fix(chat): 回复完成后保持消息流贴底

apps/desktop/src/renderer/__tests__/focusScrollLifecycle.test.ts

@@ -2,6 +2,7 @@ import { readFileSync } from 'node:fs';
 import { describe, expect, it } from 'vitest';
 
 import {
+  consumePendingReanchorForAutoFollow,
   pickIntersectingChildAnchor,
   readAnchorClientId,
   readViewportChildAnchorClientId,
@@ -61,6 +62,36 @@ describe('focus scroll cancellation decisions', () => {
   });
 });
 
+describe('render-item compensation priority', () => {
+  it('consumes pending reanchor and short-circuits old compensation while following the tail', () => {
+    let pendingReanchor = true;
+
+    const shouldShortCircuit = consumePendingReanchorForAutoFollow({
+      isNearBottom: true,
+      clearPendingReanchor: () => {
+        pendingReanchor = false;
+      },
+    });
+
+    expect(shouldShortCircuit).toBe(true);
+    expect(pendingReanchor).toBe(false);
+  });
+
+  it('preserves pending reanchor and continues compensation after the user scrolls up', () => {
+    let clearCount = 0;
+
+    const shouldShortCircuit = consumePendingReanchorForAutoFollow({
+      isNearBottom: false,
+      clearPendingReanchor: () => {
+        clearCount += 1;
+      },
+    });
+
+    expect(shouldShortCircuit).toBe(false);
+    expect(clearCount).toBe(0);
+  });
+});
+
 describe('chip jump settlement', () => {
   it('recomputes the landing from settled target geometry after content above it is deleted', () => {
     expect(
@@ -425,6 +456,26 @@ describe('MessageStream focus cancellation wiring', () => {
     expect(compensation).not.toContain('if (anchor.messageClientId && snapshotMessageGone) {');
   });
 
+  it('uses the auto-follow decision as a hard return before viewport compensation', () => {
+    const compensation = sourceBetween(
+      '// ── 删除靠前 message 后的视口保位（#2289）──',
+      '// ── post-load auto-expand ──',
+    );
+    const guardStart = compensation.indexOf('consumePendingReanchorForAutoFollow({');
+    const guardEnd = compensation.indexOf(
+      'const snapshot = lastViewportTopRef.current;',
+      guardStart,
+    );
+    expect(guardStart).toBeGreaterThanOrEqual(0);
+    expect(guardEnd).toBeGreaterThan(guardStart);
+    const guard = compensation.slice(guardStart, guardEnd);
+
+    expect(guard).toContain('isNearBottom: isNearBottomRef.current');
+    expect(guard).toContain('pendingReanchorScrollRef.current = null;');
+    expect(guard).toMatch(/\)\s*\{\s*return;\s*\}/);
+    expect(compensation).not.toContain('if (isNearBottomRef.current) return;');
+  });
+
   it('finishes an older chip or rail navigation before starting a jump to bottom', () => {
     const jumpToBottom = sourceBetween(
       'const scrollToBottomSmooth = useCallback(() => {',

apps/desktop/src/renderer/components/chat/MessageStream.tsx

@@ -125,6 +125,22 @@ export function resolveProgrammaticScrollEndDecision({
   return consumeDeferredDelete ? 'consume-deferred-delete' : 'replay-deferred-delete';
 }
 
+/**
+ * 贴底时由 auto-follow 独占本轮布局变化，并消费此前记录的视口重锚。
+ * 返回 true 表示调用方必须立即结束旧视口补偿，避免其覆盖同一提交里的 pinToBottom。
+ */
+export function consumePendingReanchorForAutoFollow({
+  isNearBottom,
+  clearPendingReanchor,
+}: {
+  isNearBottom: boolean;
+  clearPendingReanchor: () => void;
+}): boolean {
+  if (!isNearBottom) return false;
+  clearPendingReanchor();
+  return true;
+}
+
 /** 以落定时的最新 DOM 几何重新计算 chip / 导航轨道目标，而不是复用 smooth 开始前的像素。 */
 export function resolveChipJumpTargetScrollTop({
   scrollTop,
@@ -5132,6 +5148,21 @@ export function MessageStream({
     const prevAllItems = prevAllItemsRef.current;
     prevVisibleItemsRef.current = visibleRenderItems;
     prevAllItemsRef.current = allRenderItems;
+
+    // #3067: turn 完成会把运行中工作组重建为完成态分组，key / 数量都可能变化。
+    // 贴底态必须始终由 auto-follow 接管；若先执行旧锚点恢复，会覆盖上方同一提交里的
+    // pinToBottom，把视口拉回本轮 user 消息。同步消费待重锚，避免用户稍后上滚时重放旧落点。
+    if (
+      consumePendingReanchorForAutoFollow({
+        isNearBottom: isNearBottomRef.current,
+        clearPendingReanchor: () => {
+          pendingReanchorScrollRef.current = null;
+        },
+      })
+    ) {
+      return;
+    }
+
     const snapshot = lastViewportTopRef.current;
     const prevSeq = prevAllItems.length > 0 ? prevAllItems : prevVisibleItems;
 
@@ -5191,8 +5222,6 @@ export function MessageStream({
       if (programmaticScrollRef.current) deferredDeleteCompensationRef.current = true;
       return;
     }
-    if (isNearBottomRef.current) return;
-
     let anchor = snapshot;
     if (restoringRef.current) {
       const snap = restoreSnapshotRef.current;