Hug the content in every iOS content-fit sheet

[swedishfrenchpress]

The bug

The zero-balance Send sheet and the Add Mint sheet opened at ~70% of the screen with their content floating in a large void. Android's equivalents hug their content — UnifiedSendScreen.kt even says so: "Compact (no fillMaxHeight) so the sheet hugs this empty state."

before (556566f)	after (601e7e7)
592pt — cluster centered in a void	347pt — hugs its content

Root cause, part 1: a measurement loop

Every partial-height sheet derives its detent from a height measured inside that same sheet:

measured height → detent → sheet height → height proposed back to the content

Because the chrome allowance nearly matched the real chrome, the loop was neutrally stable: it settled wherever the first layout pass left it — roughly full-screen, during the presentation transition — and never recovered.

A ScrollView proposes nil height to its content, so a view measured inside one always reports its ideal size regardless of how tall the sheet currently is. That breaks the loop, and it predicted exactly which sheets were broken, 5/5:

Site	Measured	Status
SendView.inputForm	inner VStack in a ScrollView	fine
ReceiveView.inputForm	inner VStack in a ScrollView	fine
ConnectMintPicker	inner VStack in a ScrollView	fine
SendView.noBalanceState	bare NativeEmptyState	latched
AddMintFormView	bare VStack	latched

Root cause, part 2: a detent race

Breaking the loop is necessary but not sufficient, and this one only showed up under the matched capture — manual testing won the race and looked fine.

The body's height is reported more than once as layout settles. Handing presentationDetents a fresh single-element set does not move the sheet: UIKit resolves the new set but keeps whichever detent it had already selected, so a transient measurement wins and the final one is silently ignored. Instrumented on an iPhone 17 Pro:

[CFS] measured=0    → detent 298   (first-frame estimate)
[CFS] measured=469  → detent 547   ← transient, and what the sheet stayed on
[CFS] measured=241  → detent 319   ← correct, silently ignored

All three within 70ms. Binding the selection alongside the set fixes it — the sheet is told which detent to be on, not merely which ones exist.

The change

Four hand-rolled copies of the mechanism collapse into one pair of modifiers:

.contentFitMeasured { ... }   // inside the NavigationStack — owns the ScrollView + measurement
.contentFitDetent(height)     // on the sheet root — owns the arithmetic and the selection

ContentFitSheetMetrics is the single place the arithmetic lives:

detent = content + navigationBar (44, when present) + bottomSafeArea,  clamped to 0.9 × screen

Notably absent: any allowance for the drag indicator. presentationDragIndicator draws the grabber as an overlay over the content's own top padding, so reserving height for it never moved the content down — it landed as dead space at the bottom. The old flat 108 carried 20pt of that plus 10pt of slack; removing both tightens every sheet by 30pt.

The bottom safe area is resolved per device rather than assumed, so home-button iPhones no longer over-shoot by 34pt. The clamp means accessibility text sizes scroll inside the sheet rather than silently pinning it full-height.

Onboarding's "What is ecash?" sheet

Joined to the same mechanism for consistency. It hosts no NavigationStack, hence the navigationBar: flag. It loses its second .large detent — the ScrollView and the clamp cover the large-text case that detent existed for, and every other content-fit sheet is single-detent.

before	after
~391pt	~397pt

This one is essentially unchanged in size, and slightly taller by design: the old detent was the measured content with no chrome at all, so the sheet borrowed the home-indicator strip. It now accounts for it.

Capture conditions

Both sides built from isolated worktrees with separate Derived Data, captured on one simulator instance.

• base 556566f (upstream/main) · head 601e7e7
• iOS 26.5 (23F77), iPhone 17 Pro, 1206×2622 @3x (402×874pt)
• Xcode 26.6 (17F113)
• light appearance, en_US, default Dynamic Type, status bar pinned to 9:41
• fixture: RESET_WALLET + UITEST_SEED_WALLET + UITEST_SEED_MINT with a synthetic mint URL (https://mint.example.test) — no network, no real wallet data

Not captured in the matched run: Add Mint, Receive, and the connect-a-mint picker. They go through the identical code path and were checked by hand, but they do not have before/after evidence here.

No Android changes. No project.pbxproj changes.

🤖 Generated with Claude Code