Combobox: Interaction specification

Defines states, triggers, user actions, responsive behavior, content rules, and failure states for the combobox pattern. It fixes adoption boundaries and observable failure evidence while keeping environment-specific limits configurable.

Package status: reference context ready for human review. The contract and test scenarios are complete, but no claim is made that an adopting implementation has passed them.

Decision

For Combobox, adopt a reusable state and interaction contract using native semantics where available. Define a deterministic user journey with visible state, reversible choices where possible, preserved input, and accessible recovery. This package is a reference contract: the adopting team must choose numeric limits, providers, jurisdictions, and operational owners from evidence in its own environment.

Scope

• The Combobox actors, inputs, outputs, states, policy or schema versions, and externally visible outcomes described by this ux block.
• Primary and alternate interfaces, background work, caches, integrations, support paths, and evidence that can exercise the same boundary.
• Adoption-specific configuration, rollout, recovery, and verification responsibilities needed to apply the reference safely.

Outside this block

• Choosing a universal vendor, framework, jurisdiction, numeric threshold, retention period, or service-level objective for every adopter.
• Claiming that packaged scenarios have run against a downstream implementation or that this reference grants legal, security, or accessibility certification.

Contract

• Define trigger, open or active, loading, success, empty, invalid, error, disabled, and dismissal states that the pattern can enter.
• Specify keyboard input, focus entry and return, accessible name, announcements, pointer behavior, and touch target behavior together.
• Make destructive, irreversible, or external effects explicit and prevent duplicate activation while work is pending.
• Keep content hierarchy and actions usable at narrow widths, high zoom, text expansion, forced colors, and reduced motion.
• Show progress only while work is actually pending and prevent duplicate activation without hiding the user's committed intent.
• Use plain, action-specific messages that distinguish validation, permission, connectivity, conflict, and terminal failure.
• Implement the appropriate editable or select-only combobox pattern with an accessible name, expanded state, controlled popup relationship, and active descendant or focus behavior.
• Support expected arrow, typing, Escape, Enter, Tab, composition, touch, and screen-reader interactions while distinguishing highlighted, selected, and committed values.

Implementation guidance

• Prototype the longest, empty, slow, offline, denied, and assistive-technology paths before locking the happy-path layout.
• Model Combobox inputs, outputs, actors, states, invariants, side effects, and evidence before selecting framework or vendor details.
• Store the applicable Combobox contract or policy version with material state so migrations, replay, and support decisions remain attributable.
• Introduce the path behind controlled rollout, compare expected and observed outcomes, and keep a tested recovery route until adoption evidence is complete.

Failure handling and safeguards

• On failed action, preserve relevant input and focus, announce the result, and return the component to a state with a safe recovery path.
• Invalid or contradictory Combobox state is rejected or quarantined; the implementation never guesses a value that broadens authority or duplicates an effect.
• Retries are bounded and use durable identity; after exhaustion, work reaches an inspectable terminal state with an accountable owner.

Verification and operations

• Complete the journey with keyboard, touch, screen reader, narrow viewport, delayed network, and a recoverable server error.
• Monitor Combobox success, denial, validation failure, dependency failure, retry exhaustion, and recovery by contract version without sensitive payload dimensions.
• Re-run paired positive and negative fixtures after policy, schema, dependency, migration, or boundary changes and preserve the resulting evidence.

Adoption assumptions

• Names and values in the example are a concrete fixture, not universal defaults; adopters replace them through documented evidence and ownership.
• The adopting system can provide authenticated identity, durable operation or record versions, bounded telemetry, and a controlled path for change.

The executable-looking examples in this package are fixtures and acceptance contracts. Run the collection validator to check structure and metadata, then translate and execute the scenarios in the target repository before recording implementation evidence.

References

• W3C Web Content Accessibility Guidelines 2.2
• WAI-ARIA Authoring Practices Guide