diff --git a/plugins/docker/ingest.py b/plugins/docker/ingest.py
index 9efc563..027ce95 100644
--- a/plugins/docker/ingest.py
+++ b/plugins/docker/ingest.py
@@ -147,12 +147,36 @@ async def _persist_logs(session, host, log_batches) -> None:
     if not await get_setting(session, "docker.logs.enabled"):
         return
     exclude = set(await get_setting(session, "docker.logs.exclude") or ())
-    for row in _log_rows(log_batches, host.id):
-        if row["container_name"] in exclude:
+    rows = [r for r in _log_rows(log_batches, host.id) if r["container_name"] not in exclude]
+    stored = await _stored_lines(session, host.id, rows)
+    for row in rows:
+        if (row["container_name"], row["ts"], row["stream"], row["line"]) in stored:
             continue
         session.add(DockerLog(**row))
 
 
+async def _stored_lines(session, host_id: str, rows: list) -> set:
+    """The lines of `rows` this host already has, as (container, ts, stream,
+    line). A restarted agent has lost its cursors and re-sends each
+    container's last lines (#5809); a push of new lines overlaps nothing, so
+    the one query, bounded per container to the batch's own span, finds none."""
+    from sqlalchemy import and_, or_, select
+    from .models import DockerLog
+
+    spans: dict[str, list] = {}
+    for r in rows:
+        span = spans.setdefault(r["container_name"], [r["ts"], r["ts"]])
+        span[0], span[1] = min(span[0], r["ts"]), max(span[1], r["ts"])
+    if not spans:
+        return set()
+    found = await session.execute(
+        select(DockerLog.container_name, DockerLog.ts, DockerLog.stream, DockerLog.line)
+        .where(DockerLog.host_id == host_id, or_(*(
+            and_(DockerLog.container_name == name, DockerLog.ts.between(lo, hi))
+            for name, (lo, hi) in spans.items()))))
+    return {tuple(r) for r in found}
+
+
 async def _persist_swarm(session, host, swarm: dict) -> None:
     """Upsert this manager's swarm topology; drop rows no longer reported.
 
diff --git a/tests/integration/test_docker.py b/tests/integration/test_docker.py
index 80abc77..909efa5 100644
--- a/tests/integration/test_docker.py
+++ b/tests/integration/test_docker.py
@@ -221,6 +221,55 @@ def test_persist_logs_stores_lines(app):
     ]
 
 
+@_NEEDS_DB
+def test_persist_logs_skips_lines_a_restarted_agent_sends_again(app):
+    """#5809: a restarted agent has lost its cursors and re-sends each
+    container's last lines. Those are stored once; a new line, or another line
+    at the same instant, is still kept."""
+    from types import SimpleNamespace
+    from sqlalchemy import text
+    from steward.models.hosts import Host
+
+    persist = _persist_fn(app)
+    now = datetime.now(timezone.utc)
+
+    def line(container, at, text_, stream="stdout"):
+        return {"container": container, "stream": stream,
+                "ts": f"2026-01-01T00:00:0{at}+00:00", "line": text_}
+
+    first = [(now, [line("web", 1, "started"), line("web", 2, "listening"),
+                    line("db", 1, "ready")])]
+    again = [(now, [line("web", 1, "started"), line("web", 2, "listening"),
+                    line("web", 2, "worker 2 up"), line("web", 3, "GET /"),
+                    line("db", 1, "ready"), line("db", 1, "ready", stream="stderr")])]
+
+    hid = str(uuid.uuid4())
+    host = SimpleNamespace(id=hid, name="loghost-again")  # as below: no expiry across commits
+
+    async def _go():
+        async with app.db_sessionmaker() as s:
+            async with s.begin():
+                s.add(Host(id=hid, name="loghost-again", address="10.0.0.19"))
+                await s.flush()
+                await persist(s, host, [], None, None, first)
+            async with s.begin():
+                await persist(s, host, [], None, None, again)
+            rows = (await s.execute(text(
+                "SELECT container_name, stream, line FROM docker_logs "
+                "WHERE host_id = :h ORDER BY container_name, ts, stream, line"),
+                {"h": hid})).all()
+            return [tuple(r) for r in rows]
+
+    assert asyncio.run(_go()) == [
+        ("db", "stderr", "ready"),
+        ("db", "stdout", "ready"),
+        ("web", "stdout", "started"),
+        ("web", "stdout", "listening"),
+        ("web", "stdout", "worker 2 up"),
+        ("web", "stdout", "GET /"),
+    ]
+
+
 @_NEEDS_DB
 def test_persist_logs_respects_toggle_and_exclude(app):
     """Server-side controls (Settings): an excluded container's lines are dropped