides an accessible signal.

## Bounded corrections
- Fix the reproduced cause without recreating neighboring components.
- Preserve the public contract and add a focused regression test.
- Do not install dependencies or change remote state without authorization.

## Final verification
- Options belong to one named list, whether standalone or used as a popup
- The relationship between focus and selection is declared, including whether selection follows focus
- Arrow, Home, and End behavior is consistent
- The selection mode is explicit

## Guardrails
- Show the proposed changes before any external action.
- Do not publish, send, delete, pay for, or change remote state without explicit authorization.
- Preserve unrelated changes and stop if the scope becomes ambiguous.

## Output format
- Outcome or verdict.
- Files or actions involved.
- Checks run and observable evidence.
- Remaining blockers or limitations.

• Web platform
• Requires · Access to the repository, design system, and tests

# Prevent the Listbox regression

## Objective
Turn the reproduced cause into a focused regression test and compare Listbox with neighboring concepts before widening the fix.

## Checks
- Prove that the test fails before the fix.
- Prove that it passes after the bounded fix.
- Verify that no neighboring component changed behavior.

## Guardrails
- Show the proposed changes before any external action.
- Do not publish, send, delete, pay for, or change remote state without explicit authorization.
- Preserve unrelated changes and stop if the scope becomes ambiguous.

## Output format
- Outcome or verdict.
- Files or actions involved.
- Checks run and observable evidence.
- Remaining blockers or limitations.

sha256:7ec54a406b38d4149bd896328860494ebbb8e705fe5494baf4918f9cc4e8db9c