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ADR-v2-043 — Gesture Chords

Status: Accepted (2026-07-02) · Wave F Context links: [[adr-v2-023-semg-silent-input]] (sensor sibling), [[adr-v2-030-mouse-grid]], [[adr-011]]

Context

The Wave F research (#9) proposes binding multi-input "chords" — a held hotkey combined with a head nod, a second key, or an sEMG squeeze — to actions (send, undo, switch profile) so power users get modal control without leaving hold-to-talk. Anchors: MediaPipe head-pose, the existing EMG YESP backend, chorded-input HCI literature. Nothing in the prior 42 composes simultaneous inputs into a single action.

Decision

Add an opt-in Gesture Chords: [gesture] enabled=false. The pure core is an input-agnostic chord resolver: normalize_chord(keys) canonicalizes a set of simultaneously-held inputs into a stable chord id, and resolve_chord(keys, mapping) maps it to a bound action (or None). The physical sensors (head-pose via MediaPipe, sEMG via the existing EMG backend) are lazy behind their own extras and only feed input tokens into the resolver. OFF by default.

Consequences

  • Input-agnostic: the same resolver serves key-combos today and head/sEMG chords when those backends are present.
  • Pure normalization/lookup → fully testable with no hardware.
  • Privacy (ADR-011): resolver sees only abstract input tokens; sensor data stays with its backend.
  • Caveat: chord collisions/false triggers → conservative empty default mapping, off by default.