diff --git a/apps/client/src/features/page-history/work-time/work-time-stat.tsx b/apps/client/src/features/page-history/work-time/work-time-stat.tsx
index d59eb5fc..b963456f 100644
--- a/apps/client/src/features/page-history/work-time/work-time-stat.tsx
+++ b/apps/client/src/features/page-history/work-time/work-time-stat.tsx
@@ -14,17 +14,23 @@ interface Props {
  * #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 estimate, so a brand-new /
- * never-edited page shows no widget.
+ * (§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) return null;
+  if (!data || (data.workMs <= 0 && data.agentOnlyMs <= 0)) return null;
 
-  const label = formatHeadline(data.workMs, t);
+  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 (
diff --git a/apps/client/src/features/page-history/work-time/work-time.types.ts b/apps/client/src/features/page-history/work-time/work-time.types.ts
index 761ebf9b..2ef5f114 100644
--- a/apps/client/src/features/page-history/work-time/work-time.types.ts
+++ b/apps/client/src/features/page-history/work-time/work-time.types.ts
@@ -3,12 +3,6 @@
 
 export type WorkSessionClass = "work" | "agent_only";
 
-export interface IWorkSession {
-  start: number;
-  end: number;
-  class: WorkSessionClass;
-}
-
 export interface IDayWindow {
   start: number;
   end: number;
@@ -37,7 +31,6 @@ export interface IWorkTimeConfig {
 export interface IPageWorkTime {
   workMs: number;
   agentOnlyMs: number;
-  sessions: IWorkSession[];
   perDay: IPerDay[];
   config: IWorkTimeConfig;
   tz: string;
diff --git a/apps/server/src/core/page/page.controller.spec.ts b/apps/server/src/core/page/page.controller.spec.ts
index e4640493..59d595ac 100644
--- a/apps/server/src/core/page/page.controller.spec.ts
+++ b/apps/server/src/core/page/page.controller.spec.ts
@@ -1,4 +1,8 @@
-import { BadRequestException, NotFoundException } from '@nestjs/common';
+import {
+  BadRequestException,
+  ForbiddenException,
+  NotFoundException,
+} from '@nestjs/common';
 import { PageController } from './page.controller';
 
 // Direct instantiation with stub deps. The Test.createTestingModule form failed
@@ -74,6 +78,23 @@ describe('PageController', () => {
       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 });
diff --git a/apps/server/src/core/page/services/page-history.service.ts b/apps/server/src/core/page/services/page-history.service.ts
index 518a62c3..66518987 100644
--- a/apps/server/src/core/page/services/page-history.service.ts
+++ b/apps/server/src/core/page/services/page-history.service.ts
@@ -9,13 +9,11 @@ import {
   DEFAULT_WORK_TIME_CONFIG,
   WorkTimeConfig,
   PerDay,
-  WorkSession,
 } from '../work-time';
 
 export interface PageWorkTime {
   workMs: number;
   agentOnlyMs: number;
-  sessions: WorkSession[];
   perDay: PerDay[];
   /** the config actually used, so the UI can show "≈" + the T_gap threshold. */
   config: WorkTimeConfig;
@@ -60,11 +58,12 @@ export class PageHistoryService {
     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,
-      sessions: result.sessions,
       perDay,
       config: usedConfig,
       tz,
diff --git a/apps/server/src/core/page/work-time/compute-work-time.spec.ts b/apps/server/src/core/page/work-time/compute-work-time.spec.ts
index da73808e..62f89176 100644
--- a/apps/server/src/core/page/work-time/compute-work-time.spec.ts
+++ b/apps/server/src/core/page/work-time/compute-work-time.spec.ts
@@ -1,8 +1,33 @@
 import { computeWorkTime } from './compute-work-time';
-import { TimelineSample } from './work-time.types';
+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: {
@@ -216,4 +241,118 @@ describe('computeWorkTime', () => {
       }),
     ).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);
+    }
+  });
 });
diff --git a/apps/server/src/core/page/work-time/compute-work-time.ts b/apps/server/src/core/page/work-time/compute-work-time.ts
index fa93c3c0..ccc19bd4 100644
--- a/apps/server/src/core/page/work-time/compute-work-time.ts
+++ b/apps/server/src/core/page/work-time/compute-work-time.ts
@@ -167,8 +167,10 @@ function unionDuration(intervals: Array<[number, number]>): number {
  * 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]) → metrics are the
- * union wall-clock within each class (union, not Σ, so overlaps never double).
+ * → [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[],
@@ -196,29 +198,70 @@ export function computeWorkTime(
   }
   if (cur != null) rawSessions.push(cur); // MUST close the last session (§5, §9#1)
 
-  const sessions: WorkSession[] = [];
-  const workIvs: Array<[number, number]> = [];
-  const agentIvs: Array<[number, number]> = [];
+  // 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 start: number;
-    let end: number;
+    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).
-      start = first.tStart - cfg.pSingle;
-      end = first.tStart;
+      padStart = first.tStart - cfg.pSingle;
+      padEnd = first.tStart;
     } else {
-      start = first.tStart - cfg.pIn;
-      end = last.tEnd + cfg.pOut;
+      padStart = first.tStart - cfg.pIn;
+      padEnd = last.tEnd + cfg.pOut;
     }
 
-    sessions.push({ start, end, class: cls });
-    (cls === 'work' ? workIvs : agentIvs).push([start, end]);
+    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);
diff --git a/apps/server/src/core/page/work-time/work-time.config.ts b/apps/server/src/core/page/work-time/work-time.config.ts
index 2e186255..497633a1 100644
--- a/apps/server/src/core/page/work-time/work-time.config.ts
+++ b/apps/server/src/core/page/work-time/work-time.config.ts
@@ -52,10 +52,20 @@ void IDLE_MAX_WAIT_USER;
 void IDLE_MAX_WAIT_AGENT;
 
 /**
- * Fill a partial config with defaults and validate it. `tGap ≥ pIn + pOut` is
- * NOT required for the §6.3 per-day invariant (union takes care of that), but is
- * RECOMMENDED and enforced: otherwise the P-padding of adjacent sessions of
- * DIFFERENT classes could overlap and be counted into both metrics (§5, §10).
+ * 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>,
@@ -80,7 +90,12 @@ export function resolveWorkTimeConfig(
   }
   if (config.tGap < config.pIn + config.pOut) {
     throw new Error(
-      'work-time config: tGap must be ≥ pIn + pOut so work/agent_only metrics cannot overlap',
+      "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;