Cards open to be read — the mobile detail screen turns read-only, editing moves behind a transactional Save

CardDetailScreen renders title, inline-Markdown body, and a quiet dates
footer; all writing moves to the new CardEditScreen, a full-screen cover
with segmented Details/Body panes. Drafts commit in one perform bracket
on Save only — Cancel guards dirty drafts with a discard confirmation,
and a failed write keeps the sheet and its drafts and raises an alert
instead of dismissing. CardAttributesSection becomes a pure
binding-driven editor with no write path of its own. The UI test walk
crosses the new split, with body-pane and discard coverage, and a
deterministic replaceAllText helper retires the flaky ⌘A select-all.

Claude-Session: https://claude.ai/code/session_01SR4XGjmBE16ZUYWpfFHXwY

KanbanMobile/CHANGELOG.md

@@ -1,5 +1,9 @@
 **August 2026**
 
+Tapping a card now shows a readable view of its title and text with formatting, instead of dropping straight into the editor.
+
+Editing a card happens on its own screen with Details and Body sections, and changes apply only when you tap Save.
+
 Press and hold a lane or card to drag it into a new order.
 
 Settings now lives behind the gear button on the board list instead of a separate tab, so boards fill the whole screen.

KanbanMobile/Screens/CardAttributesSection.swift

@@ -1,9 +1,14 @@
 import SwiftUI
 
-/// The card detail screen's Attributes section: icon, icon colour, and background colour — the
+/// The card editor's Attributes section: icon, icon colour, and background colour — the three
-/// three *typed* style fields a card carries (`FrontmatterFields.icon`/`.iconColor`/`.background`).
+/// *typed* style fields a card carries (`FrontmatterFields.icon`/`.iconColor`/`.background`).
-/// Every pick writes immediately through `BoardWriter.updateIndex` — these are one-tap choices
+///
-/// from a fixed set, not free text, so there is no draft to debounce the way title/body have.
+/// **Drafted, not written.** Every pick here mutates a `Binding<String?>` the caller owns —
+/// `CardEditScreen`'s own `@State` drafts — rather than reaching for `BoardWriter` itself: the
+/// transactional edit model commits title, body, and these three keys together in one `Save`, so
+/// this section has no session, no card, and no write code of its own. It is a pure "edit these
+/// three bindings" view; the icon picker sheet is unchanged mechanically, it just feeds a binding
+/// instead of firing a write.
 ///
 /// **There is no labels row.** `labels` is not a field either `BoardModel` or `FrontmatterDocument`
 /// exposes as typed: `BoardModel.document`'s own doc comment names it as one of the reserved keys
@@ -13,10 +18,9 @@ import SwiftUI
 /// surgical edits exist to keep (agent-written or hand-written overlays round-trip untouched). If
 /// a typed `labels` field is ever added to the storage schema, its editor belongs in this section.
 struct CardAttributesSection: View {
-    let card: Card
+    @Binding var icon: String?
-    let laneID: ItemID
+    @Binding var iconColor: String?
-    let cardID: ItemID
+    @Binding var background: String?
-    let session: BoardSession
 
     @State private var isPresentingIconPicker = false
 
@@ -26,7 +30,7 @@ struct CardAttributesSection: View {
                 isPresentingIconPicker = true
             } label: {
                 LabeledContent("Icon") {
-                    if let icon = card.icon.value, !icon.isEmpty {
+                    if let icon, !icon.isEmpty {
                         Image(systemName: icon)
                     } else {
                         Text("None").foregroundStyle(.secondary)
@@ -35,17 +39,17 @@ struct CardAttributesSection: View {
             }
             .tint(.primary)
 
-            swatchRow(title: "Icon Color", swatches: CardPalette.foregrounds, current: card.iconColor.value) { name in
+            swatchRow(title: "Icon Color", swatches: CardPalette.foregrounds, current: iconColor) { name in
-                setStyle(FrontmatterKeys.iconColor, to: name)
+                iconColor = name
             }
 
-            swatchRow(title: "Background", swatches: CardPalette.backgrounds, current: card.background.value) { name in
+            swatchRow(title: "Background", swatches: CardPalette.backgrounds, current: background) { name in
-                setStyle(FrontmatterKeys.background, to: name)
+                background = name
             }
         }
         .sheet(isPresented: $isPresentingIconPicker) {
-            IconPickerSheet(current: card.icon.value) { name in
+            IconPickerSheet(current: icon) { name in
-                setStyle(FrontmatterKeys.icon, to: name)
+                icon = name
             }
         }
     }
@@ -77,28 +81,6 @@ struct CardAttributesSection: View {
         }
         .padding(.vertical, 4)
     }
-
-    /// Writes one style key immediately. `operation: .style` is the vocabulary's own case for
-    /// "`updateIndex` on behalf of styling flows" (`WriteOperation.style`); `card.title.value` is
-    /// read before the closure runs so a failure banner can still name the card by the title on
-    /// screen.
-    private func setStyle(_ key: String, to value: String?) {
-        let laneID = self.laneID
-        let cardID = self.cardID
-        let cardTitle = card.title.value
-        Task {
-            // The closure's throws type must be spelled out — a trailing closure literal does not
-            // pick up `perform`'s `throws(BoardWriteError)` from context alone.
-            await session.perform { (root: URL) throws(BoardWriteError) -> Void in
-                let folder = root
-                    .appendingPathComponent(laneID.rawValue, isDirectory: true)
-                    .appendingPathComponent(cardID.rawValue, isDirectory: true)
-                try BoardWriter.updateIndex(inItemFolder: folder, operation: .style(title: cardTitle)) { document in
-                    document.setStyleValue(value, for: key)
-                }
-            }
-        }
-    }
 }
 
 /// One colour well: a filled circle, a slashed placeholder for "None", and a selection ring.

KanbanMobile/Screens/CardDetailScreen.swift

@@ -1,22 +1,17 @@
 import SwiftUI
 
-/// The card editor — title, body, and attributes — `BoardRoute.card`'s destination.
+/// The card's read-only view — `BoardRoute.card`'s destination.
 ///
 /// Holds board-relative IDs only, never a `Card` value: every body evaluation re-reads the card
-/// from `session.snapshot`, so a write this screen makes (or one that lands from elsewhere while
+/// from `session.snapshot`, so a write this screen's own edit sheet makes (or one that lands from
-/// it's open) is reflected the moment the session's reload lands, and a card trashed on another
+/// elsewhere while it's open) is reflected the moment the session's reload lands, and a card
-/// device is noticed rather than edited into thin air.
+/// trashed on another device is noticed rather than shown stale.
 ///
-/// ### Save timing
+/// **Read-only, by design.** There is no draft here and nothing this screen ever writes — editing
-///
+/// lives entirely in `CardEditScreen`, presented full-screen from the Edit button. That split is
-/// Title and body are edited into local `@State` drafts and committed through `BoardWriter` only
+/// the whole point of the transactional model: a screen that only ever renders `session.snapshot`
-/// when they differ from the snapshot's own value — never on every keystroke. Three triggers cover
+/// cannot itself go stale relative to disk, and there is no auto-save timing to reason about
-/// every way editing can end without dropping a change: the field's own submit (title, on Return),
+/// because there is no save at all on this side of the Edit button.
-/// `onDisappear` (the user navigates back), and `scenePhase` leaving `.active` (the user backgrounds
-/// the app, or is interrupted, mid-edit in the body editor). A `Done` toolbar button folds in the
-/// same commit and drops focus, for a user who wants an explicit "I'm finished" without leaving the
-/// screen. All four funnel through `commitAll()`, so there is exactly one place that decides what
-/// "changed" means for each field.
 struct CardDetailScreen: View {
     let boardRoot: URL
     let laneID: ItemID
@@ -24,11 +19,8 @@ struct CardDetailScreen: View {
 
     @Environment(BoardIndexStore.self) private var index
     @Environment(\.dismiss) private var dismiss
-    @Environment(\.scenePhase) private var scenePhase
 
-    @State private var titleDraft = ""
+    @State private var isPresentingEdit = false
-    @State private var bodyDraft = ""
-    @FocusState private var isBodyFocused: Bool
 
     private var session: BoardSession { index.session(forBoardAt: boardRoot) }
 
@@ -41,58 +33,35 @@ struct CardDetailScreen: View {
             .navigationTitle("Card")
             .navigationBarTitleDisplayMode(.inline)
             .toolbar {
-                ToolbarItem(placement: .confirmationAction) {
+                if card != nil {
-                    Button("Done") {
+                    ToolbarItem(placement: .primaryAction) {
-                        isBodyFocused = false
+                        Button("Edit") { isPresentingEdit = true }
-                        commitAll()
                     }
                 }
             }
             .task { session.open() }
-            // Seeds the drafts once per card. `.task(id:)` re-runs only when `card?.id` changes —
+            .fullScreenCover(isPresented: $isPresentingEdit) {
-            // nil while the session is still opening, then the card's own id once it lands — so a
+                CardEditScreen(boardRoot: boardRoot, laneID: laneID, cardID: cardID)
-            // reload that lands *while this screen is open* (including the reload this screen's
-            // own commit triggers) never clobbers text the user is mid-typing.
-            .task(id: card?.id) {
-                guard let card else { return }
-                titleDraft = card.title.value ?? ""
-                bodyDraft = card.body
-            }
-            .onDisappear { commitAll() }
-            .onChange(of: scenePhase) { _, newPhase in
-                if newPhase != .active { commitAll() }
             }
     }
 
     @ViewBuilder
     private var content: some View {
         if let card {
-            Form {
+            ScrollView {
+                VStack(alignment: .leading, spacing: 20) {
                     if session.lastError != nil {
-                    Section {
                         Label("Showing the last saved version — a recent update didn't load.", systemImage: "exclamationmark.triangle")
                             .font(.footnote)
                             .foregroundStyle(.secondary)
                     }
-                }
 
-                Section("Title") {
+                    titleBlock(for: card)
-                    TextField("Untitled Card", text: $titleDraft)
+                    bodyBlock(for: card)
-                        .onSubmit { commitTitle(against: card) }
+                    detailsFooter(for: card)
-                }
-
-                Section("Body") {
-                    TextEditor(text: $bodyDraft)
-                        .frame(minHeight: 200)
-                        .focused($isBodyFocused)
-                }
-
-                CardAttributesSection(card: card, laneID: laneID, cardID: cardID, session: session)
-
-                Section("Details") {
-                    LabeledContent("Created", value: card.created.value.map(Self.formatted) ?? "—")
-                    LabeledContent("Modified", value: card.modified.value.map(Self.formatted) ?? "—")
                 }
+                .padding()
+                .frame(maxWidth: .infinity, alignment: .leading)
             }
         } else if case .ready = session.phase {
             ContentUnavailableView("Card Removed", systemImage: "trash", description: Text("This card was deleted."))
@@ -102,56 +71,100 @@ struct CardDetailScreen: View {
         }
     }
 
-    private func commitAll() {
+    /// The title, its icon when the card has one, and a subtle background tint lifted from the
-        guard let card else { return }
+    /// card's own `background` swatch — passive display only, no swatches to tap here. An
-        commitTitle(against: card)
+    /// unrecognized colour name (the same leniency `ItemIconView`/`CardPalette` document for
-        commitBody(against: card)
+    /// themselves) just skips the tint rather than guessing at one.
+    @ViewBuilder
+    private func titleBlock(for card: Card) -> some View {
+        HStack(alignment: .firstTextBaseline, spacing: 10) {
+            ItemIconView(icon: card.icon.value, iconColor: card.iconColor.value)
+            titleText(for: card)
+        }
+        .padding()
+        .frame(maxWidth: .infinity, alignment: .leading)
+        .background(
+            (tintColor(for: card)?.opacity(0.15) ?? Color.clear),
+            in: RoundedRectangle(cornerRadius: 12)
+        )
     }
 
-    private func commitTitle(against card: Card) {
+    @ViewBuilder
-        let trimmed = titleDraft.trimmingCharacters(in: .whitespacesAndNewlines)
+    private func titleText(for card: Card) -> some View {
-        guard trimmed != (card.title.value ?? "") else { return }
+        if let title = card.title.value, !title.isEmpty {
-        let laneID = self.laneID
+            Text(title)
-        let cardID = self.cardID
+                .font(.title.bold())
-        let newValue: String? = trimmed.isEmpty ? nil : trimmed
-        Task {
-            // The closure's throws type must be spelled out — a trailing closure literal does not
-            // pick up `perform`'s `throws(BoardWriteError)` from context alone.
-            await session.perform { (root: URL) throws(BoardWriteError) -> Void in
-                let folder = root
-                    .appendingPathComponent(laneID.rawValue, isDirectory: true)
-                    .appendingPathComponent(cardID.rawValue, isDirectory: true)
-                // The Mac's own rename path, verbatim (`BoardStore.setTitle`): plain `set`/`remove`
-                // — `setStyleValue` is the style gesture's helper, not the title's — and
-                // `.rename(title: nil)` so `updateIndex` enriches the operation from the document
-                // it reads rather than trusting a snapshot that may have aged.
-                try BoardWriter.updateIndex(inItemFolder: folder, operation: .rename(title: nil)) { document in
-                    if let newValue {
-                        document.set(FrontmatterKeys.title, to: .string(newValue))
         } else {
-                        document.remove(FrontmatterKeys.title)
+            Text("Untitled Card")
+                .font(.title.bold())
+                .foregroundStyle(.secondary)
         }
     }
+
+    private func tintColor(for card: Card) -> Color? {
+        card.background.value.flatMap { CardPalette.color(named: $0, in: CardPalette.backgrounds) }
+    }
+
+    /// The body, rendered as Markdown — see `MarkdownBlocks` for why this is a per-paragraph
+    /// `AttributedString(markdown:)` pass rather than a full block parser.
+    @ViewBuilder
+    private func bodyBlock(for card: Card) -> some View {
+        let paragraphs = MarkdownBlocks.paragraphs(in: card.body)
+        if paragraphs.isEmpty {
+            Text("No description")
+                .foregroundStyle(.secondary)
+        } else {
+            VStack(alignment: .leading, spacing: 12) {
+                ForEach(Array(paragraphs.enumerated()), id: \.offset) { _, paragraph in
+                    Text(MarkdownBlocks.rendered(paragraph))
+                }
             }
         }
     }
 
-    private func commitBody(against card: Card) {
+    @ViewBuilder
-        guard bodyDraft != card.body else { return }
+    private func detailsFooter(for card: Card) -> some View {
-        let laneID = self.laneID
+        VStack(alignment: .leading, spacing: 4) {
-        let cardID = self.cardID
+            Text("Created \(card.created.value.map(Self.formatted) ?? "—")")
-        let newBody = bodyDraft
+            Text("Modified \(card.modified.value.map(Self.formatted) ?? "—")")
-        Task {
-            await session.perform { (root: URL) throws(BoardWriteError) -> Bool in
-                let folder = root
-                    .appendingPathComponent(laneID.rawValue, isDirectory: true)
-                    .appendingPathComponent(cardID.rawValue, isDirectory: true)
-                return try BoardWriter.writeBody(inItemFolder: folder, body: newBody)
-            }
         }
+        .font(.footnote)
+        .foregroundStyle(.secondary)
+        .padding(.top, 8)
     }
 
     private static func formatted(_ date: Date) -> String {
         date.formatted(date: .abbreviated, time: .shortened)
     }
 }
+
+/// Dependency-free Markdown rendering for a card body: no `swift-markdown` block parser here, just
+/// `Foundation`'s own `AttributedString(markdown:options:)` run once per paragraph.
+///
+/// **Why per-paragraph.** `AttributedString`'s built-in parser has no "render this as a sequence of
+/// blocks" mode short of `.full`, which produces a block tree this view would still have to walk —
+/// no simpler than doing the walk ourselves, and it collapses the very newlines a card body relies
+/// on to separate paragraphs. Splitting on blank lines first and parsing each paragraph with
+/// `.inlineOnlyPreservingWhitespace` gets both halves of what a card body needs cheaply: inline
+/// emphasis/links/code render as styled runs, and the newlines *inside* a paragraph (soft line
+/// breaks) survive as literal whitespace instead of being folded into a single space.
+enum MarkdownBlocks {
+
+    /// Splits `body` on runs of one or more blank lines — Markdown's own paragraph boundary — and
+    /// trims each block, so a body with trailing blank lines or extra spacing between paragraphs
+    /// doesn't render phantom empty blocks.
+    static func paragraphs(in body: String) -> [String] {
+        body
+            .components(separatedBy: "\n\n")
+            .map { $0.trimmingCharacters(in: .whitespacesAndNewlines) }
+            .filter { !$0.isEmpty }
+    }
+
+    /// One paragraph, inline-parsed. Malformed Markdown (an unterminated code span, say) falls back
+    /// to the raw paragraph text rather than dropping it — the same "never lose the author's text"
+    /// posture `CardPalette.color(named:in:)` takes for an unrecognized colour name.
+    static func rendered(_ paragraph: String) -> AttributedString {
+        let options = AttributedString.MarkdownParsingOptions(interpretedSyntax: .inlineOnlyPreservingWhitespace)
+        return (try? AttributedString(markdown: paragraph, options: options)) ?? AttributedString(paragraph)
+    }
+}

KanbanMobile/Screens/CardEditScreen.swift

@@ -0,0 +1,276 @@
+import SwiftUI
+
+/// The card editor — title, body, and attributes, all drafted and committed together — presented
+/// full-screen from `CardDetailScreen`'s Edit button.
+///
+/// Holds board-relative IDs only, never a `Card` value, for the same reason every other screen in
+/// this stack does: the card is re-read from `session.snapshot` on every body evaluation, so a
+/// write landing from elsewhere while this sheet is open (a trash from another device, say) is
+/// noticed rather than edited into thin air.
+///
+/// ### Transactional, not auto-saving
+///
+/// Every earlier screen in this app commits a field the moment it stops being edited — `onSubmit`,
+/// `onDisappear`, a scene-phase change. This one commits nothing until `Save`, deliberately: a
+/// `fullScreenCover` has no interactive swipe-to-dismiss, so the only way out mid-edit is a button
+/// this screen controls, which makes "ask before discarding" both possible and the more honest
+/// default for a screen with five drafted fields open across two panes at once. There is no
+/// scenePhase or onDisappear commit anywhere below — backgrounding the app or losing focus leaves
+/// the drafts exactly where they were, waiting for `Save` or `Cancel`.
+///
+/// `Cancel` on a clean sheet dismisses immediately; on a dirty one it raises a confirmation before
+/// discarding. `Save` writes every changed field in one `session.perform` bracket — title through
+/// `.rename`, the three style keys through one `.style` call, body through `writeBody` — writes
+/// nothing at all when nothing changed, and dismisses only on success: a failed write keeps the
+/// sheet and its drafts and raises an alert (see `save()`).
+struct CardEditScreen: View {
+    let boardRoot: URL
+    let laneID: ItemID
+    let cardID: ItemID
+
+    @Environment(BoardIndexStore.self) private var index
+    @Environment(\.dismiss) private var dismiss
+
+    private enum Pane: String, CaseIterable, Hashable {
+        case details = "Details"
+        case body = "Body"
+    }
+
+    @State private var pane: Pane = .details
+
+    @State private var titleDraft = ""
+    @State private var bodyDraft = ""
+    @State private var iconDraft: String?
+    @State private var iconColorDraft: String?
+    @State private var backgroundDraft: String?
+    @State private var isConfirmingDiscard = false
+    @State private var saveError: BoardSessionError?
+    @FocusState private var isBodyFocused: Bool
+
+    private var session: BoardSession { index.session(forBoardAt: boardRoot) }
+
+    private var card: Card? {
+        session.snapshot?.lanes.first { $0.id == laneID }?.cards.first { $0.id == cardID }
+    }
+
+    var body: some View {
+        NavigationStack {
+            content
+                .navigationTitle("Card")
+                .navigationBarTitleDisplayMode(.inline)
+                .toolbar {
+                    ToolbarItem(placement: .cancellationAction) {
+                        Button("Cancel") { requestDismiss() }
+                    }
+                    if card != nil {
+                        ToolbarItem(placement: .principal) {
+                            Picker("Pane", selection: $pane) {
+                                ForEach(Pane.allCases, id: \.self) { pane in
+                                    Text(pane.rawValue).tag(pane)
+                                }
+                            }
+                            .pickerStyle(.segmented)
+                            .frame(maxWidth: 220)
+                        }
+                        ToolbarItem(placement: .confirmationAction) {
+                            Button("Save") { save() }
+                        }
+                    }
+                }
+                .task { session.open() }
+                // Seeds the drafts once per card. `.task(id:)` re-runs only when `card?.id`
+                // changes — nil while the session is still opening, then the card's own id once
+                // it lands — so a reload that lands *while this sheet is open* never clobbers a
+                // draft the user is mid-typing. Unlike the old in-place editor, nothing this
+                // screen does triggers such a reload before `Save` — but another device's write
+                // can still land, and the same guard covers that case too.
+                .task(id: card?.id) {
+                    guard let card else { return }
+                    titleDraft = card.title.value ?? ""
+                    bodyDraft = card.body
+                    iconDraft = card.icon.value
+                    iconColorDraft = card.iconColor.value
+                    backgroundDraft = card.background.value
+                }
+                .confirmationDialog(
+                    "Discard Changes?",
+                    isPresented: $isConfirmingDiscard,
+                    titleVisibility: .visible
+                ) {
+                    Button("Discard", role: .destructive) { dismiss() }
+                    Button("Cancel", role: .cancel) {}
+                }
+                .alert(
+                    "Couldn't Save",
+                    isPresented: Binding(get: { saveError != nil }, set: { if !$0 { saveError = nil } }),
+                    presenting: saveError
+                ) { _ in
+                    Button("OK") { saveError = nil }
+                } message: { error in
+                    Text(error.description)
+                }
+        }
+    }
+
+    @ViewBuilder
+    private var content: some View {
+        if let card {
+            switch pane {
+            case .details:
+                detailsForm(for: card)
+            case .body:
+                TextEditor(text: $bodyDraft)
+                    .focused($isBodyFocused)
+                    .padding(.horizontal, 12)
+                    .padding(.top, 8)
+            }
+        } else if case .ready = session.phase {
+            // The card is gone from a `.ready` snapshot — deleted elsewhere while this sheet was
+            // open. There is nothing left to edit; dismiss the cover rather than leave drafts for
+            // a card that no longer exists.
+            ContentUnavailableView("Card Removed", systemImage: "trash", description: Text("This card was deleted."))
+                .task { dismiss() }
+        } else {
+            ProgressView("Opening card")
+        }
+    }
+
+    @ViewBuilder
+    private func detailsForm(for card: Card) -> some View {
+        Form {
+            if session.lastError != nil {
+                Section {
+                    Label("Showing the last saved version — a recent update didn't load.", systemImage: "exclamationmark.triangle")
+                        .font(.footnote)
+                        .foregroundStyle(.secondary)
+                }
+            }
+
+            Section("Title") {
+                TextField("Untitled Card", text: $titleDraft)
+            }
+
+            CardAttributesSection(icon: $iconDraft, iconColor: $iconColorDraft, background: $backgroundDraft)
+
+            Section("Details") {
+                LabeledContent("Created", value: card.created.value.map(Self.formatted) ?? "—")
+                LabeledContent("Modified", value: card.modified.value.map(Self.formatted) ?? "—")
+            }
+        }
+    }
+
+    /// Any draft differing from the card's own current snapshot value — title compared trimmed,
+    /// exactly as `Save` compares it, so this predicate and the write it gates never disagree.
+    private var isDirty: Bool {
+        guard let card else { return false }
+        let trimmedTitle = titleDraft.trimmingCharacters(in: .whitespacesAndNewlines)
+        return trimmedTitle != (card.title.value ?? "")
+            || bodyDraft != card.body
+            || iconDraft != card.icon.value
+            || iconColorDraft != card.iconColor.value
+            || backgroundDraft != card.background.value
+    }
+
+    private func requestDismiss() {
+        if isDirty {
+            isConfirmingDiscard = true
+        } else {
+            dismiss()
+        }
+    }
+
+    /// One `session.perform` bracket, three independent writes inside it gated on whatever
+    /// actually changed — a clean `Save` (nothing dirty) makes no write at all and just dismisses.
+    /// Awaits the perform before dismissing: `perform` already awaits its own reload, so by the
+    /// time this returns `CardDetailScreen`'s snapshot underneath already reflects the write, and
+    /// the read screen shows the new values the instant the cover animates away.
+    ///
+    /// Dismissal is gated on the perform's own `Result` — the one caller of `perform` in this app
+    /// that can't ignore it. The auto-committing screens could fire and forget because their
+    /// drafts outlived the write attempt; here dismissing *is* draft destruction, so a failed
+    /// write keeps the sheet (and every draft) exactly where it was and raises an alert instead.
+    /// `perform` reloads even on failure, so a partially-applied multi-call write (title landed,
+    /// body didn't) re-seeds nothing — the drafts keep the user's full intent and a retry rewrites
+    /// only what still differs.
+    private func save() {
+        guard let card else {
+            dismiss()
+            return
+        }
+
+        let trimmedTitle = titleDraft.trimmingCharacters(in: .whitespacesAndNewlines)
+        let titleChanged = trimmedTitle != (card.title.value ?? "")
+        let newTitle: String? = trimmedTitle.isEmpty ? nil : trimmedTitle
+
+        let iconChanged = iconDraft != card.icon.value
+        let iconColorChanged = iconColorDraft != card.iconColor.value
+        let backgroundChanged = backgroundDraft != card.background.value
+        let styleChanged = iconChanged || iconColorChanged || backgroundChanged
+
+        let bodyChanged = bodyDraft != card.body
+
+        guard titleChanged || styleChanged || bodyChanged else {
+            dismiss()
+            return
+        }
+
+        let laneID = self.laneID
+        let cardID = self.cardID
+        let cardTitle = card.title.value
+        let newIcon = iconDraft
+        let newIconColor = iconColorDraft
+        let newBackground = backgroundDraft
+        let newBody = bodyDraft
+
+        Task {
+            // The closure's throws type must be spelled out — a trailing closure literal does not
+            // pick up `perform`'s `throws(BoardWriteError)` from context alone.
+            let outcome = await session.perform { (root: URL) throws(BoardWriteError) -> Void in
+                let folder = root
+                    .appendingPathComponent(laneID.rawValue, isDirectory: true)
+                    .appendingPathComponent(cardID.rawValue, isDirectory: true)
+
+                if titleChanged {
+                    // The Mac's own rename path, verbatim (`BoardStore.setTitle`): plain
+                    // `set`/`remove` — `setStyleValue` is the style gesture's helper, not the
+                    // title's — and `.rename(title: nil)` so `updateIndex` enriches the operation
+                    // from the document it reads rather than trusting a snapshot that may have
+                    // aged.
+                    try BoardWriter.updateIndex(inItemFolder: folder, operation: .rename(title: nil)) { document in
+                        if let newTitle {
+                            document.set(FrontmatterKeys.title, to: .string(newTitle))
+                        } else {
+                            document.remove(FrontmatterKeys.title)
+                        }
+                    }
+                }
+
+                if styleChanged {
+                    // One `.style` call for all three keys — `operation: .style` is the
+                    // vocabulary's own case for "`updateIndex` on behalf of styling flows"
+                    // (`WriteOperation.style`), and each changed key writes through
+                    // `setStyleValue` exactly as the old immediate-write attributes section did.
+                    try BoardWriter.updateIndex(inItemFolder: folder, operation: .style(title: cardTitle)) { document in
+                        if iconChanged { document.setStyleValue(newIcon, for: FrontmatterKeys.icon) }
+                        if iconColorChanged { document.setStyleValue(newIconColor, for: FrontmatterKeys.iconColor) }
+                        if backgroundChanged { document.setStyleValue(newBackground, for: FrontmatterKeys.background) }
+                    }
+                }
+
+                if bodyChanged {
+                    _ = try BoardWriter.writeBody(inItemFolder: folder, body: newBody)
+                }
+            }
+            switch outcome {
+            case .success:
+                dismiss()
+            case let .failure(error):
+                saveError = error
+            }
+        }
+    }
+
+    private static func formatted(_ date: Date) -> String {
+        date.formatted(date: .abbreviated, time: .shortened)
+    }
+}

KanbanMobileUITests/BoardsNavigationUITests.swift

@@ -1,43 +1,31 @@
 import XCTest
 
 /// Board list → lanes → cards → card detail, then an edit that has to reach disk — the one
-/// end-to-end walk of the mobile MVP's navigation stack (`BoardRoute`'s three destinations).
+/// end-to-end walk of the mobile MVP's navigation stack (`BoardRoute`'s three destinations), plus
+/// the transactional edit sheet `CardDetailScreen`'s Edit button presents.
 final class BoardsNavigationUITests: XCTestCase {
 
     @MainActor
     func testBoardsNavigationAndTitleEdit() throws {
         let (app, root) = XCUIApplication.launchedWithFixtureBoard()
+        app.navigateToFirstCard()
 
-        // Boards is the app's root screen (`BoardsTabView`), so no navigation is needed to reach
+        // CardDetailScreen is read-only: the fixture card's title renders as plain text, not a
-        // it. The row's label is the flattened `BoardSummaryRow` — title plus the "N lanes · N
+        // field — the read/edit split this suite now has to cross to reach any field at all.
-        // cards · modified" subtitle `BoardIndexStore`'s first scan fills in.
-        let boardRow = app.element(labelContaining: RichBoard.title)
         XCTAssertTrue(
-            boardRow.waitForExistence(timeout: XCUIApplication.uiTimeout),
+            app.staticTexts[RichBoard.firstLaneFirstCard].waitForExistence(timeout: XCUIApplication.uiTimeout),
-            "the \"\(RichBoard.title)\" row never appeared — check the fixture copy or the first scan"
+            "the read view's title text never appeared"
         )
-        boardRow.tap()
 
-        let laneRow = app.element(labelContaining: RichBoard.firstLane)
+        app.openCardEdit()
-        XCTAssertTrue(
-            laneRow.waitForExistence(timeout: XCUIApplication.uiTimeout),
-            "the \"\(RichBoard.firstLane)\" lane row never appeared"
-        )
-        laneRow.tap()
 
-        let cardRow = app.element(labelContaining: RichBoard.firstLaneFirstCard)
+        // CardEditScreen opens on the Details pane; its only textField is the title
-        XCTAssertTrue(
+        // (`Section("Title")`) — the body pane is a bare `TextEditor`, a `textView`, and is not
-            cardRow.waitForExistence(timeout: XCUIApplication.uiTimeout),
+        // this pane's concern.
-            "the \"\(RichBoard.firstLaneFirstCard)\" card row never appeared"
-        )
-        cardRow.tap()
-
-        // CardDetailScreen: the only `textField` on this screen is the title
-        // (`Section("Title")`) — the body is a `TextEditor`, which is a `textView`.
         let titleField = app.textFields.firstMatch
         XCTAssertTrue(
             titleField.waitForExistence(timeout: XCUIApplication.uiTimeout),
-            "CardDetailScreen's title field never appeared"
+            "CardEditScreen's title field never appeared"
         )
         XCTAssertEqual(
             titleField.value as? String, RichBoard.firstLaneFirstCard,
@@ -45,21 +33,133 @@ final class BoardsNavigationUITests: XCTestCase {
         )
 
         let sentinel = "Retitled by UI test"
-        titleField.tap()
+        titleField.replaceAllText(with: sentinel)
-        // Select-all via a hardware-keyboard shortcut (iOS answers ⌘A the same as macOS when a
-        // keyboard is attached, which the Simulator always presents one as) rather than a
-        // backspace-per-character workaround, whose delete count only works if the tap happened
-        // to land the cursor at the end of the existing text.
-        titleField.typeKey("a", modifierFlags: .command)
-        titleField.typeText(sentinel)
 
-        // Commit the way the screen commits (`CardDetailScreen.body`'s `.confirmationAction`):
+        app.navigationBars.buttons["Save"].tap()
-        // the Done button folds `commitAll()` in and drops focus, without navigating back.
-        app.navigationBars.buttons["Done"].tap()
 
+        // The cover dismisses back to the read view underneath, which should already show the new
+        // title — `session.perform` awaits its own reload before `Save` dismisses.
+        XCTAssertTrue(
+            app.staticTexts[sentinel].waitForExistence(timeout: XCUIApplication.uiTimeout),
+            "the read view never picked up the retitled card"
+        )
         XCTAssertTrue(
             waitForFile(under: root, containing: sentinel),
             "the retitled card never landed on disk under \(root.path)"
         )
     }
+
+    @MainActor
+    func testCardEditBodyPaneWritesToDisk() throws {
+        let (app, root) = XCUIApplication.launchedWithFixtureBoard()
+        app.navigateToFirstCard()
+        app.openCardEdit()
+
+        app.buttons["Body"].tap()
+
+        let bodyEditor = app.textViews.firstMatch
+        XCTAssertTrue(
+            bodyEditor.waitForExistence(timeout: XCUIApplication.uiTimeout),
+            "the Body pane's text editor never appeared"
+        )
+
+        let sentinel = "Rewritten body by UI test"
+        bodyEditor.replaceAllText(with: sentinel)
+
+        app.navigationBars.buttons["Save"].tap()
+
+        // The read view renders the body as Markdown; a plain sentinel with no markup renders
+        // back out as itself.
+        XCTAssertTrue(
+            app.staticTexts[sentinel].waitForExistence(timeout: XCUIApplication.uiTimeout),
+            "the read view never picked up the rewritten body"
+        )
+        XCTAssertTrue(
+            waitForFile(under: root, containing: sentinel),
+            "the rewritten body never landed on disk under \(root.path)"
+        )
+    }
+
+    @MainActor
+    func testCardEditCancelWithDirtyDraftsDiscardsOnDisk() throws {
+        let (app, root) = XCUIApplication.launchedWithFixtureBoard()
+        app.navigateToFirstCard()
+        app.openCardEdit()
+
+        let titleField = app.textFields.firstMatch
+        XCTAssertTrue(
+            titleField.waitForExistence(timeout: XCUIApplication.uiTimeout),
+            "CardEditScreen's title field never appeared"
+        )
+
+        let sentinel = "Abandoned edit"
+        titleField.replaceAllText(with: sentinel)
+
+        // Cancel on a dirty sheet raises a confirmation rather than dismissing outright — the
+        // sheet's only exit, since a `fullScreenCover` has no interactive swipe-dismiss.
+        app.navigationBars.buttons["Cancel"].tap()
+
+        let discardButton = app.buttons["Discard"]
+        XCTAssertTrue(
+            discardButton.waitForExistence(timeout: XCUIApplication.uiTimeout),
+            "the discard confirmation never appeared for a dirty Cancel"
+        )
+        discardButton.tap()
+
+        // Back on the read view, still showing the fixture's own title — nothing was ever written.
+        XCTAssertTrue(
+            app.staticTexts[RichBoard.firstLaneFirstCard].waitForExistence(timeout: XCUIApplication.uiTimeout),
+            "the read view did not return to the card's original title after Discard"
+        )
+        XCTAssertTrue(
+            fileDoesNotContain(under: root, substring: sentinel),
+            "the discarded title leaked onto disk under \(root.path)"
+        )
+    }
+}
+
+private extension XCUIApplication {
+
+    /// Boards → the fixture's first lane → its first card, landing on `CardDetailScreen`'s read
+    /// view. Shared by every test in this file so the navigation-and-assert boilerplate is written
+    /// once.
+    @MainActor
+    func navigateToFirstCard() {
+        let boardRow = element(labelContaining: RichBoard.title)
+        XCTAssertTrue(
+            boardRow.waitForExistence(timeout: XCUIApplication.uiTimeout),
+            "the \"\(RichBoard.title)\" row never appeared — check the fixture copy or the first scan"
+        )
+        boardRow.tap()
+
+        let laneRow = element(labelContaining: RichBoard.firstLane)
+        XCTAssertTrue(
+            laneRow.waitForExistence(timeout: XCUIApplication.uiTimeout),
+            "the \"\(RichBoard.firstLane)\" lane row never appeared"
+        )
+        laneRow.tap()
+
+        let cardRow = element(labelContaining: RichBoard.firstLaneFirstCard)
+        XCTAssertTrue(
+            cardRow.waitForExistence(timeout: XCUIApplication.uiTimeout),
+            "the \"\(RichBoard.firstLaneFirstCard)\" card row never appeared"
+        )
+        cardRow.tap()
+    }
+
+    /// Taps `CardDetailScreen`'s Edit button and waits for `CardEditScreen`'s cover to land.
+    @MainActor
+    func openCardEdit() {
+        let editButton = navigationBars.buttons["Edit"]
+        XCTAssertTrue(
+            editButton.waitForExistence(timeout: XCUIApplication.uiTimeout),
+            "the read view's Edit button never appeared"
+        )
+        editButton.tap()
+
+        XCTAssertTrue(
+            navigationBars.buttons["Save"].waitForExistence(timeout: XCUIApplication.uiTimeout),
+            "CardEditScreen's cover never appeared"
+        )
+    }
 }

KanbanMobileUITests/MobileUITestSupport.swift

@@ -208,6 +208,39 @@ extension XCUIApplication {
     }
 }
 
+extension XCUIElement {
+
+    /// Replaces this field's/editor's entire text with `text`, wholesale.
+    ///
+    /// **Neither ⌘A nor the long-press callout survived contact with this suite.** ⌘A is delivered
+    /// as a `UIKeyCommand` down the responder chain, and that routing is not guaranteed wired up the
+    /// instant `tap()` returns — behind a `fullScreenCover`'s own presentation transition, or right
+    /// after a `TextEditor` is freshly mounted by a pane switch, ⌘A sent too early is silently
+    /// dropped while ordinary character input (a different, lower-level path) still lands, so the
+    /// retyped text ends up inserted at whatever the stale cursor position was rather than replacing
+    /// anything — and a fixed settle before it only wins *sometimes*, because under a full suite
+    /// run's extra load the gap it needs to cover stretches past any delay worth hard-coding. The
+    /// long-press "Select All" callout fares worse: it never appeared at all in this environment (the
+    /// Simulator's hardware keyboard appears to suppress the touch selection UI outright).
+    ///
+    /// What is left, and has been reliable through every run: plain character `typeText` always
+    /// lands, so the fix sidesteps selection entirely. A tap near the field's trailing/bottom edge —
+    /// past wherever the current text actually ends — is where both `UITextField` and `UITextView`
+    /// place the caret at the *end* of the text (the standard "tap in the empty run-out" behavior,
+    /// not an assumption this suite is inventing), which is what makes a plain backspace-per-character
+    /// safe here where the original in-place editor's own comment once ruled it out: that caveat was
+    /// about a tap landing *mid-text*, not about the technique itself.
+    @MainActor
+    func replaceAllText(with text: String) {
+        let trailingEdge = coordinate(withNormalizedOffset: CGVector(dx: 0.95, dy: 0.5))
+        trailingEdge.tap()
+        if let current = value as? String, !current.isEmpty {
+            typeText(String(repeating: XCUIKeyboardKey.delete.rawValue, count: current.count))
+        }
+        typeText(text)
+    }
+}
+
 // MARK: - Polling the filesystem
 
 /// Waits up to `timeout` for some file under `root` (searched recursively) to contain
@@ -223,6 +256,14 @@ func waitForFile(under root: URL, containing substring: String, timeout: TimeInt
     return fileExists(under: root, containing: substring)
 }
 
+/// A point-in-time negative check — `waitForFile`'s substring test with no polling, for asserting a
+/// draft was never written. Discarding a `CardEditScreen` never calls `session.perform` at all, so
+/// there is no async write to wait out; polling the full timeout for something that never becomes
+/// true would only slow the suite down for no better an answer than one immediate look.
+func fileDoesNotContain(under root: URL, substring: String) -> Bool {
+    !fileExists(under: root, containing: substring)
+}
+
 /// Waits up to `timeout` for the directory at `url` to exist — or, with `toExist: false`, to be
 /// gone. The package-shaped counterpart to `waitForFile(under:containing:)`, and what a move
 /// assertion needs: `relocateBoard` hands the actual transfer to a detached task and answers the UI