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.

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(),