@@ -63,9 +63,18 @@
  *                    (`LEDGER_EXCLUSION`).
  *   wall note        a line-initial `Wall:` (or `撞墙:`) line in the post
  *                    body, the seat's own record of a usage wall.
- *   last activity    the newest `updated_at` of the post and its in-flight
- *                    cards. A seated seat older than `STALE_HOURS` with no
- *                    wall note is flagged 「疑似撞墙」.
+ *   last activity    the newest of the seat's own traces: the post's
+ *                    `updated_at`, its in-flight cards', its mailbox pull's
+ *                    (the column below), and every comment of the last
+ *                    `STALE_HOURS` signed `LANE#N · ACCOUNT · SESSION` on its
+ *                    first line with THIS row's lane and seat — by seat, ⛔
+ *                    never by account, so a seat whose account also holds a
+ *                    lower seat of its lane (in flight `= seat N`) still reads
+ *                    its own work. A seated seat older than `STALE_HOURS` with
+ *                    no wall note is flagged 「疑似撞墙」. The comment read
+ *                    stops at `STALE_HOURS`, so a flagged row's age can read
+ *                    older than a signed comment past that window; the flag
+ *                    is exact.
  *   mailbox          open `pm:mailbox` pulls of the SEAT, whichever account
  *                    holds it: the seat on the body's first line
  *                    `Mailbox-of: <seat> · <login>`, or the head
@@ -283,6 +292,38 @@ export function epicSeatsHeld(lane, mailboxes) {
 }
 const isEpicLane = (lane) => lane.startsWith(`${SEAT_EPIC_KIND}:`);
 
+/**
+ * The seat signature line `LANE#N · ACCOUNT · SESSION`, MIRRORED from `check-half-states.mjs`'s `SEAT_SIGNATURE_LINE`
+ * (#27113) — not imported, so the relay never loads the patrol; the self-test holds the two patterns byte-equal.
+ */
+const SIGNATURE_LINE = new RegExp(
+  '^((?:domain:[a-z][a-z0-9-]*|repo:[a-z][a-z0-9-]*|epic:#[1-9][0-9]*|triage|director|coordinator))#([1-9][0-9]*) · ([A-Za-z0-9](?:[A-Za-z0-9]|-(?=[A-Za-z0-9])){0,38}) · (session_[A-Za-z0-9]{6,})$',
+  'u',
+);
+
+/** The seat a body is signed by — its FIRST non-empty line, `readSignatureLine`'s reading — as `LANE#N`, or null. Pure. */
+export function signedSeatOf(body) {
+  const line = String(body ?? '').split(/\r?\n/).find((l) => l.trim() !== '');
+  const m = line === undefined ? null : SIGNATURE_LINE.exec(line.trim());
+  return m ? `${m[1]}#${m[2]}` : null;
+}
+
+/** The newest signed-comment time per seat, `LANE#N` → ISO, over every repo's `recentComments`. Pure. */
+export function signedActivity(snapshot) {
+  const out = new Map();
+  for (const repo of Object.keys(snapshot?.repos ?? {})) {
+    for (const c of snapshot.repos[repo]?.recentComments ?? []) {
+      const seat = signedSeatOf(c?.body);
+      const at = c?.updated_at ?? c?.created_at ?? null;
+      if (seat !== null && at && !(out.get(seat) >= at)) out.set(seat, at);
+    }
+  }
+  return out;
+}
+
+/** Where the signed-comment read starts: `STALE_HOURS` before `now` — no older comment can lift a flag. Pure. */
+export const activitySince = (now) => new Date(Date.parse(now) - STALE_HOURS * 3_600_000).toISOString().replace(/\.\d{3}Z$/, 'Z');
+
 /** A seat row's mailbox slug — its `LANE#N` as the opener spells it in a ref — or null. Pure. */
 const seatSlugOf = (row) => seatKey(`${row.lane}#${row.seat}`)?.slug ?? null;
 
@@ -319,7 +360,7 @@ const keyOf = (r) => `${r.repo}#${r.number}`;
 const byRef = (a, b) => (a.repo === b.repo ? a.number - b.number : a.repo < b.repo ? -1 : 1);
 
 /**
- * snapshot = { repos: { 'owner/name': { seats, dispatched, rulings, pulls, comments: { '<n>': [...] } } } }
+ * snapshot = { repos: { 'owner/name': { seats, dispatched, rulings, pulls, comments: { '<n>': [...] }, recentComments } } }
  * → the roster rows, deterministically ordered (repo, lane, seat, post). Pure.
  */
 export function buildRows(snapshot, { now }) {
@@ -330,6 +371,8 @@ export function buildRows(snapshot, { now }) {
   const rulings = [];
   const pulls = [];
   const mailboxes = readMailboxes(snapshot);
+  const signed = signedActivity(snapshot);
+  const pullUpdatedAt = new Map(); // pull key → its updated_at, for the mailbox's share of last activity
   for (const repo of repos) {
     const s = snapshot.repos[repo] ?? {};
     for (const post of s.seats ?? []) {
@@ -350,7 +393,11 @@ export function buildRows(snapshot, { now }) {
     const asCard = (i) => ({ repo, number: i.number, labels: labelNames(i), assignees: assigneeLogins(i).map(lc), updatedAt: i.updated_at ?? null });
     for (const i of s.dispatched ?? []) if (!i.pull_request && i.state !== 'closed') cards.push(asCard(i));
     for (const i of s.rulings ?? []) if (!i.pull_request && i.state !== 'closed') rulings.push(asCard(i));
-    for (const p of s.pulls ?? []) if (p.state !== 'closed') pulls.push({ repo, pr: p, comments: s.comments?.[String(p.number)] ?? [] });
+    for (const p of s.pulls ?? []) {
+      if (p.state === 'closed') continue;
+      pulls.push({ repo, pr: p, comments: s.comments?.[String(p.number)] ?? [] });
+      pullUpdatedAt.set(keyOf(ref(repo, p.number)), p.updated_at ?? null);
+    }
   }
   rows.sort((a, b) => (a.repo !== b.repo ? (a.repo < b.repo ? -1 : 1) : a.lane !== b.lane ? (a.lane < b.lane ? -1 : 1) : a.seat !== b.seat ? a.seat - b.seat : a.post - b.post));
 
@@ -368,7 +415,10 @@ export function buildRows(snapshot, { now }) {
     const sharesWith = first !== row ? first.seat : null;
     const inFlight = row.account && sharesWith === null ? cards.filter((c) => cardLaneMatch(c, row) && c.assignees.includes(acct)) : [];
     const awaitingLanding = inFlight.flatMap((c) => landing.get(keyOf(c)) ?? []);
-    const times = [row.updatedAt, ...inFlight.map((c) => c.updatedAt)].filter(Boolean).sort();
+    // Per seat, never per account: one account holds several seats, and each seat opens its own.
+    const mailbox = mailboxes.filter((m) => m.slug !== null && m.slug === seatSlugOf(row)).map((m) => m.ref);
+    // The seat's own traces: a seat sharing its lane's account with a lower seat has no in-flight cards of its own.
+    const times = [row.updatedAt, ...inFlight.map((c) => c.updatedAt), ...mailbox.map((m) => pullUpdatedAt.get(keyOf(m))), signed.get(`${row.lane}#${row.seat}`)].filter(Boolean).sort();
     const lastActivity = times.at(-1) ?? null;
     const ageHours = lastActivity && Number.isFinite(nowMs) ? (nowMs - Date.parse(lastActivity)) / 3_600_000 : null;
     return {
@@ -379,8 +429,7 @@ export function buildRows(snapshot, { now }) {
       awaitingLanding: awaitingLanding.sort(byRef),
       lastActivity,
       suspectedWall: row.status === 'seated' && !isEpicLane(row.lane) && row.wallNote === null && ageHours !== null && ageHours > STALE_HOURS,
-      // Per seat, never per account: one account holds several seats, and each seat opens its own.
-      mailbox: mailboxes.filter((m) => m.slug !== null && m.slug === seatSlugOf(row)).map((m) => m.ref),
+      mailbox,
     };
   });
 
@@ -414,6 +463,7 @@ export function readsFor(repos) {
     `GET /repos/${r}/issues?state=open&labels=pm:dispatched`,
     `GET /repos/${r}/issues?state=open&labels=needs-user-decision`,
     `GET /repos/${r}/pulls?state=open`,
+    `GET /repos/${r}/issues/comments?since=(now − ${STALE_HOURS} h), each read for its first-line seat signature`,
     `GET /repos/${r}/issues/{n}/comments for each claude/ pull closing an in-flight card (${LEDGER_EXCLUSION} excluded)`,
   ]);
 }
@@ -483,7 +533,7 @@ function ghJson(path, { paginate = false } = {}) {
 }
 
 /** Read every repo into the snapshot shape `buildRows` takes; throws on the first failed read. */
-function readLive(repos) {
+function readLive(repos, { since }) {
   const need = (path, paginate = true) => {
     const r = ghJson(path, { paginate });
     if (!r.ok) throw new Error(`GET ${path} — ${r.error}`);
@@ -498,6 +548,7 @@ function readLive(repos) {
       rulings: need(`/repos/${repo}/issues?state=open&labels=needs-user-decision&per_page=100`),
       pulls: need(`/repos/${repo}/pulls?state=open&per_page=100`),
       comments: {},
+      recentComments: need(`/repos/${repo}/issues/comments?since=${encodeURIComponent(since)}&per_page=100`),
     };
     snapshot.repos[repo] = s;
   }
@@ -552,7 +603,7 @@ export async function main(argv, { env = process.env } = {}) {
     if (opts.fixture !== null) {
       snapshot = JSON.parse(readFileSync(opts.fixture, 'utf8'));
       repos = Object.keys(snapshot.repos ?? {}).sort();
-    } else snapshot = readLive(repos);
+    } else snapshot = readLive(repos, { since: activitySince(opts.now ?? new Date().toISOString()) });
   } catch (e) {
     console.error(`✗ fleet-roster: ${opts.fixture !== null ? `could not read the fixture ${opts.fixture}` : 'a read failed'} — ${e.message}. Nothing was written.`);
     return EXIT_PREREQUISITE;
@@ -606,12 +657,13 @@ const SELF_TEST_BATTERIES = Object.freeze({
   'seat titles: lane, seat, repo, status, account, project': 13,
   'wall notes, closing refs, verdicts and mailboxes': 13,
   'the fixture snapshot: rows for the three repos': 25,
+  'one account on two seats of a lane: the second seat reads its own traces': 13,
   'the rendered body: marker, columns, footer, determinism': 10,
   'refusing to overwrite what is not the roster': 6,
   'the CLI: fixture runs offline, usage errors are exit 2': 6,
   'paging: a three-page read through the loop equals the slurped array': 4,
 });
-const SELF_TEST_BATTERY_FLOOR = 8;
+const SELF_TEST_BATTERY_FLOOR = 9;
 
 async function selfTest() {
   let failed = 0;
@@ -732,6 +784,52 @@ async function selfTest() {
   t('last activity is the newest of post and in-flight cards', row(6023).lastActivity, '2026-10-23T13:28:00Z');
   t('one account on two seats of a lane: cards on the lowest seat, the other reads = seat 1', [row(5560, 'objectstack-ai/objectui').inFlight.length, row(10243, 'objectstack-ai/objectui').sharesWith, row(10243, 'objectstack-ai/objectui').inFlight, row(10243, 'objectstack-ai/objectui').suspectedWall], [1, 1, [], true]);
 
+  battery('one account on two seats of a lane: the second seat reads its own traces');
+  {
+    const NOW = '2026-11-02T04:00:00Z';
+    const R = 'objectstack-ai/objectstack';
+    const fresh = '2026-11-02T03:00:00Z'; // 1 h before NOW
+    const stale = '2026-11-01T20:00:00Z'; // 8 h before NOW, past STALE_HOURS
+    const sig = (laneSeat, account = 'os-pm') => `${laneSeat} · ${account} · session_01SharedSeatSess`;
+    const snap = ({ mailboxAt = null, comments = [], seat1MailboxAt = null } = {}) => ({
+      repos: {
+        [R]: {
+          seats: [
+            { number: 100, title: '[PM seat] domain:server — 🟢 os-pm', body: '', labels: ['pm:seat'], assignees: ['os-pm'], updated_at: '2026-10-30T00:00:00Z' },
+            { number: 200, title: '[PM seat] domain:server · seat 2 — 🟢 os-pm', body: '', labels: ['pm:seat'], assignees: ['os-pm'], updated_at: '2026-10-31T00:00:00Z' },
+          ],
+          dispatched: [{ number: 300, labels: ['pm:dispatched', 'domain:server'], assignees: ['os-pm'], updated_at: fresh }],
+          rulings: [],
+          pulls: [
+            ...(seat1MailboxAt ? [{ number: 401, state: 'open', head: { ref: 'mailbox/os-pm/server-1' }, body: 'Mailbox-of: domain:server#1 · os-pm', labels: ['pm:mailbox'], updated_at: seat1MailboxAt }] : []),
+            ...(mailboxAt ? [{ number: 402, state: 'open', head: { ref: 'mailbox/os-pm/server-2' }, body: 'Mailbox-of: domain:server#2 · os-pm', labels: ['pm:mailbox'], updated_at: mailboxAt }] : []),
+          ],
+          comments: {},
+          recentComments: comments,
+        },
+      },
+    });
+    const seat2 = (s) => (({ sharesWith, inFlight, mailbox, lastActivity, suspectedWall }) => ({ sharesWith, inFlight, mailbox, lastActivity, suspectedWall }))(buildRows(s, { now: NOW }).find((r) => r.post === 200));
+    t('no trace of its own: seat 2 reads = seat 1, its post alone, and is flagged', seat2(snap()), { sharesWith: 1, inFlight: [], mailbox: [], lastActivity: '2026-10-31T00:00:00Z', suspectedWall: true });
+    t('⭐ a fresh mailbox pull lifts the flag, and the in-flight cell still reads = seat 1', seat2(snap({ mailboxAt: fresh })), { sharesWith: 1, inFlight: [], mailbox: [{ repo: R, number: 402 }], lastActivity: fresh, suspectedWall: false });
+    t('⭐ a fresh comment signed domain:server#2 lifts the flag', seat2(snap({ comments: [{ body: `${sig('domain:server#2')}\n\n## 席位核对 — ACCEPT`, updated_at: fresh }] })), { sharesWith: 1, inFlight: [], mailbox: [], lastActivity: fresh, suspectedWall: false });
+    t('⛔ mailbox and signed comment both older than STALE_HOURS: flagged, last activity the newer of them', seat2(snap({ mailboxAt: stale, comments: [{ body: sig('domain:server#2'), updated_at: '2026-11-01T19:00:00Z' }] })), { sharesWith: 1, inFlight: [], mailbox: [{ repo: R, number: 402 }], lastActivity: stale, suspectedWall: true });
+    t('⛔ by seat, never by account: seat 1\'s fresh signed comment and fresh mailbox, same account, leave seat 2 flagged', seat2(snap({ seat1MailboxAt: fresh, comments: [{ body: sig('domain:server#1'), updated_at: fresh }] })).suspectedWall, true);
+    t('⛔ another lane\'s seat 2, or a seat-2 signature on a repo: lane, is not this seat', seat2(snap({ comments: [{ body: sig('domain:ui#2'), updated_at: fresh }, { body: sig('repo:server#2'), updated_at: fresh }] })).suspectedWall, true);
+    t('⛔ a signature that is not the FIRST non-empty line, or is spelled wrong, signs nothing', seat2(snap({ comments: [{ body: `Claim: x\n${sig('domain:server#2')}`, updated_at: fresh }, { body: 'domain:server#2 - os-pm - session_01SharedSeatSess', updated_at: fresh }, { body: 'domain:server#2 · os-pm · session_01x', updated_at: fresh }] })).suspectedWall, true);
+    t('the newest of the four traces wins, and the comment\'s updated_at is its time', seat2(snap({ mailboxAt: '2026-11-02T01:00:00Z', comments: [{ body: sig('domain:server#2'), created_at: '2026-11-02T00:00:00Z', updated_at: '2026-11-02T03:30:00Z' }, { body: sig('domain:server#2'), updated_at: '2026-11-02T02:00:00Z' }] })).lastActivity, '2026-11-02T03:30:00Z');
+    t('seat 1 keeps its cards and reads its own traces too', (({ inFlight, lastActivity, suspectedWall }) => ({ inFlight, lastActivity, suspectedWall }))(buildRows(snap({ comments: [{ body: sig('domain:server#1'), updated_at: '2026-11-02T03:45:00Z' }] }), { now: NOW }).find((r) => r.post === 100)), { inFlight: [{ repo: R, number: 300 }], lastActivity: '2026-11-02T03:45:00Z', suspectedWall: false });
+    t('the rendered row keeps = seat 1 and drops the flag once a trace is fresh', (() => {
+      const line = renderBody(buildRows(snap({ mailboxAt: fresh }), { now: NOW }), { now: NOW, repos: [R] }).split('\n').find((l) => l.includes('/issues/200)'));
+      return [line.includes('| = seat 1 |'), line.includes(SUSPECTED_WALL)];
+    })(), [true, false]);
+    t('the comment read starts STALE_HOURS before now, and the footer names it', [activitySince(NOW), readsFor([R]).some((q) => q.startsWith(`GET /repos/${R}/issues/comments?since=`))], ['2026-11-01T22:00:00Z', true]);
+    const { SEAT_SIGNATURE_LINE, readSignatureLine } = await import('./check-half-states.mjs');
+    t('the signature pattern is check-half-states\' SEAT_SIGNATURE_LINE, byte for byte — mirrored, not imported', [SIGNATURE_LINE.source === SEAT_SIGNATURE_LINE.source, SIGNATURE_LINE.flags === SEAT_SIGNATURE_LINE.flags], [true, true]);
+    const corpus = ['', sig('domain:server#2'), `\n\n  ${sig('domain:engine-core#3')}\r\nbody`, `body\n${sig('triage#1')}`, 'epic:#27293#1 · sunhaolin · session_017xRBcVBKAFk1ntXSjvPt7U', 'domain:server#0 · os-pm · session_01SharedSeatSess', 'domain:server#2 · os-pm · cse_01SharedSeatSess'];
+    t('signedSeatOf reads every body as readSignatureLine does', corpus.map(signedSeatOf), corpus.map((b) => { const r = readSignatureLine(b); return r ? `${r.lane}#${r.seat}` : null; }));
+  }
+
   battery('the rendered body: marker, columns, footer, determinism');
   const body = renderBody(rows, { now: fixture.now, repos: Object.keys(fixture.repos).sort(), session: 'cse_01ABC' });
   t('the body opens with the marker', body.split('\n')[0], ROSTER_MARKER);