Symptom

On a fresh iOS install, the PIN-entry screen shown during FTUE rendered the input field as an effectively invisible rectangle inside the Card. Users couldn’t see they needed to tap there to enter the PIN to join the cluster — the screen looked like just a title, a description, and a Connect button (which was disabled until 4 digits were typed, completing the dead end).

Root cause

composeApp/.../startup/PinEntryScreen.kt rendered an OutlinedTextField with three properties that combined to make the field invisible against the iOS Material light theme:

1. No label. Without a label, an empty OutlinedTextField shows literally nothing inside the rectangle — no floating label, no in-field hint.
2. No placeholder. Same effect; nothing tells the user the field expects input.
3. Heavily de-saturated container (unfocusedContainerColor = surfaceVariant.copy(alpha = 0.15f)) and no border-color override. The default OutlinedTextField unfocused border uses colorScheme.outlineVariant, which is intentionally subtle. On iOS’ Material light scheme that pale grey vanishes against the white Card surface, leaving nothing visible at all.

The bug was described as iOS-specific in the report, but the same composable serves desktop and Android — every target was missing the affordance; iOS just exposed it most starkly because of the lighter default surface.

Fix

• composeApp/.../startup/PinEntryScreen.kt — added label = { Text("PIN") } (the discoverability affordance: shows inside the field when empty, floats up when focused), set unfocusedBorderColor = MaterialTheme.colorScheme.outline (replaces outlineVariant so the border is always visible regardless of theme/background contrast), and focusedBorderColor = MaterialTheme.colorScheme.primary for the standard “yes, you’re typing here” feedback. Container alpha left as-is.
• composeApp/src/desktopTest/.../screenshot/Scenarios.kt — three new Roborazzi screenshot scenarios (ftue__pin-entry__light, ftue__pin-entry__dark, ftue__pin-entry__light__error) that render the real PinEntryScreen composable. Compile-time guard + visual-diff artifact for any future visibility regression.
• No @BeforeEach setup, no delay, no real filesystem — pure setContent { ... } calls per the workflow rule shipped in Sautner-Studio-LLC/krill-agents#3.

Prevention

• OutlinedTextField without a label AND without a placeholder is almost always a bug. Either is a usability affordance; both missing is a hidden field. If someone really wants a label-less field (rare — it’s typically a single-cell PIN box, not a form field), they should at minimum override unfocusedBorderColor to something with adequate contrast against the parent surface.
• Don’t trust default outlineVariant. Material 3 deliberately subordinates outlineVariant to other foreground content; on light themes it can be near-invisible against surface / surfaceContainer. Form fields that are the primary call-to-action on a screen (like FTUE) should set unfocusedBorderColor = colorScheme.outline (one notch up in contrast) at minimum.
• First-run / FTUE screens deserve a screenshot scenario per theme. They’re the most-broken screens (least exercised in dev, most consequential in field), and a single “render and dump PNG” test catches “is the affordance there at all” without needing real iOS hardware. Added three for PinEntryScreen here; do the same for any new FTUE-tier screen.
• No CI gate added. A lint that scans for OutlinedTextField { without a label = argument would have caught this, but the false-positive rate would be high (legitimate uses exist) and the population of FTUE screens is small. Relying on the screenshot scenarios + the prevention rule above instead.