From dc91a461d60f1a60c8e00aa89ddfd1895e1ee9f1 Mon Sep 17 00:00:00 2001
From: murashit <murashit@proton.me>
Date: Sun, 21 Jun 2026 23:10:31 +0900
Subject: [PATCH] Fix work details stream spacing

---
 .../chat/ui/message-stream/virtualizer.ts     | 35 ++++++++++++++++++-
 .../ui/message-stream/virtualizer.test.ts     | 21 +++++++++++
 2 files changed, 55 insertions(+), 1 deletion(-)

diff --git a/src/features/chat/ui/message-stream/virtualizer.ts b/src/features/chat/ui/message-stream/virtualizer.ts
index 83fbf3c6..168d5918 100644
--- a/src/features/chat/ui/message-stream/virtualizer.ts
+++ b/src/features/chat/ui/message-stream/virtualizer.ts
@@ -52,11 +52,12 @@ interface MessageVirtualizerRuntime {
   viewportRestoreFrame: number | null;
   virtualizerChangeFrame: number | null;
   settleScrollToEndFrame: number | null;
+  anchorClampFrame: number | null;
   settleScrollToEndAttemptsRemaining: number;
   userScrollIntentUntil: number;
 }
 
-type MessageVirtualizerFrameKey = "viewportRestoreFrame" | "virtualizerChangeFrame" | "settleScrollToEndFrame";
+type MessageVirtualizerFrameKey = "viewportRestoreFrame" | "virtualizerChangeFrame" | "settleScrollToEndFrame" | "anchorClampFrame";
 
 export interface MessageStreamVirtualizerOptions {
   blocks: readonly MessageStreamBlock[];
@@ -160,6 +161,7 @@ function createMessageVirtualizerRuntime(): MessageVirtualizerRuntime {
     viewportRestoreFrame: null,
     virtualizerChangeFrame: null,
     settleScrollToEndFrame: null,
+    anchorClampFrame: null,
     settleScrollToEndAttemptsRemaining: 0,
     userScrollIntentUntil: 0,
   };
@@ -384,6 +386,7 @@ function scrollMessageVirtualizerByPage(runtime: MessageVirtualizerRuntime, dire
 function disposeMessageVirtualizer(runtime: MessageVirtualizerRuntime): void {
   cancelViewportRestoreMessageVirtualizerReset(runtime);
   cancelDeferredMessageVirtualizerChange(runtime);
+  cancelPreservedMessageVirtualizerEndClamp(runtime);
   cancelPendingMessageVirtualizerBottomFollow(runtime);
   runtime.cleanupVirtualizer?.();
   runtime.cleanupVirtualizer = null;
@@ -406,6 +409,7 @@ function attachMessageVirtualizer(runtime: MessageVirtualizerRuntime, container:
 function detachMessageVirtualizer(runtime: MessageVirtualizerRuntime): void {
   cancelViewportRestoreMessageVirtualizerReset(runtime);
   cancelDeferredMessageVirtualizerChange(runtime);
+  cancelPreservedMessageVirtualizerEndClamp(runtime);
   cancelPendingMessageVirtualizerBottomFollow(runtime);
   runtime.cleanupVirtualizer?.();
   runtime.cleanupVirtualizer = null;
@@ -419,6 +423,7 @@ function detachMessageVirtualizer(runtime: MessageVirtualizerRuntime): void {
 function resetMessageVirtualizer(runtime: MessageVirtualizerRuntime, container: HTMLElement): void {
   cancelViewportRestoreMessageVirtualizerReset(runtime);
   cancelDeferredMessageVirtualizerChange(runtime);
+  cancelPreservedMessageVirtualizerEndClamp(runtime);
   cancelSettledMessageVirtualizerScrollToEnd(runtime);
   runtime.cleanupVirtualizer?.();
   runtime.cleanupVirtualizer = null;
@@ -656,6 +661,31 @@ function cancelSettledMessageVirtualizerScrollToEnd(runtime: MessageVirtualizerR
   runtime.settleScrollToEndAttemptsRemaining = 0;
 }
 
+function schedulePreservedMessageVirtualizerEndClamp(runtime: MessageVirtualizerRuntime): void {
+  const container = runtime.container;
+  if (!container || runtime.anchorClampFrame !== null) return;
+  scheduleMessageVirtualizerFrame(runtime, "anchorClampFrame", container, () => {
+    if (runtime.container !== container || !isMessageVirtualizerPreservingReadingAnchor(runtime)) return;
+    const scrollEnd = Math.max(0, runtime.virtualizer.getTotalSize() - container.clientHeight);
+    if (Math.abs(container.scrollTop - scrollEnd) <= MESSAGE_BOTTOM_THRESHOLD) {
+      updateMessageVirtualizer(runtime.virtualizer);
+      markMessageVirtualizerFollowEndIntent(runtime);
+      notifyMessageVirtualizerChange(runtime);
+      return;
+    }
+    if (container.scrollTop < scrollEnd) return;
+    runtime.virtualizer.scrollToOffset(scrollEnd);
+    syncMessageVirtualizerScrollOffset(runtime);
+    updateMessageVirtualizer(runtime.virtualizer);
+    markMessageVirtualizerFollowEndIntent(runtime);
+    notifyMessageVirtualizerChange(runtime);
+  });
+}
+
+function cancelPreservedMessageVirtualizerEndClamp(runtime: MessageVirtualizerRuntime): void {
+  cancelMessageVirtualizerFrame(runtime, "anchorClampFrame");
+}
+
 function scheduleMessageVirtualizerFrame(
   runtime: MessageVirtualizerRuntime,
   key: MessageVirtualizerFrameKey,
@@ -743,6 +773,9 @@ function measureMessageElement(
 ): number {
   const box = entry?.borderBoxSize[0];
   const size = box ? Math.round(box.blockSize) : element.offsetHeight || instance.options.estimateSize(instance.indexFromElement(element));
+  if (entry && isMessageVirtualizerPreservingReadingAnchor(runtime)) {
+    schedulePreservedMessageVirtualizerEndClamp(runtime);
+  }
   if (entry && hasMessageVirtualizerFollowEndIntent(runtime)) {
     // ResizeObserver measurements can arrive while TanStack and DOM heights are still converging, so keep the bounded settle.
     scheduleMessageVirtualizerBottomReconcileAfterCommit(runtime);
diff --git a/tests/features/chat/ui/message-stream/virtualizer.test.ts b/tests/features/chat/ui/message-stream/virtualizer.test.ts
index 40c62f6e..2647b5c6 100644
--- a/tests/features/chat/ui/message-stream/virtualizer.test.ts
+++ b/tests/features/chat/ui/message-stream/virtualizer.test.ts
@@ -463,6 +463,27 @@ describe("TestMessageStreamVirtualizer", () => {
     });
   });
 
+  it("clamps stale unpinned offsets when a visible item shrinks near the end", () => {
+    withResizeObserverEntries((resizeElement, flushFrames) => {
+      const container = messageContainer({ scrollTop: 0, clientHeight: 100 });
+      const controller = createMessageStreamVirtualizerDriver(container);
+      const details = measuredElement("details", 1, 500);
+
+      renderVirtualItems(controller, container, ["first", "details", "last"], [300, 500, 270], "force-bottom");
+      controller.measureElement(details);
+      userScrollTo(container, 720);
+
+      container.dataset["testTotalSize"] = "590";
+      container.dataset["testScrollHeight"] = "1070";
+      resizeElement(details, 20);
+      flushFrames();
+
+      expect(controller.getTotalSize()).toBe(590);
+      expect(container.scrollTop).toBe(490);
+      controller.dispose();
+    });
+  });
+
   it("keeps the reading position when the message viewport shrinks away from the end", () => {
     withResizeObserver((triggerResize) => {
       const container = messageContainer({ scrollTop: 0, clientHeight: 160 });