# RB-12 MAJOR: hotkey device filtering hard-codes KEY_A / KEY_R

**Severity:** MAJOR
**Path:** `crates/hotkey/src/linux.rs:236-241`
**Source:** [2026-04-22 code review](../code-review-2026-04-22.md)
**Labels:** release-blocker, major, hotkey, correctness
**Status:** RESOLVED (2026-04-22)

## Resolution

Extracted `device_supports_combo(supported, combo) -> bool` as a pure helper.
`try_attach_device` now snapshots the current `HotkeyCombo` from `hotkey_rx`
(returning early with `false` if the listener is unconfigured) and uses the
helper to filter devices by the configured trigger key.

Tests in `crates/hotkey/src/linux.rs` (`linux::tests`):

- `attaches_when_device_supports_configured_trigger`
- `rejects_when_device_lacks_configured_trigger`
- `rejects_when_device_reports_no_keys`
- `attaches_for_non_a_non_r_trigger` (direct regression)

Manual verification of the Ctrl+Shift+D binding in Settings remains on the
ship-gate checklist — code path is correct; runtime GUI check is deferred.

## Problem

`try_attach_device` claims to check whether an input device supports the configured hotkey's key, but the implementation tests for hard-coded `KEY_A` or `KEY_R` instead of consulting the actual `HotkeyCombo` that was configured. Hotkeys bound to any other key (which is most of them) can be silently skipped even when the device supports them.

This is a correctness bug in a user-facing feature. A user who binds Kon to `Ctrl+Shift+D` and sees "no hotkey fires" has no obvious path to diagnose it.

## Acceptance

- Device attachment consults the actual configured `HotkeyCombo.trigger` key code.
- Regression test: `try_attach_device` called with a mock device that supports `KEY_D` attaches when the configured hotkey's trigger is `D`, does not attach when the trigger is a key the device doesn't support.
- Manual verification: bind `Ctrl+Shift+D` in Settings, confirm it fires in a running Kon.

## Fix scope

Small. Replace the hard-coded constants with a lookup from the passed-in `HotkeyCombo`.

## Dependencies

- None — standalone fix.