No irreversible commit during the discrimination window

What it is

The span from contact to unique recognition is the disambiguation window. Preview is allowed there—the list may follow, a swipe may reveal an action tint, a long-press ring may fill—but irreversible effects must not commit: archive, send, purchase, delete, or navigate away. Previews rewind; commits do not. The model may change only after the gesture is established.

Why it happens

During the window a recognizer holds a hypothesis, not a fact. If a later feature overturns it (the swipe-to-archive was actually a vertical scroll), an already-fired network call, a pushed page, or a finished “deleted” toast is a bad ledger. Split the effect: the presentation layer may track the finger; the model waits for recognized or an equivalent success. Mail clients that paint an archive ribbon and move the row only after a threshold at lift-off follow that split; firing the archive API on the first horizontal pixel treats the hypothesis as fact.

Studying it

Inject paths that start horizontal then go vertical, or rest then move, and count irreversible side effects that landed before the path was rewritten. Measures include premature commits, the fraction that needed undo, and whether undo still arrived in time. The factor is which lifecycle stage binds the commit (began / changed / ended). Do not ask only whether it “felt smooth”—a smooth preview can already have written the store.

Where it stops holding

View-only scrolling is usually a reversible transform and may follow the finger in the window. Payments, credential submit, and permission grants have no safe preview; they should not be gesture outcomes at all during discrimination. If the system leaves the page before the app sees ended (a back gesture), delayed commit at the app layer cannot help. A short window is not a license to write the model early.

Applying it

• Split gesture callbacks into preview and commit; hang delete, send, and purchase only on successful recognition plus lift-off (or an explicit commit threshold).
• Previews must snap back on failure or reclassification, leaving no debris.
• Drive a scripted “horizontal then vertical” stroke and assert zero archives, navigations, or writes before the reclassify.

Related

• Same group: C3.19.1 Multiple gestures compete for the same onset · C3.19.2 Disambiguation order by direction, speed, finger count, and duration · C3.19.4 Touch-ownership rules for nested scrollers
• Adjacent: C3.33 Gesture undoability · C3.17 Swipe actions
• Search: disambiguation window · speculative update · gesture commit