Acknowledge Vibe reads after agent turns (#464)

ddiff --git a/server/chat/agent-routes.js b/server/chat/agent-routes.js
iindex 5f8a9b7..e0ec293 100644
---- a/server/chat/agent-routes.js
++++ b/server/chat/agent-routes.js
@@@ -56,13 +56,16 @@ router.get('/:roomId/digest', room.guard('chat.agent_digest.read'), async (req,
              res.set('Retry-After', '20');
              return res.status(429).json({ error: 'The digest was read a moment ago', code: 'agent_digest.too_soon' });
          }
++        // A caller acknowledges this watermark only after its run reports/ends. Until then the durable read cursor
++        // does not advance, so a failed run can fetch the same messages again.
++        const watermark = await db.get('SELECT COALESCE(MAX(id), 0) AS id FROM room_messages WHERE room_id = ? AND is_deleted = 0', [row.id]);
          const out = await room.digest(row, { since, now });
++        res.set('OpenVibe-Read-Through', String(Number(watermark && watermark.id) || 0));
          await db.run(
--            `INSERT INTO agent_room_reads (room_id, reader, last_read_at, last_message_id, last_read_at_ms, updated_at)
--             VALUES (?, ?, now(), ?, ?, now())
--             ON CONFLICT (room_id, reader) DO UPDATE SET last_read_at = now(), last_message_id = EXCLUDED.last_message_id,
--                 last_read_at_ms = EXCLUDED.last_read_at_ms, updated_at = now()`,
--            [row.id, reader, Number(cursor && cursor.last_message_id) || 0, now]
++            `INSERT INTO agent_room_reads (room_id, reader, last_read_at_ms, updated_at)
++             VALUES (?, ?, ?, now())
++             ON CONFLICT (room_id, reader) DO UPDATE SET last_read_at_ms = EXCLUDED.last_read_at_ms, updated_at = now()`,
++            [row.id, reader, now]
          );
          res.set('Cache-Control', 'no-store');
          res.json(out);
@@@ -72,6 +75,29 @@ router.get('/:roomId/digest', room.guard('chat.agent_digest.read'), async (req,
      }
  });
  
++/** Advance the durable read cursor after the caller's run has reported or ended. */
++router.post('/:roomId/digest/ack', room.guard('chat.agent_digest.read'), async (req, res) => {
++    try {
++        const row = await loadRoom(req, res);
++        if (!row) return;
++        const through = Number(req.body && req.body.through);
++        if (!Number.isSafeInteger(through) || through < 0) return res.status(422).json({ error: 'A valid read watermark is required', code: 'agent_digest.invalid_watermark' });
++        const reader = String(req.principal.sub || '');
++        const max = await db.get('SELECT COALESCE(MAX(id), 0) AS id FROM room_messages WHERE room_id = ?', [row.id]);
++        if (through > Number(max && max.id || 0)) return res.status(422).json({ error: 'The read watermark is beyond this room', code: 'agent_digest.invalid_watermark' });
++        await db.run(`INSERT INTO agent_room_reads (room_id, reader, last_read_at, last_message_id, updated_at)
++            VALUES (?, ?, now(), ?, now())
++            ON CONFLICT (room_id, reader) DO UPDATE SET
++                last_read_at = CASE WHEN EXCLUDED.last_message_id >= agent_room_reads.last_message_id THEN now() ELSE agent_room_reads.last_read_at END,
++                last_message_id = GREATEST(agent_room_reads.last_message_id, EXCLUDED.last_message_id), updated_at = now()`,
++        [row.id, reader, through]);
++        res.set('Cache-Control', 'no-store').json({ read_through: through });
++    } catch (err) {
++        console.error('[Chat] the digest acknowledgement failed:', err.message);
++        res.status(500).json({ error: 'The digest acknowledgement could not be saved', code: 'agent_digest.ack_failed' });
++    }
++});
++
  // ── The polls ────────────────────────────────────────────────────────────
  
  /** The options the agent wrote, cleaned: two to four, each with its number and its text. */
ddiff --git a/test/agent-copilot.test.js b/test/agent-copilot.test.js
iindex 414bbd0..1771a9d 100644
---- a/test/agent-copilot.test.js
++++ b/test/agent-copilot.test.js
@@@ -130,6 +130,15 @@ t('the digest needs a service token that names the owner', async () => {
      const r = await h.http('GET', `/api/v1/rooms/${room.slug}/digest`, { token: ok });
      assert.strictEqual(r.status, 200, r.text);
      assert.ok(Array.isArray(r.body.items));
++    const through = Number(r.headers.get('openvibe-read-through'));
++    assert.ok(Number.isSafeInteger(through) && through >= 0, 'digest carries a cursor to acknowledge after the agent turn');
++    const ack = await h.http('POST', `/api/v1/rooms/${room.slug}/digest/ack`, { token: ok, body: { through } });
++    assert.strictEqual(ack.status, 200, ack.text);
++    assert.strictEqual(Number(ack.body.read_through), through);
++    const cursor = await db.get('SELECT last_message_id, last_read_at FROM agent_room_reads WHERE room_id = ? AND reader = ?', [room.id, ann.subject_id]);
++    assert.strictEqual(Number(cursor.last_message_id), through, 'only the explicit end-of-turn acknowledgement advances the cursor');
++    assert.ok(cursor.last_read_at);
++    assert.strictEqual((await h.http('POST', `/api/v1/rooms/${room.slug}/digest/ack`, { token: ok, body: { through: through + 10_000_000 } })).status, 422);
      assert.ok(agentRoom.READ_INTERVAL_MS > 0);
  });