FA-31867 / Keyboard interactions / Member archive

Keyboard usage snapshot delta decoder: Modifier release delta includes presses or still-held modifiers · case 02

The event trace violates the modifier release delta rule and produces incorrect keyboard state or command output.

Member previewVariant 2 · 3 implementations · 8 checks per implementation

Case contract

Each report is [modifier_mask,usage_slots]. Usages are integers >=0; 0 is padding, 1 is an error sentinel that invalidates the whole report. Other usages are unique logical keys even when slots duplicate. Modifier bits 0..7 identify M0..M7. Emit sorted key releases, sorted modifier releases, sorted modifier presses, then sorted key presses per valid report. Return emitted [phase,kind,identity] and final usage/modifier sets. Inputs are finite ordered event traces; return the stated deterministic state. Batch entries are independent. N varies the number of independent input transactions.

Why this case matters

Controlled keyboard event processing model for debugging application event logic.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
hid-report-delta scenario 2	`[[[["up", "mod", 0], ["down", "mod", 0], ["down", "key", 2], ["down", "key", 3]], [2, 3], [0], 0], [[["up", "mod", 0], ["down", "mod", 0], ["down", "key", 2], ["down", "key", 3]], [2, 3], [0], 0]]`	`[[[["down", "mod", 0], ["down", "key", 2], ["down", "key", 3]], [2, 3], [0], 0], [[["down", "mod", 0], ["down", "key", 2], ["down", "key", 3]], [2, 3], [0], 0]]`	Failed

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