No way to finish a scan early: stopping took 7 rapid "Can't get there" taps, each silently setting ends #82

There is no control to end a scan early. To stop, the tester tapped "Can't get there" 7 times in about 2.5 s. Each new card's button appeared under the same finger, and each tap silently skipped a task or set a wall end.

Seen in. Device field test of TestFlight build 4.1 (beta at 45017ba), iPhone 14 without LiDAR, iOS 26.6.2, 2026-09-26. Run 3 (a real house): decision at 1:30, taps at 1:34.0–1:36.5 in the recording. Report IDs A41-2055-05 and A41-2055-06 in run3-2055.md.

What happens. After 73 s stuck on the first task, the tester said "I'm just gonna end the test here." (1:30). No control does that. From 1:34.0 to 1:36.5 they tapped "Can't get there" at the same place on the screen ("Can't get there. Can't get there. Can't get there. Can't get there. Can't get there. Done."). Each tap resolved one card, and the next card's button appeared under the finger within 0.2–0.5 s:

1. Tilt down at the meter: skipped.
2. "Walk slowly to your left": the left end was set, unexplored, at 13 ft 2 in left.
3. "Walk slowly to your right": the right end was set, unexplored, at 1 ft 9 in right.
4. Overhead: skipped.
5. Tilt down at 8 ft 9 in left: skipped.
6. Tilt down at 12 ft left: skipped.
7. Tilt down at 5 ft 6 in left: skipped.

Then came "That's the whole wall", "Done with this wall", "Looks complete", the server request, "I can't get there" and the result. The scan's wall is a 14.9 ft stretch nobody walked, and the server still gave it a spot (see "An unwalked, tapped wall still gets a spot (here inside the house) with wall backing and cable route passing"). The left end is also 13 ft from anywhere the phone went (see "Wall ends still land in the wrong place: at the meter on a short side, or 13 ft from where the phone went").

Cause.

• "Done with this wall" (the .finish controls) only appears once both ends are marked (WallWalkScreen.swift#L113-L122, #L149-L151). Before that, the only way forward is to resolve each card.
• Every walk, aim and tilt card carries the same "Can't get there" reply in the same place on the instruction card (WallWalkScreen.swift#L264-L288). Nothing locks input when the card changes.
• On a walk card, cannotAccessArea calls endWalkCannotGoOn, which writes an unexplored end without asking (ScanEngine+Actions.swift#L341-L379, ScanEngine+Ends.swift#L83-L87). Refusing both walks in a row sets both ends.

Fix direction.

• Add an explicit "Finish scan" in a menu, behind a confirm, so testers and homeowners don't have to abuse "Can't get there".
• Refusing both walk directions (or several refusals within a few seconds) is a strong signal: ask "End the scan here?" instead of silently writing two ends.
• Lock the reply button for about 0.6 s when the card changes, or move or animate it, so taps can't chain across cards.

Related.

• "Can't get there" during the walk can put the wall's end at the meter, and the rest of the walk is dropped #24.
• New issues "An unwalked, tapped wall still gets a spot (here inside the house) with wall backing and cable route passing", "Wall ends still land in the wrong place: at the meter on a short side, or 13 ft from where the phone went", and "The first "Tilt down… at your meter" task blocked the start in all three runs: no timeout, and the two-spots rule is never explained".
• Report IDs A41-2055-05 and A41-2055-06.

Screen recordings are in the comment below.