fix(mobile): iOS 18 iPad sidebar and thread feed start below the header

apps/mobile/src/components/ui/useBarInset.ts

@@ -38,9 +38,9 @@ export function useBarOverlap(): number {
 }
 
 /**
- * The content's top safe area under the AppBar: a translucent bar's height, zero under a solid
- * one or on Android, where the bar sits in flow. For scroll content insets, which must not
- * double-count a solid bar.
+ * The content's top safe area under the AppBar: the height of the iOS bar its column lays content
+ * under, glass or solid, and zero on Android, where the bar sits in flow. For manual scroll
+ * content insets.
  */
 export function useContentTopInset(): number {
   const insets = useSafeAreaInsets();

apps/mobile/src/features/layout/workspace/workspace-list-insets.ts

@@ -2,12 +2,6 @@ import { useSafeAreaInsets } from "react-native-safe-area-context";
 
 import { NATIVE_LIQUID_GLASS_SUPPORTED } from "../../../native/native-glass";
 
-/** A workspace list scrolls under its bar where the bar is glass; under a solid bar it starts below. */
-export const WORKSPACE_LIST_SCROLL_INSETS = {
-  automaticallyAdjustsScrollIndicatorInsets: NATIVE_LIQUID_GLASS_SUPPORTED,
-  contentInsetAdjustmentBehavior: NATIVE_LIQUID_GLASS_SUPPORTED ? "automatic" : "never",
-} as const;
-
 /** How far an empty workspace list keeps its message below a glass bar and its search. */
 export function useWorkspaceListEmptyTopInset(): number {
   const insets = useSafeAreaInsets();

apps/mobile/src/features/threads/ThreadDetailScreen.tsx

@@ -1496,7 +1496,6 @@ function ThreadDetailBody(
                   keyboardOffset={composerKeyboardOffset}
                   sendingWithKeyboard={sendingWithKeyboard}
                   fitShortFeedToViewport={questionInFlow && !isKeyboardVisible}
-                  contentTopInset={0}
                   contentBottomInset={
                     questionInFlow
                       ? 0

apps/mobile/src/features/threads/ThreadFeed.tsx

@@ -170,7 +170,7 @@ import { getReviewSectionIdForCheckpoint } from "../review/reviewModel";
 import { setReviewSelectedSectionId } from "../review/reviewState";
 import { Menu } from "../../components/ui/Menu";
 import { useAndroidControlSizing } from "../../components/ui/useAndroidControlSizing";
-import { useBarInset } from "../../components/ui/useBarInset";
+import { useBarInset, useContentTopInset } from "../../components/ui/useBarInset";
 import { copyPromptLink } from "../prompt-links/prompt-link-actions";
 import { parseReviewCommentMessageSegments } from "../review/reviewCommentSelection";
 import {
@@ -332,7 +332,6 @@ export interface ThreadFeedProps {
   readonly keyboardOffset: number;
   readonly sendingWithKeyboard?: boolean;
   readonly fitShortFeedToViewport?: boolean;
-  readonly contentTopInset?: number;
   readonly contentBottomInset?: number;
   readonly historyControls?: ThreadFeedHistoryControls;
   readonly contentMaxWidth?: number;
@@ -2772,10 +2771,12 @@ export const ThreadFeed = memo(function ThreadFeed(props: ThreadFeedProps) {
   const markdownContentWidth = Math.max(0, contentWidth - ASSISTANT_ROW_HORIZONTAL_PADDING * 2);
   const reviewCommentBubbleWidth = Math.min(Math.max(280, contentWidth * 0.85), contentWidth);
   const barInset = useBarInset();
-  const topContentInset = props.contentTopInset ?? barInset;
+  const columnTopInset = useContentTopInset();
   const bottomContentInset = props.contentBottomInset ?? 18;
   const usesNativeAutomaticInsets =
     props.usesAutomaticContentInsets === true && Platform.OS === "ios";
+  // Without the native contentInset, a list-header spacer clears the bar the column lays content under.
+  const topContentInset = usesNativeAutomaticInsets ? 0 : columnTopInset;
   const anchorTopInset = usesNativeAutomaticInsets ? barInset : topContentInset;
 
   const theme = useUniwindTheme();
@@ -3200,7 +3201,9 @@ export const ThreadFeed = memo(function ThreadFeed(props: ThreadFeedProps) {
     if (state) onIsAtEndChange?.(state.isAtEnd);
   };
   const handleScroll = (event: NativeSyntheticEvent<NativeScrollEvent>) => {
-    reportHeaderMaterialVisibility(event.nativeEvent.contentOffset.y + anchorTopInset > 6);
+    reportHeaderMaterialVisibility(
+      event.nativeEvent.contentOffset.y + (usesNativeAutomaticInsets ? barInset : 0) > 6,
+    );
     handleMetricsChange();
   };
   // oxlint-disable-next-line t3code/no-unreasoned-state-sync -- subscribes to the list's end state to report it to the parent

apps/mobile/src/features/threads/ThreadNavigationSidebar.tsx

@@ -48,7 +48,6 @@ import { usePendingTaskListActions } from "../home/usePendingTaskListActions";
 import { useThreadListActions } from "../home/useThreadListActions";
 import { useFabScroll } from "../home/FabScrollContext";
 import { WorkspaceListHeader } from "../layout/workspace/WorkspaceListHeader";
-import { WORKSPACE_LIST_SCROLL_INSETS } from "../layout/workspace/workspace-list-insets";
 import { WorkspaceSidebarColumn } from "../layout/workspace/WorkspaceSidebarColumn";
 import {
   ThreadListV2PendingRow,
@@ -592,7 +591,9 @@ function ThreadNavigationSidebarPane(props: ThreadNavigationSidebarProps) {
                 itemsAreEqual={sidebarItemsAreEqual}
                 keyExtractor={(item) => item.key}
                 renderItem={renderListItem}
-                {...WORKSPACE_LIST_SCROLL_INSETS}
+                automaticallyAdjustsScrollIndicatorInsets
+                // The column lays the list under its bar, glass or solid; UIKit insets it past both.
+                contentInsetAdjustmentBehavior="automatic"
                 contentContainerStyle={[
                   styles.threadListContent,
                   {