fix(ui-conversation): preserve semantic chat scroll position

.agents/notes/implemented/bug-fix/2026-07-29-sticky-composer-conversation-scroll.i18n.yaml

@@ -2,5 +2,5 @@
 # side as of the last confirmed-consistent state. Both languages carry equal authority;
 # after editing either side, bring the other along and re-record with:
 #   pnpm run verify-translation-pairing --write .agents/notes/implemented/bug-fix/2026-07-29-sticky-composer-conversation-scroll.md
-2026-07-29-sticky-composer-conversation-scroll.md: 7ceae95dafffdb756ef49bb5612cd4e711eb59ca
-2026-07-29-sticky-composer-conversation-scroll.zh.md: d925d82f94635b5fe67b0be119c041d003def393
+2026-07-29-sticky-composer-conversation-scroll.md: 1ec68cfbf2d78b2bda936822be6784f6fbd17a20
+2026-07-29-sticky-composer-conversation-scroll.zh.md: b163b3b08ce9664c7d0aad6b46fca1675f29ce1f

.agents/notes/implemented/bug-fix/2026-07-29-sticky-composer-conversation-scroll.md

@@ -14,6 +14,8 @@ While a session exists, `ConversationRoot` always supplies a `wrapActiveBody` ow
 
 Session stats live on `'conversation.composer.dock'` (above `'conversation.input.dock'`). The InputBar textarea, when inside the host, chains `wheel` with `{ passive: false }`: while the capped textarea can still scroll in that direction it keeps the native gesture; only at its own edge does it `preventDefault` and apply `deltaY` to the host.
 
+Chat history prepend follows reader intent through stable rendered node/call identities rather than whole-scrollport height deltas. `ChatView` records the first visible `data-chat-anchor-key` and its top relative to the scrollport when paging starts, reselects the currently visible stable anchor after every reader scroll while the request is in flight, and compensates by that row's post-prepend rectangle delta. Reaching the bottom or appending the reader's own message cancels the paging anchor, so a late page cannot pull the view away from the newest content. ChatView's single `ResizeObserver` owns bottom-follow decisions for column and sticky-composer height changes: it follows streaming, tool disclosure, and draft resize only while bottom ownership remains pinned, without a second per-chunk scroll write.
+
 ## Alternatives considered
 
 **Sticky header and sticky composer inside one column scrollport.** Rejected for the header: it must occupy the top as fixed layout chrome, not participate in the scrollport's sticky layer.
@@ -26,4 +28,4 @@ Session stats live on `'conversation.composer.dock'` (above `'conversation.input
 
 ## Consequences
 
-Wheel over the footer scrolls the transcript; the visible layout is a fixed header, scrolling transcript, and sticky bottom composer. Stats appear on every active view tab. Nested view scrollers under the host are suppressed so sticky Turn headers in Trajectory stick to the column host. Hero → active keeps the same textarea DOM node (assembled slash-flow snapshot) and the InputHub draft.
+Wheel over the footer scrolls the transcript; the visible layout is a fixed header, scrolling transcript, and sticky bottom composer. Stats appear on every active view tab. Nested view scrollers under the host are suppressed so sticky Turn headers in Trajectory stick to the column host. Concurrent history, streaming, tool expansion, and composer reflow cannot overwrite a reader's newer scroll decision. Hero → active keeps the same textarea DOM node (assembled slash-flow snapshot) and the InputHub draft.

.agents/notes/implemented/bug-fix/2026-07-29-sticky-composer-conversation-scroll.zh.md

@@ -14,6 +14,8 @@ Status: implemented
 
 会话统计挂在 `'conversation.composer.dock'`（位于 `'conversation.input.dock'` 之上）。InputBar 的 textarea 在宿主内以 `{ passive: false }` 链式处理 `wheel`：在限高 textarea 仍能沿该方向滚动时保留原生手势；仅在自身边缘才 `preventDefault` 并将 `deltaY` 施加到宿主。
 
+Chat 历史前插通过稳定的已渲染 node／call 身份跟随读者意图，而不是使用整个滚动容器的高度差。分页开始时，`ChatView` 记录第一个可见的 `data-chat-anchor-key` 及其相对滚动容器的顶部位置；请求在途期间，每次读者滚动都会重新选择当前可见的稳定锚点；页面到达后则按该行矩形的前后差值补偿。到达底部或追加读者自己的消息会取消分页锚点，因此迟到的页面不能把视图从最新内容拉走。`ChatView` 的单个 `ResizeObserver` 统一负责消息列与 sticky 编辑器高度变化的贴底跟随决策：只有在仍贴底时才跟随流式输出、工具展开与草稿尺寸变化，且每个 chunk 不会触发第二次滚动写入。
+
 ## Alternatives considered
 
 **标题栏与编辑器都在同一列滚动容器内 sticky。** 标题栏否决：它必须作为固定布局 chrome 占据顶部，而不是参与滚动容器的 sticky 层。
@@ -26,4 +28,4 @@ Status: implemented
 
 ## Consequences
 
-在页脚上滚轮会滚动 transcript；可见布局是固定标题栏、可滚动 transcript 与 sticky 底部编辑器。统计出现在每一个活跃视图标签上。宿主下的嵌套视图 scroller 被抑制，因而 Trajectory 的 sticky Turn 标题贴在列宿主上。hero → active 保持同一 textarea DOM 节点（assembled slash-flow 快照）以及 InputHub 草稿。
+在页脚上滚轮会滚动 transcript；可见布局是固定标题栏、可滚动 transcript 与 sticky 底部编辑器。统计出现在每一个活跃视图标签上。宿主下的嵌套视图 scroller 被抑制，因而 Trajectory 的 sticky Turn 标题贴在列宿主上。并发历史加载、流式输出、工具展开与编辑器重排都不能覆盖读者更新的滚动决定。hero → active 保持同一 textarea DOM 节点（assembled slash-flow 快照）以及 InputHub 草稿。

.agents/notes/implemented/feature/2026-07-30-web-tool-row-unified-expand-and-inspect.i18n.yaml

@@ -2,5 +2,5 @@
 # side as of the last confirmed-consistent state. Both languages carry equal authority;
 # after editing either side, bring the other along and re-record with:
 #   pnpm run verify-translation-pairing --write .agents/notes/implemented/feature/2026-07-30-web-tool-row-unified-expand-and-inspect.md
-2026-07-30-web-tool-row-unified-expand-and-inspect.md: ba2f4ead8023772fad578ca0b647241ecc332905
-2026-07-30-web-tool-row-unified-expand-and-inspect.zh.md: ac4835c7429a3ff7d3042f73d26d267911533132
+2026-07-30-web-tool-row-unified-expand-and-inspect.md: 98f1595564f0bd0d22f1ca4318b4c7fe15c6900d
+2026-07-30-web-tool-row-unified-expand-and-inspect.zh.md: 8f00349a975f777cc4d556ade3a9abe9676b8848

.agents/notes/implemented/feature/2026-07-30-web-tool-row-unified-expand-and-inspect.md

@@ -10,14 +10,14 @@ The chat view's tool rows had drifted into per-surface interaction dialects: Too
 
 ## Decision
 
-**Every expandable tool row shares one interaction — the whole row toggles (click / Enter / Space) with an icon→chevron hover preview — and one expanded body: an IN/OUT gutter-labeled card with per-section scroll caps; a hover-revealed Inspect pill jumps to the call's trajectory record through a one-shot store handoff; the chat view preserves its scroll offset across view switches through an in-memory per-session map.**
+**Every expandable tool row shares one interaction — the whole row toggles (click / Enter / Space) with an icon→chevron hover preview — and one expanded body: an IN/OUT gutter-labeled card with per-section scroll caps; a hover-revealed Inspect pill jumps to the call's trajectory record through a one-shot store handoff; the chat view preserves its semantic reading position across view switches through an in-memory per-session map.**
 
 - `toolRowModel` now derives result material alongside args: `output` (the `resultText` flatten, moved from DetailsPanel into the contract), and `errorSummary` (the failure's first line, shown as the collapsed summary in the error color). A row with body, output, or terminal material is expandable; the row itself is the toggle (`role="button"`, `aria-expanded`), and file-path summaries stay independent links via `stopPropagation`.
 - The expanded card (figma 1249:35657) is a column of IN/OUT sections: each section is its own scrollport (max-height 150px) with a sticky gutter label, and the l2 divider spans the full card width. Think prose and the run_code CodeBlock keep their non-card bodies; context injection reuses the row with a label-less `plainBody` card.
 - `terminalFailed` reads a settled terminal card's exit status so BashRow and GenericToolCard surface a failing command as the row's red state dot — the only failure signal the collapsed row has, since the call itself settles `isError:false`.
 - TerminalBlock's banner joins the same reading model: it shares the card surface (no banner token), an l2 hairline separates it from the body, the command column caps at 150px and scrolls with sticky copy/status controls top-aligned to the first prompt row.
 - Inspect: `ToolRowOwnerProps.inspect` (absent for rows without a call identity) renders a pill in real flow under the expanded body's bottom-left, revealed by hovering anywhere on the tool call. Clicking writes `{ callId }` to the chat store's one-shot `inspect` field and switches to the trajectory view; TrajectoryTable finds the record, opens its summary, and acknowledges by clearing the field.
-- Scroll preservation: the chat view saves its offset on every scroll (null when pinned to bottom) into an apply-scope `Map<SessionId, number>` exposed as `chatScroll` on the injected props; the open-jump branch restores it on remount. Deliberately not persisted — a fresh page load keeps the open-jump-to-bottom default.
+- Scroll preservation: on every non-bottom scroll, the chat view saves `{ anchorKey, anchorTop, scrollTop }` into an apply-scope per-session map exposed as `chatScroll`; a remount first uses `scrollTop` to reach the approximate window, then corrects by the stable node/call anchor's rectangle delta so width reflow keeps the same reading row in place. Every pinned path, including Back to bottom, clears the entry synchronously before a tab or session switch. The map remains deliberately unpersisted — a fresh page load keeps the open-jump-to-bottom default.
 
 ## Alternatives considered
 

.agents/notes/implemented/feature/2026-07-30-web-tool-row-unified-expand-and-inspect.zh.md

@@ -10,14 +10,14 @@
 
 ## 决定
 
-**所有可展开工具行共享同一交互——整行即开关（点击 / Enter / 空格），图标 hover 时渐变为 chevron 预览——以及同一展开体：带 IN/OUT 侧栏标签的卡片，各分区独立滚动上限；hover 显示的 Inspect 胶囊通过 store 的一次性交接跳到该调用的 trajectory 记录；聊天视图用内存态的按会话 Map 在视图切换间保留滚动位置。**
+**所有可展开工具行共享同一交互——整行即开关（点击 / Enter / 空格），图标 hover 时渐变为 chevron 预览——以及同一展开体：带 IN/OUT 侧栏标签的卡片，各分区独立滚动上限；hover 显示的 Inspect 胶囊通过 store 的一次性交接跳到该调用的 trajectory 记录；聊天视图用内存态的按会话 Map 在视图切换间保留语义阅读位置。**
 
 - `toolRowModel` 在 args 之外同时派生结果材料：`output`（`resultText` 拍平逻辑从 DetailsPanel 移入 contract）和 `errorSummary`（失败首行，以错误色作为折叠摘要）。有 body、output 或 terminal 材料的行即可展开；行本身是开关（`role="button"`、`aria-expanded`），文件路径摘要通过 `stopPropagation` 保持独立链接。
 - 展开卡片（figma 1249:35657）是 IN/OUT 分区列：每个分区是独立滚动区（max-height 150px），侧栏标签 sticky 固定，l2 分割线横贯整卡宽度。Think 的推理文本和 run_code 的 CodeBlock 保持非卡片体；上下文注入复用此行并以无标签的 `plainBody` 卡片展开。
 - `terminalFailed` 读取已结算 terminal 卡片的退出状态，让 BashRow 和 GenericToolCard 把失败命令显示为行的红色状态点——这是折叠行唯一的失败信号，因为调用本身结算为 `isError:false`。
 - TerminalBlock 的横幅并入同一阅读模型：与卡片共用同一表面（不再用 banner token），与正文之间是 l2 细线，命令列上限 150px 内部滚动，复制/状态控件 sticky 且顶对齐第一行提示符。
 - Inspect：`ToolRowOwnerProps.inspect`（无调用身份的行不提供）在展开体左下角以真实布局位置渲染胶囊，hover 整个 tool call 任意位置显示。点击将 `{ callId }` 写入 chat store 的一次性 `inspect` 字段并切换到 trajectory 视图；TrajectoryTable 找到记录、打开其摘要，并通过清空字段确认。
-- 滚动保留：聊天视图在每次滚动时保存偏移（贴底时为 null）到 apply 作用域的 `Map<SessionId, number>`，经注入 props 的 `chatScroll` 暴露；重挂载时 open-jump 分支恢复它。刻意不持久化——新页面加载保持打开即贴底的默认行为。
+- 滚动保留：每次非贴底滚动时，聊天视图把 `{ anchorKey, anchorTop, scrollTop }` 保存到 apply 作用域的按会话 Map，并经注入 props 的 `chatScroll` 暴露；重挂载时先用 `scrollTop` 到达近似窗口，再按稳定 node／call 锚点的矩形差值校正，因此宽度重排后仍把同一阅读行保持在原位。包括「回到底部」在内的每条贴底路径都会在切换 tab 或会话前同步清除该项。Map 仍刻意不持久化——新页面加载保持打开即贴底的默认行为。
 
 ## 曾考虑的替代方案