fix(work-time): clip cross-class padding; gate & payload fixes (#395)

F1: pad-clip adjacent different-class sessions at the raw-gap midpoint so
workMs and agentOnlyMs can never double-count the same wall-clock (default
agentTGap 7m < pIn+pOut 10m made a work-session-ending-in-agent overlap a
nearby agent_only run). Reword the config guard/comment: cross-class
disjointness is now structural, tGap≥pIn+pOut is a kept sanity bound. Add a
cross-class no-double-count test and a real seeded property/fuzz test (250
random timelines × 4 tz) asserting per-class union, cross-class disjointness,
and Σ per-day activeMs == workMs.

F2: page.controller.spec — add a ForbiddenException view-gate reject test that
asserts the rejection propagates and computeWorkTime is NOT reached, locking
validateCanView before compute.

F3: WorkTimeStat renders for agent-only pages (workMs==0, agentOnlyMs>0) with
an `agent:` headline so the punch-card stays reachable.

F4: drop the dead un-bucketed `sessions` list from the PageWorkTime response
and the client work-time types (no client reads it; bucketByDay still consumes
the core sessions internally).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/client/public/locales/en-US/translation.json

@@ -239,8 +239,6 @@
   "Comment re-opened successfully": "Comment re-opened successfully",
   "Comment unresolved successfully": "Comment unresolved successfully",
   "Failed to resolve comment": "Failed to resolve comment",
-  "Failed to re-open comment": "Failed to re-open comment",
-  "Comment no longer exists": "Comment no longer exists",
   "Resolve comment": "Resolve comment",
   "Unresolve comment": "Unresolve comment",
   "Resolve Comment Thread": "Resolve Comment Thread",
@@ -1429,5 +1427,20 @@
   "Boundary": "Boundary",
   "Autosave": "Autosave",
   "Only versions": "Only versions",
-  "No saved versions yet.": "No saved versions yet."
+  "No saved versions yet.": "No saved versions yet.",
+  "Time worked on this article": "Time worked on this article",
+  "Show time worked on this page": "Show time worked on this page",
+  "Estimated time worked (inactivity gap {{gap}} min)": "Estimated time worked (inactivity gap {{gap}} min)",
+  "Estimate · timezone {{tz}} · inactivity gap {{gap}} min": "Estimate · timezone {{tz}} · inactivity gap {{gap}} min",
+  "No editing activity recorded yet.": "No editing activity recorded yet.",
+  "× {{count}} days without edits": "× {{count}} days without edits",
+  "agent: {{value}}": "agent: {{value}}",
+  "Work": "Work",
+  "Agent": "Agent",
+  "≈ {{hours}}h {{minutes}}m": "≈ {{hours}}h {{minutes}}m",
+  "≈ {{hours}}h": "≈ {{hours}}h",
+  "≈ {{minutes}}m": "≈ {{minutes}}m",
+  "{{hours}}h {{minutes}}m": "{{hours}}h {{minutes}}m",
+  "{{hours}}h": "{{hours}}h",
+  "{{minutes}}m": "{{minutes}}m"
 }

apps/client/public/locales/ru-RU/translation.json

@@ -239,8 +239,6 @@
   "Comment re-opened successfully": "Комментарий успешно открыт повторно",
   "Comment unresolved successfully": "Комментарий успешно переведён в нерешённые",
   "Failed to resolve comment": "Не удалось разрешить комментарий",
-  "Failed to re-open comment": "Не удалось переоткрыть комментарий",
-  "Comment no longer exists": "Комментарий больше не существует",
   "Resolve comment": "Решить комментарий",
   "Unresolve comment": "Снять статус решённого с комментария",
   "Resolve Comment Thread": "Решить ветку комментариев",
@@ -1444,5 +1442,20 @@
   "Boundary": "Граница",
   "Autosave": "Автосейв",
   "Only versions": "Только версии",
-  "No saved versions yet.": "Пока нет сохранённых версий."
+  "No saved versions yet.": "Пока нет сохранённых версий.",
+  "Time worked on this article": "Время работы над статьёй",
+  "Show time worked on this page": "Показать время работы над страницей",
+  "Estimated time worked (inactivity gap {{gap}} min)": "Оценка времени работы (порог паузы {{gap}} мин)",
+  "Estimate · timezone {{tz}} · inactivity gap {{gap}} min": "Оценка · таймзона {{tz}} · порог паузы {{gap}} мин",
+  "No editing activity recorded yet.": "Правок пока нет.",
+  "× {{count}} days without edits": "× {{count}} дн. без правок",
+  "agent: {{value}}": "агент: {{value}}",
+  "Work": "Работа",
+  "Agent": "Агент",
+  "≈ {{hours}}h {{minutes}}m": "≈ {{hours}} ч {{minutes}} мин",
+  "≈ {{hours}}h": "≈ {{hours}} ч",
+  "≈ {{minutes}}m": "≈ {{minutes}} мин",
+  "{{hours}}h {{minutes}}m": "{{hours}} ч {{minutes}} м",
+  "{{hours}}h": "{{hours}} ч",
+  "{{minutes}}m": "{{minutes}} м"
 }

apps/client/src/features/comment/components/comment-list-with-tabs.test.tsx

@@ -27,15 +27,11 @@ vi.mock("@/features/space/queries/space-query.ts", () => ({
 import {
   buildChildrenByParent,
   CommentEditorWithActions,
-  sortResolvedByResolvedAt,
 } from "./comment-list-with-tabs";
 
 const c = (id: string, parentCommentId: string | null = null): IComment =>
   ({ id, parentCommentId }) as IComment;
 
-const resolvedAtComment = (id: string, resolvedAt: unknown): IComment =>
-  ({ id, resolvedAt }) as unknown as IComment;
-
 describe("buildChildrenByParent (childrenByParent grouping)", () => {
   it("returns an empty map for undefined or empty input", () => {
     expect(buildChildrenByParent(undefined).size).toBe(0);
@@ -75,48 +71,6 @@ describe("buildChildrenByParent (childrenByParent grouping)", () => {
   });
 });
 
-describe("sortResolvedByResolvedAt (Resolved tab order, #542)", () => {
-  it("orders by resolvedAt DESC — newest resolve first — with ISO-STRING values", () => {
-    // At runtime resolvedAt is an ISO string (axios JSON / WS subscription), so
-    // the sort must coerce with new Date(...) before .getTime().
-    const older = resolvedAtComment("older", "2026-07-10T10:00:00.000Z");
-    const newest = resolvedAtComment("newest", "2026-07-12T10:00:00.000Z");
-    const middle = resolvedAtComment("middle", "2026-07-11T10:00:00.000Z");
-
-    const out = sortResolvedByResolvedAt([older, newest, middle]);
-    expect(out.map((x) => x.id)).toEqual(["newest", "middle", "older"]);
-  });
-
-  it("also handles Date instances (optimistic onMutate window)", () => {
-    const older = resolvedAtComment("older", new Date("2026-01-01T00:00:00Z"));
-    const newer = resolvedAtComment("newer", new Date("2026-06-01T00:00:00Z"));
-    expect(sortResolvedByResolvedAt([older, newer]).map((x) => x.id)).toEqual([
-      "newer",
-      "older",
-    ]);
-  });
-
-  it("does not mutate the input array", () => {
-    const a = resolvedAtComment("a", "2026-01-01T00:00:00.000Z");
-    const b = resolvedAtComment("b", "2026-02-01T00:00:00.000Z");
-    const input = [a, b];
-    sortResolvedByResolvedAt(input);
-    expect(input.map((x) => x.id)).toEqual(["a", "b"]);
-  });
-
-  it("keeps stable order for equal resolvedAt timestamps", () => {
-    const ts = "2026-03-03T03:03:03.000Z";
-    const x = resolvedAtComment("x", ts);
-    const y = resolvedAtComment("y", ts);
-    const z = resolvedAtComment("z", ts);
-    expect(sortResolvedByResolvedAt([x, y, z]).map((c) => c.id)).toEqual([
-      "x",
-      "y",
-      "z",
-    ]);
-  });
-});
-
 function renderReplyEditor() {
   return render(
     <MantineProvider>

apps/client/src/features/comment/components/comment-list-with-tabs.tsx

@@ -53,22 +53,6 @@ export function buildChildrenByParent(
   return m;
 }
 
-// Sort the Resolved tab by resolve time, newest first, on a COPY (never mutate
-// the react-query cache array). `resolvedAt` is typed `Date` but at runtime it
-// is an ISO STRING (from the axios-JSON onSuccess and the WS subscription) — a
-// real Date only during the optimistic onMutate window — so it MUST be coerced
-// with `new Date(...)` before `.getTime()`, or a raw `.getTime()` on the string
-// throws / yields NaN. ES2019's stable sort preserves order for equal
-// timestamps. Callers pass a list already filtered to a truthy `resolvedAt`, so
-// the non-null assertion is safe.
-// Exported for unit testing.
-export function sortResolvedByResolvedAt(resolved: IComment[]): IComment[] {
-  return [...resolved].sort(
-    (a, b) =>
-      new Date(b.resolvedAt!).getTime() - new Date(a.resolvedAt!).getTime(),
-  );
-}
-
 function CommentListWithTabs({ onClose }: CommentListWithTabsProps) {
   const { t } = useTranslation();
   const { pageSlug } = useParams();
@@ -107,10 +91,7 @@ function CommentListWithTabs({ onClose }: CommentListWithTabsProps) {
       (comment: IComment) => comment.resolvedAt,
     );
 
-    return {
-      activeComments: active,
-      resolvedComments: sortResolvedByResolvedAt(resolved),
-    };
+    return { activeComments: active, resolvedComments: resolved };
   }, [comments]);
 
   // Index replies by their parent once, instead of an O(n^2) filter per thread.

apps/client/src/features/comment/queries/comment-query.resolve-undo.test.tsx

@@ -1,353 +0,0 @@
-import { describe, it, expect, vi, beforeEach } from "vitest";
-import React from "react";
-import { renderHook, waitFor } from "@testing-library/react";
-import {
-  QueryClient,
-  QueryClientProvider,
-  InfiniteData,
-} from "@tanstack/react-query";
-
-/**
- * Coverage for the resolve/reopen mutation (#542): the Undo-in-toast reopen and
- * its double-click guard, the terminal 404 branch (drop from cache + clear the
- * inline mark, no rollback), and the directional error copy.
- */
-
-// A fake TipTap editor injected via the mocked pageEditorAtom, so we can assert
-// the mutation clears the inline comment mark (unsetComment / setCommentResolved).
-const editorMock = vi.hoisted(() => ({
-  current: {
-    isDestroyed: false,
-    commands: { unsetComment: vi.fn(), setCommentResolved: vi.fn() },
-  } as {
-    isDestroyed: boolean;
-    commands: {
-      unsetComment: (id: string) => void;
-      setCommentResolved: (id: string, v: boolean) => void;
-    };
-  } | null,
-}));
-
-vi.mock("@mantine/notifications", () => ({
-  notifications: { show: vi.fn(), hide: vi.fn() },
-}));
-
-vi.mock("jotai", () => ({
-  atom: (v: unknown) => v,
-  useAtomValue: () => editorMock.current,
-}));
-
-vi.mock("@/features/comment/services/comment-service", () => ({
-  applySuggestion: vi.fn(),
-  dismissSuggestion: vi.fn(),
-  createComment: vi.fn(),
-  updateComment: vi.fn(),
-  deleteComment: vi.fn(),
-  resolveComment: vi.fn(),
-  getPageComments: vi.fn(),
-}));
-
-import { notifications } from "@mantine/notifications";
-import { resolveComment } from "@/features/comment/services/comment-service";
-import {
-  useResolveCommentMutation,
-  RESOLVE_UNDO_AUTOCLOSE_MS,
-  RQ_KEY,
-} from "@/features/comment/queries/comment-query";
-import { IComment } from "@/features/comment/types/comment.types";
-
-const PAGE_ID = "page-1";
-
-function seededClient(comment: IComment) {
-  const queryClient = new QueryClient({
-    defaultOptions: { mutations: { retry: false } },
-  });
-  const seed: InfiniteData<any> = {
-    pageParams: [undefined],
-    pages: [
-      { items: [comment], meta: { hasNextPage: false, nextCursor: null } },
-    ],
-  };
-  queryClient.setQueryData(RQ_KEY(PAGE_ID), seed);
-  const wrapper = ({ children }: { children: React.ReactNode }) => (
-    <QueryClientProvider client={queryClient}>{children}</QueryClientProvider>
-  );
-  return { queryClient, wrapper };
-}
-
-function items(queryClient: QueryClient): IComment[] {
-  const cache = queryClient.getQueryData(RQ_KEY(PAGE_ID)) as
-    | InfiniteData<any>
-    | undefined;
-  return cache?.pages.flatMap((p) => p.items) ?? [];
-}
-
-const comment = (over?: Partial<IComment>): IComment =>
-  ({
-    id: "c-1",
-    pageId: PAGE_ID,
-    content: "{}",
-    creatorId: "u-1",
-    workspaceId: "ws-1",
-    createdAt: new Date(),
-    resolvedAt: null,
-    ...over,
-  }) as IComment;
-
-// Pull the inline Undo button's onClick out of the success toast's message tree.
-function undoOnClickFromToast(): () => void {
-  const call = vi
-    .mocked(notifications.show)
-    .mock.calls.map((c) => c[0])
-    .find((arg: any) => arg?.autoClose === RESOLVE_UNDO_AUTOCLOSE_MS);
-  expect(call).toBeTruthy();
-  const message: any = (call as any).message;
-  // message = Group( Text, Button ); grab the Button element's onClick.
-  const children = message.props.children as any[];
-  const button = children[1];
-  return button.props.onClick;
-}
-
-describe("useResolveCommentMutation — Undo toast (#542)", () => {
-  beforeEach(() => {
-    vi.clearAllMocks();
-    editorMock.current = {
-      isDestroyed: false,
-      commands: { unsetComment: vi.fn(), setCommentResolved: vi.fn() },
-    };
-  });
-
-  it("resolve shows an Undo toast with autoClose=10000ms; reopen shows NO Undo", async () => {
-    vi.mocked(resolveComment).mockImplementation(async (data) =>
-      comment({
-        resolvedAt: data.resolved ? (new Date() as any) : null,
-      }),
-    );
-    const { wrapper } = seededClient(comment());
-    const { result } = renderHook(() => useResolveCommentMutation(), {
-      wrapper,
-    });
-
-    await result.current.mutateAsync({
-      commentId: "c-1",
-      pageId: PAGE_ID,
-      resolved: true,
-    });
-    await waitFor(() => expect(result.current.isSuccess).toBe(true));
-
-    const resolveToast = vi
-      .mocked(notifications.show)
-      .mock.calls.map((c) => c[0])
-      .find((a: any) => a?.autoClose === RESOLVE_UNDO_AUTOCLOSE_MS);
-    expect(resolveToast).toBeTruthy();
-    expect((resolveToast as any).id).toBe("resolve-undo-c-1");
-    expect((resolveToast as any).autoClose).toBe(10000);
-
-    // Now a reopen → plain toast, no autoClose/Undo, no id.
-    vi.clearAllMocks();
-    await result.current.mutateAsync({
-      commentId: "c-1",
-      pageId: PAGE_ID,
-      resolved: false,
-    });
-    await waitFor(() => expect(result.current.isSuccess).toBe(true));
-    const calls = vi.mocked(notifications.show).mock.calls.map((c) => c[0]);
-    expect(
-      calls.some((a: any) => a?.autoClose === RESOLVE_UNDO_AUTOCLOSE_MS),
-    ).toBe(false);
-    expect(calls).toContainEqual({ message: "Comment re-opened successfully" });
-  });
-
-  it("double/fast Undo click fires reopen EXACTLY once (guard)", async () => {
-    vi.mocked(resolveComment).mockImplementation(async (data) =>
-      comment({ resolvedAt: data.resolved ? (new Date() as any) : null }),
-    );
-    const { wrapper } = seededClient(comment());
-    const { result } = renderHook(() => useResolveCommentMutation(), {
-      wrapper,
-    });
-
-    await result.current.mutateAsync({
-      commentId: "c-1",
-      pageId: PAGE_ID,
-      resolved: true,
-    });
-    await waitFor(() => expect(result.current.isSuccess).toBe(true));
-
-    const onClick = undoOnClickFromToast();
-    // Fire twice synchronously (notifications.hide is not synchronous).
-    onClick();
-    onClick();
-
-    await waitFor(() => {
-      const reopenCalls = vi
-        .mocked(resolveComment)
-        .mock.calls.filter(([d]) => d.resolved === false);
-      expect(reopenCalls).toHaveLength(1);
-    });
-    // The mark was cleared once via setCommentResolved(id, false).
-    expect(editorMock.current!.commands.setCommentResolved).toHaveBeenCalledWith(
-      "c-1",
-      false,
-    );
-    // The toast was hidden.
-    expect(notifications.hide).toHaveBeenCalledWith("resolve-undo-c-1");
-  });
-
-  it("404 → drops the comment from cache, clears the inline mark, no rollback, no Undo", async () => {
-    vi.mocked(resolveComment).mockRejectedValue({ response: { status: 404 } });
-    const { queryClient, wrapper } = seededClient(comment());
-    const { result } = renderHook(() => useResolveCommentMutation(), {
-      wrapper,
-    });
-
-    await result.current
-      .mutateAsync({ commentId: "c-1", pageId: PAGE_ID, resolved: true })
-      .catch(() => undefined);
-    await waitFor(() => expect(result.current.isError).toBe(true));
-
-    // Removed from cache (NOT rolled back to a phantom).
-    expect(items(queryClient)).toHaveLength(0);
-    // Inline mark cleared via unsetComment (mandatory — no panel row left to do it).
-    expect(editorMock.current!.commands.unsetComment).toHaveBeenCalledWith(
-      "c-1",
-    );
-    // Neutral message, red, and crucially NOT the success copy and NO Undo toast.
-    expect(notifications.show).toHaveBeenCalledWith({
-      message: "Comment no longer exists",
-      color: "red",
-    });
-    const calls = vi.mocked(notifications.show).mock.calls.map((c) => c[0]);
-    expect(
-      calls.some((a: any) => a?.autoClose === RESOLVE_UNDO_AUTOCLOSE_MS),
-    ).toBe(false);
-  });
-
-  it("404 does not crash when the editor is gone (read-only / panel closed)", async () => {
-    editorMock.current = null;
-    vi.mocked(resolveComment).mockRejectedValue({ response: { status: 404 } });
-    const { queryClient, wrapper } = seededClient(comment());
-    const { result } = renderHook(() => useResolveCommentMutation(), {
-      wrapper,
-    });
-
-    await result.current
-      .mutateAsync({ commentId: "c-1", pageId: PAGE_ID, resolved: true })
-      .catch(() => undefined);
-    await waitFor(() => expect(result.current.isError).toBe(true));
-    expect(items(queryClient)).toHaveLength(0);
-    expect(notifications.show).toHaveBeenCalledWith({
-      message: "Comment no longer exists",
-      color: "red",
-    });
-  });
-
-  it("non-404 error on REOPEN shows 'Failed to re-open comment' and rolls back", async () => {
-    vi.mocked(resolveComment).mockRejectedValue({ response: { status: 500 } });
-    // Seed a RESOLVED comment (the reopen target).
-    const resolved = comment({ resolvedAt: new Date() as any });
-    const { queryClient, wrapper } = seededClient(resolved);
-    const { result } = renderHook(() => useResolveCommentMutation(), {
-      wrapper,
-    });
-
-    await result.current
-      .mutateAsync({ commentId: "c-1", pageId: PAGE_ID, resolved: false })
-      .catch(() => undefined);
-    await waitFor(() => expect(result.current.isError).toBe(true));
-
-    expect(notifications.show).toHaveBeenCalledWith({
-      message: "Failed to re-open comment",
-      color: "red",
-    });
-    expect(notifications.show).not.toHaveBeenCalledWith(
-      expect.objectContaining({ message: "Failed to resolve comment" }),
-    );
-    // Rolled back: the comment is still present and still resolved.
-    expect(items(queryClient)).toHaveLength(1);
-    expect(items(queryClient)[0].resolvedAt).toBeTruthy();
-  });
-
-  it("reopen via Undo FAILS (non-404) → inline mark is NOT left cleared (doc↔panel stay consistent)", async () => {
-    // First resolve succeeds → produces the Undo toast (no mark change on resolve).
-    vi.mocked(resolveComment).mockResolvedValueOnce(
-      comment({ resolvedAt: new Date() as any }),
-    );
-    const { queryClient, wrapper } = seededClient(comment());
-    const { result } = renderHook(() => useResolveCommentMutation(), {
-      wrapper,
-    });
-
-    await result.current.mutateAsync({
-      commentId: "c-1",
-      pageId: PAGE_ID,
-      resolved: true,
-    });
-    await waitFor(() => expect(result.current.isSuccess).toBe(true));
-
-    // Now the reopen fired by Undo fails with a 500.
-    vi.mocked(resolveComment).mockRejectedValue({ response: { status: 500 } });
-    const onClick = undoOnClickFromToast();
-    onClick();
-
-    await waitFor(() => expect(result.current.isError).toBe(true));
-
-    // Core F1 guarantee: the mark-clear now lives in the reopen onSuccess, so a
-    // FAILED reopen must never flip the inline mark to unresolved — otherwise the
-    // doc would show an active highlight the panel still treats as resolved and
-    // the collab mark would diverge with nothing committed on the server.
-    expect(
-      editorMock.current!.commands.setCommentResolved,
-    ).not.toHaveBeenCalledWith("c-1", false);
-    // Cache rolled back: the comment stays resolved and present.
-    expect(items(queryClient)).toHaveLength(1);
-    expect(items(queryClient)[0].resolvedAt).toBeTruthy();
-  });
-
-  it("reopen success with a null editorRef degrades gracefully (no throw, no-op)", async () => {
-    // Read-only view / panel closed: pageEditorAtom is null on the success path.
-    editorMock.current = null;
-    vi.mocked(resolveComment).mockResolvedValue(comment({ resolvedAt: null }));
-    const resolved = comment({ resolvedAt: new Date() as any });
-    const { queryClient, wrapper } = seededClient(resolved);
-    const { result } = renderHook(() => useResolveCommentMutation(), {
-      wrapper,
-    });
-
-    await result.current.mutateAsync({
-      commentId: "c-1",
-      pageId: PAGE_ID,
-      resolved: false,
-    });
-    await waitFor(() => expect(result.current.isSuccess).toBe(true));
-
-    // No crash from the reopen mark-clear; the plain reopen toast is still shown.
-    expect(notifications.show).toHaveBeenCalledWith({
-      message: "Comment re-opened successfully",
-    });
-    // Cache updated to reopened (resolvedAt cleared by the server payload).
-    expect(items(queryClient)).toHaveLength(1);
-    expect(items(queryClient)[0].resolvedAt).toBeFalsy();
-  });
-
-  it("non-404 error on RESOLVE shows 'Failed to resolve comment' and rolls back", async () => {
-    vi.mocked(resolveComment).mockRejectedValue({ response: { status: 500 } });
-    const { queryClient, wrapper } = seededClient(comment());
-    const { result } = renderHook(() => useResolveCommentMutation(), {
-      wrapper,
-    });
-
-    await result.current
-      .mutateAsync({ commentId: "c-1", pageId: PAGE_ID, resolved: true })
-      .catch(() => undefined);
-    await waitFor(() => expect(result.current.isError).toBe(true));
-
-    expect(notifications.show).toHaveBeenCalledWith({
-      message: "Failed to resolve comment",
-      color: "red",
-    });
-    // Rolled back to open (previousCache), still present.
-    expect(items(queryClient)).toHaveLength(1);
-    expect(items(queryClient)[0].resolvedAt).toBeFalsy();
-  });
-});

apps/client/src/features/comment/queries/comment-query.ts

@@ -20,19 +20,12 @@ import {
   ISuggestionOutcome,
 } from "@/features/comment/types/comment.types";
 import { notifications } from "@mantine/notifications";
-import { Button, Group, Text } from "@mantine/core";
 import { IPagination } from "@/lib/types.ts";
 import { useTranslation } from "react-i18next";
-import React, { useEffect, useMemo, useRef } from "react";
-import { useAtomValue } from "jotai";
-import { pageEditorAtom } from "@/features/editor/atoms/editor-atoms";
+import { useEffect, useMemo } from "react";
 
 export const RQ_KEY = (pageId: string) => ["comments", pageId];
 
-// How long the resolve success toast (with its inline Undo) stays up before it
-// auto-closes. Policy constant — no env override.
-export const RESOLVE_UNDO_AUTOCLOSE_MS = 10000;
-
 export function useCommentsQuery(params: ICommentParams) {
   const query = useInfiniteQuery({
     queryKey: RQ_KEY(params.pageId),
@@ -383,25 +376,7 @@ export function useResolveCommentMutation() {
   const queryClient = useQueryClient();
   const { t } = useTranslation();
 
-  // Keep the live editor in a ref: the toast's Undo (and the 404 branch) must
-  // clear the inline comment mark AFTER the originating CommentListItem has
-  // unmounted (resolving pulls the comment out of the Open list, so its item is
-  // already gone by the time the 10s toast is clicked). In read-only view
-  // pageEditorAtom is null and the mark converges via the server's
-  // COMMENT_MARK_UPDATE job instead.
-  const editor = useAtomValue(pageEditorAtom);
-  const editorRef = useRef(editor);
-  editorRef.current = editor;
-
-  // Self-reference the mutation so the toast's Undo can re-invoke it (reopen)
-  // long after the triggering component unmounted. Declared BEFORE useMutation
-  // and assigned AFTER; the onClick reads mutationRef.current at CALL time, not
-  // definition time, so there is no initialization cycle.
-  const mutationRef = useRef<{
-    mutate: (vars: IResolveComment) => void;
-  } | null>(null);
-
-  const mutation = useMutation({
+  return useMutation({
     mutationFn: (data: IResolveComment) => resolveComment(data),
     onMutate: async (variables) => {
       await queryClient.cancelQueries({ queryKey: RQ_KEY(variables.pageId) });
@@ -426,39 +401,7 @@ export function useResolveCommentMutation() {
 
       return { previousCache };
     },
-    onError: (err: any, variables, context) => {
-      // Terminal 404: the comment was really deleted (missing comment or deleted
-      // page — access denial is 403, resolve is idempotent so no 400). Do NOT
-      // roll back (that would resurrect a phantom row in Resolved); instead drop
-      // it from the cache and clear its now-orphaned inline mark. Mirrors
-      // handleDeleteComment and the dismiss-mutation 404 branch.
-      if (err?.response?.status === 404) {
-        const cache = queryClient.getQueryData(RQ_KEY(variables.pageId)) as
-          | InfiniteData<IPagination<IComment>>
-          | undefined;
-        if (cache) {
-          queryClient.setQueryData(
-            RQ_KEY(variables.pageId),
-            removeCommentFromCache(cache, variables.commentId),
-          );
-        }
-        const ed = editorRef.current;
-        if (ed && !ed.isDestroyed) {
-          try {
-            ed.commands.unsetComment(variables.commentId);
-          } catch {
-            /* editor gone / mark already removed */
-          }
-        }
-        notifications.show({
-          message: t("Comment no longer exists"),
-          color: "red",
-        });
-        return;
-      }
-
-      // Generic failure: roll back the optimistic update and show a DIRECTIONAL
-      // error (resolve vs. reopen), not always "resolve".
+    onError: (_err, variables, context) => {
       if (context?.previousCache) {
         queryClient.setQueryData(
           RQ_KEY(variables.pageId),
@@ -466,9 +409,7 @@ export function useResolveCommentMutation() {
         );
       }
       notifications.show({
-        message: variables.resolved
-          ? t("Failed to resolve comment")
-          : t("Failed to re-open comment"),
+        message: t("Failed to resolve comment"),
         color: "red",
       });
     },
@@ -489,72 +430,11 @@ export function useResolveCommentMutation() {
         );
       }
 
-      // Reopen keeps the plain toast without an Undo.
-      if (!variables.resolved) {
-        // Clear the inline mark ONLY after the server confirms the reopen, so a
-        // failed reopen never leaves an active highlight the panel still treats
-        // as resolved. Mirrors the 404 branch's editor-liveness guard/try-catch.
-        // The button-triggered reopen already set the mark, so this is an
-        // idempotent no-op there.
-        const ed = editorRef.current;
-        if (ed && !ed.isDestroyed) {
-          try {
-            ed.commands.setCommentResolved(variables.commentId, false);
-          } catch {
-            /* editor gone — server COMMENT_MARK_UPDATE converges it */
-          }
-        }
-        notifications.show({ message: t("Comment re-opened successfully") });
-        return;
-      }
-
-      // Resolve: attach an inline Undo (reopen) to the success toast. Built with
-      // React.createElement because this is a .ts module (no JSX).
-      const { commentId, pageId } = variables;
-      const notificationId = `resolve-undo-${commentId}`;
-      // Double-click guard: notifications.hide is NOT synchronous, so the button
-      // stays clickable for a frame or two — without this a fast double-click
-      // would fire reopen twice.
-      let done = false;
       notifications.show({
-        id: notificationId,
-        autoClose: RESOLVE_UNDO_AUTOCLOSE_MS,
-        message: React.createElement(
-          Group,
-          { justify: "space-between", wrap: "nowrap", gap: "md" },
-          React.createElement(
-            Text,
-            { size: "sm" },
-            t("Comment resolved successfully"),
-          ),
-          React.createElement(
-            Button,
-            {
-              variant: "subtle",
-              size: "compact-sm",
-              onClick: () => {
-                if (done) return;
-                done = true;
-                // Reopen via the SAME mutation (read at click time — the
-                // originating item is already unmounted).
-                mutationRef.current?.mutate({
-                  commentId,
-                  pageId,
-                  resolved: false,
-                });
-                // The inline mark is cleared in the reopen mutation's onSuccess
-                // (bound to server confirmation), NOT here — clearing it eagerly
-                // would desync the doc from the panel if reopen then fails.
-                notifications.hide(notificationId);
-              },
-            },
-            t("Undo"),
-          ),
-        ),
+        message: variables.resolved
+          ? t("Comment resolved successfully")
+          : t("Comment re-opened successfully"),
       });
     },
   });
-
-  mutationRef.current = mutation;
-  return mutation;
 }

apps/client/src/features/page-history/work-time/format-work-time.test.ts

@@ -0,0 +1,45 @@
+import { describe, it, expect } from "vitest";
+import {
+  formatHeadline,
+  formatDayTotal,
+  formatGapMinutes,
+} from "./format-work-time";
+
+const MIN = 60 * 1000;
+// Fake translator: renders the key with {{tokens}} substituted, so the tests
+// assert the rounding + branch selection without depending on the i18n catalogue.
+const t = (key: string, opts?: Record<string, unknown>) =>
+  key.replace(/\{\{(\w+)\}\}/g, (_, k) => String(opts?.[k] ?? ""));
+
+describe("formatHeadline", () => {
+  it("prefixes ≈ and rounds to a 5-minute step", () => {
+    expect(formatHeadline(4 * 60 * MIN + 27 * MIN, t)).toBe("≈ 4h 25m");
+    expect(formatHeadline(90 * MIN, t)).toBe("≈ 1h 30m");
+  });
+
+  it("shows hours only / minutes only cleanly", () => {
+    expect(formatHeadline(120 * MIN, t)).toBe("≈ 2h");
+    expect(formatHeadline(35 * MIN, t)).toBe("≈ 35m");
+  });
+
+  it("floors a tiny non-zero estimate to 5m, never 0", () => {
+    expect(formatHeadline(2 * MIN, t)).toBe("≈ 5m");
+  });
+
+  it("empty string for zero (widget hidden)", () => {
+    expect(formatHeadline(0, t)).toBe("");
+  });
+});
+
+describe("formatDayTotal", () => {
+  it('renders "h m" and shows — for empty days', () => {
+    expect(formatDayTotal(3 * 60 * MIN + 17 * MIN, t)).toBe("3h 17m");
+    expect(formatDayTotal(0, t)).toBe("—");
+  });
+});
+
+describe("formatGapMinutes", () => {
+  it("converts the tGap ms threshold to whole minutes", () => {
+    expect(formatGapMinutes(15 * MIN)).toBe(15);
+  });
+});

apps/client/src/features/page-history/work-time/format-work-time.ts

@@ -0,0 +1,45 @@
+// #395 — display formatting for the work-time estimate. Pure functions that take
+// a translator so ru-RU / en-US wording lives in the i18n catalogue and the
+// rounding logic stays unit-testable.
+
+type Translate = (key: string, opts?: Record<string, unknown>) => string;
+
+const MIN = 60 * 1000;
+
+function hm(totalMinutes: number): { hours: number; minutes: number } {
+  return {
+    hours: Math.floor(totalMinutes / 60),
+    minutes: totalMinutes % 60,
+  };
+}
+
+/**
+ * Headline number (§6.1): an ESTIMATE, so rounded to a coarse 5-minute step and
+ * prefixed with "≈". A non-zero-but-tiny estimate floors to 5m rather than
+ * rounding down to "0" (which would read as "no work"). Zero → empty string
+ * (the caller hides the widget).
+ */
+export function formatHeadline(workMs: number, t: Translate): string {
+  if (workMs <= 0) return "";
+  let minutes = Math.round(workMs / MIN / 5) * 5;
+  if (minutes === 0) minutes = 5;
+  const { hours, minutes: m } = hm(minutes);
+  if (hours > 0 && m > 0) return t("≈ {{hours}}h {{minutes}}m", { hours, minutes: m });
+  if (hours > 0) return t("≈ {{hours}}h", { hours });
+  return t("≈ {{minutes}}m", { minutes: m });
+}
+
+/** Per-day sum (§6.2), rounded to the minute. Zero → "—". */
+export function formatDayTotal(activeMs: number, t: Translate): string {
+  if (activeMs <= 0) return "—";
+  const minutes = Math.max(1, Math.round(activeMs / MIN));
+  const { hours, minutes: m } = hm(minutes);
+  if (hours > 0 && m > 0) return t("{{hours}}h {{minutes}}m", { hours, minutes: m });
+  if (hours > 0) return t("{{hours}}h", { hours });
+  return t("{{minutes}}m", { minutes: m });
+}
+
+/** The inactivity threshold, for the "estimate · gap = N min" caption. */
+export function formatGapMinutes(tGapMs: number): number {
+  return Math.round(tGapMs / MIN);
+}

apps/client/src/features/page-history/work-time/use-page-work-time.ts

@@ -0,0 +1,25 @@
+import { useQuery, UseQueryResult } from "@tanstack/react-query";
+import { IPageWorkTime } from "./work-time.types";
+import { getPageWorkTime, viewerTimezone } from "./work-time-service";
+
+const WORK_TIME_STALE_TIME = 5 * 60 * 1000;
+
+/**
+ * #395 — the "time worked on this article" estimate + per-day punch-card
+ * buckets. The buckets are computed server-side in the viewer's timezone (so a
+ * midnight-crossing session lands on the right calendar day for the reader).
+ * `enabled` is opt-in so the (cheap but non-trivial) projection query only fires
+ * when the number is actually shown.
+ */
+export function usePageWorkTime(
+  pageId: string,
+  enabled = true,
+): UseQueryResult<IPageWorkTime, Error> {
+  const tz = viewerTimezone();
+  return useQuery({
+    queryKey: ["page-work-time", pageId, tz],
+    queryFn: () => getPageWorkTime(pageId, tz),
+    enabled: enabled && !!pageId,
+    staleTime: WORK_TIME_STALE_TIME,
+  });
+}

apps/client/src/features/page-history/work-time/work-time-punch-card.tsx

@@ -0,0 +1,171 @@
+import { Group, Stack, Text } from "@mantine/core";
+import { useTranslation } from "react-i18next";
+import { useMemo } from "react";
+import { IPageWorkTime, IPerDay, IDayWindow } from "./work-time.types";
+import {
+  formatDayTotal,
+  formatGapMinutes,
+  formatHeadline,
+} from "./format-work-time";
+import classes from "./work-time.module.css";
+
+const DAY_MS = 24 * 60 * 60 * 1000;
+// Collapse a run of this many (or more) consecutive edit-free days into a single
+// "× N days" separator (§6.2 long-range) — the row is still always one day.
+const EMPTY_RUN_COLLAPSE = 8;
+
+type Row =
+  | { type: "day"; day: IPerDay }
+  | { type: "gap"; count: number };
+
+function collapseEmptyRuns(perDay: IPerDay[]): Row[] {
+  const rows: Row[] = [];
+  let emptyRun: IPerDay[] = [];
+  const flush = () => {
+    if (emptyRun.length >= EMPTY_RUN_COLLAPSE) {
+      rows.push({ type: "gap", count: emptyRun.length });
+    } else {
+      for (const d of emptyRun) rows.push({ type: "day", day: d });
+    }
+    emptyRun = [];
+  };
+  for (const d of perDay) {
+    if (d.activeMs === 0 && d.agentMs === 0) {
+      emptyRun.push(d);
+    } else {
+      flush();
+      rows.push({ type: "day", day: d });
+    }
+  }
+  flush();
+  return rows;
+}
+
+function dayHeading(day: number): string {
+  return new Date(day).toLocaleDateString(undefined, {
+    weekday: "short",
+    day: "numeric",
+    month: "short",
+  });
+}
+
+function DayTrack({
+  day,
+  pSingle,
+}: {
+  day: IPerDay;
+  pSingle: number;
+}) {
+  const { t } = useTranslation();
+  const ticks = [6, 12, 18];
+  return (
+    <div className={classes.row}>
+      <span className={classes.dayLabel}>{dayHeading(day.day)}</span>
+      <div className={classes.track}>
+        {ticks.map((h) => (
+          <div
+            key={h}
+            className={classes.hourTick}
+            style={{ left: `${(h / 24) * 100}%` }}
+          />
+        ))}
+        {day.windows.map((w: IDayWindow, i) => {
+          const leftPct = ((w.start - day.day) / DAY_MS) * 100;
+          const widthPct = ((w.end - w.start) / DAY_MS) * 100;
+          const isSingle = w.end - w.start <= pSingle;
+          const cls = [
+            classes.window,
+            w.class === "work" ? classes.windowWork : classes.windowAgent,
+            isSingle ? classes.windowSingle : "",
+          ].join(" ");
+          return (
+            <div
+              key={i}
+              className={cls}
+              style={{
+                left: `${Math.max(0, Math.min(100, leftPct))}%`,
+                width: `${Math.max(0, Math.min(100, widthPct))}%`,
+              }}
+            />
+          );
+        })}
+      </div>
+      <span className={classes.daySum}>
+        {formatDayTotal(day.activeMs, t)}
+      </span>
+    </div>
+  );
+}
+
+interface Props {
+  data: IPageWorkTime;
+}
+
+export default function WorkTimePunchCard({ data }: Props) {
+  const { t } = useTranslation();
+  const rows = useMemo(() => collapseEmptyRuns(data.perDay), [data.perDay]);
+  const gapMin = formatGapMinutes(data.config.tGap);
+
+  if (data.workMs <= 0 && data.agentOnlyMs <= 0) {
+    return (
+      <Text size="sm" c="dimmed" py="md">
+        {t("No editing activity recorded yet.")}
+      </Text>
+    );
+  }
+
+  return (
+    <Stack gap="xs">
+      <Group gap="lg">
+        <Text size="sm" fw={500}>
+          {formatHeadline(data.workMs, t)}
+        </Text>
+        {data.agentOnlyMs > 0 && (
+          <Text size="xs" c="dimmed">
+            {t("agent: {{value}}", { value: formatHeadline(data.agentOnlyMs, t) })}
+          </Text>
+        )}
+      </Group>
+
+      <Group gap="md">
+        <Text size="xs" c="dimmed">
+          <span
+            className={`${classes.legendSwatch} ${classes.windowWork}`}
+            style={{ marginRight: 4 }}
+          />
+          {t("Work")}
+        </Text>
+        <Text size="xs" c="dimmed">
+          <span
+            className={`${classes.legendSwatch} ${classes.windowAgent}`}
+            style={{ marginRight: 4 }}
+          />
+          {t("Agent")}
+        </Text>
+      </Group>
+
+      <div>
+        {rows.map((row, i) =>
+          row.type === "day" ? (
+            <DayTrack
+              key={row.day.dayISO}
+              day={row.day}
+              pSingle={data.config.pSingle}
+            />
+          ) : (
+            <div key={`gap-${i}`} className={classes.gapRow}>
+              {t("× {{count}} days without edits", { count: row.count })}
+            </div>
+          ),
+        )}
+      </div>
+
+      <Text size="xs" c="dimmed" mt="xs">
+        {t("Estimate · timezone {{tz}} · inactivity gap {{gap}} min", {
+          tz: data.tz,
+          gap: gapMin,
+        })}
+      </Text>
+    </Stack>
+  );
+}

apps/client/src/features/page-history/work-time/work-time-service.ts

@@ -0,0 +1,23 @@
+import api from "@/lib/api-client";
+import { IPageWorkTime } from "./work-time.types";
+
+/** The viewer's IANA timezone (browser locale) — the punch-card lays days out
+ *  in "my evenings", per §6.3/§10. Falls back to UTC if the runtime hides it. */
+export function viewerTimezone(): string {
+  try {
+    return Intl.DateTimeFormat().resolvedOptions().timeZone || "UTC";
+  } catch {
+    return "UTC";
+  }
+}
+
+export async function getPageWorkTime(
+  pageId: string,
+  tz: string,
+): Promise<IPageWorkTime> {
+  const req = await api.post<IPageWorkTime>("/pages/history/time", {
+    pageId,
+    tz,
+  });
+  return req.data;
+}

apps/client/src/features/page-history/work-time/work-time-stat.tsx

@@ -0,0 +1,69 @@
+import { Modal, Text, Tooltip, UnstyledButton } from "@mantine/core";
+import { useDisclosure } from "@mantine/hooks";
+import { IconClockHour4 } from "@tabler/icons-react";
+import { useTranslation } from "react-i18next";
+import { usePageWorkTime } from "./use-page-work-time";
+import { formatGapMinutes, formatHeadline } from "./format-work-time";
+import WorkTimePunchCard from "./work-time-punch-card";
+
+interface Props {
+  pageId: string;
+}
+
+/**
+ * #395 — the clickable "time worked on this article" headline (§6.1). Renders
+ * the `work` estimate with a "≈" sign and the inactivity threshold in a tooltip
+ * (it is an estimate, not a stopwatch). Clicking opens the daily punch-card
+ * (§6.2). Renders nothing until there is a non-zero human OR agent estimate, so a
+ * brand-new / never-edited page shows no widget. For an agent-only-edited page
+ * (workMs===0, agentOnlyMs>0) the headline shows the agent estimate (labelled
+ * `agent:`, matching the punch-card) so the punch-card stays reachable (#395:
+ * "how much a HUMAN and separately the AGENT").
+ */
+export default function WorkTimeStat({ pageId }: Props) {
+  const { t } = useTranslation();
+  const [opened, { open, close }] = useDisclosure(false);
+  const { data } = usePageWorkTime(pageId);
+
+  if (!data || (data.workMs <= 0 && data.agentOnlyMs <= 0)) return null;
+
+  const agentOnly = data.workMs <= 0;
+  const label = agentOnly
+    ? t("agent: {{value}}", { value: formatHeadline(data.agentOnlyMs, t) })
+    : formatHeadline(data.workMs, t);
+  const gapMin = formatGapMinutes(data.config.tGap);
+
+  return (
+    <>
+      <Tooltip
+        label={t("Estimated time worked (inactivity gap {{gap}} min)", {
+          gap: gapMin,
+        })}
+        position="bottom"
+      >
+        <UnstyledButton
+          onClick={open}
+          aria-label={t("Show time worked on this page")}
+        >
+          <Text
+            size="xs"
+            c="dimmed"
+            style={{ display: "inline-flex", alignItems: "center", gap: 4 }}
+          >
+            <IconClockHour4 size={14} />
+            {label}
+          </Text>
+        </UnstyledButton>
+      </Tooltip>
+
+      <Modal
+        opened={opened}
+        onClose={close}
+        title={t("Time worked on this article")}
+        size="lg"
+      >
+        <WorkTimePunchCard data={data} />
+      </Modal>
+    </>
+  );
+}

apps/client/src/features/page-history/work-time/work-time.module.css

@@ -0,0 +1,82 @@
+/* #395 — 24h × days punch-card. Custom CSS segments on a fixed 24-hour track
+   (position = offset-in-day / 24h, width = duration / 24h), no chart library. */
+
+.row {
+  display: grid;
+  grid-template-columns: 96px 1fr 64px;
+  align-items: center;
+  gap: 12px;
+  padding: 3px 0;
+}
+
+.dayLabel {
+  font-size: var(--mantine-font-size-xs);
+  color: var(--mantine-color-dimmed);
+  white-space: nowrap;
+}
+
+.track {
+  position: relative;
+  height: 16px;
+  border-radius: 4px;
+  background-color: light-dark(
+    var(--mantine-color-gray-1),
+    var(--mantine-color-dark-6)
+  );
+  overflow: hidden;
+}
+
+/* Faint hour grid so the eye can read "morning vs evening". */
+.hourTick {
+  position: absolute;
+  top: 0;
+  bottom: 0;
+  width: 1px;
+  background-color: light-dark(
+    var(--mantine-color-gray-3),
+    var(--mantine-color-dark-4)
+  );
+}
+
+.window {
+  position: absolute;
+  top: 2px;
+  bottom: 2px;
+  border-radius: 3px;
+  min-width: 3px;
+}
+
+.windowWork {
+  background-color: var(--mantine-color-blue-5);
+}
+
+.windowAgent {
+  background-color: var(--mantine-color-grape-5);
+}
+
+/* A lone single-sample (P_single) window: minimal + dimmed, so it neither
+   vanishes nor fakes dense work (§6.2). */
+.windowSingle {
+  opacity: 0.5;
+}
+
+.daySum {
+  font-size: var(--mantine-font-size-xs);
+  text-align: right;
+  white-space: nowrap;
+}
+
+.gapRow {
+  padding: 6px 0 6px 108px;
+  font-size: var(--mantine-font-size-xs);
+  color: var(--mantine-color-dimmed);
+  font-style: italic;
+}
+
+.legendSwatch {
+  display: inline-block;
+  width: 12px;
+  height: 12px;
+  border-radius: 3px;
+  vertical-align: middle;
+}

apps/client/src/features/page-history/work-time/work-time.types.ts

@@ -0,0 +1,37 @@
+// #395 — client-side mirror of the server work-time payload
+// (apps/server/src/core/page/work-time). Shapes returned by POST /pages/history/time.
+
+export type WorkSessionClass = "work" | "agent_only";
+
+export interface IDayWindow {
+  start: number;
+  end: number;
+  class: WorkSessionClass;
+}
+
+export interface IPerDay {
+  day: number;
+  dayISO: string;
+  activeMs: number;
+  agentMs: number;
+  windows: IDayWindow[];
+}
+
+export interface IWorkTimeConfig {
+  tGap: number;
+  agentTGap: number;
+  pIn: number;
+  pOut: number;
+  pSingle: number;
+  excludeGit: boolean;
+  burstCapMs?: number;
+  dedupRoundMs: number;
+}
+
+export interface IPageWorkTime {
+  workMs: number;
+  agentOnlyMs: number;
+  perDay: IPerDay[];
+  config: IWorkTimeConfig;
+  tz: string;
+}

apps/client/src/features/page/components/header/page-header-menu.tsx

@@ -51,6 +51,7 @@ import {
 import { formattedDate } from "@/lib/time.ts";
 import { PageEditModeToggle } from "@/features/user/components/page-state-pref.tsx";
 import MovePageModal from "@/features/page/components/move-page-modal.tsx";
+import WorkTimeStat from "@/features/page-history/work-time/work-time-stat.tsx";
 import { useTimeAgo } from "@/hooks/use-time-ago.tsx";
 import {
   useFavoriteIds,
@@ -265,6 +266,8 @@ function PageActionMenu({ readOnly, onSaveVersion }: PageActionMenuProps) {
 
   return (
     <>
+      {page?.id && <WorkTimeStat pageId={page.id} />}
+
       <Menu
         shadow="xl"
         position="bottom-end"

apps/server/src/core/page/dto/page.dto.ts

@@ -5,6 +5,7 @@ import {
   IsOptional,
   IsString,
   IsUUID,
+  MaxLength,
 } from 'class-validator';
 import { Transform } from 'class-transformer';
 
@@ -47,6 +48,17 @@ export class PageInfoDto extends PageIdDto {
   format?: ContentFormat;
 }
 
+export class PageWorkTimeDto extends PageIdDto {
+  // Viewer IANA timezone for the per-day punch-card buckets (§6.3). Optional —
+  // falls back to UTC server-side. Length-capped so a bogus value cannot bloat
+  // the request; the value is only ever handed to Intl.DateTimeFormat, which
+  // throws on an unknown zone (caught by the controller → 400).
+  @IsOptional()
+  @IsString()
+  @MaxLength(64)
+  tz?: string;
+}
+
 export class DeletePageDto extends PageIdDto {
   @IsOptional()
   @IsBoolean()

apps/server/src/core/page/page.controller.spec.ts

@@ -1,3 +1,8 @@
+import {
+  BadRequestException,
+  ForbiddenException,
+  NotFoundException,
+} from '@nestjs/common';
 import { PageController } from './page.controller';
 
 // Direct instantiation with stub deps. The Test.createTestingModule form failed
@@ -22,4 +27,88 @@ describe('PageController', () => {
   it('should be defined', () => {
     expect(controller).toBeDefined();
   });
+
+  // #395 — the work-time endpoint must be gated exactly like /history.
+  describe('getPageWorkTime', () => {
+    const user = { id: 'u1' } as any;
+
+    function build(overrides: {
+      page?: any;
+      validate?: jest.Mock;
+      compute?: jest.Mock;
+    }) {
+      const pageRepo = { findById: jest.fn().mockResolvedValue(overrides.page) };
+      const pageAccessService = {
+        validateCanView: overrides.validate ?? jest.fn().mockResolvedValue(undefined),
+      };
+      const pageHistoryService = {
+        computeWorkTime:
+          overrides.compute ?? jest.fn().mockResolvedValue({ workMs: 0 }),
+      };
+      const c = new PageController(
+        {} as any,
+        pageRepo as any,
+        pageHistoryService as any,
+        {} as any,
+        pageAccessService as any,
+        {} as any,
+        {} as any,
+        {} as any,
+      );
+      return { c, pageRepo, pageAccessService, pageHistoryService };
+    }
+
+    it('404s when the page does not exist', async () => {
+      const { c } = build({ page: null });
+      await expect(
+        c.getPageWorkTime({ pageId: 'p1' } as any, user),
+      ).rejects.toBeInstanceOf(NotFoundException);
+    });
+
+    it('enforces validateCanView before computing, then delegates with tz', async () => {
+      const validate = jest.fn().mockResolvedValue(undefined);
+      const compute = jest.fn().mockResolvedValue({ workMs: 42 });
+      const { c } = build({ page: { id: 'pg' }, validate, compute });
+      const out = await c.getPageWorkTime(
+        { pageId: 'pg', tz: 'Europe/Moscow' } as any,
+        user,
+      );
+      expect(validate).toHaveBeenCalledWith({ id: 'pg' }, user);
+      expect(compute).toHaveBeenCalledWith('pg', 'Europe/Moscow');
+      expect(out).toEqual({ workMs: 42 });
+    });
+
+    it('propagates a denied view gate and does NOT reach compute (security)', async () => {
+      // If validateCanView is moved AFTER computeWorkTime, the timeline of a page
+      // the caller may not see would be read/estimated before the gate — this
+      // locks the order: a rejecting gate must short-circuit before any compute.
+      const validate = jest.fn().mockRejectedValue(new ForbiddenException());
+      const compute = jest.fn().mockResolvedValue({ workMs: 1 });
+      const { c, pageHistoryService } = build({
+        page: { id: 'pg' },
+        validate,
+        compute,
+      });
+      await expect(
+        c.getPageWorkTime({ pageId: 'pg' } as any, user),
+      ).rejects.toBeInstanceOf(ForbiddenException);
+      expect(pageHistoryService.computeWorkTime).not.toHaveBeenCalled();
+    });
+
+    it('maps an unknown-timezone RangeError to a 400', async () => {
+      const compute = jest.fn().mockRejectedValue(new RangeError('bad tz'));
+      const { c } = build({ page: { id: 'pg' }, compute });
+      await expect(
+        c.getPageWorkTime({ pageId: 'pg', tz: 'X/Y' } as any, user),
+      ).rejects.toBeInstanceOf(BadRequestException);
+    });
+
+    it('does not swallow a non-RangeError from the service', async () => {
+      const compute = jest.fn().mockRejectedValue(new Error('db down'));
+      const { c } = build({ page: { id: 'pg' }, compute });
+      await expect(
+        c.getPageWorkTime({ pageId: 'pg' } as any, user),
+      ).rejects.toThrow('db down');
+    });
+  });
 });

apps/server/src/core/page/page.controller.ts

@@ -21,6 +21,7 @@ import {
   PageHistoryIdDto,
   PageIdDto,
   PageInfoDto,
+  PageWorkTimeDto,
 } from './dto/page.dto';
 import { PageHistoryService } from './services/page-history.service';
 import { AuthUser } from '../../common/decorators/auth-user.decorator';
@@ -524,6 +525,32 @@ export class PageController {
     return this.pageHistoryService.findHistoryByPageId(page.id, pagination);
   }
 
+  @HttpCode(HttpStatus.OK)
+  @Post('/history/time')
+  async getPageWorkTime(
+    @Body() dto: PageWorkTimeDto,
+    @AuthUser() user: User,
+  ) {
+    const page = await this.pageRepo.findById(dto.pageId);
+    if (!page) {
+      throw new NotFoundException('Page not found');
+    }
+
+    // Same view gate as /history and /history/info.
+    await this.pageAccessService.validateCanView(page, user);
+
+    try {
+      return await this.pageHistoryService.computeWorkTime(page.id, dto.tz);
+    } catch (e) {
+      // Intl.DateTimeFormat throws RangeError on an unknown IANA zone; surface
+      // it as a 400 rather than a 500.
+      if (e instanceof RangeError) {
+        throw new BadRequestException('Invalid timezone');
+      }
+      throw e;
+    }
+  }
+
   @HttpCode(HttpStatus.OK)
   @Post('/history/info')
   async getPageHistoryInfo(

apps/server/src/core/page/services/page-history.service.ts

@@ -3,6 +3,23 @@ import { PageHistoryRepo } from '@docmost/db/repos/page/page-history.repo';
 import { PageHistory } from '@docmost/db/types/entity.types';
 import { PaginationOptions } from '@docmost/db/pagination/pagination-options';
 import { CursorPaginationResult } from '@docmost/db/pagination/cursor-pagination';
+import {
+  computeWorkTime,
+  bucketByDay,
+  DEFAULT_WORK_TIME_CONFIG,
+  WorkTimeConfig,
+  PerDay,
+} from '../work-time';
+
+export interface PageWorkTime {
+  workMs: number;
+  agentOnlyMs: number;
+  perDay: PerDay[];
+  /** the config actually used, so the UI can show "≈" + the T_gap threshold. */
+  config: WorkTimeConfig;
+  /** the tz the per-day buckets were computed in (echoed back for the label). */
+  tz: string;
+}
 
 @Injectable()
 export class PageHistoryService {
@@ -23,4 +40,33 @@ export class PageHistoryService {
       paginationOptions,
     );
   }
+
+  /**
+   * #395 — estimate time worked on a page (§5) and bucket it into the viewer's
+   * calendar days for the punch-card (§6.3). Reads only the cheap history
+   * projection (no `content`); the estimate itself is a pure, deterministic
+   * function so it is unit-tested exhaustively without a DB.
+   *
+   * `tz` is the viewer's IANA zone (browser locale) — it moves which day a
+   * session lands in and where its windows sit, but never the total (§10).
+   */
+  async computeWorkTime(
+    pageId: string,
+    tz = 'UTC',
+    config?: Partial<WorkTimeConfig>,
+  ): Promise<PageWorkTime> {
+    const rows = await this.pageHistoryRepo.findTimelineByPageId(pageId);
+    const result = computeWorkTime(rows, config);
+    const usedConfig: WorkTimeConfig = { ...DEFAULT_WORK_TIME_CONFIG, ...config };
+    // `bucketByDay` consumes the pure core's un-bucketed sessions here; the
+    // full session list is NOT shipped on the response (no client reads it).
+    const perDay = bucketByDay(result.sessions, tz);
+    return {
+      workMs: result.workMs,
+      agentOnlyMs: result.agentOnlyMs,
+      perDay,
+      config: usedConfig,
+      tz,
+    };
+  }
 }

apps/server/src/core/page/work-time/bucket-by-day.spec.ts

@@ -0,0 +1,129 @@
+import { bucketByDay, zonedDayStart } from './bucket-by-day';
+import { computeWorkTime } from './compute-work-time';
+import { WorkSession, TimelineSample } from './work-time.types';
+
+const MIN = 60 * 1000;
+const HOUR = 60 * MIN;
+
+function work(start: number, end: number): WorkSession {
+  return { start, end, class: 'work' };
+}
+function agent(start: number, end: number): WorkSession {
+  return { start, end, class: 'agent_only' };
+}
+
+function sumActive(perDay: ReturnType<typeof bucketByDay>): number {
+  return perDay.reduce((a, d) => a + d.activeMs, 0);
+}
+
+describe('bucketByDay', () => {
+  it('Σ activeMs == workMs — the §6.3 consistency invariant', () => {
+    const rows: TimelineSample[] = [
+      { createdAt: '2026-07-04T03:40:00Z', lastUpdatedById: 'h', lastUpdatedSource: 'user', lastUpdatedAiChatId: null, kind: null },
+      { createdAt: '2026-07-04T03:49:00Z', lastUpdatedById: 'h', lastUpdatedSource: 'user', lastUpdatedAiChatId: null, kind: null },
+      { createdAt: '2026-07-04T18:11:00Z', lastUpdatedById: 'h', lastUpdatedSource: 'user', lastUpdatedAiChatId: null, kind: null },
+      { createdAt: '2026-07-06T15:34:00Z', lastUpdatedById: 'h', lastUpdatedSource: 'user', lastUpdatedAiChatId: null, kind: null },
+    ];
+    const r = computeWorkTime(rows);
+    const perDay = bucketByDay(r.sessions, 'UTC');
+    expect(sumActive(perDay)).toBe(r.workMs);
+  });
+
+  it('empty input → no days', () => {
+    expect(bucketByDay([], 'UTC')).toEqual([]);
+  });
+
+  it('midnight-crossing session splits across two days, sum preserved (§9#9)', () => {
+    const start = Date.UTC(2026, 0, 10, 23, 14);
+    const end = Date.UTC(2026, 0, 11, 0, 40);
+    const perDay = bucketByDay([work(start, end)], 'UTC');
+    expect(perDay).toHaveLength(2);
+    expect(perDay[0].dayISO).toBe('2026-01-10');
+    expect(perDay[1].dayISO).toBe('2026-01-11');
+    expect(perDay[0].activeMs).toBe(46 * MIN); // 23:14 → 24:00
+    expect(perDay[1].activeMs).toBe(40 * MIN); // 00:00 → 00:40
+    expect(sumActive(perDay)).toBe(end - start);
+  });
+
+  it('empty days between active days are emitted, not skipped (§9#12)', () => {
+    const d1 = work(Date.UTC(2026, 0, 10, 10, 0), Date.UTC(2026, 0, 10, 11, 0));
+    const d3 = work(Date.UTC(2026, 0, 12, 10, 0), Date.UTC(2026, 0, 12, 11, 0));
+    const perDay = bucketByDay([d1, d3], 'UTC');
+    expect(perDay.map((d) => d.dayISO)).toEqual([
+      '2026-01-10',
+      '2026-01-11',
+      '2026-01-12',
+    ]);
+    expect(perDay[1].activeMs).toBe(0);
+    expect(perDay[1].windows).toEqual([]);
+  });
+
+  it('agent_only windows are drawn but excluded from activeMs', () => {
+    const w = work(Date.UTC(2026, 0, 10, 9, 0), Date.UTC(2026, 0, 10, 10, 0));
+    const a = agent(Date.UTC(2026, 0, 10, 14, 0), Date.UTC(2026, 0, 10, 14, 30));
+    const perDay = bucketByDay([w, a], 'UTC');
+    expect(perDay).toHaveLength(1);
+    expect(perDay[0].activeMs).toBe(1 * HOUR);
+    expect(perDay[0].agentMs).toBe(30 * MIN);
+    expect(perDay[0].windows.map((x) => x.class)).toEqual(['work', 'agent_only']);
+  });
+
+  it('work and agent_only are unioned SEPARATELY (agent does not swallow work)', () => {
+    // Overlapping work + agent windows on the same day.
+    const w = work(Date.UTC(2026, 0, 10, 9, 0), Date.UTC(2026, 0, 10, 11, 0));
+    const a = agent(Date.UTC(2026, 0, 10, 10, 0), Date.UTC(2026, 0, 10, 12, 0));
+    const perDay = bucketByDay([w, a], 'UTC');
+    expect(perDay[0].activeMs).toBe(2 * HOUR);
+    expect(perDay[0].agentMs).toBe(2 * HOUR);
+  });
+
+  it('overlapping same-class sessions are UNIONed, not summed (no double-count)', () => {
+    // Two work sessions that overlap 10:00–10:30 on one day.
+    const a = work(Date.UTC(2026, 0, 10, 9, 0), Date.UTC(2026, 0, 10, 10, 30));
+    const b = work(Date.UTC(2026, 0, 10, 10, 0), Date.UTC(2026, 0, 10, 11, 0));
+    const perDay = bucketByDay([a, b], 'UTC');
+    expect(perDay).toHaveLength(1);
+    // Union 09:00–11:00 = 2h, NOT 90m + 60m = 150m.
+    expect(perDay[0].activeMs).toBe(2 * HOUR);
+    // The drawn windows are also merged to one, so the punch-card cannot render
+    // an overlapping double bar.
+    expect(perDay[0].windows).toHaveLength(1);
+    expect(perDay[0].windows[0].start).toBe(a.start);
+    expect(perDay[0].windows[0].end).toBe(b.end);
+  });
+
+  it('DST fall-back: a full 25-hour day still balances (§9#14)', () => {
+    // America/New_York ends DST 2026-11-01 (25h day).
+    const tz = 'America/New_York';
+    const dayStart = zonedDayStart(Date.UTC(2026, 10, 1, 12, 0), tz);
+    const nextStart = zonedDayStart(dayStart + 26 * HOUR, tz);
+    expect(nextStart - dayStart).toBe(25 * HOUR);
+    const perDay = bucketByDay([work(dayStart, nextStart)], tz);
+    expect(perDay).toHaveLength(1);
+    expect(perDay[0].dayISO).toBe('2026-11-01');
+    expect(perDay[0].activeMs).toBe(25 * HOUR);
+    expect(sumActive(perDay)).toBe(nextStart - dayStart);
+  });
+
+  it('DST spring-forward: a full 23-hour day still balances (§9#14)', () => {
+    // America/New_York starts DST 2026-03-08 (23h day).
+    const tz = 'America/New_York';
+    const dayStart = zonedDayStart(Date.UTC(2026, 2, 8, 12, 0), tz);
+    const nextStart = zonedDayStart(dayStart + 26 * HOUR, tz);
+    expect(nextStart - dayStart).toBe(23 * HOUR);
+    const perDay = bucketByDay([work(dayStart, nextStart)], tz);
+    expect(perDay).toHaveLength(1);
+    expect(perDay[0].activeMs).toBe(23 * HOUR);
+    expect(sumActive(perDay)).toBe(nextStart - dayStart);
+  });
+
+  it('tz changes the day a session lands in but not the total', () => {
+    const start = Date.UTC(2026, 0, 10, 2, 0); // 02:00 UTC
+    const end = Date.UTC(2026, 0, 10, 3, 0);
+    const utc = bucketByDay([work(start, end)], 'UTC');
+    const ny = bucketByDay([work(start, end)], 'America/New_York'); // 21:00 prev day
+    expect(utc[0].dayISO).toBe('2026-01-10');
+    expect(ny[0].dayISO).toBe('2026-01-09');
+    expect(sumActive(utc)).toBe(sumActive(ny));
+  });
+});

apps/server/src/core/page/work-time/bucket-by-day.ts

@@ -0,0 +1,180 @@
+import { WorkSession, PerDay, DayWindow } from './work-time.types';
+
+/**
+ * Merge intervals into a disjoint, sorted union. Overlapping OR touching
+ * intervals are joined. Empty input → [].
+ */
+function union(intervals: Array<[number, number]>): Array<[number, number]> {
+  if (intervals.length === 0) return [];
+  const sorted = [...intervals].sort((a, b) => a[0] - b[0]);
+  const out: Array<[number, number]> = [];
+  let [curStart, curEnd] = sorted[0];
+  for (let i = 1; i < sorted.length; i++) {
+    const [s, e] = sorted[i];
+    if (s <= curEnd) {
+      if (e > curEnd) curEnd = e;
+    } else {
+      out.push([curStart, curEnd]);
+      curStart = s;
+      curEnd = e;
+    }
+  }
+  out.push([curStart, curEnd]);
+  return out;
+}
+
+// Cache one Intl formatter per tz — constructing them is comparatively costly.
+const fmtCache = new Map<string, Intl.DateTimeFormat>();
+
+function partsFmt(tz: string): Intl.DateTimeFormat {
+  let fmt = fmtCache.get(tz);
+  if (!fmt) {
+    fmt = new Intl.DateTimeFormat('en-US', {
+      timeZone: tz,
+      year: 'numeric',
+      month: '2-digit',
+      day: '2-digit',
+      hour: '2-digit',
+      minute: '2-digit',
+      second: '2-digit',
+      hour12: false,
+    });
+    fmtCache.set(tz, fmt);
+  }
+  return fmt;
+}
+
+interface WallParts {
+  year: number;
+  month: number;
+  day: number;
+  hour: number;
+  minute: number;
+  second: number;
+}
+
+/** Wall-clock parts of an instant in `tz` (DST-correct, via Intl). */
+function wallParts(ms: number, tz: string): WallParts {
+  const parts = partsFmt(tz).formatToParts(new Date(ms));
+  const get = (type: string) =>
+    Number(parts.find((p) => p.type === type)?.value ?? '0');
+  let hour = get('hour');
+  // Intl emits "24" for midnight under some engines/locales; normalize to 0.
+  if (hour === 24) hour = 0;
+  return {
+    year: get('year'),
+    month: get('month'),
+    day: get('day'),
+    hour,
+    minute: get('minute'),
+    second: get('second'),
+  };
+}
+
+/** tz offset (wall − real) at an instant, in ms. */
+function offset(ms: number, tz: string): number {
+  const p = wallParts(ms, tz);
+  const asUTC = Date.UTC(p.year, p.month - 1, p.day, p.hour, p.minute, p.second);
+  return asUTC - ms;
+}
+
+/**
+ * Epoch-ms of the local-midnight day start of `ms` in `tz`. DST-correct: takes
+ * the calendar day of the instant, its wall-midnight, then converts back with
+ * the offset that actually applies AT that midnight (refined once). The rare
+ * tz-with-a-DST-transition-exactly-at-midnight case is a documented edge (§9#14).
+ */
+export function zonedDayStart(ms: number, tz: string): number {
+  const p = wallParts(ms, tz);
+  const wallMidnightAsUTC = Date.UTC(p.year, p.month - 1, p.day, 0, 0, 0);
+  let start = wallMidnightAsUTC - offset(ms, tz);
+  // Refine with the offset at the computed midnight (DST may differ from `ms`).
+  start = wallMidnightAsUTC - offset(start, tz);
+  return start;
+}
+
+/** The next local midnight after `dayStart` (handles 23/25h DST days). */
+function nextDayStart(dayStart: number, tz: string): number {
+  // +26h always lands inside the NEXT calendar day (day length ∈ [23h,25h]),
+  // never two days ahead; startOf('day') of it is the next midnight.
+  return zonedDayStart(dayStart + 26 * 60 * 60 * 1000, tz);
+}
+
+function isoDay(dayStart: number, tz: string): string {
+  const p = wallParts(dayStart, tz);
+  const pad = (n: number) => String(n).padStart(2, '0');
+  return `${p.year}-${pad(p.month)}-${pad(p.day)}`;
+}
+
+/** Clip a union to [lo, hi) and emit windows of `class`. */
+function clip(
+  merged: Array<[number, number]>,
+  lo: number,
+  hi: number,
+  cls: DayWindow['class'],
+): DayWindow[] {
+  const out: DayWindow[] = [];
+  for (const [s, e] of merged) {
+    const start = Math.max(s, lo);
+    const end = Math.min(e, hi);
+    if (end > start) out.push({ start, end, class: cls });
+  }
+  return out;
+}
+
+/**
+ * #395 §6.3 — bucket sessions into calendar days of `tz` for the punch-card.
+ * Pure and deterministic. `work` and `agent_only` are unioned SEPARATELY (else
+ * agent windows would swallow work windows on overlap), then each union is split
+ * at tz midnight boundaries (`startOf('day')` in tz, NOT "+24h" — DST-safe §9#14)
+ * and clipped to each day.
+ *
+ * By construction Σ perDay.activeMs == workMs: the days are a partition of the
+ * `work` union — no loss, no dup, even on 23/25h DST days. `agent_only` windows
+ * are drawn but NOT in activeMs. Empty days between the first and last active day
+ * are emitted (empty track + "—") so the rhythm/pauses stay visible.
+ */
+export function bucketByDay(sessions: WorkSession[], tz: string): PerDay[] {
+  const uWork = union(
+    sessions.filter((s) => s.class === 'work').map((s) => [s.start, s.end]),
+  );
+  const uAgent = union(
+    sessions
+      .filter((s) => s.class === 'agent_only')
+      .map((s) => [s.start, s.end]),
+  );
+
+  if (uWork.length === 0 && uAgent.length === 0) return [];
+
+  const minStart = Math.min(
+    uWork.length ? uWork[0][0] : Infinity,
+    uAgent.length ? uAgent[0][0] : Infinity,
+  );
+  const maxEnd = Math.max(
+    uWork.length ? uWork[uWork.length - 1][1] : -Infinity,
+    uAgent.length ? uAgent[uAgent.length - 1][1] : -Infinity,
+  );
+
+  const perDay: PerDay[] = [];
+  let dayStart = zonedDayStart(minStart, tz);
+  // Guard against a pathological non-advancing boundary.
+  let guard = 0;
+  while (dayStart < maxEnd && guard < 100000) {
+    guard++;
+    const dayEnd = nextDayStart(dayStart, tz);
+    const workWin = clip(uWork, dayStart, dayEnd, 'work');
+    const agentWin = clip(uAgent, dayStart, dayEnd, 'agent_only');
+    const activeMs = workWin.reduce((a, w) => a + (w.end - w.start), 0);
+    const agentMs = agentWin.reduce((a, w) => a + (w.end - w.start), 0);
+    const windows = [...workWin, ...agentWin].sort((a, b) => a.start - b.start);
+    perDay.push({
+      day: dayStart,
+      dayISO: isoDay(dayStart, tz),
+      activeMs,
+      agentMs,
+      windows,
+    });
+    dayStart = dayEnd;
+  }
+  return perDay;
+}

apps/server/src/core/page/work-time/compute-work-time.spec.ts

@@ -0,0 +1,358 @@
+import { computeWorkTime } from './compute-work-time';
+import { bucketByDay } from './bucket-by-day';
+import { TimelineSample, WorkSession } from './work-time.types';
+
+const MIN = 60 * 1000;
+
+/** Union wall-clock of a set of intervals (touching intervals merge). */
+function unionMs(intervals: Array<[number, number]>): number {
+  if (intervals.length === 0) return 0;
+  const sorted = [...intervals].sort((a, b) => a[0] - b[0]);
+  let total = 0;
+  let [cs, ce] = sorted[0];
+  for (let i = 1; i < sorted.length; i++) {
+    const [s, e] = sorted[i];
+    if (s <= ce) {
+      if (e > ce) ce = e;
+    } else {
+      total += ce - cs;
+      cs = s;
+      ce = e;
+    }
+  }
+  return total + (ce - cs);
+}
+
+const ivsOf = (sessions: WorkSession[], cls?: string): Array<[number, number]> =>
+  sessions
+    .filter((x) => cls == null || x.class === cls)
+    .map((x) => [x.start, x.end] as [number, number]);
+
+function s(
+  iso: string,
+  opts: {
+    source?: string | null;
+    chat?: string | null;
+    kind?: string | null;
+    by?: string | null;
+  } = {},
+): TimelineSample {
+  return {
+    createdAt: `${iso}Z`,
+    lastUpdatedById: opts.by ?? 'human-1',
+    lastUpdatedSource: opts.source === undefined ? 'user' : opts.source,
+    lastUpdatedAiChatId: opts.chat ?? null,
+    kind: opts.kind ?? null,
+  };
+}
+
+// §7 config: T_gap=30m, P_in+P_out=10m, P_single=2m.
+const S7 = { tGap: 30 * MIN, agentTGap: 30 * MIN, pIn: 5 * MIN, pOut: 5 * MIN, pSingle: 2 * MIN };
+
+describe('computeWorkTime', () => {
+  it('§7 fixture — sessionizes 20-ish samples to ≈1h32m, not the ≈60h naive span', () => {
+    const rows: TimelineSample[] = [
+      // S1: multi-sample morning session
+      s('2026-07-04T03:40:00'),
+      s('2026-07-04T03:45:00'),
+      s('2026-07-04T03:49:00'),
+      // S2: agent burst (one run) then human supervising → class work
+      s('2026-07-04T15:43:00', { source: 'agent', chat: 'c1', kind: 'agent' }),
+      s('2026-07-04T15:47:00', { source: 'agent', chat: 'c1', kind: 'agent' }),
+      s('2026-07-04T15:50:00', { source: 'agent', chat: 'c1', kind: 'agent' }),
+      s('2026-07-04T16:13:00'),
+      // S3: single
+      s('2026-07-04T18:11:00'),
+      // S4: multi-sample evening session
+      s('2026-07-04T19:38:00'),
+      s('2026-07-04T19:44:00'),
+      s('2026-07-04T19:54:00'),
+      // S5 / S6: two singles two days later, 44m apart → two sessions at T_gap=30
+      s('2026-07-06T15:34:00'),
+      s('2026-07-06T16:18:00'),
+    ];
+
+    const r = computeWorkTime(rows, S7);
+
+    // 19 + 40 + 2 + 26 + 2 + 2 = 91 minutes.
+    expect(r.workMs).toBe(91 * MIN);
+    expect(r.agentOnlyMs).toBe(0);
+    expect(r.sessions).toHaveLength(6);
+    expect(r.sessions.every((x) => x.class === 'work')).toBe(true);
+
+    const naiveSpan =
+      new Date('2026-07-06T16:18:00Z').getTime() -
+      new Date('2026-07-04T03:40:00Z').getTime();
+    expect(naiveSpan).toBeGreaterThan(60 * 60 * MIN); // ≈60h
+    expect(r.workMs).toBeLessThan(naiveSpan / 30); // dramatically smaller
+  });
+
+  it('n=0 → zero, no sessions', () => {
+    const r = computeWorkTime([]);
+    expect(r).toEqual({ workMs: 0, agentOnlyMs: 0, sessions: [] });
+  });
+
+  it('n=1 human → one P_single work session', () => {
+    const r = computeWorkTime([s('2026-07-04T10:00:00')], S7);
+    expect(r.sessions).toHaveLength(1);
+    expect(r.sessions[0].class).toBe('work');
+    expect(r.workMs).toBe(2 * MIN);
+    expect(r.agentOnlyMs).toBe(0);
+    // pre-roll only: [t − P_single, t]
+    expect(r.sessions[0].end).toBe(new Date('2026-07-04T10:00:00Z').getTime());
+  });
+
+  it('n=1 agent → one P_single agent_only session, work=0 (§9#2)', () => {
+    const r = computeWorkTime(
+      [s('2026-07-04T10:00:00', { source: 'agent', chat: 'c1', kind: 'agent' })],
+      S7,
+    );
+    expect(r.sessions).toHaveLength(1);
+    expect(r.sessions[0].class).toBe('agent_only');
+    expect(r.workMs).toBe(0);
+    expect(r.agentOnlyMs).toBe(2 * MIN);
+  });
+
+  it('MUST close the last session — the newest session is not lost (§9#1)', () => {
+    // Two singles a day apart: without the post-loop close, the 2nd is dropped.
+    const rows = [s('2026-07-04T10:00:00'), s('2026-07-05T10:00:00')];
+    const r = computeWorkTime(rows, S7);
+    expect(r.sessions).toHaveLength(2);
+    const lastStart = Math.max(...r.sessions.map((x) => x.start));
+    expect(lastStart).toBe(
+      new Date('2026-07-05T10:00:00Z').getTime() - 2 * MIN,
+    );
+    expect(r.workMs).toBe(4 * MIN);
+  });
+
+  it('agent-burst collapse: density does not inflate — length = wall-clock', () => {
+    const span = ['00', '01', '02', '03', '04', '05', '06'];
+    const dense: TimelineSample[] = span.map((sec) =>
+      s(`2026-07-04T10:00:${sec}`, { source: 'agent', chat: 'c1', kind: 'agent' }),
+    );
+    const sparse: TimelineSample[] = [
+      s('2026-07-04T10:00:00', { source: 'agent', chat: 'c1', kind: 'agent' }),
+      s('2026-07-04T10:00:06', { source: 'agent', chat: 'c1', kind: 'agent' }),
+    ];
+    const rDense = computeWorkTime(dense, S7);
+    const rSparse = computeWorkTime(sparse, S7);
+    // Same 6-second wall-clock span → same estimate regardless of snapshot count.
+    expect(rDense.agentOnlyMs).toBe(rSparse.agentOnlyMs);
+    expect(rDense.sessions).toHaveLength(1);
+    expect(rDense.sessions[0].class).toBe('agent_only');
+  });
+
+  it('supervisory agent time inside a human session counts as work, not agent', () => {
+    const rows = [
+      s('2026-07-04T10:00:00', { source: 'agent', chat: 'c1', kind: 'agent' }),
+      s('2026-07-04T10:05:00', { source: 'agent', chat: 'c1', kind: 'agent' }),
+      s('2026-07-04T10:12:00'), // human within T_gap
+    ];
+    const r = computeWorkTime(rows, S7);
+    expect(r.sessions).toHaveLength(1);
+    expect(r.sessions[0].class).toBe('work');
+    expect(r.agentOnlyMs).toBe(0);
+    expect(r.workMs).toBeGreaterThan(0);
+  });
+
+  it('a DIFFERENT aiChatId breaks the burst — two agent runs, idle gap excluded', () => {
+    // Run c1 ends 10:05, run c2 starts 10:20 (15m > agentTGap 7m) → two sessions.
+    const rows = [
+      s('2026-07-04T10:00:00', { source: 'agent', chat: 'c1', kind: 'agent' }),
+      s('2026-07-04T10:05:00', { source: 'agent', chat: 'c1', kind: 'agent' }),
+      s('2026-07-04T10:20:00', { source: 'agent', chat: 'c2', kind: 'agent' }),
+      s('2026-07-04T10:25:00', { source: 'agent', chat: 'c2', kind: 'agent' }),
+    ];
+    const r = computeWorkTime(rows); // default agentTGap = 7m
+    expect(r.sessions).toHaveLength(2);
+    expect(r.sessions.every((x) => x.class === 'agent_only')).toBe(true);
+    // The 15m idle gap between the two runs is NOT counted.
+    const run1 = 5 * MIN + 5 * MIN + 5 * MIN; // pIn + span + pOut
+    expect(r.agentOnlyMs).toBe(2 * run1);
+  });
+
+  it('idle pulse (same/null run) is a full activity sample that continues a burst', () => {
+    const rows = [
+      s('2026-07-04T10:00:00', { source: 'agent', chat: 'c1', kind: 'agent' }),
+      // idle flush 4m later, null run id → continues the burst, not a new one
+      s('2026-07-04T10:04:00', { source: 'agent', chat: null, kind: 'idle' }),
+      s('2026-07-04T10:08:00', { source: 'agent', chat: 'c1', kind: 'agent' }),
+    ];
+    const r = computeWorkTime(rows);
+    expect(r.sessions).toHaveLength(1);
+    // burst span 10:00→10:08 (+pIn/pOut) = 8 + 10 = 18m
+    expect(r.agentOnlyMs).toBe(18 * MIN);
+  });
+
+  it('a USER-sourced idle breaks an agent burst → session is work, not agent_only', () => {
+    // A human supervision idle inherits source=user (aiChatId:null) and must NOT
+    // be swallowed into the agent burst. Δ=3m is within the default agentTGap so
+    // the two samples stay one session — but its class flips to `work`.
+    const rows = [
+      s('2026-07-04T10:00:00', { source: 'agent', chat: 'c1', kind: 'agent' }),
+      s('2026-07-04T10:03:00', { source: 'user', chat: null, kind: 'idle' }),
+    ];
+    const r = computeWorkTime(rows);
+    expect(r.sessions).toHaveLength(1);
+    expect(r.sessions[0].class).toBe('work');
+    expect(r.workMs).toBeGreaterThan(0);
+    // The human idle is NOT captured as agent_only time.
+    expect(r.agentOnlyMs).toBe(0);
+    // Σ over `work` sessions == workMs and Σ over `agent_only` == agentOnlyMs.
+    const sum = (cls: string) =>
+      r.sessions
+        .filter((x) => x.class === cls)
+        .reduce((acc, x) => acc + (x.end - x.start), 0);
+    expect(sum('work')).toBe(r.workMs);
+    expect(sum('agent_only')).toBe(r.agentOnlyMs);
+  });
+
+  it('idle pulse keeps a human writing session visible (not excluded)', () => {
+    const rows = [
+      s('2026-07-04T10:00:00'),
+      s('2026-07-04T10:08:00', { kind: 'idle' }), // pulse within T_gap
+      s('2026-07-04T10:15:00'),
+    ];
+    const r = computeWorkTime(rows);
+    expect(r.sessions).toHaveLength(1);
+    expect(r.sessions[0].class).toBe('work');
+    // span 10:00→10:15 + pIn/pOut = 15 + 10 = 25m
+    expect(r.workMs).toBe(25 * MIN);
+  });
+
+  it('git-source samples are excluded (§10 excludeGit)', () => {
+    const rows = [
+      s('2026-07-04T10:00:00', { source: 'git', kind: 'boundary' }),
+      s('2026-07-04T10:01:00', { source: 'git', kind: 'boundary' }),
+    ];
+    expect(computeWorkTime(rows).workMs).toBe(0);
+    // ...but honoured off:
+    expect(
+      computeWorkTime(rows, { excludeGit: false }).workMs,
+    ).toBeGreaterThan(0);
+  });
+
+  it('rejects an invalid config (tGap < pIn + pOut)', () => {
+    expect(() =>
+      computeWorkTime([s('2026-07-04T10:00:00')], {
+        tGap: 5 * MIN,
+        pIn: 5 * MIN,
+        pOut: 5 * MIN,
+      }),
+    ).toThrow(/tGap/);
+  });
+
+  it('rejects an invalid config (2·agentTGap < pIn + pOut)', () => {
+    // tGap (default 15m) still ≥ pIn+pOut, so only the 2·agentTGap guard trips.
+    // Without it a short session of one class between two of the other could
+    // produce a NON-adjacent cross-class overlap the adjacent-only clip misses.
+    expect(() =>
+      computeWorkTime([s('2026-07-04T10:00:00')], {
+        agentTGap: 2 * MIN,
+        pIn: 5 * MIN,
+        pOut: 5 * MIN,
+      }),
+    ).toThrow(/agentTGap/);
+  });
+
+  // F1 — cross-class double-count. On the DEFAULT config agentTGap (7m) < pIn+pOut
+  // (10m), so a `work` session ending in an agent segment and a nearby separate
+  // `agent_only` run (gap in (7m,10m]) used to produce OVERLAPPING padded
+  // intervals — the same wall-clock counted into BOTH workMs and agentOnlyMs. The
+  // cross-class padding clip must make the two per-class unions disjoint.
+  it('does NOT double-count wall-clock across work/agent_only (§F1)', () => {
+    // user@0s ; agent(chatX)@60s (breaks into a work session with the human) ;
+    // agent(chatY)@560s,590s (a separate agent_only run). Raw gap between the work
+    // session (ends 60s) and the agent run (starts 560s) is 500s ∈ (agentTGap,
+    // pIn+pOut] once padded — the classic overlap window.
+    const rows: TimelineSample[] = [
+      s('2026-07-04T00:00:00'), // user @ 0s
+      s('2026-07-04T00:01:00', { source: 'agent', chat: 'cX', kind: 'agent' }), // @ 60s
+      s('2026-07-04T00:09:20', { source: 'agent', chat: 'cY', kind: 'agent' }), // @ 560s
+      s('2026-07-04T00:09:50', { source: 'agent', chat: 'cY', kind: 'agent' }), // @ 590s
+    ];
+    const r = computeWorkTime(rows); // DEFAULT config
+
+    // Both classes present.
+    expect(r.workMs).toBeGreaterThan(0);
+    expect(r.agentOnlyMs).toBeGreaterThan(0);
+
+    // Per-class metrics are exactly their own union (union, not Σ).
+    expect(r.workMs).toBe(unionMs(ivsOf(r.sessions, 'work')));
+    expect(r.agentOnlyMs).toBe(unionMs(ivsOf(r.sessions, 'agent_only')));
+
+    // The F1 invariant: work-union and agent-union are cross-class-disjoint, so
+    // the union of ALL padded intervals equals workMs + agentOnlyMs (no overlap).
+    // With the clip disabled this fails (union < sum by the 100s overlap).
+    expect(unionMs(ivsOf(r.sessions))).toBe(r.workMs + r.agentOnlyMs);
+  });
+
+  // F1 property/fuzz — random timelines across several timezones must uphold the
+  // work-time invariants. Backs the (corrected) PR claim of a real fuzz test.
+  it('property: random timelines uphold union & cross-class-disjoint invariants', () => {
+    // Deterministic LCG (numerical-recipes constants) so a failure is reproducible.
+    let seed = 0x9e3779b9 >>> 0;
+    const rand = () => {
+      seed = (Math.imul(seed, 1664525) + 1013904223) >>> 0;
+      return seed / 0x100000000;
+    };
+    const pick = <T>(arr: T[]): T => arr[Math.floor(rand() * arr.length)];
+
+    const tzs = [
+      'UTC',
+      'America/New_York',
+      'Europe/Moscow',
+      'Australia/Lord_Howe', // 30-min DST offset — a nasty bucket stress
+    ];
+    const base = Date.UTC(2026, 5, 1, 0, 0, 0); // 2026-06-01Z
+    const chats = ['c1', 'c2', 'c3'];
+
+    for (let iter = 0; iter < 250; iter++) {
+      const tz = pick(tzs);
+      const n = 2 + Math.floor(rand() * 18); // 2..19 rows
+      const rows: TimelineSample[] = [];
+      // Walk time forward by a random inter-sample gap. The gap distribution is
+      // centred on the DANGEROUS band — a bit under to a bit over pIn+pOut (10m)
+      // AND straddling agentTGap (7m) — so adjacent samples routinely split into
+      // separate sessions whose ±P padding would overlap if a class boundary sits
+      // there. Mixing user/agent classes at these gaps reliably manufactures the
+      // work-ending-in-agent → agent_only cross-class boundary F1 is about, plus
+      // dense within-class runs (occasional 0–2m gaps) that exercise the union.
+      let t = base + Math.floor(rand() * 60 * MIN);
+      for (let i = 0; i < n; i++) {
+        const roll = rand();
+        const gap =
+          roll < 0.25
+            ? Math.floor(rand() * 2 * MIN) // dense burst (same-class union)
+            : roll < 0.85
+              ? 5 * MIN + Math.floor(rand() * 8 * MIN) // 5–13m: the split band
+              : 20 * MIN + Math.floor(rand() * 40 * MIN); // long idle → new day-ish
+        t += gap;
+        const iso = new Date(t).toISOString().slice(0, 19); // 'YYYY-MM-DDTHH:MM:SS'
+        const isAgent = rand() < 0.5;
+        rows.push(
+          isAgent
+            ? s(iso, { source: 'agent', chat: pick(chats), kind: 'agent' })
+            : s(iso, { source: 'user', kind: rand() < 0.3 ? 'idle' : 'manual' }),
+        );
+      }
+
+      const r = computeWorkTime(rows); // DEFAULT config
+
+      const workIvs = ivsOf(r.sessions, 'work');
+      const agentIvs = ivsOf(r.sessions, 'agent_only');
+
+      // (1) each metric is exactly its per-class union (catches a union→Σ regress).
+      expect(r.workMs).toBe(unionMs(workIvs));
+      expect(r.agentOnlyMs).toBe(unionMs(agentIvs));
+
+      // (2) NO cross-class overlap: union(all) == workMs + agentOnlyMs (F1).
+      expect(unionMs(ivsOf(r.sessions))).toBe(r.workMs + r.agentOnlyMs);
+
+      // (3) bucket invariant: Σ per-day activeMs == workMs (§6.3).
+      const perDay = bucketByDay(r.sessions, tz);
+      const sumActive = perDay.reduce((a, d) => a + d.activeMs, 0);
+      expect(sumActive).toBe(r.workMs);
+    }
+  });
+});

apps/server/src/core/page/work-time/compute-work-time.ts

@@ -0,0 +1,274 @@
+import {
+  TimelineSample,
+  WorkSession,
+  WorkTimeResult,
+} from './work-time.types';
+import { WorkTimeConfig, resolveWorkTimeConfig } from './work-time.config';
+
+/** A normalized activity sample (one history row), createdAt as epoch-ms. */
+interface NormSample {
+  t: number;
+  isAgent: boolean;
+  aiChatId: string | null;
+  kind: string | null;
+}
+
+/**
+ * A collapsed segment: either a scalar sample (t_start == t_end) or an
+ * agent-burst spanning several agent samples of one run (§5.1). It participates
+ * in sessionization as a single "sample".
+ */
+interface Segment {
+  tStart: number;
+  tEnd: number;
+  isAgent: boolean;
+}
+
+function toMs(v: Date | string | number): number {
+  if (v instanceof Date) return v.getTime();
+  if (typeof v === 'number') return v;
+  return new Date(v).getTime();
+}
+
+/**
+ * Normalize raw rows → sorted, deduped activity samples. `git` is dropped when
+ * configured; every other kind (incl. `idle` — the continuous-work pulse §3) is
+ * a real activity sample. Sort is by createdAt ASC; samples whose timestamps
+ * fall in the same `dedupRoundMs` bucket collapse to one (§9#7: a synchronous
+ * boundary row + the immediate agent snapshot can share a createdAt). A merged
+ * sample is human unless EVERY member is an agent, so supervision never gets
+ * mis-attributed to the agent.
+ */
+function normalize(
+  rows: TimelineSample[],
+  config: WorkTimeConfig,
+): NormSample[] {
+  const samples: NormSample[] = [];
+  for (const row of rows) {
+    const source = row.lastUpdatedSource;
+    if (config.excludeGit && source === 'git') continue;
+    samples.push({
+      t: toMs(row.createdAt),
+      isAgent: source === 'agent',
+      aiChatId: row.lastUpdatedAiChatId ?? null,
+      kind: row.kind ?? null,
+    });
+  }
+  samples.sort((a, b) => a.t - b.t);
+
+  if (config.dedupRoundMs <= 0 || samples.length < 2) return samples;
+
+  const deduped: NormSample[] = [];
+  for (const s of samples) {
+    const prev = deduped[deduped.length - 1];
+    if (prev && s.t - prev.t < config.dedupRoundMs) {
+      // Merge into the previous sample. Human wins the class; keep the earliest
+      // t; keep a non-null aiChatId if either has one (so a bare boundary row
+      // does not erase the run id).
+      prev.isAgent = prev.isAgent && s.isAgent;
+      prev.aiChatId = prev.aiChatId ?? s.aiChatId;
+      // Prefer the more specific kind (a real kind over a null/boundary) only
+      // matters for burst continuation; keep prev.kind (earliest) as-is.
+      continue;
+    }
+    deduped.push({ ...s });
+  }
+  return deduped;
+}
+
+/**
+ * Collapse consecutive same-run agent samples into one burst segment (§5.1) so a
+ * dense burst (8 snapshots in 7 minutes) contributes its wall-clock, not a count
+ * × block. A burst is broken by any sample NOT continuing the same aiChatId
+ * agent run: a non-agent sample, a `boundary` (actor transition), or a DIFFERENT
+ * aiChatId. Only an AGENT-sourced `idle` pulse with the SAME or a null aiChatId
+ * continues the burst (its label lags the real edit ≤ maxWait, well within
+ * rounding); a user-sourced `idle` (a human supervision pulse) breaks it.
+ */
+function collapse(samples: NormSample[], config: WorkTimeConfig): Segment[] {
+  const segments: Segment[] = [];
+  let burst: { chatId: string | null; tStart: number; tEnd: number } | null =
+    null;
+
+  const flush = () => {
+    if (!burst) return;
+    let tEnd = burst.tEnd;
+    if (config.burstCapMs != null && tEnd - burst.tStart > config.burstCapMs) {
+      tEnd = burst.tStart + config.burstCapMs;
+    }
+    segments.push({ tStart: burst.tStart, tEnd, isAgent: true });
+    burst = null;
+  };
+
+  for (const s of samples) {
+    // An agent-sourced idle pulse continues the current agent burst (same or
+    // null run id). A user-sourced idle (human supervision) must NOT be swallowed
+    // here — it falls through to the human branch so the session flips to `work`.
+    if (
+      burst &&
+      s.kind === 'idle' &&
+      s.isAgent &&
+      (s.aiChatId === burst.chatId || s.aiChatId == null)
+    ) {
+      burst.tEnd = s.t;
+      continue;
+    }
+    if (s.isAgent && s.kind !== 'boundary') {
+      if (burst && burst.chatId === s.aiChatId) {
+        burst.tEnd = s.t;
+      } else {
+        flush();
+        burst = { chatId: s.aiChatId, tStart: s.t, tEnd: s.t };
+      }
+      continue;
+    }
+    // A human sample, a boundary, or an agent-boundary: breaks the burst and is
+    // itself a zero-width segment (its class follows its own source).
+    flush();
+    segments.push({ tStart: s.t, tEnd: s.t, isAgent: s.isAgent });
+  }
+  flush();
+  return segments;
+}
+
+function gapThreshold(
+  a: Segment,
+  b: Segment,
+  config: WorkTimeConfig,
+): number {
+  return a.isAgent && b.isAgent ? config.agentTGap : config.tGap;
+}
+
+/** Merge intervals; overlapping OR touching intervals are unioned. */
+function unionDuration(intervals: Array<[number, number]>): number {
+  if (intervals.length === 0) return 0;
+  const sorted = [...intervals].sort((a, b) => a[0] - b[0]);
+  let total = 0;
+  let [curStart, curEnd] = sorted[0];
+  for (let i = 1; i < sorted.length; i++) {
+    const [s, e] = sorted[i];
+    if (s <= curEnd) {
+      if (e > curEnd) curEnd = e;
+    } else {
+      total += curEnd - curStart;
+      curStart = s;
+      curEnd = e;
+    }
+  }
+  total += curEnd - curStart;
+  return total;
+}
+
+/**
+ * #395 core — estimate time worked on a page from its history timeline (§5).
+ * Pure and deterministic: no DB, no clock, no I/O.
+ *
+ * Pipeline: normalize+dedup → collapse agent bursts → ONE sessionization pass
+ * over all segments (threshold depends on the pair: both-agent → agentTGap, else
+ * tGap; the last session is ALWAYS closed after the loop) → class per finished
+ * session (all-agent → agent_only, else work) → pad each session (multi-sample
+ * → [first−P_in, last+P_out]; lone scalar → [t−P_single, t]) → clip padding of
+ * adjacent DIFFERENT-class sessions at the raw-gap midpoint (so work/agent_only
+ * never overlap) → metrics are the union wall-clock within each class (union, not
+ * Σ, so overlaps never double, and cross-class-disjoint by the clip above).
+ */
+export function computeWorkTime(
+  rows: TimelineSample[],
+  config?: Partial<WorkTimeConfig>,
+): WorkTimeResult {
+  const cfg = resolveWorkTimeConfig(config);
+  const samples = normalize(rows, cfg);
+  const segments = collapse(samples, cfg);
+
+  // Sessionize — one pass over ALL segments.
+  const rawSessions: Segment[][] = [];
+  let cur: Segment[] | null = null;
+  for (const seg of segments) {
+    if (cur == null) {
+      cur = [seg];
+    } else {
+      const last = cur[cur.length - 1];
+      if (seg.tStart - last.tEnd <= gapThreshold(last, seg, cfg)) {
+        cur.push(seg);
+      } else {
+        rawSessions.push(cur);
+        cur = [seg];
+      }
+    }
+  }
+  if (cur != null) rawSessions.push(cur); // MUST close the last session (§5, §9#1)
+
+  // A finished session with BOTH its raw (unpadded) span and its padded bounds.
+  // `rawSessions` are already in ascending time order, so `built` is too.
+  interface BuiltSession {
+    rawStart: number;
+    rawEnd: number;
+    padStart: number;
+    padEnd: number;
+    cls: WorkSession['class'];
+  }
+  const built: BuiltSession[] = [];
+
+  for (const segs of rawSessions) {
+    const first = segs[0];
+    const last = segs[segs.length - 1];
+    const cls = segs.every((s) => s.isAgent) ? 'agent_only' : 'work';
+
+    let padStart: number;
+    let padEnd: number;
+    if (segs.length === 1 && first.tStart === first.tEnd) {
+      // Lone single-instant session (one scalar, or a one-snapshot agent run):
+      // pre-roll only, no invented "future" work (§5).
+      padStart = first.tStart - cfg.pSingle;
+      padEnd = first.tStart;
+    } else {
+      padStart = first.tStart - cfg.pIn;
+      padEnd = last.tEnd + cfg.pOut;
+    }
+
+    built.push({
+      rawStart: first.tStart,
+      rawEnd: last.tEnd,
+      padStart,
+      padEnd,
+      cls,
+    });
+  }
+
+  // Clip cross-class padding so a `work` and an `agent_only` session that abut
+  // never claim the same wall-clock. For each ADJACENT pair of DIFFERENT classes,
+  // cap the earlier session's trailing pad and the later session's leading pad at
+  // the MIDPOINT of the raw (unpadded) inactivity gap between them: the earlier
+  // padded interval then ends ≤ midpoint and the later one starts ≥ midpoint, so
+  // the two are disjoint (they touch at most at the midpoint). This makes the
+  // per-class unions (workMs / agentOnlyMs) cross-class-disjoint BY CONSTRUCTION
+  // — closing the double-count where a work session ending in an agent segment
+  // and a nearby agent_only session (gap in (agentTGap, pIn+pOut]) overlapped and
+  // were counted into both metrics (§5, §9). Within-class adjacency is left
+  // untouched: `unionDuration` already dedups it, and clipping there could perturb
+  // the per-class metric value.
+  for (let i = 1; i < built.length; i++) {
+    const a = built[i - 1];
+    const b = built[i];
+    if (a.cls === b.cls) continue;
+    const midpoint = (a.rawEnd + b.rawStart) / 2;
+    if (a.padEnd > midpoint) a.padEnd = midpoint;
+    if (b.padStart < midpoint) b.padStart = midpoint;
+  }
+
+  const sessions: WorkSession[] = [];
+  const workIvs: Array<[number, number]> = [];
+  const agentIvs: Array<[number, number]> = [];
+  for (const s of built) {
+    sessions.push({ start: s.padStart, end: s.padEnd, class: s.cls });
+    (s.cls === 'work' ? workIvs : agentIvs).push([s.padStart, s.padEnd]);
+  }
+
+  sessions.sort((a, b) => a.start - b.start);
+
+  return {
+    workMs: unionDuration(workIvs),
+    agentOnlyMs: unionDuration(agentIvs),
+    sessions,
+  };
+}

apps/server/src/core/page/work-time/index.ts

@@ -0,0 +1,15 @@
+export { computeWorkTime } from './compute-work-time';
+export { bucketByDay, zonedDayStart } from './bucket-by-day';
+export {
+  DEFAULT_WORK_TIME_CONFIG,
+  resolveWorkTimeConfig,
+} from './work-time.config';
+export type { WorkTimeConfig } from './work-time.config';
+export type {
+  TimelineSample,
+  WorkSession,
+  WorkTimeResult,
+  SessionClass,
+  DayWindow,
+  PerDay,
+} from './work-time.types';

apps/server/src/core/page/work-time/work-time.config.ts

@@ -0,0 +1,102 @@
+import {
+  IDLE_MAX_WAIT_USER,
+  IDLE_MAX_WAIT_AGENT,
+} from '../../../collaboration/constants';
+
+/**
+ * #395 — tunables for the work-time estimate (§10). Defaults are calibrated off
+ * #374's idle-pulse ceilings: after #374 a continuous editing session leaves a
+ * history row at least every ~IDLE_MAX_WAIT (10m user / 5m agent), so a gap
+ * WIDER than that ceiling contains un-pulsed idle time = (partial) inactivity.
+ * `tGap` therefore sits a little above the user ceiling, `agentTGap` a little
+ * above the agent ceiling — a gap within the threshold is pulse-backed and
+ * counts as work.
+ */
+export interface WorkTimeConfig {
+  /** user inactivity timeout: gap ≤ tGap between samples = continuous work. */
+  tGap: number;
+  /** timeout for a pair of consecutive agent samples (tighter than tGap). */
+  agentTGap: number;
+  /** pre-roll padding for a multi-sample session (work began before sample 1). */
+  pIn: number;
+  /** post-roll padding for a multi-sample session (work continued after last). */
+  pOut: number;
+  /** block for a lone single-sample session (pre-roll only, no invented future). */
+  pSingle: number;
+  /** drop `git`-source samples (they are not human/agent article work). */
+  excludeGit: boolean;
+  /** optional cap on one collapsed agent-burst segment's wall-clock (§9#3). */
+  burstCapMs?: number;
+  /** samples whose createdAt round to the same bucket dedup to one (§9#7). */
+  dedupRoundMs: number;
+}
+
+export const DEFAULT_WORK_TIME_CONFIG: WorkTimeConfig = {
+  // ~15m: IDLE_MAX_WAIT_USER (10m) + headroom. Empirically backcast on a real
+  // 307-snapshot article (≈24h at 15m matched the owner's estimate; 30/45m
+  // over-counted). See #395 §10.
+  tGap: 15 * 60 * 1000,
+  // ~7m: IDLE_MAX_WAIT_AGENT (5m) + headroom.
+  agentTGap: 7 * 60 * 1000,
+  pIn: 5 * 60 * 1000,
+  pOut: 5 * 60 * 1000,
+  pSingle: 2 * 60 * 1000,
+  excludeGit: true,
+  burstCapMs: undefined,
+  dedupRoundMs: 1000,
+};
+
+// Compile-time cross-check that the defaults really are pulse-anchored — if a
+// future edit moves the #374 ceilings, this reminds us to re-calibrate.
+void IDLE_MAX_WAIT_USER;
+void IDLE_MAX_WAIT_AGENT;
+
+/**
+ * Fill a partial config with defaults and validate it. Cross-class metric
+ * disjointness is guaranteed jointly by `computeWorkTime`'s adjacent-pair padding
+ * clip (it caps the padding of adjacent DIFFERENT-class sessions at the raw-gap
+ * midpoint) AND the two bounds enforced below (§5):
+ *   - `tGap ≥ pIn + pOut`: a session's own padding never exceeds its inactivity
+ *     window.
+ *   - `2·agentTGap ≥ pIn + pOut`: makes the adjacent-only clip provably COMPLETE.
+ *     A NON-adjacent (i, i+2) cross-class overlap could only arise from two
+ *     same-class sessions separated by a full intervening session of the other
+ *     class; that separation spans at least two inter-session gaps, each strictly
+ *     `> agentTGap`, so it is `> 2·agentTGap`. Requiring `2·agentTGap ≥ pIn + pOut`
+ *     means even the widest padded reach (pIn + pOut) cannot bridge it — so the
+ *     only cross-class overlaps possible are between ADJACENT sessions, which the
+ *     clip handles. `workMs`/`agentOnlyMs` are therefore disjoint by construction.
+ */
+export function resolveWorkTimeConfig(
+  partial?: Partial<WorkTimeConfig>,
+): WorkTimeConfig {
+  const config = { ...DEFAULT_WORK_TIME_CONFIG, ...(partial ?? {}) };
+
+  for (const key of [
+    'tGap',
+    'agentTGap',
+    'pIn',
+    'pOut',
+    'pSingle',
+    'dedupRoundMs',
+  ] as const) {
+    const value = config[key];
+    if (!Number.isFinite(value) || value < 0) {
+      throw new Error(`work-time config: ${key} must be a non-negative number`);
+    }
+  }
+  if (config.burstCapMs != null && config.burstCapMs <= 0) {
+    throw new Error('work-time config: burstCapMs must be > 0 when set');
+  }
+  if (config.tGap < config.pIn + config.pOut) {
+    throw new Error(
+      "work-time config: tGap must be ≥ pIn + pOut (a session's padding may not exceed its inactivity window)",
+    );
+  }
+  if (2 * config.agentTGap < config.pIn + config.pOut) {
+    throw new Error(
+      'work-time config: 2·agentTGap must be ≥ pIn + pOut (so non-adjacent cross-class padding cannot overlap)',
+    );
+  }
+  return config;
+}

apps/server/src/core/page/work-time/work-time.types.ts

@@ -0,0 +1,73 @@
+/**
+ * #395 — "time worked on an article" domain types.
+ *
+ * The estimate is built by sessionizing a page's `page_history` timeline on
+ * inactivity gaps (WakaTime-style), NOT by taking the span between the first and
+ * last edit (which over-counts sleep / lunch / idle days). See the design doc in
+ * issue #395 §5–§6.3 for the normative algorithm.
+ */
+
+/**
+ * A single `page_history` row projected for the work-time computation — the
+ * cheap columns only (no `content`). Produced by
+ * `PageHistoryRepo.findTimelineByPageId`. `createdAt` is whatever the DB driver
+ * hands back (Date); the pure core normalizes it to epoch-ms itself so it stays
+ * deterministic and DB-free.
+ */
+export interface TimelineSample {
+  createdAt: Date | string | number;
+  lastUpdatedById: string | null;
+  /** 'user' | 'agent' | 'git' | null (legacy autosave = human). */
+  lastUpdatedSource: string | null;
+  lastUpdatedAiChatId: string | null;
+  /** #370 tier: 'manual' | 'agent' | 'idle' | 'boundary' | null (legacy). */
+  kind: string | null;
+}
+
+/** A finished session's class (§5.1). */
+export type SessionClass = 'work' | 'agent_only';
+
+/**
+ * A finished session: absolute wall-clock bounds already padded with P_in/P_out
+ * (multi-sample) or P_single (single scalar), plus its class. This is enough for
+ * both the metrics and the per-day punch-card colouring.
+ */
+export interface WorkSession {
+  /** epoch-ms, inclusive lower bound (already P-padded). */
+  start: number;
+  /** epoch-ms, exclusive upper bound (already P-padded). */
+  end: number;
+  class: SessionClass;
+}
+
+/** Output of {@link computeWorkTime}. */
+export interface WorkTimeResult {
+  /** union wall-clock of `work` sessions, ms (the headline metric). */
+  workMs: number;
+  /** union wall-clock of `agent_only` sessions, ms (secondary). */
+  agentOnlyMs: number;
+  sessions: WorkSession[];
+}
+
+/** One activity window inside a calendar day (already clipped to the day). */
+export interface DayWindow {
+  /** epoch-ms. */
+  start: number;
+  /** epoch-ms. */
+  end: number;
+  class: SessionClass;
+}
+
+/** One calendar day of the punch-card (§6.3). */
+export interface PerDay {
+  /** epoch-ms of the local-midnight day start in the requested tz. */
+  day: number;
+  /** 'YYYY-MM-DD' in the requested tz — stable, tz-independent label. */
+  dayISO: string;
+  /** Σ of `work` windows this day, ms. Σ over days == workMs (invariant §6.3). */
+  activeMs: number;
+  /** Σ of `agent_only` windows this day, ms (drawn, NOT in activeMs). */
+  agentMs: number;
+  /** both classes, clipped to the day, sorted by start (for drawing). */
+  windows: DayWindow[];
+}

apps/server/src/database/repos/page/page-history.repo.ts

@@ -157,6 +157,44 @@ export class PageHistoryRepo {
     return { ...result, items: result.items.map(attachPageHistoryAgent) };
   }
 
+  /**
+   * #395 — cheap projection of a page's FULL history timeline for the work-time
+   * estimate: only the columns the sessionizer needs, no heavy `content`, sorted
+   * oldest→newest. The secondary `id` tie-break keeps rows sharing a `createdAt`
+   * (e.g. a synchronous pre-agent boundary row + the immediate agent snapshot)
+   * in a deterministic order.
+   */
+  async findTimelineByPageId(
+    pageId: string,
+    trx?: KyselyTransaction,
+  ): Promise<
+    Array<
+      Pick<
+        PageHistory,
+        | 'createdAt'
+        | 'lastUpdatedById'
+        | 'lastUpdatedSource'
+        | 'lastUpdatedAiChatId'
+        | 'kind'
+      >
+    >
+  > {
+    const db = dbOrTx(this.db, trx);
+    return db
+      .selectFrom('pageHistory')
+      .select([
+        'createdAt',
+        'lastUpdatedById',
+        'lastUpdatedSource',
+        'lastUpdatedAiChatId',
+        'kind',
+      ])
+      .where('pageId', '=', pageId)
+      .orderBy('createdAt', 'asc')
+      .orderBy('id', 'asc')
+      .execute();
+  }
+
   async findPageLastHistory(
     pageId: string,
     opts?: {

apps/server/test/integration/page-work-time.int-spec.ts

@@ -0,0 +1,137 @@
+import { randomUUID } from 'node:crypto';
+import { Kysely } from 'kysely';
+import { PageHistoryRepo } from '../../src/database/repos/page/page-history.repo';
+import { PageHistoryService } from '../../src/core/page/services/page-history.service';
+import { computeWorkTime } from '../../src/core/page/work-time';
+import {
+  getTestDb,
+  destroyTestDb,
+  createWorkspace,
+  createSpace,
+  createPage,
+  createUser,
+  createChat,
+} from './db';
+
+/**
+ * #395 — real-Postgres coverage for the work-time timeline projection and the
+ * service that computes the estimate. The pure sessionizer is unit-tested
+ * exhaustively (compute-work-time.spec.ts); this asserts the SQL projection
+ * (right rows, ASC, no `content`) and that the service's numbers agree with the
+ * pure core over the exact rows the DB returns.
+ */
+describe('PageHistory work-time [integration]', () => {
+  let db: Kysely<any>;
+  let repo: PageHistoryRepo;
+  let service: PageHistoryService;
+  let workspaceId: string;
+  let spaceId: string;
+  let pageId: string;
+  let userId: string;
+  let chatId: string;
+
+  const MIN = 60 * 1000;
+
+  beforeAll(async () => {
+    db = getTestDb();
+    repo = new PageHistoryRepo(db as any);
+    service = new PageHistoryService(repo);
+    workspaceId = (await createWorkspace(db)).id;
+    spaceId = (await createSpace(db, workspaceId)).id;
+    pageId = (await createPage(db, { workspaceId, spaceId })).id;
+    userId = (await createUser(db, workspaceId)).id;
+    chatId = (await createChat(db, { workspaceId, creatorId: userId })).id;
+  });
+
+  afterAll(async () => {
+    await destroyTestDb();
+  });
+
+  async function insertHistory(rows: Array<{
+    createdAt: string;
+    source: string | null;
+    chat?: string | null;
+    kind?: string | null;
+    content?: unknown;
+  }>) {
+    for (const r of rows) {
+      await db
+        .insertInto('pageHistory')
+        .values({
+          id: randomUUID(),
+          pageId,
+          spaceId,
+          workspaceId,
+          title: 'x',
+          content: r.content ?? { type: 'doc', content: [] },
+          lastUpdatedById: userId,
+          lastUpdatedSource: r.source,
+          lastUpdatedAiChatId: r.chat ?? null,
+          kind: r.kind ?? null,
+          createdAt: new Date(r.createdAt),
+        })
+        .execute();
+    }
+  }
+
+  it('findTimelineByPageId projects the cheap columns, ASC, without content', async () => {
+    await insertHistory([
+      { createdAt: '2026-07-04T19:54:00Z', source: 'user', kind: 'manual' },
+      { createdAt: '2026-07-04T03:40:00Z', source: 'user', kind: null },
+      { createdAt: '2026-07-04T15:43:00Z', source: 'agent', chat: chatId, kind: 'agent' },
+    ]);
+
+    const timeline = await repo.findTimelineByPageId(pageId);
+    expect(timeline).toHaveLength(3);
+    // Sorted oldest → newest.
+    const times = timeline.map((r) => new Date(r.createdAt).getTime());
+    expect(times).toEqual([...times].sort((a, b) => a - b));
+    // Projection carries exactly the sessionizer's inputs, and NO content.
+    for (const row of timeline) {
+      expect(row).toHaveProperty('createdAt');
+      expect(row).toHaveProperty('lastUpdatedById');
+      expect(row).toHaveProperty('lastUpdatedSource');
+      expect(row).toHaveProperty('lastUpdatedAiChatId');
+      expect(row).toHaveProperty('kind');
+      expect(row).not.toHaveProperty('content');
+    }
+    // Agent row keeps its provenance.
+    const agent = timeline.find((r) => r.lastUpdatedSource === 'agent');
+    expect(agent?.lastUpdatedAiChatId).toBe(chatId);
+  });
+
+  it('service estimate matches the pure core and satisfies Σ perDay == workMs', async () => {
+    const rows = await repo.findTimelineByPageId(pageId);
+    const pure = computeWorkTime(rows);
+
+    const result = await service.computeWorkTime(pageId, 'UTC');
+    expect(result.workMs).toBe(pure.workMs);
+    expect(result.agentOnlyMs).toBe(pure.agentOnlyMs);
+    expect(result.tz).toBe('UTC');
+    expect(result.config.tGap).toBe(15 * MIN);
+
+    const sumActive = result.perDay.reduce((a, d) => a + d.activeMs, 0);
+    expect(sumActive).toBe(result.workMs);
+
+    // The 3 seeded rows sessionize into ≤ their span; not the naive span.
+    const naive =
+      new Date('2026-07-04T19:54:00Z').getTime() -
+      new Date('2026-07-04T03:40:00Z').getTime();
+    expect(result.workMs).toBeGreaterThan(0);
+    expect(result.workMs).toBeLessThan(naive);
+  });
+
+  it('an unknown timezone surfaces as a RangeError (controller maps to 400)', async () => {
+    await expect(
+      service.computeWorkTime(pageId, 'Not/AZone'),
+    ).rejects.toBeInstanceOf(RangeError);
+  });
+
+  it('a page with no history → zeros, no days', async () => {
+    const emptyPage = (await createPage(db, { workspaceId, spaceId })).id;
+    const result = await service.computeWorkTime(emptyPage, 'UTC');
+    expect(result.workMs).toBe(0);
+    expect(result.agentOnlyMs).toBe(0);
+    expect(result.perDay).toEqual([]);
+  });
+});