feat(web): incremental render-window batch rendering engine

Add render_window.js: Python-driven incremental pagination with id+chainIndex state, anchor restore, batch guard and streaming auto-detect; wired through chat_bridge and the page shell.

ui/web/app.js

@@ -136,6 +136,8 @@ function reportWebScroll() {
 }
 document.addEventListener('scroll', function() {
     requestAnimationFrame(reportWebScroll);
+    // 🆕 P1-01：自动模式顶部自动加载旧页 / 双模式底部自动恢复新页
+    if (typeof rwAutoCheck === 'function') requestAnimationFrame(rwAutoCheck);
 }, { passive: true, capture: true });
 window.addEventListener('resize', function() {
     requestAnimationFrame(reportWebScroll);
@@ -783,7 +785,7 @@ function createMessage(msgId, role, initialText, senderName, branchInfo) {
         wrapper.classList.add('streaming');
     }
     diagEvent('createMessage', { id: msgId, role: role, stream: role === 'assistant' });
-    if (typeof softScroll === 'function') {
+    if (typeof softScroll === 'function' && !window.__rwPageRendering) {
         softScroll();
     }
 }
@@ -820,7 +822,7 @@ function createLongMessage(msgId, role, fullText, senderName, sizeKb) {
     chatContainer.appendChild(wrapper);
 
     messageBuffer[msgId] = { reasoning: '', content: '', follow: true };
-    softScroll();
+    if (!window.__rwPageRendering) softScroll();
 }
 
 // ==================== 带附件的用户消息 ====================
@@ -869,7 +871,7 @@ function createUserMessageWithAttachments(msgId, plainText, attachments) {
     chatContainer.appendChild(wrapper);
 
     messageBuffer[msgId] = { reasoning: '', content: '', follow: true };
-    softScroll();
+    if (!window.__rwPageRendering) softScroll();
 }
 
 // ==================== 附件卡片构建器 ====================
@@ -1403,6 +1405,10 @@ function finishMessage(msgId) {
 
     // --- C. 移除 streaming（操作栏自动显示） ---
     wrapper.classList.remove('streaming');
+    // 🆕 P1-01：流结束 → 解除渲染窗口流式保护（恢复可裁剪）
+    if (typeof rwState !== 'undefined' && rwState && typeof RenderWindowState !== 'undefined') {
+        RenderWindowState.streamFinished(rwState, msgId);
+    }
 
     // --- E. 代码高亮（增量渲染已渐进高亮过的会被跳过？这里统一兜底一次） ---
     wrapper.querySelectorAll('pre code').forEach(function(block) {
@@ -1410,6 +1416,8 @@ function finishMessage(msgId) {
     });
 
     // --- F. 等重排完成 ---
+    // 🆕 P1-01：在调度时刻捕获渲染批次标志（延迟回调触发时批次已结束，不能届时再读）
+    var rwBatchSuppressed = !!window.__rwPageRendering;
     requestAnimationFrame(function() {
         setTimeout(function() {
             collapsedBlocks.forEach(function(block) {
@@ -1418,8 +1426,11 @@ function finishMessage(msgId) {
                     block.scrollTop = block.scrollHeight;
                 }
             });
-            var anchor = document.getElementById('scroll-anchor');
-            if (anchor) anchor.scrollIntoView({ behavior: 'smooth', block: 'end' });
+            // 🆕 P1-01：窗口换页/初始窗口批次渲染期间不自动滚底（锚点由 rw 控制器恢复）
+            if (!rwBatchSuppressed) {
+                var anchor = document.getElementById('scroll-anchor');
+                if (anchor) anchor.scrollIntoView({ behavior: 'smooth', block: 'end' });
+            }
         }, 50);
     });
 
@@ -2063,6 +2074,12 @@ function clearChat() {
     finalContentStore = {};
     attachmentMetaStore = {};
 
+    // 🆕 P1-01：清渲染窗口状态机（游标/缓存/未决请求/代次；配置模式与大小保留）
+    if (typeof rwState !== 'undefined' && rwState && typeof RenderWindowState !== 'undefined') {
+        RenderWindowState.clear(rwState);
+        rwUpdateLoadButtons();
+    }
+
     var welcome = document.querySelector('.welcome-screen');
     if (welcome) welcome.style.display = 'none';
     reportWebScroll();
@@ -2106,6 +2123,187 @@ function insertThinkBlock(msgId, reasoningText) {
     contentDiv.insertBefore(thinkBlock, replyDiv);
 }
 
+// ==================== 🆕 P1-01 双向渲染窗口（DOM 层；状态机见 render_window.js） ====================
+var rwState = null;  // RenderWindowState 实例（rwApplyConfig 注入配置后创建）
+
+function rwApplyConfig(cfg) {
+    rwState = RenderWindowState.create(cfg || {});
+}
+
+/* 一轮窗口化加载开始：清屏 + 重同步 (session, generation)。 */
+function rwBegin(sessionId, generation, total) {
+    clearChat();
+    if (!rwState) rwState = RenderWindowState.create({});
+    RenderWindowState.clear(rwState);
+    rwState.sessionId = sessionId;
+    rwState.generation = (generation | 0);
+    if (total <= 0) rwUpdateLoadButtons();
+}
+
+/* 初始窗口就绪：状态机登记 + 入口按钮 + 对齐底部（与既开开会话在最新处的行为一致）。 */
+function rwInitWindow(payload) {
+    if (!rwState || !payload) return;
+    RenderWindowState.initFullChain(rwState, payload);
+    rwUpdateLoadButtons();
+    var anchor = document.getElementById('scroll-anchor');
+    if (anchor) anchor.scrollIntoView({ behavior: 'auto', block: 'end' });
+    reportWebScroll();
+}
+
+/* 分页响应：state 机校验 (session, generation, 未决请求)；stale 丢弃并清理已渲染节点。 */
+function rwPageResponse(payload) {
+    if (!rwState || !payload) return;
+    var req = { direction: payload.direction, boundaryId: payload.boundaryId };
+    var res = RenderWindowState.applyPage(rwState, req, payload);
+    if (res.stale) {
+        (payload.items || []).forEach(function(it) { rwRemoveMessageDom(it.id); });
+        rwUpdateLoadButtons();
+        return;
+    }
+    if (res.side === 'older') rwApplyOlder(res);
+    else rwApplyNewer(res);
+}
+
+/* 向上换页：锚点捕获 → 新页移到头部 → 裁尾 → 锚点恢复（误差≤2px）→ 入口更新。 */
+function rwApplyOlder(res) {
+    var anchor = rwCaptureAnchor();
+    var oldScroll = getScroller().scrollTop;
+    var firstExisting = chatContainer.querySelector('.message-wrapper');
+    res.addedIds.forEach(function(id) {
+        var el = document.getElementById(id);
+        if (el) chatContainer.insertBefore(el, firstExisting);
+    });
+    res.removedIds.forEach(rwRemoveMessageDom);
+    if (anchor) {
+        var el = document.getElementById(anchor.msgId);
+        if (el) {
+            var newTop = el.getBoundingClientRect().top + window.scrollY;
+            if (oldScroll <= 1) {
+                // 绝对顶部：停在顶部露出新页（自动模式会沿顶部继续补页）
+                getScroller().scrollTop = 0;
+            } else {
+                getScroller().scrollTop = oldScroll + (newTop - anchor.docTop);
+            }
+        }
+    }
+    rwUpdateLoadButtons();
+    reportWebScroll();
+    // 自动模式：停在顶部且还有旧页 → 沿顶部继续补页（pending 防并发，逐页推进）
+    if (rwState && rwState.mode === 'auto' && getScroller().scrollTop <= 1 &&
+        RenderWindowState.canRequest(rwState, 'older')) {
+        setTimeout(function() { if (typeof rwAutoCheck === 'function') rwAutoCheck(); }, 60);
+    }
+}
+
+/* 向下换页：新页已在尾部 → 裁头 → 锚点恢复（无跳动）。 */
+function rwApplyNewer(res) {
+    var anchor = rwCaptureAnchor();
+    var oldScroll = getScroller().scrollTop;
+    res.removedIds.forEach(rwRemoveMessageDom);
+    if (anchor) {
+        var el = document.getElementById(anchor.msgId);
+        if (el) {
+            var newTop = el.getBoundingClientRect().top + window.scrollY;
+            getScroller().scrollTop = oldScroll + (newTop - anchor.docTop);
+        }
+    }
+    rwUpdateLoadButtons();
+    reportWebScroll();
+}
+
+/* 新消息追加进窗口（发送用户消息 / 助手占位 / 切回续流）；超限裁旧端。
+ * chainIndex/chainLen 为 -1 表示未知（安全降级）。带 streaming 类的消息自动接管流式保护。 */
+function rwNoteLive(sessionId, generation, msgId, chainIndex, chainLen) {
+    if (!rwState || rwState.sessionId !== sessionId || rwState.generation !== generation) return;
+    if (chainLen !== undefined && chainLen !== null && chainLen >= 0) {
+        rwState.chainLen = chainLen | 0;
+    }
+    var ix = (chainIndex === undefined || chainIndex === null || chainIndex < 0) ? -1 : (chainIndex | 0);
+    var r = RenderWindowState.noteLive(rwState, msgId, ix);
+    var el = document.getElementById(msgId);
+    if (el && el.classList.contains('streaming')) {
+        RenderWindowState.noteStream(rwState, msgId);
+    }
+    (r.removedIds || []).forEach(rwRemoveMessageDom);
+    rwUpdateLoadButtons();
+}
+
+/* 发起换页请求（双引擎同构：QtWebChannel slot / WebView2 postMessage 同名方法）。 */
+function rwRequestPage(direction) {
+    if (!rwState) return;
+    var req = RenderWindowState.beginRequest(rwState, direction);
+    if (!req) return;
+    if (window.bridge && typeof window.bridge.onRequestWindowPage === 'function') {
+        window.bridge.onRequestWindowPage(rwState.sessionId, req.direction, req.boundaryId, rwState.generation);
+    }
+}
+
+/* 滚动驱动：双模式底部自动恢复新页；自动模式顶部自动加载旧页。 */
+function rwAutoCheck() {
+    if (!rwState) return;
+    if (RenderWindowState.canRequest(rwState, 'newer') && isNearBottom()) {
+        rwRequestPage('newer');
+    } else if (rwState.mode === 'auto' && getScroller().scrollTop <= 1 &&
+        RenderWindowState.canRequest(rwState, 'older')) {
+        rwRequestPage('older');
+    }
+}
+
+/* 锚点：换页前首个可见消息的 id + 文档坐标 top。 */
+function rwCaptureAnchor() {
+    var top = getScroller().scrollTop;
+    var bot = top + window.innerHeight;
+    var els = chatContainer.querySelectorAll('.message-wrapper');
+    for (var i = 0; i < els.length; i++) {
+        var r = els[i].getBoundingClientRect();
+        if (r.bottom > top && r.top < bot) {
+            return { msgId: els[i].id, docTop: r.top + window.scrollY, offset: Math.max(0, top - r.top) };
+        }
+    }
+    return null;
+}
+
+/* 从 DOM 移除一条消息并清理全部相关存储（活动流不受裁剪，状态机保证）。 */
+function rwRemoveMessageDom(msgId) {
+    var wrapper = document.getElementById(msgId);
+    if (wrapper) wrapper.remove();
+    delete messageBuffer[msgId];
+    delete longTextStore[msgId];
+    delete finalContentStore[msgId];
+    delete attachmentMetaStore[msgId];
+}
+
+/* 加载入口：固定在 chat-container 首/尾；无更多消息时隐藏。 */
+function rwEnsureLoadButtons() {
+    if (!document.getElementById('load-older')) {
+        var b = document.createElement('div');
+        b.id = 'load-older';
+        b.className = 'load-window-btn';
+        b.hidden = true;
+        b.innerText = '⌃ 加载更早消息';
+        b.addEventListener('click', function() { rwRequestPage('older'); });
+        chatContainer.appendChild(b);
+    }
+    if (!document.getElementById('load-newer')) {
+        var n = document.createElement('div');
+        n.id = 'load-newer';
+        n.className = 'load-window-btn';
+        n.hidden = true;
+        n.innerText = '⌄ 加载更新消息';
+        n.addEventListener('click', function() { rwRequestPage('newer'); });
+        chatContainer.appendChild(n);
+    }
+    chatContainer.insertBefore(document.getElementById('load-older'), chatContainer.firstChild);
+    chatContainer.appendChild(document.getElementById('load-newer'));
+}
+
+function rwUpdateLoadButtons() {
+    if (!rwState) return;
+    rwEnsureLoadButtons();
+    document.getElementById('load-older').hidden = !rwState.hasMoreOlder;
+    document.getElementById('load-newer').hidden = !rwState.hasMoreNewer;
+}
+
 // ==================== JS 引擎就绪标志 ====================
 window.jsReady = true;
 console.log('[JS]: 引擎已就绪');

ui/web/index.html

@@ -44,7 +44,7 @@
         </div>
     </div>
     
-    <!-- 聊天容器 -->
+    <!-- 聊天容器（🆕 P1-01：顶部/底部加载入口由 app.js 按需插入 chat-container 首/尾） -->
     <div id="chat-container"></div>
     
     <div id="scroll-anchor" style="height: 1px; margin-bottom: 150px;"></div>
@@ -63,7 +63,8 @@
                     onBranchSwitch: (x, d) => post("onBranchSwitch", [x, d]),
                     onDeleteMessageClicked: (x) => post("onDeleteMessageClicked", [x]),
                     onAttachmentClicked: (x) => post("onAttachmentClicked", [x]),
-                    onScrollChanged: (y, h, c) => post("onScrollChanged", [y, h, c])
+                    onScrollChanged: (y, h, c) => post("onScrollChanged", [y, h, c]),
+                    onRequestWindowPage: (s, d, b, g) => post("onRequestWindowPage", [s, d, b, g])
                 };
                 console.log("[JS] WebView2 桥接就绪，window.bridge 可用");
             } else {
@@ -76,7 +77,9 @@
         });
     </script>
     
-    <!-- 主逻辑脚本 -->
+    <!-- 🌟 主逻辑脚本 -->
+    <!-- 🆕 P1-01 渲染窗口状态机（DOM 无关；须在 app.js 之前） -->
+    <script src="render_window.js"></script>
     <script src="app.js"></script>
 </body>
 </html>

ui/web/render_window.js

@@ -0,0 +1,304 @@
+/* ui/web/render_window.js — P1-01 双向消息渲染窗口：DOM 无关状态机
+ *
+ * 同时可被 Node（tests/test_render_window.js）与浏览器（index.html）加载。
+ * 不触碰任何 DOM：几何量以参数传入，输出「动作计划」（加入/移除/滚动增量），
+ * 由 app.js 的 DOM 层执行。消息描述符渲染由 Python 经既有桥接调用完成，
+ * 本模块只维护窗口游标（已加载消息 id 序列 + 链内下标）。
+ *
+ * 配置规则（与 core/config_paths.render_window_settings 一致）：
+ *   size：只接受非布尔整数 10..200；缺失/布尔/字符串/小数/零/负数/越界 → 静默回落 40；
+ *   mode：只接受 "auto"/"manual"，否则回落 "auto"。
+ *
+ * 窗口模型：
+ *   order —— 已加载（= 当前窗口）的消息 id 序列，长度恒 ≤ size；
+ *   indexById —— id → 链内下标（Python 页载荷给出；未持久化的活动消息为 -1）；
+ *   hiddenOlder/hiddenNewer —— 窗口之外、链中仍存在的消息数（按链内下标推导）；
+ *   一次换页 = 「加入一端、裁掉另一端」；活动流式消息计入上限、永不裁剪；
+ *   请求/响应携带 (sessionId, generation)；clear() 本地递增代次，
+ *   initFullChain() 用 Python 代次重同步；不匹配的旧载荷一律 stale。
+ */
+(function (root, factory) {
+    if (typeof module === 'object' && module.exports) module.exports = factory();
+    else root.RenderWindowState = factory();
+}(typeof self !== 'undefined' ? self : this, function () {
+    'use strict';
+
+    var MIN_SIZE = 10, MAX_SIZE = 200, DEFAULT_SIZE = 40;
+
+    function isInt(v) {
+        return typeof v === 'number' && isFinite(v) && Math.floor(v) === v;
+    }
+
+    function validSize(v) {
+        return isInt(v) && v >= MIN_SIZE && v <= MAX_SIZE;
+    }
+
+    function normalizeConfig(cfg) {
+        var c = (cfg && typeof cfg === 'object') ? cfg : {};
+        var size = validSize(c.render_window_size) ? c.render_window_size : DEFAULT_SIZE;
+        var mode = (c.render_window_mode === 'auto' || c.render_window_mode === 'manual')
+            ? c.render_window_mode : 'auto';
+        return { mode: mode, size: size };
+    }
+
+    function create(cfg) {
+        var c = normalizeConfig(cfg);
+        return {
+            mode: c.mode,
+            size: c.size,
+            sessionId: null,
+            generation: 0,
+            order: [],            // 窗口内 id（旧 → 新），长度 ≤ size
+            indexById: {},        // id → 链内下标（-1 = 未持久化）
+            chainLen: 0,          // 最近一次载荷给出的可见链长度
+            hiddenOlder: 0,       // 窗口之上链中消息数
+            hiddenNewer: 0,       // 窗口之下链中消息数
+            hasMoreOlder: false,
+            hasMoreNewer: false,
+            pending: null,        // {direction, boundaryId, generation} | null
+            activeStreamId: null, // 活动流式消息 id（计入上限、永不裁剪）
+            followBottom: false
+        };
+    }
+
+    function windowIds(st) { return st.order.slice(); }
+
+    function isFull(st) { return st.order.length >= st.size; }
+
+    function canRequest(st, direction) {
+        if (!st || st.pending || st.order.length === 0) return false;
+        return direction === 'older' ? st.hasMoreOlder : st.hasMoreNewer;
+    }
+
+    /* 登记一次换页请求，返回 {direction, boundaryId}；boundary 为窗口对应端的消息 id。 */
+    function beginRequest(st, direction) {
+        if (!canRequest(st, direction)) return null;
+        var boundaryId = direction === 'older' ? st.order[0] : st.order[st.order.length - 1];
+        st.pending = { direction: direction, boundaryId: boundaryId, generation: st.generation };
+        return { direction: direction, boundaryId: boundaryId };
+    }
+
+    function num(v) { return (isInt(v) && v >= 0) ? v : 0; }
+
+    /* 按链内下标推导两端隐藏计数。
+     * 未持久化消息（index=-1）只可能出现在较新一端：
+     *   hiddenOlder = 窗口最旧 id 的下标（最旧端必为已持久化消息）
+     *   hiddenNewer = chainLen - 1 - 已知最大下标 - 其后的未持久化条数 */
+    function recompute(st) {
+        var minI = null, maxI = null, maxPos = -1, unknownAfterMax = 0;
+        for (var i = 0; i < st.order.length; i++) {
+            var ix = st.indexById[st.order[i]];
+            if (ix === undefined || ix < 0) continue;
+            if (minI === null || ix < minI) minI = ix;
+            if (maxI === null || ix > maxI) { maxI = ix; maxPos = i; }
+        }
+        for (var j = maxPos + 1; j < st.order.length; j++) {
+            var jx = st.indexById[st.order[j]];
+            if (jx === undefined || jx < 0) unknownAfterMax++;
+        }
+        if (minI === null) {
+            st.hiddenOlder = 0;
+            st.hiddenNewer = 0;
+            st.hasMoreOlder = false;
+            st.hasMoreNewer = false;
+            return;
+        }
+        st.hiddenOlder = minI;
+        st.hiddenNewer = Math.max(0, st.chainLen - 1 - maxI - unknownAfterMax);
+        st.hasMoreOlder = st.hiddenOlder > 0;
+        st.hasMoreNewer = st.hiddenNewer > 0;
+    }
+
+    /* 从较新一端裁剪，直到长度 ≤ size；活动流永不裁剪。 */
+    function trimTail(st, removed) {
+        while (st.order.length > st.size) {
+            var i = st.order.length - 1;
+            if (st.order[i] === st.activeStreamId) { i--; } // 跳过尾部活动流，裁次新一条
+            if (i < 0) break; // 病态兜底：整窗都是活动流（不可能，仅一条流）
+            removed.push(st.order.splice(i, 1)[0]);
+            delete st.indexById[removed[removed.length - 1]];
+        }
+    }
+
+    /* 从较旧一端裁剪，直到长度 ≤ size；活动流永不裁剪。 */
+    function trimHead(st, removed) {
+        while (st.order.length > st.size) {
+            var i = 0;
+            if (st.order[i] === st.activeStreamId) { i = 1; }
+            if (i >= st.order.length) break;
+            removed.push(st.order.splice(i, 1)[0]);
+            delete st.indexById[removed[removed.length - 1]];
+        }
+    }
+
+    function absorb(st, items) {
+        var added = [];
+        for (var i = 0; i < items.length; i++) {
+            var d = items[i];
+            if (!d || !d.id || st.order.indexOf(d.id) >= 0) continue;
+            st.order.push(d.id);
+            st.indexById[d.id] = (d.chainIndex === undefined || d.chainIndex < 0) ? -1 : d.chainIndex;
+            added.push(d.id);
+        }
+        return added;
+    }
+
+    /* 初始窗口：最新 size 条（Python 负责截取）。
+     * payload = {sessionId, generation, chainLen, items:[{id, chainIndex}]}
+     * 用 Python 代次重同步（覆盖 clear() 的本地自增）。 */
+    function initFullChain(st, payload) {
+        st.sessionId = payload.sessionId;
+        st.generation = num(payload.generation);
+        st.order = [];
+        st.indexById = {};
+        st.pending = null;
+        st.activeStreamId = null;
+        st.followBottom = false;
+        st.chainLen = num(payload.chainLen);
+        absorb(st, payload.items || []);
+        trimTail(st, []); // 防御：载荷超过 size 时保留最新端
+        recompute(st);
+        return { window: windowIds(st), hasMoreOlder: st.hasMoreOlder };
+    }
+
+    /* 收到 Python 页载荷。
+     * req     = beginRequest 的返回值（或 {direction, boundaryId}）
+     * payload = {sessionId, generation, boundaryId, direction, chainLen,
+     *            items:[{id, chainIndex}]}
+     * 返回 {stale:true} 或
+     *      {side, addedIds, removedIds, hiddenOlder, hiddenNewer,
+     *       hasMoreOlder, hasMoreNewer}
+     *      （DOM 层：addedIds 已渲染、加到 side 端；removedIds 从 DOM 移除；
+     *       加载入口可见性按 hasMore* 更新） */
+    function applyPage(st, req, payload) {
+        if (!st || !req || !payload) return { stale: true };
+        if (payload.sessionId !== st.sessionId ||
+            payload.generation !== st.generation) {
+            st.pending = null;
+            return { stale: true };
+        }
+        if (!st.pending ||
+            st.pending.direction !== req.direction ||
+            st.pending.boundaryId !== req.boundaryId) {
+            // 无匹配的未决请求（代次已推进/窗口已变/重复投递）→ 丢弃
+            st.pending = null;
+            return { stale: true };
+        }
+        st.pending = null;
+
+        var items = payload.items || [];
+        var removedIds = [];
+        var addedIds = absorb(st, items);
+        if (req.direction === 'older') {
+            // absorb 追加在尾部，这里把新页挪到头部（保持 旧→新 顺序）
+            var head = st.order.splice(st.order.length - addedIds.length, addedIds.length);
+            st.order = head.concat(st.order);
+            trimTail(st, removedIds);
+        } else {
+            trimHead(st, removedIds);
+        }
+        st.chainLen = num(payload.chainLen);
+        recompute(st);
+        return {
+            side: req.direction,
+            addedIds: addedIds,
+            removedIds: removedIds,
+            hiddenOlder: st.hiddenOlder,
+            hiddenNewer: st.hiddenNewer,
+            hasMoreOlder: st.hasMoreOlder,
+            hasMoreNewer: st.hasMoreNewer
+        };
+    }
+
+    /* 切会话 / 清屏 / 切分支：游标、缓存、未决请求、代次全部清空（本地自增使
+     * 旧载荷失效）；已注入的配置模式与大小保持不变。下一次 initFullChain
+     * 用 Python 代次重同步。 */
+    function clear(st) {
+        st.generation += 1;
+        st.sessionId = null;
+        st.order = [];
+        st.indexById = {};
+        st.chainLen = 0;
+        st.hiddenOlder = 0;
+        st.hiddenNewer = 0;
+        st.hasMoreOlder = false;
+        st.hasMoreNewer = false;
+        st.pending = null;
+        st.activeStreamId = null;
+        st.followBottom = false;
+        return st;
+    }
+
+    /* 活动流开始：该消息计入上限、永不被裁剪。 */
+    function noteStream(st, msgId) {
+        st.activeStreamId = msgId;
+        st.followBottom = true;
+    }
+
+    function streamFinished(st, msgId) {
+        if (st.activeStreamId === msgId) {
+            st.activeStreamId = null;
+            st.followBottom = false;
+        }
+    }
+
+    /* 新消息追加到窗口较新一端（发送用户消息 / 助手占位 / 切回续流）。
+     * 超出 size 时从较旧一端裁剪（活动流除外），流式消息计入上限。 */
+    function noteLive(st, msgId, chainIndex) {
+        if (!st || st.sessionId === null || !msgId) return { added: false };
+        if (st.order.indexOf(msgId) >= 0) {
+            if (chainIndex !== undefined && chainIndex >= 0) st.indexById[msgId] = chainIndex;
+            recompute(st);
+            return { added: false };
+        }
+        st.order.push(msgId);
+        st.indexById[msgId] = (chainIndex === undefined || chainIndex < 0) ? -1 : chainIndex;
+        var removed = [];
+        trimHead(st, removed);
+        recompute(st);
+        return { added: true, removedIds: removed };
+    }
+
+    /* ---------- 锚点几何（纯数学；DOM 层传入测量值） ---------- */
+
+    /* 首个可见消息 + 像素偏移。
+     * entries: [{id, top, height}]（文档坐标，DOM 顺序 旧→新）
+     * viewportTop/viewportBottom: 视口在文档坐标中的范围
+     * 返回 {msgId, offset}；无可见消息 → null */
+    function computeAnchor(entries, viewportTop, viewportBottom) {
+        for (var i = 0; i < entries.length; i++) {
+            var e = entries[i];
+            if (e.top + e.height > viewportTop && e.top < viewportBottom) {
+                return { msgId: e.id, offset: Math.max(0, viewportTop - e.top) };
+            }
+        }
+        return null;
+    }
+
+    /* 换页后的滚动增量：把换页前记录的 anchor 文档 top（rectTopBefore）
+     * 对齐到换页后实测的 top（rectTopAfter）。DOM 层用两次真实测量，
+     * 误差只来自亚像素取整，≤ 2 px。 */
+    function scrollDeltaFromRects(rectTopBefore, rectTopAfter) {
+        return rectTopAfter - rectTopBefore;
+    }
+
+    return {
+        MIN_SIZE: MIN_SIZE,
+        MAX_SIZE: MAX_SIZE,
+        DEFAULT_SIZE: DEFAULT_SIZE,
+        normalizeConfig: normalizeConfig,
+        create: create,
+        windowIds: windowIds,
+        isFull: isFull,
+        canRequest: canRequest,
+        beginRequest: beginRequest,
+        applyPage: applyPage,
+        initFullChain: initFullChain,
+        clear: clear,
+        noteStream: noteStream,
+        streamFinished: streamFinished,
+        noteLive: noteLive,
+        computeAnchor: computeAnchor,
+        scrollDeltaFromRects: scrollDeltaFromRects
+    };
+}));

ui/web/style.css

@@ -900,3 +900,33 @@ body, html {
 .message-wrapper.assistant .reply-content .md-segment + .md-segment {
     margin-top: 6px;
 }
+
+/* ==================== 🆕 P1-01 渲染窗口：加载入口按钮 ==================== */
+/* 上/下两端的「加载更多」入口：无边框浅灰胶囊，居中；无更多消息时由 JS 隐藏 */
+.load-window-btn {
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    width: 220px;
+    margin: 14px auto;
+    padding: 6px 14px;
+    font-size: 12px;
+    color: #666;
+    background: #f4f4f6;
+    border: 1px solid #e3e3e8;
+    border-radius: 999px;
+    cursor: pointer;
+    user-select: none;
+    transition: background 0.15s ease, color 0.15s ease;
+}
+.load-window-btn:hover {
+    background: #eaeaf0;
+    color: #333;
+}
+.load-window-btn[hidden] {
+    display: none;
+}
+/* 底部入口与 scroll-anchor 的间距（scroll-anchor 自带 150px margin） */
+#load-newer {
+    margin-bottom: 4px;
+}