re-anchor the conversation tail when the bottom input zone resizes (T-297)

When the interaction zone grows/shrinks (composer ↔ permission prompt /
AskUserQuestion, D-78) the conversation viewport changed height but the scroll
offset didn't follow, leaving the last card hidden behind the taller box. Track
whether the view is pinned to the tail; a LayoutBuilder around the list detects
the viewport-height change and re-jumps to the bottom only when pinned, so a
scrolled-up reader is undisturbed.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

CHANGELOG.md

@@ -224,6 +224,11 @@ heading, and (b) bumping `pubspec.yaml` `version:` in the same commit.
 
 ### Fixed
 
+- **The conversation re-anchors when the input area resizes.** Opening a
+  permission prompt or AskUserQuestion (which grows the bottom zone, D-78) no
+  longer hides the last message behind it — when pinned to the tail, the view
+  re-scrolls to keep it visible; a scrolled-up reader is left undisturbed.
+  (T-297)
 - **The chosen theme now persists across restarts**, per repo. Picking a theme
   (status-bar switcher or Settings) writes it to the repo's
   `.clide/settings.yaml` (and a global default), and reopening the repo restores

lib/builtin/claude/src/conversation_view.dart

@@ -69,10 +69,28 @@ class ConversationView extends StatefulWidget {
 class _ConversationViewState extends State<ConversationView> {
   final ScrollController _scroll = ScrollController();
 
+  /// Whether the view is pinned to the tail — only then do we re-anchor on a
+  /// viewport resize, so a user who scrolled up isn't yanked back down (T-297).
+  bool _atBottom = true;
+
+  /// Last laid-out viewport height; a change means the bottom interaction zone
+  /// grew/shrank (a permission prompt / AskUserQuestion opened, D-78) and the
+  /// tail needs re-anchoring above the newly-sized box.
+  double? _lastViewportHeight;
+
+  static const double _bottomEpsilon = 8;
+
   @override
   void initState() {
     super.initState();
     widget.controller.addListener(_onChanged);
+    _scroll.addListener(_trackBottom);
+  }
+
+  void _trackBottom() {
+    if (!_scroll.hasClients) return;
+    final p = _scroll.position;
+    _atBottom = (p.maxScrollExtent - p.pixels) <= _bottomEpsilon;
   }
 
   @override
@@ -87,6 +105,7 @@ class _ConversationViewState extends State<ConversationView> {
   @override
   void dispose() {
     widget.controller.removeListener(_onChanged);
+    _scroll.removeListener(_trackBottom);
     _scroll.dispose();
     super.dispose();
   }
@@ -289,9 +308,26 @@ class _ConversationViewState extends State<ConversationView> {
         },
       ),
     );
+    // Re-anchor the tail when the viewport height changes — the bottom
+    // interaction zone (composer ↔ permission prompt / AskUserQuestion, D-78)
+    // resizing would otherwise leave the last card hidden behind the taller box
+    // (T-297). Only when already pinned to the bottom, so scrolled-up reading
+    // is undisturbed.
+    final sized = LayoutBuilder(
+      builder: (ctx, constraints) {
+        final h = constraints.maxHeight;
+        if (_lastViewportHeight != null && h != _lastViewportHeight && _atBottom) {
+          WidgetsBinding.instance.addPostFrameCallback((_) {
+            if (_scroll.hasClients) _scroll.jumpTo(_scroll.position.maxScrollExtent);
+          });
+        }
+        _lastViewportHeight = h;
+        return list;
+      },
+    );
     return ColoredBox(
       color: tokens.panelBackground,
-      child: widget.wrapInSelectionArea ? ClideSelectionArea(child: list) : list,
+      child: widget.wrapInSelectionArea ? ClideSelectionArea(child: sized) : sized,
     );
   }
 }

test/builtin/claude/conversation_scroll_test.dart

@@ -0,0 +1,96 @@
+/// T-297: when the bottom interaction zone resizes, the conversation re-anchors
+/// to the tail (if pinned there) so content isn't left hidden behind the taller
+/// box — and leaves a scrolled-up reader undisturbed.
+library;
+
+import 'dart:async';
+
+import 'package:clide/builtin/claude/src/conversation_controller.dart';
+import 'package:clide/builtin/claude/src/conversation_view.dart';
+import 'package:clide/builtin/claude/src/transcript_reader.dart';
+import 'package:flutter/widgets.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+import '../../helpers/kernel_fixture.dart';
+import '../../helpers/widget_harness.dart';
+
+final _t = DateTime.utc(2026, 1, 1);
+AssistantTextMessage _asst(String text, int i) => AssistantTextMessage(uuid: 'a$i', timestamp: _t, isSidechain: false, text: text);
+
+void main() {
+  late KernelFixture f;
+  setUp(() async => f = await KernelFixture.create());
+  tearDown(() => f.dispose());
+
+  ScrollPosition scrollPos(WidgetTester tester) => tester.state<ScrollableState>(find.byType(Scrollable).first).position;
+
+  Future<ConversationController> pump(WidgetTester tester, ValueNotifier<double> bottomH) async {
+    tester.view.physicalSize = const Size(600, 600);
+    tester.view.devicePixelRatio = 1.0;
+    addTearDown(() {
+      tester.view.resetPhysicalSize();
+      tester.view.resetDevicePixelRatio();
+    });
+    final stream = StreamController<ConversationItem>.broadcast();
+    final c = ConversationController(stream: stream.stream);
+    addTearDown(c.dispose);
+    await tester.pumpWidget(harness(
+      f,
+      SizedBox(
+        width: 600,
+        height: 600,
+        child: Column(
+          children: [
+            Expanded(child: ConversationView(controller: c)),
+            // Stand-in for the interaction zone (composer / prompt) whose height
+            // changes; ValueListenableBuilder rebuilds just the box.
+            ValueListenableBuilder<double>(
+              valueListenable: bottomH,
+              builder: (_, h, __) => SizedBox(height: h, width: 600),
+            ),
+          ],
+        ),
+      ),
+    ));
+    for (var i = 0; i < 40; i++) {
+      stream.add(_asst('conversation line number $i', i));
+    }
+    await tester.pumpAndSettle();
+    return c;
+  }
+
+  testWidgets('a growing bottom zone re-anchors the tail when pinned to bottom', (tester) async {
+    final bottomH = ValueNotifier<double>(40);
+    addTearDown(bottomH.dispose);
+    await pump(tester, bottomH);
+
+    final p = scrollPos(tester);
+    expect(p.pixels, closeTo(p.maxScrollExtent, 1), reason: 'starts pinned to the tail');
+
+    // The interaction zone grows (a permission prompt opened).
+    bottomH.value = 220;
+    await tester.pumpAndSettle();
+
+    final p2 = scrollPos(tester);
+    expect(p2.pixels, closeTo(p2.maxScrollExtent, 1), reason: 'still pinned after the zone grew');
+  });
+
+  testWidgets('a scrolled-up reader is not yanked when the zone resizes', (tester) async {
+    final bottomH = ValueNotifier<double>(40);
+    addTearDown(bottomH.dispose);
+    await pump(tester, bottomH);
+
+    // Scroll up, away from the tail.
+    scrollPos(tester).jumpTo(30);
+    await tester.pump();
+    final before = scrollPos(tester).pixels;
+    expect(before, closeTo(30, 1));
+
+    bottomH.value = 220;
+    await tester.pumpAndSettle();
+
+    final after = scrollPos(tester);
+    expect(after.pixels, closeTo(before, 1), reason: 'offset preserved; not re-anchored to bottom');
+    expect(after.pixels, lessThan(after.maxScrollExtent - 8), reason: 'still not at the tail');
+  });
+}