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/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(),