fix(consult): drop traces, budget checkpoints, silent summary inherit

BUG-729: dropped history rounds leave an omission marker in the model-visible summary slot.
BUG-730: checkpoint threshold is 0.4 of historyBudgetChars (128k still 16,000).
BUG-731: session_full new chat copies owned context_summary on the server; clients send only continued_from_session_id.

CHANGELOG.md

@@ -1,5 +1,9 @@
 # 印度占星 Skill 更新日志
 
+## 2026-09-16 — 对话写满后开新对话会静默带上之前的摘要
+
+普通咨询写满、点「开新对话」之后，服务端会把上一场的会话摘要拷进新对话，界面上看不出差别。进不了窗口的更早几轮，模型会看到省略说明，不再当成没发生过。Skill 版本不变。
+
 ## 2026-09-16 — 同一天再问同一张盘，不再重复等外部证据
 
 普通聊天同一张盘、同一天里再问，外部证据直接用已经取到的，不再每轮等外网。隔了一天会先用最多七天内的旧证据马上回答，后台再刷新；「深入看今日」仍然只要当天的。西洋盘整包不再塞进每一轮的回答里，压缩后的西洋层还在。Skill 版本不变。

docs/BUG_HISTORY.md

@@ -11332,3 +11332,51 @@
 - 相关记录：BUG-727
 - 复发自：无
 - 修复版本：待发布
+
+## BUG-729 | 咨询历史丢掉整轮时模型看不见任何痕迹
+
+- 状态：resolved
+- 首次发现：2026-09-15
+- 最近更新：2026-09-16
+- 影响面：`consultationHistoryWindow`、`consultationUserTurnContent`、`POST /api/consult`
+- 用户现象：历史超过模型预算后，追问「刚才你说的那个时间」时模型当成从没说过。单条超长会写「省略 N 字」，整轮被丢掉时什么都不留。
+- 触发条件：普通咨询多轮之后，尾巴字符数超过当前模型的历史预算，窗口从最旧整条丢弃。
+- 根因：`droppedCount` 算出来了，`route.ts` 只取 `.tail`。BUG-555 的防复发只写了「不得再按固定 12 条 × 头部截断静默砍结论」，整轮丢弃不在字面里，所以没拦住。
+- 修复：`droppedCount > 0` 时在摘要槽追加与 `omissionMarker` 同风格的说明。有摘要时写「更早的 N 轮问答已并入上面的会话摘要」；没有摘要时诚实写结论尚未并入。`droppedCount === 0` 不加这句话。
+- 验证：超预算历史的模型可见文本含丢弃说明且轮数等于 `droppedCount`；零丢弃不加这句话；源码合同断言 `route.ts` 读取 `historyWindow.droppedCount`。
+- 防复发：咨询历史任何形式的丢弃（截断单条、丢整轮）都必须在模型可见文本里留痕。
+- 相关记录：BUG-555
+- 复发自：BUG-555（防复发只覆盖头部截断）
+- 修复版本：待发布
+
+## BUG-730 | 写摘要的阈值写死 16,000，追不上按窗口算出的历史预算
+
+- 状态：resolved
+- 首次发现：2026-09-15
+- 最近更新：2026-09-16
+- 影响面：`historyBudgetChars`、`consultationHistoryCheckpointChars`、`shouldCheckpoint`、`checkpointSessionContextSummary`
+- 用户现象：后台上架中等上下文窗口的模型后，每轮静默丢掉最老的几轮问答，摘要却还没开始写。
+- 触发条件：模型 `context_window` 低于约 70,667（例如 64k / 32k）。历史预算已经小于写死的 16,000 字阈值。
+- 根因：`shouldCheckpoint` 用常量 16,000，`consultationHistoryWindow` 用 `historyBudgetChars()`。两个数各写各的，没有「阈值必须低于预算」的断言。
+- 修复：阈值改为预算的 0.4（默认 128k 窗口仍是 16,000）。运行时断言阈值 < 预算。检查点把会话模型的 `contextWindow` 传进去。
+- 验证：表驱动覆盖 200k / 128k / 64k / 32k / null，逐条 `checkpoint < budget`；128k 仍为 16,000。
+- 防复发：触发摘要的阈值必须由历史预算派生，并由一条断言钉死「阈值 < 预算」在所有合法上下文窗口下成立。
+- 相关记录：BUG-555
+- 复发自：BUG-555（检查点阈值与窗口预算未绑在一起）
+- 修复版本：待发布
+
+## BUG-731 | 对话写满后开新对话不继承服务端已有的会话摘要
+
+- 状态：resolved
+- 首次发现：2026-09-15
+- 最近更新：2026-09-16
+- 影响面：`chatSessionCreateSchema`、`POST /api/sessions`、`continueInNewChat`、`startNewChat`
+- 用户现象：这段对话已写满、点「开新对话」之后，模型对刚才的结论一无所知，用户被要求从零开始。
+- 触发条件：`append_consultation_question` 返回 `session_full`，客户端走「开新对话」。
+- 根因：新会话是空的。`context_summary` 不在列表 GET 列里，创建合同也不接收它。即便前端想带，也没有合法入口。
+- 修复：创建合同增加可选 `continued_from_session_id`（保持 `.strict()`，不加 `context_summary`）。服务端按当前用户读源会话摘要，读到才写入新行；读不到、不属于该用户、或为空都静默跳过，仍返回 201。写满出口把当前会话 id 带进创建请求。界面不加「接着上次聊」之类提示。
+- 验证：带来源 id 时新行摘要等于源会话；源会话属于别人时新行无摘要且 201；源码合同断言创建 schema 没有 `context_summary` 字段；写满后「开新对话」没有新增提示文案。
+- 防复发：会话满员后的「开新对话」出口必须由服务端继承 `context_summary`；摘要文本任何时候都不得由客户端提供。不得把 `messages` 加回列表 GET。
+- 相关记录：BUG-464、BUG-555
+- 复发自：无
+- 修复版本：待发布

docs/tasks/PROGRESS-consultation-context-memory-20260915.md

@@ -0,0 +1,60 @@
+# PROGRESS · 普通聊天的三条记忆缺口（2026-09-16）
+
+工作树：`.worktrees/consultation-context-memory-20260915`  
+分支：`codex/consultation-context-memory-20260915`  
+任务书基线：`origin/staging` @ `6b3248bf`；开工时本 worktree 在 `11893c7f`（任务书已合入 staging）。  
+本机 Windows。Skill **未 bump**。未改 `frontend/src/app/page.tsx`、数据库、依赖。
+
+开工核对：`docs/BUG_HISTORY.md` 最大号 **BUG-720**。校正四单预占 721–726、external-evidence-cache 预占 727/728，本单使用预占 **BUG-729 / 730 / 731**，无冲突。
+
+## 任务状态
+
+| 任务 | 状态 | BUG |
+| --- | --- | --- |
+| 5.2 写摘要阈值跟着预算走 | 完成 | BUG-730 |
+| 5.1 丢整轮必须留痕 | 完成 | BUG-729 |
+| 5.3 写满时静默继承摘要 | 完成 | BUG-731 |
+| 5.4 Bug 历史 | 完成 | 729/730/731 |
+
+## 实现要点
+
+- **BUG-730**：删除写死的 `CONSULTATION_HISTORY_TAIL_MAX_CHARS = 16_000`。新函数 `consultationHistoryCheckpointChars(window)` = `floor(historyBudgetChars(window) × 0.4)`，并运行时断言阈值 < 预算。128k 仍是 16,000。`shouldCheckpoint` / `checkpointSessionContextSummary` 吃 `contextWindow`；consult 把会话模型窗口传进去。
+- **BUG-729**：`droppedCount > 0` 时在 `consultationUserTurnContent` 的摘要槽追加与 `omissionMarker` 同风格的说明。有摘要：「更早的 N 轮问答已并入上面的会话摘要」；无摘要：「更早的 N 轮问答未能进入本轮上下文，结论尚未并入会话摘要」。`droppedCount === 0` 不加。`route.ts` 四条用户回合都读 `historyWindow.droppedCount`。
+- **BUG-731**：`chatSessionCreateSchema` 增加可选 `continued_from_session_id`（保持 `.strict()`，**不加** `context_summary`）。`POST /api/sessions` 按当前用户读源会话摘要，读到才写入新行；读不到 / 别人的 / 空都静默跳过，仍 201。`continueInNewChat` 把当前会话 id 传给 `startNewChat`。界面无新文案。
+
+未改摘要机制本身（800 汉字、15 秒 ref 计时器、乐观并发、结算后异步）。未用 `AbortSignal.timeout()` 替换摘要超时。未把 `messages` 加回列表 GET。未动数据库。
+
+## 既有断言改动
+
+| 文件 | 原值 | 新值 | 原因 |
+| --- | --- | --- | --- |
+| `session-context-summary.test.ts` | `CONSULTATION_HISTORY_TAIL_MAX_CHARS === 16_000`；`shouldCheckpoint` 只测 15_999 / 16_001 | `consultationHistoryCheckpointChars(128_000) === 16_000`；另测 64k 阈值 2_400 | BUG-730：阈值由预算派生，128k 行为与改前一致 |
+| `chat-session-write.test.ts` 源码合同 | `const { id, updated_at: _ignoredClientClock, ...values } = parsed.data` | 另拆 `continued_from_session_id`，不随 values 插入 | 该字段不是表列 |
+| `chat-session-url.test.ts` / `composer-isolation-contract.test.ts` | 切片起点 `async function startNewChat()` | `async function startNewChat(` | 可带来源会话 id |
+| `consultation-context-cache-contract.test.ts` | 检查点不传窗口 | 传 `sessionContextWindow`；历史文件不得再出现字面量 `16_000` | BUG-730 |
+
+128k 检查点阈值：**原值 16,000 / 新值 16,000 / 原因** 比例 0.4 × 预算 40,000。未弱化其它既有断言。
+
+## 测试
+
+| 命令 | 结果 |
+| --- | --- |
+| `./node_modules/.bin/tsc --noEmit` | **0 错** |
+| `npm run lint` | **0 error**（119 条既有 warning；本单未新增 error） |
+| 本单相关 `npx tsx --test`（history / summary / cache contract / chat-session-write / authority / url / composer-isolation / consultation-context） | **69 pass / 0 fail** |
+| `npx tsx --test tests/consultation*.test.ts tests/chat-session-*.test.ts tests/session-*.test.ts` | 264 项 / 252 pass / **12 fail**：3 个文件级失败 + 9 条 methodology，全是 Windows `SkillPackageRegistryError`（EPERM symlink），与本单文件无关 |
+| `npm test`（`tests/*.test.ts tests/*.test.tsx`） | `# tests 3110 / # pass 3023 / # fail 73 / # skipped 14`。失败清单不含本单文件。对照近期同机 `PROGRESS-chart-page-blocking-open-20260915.md` 的 fail **73**，**零新增失败** |
+| `page.tsx` | 未改 |
+| `npm run build` | compile + TypeScript 过；Collecting page data 死在既有 `SkillPackageRegistryError`（EPERM symlink `/api/daily-starlanguage`），与本单无关。未能从本机构建表确认 `/` 的 `○ Static` 与首屏 gzip。源码：`page.tsx` 无 `force-dynamic`；既有合同「home stays a client-read query on a static route」本单相关套件已绿 |
+
+## 环境缺口
+
+- 本机 Windows 无开发者模式 symlink：`skill-package-registry` 建 live runtime alias 报 EPERM。因此 `next build` 收集页面数据失败；若干 consult/methodology/skill-binding 测试整文件红。Linux CI / staging 不受影响。
+- 无 Docker：`tests/database-*.test.ts` 照常红，与基线同类。
+- 无登录态、无 Chrome：写满后「开新对话」的静默继承未做浏览器走查。界面无新文案，源码合同已锁「开新对话」按钮与禁止「接着上次聊」类句子。
+
+## 收尾限制
+
+- 摘要失败仍只 `console.warn("session context summary failed")`，不打印摘要正文。
+- 侧栏「新建对话」不带 `continued_from_session_id`，只有写满出口的「开新对话」会静默继承。
+- 源会话属于别人或没有摘要时新行 `context_summary` 为空，接口仍 201。

docs/tasks/README.md

@@ -239,7 +239,7 @@
 | `TASK-rectification-settled-render-split-20260915.md` | — | **前端性能单（独占校正会话组件，可并行）**：`rectification-agentic-chat.tsx` 1973 行、`useMemo` 0 个、`memo` 0 个，`messages.map` 内联在组件体里且逐条新建时间轴数组与 choice card，`ChatMessageRow` 无 memo、结算态 Markdown 走没有缓存的 `renderProse`。流式每帧（~60/s）重渲整条会话并重跑每条已结算消息的 Markdown。BUG-473 在本文件只落地了 `stream-frame-buffer`，咨询面的 `SettledMessageList` + `HistoryMessageEntry` 拆分没有跟过来。**零行为变化**；验收必须有按帧驱动的渲染计数断言（照 `home-streaming-render-split.test.ts`）。BUG 段 725 | 待领取 | — |
 | `TASK-rectification-request-dossier-cache-20260915.md` | — | **低风险单，串行在 failure-attribution 之后（同改 `route.ts`）**：一轮 Agent 对话实测取 3.44 次整份 Case 档案（点选题 2.07 次），全仓约 40 个调用点、请求内零缓存；档案是「最近 50 轮 turns + 全部 evidence + 合成收据」的大 jsonb。做法是包装 `accounting` 客户端做**写即失效**的请求作用域缓存（两个只读投影命中缓存，其余任何 RPC 先清空再转发），**零调用点改动**。不得做成「请求内只读一次」——档案在请求内会变。BUG 段 726 | 待领取 | — |
 | `TASK-consultation-external-evidence-cache-20260915.md` | `PROGRESS-consultation-external-evidence-cache-20260915.md` | **普通聊天性能单（Python；2026-09-15 产品拍板改为排在 api-server-decomposition 之前）**：每轮每域同步等外网，cProfile 前三名全是 `api.vedastro.org` 的 HTTPS 往返（0.801 + 0.786 + 0.206 s），本地 swisseph 只有 0.022 s。三个护栏数字凑不齐：前台等 1.5 s、后台跑 8 s、线程池只有 2 个 worker，且超时**不 cancel** → 每 4 秒一轮就长期饱和，之后每轮白等再拿 `official_blocked`（BUG-727）。另 `western_evidence_packet` 122 KB 前端零读取点（BUG-728）。**产品定案**：按「出生数据+岁差+交点+UTC 日期」缓存（与引擎 `_official_snapshot_reference_date` 同键，否决自定 TTL），同日 0 等待 / 跨日先用旧的（≤7 天）后台刷新 / `daily_starlanguage` 要求当天 / 冷启动才走 1.5 s。**不许「干脆不调」——那会重开 BUG-301。** 另含 staging 单域耗时实测单（代码注释里的 21 s 与本机 0.5 s 差 40 倍，三域上限就是从它推的）。BUG 段 727–728 | 待验收 | `codex/consultation-external-evidence-cache-20260915` |
-| `TASK-consultation-context-memory-20260915.md` | — | **记忆三缺口（TS，可并行）**：历史超预算时从最老整轮丢弃，`droppedCount` 算了却**全仓零读取点**，模型不知道少看了几轮——单条截断有「省略 N 字」标记，整轮丢弃没有（BUG-729，BUG-555 防复发只写了「头部截断」所以漏网）；写摘要阈值写死 16,000，历史预算却是 `clamp((窗口−60k)×1.5, 4k, 40k)`，窗口 < **70,667** 时预算低于阈值 → 每轮静默丢（BUG-730，后台上架中等窗口模型即触发）；写满时服务端存着摘要，`continueInNewChat` 只带问题不带摘要，而 `context_summary` 根本不在任何会话接口的列里（BUG-731）。**产品定案：静默继承**，且摘要文本永远不许由客户端提供（`chatSessionCreateSchema` 只收来源会话 uuid）。BUG 段 729–731 | 待领取 | — |
+| `TASK-consultation-context-memory-20260915.md` | `PROGRESS-consultation-context-memory-20260915.md` | **记忆三缺口（TS，可并行）**：历史超预算时从最老整轮丢弃，`droppedCount` 算了却**全仓零读取点**，模型不知道少看了几轮——单条截断有「省略 N 字」标记，整轮丢弃没有（BUG-729，BUG-555 防复发只写了「头部截断」所以漏网）；写摘要阈值写死 16,000，历史预算却是 `clamp((窗口−60k)×1.5, 4k, 40k)`，窗口 < **70,667** 时预算低于阈值 → 每轮静默丢（BUG-730，后台上架中等窗口模型即触发）；写满时服务端存着摘要，`continueInNewChat` 只带问题不带摘要，而 `context_summary` 根本不在任何会话接口的列里（BUG-731）。**产品定案：静默继承**，且摘要文本永远不许由客户端提供（`chatSessionCreateSchema` 只收来源会话 uuid）。BUG 段 729–731 | 待验收 | `codex/consultation-context-memory-20260915` |
 | `TASK-consultation-session-capacity-20260915.md` | — | **对话上限单（一份迁移，可并行；不碰 route.ts）**：`append_consultation_question` 的 200,000 字符额度里，`thinkingText`(≤4,000) + `thinkingSections`(实测 1,521/2,243/2,977) 占一半以上，而 `techniqueTruth`/`workflowReceipt`/`agentExecutionReceipt` 照样入库却不计入——同一条上限身兼二职且两职都没做好，约 **19 轮** 就「已写满」（200 条那档永远碰不到）。**产品定案：思考文本不计入**，额度只数用户读得到的正文（约 19 → 约 50 轮），另设一条按 `length(elem::text)` 把全部字段算全的物理上限（算式取 1,000,000，写进迁移注释）护住数据库行；两档都返回同一个 `session_full`。保留 advisory lock / 幂等 / 满员拒绝（BUG-464 防复发）。BUG 段 732 | 待领取 | — |
 | `TASK-freeze-metric-change-20260915.md` | — | **规则单（后面两单的前置，无 BUG 号）**：两条增长冻结余量都用完（`page.tsx` 1,951/1,951 余 **0**；`jyotish_api_server.py` 11,334/11,363 余 **29**），冻结从「逼新代码往外走」退化成「拦路」。实证：`page.tsx` 行数砍 59% 但 `Home()` 的 `useState` 从 56 涨到 **66**（拆的是代码不是状态）；api server **225 个类方法只有 12 处真碰 HTTP 上下文**，4 处 `__new__` 伪造空壳就是这么来的。**产品拍板换口径**：主门改成「`Home()` 的 useState/useRef 不得增长」与「类方法数 + `__new__` 计数不得增长」，行数降级为粗护栏；**同时推翻 §6「参数式 hook 内部保持 0 个 React hook」**（那正是状态搬不走的原因）。改 `AGENTS.md` §6 + 两个合同测试，不碰业务代码 | 待领取 | — |
 | `TASK-home-state-lowering-20260915.md` | — | **page.tsx 状态下沉第一簇（串行在 freeze-metric-change + C2 + R3 之后）**：66 个 state 里 `rectification*` 占 **15** 个，而它们服务的 `<ConversationalBirthTimeRectification>` 本来就是 `dynamic()` 懒加载子树、挂着 24 个 props；`useRectificationSurface` 要解构约 56 个参数。把这簇搬进子树，`Home()` 的 useState 从 66 降到 ≤ 53。**零行为变化**；第一步必须先把 15 个逐个分类（只服务子树 / 外壳也要读）。产品否决了 Context Provider 与外部 store 两条路。不占 BUG 号 | 待领取 | — |

frontend/src/app/api/consult/route.ts

@@ -330,6 +330,7 @@ export async function POST(request: Request) {
       { status: 503 },
     );
   }
+  const sessionContextWindow = sessionModel.contextWindow;
 
   if (parsed.data.entrypoint === "birth_time_rectification") {
     return NextResponse.json(
@@ -353,7 +354,7 @@ export async function POST(request: Request) {
   // Client `history` stays in the request schema for old bundles and is not read.
   const contextSummary = parseSessionContextSummary(chatSession.context_summary);
   const historyWindow = consultationHistoryWindow(chatSession.messages, contextSummary, {
-    contextWindow: sessionModel.contextWindow,
+    contextWindow: sessionContextWindow,
   });
   const storedHistory = historyWindow.tail;
   const userControlledPrompt = [
@@ -596,6 +597,7 @@ export async function POST(request: Request) {
       await checkpointSessionContextSummary({
         messages: sessionRow.messages,
         summary: sessionRow.context_summary,
+        contextWindow: sessionContextWindow,
         generateText: (prompt, signal) => generateSessionContextSummaryText(summaryModel, prompt, signal),
         update: async (summary, seenUpdatedAt) => {
           let query = supabase.from("chat_sessions")
@@ -875,6 +877,7 @@ export async function POST(request: Request) {
             instruction: modeInstruction,
             extra: generalDailyContextPrompt(generalDailyContext),
             summaryText: historyWindow.summaryText,
+            droppedCount: historyWindow.droppedCount,
             question: resolvedQuestion.modelQuestion,
           }),
         },
@@ -1271,6 +1274,7 @@ export async function POST(request: Request) {
           instruction: generalNoMinuteInstruction(Boolean(generalDailyContext)),
           extra: generalDailyContextPrompt(generalDailyContext),
           summaryText: historyWindow.summaryText,
+          droppedCount: historyWindow.droppedCount,
           question: resolvedQuestion.modelQuestion,
         }),
       },
@@ -1355,6 +1359,7 @@ export async function POST(request: Request) {
           name,
           instruction: "先用 3–6 句口语直接回答下面的问题，不要加标题；形状为一句结论、2–3 条短要点（每条完整句子、不超过 30 字）、一句下一步，总量不超过 400 字；然后再按 skill Level 2 骨架写：原始结构、六步宫位、Yoga 表、时机、综合、文末技法审计表，最后才是现代生活。骨架不可省略。星盘事实只使用系统里已经注入的计算结果，不要复述内部字段、JSON 或再跑一遍咨询流程。",
           summaryText: historyWindow.summaryText,
+          droppedCount: historyWindow.droppedCount,
           question: resolvedQuestion.modelQuestion,
         }),
       },
@@ -1379,6 +1384,7 @@ export async function POST(request: Request) {
             name,
             instruction: "先用 3–6 句口语直接回答下面的问题，不要加标题；形状为一句结论、2–3 条短要点（每条完整句子、不超过 30 字）、一句下一步，总量不超过 400 字；然后再按 skill Level 2 骨架写：原始结构、六步宫位、Yoga 表、时机、综合、文末技法审计表，最后才是现代生活。骨架不可省略。星盘事实只使用系统里已经注入的计算结果，不要复述内部字段、JSON 或再跑一遍咨询流程。",
             summaryText: historyWindow.summaryText,
+            droppedCount: historyWindow.droppedCount,
             question: resolvedQuestion.modelQuestion,
           }),
         },

frontend/src/app/api/sessions/route.ts

@@ -1,6 +1,12 @@
 import { NextResponse } from "next/server";
-import { chatSessionCreateSchema, ChatSessionBodyTooLargeError, readChatSessionJson } from "@/lib/chat-session-write-contract";
+import {
+  chatSessionCreateInsertRow,
+  chatSessionCreateSchema,
+  ChatSessionBodyTooLargeError,
+  readChatSessionJson,
+} from "@/lib/chat-session-write-contract";
 import { consumeUserRequestRateLimit } from "@/lib/request-rate-limit";
+import { resolveInheritedContextSummary } from "@/lib/session-context-summary";
 import { isSupabaseConfigurationError } from "@/lib/supabase/config";
 import { createServerSupabaseClient } from "@/lib/supabase/server";
 import {
@@ -94,13 +100,28 @@ export async function POST(request: Request) {
     }
     const parsed = chatSessionCreateSchema.safeParse(await readChatSessionJson(request));
     if (!parsed.success) return NextResponse.json({ error: "聊天记录格式不正确" }, { status: 400 });
-    const { id, updated_at: _ignoredClientClock, ...values } = parsed.data;
-    const { error } = await supabase.from("chat_sessions").insert({
-      id,
-      user_id: user.id,
-      ...values,
-      updated_at: new Date().toISOString(),
+    const { id, updated_at: _ignoredClientClock, continued_from_session_id: continuedFromSessionId, ...values } = parsed.data;
+    const inheritedSummary = await resolveInheritedContextSummary({
+      continuedFromSessionId,
+      loadOwnedSummary: async (sourceId) => {
+        const { data } = await supabase
+          .from("chat_sessions")
+          .select("context_summary")
+          .eq("id", sourceId)
+          .eq("user_id", user.id)
+          .maybeSingle();
+        return data?.context_summary ?? null;
+      },
     });
+    const { error } = await supabase.from("chat_sessions").insert(
+      chatSessionCreateInsertRow({
+        id,
+        userId: user.id,
+        values,
+        inheritedSummary,
+        updatedAt: new Date().toISOString(),
+      }),
+    );
     if (error) return NextResponse.json({ error: "聊天记录暂时无法同步" }, { status: 500 });
     return NextResponse.json({ ok: true }, { status: 201 });
   } catch (error) {

frontend/src/hooks/use-consultation-run.ts

@@ -135,7 +135,7 @@ export type ConsultationRunParams = {
   uiPreviewMode: MutableRefObject<string | null>;
   persistSession: (session: ChatSession, mode?: "create" | "update") => Promise<void>;
   updateSession: (sessionId: string, change: (session: ChatSession) => ChatSession) => void;
-  startNewChat: () => Promise<ChatSession | null>;
+  startNewChat: (options?: { continuedFromSessionId?: string }) => Promise<ChatSession | null>;
   continueInNewChat: (prompt: { question: string; theme: Theme }) => Promise<void>;
   refreshAccount: () => Promise<void>;
   openAccountDialog: (dialog: AccountDialog, options?: HTMLButtonElement | null | OpenAccountDialogOptions) => void;

frontend/src/hooks/use-session-management.ts

@@ -139,7 +139,11 @@ export function useSessionManagement(params: SessionManagementParams) {
     setSessions((current) => current.map((session) => (session.id === sessionId ? change(session) : session)));
   }
 
-  async function persistSession(session: ChatSession, mode: "create" | "update" = "update") {
+  async function persistSession(
+    session: ChatSession,
+    mode: "create" | "update" = "update",
+    options?: { continuedFromSessionId?: string },
+  ) {
     if (!account) throw new Error("账户尚未加载完成");
     if (process.env.NODE_ENV === "development" && uiPreview.current) return;
     const values = mode === "create"
@@ -153,6 +157,9 @@ export function useSessionManagement(params: SessionManagementParams) {
         chart_profile_id: session.chartProfileId,
         chart_profile_name: session.chartProfileName,
         chart_profile_role: session.chartProfileRole,
+        ...(options?.continuedFromSessionId
+          ? { continued_from_session_id: options.continuedFromSessionId }
+          : {}),
       }
       : {
         title: session.title,
@@ -192,7 +199,10 @@ export function useSessionManagement(params: SessionManagementParams) {
 
   async function continueInNewChat(prompt: { question: string; theme: Theme }) {
     setSessionFullPrompt(null);
-    const created = await startNewChat();
+    const sourceSessionId = activeSessionId;
+    const created = await startNewChat(
+      sourceSessionId ? { continuedFromSessionId: sourceSessionId } : undefined,
+    );
     if (!created) return;
     setDraft(prompt.question);
     setDraftTheme(prompt.theme);
@@ -294,7 +304,7 @@ export function useSessionManagement(params: SessionManagementParams) {
     }
   }
 
-  async function startNewChat(): Promise<ChatSession | null> {
+  async function startNewChat(options?: { continuedFromSessionId?: string }): Promise<ChatSession | null> {
     if (!account || !modelCatalog || creatingSession) return null;
     const nextSession = {
       ...createSession(modelCatalog.defaultModelId),
@@ -312,7 +322,13 @@ export function useSessionManagement(params: SessionManagementParams) {
     setComposerNotice("");
     setRequestError(null);
     try {
-      await persistSession(nextSession, "create");
+      await persistSession(
+        nextSession,
+        "create",
+        options?.continuedFromSessionId
+          ? { continuedFromSessionId: options.continuedFromSessionId }
+          : undefined,
+      );
       return nextSession;
     } catch (caught) {
       setSessions((current) => current.filter((session) => session.id !== nextSession.id));

frontend/src/lib/chat-session-write-contract.ts

@@ -59,6 +59,7 @@ export const chatSessionCreateSchema = z.object({
   messages: z.array(chatMessageSchema).max(0),
   session_type: z.enum(["consultation", "birth_time_rectification"]),
   rectification_case_id: z.string().uuid().nullable(),
+  continued_from_session_id: z.string().uuid().optional(),
   ...chartBindingSchema,
   updated_at: z.string().datetime().optional(),
 }).strict();
@@ -148,11 +149,41 @@ export type ChatSessionCreate = Readonly<{
   messages: readonly [];
   session_type: "consultation" | "birth_time_rectification";
   rectification_case_id: string | null;
+  continued_from_session_id?: string;
   chart_profile_id?: string | null;
   chart_profile_name?: string | null;
   chart_profile_role?: "self" | "other" | null;
 }>;
 
+export type ChatSessionCreateInsertValues = Readonly<{
+  title: string;
+  theme: ConsultationDomain;
+  model_id: string;
+  messages: readonly unknown[];
+  session_type: "consultation" | "birth_time_rectification";
+  rectification_case_id: string | null;
+  chart_profile_id?: string | null;
+  chart_profile_name?: string | null;
+  chart_profile_role?: "self" | "other" | null;
+}>;
+
+export function chatSessionCreateInsertRow(input: {
+  id: string;
+  userId: string;
+  values: ChatSessionCreateInsertValues;
+  inheritedSummary?: unknown;
+  updatedAt: string;
+}): Record<string, unknown> {
+  const row: Record<string, unknown> = {
+    id: input.id,
+    user_id: input.userId,
+    ...input.values,
+    updated_at: input.updatedAt,
+  };
+  if (input.inheritedSummary) row.context_summary = input.inheritedSummary;
+  return row;
+}
+
 export type ChatSessionWrite = Readonly<{
   title: string;
   theme: ConsultationDomain;

frontend/src/lib/consultation-session-history.ts

@@ -1,11 +1,14 @@
 export const CONSULTATION_HISTORY_LIMIT = 12;
 export const CONSULTATION_HISTORY_MESSAGE_CHARS = 12_000;
-export const CONSULTATION_HISTORY_TAIL_MAX_CHARS = 16_000;
 export const CONSULTATION_HISTORY_SYSTEM_RESERVE_TOKENS = 60_000;
 export const CONSULTATION_HISTORY_CHAR_PER_TOKEN = 1.5;
 export const CONSULTATION_HISTORY_BUDGET_MIN_CHARS = 4_000;
 export const CONSULTATION_HISTORY_BUDGET_MAX_CHARS = 40_000;
 export const DEFAULT_MODEL_CONTEXT_WINDOW = 128_000;
+// 0.4 of the history budget. At the default 128k window the budget is 40,000,
+// so the checkpoint fires at 16,000 — the previous hard-coded threshold.
+// Smaller windows then checkpoint before the tail can exceed the budget.
+export const CONSULTATION_HISTORY_CHECKPOINT_BUDGET_RATIO = 0.4;
 
 export const SESSION_CONTEXT_SUMMARY_HEADING = "【会话摘要（服务端维护）】";
 
@@ -51,6 +54,15 @@ export function historyBudgetChars(contextWindow: number | null | undefined): nu
   );
 }
 
+export function consultationHistoryCheckpointChars(contextWindow: number | null | undefined): number {
+  const budget = historyBudgetChars(contextWindow);
+  const threshold = Math.floor(budget * CONSULTATION_HISTORY_CHECKPOINT_BUDGET_RATIO);
+  if (!(threshold < budget)) {
+    throw new Error("consultation history checkpoint threshold must stay below the history budget");
+  }
+  return threshold;
+}
+
 export function parseSessionContextSummary(value: unknown): SessionContextSummaryV1 | null {
   if (!value || typeof value !== "object" || Array.isArray(value)) return null;
   const row = value as Record<string, unknown>;
@@ -74,6 +86,13 @@ export function omissionMarker(omittedChars: number): string {
   return `……（以下省略 ${omittedChars} 字，结论已并入会话摘要）`;
 }
 
+export function droppedRoundsMarker(droppedCount: number, hasSummary: boolean): string {
+  if (droppedCount <= 0) return "";
+  return hasSummary
+    ? `……（更早的 ${droppedCount} 轮问答已并入上面的会话摘要）`
+    : `……（更早的 ${droppedCount} 轮问答未能进入本轮上下文，结论尚未并入会话摘要）`;
+}
+
 export function clipConsultationHistoryText(text: string): string {
   if (text.length <= CONSULTATION_HISTORY_MESSAGE_CHARS) return text;
   const omitted = text.length - CONSULTATION_HISTORY_MESSAGE_CHARS;
@@ -165,16 +184,18 @@ export function consultationUserTurnContent(input: {
   instruction: string;
   extra?: string;
   summaryText?: string | null;
+  droppedCount?: number;
   question: string;
 }): string {
+  const summary = input.summaryText?.trim() ?? "";
+  const dropped = droppedRoundsMarker(input.droppedCount ?? 0, Boolean(summary));
   return [
     input.currentTime,
     input.name ? `用户称呼：${input.name}` : "",
     input.instruction,
     input.extra ?? "",
-    input.summaryText?.trim()
-      ? `${SESSION_CONTEXT_SUMMARY_HEADING}\n${input.summaryText.trim()}`
-      : "",
+    summary ? `${SESSION_CONTEXT_SUMMARY_HEADING}\n${summary}` : "",
+    dropped,
     input.question,
   ].filter(Boolean).join("\n");
 }

frontend/src/lib/session-context-summary.ts

@@ -1,7 +1,7 @@
 import { Agent } from "@mastra/core/agent";
 
 import {
-  CONSULTATION_HISTORY_TAIL_MAX_CHARS,
+  consultationHistoryCheckpointChars,
   lastConsultationPair,
   parseSessionContextSummary,
   storedConsultationTurns,
@@ -98,7 +98,7 @@ export function sanitizeSessionContextSummary(raw: string): string | null {
 export function tailCharCount(
   messages: unknown,
   summary: SessionContextSummaryV1 | null,
-  options: { excludeRequestId?: string } = {},
+  options: { excludeRequestId?: string; contextWindow?: number | null } = {},
 ): number {
   const turns = storedConsultationTurns(messages, { excludeRequestId: options.excludeRequestId });
   const tail = summary
@@ -110,9 +110,10 @@ export function tailCharCount(
 export function shouldCheckpoint(
   messages: unknown,
   summary: SessionContextSummaryV1 | null,
-  options: { excludeRequestId?: string } = {},
+  options: { excludeRequestId?: string; contextWindow?: number | null } = {},
 ): boolean {
-  return tailCharCount(messages, summary, options) > CONSULTATION_HISTORY_TAIL_MAX_CHARS;
+  return tailCharCount(messages, summary, options)
+    > consultationHistoryCheckpointChars(options.contextWindow);
 }
 
 export function messagesForSummaryInput(
@@ -215,6 +216,19 @@ export function nextSessionContextSummary(
   };
 }
 
+export async function resolveInheritedContextSummary(input: {
+  continuedFromSessionId?: string | null;
+  loadOwnedSummary: (sessionId: string) => Promise<unknown>;
+}): Promise<SessionContextSummaryV1 | null> {
+  const sourceId = input.continuedFromSessionId?.trim();
+  if (!sourceId) return null;
+  try {
+    return parseSessionContextSummary(await input.loadOwnedSummary(sourceId));
+  } catch {
+    return null;
+  }
+}
+
 export async function writeSessionContextSummary(input: {
   seenUpdatedAt: string | null;
   summary: SessionContextSummaryV1;
@@ -228,13 +242,17 @@ export async function checkpointSessionContextSummary(input: {
   messages: unknown;
   summary: unknown;
   excludeRequestId?: string;
+  contextWindow?: number | null;
   now?: () => Date;
   generateText: (prompt: string, signal?: AbortSignal) => Promise<string>;
   update: (summary: SessionContextSummaryV1, seenUpdatedAt: string | null) => Promise<boolean>;
   timeoutMs?: number;
 }): Promise<"written" | "skipped" | "abandoned" | "failed"> {
   const previous = parseSessionContextSummary(input.summary);
-  if (!shouldCheckpoint(input.messages, previous, { excludeRequestId: input.excludeRequestId })) {
+  if (!shouldCheckpoint(input.messages, previous, {
+    excludeRequestId: input.excludeRequestId,
+    contextWindow: input.contextWindow,
+  })) {
     return "skipped";
   }
   try {

frontend/tests/chat-session-authority.test.ts

@@ -20,6 +20,10 @@ test("session list GET omits messages while detail GET returns them", () => {
     /SESSION_LIST_COLUMNS = "id,title,theme,model_id,session_type,rectification_case_id,chart_profile_id,chart_profile_name,chart_profile_role,updated_at,pinned,archived_at"/,
   );
   assert.doesNotMatch(listRoute, /select\(SESSION_LIST_COLUMNS\)[\s\S]*messages/);
+  assert.doesNotMatch(
+    listRoute,
+    /SESSION_LIST_COLUMNS = "[^"]*context_summary/,
+  );
   assert.match(itemRoute, /export async function GET/);
   assert.match(
     itemRoute,
@@ -52,6 +56,8 @@ test("consult appends the user question after reserve and returns session_full",
   assert.match(sendSource, /caught\.code === "session_full"/);
   assert.match(sendSource, /label: "开新对话"/);
   assert.match(sendSource, /continueInNewChat\(\{ question: originalQuestion, theme \}\)/);
+  assert.match(page, /continuedFromSessionId: sourceSessionId/);
+  assert.doesNotMatch(page, /接着上次|继续上次聊|继承会话摘要|从上次对话继续/);
 });
 
 test("PATCH compatibility accepts and ignores a legacy messages write", () => {

frontend/tests/chat-session-url.test.ts

@@ -173,7 +173,7 @@ test("popstate to a missing session query reuses selectSession side effects for
 });
 
 test("creating and leaving a session keep the address bar in sync", () => {
-  const startNewChat = sourceBetween(page, "async function startNewChat()", "function selectSession(");
+  const startNewChat = sourceBetween(page, "async function startNewChat(", "function selectSession(");
   assert.match(startNewChat, /writeSessionUrl\(nextSession\.id, "push"\)/);
   assert.match(startNewChat, /window\.history\.replaceState\(null, "", previousHref\)/);
 

frontend/tests/chat-session-write.test.ts

@@ -1,7 +1,14 @@
 import assert from "node:assert/strict";
 import { readFileSync } from "node:fs";
 import test from "node:test";
-import { chatSessionCreateSchema, chatSessionMetadataPatchSchema, chatSessionWriteSchema, writeChatSession, type ChatSessionWrite } from "../src/lib/chat-session-write-contract.ts";
+import {
+  chatSessionCreateInsertRow,
+  chatSessionCreateSchema,
+  chatSessionMetadataPatchSchema,
+  chatSessionWriteSchema,
+  writeChatSession,
+  type ChatSessionWrite,
+} from "../src/lib/chat-session-write-contract.ts";
 import { metadataUpdateValues } from "../src/lib/session-metadata-update.ts";
 import { homeSurface } from "./home-surface.ts";
 
@@ -41,6 +48,61 @@ test("create schema keeps the client-generated session id after transcript limit
   assert.equal(parsed.messages.length, 0);
 });
 
+test("create schema accepts continued_from_session_id and rejects client-supplied context_summary", () => {
+  const parsed = chatSessionCreateSchema.parse({
+    id: sessionId,
+    ...createValues,
+    continued_from_session_id: "22222222-2222-4222-8222-222222222222",
+  });
+  assert.equal(parsed.continued_from_session_id, "22222222-2222-4222-8222-222222222222");
+  assert.equal("context_summary" in parsed, false);
+  assert.equal("context_summary" in chatSessionCreateSchema.shape, false);
+
+  const withSummary = chatSessionCreateSchema.safeParse({
+    id: sessionId,
+    ...createValues,
+    context_summary: { version: 1, text: "injected" },
+  });
+  assert.equal(withSummary.success, false);
+
+  const badId = chatSessionCreateSchema.safeParse({
+    id: sessionId,
+    ...createValues,
+    continued_from_session_id: "not-a-uuid",
+  });
+  assert.equal(badId.success, false);
+});
+
+test("create insert copies an owned summary and omits a missing one", () => {
+  const source = {
+    version: 1 as const,
+    text: "已问过的问题\n事业时机",
+    throughRequestId: "a1",
+    throughMessageIndex: 3,
+    messageCount: 4,
+    updatedAt: "2026-09-15T00:00:00.000Z",
+  };
+  const copied = chatSessionCreateInsertRow({
+    id: sessionId,
+    userId: "owner",
+    values: createValues,
+    inheritedSummary: source,
+    updatedAt: "2026-09-16T00:00:00.000Z",
+  });
+  assert.deepEqual(copied.context_summary, source);
+  assert.equal("continued_from_session_id" in copied, false);
+
+  const skipped = chatSessionCreateInsertRow({
+    id: sessionId,
+    userId: "owner",
+    values: createValues,
+    inheritedSummary: null,
+    updatedAt: "2026-09-16T00:00:00.000Z",
+  });
+  assert.equal("context_summary" in skipped, false);
+  assert.equal(skipped.user_id, "owner");
+});
+
 test("create schema rejects a non-empty transcript", () => {
   // Former value: create accepted up to CHAT_SESSION_MAX_MESSAGES and was a
   // history-import path. Create is now only an empty session.
@@ -122,6 +184,19 @@ test("metadata patch accepts pin and archive fields without a transcript", () =>
   assert.deepEqual(chatSessionMetadataPatchSchema.parse({ archived_at: null }), { archived_at: null });
 });
 
+test("create write may carry continued_from_session_id and never context_summary", async () => {
+  const calls: Array<Record<string, unknown>> = [];
+  await writeChatSession(sessionId, {
+    ...createValues,
+    continued_from_session_id: "22222222-2222-4222-8222-222222222222",
+  }, "create", async (_url, init) => {
+    calls.push(JSON.parse(String(init?.body)));
+    return Response.json({ ok: true }, { status: 201 });
+  });
+  assert.equal(calls[0]?.continued_from_session_id, "22222222-2222-4222-8222-222222222222");
+  assert.equal("context_summary" in (calls[0] ?? {}), false);
+});
+
 test("chat session writes use same-origin API instead of browser-to-Supabase requests", async () => {
   const calls: Array<{ url: string; init?: RequestInit }> = [];
   await writeChatSession(sessionId, metadataPatch, "update", async (url, init) => {
@@ -205,8 +280,17 @@ test("session API owns create and update while answer UI keeps sync failures out
   assert.match(itemRoute, /readChatSessionJson/);
   assert.match(collectionRoute, /ChatSessionBodyTooLargeError/);
   assert.match(itemRoute, /ChatSessionBodyTooLargeError/);
-  // Former value: `const { id, ...values } = parsed.data` trusted the client clock.
-  assert.match(collectionRoute, /const \{ id, updated_at: _ignoredClientClock, \.\.\.values \} = parsed\.data/);
+  // Former value: `const { id, updated_at: _ignoredClientClock, ...values } = parsed.data`
+  // New value: also peel `continued_from_session_id` so it is never inserted as a column.
+  assert.match(
+    collectionRoute,
+    /const \{ id, updated_at: _ignoredClientClock, continued_from_session_id: continuedFromSessionId, \.\.\.values \} = parsed\.data/,
+  );
+  assert.match(collectionRoute, /resolveInheritedContextSummary/);
+  assert.match(collectionRoute, /chatSessionCreateInsertRow/);
+  assert.match(collectionRoute, /\.eq\("user_id", user\.id\)/);
+  assert.match(collectionRoute, /status: 201/);
+  assert.doesNotMatch(collectionRoute, /context_summary: parsed/);
   assert.match(contract, /function limitTranscriptSize<Output extends \{ messages: Array<\{ text: string; thinkingText\?: string; thinkingSections\?: unknown \}> \}>/);
   assert.match(contract, /\): z\.ZodType<Output> \{/);
   assert.match(page, /chartSnapshotForSession/);

frontend/tests/composer-isolation-contract.test.ts

@@ -91,7 +91,7 @@ test("every external draft writer keeps working through the page-owned setters",
 
   // When: each existing write path is inspected.
   const chooseSuggested = sourceBetween(pageSource, "function chooseSuggestedQuestion(", "async function startSuggestedConsultation");
-  const startNewChat = sourceBetween(pageSource, "async function startNewChat()", "function selectSession(");
+  const startNewChat = sourceBetween(pageSource, "async function startNewChat(", "function selectSession(");
   const selectSession = sourceBetween(pageSource, "function selectSession(sessionId: string)", "async function selectSessionModel");
   const saveOnboardingName = sourceBetween(pageSource, "async function saveOnboardingName()", "async function saveOnboardingBirth");
   const stopRestore = sourceBetween(pageSource, "updateSession(pending.sessionId, () => pending.previousSession);", "function completeConsultationInterface");

frontend/tests/consultation-context-cache-contract.test.ts

@@ -14,7 +14,10 @@ test("consult history uses the checkpoint tail and puts the summary after the ti
   assert.match(consultRoute, /consultationHistoryWindow\(chatSession\.messages, contextSummary/);
   assert.match(consultRoute, /SESSION_CONTEXT_SUMMARY_HEADING|consultationUserTurnContent/);
   assert.match(consultRoute, /summaryText: historyWindow\.summaryText/);
+  assert.match(consultRoute, /droppedCount: historyWindow\.droppedCount/);
   assert.match(history, /【会话摘要（服务端维护）】/);
+  assert.match(history, /droppedRoundsMarker/);
+  assert.doesNotMatch(history, /16_000|16000/);
   const helper = history.slice(history.indexOf("export function consultationUserTurnContent"));
   const timeLine = helper.indexOf("input.currentTime");
   const summaryLine = helper.indexOf("SESSION_CONTEXT_SUMMARY_HEADING");
@@ -33,9 +36,13 @@ test("consult retries once on context overflow with summary plus the last pair",
 test("consult checkpoints the session summary after a successful completion", () => {
   assert.match(consultRoute, /void checkpointConsultationContext\(\)/);
   assert.match(consultRoute, /checkpointSessionContextSummary/);
+  assert.match(consultRoute, /contextWindow: sessionContextWindow/);
   assert.match(consultRoute, /context_summary ->>updatedAt|context_summary->>updatedAt/);
   assert.match(consultRoute, /console\.warn\("session context summary failed"/);
   assert.doesNotMatch(consultRoute, /AbortSignal\.timeout\(\s*15/);
+  const summary = readFileSync(new URL("../src/lib/session-context-summary.ts", import.meta.url), "utf8");
+  assert.match(summary, /consultationHistoryCheckpointChars/);
+  assert.doesNotMatch(summary, /CONSULTATION_HISTORY_TAIL_MAX_CHARS/);
 });
 
 test("the context summary migration only adds one jsonb column", () => {

frontend/tests/consultation-session-history.test.ts

@@ -2,11 +2,14 @@ import assert from "node:assert/strict";
 import test from "node:test";
 
 import {
+  CONSULTATION_HISTORY_CHECKPOINT_BUDGET_RATIO,
   CONSULTATION_HISTORY_MESSAGE_CHARS,
   clipConsultationHistoryText,
+  consultationHistoryCheckpointChars,
   consultationHistoryFromStoredMessages,
   consultationHistoryWindow,
   consultationUserTurnContent,
+  droppedRoundsMarker,
   historyBudgetChars,
   isContextOverflowError,
   omissionMarker,
@@ -77,6 +80,61 @@ test("historyBudgetChars uses 64k, 32k, and null-as-128k windows", () => {
   assert.equal(historyBudgetChars(undefined), 40_000);
 });
 
+test("checkpoint threshold stays below the history budget for legal context windows", () => {
+  assert.equal(CONSULTATION_HISTORY_CHECKPOINT_BUDGET_RATIO, 0.4);
+  const windows = [200_000, 128_000, 64_000, 32_000, null] as const;
+  for (const window of windows) {
+    const budget = historyBudgetChars(window);
+    const threshold = consultationHistoryCheckpointChars(window);
+    assert.ok(threshold < budget, `window=${window}`);
+  }
+  // 128k keeps the previous 16,000-character checkpoint.
+  assert.equal(consultationHistoryCheckpointChars(128_000), 16_000);
+  assert.equal(consultationHistoryCheckpointChars(null), 16_000);
+  assert.equal(consultationHistoryCheckpointChars(64_000), 2_400);
+  assert.equal(consultationHistoryCheckpointChars(32_000), 1_600);
+});
+
+test("dropped whole turns leave an omission marker in the user-turn summary slot", () => {
+  const body = "x".repeat(3_000);
+  const history = consultationHistoryWindow(numberedMessages(20, () => body), null, {
+    contextWindow: 128_000,
+  });
+  assert.ok(history.droppedCount > 0);
+  const withoutSummary = consultationUserTurnContent({
+    currentTime: "当前时间：2026-09-16 12:00（中国）",
+    instruction: "先加载 Jyotish Skill",
+    summaryText: history.summaryText,
+    droppedCount: history.droppedCount,
+    question: "刚才你说的那个时间",
+  });
+  assert.match(
+    withoutSummary,
+    new RegExp(`更早的 ${history.droppedCount} 轮问答未能进入本轮上下文，结论尚未并入会话摘要`),
+  );
+  assert.equal(withoutSummary.includes(SESSION_CONTEXT_SUMMARY_HEADING), false);
+
+  const withSummary = consultationUserTurnContent({
+    currentTime: "当前时间：2026-09-16 12:00（中国）",
+    instruction: "先加载 Jyotish Skill",
+    summaryText: "先前结论",
+    droppedCount: history.droppedCount,
+    question: "刚才你说的那个时间",
+  });
+  assert.match(withSummary, new RegExp(`更早的 ${history.droppedCount} 轮问答已并入上面的会话摘要`));
+  assert.ok(withSummary.indexOf(SESSION_CONTEXT_SUMMARY_HEADING) < withSummary.indexOf("刚才你说的那个时间"));
+
+  const kept = consultationUserTurnContent({
+    currentTime: "当前时间：2026-09-16 12:00（中国）",
+    instruction: "先加载 Jyotish Skill",
+    summaryText: "先前结论",
+    droppedCount: 0,
+    question: "刚才你说的那个时间",
+  });
+  assert.equal(kept.includes("更早的"), false);
+  assert.equal(droppedRoundsMarker(0, true), "");
+});
+
 test("stored consultation history can skip the in-flight request id", () => {
   const history = consultationHistoryFromStoredMessages([
     { role: "user", text: "old", requestId: "keep" },

frontend/tests/session-context-summary.test.ts

@@ -3,13 +3,14 @@ import { readFileSync } from "node:fs";
 import test from "node:test";
 
 import {
-  CONSULTATION_HISTORY_TAIL_MAX_CHARS,
+  consultationHistoryCheckpointChars,
 } from "../src/lib/consultation-session-history.ts";
 import {
   buildSummaryPrompt,
   checkpointSessionContextSummary,
   generateSessionContextSummary,
   messagesForSummaryInput,
+  resolveInheritedContextSummary,
   sanitizeSessionContextSummary,
   shouldCheckpoint,
   writeSessionContextSummary,
@@ -24,10 +25,14 @@ function overBudgetConversation() {
   ];
 }
 
-test("checkpoint triggers only when the tail exceeds 16_000 characters", () => {
-  assert.equal(CONSULTATION_HISTORY_TAIL_MAX_CHARS, 16_000);
+test("checkpoint triggers only when the tail exceeds the derived threshold", () => {
+  // Former value: hard-coded CONSULTATION_HISTORY_TAIL_MAX_CHARS = 16_000.
+  // 128k still checkpoints at 16_000 (0.4 × 40_000 budget).
+  assert.equal(consultationHistoryCheckpointChars(128_000), 16_000);
   assert.equal(shouldCheckpoint([{ role: "user", text: "x".repeat(15_999) }], null), false);
   assert.equal(shouldCheckpoint([{ role: "user", text: "x".repeat(16_001) }], null), true);
+  assert.equal(shouldCheckpoint([{ role: "user", text: "x".repeat(2_400) }], null, { contextWindow: 64_000 }), false);
+  assert.equal(shouldCheckpoint([{ role: "user", text: "x".repeat(2_401) }], null, { contextWindow: 64_000 }), true);
 });
 
 test("checkpoint prompt omits the last question-answer pair", () => {
@@ -108,6 +113,41 @@ test("writeSessionContextSummary abandons when updatedAt does not match", async
   assert.equal(result, "abandoned");
 });
 
+test("inherited context summary copies owned text and skips foreign or empty sources", async () => {
+  const source = {
+    version: 1 as const,
+    text: "已问过的问题\n事业时机",
+    throughRequestId: "a1",
+    throughMessageIndex: 3,
+    messageCount: 4,
+    updatedAt: "2026-09-15T00:00:00.000Z",
+  };
+  const copied = await resolveInheritedContextSummary({
+    continuedFromSessionId: "11111111-1111-4111-8111-111111111111",
+    loadOwnedSummary: async () => source,
+  });
+  assert.deepEqual(copied, source);
+
+  const foreign = await resolveInheritedContextSummary({
+    continuedFromSessionId: "22222222-2222-4222-8222-222222222222",
+    loadOwnedSummary: async () => null,
+  });
+  assert.equal(foreign, null);
+
+  const empty = await resolveInheritedContextSummary({
+    continuedFromSessionId: "11111111-1111-4111-8111-111111111111",
+    loadOwnedSummary: async () => ({ version: 1, text: "   " }),
+  });
+  assert.equal(empty, null);
+
+  const skipped = await resolveInheritedContextSummary({
+    loadOwnedSummary: async () => {
+      throw new Error("should not load");
+    },
+  });
+  assert.equal(skipped, null);
+});
+
 test("checkpoint writes a new summary when the tail is over budget", async () => {
   const result = await checkpointSessionContextSummary({
     messages: overBudgetConversation(),