diff --git a/src/sdlc_hub/modules/wiki/commands.py b/src/sdlc_hub/modules/wiki/commands.py
index 6084c97..f01509a 100644
--- a/src/sdlc_hub/modules/wiki/commands.py
+++ b/src/sdlc_hub/modules/wiki/commands.py
@@ -47,16 +47,38 @@ def validate(cmds) -> list[dict]:
     return out
 
 
+def _active_same_root(conn, label: str, root: str) -> int | None:
+    """id самого нового пакета проекта с wiki_sync того же корня в queued/claimed или None."""
+    row = conn.execute(
+        "SELECT batch_id FROM command WHERE type = 'wiki_sync' AND status IN ('queued', 'claimed') "
+        "AND json_extract(params, '$.label') = ? AND json_extract(params, '$.root') = ? ORDER BY batch_id DESC LIMIT 1",
+        (label, root)).fetchone()
+    return row["batch_id"] if row else None
+
+
 def check_batch(conn, cmds, project, files_dir) -> list[dict]:
-    """wiki_sync живёт в пакете своего проекта: project пакета равен label команды."""
+    """wiki_sync живёт в пакете своего проекта: project пакета равен label команды. Вторая живая синхронизация того же
+    корня не ставится — ни через POST /batches, ни повтором команды (T8.3); другой корень не мешает (смена корня)."""
     for i, c in enumerate(cmds, 1):
-        if c["type"] == "wiki_sync" and c["params"]["label"] != project:
+        if c["type"] != "wiki_sync":
+            continue
+        if c["params"]["label"] != project:
             raise CommandError(f"команда {i}: проект пакета ({project}) не равен label ({c['params']['label']})")
+        bid = _active_same_root(conn, project, c["params"]["root"])
+        if bid is not None:
+            raise CommandError(f"команда {i}: у проекта {project} уже идёт синхронизация корня {c['params']['root']} "
+                               f"(пакет #{bid})")
     return cmds
 
 
 def enqueue_sync(conn, label: str, root: str, author: str) -> dict:
-    """Пакет «Вики <метка>» из одной команды wiki_sync."""
+    """Пакет «Вики <метка>» из одной команды wiki_sync. Идёт синхронизация того же корня (возврат корня A → B → A,
+    пока A у агента) — её пакет в той же форме {id, estimate_seconds, count}, нового нет."""
+    bid = _active_same_root(conn, label, root)
+    if bid is not None:
+        row = conn.execute("SELECT b.estimate_seconds, (SELECT COUNT(*) FROM command c WHERE c.batch_id = b.id) AS n "
+                           "FROM batch b WHERE b.id = ?", (bid,)).fetchone()
+        return {"id": bid, "estimate_seconds": row["estimate_seconds"], "count": row["n"]}
     return queue.create_batch(conn, f"Вики {label}", author, [{"type": "wiki_sync", "params": {"label": label, "root": root}}],
                               project=label)
 
diff --git a/tests/test_wiki_commands.py b/tests/test_wiki_commands.py
index 70497be..fbd3866 100644
--- a/tests/test_wiki_commands.py
+++ b/tests/test_wiki_commands.py
@@ -128,3 +128,32 @@ def test_validate_settings(key, bad, good):
 def test_wiki_agent_gets_own_keys(conn):
     out = settings.for_agent(conn, "wiki")
     assert out == {"wiki_pacing": 0.2, "settings_version": 1}
+
+
+# пакет D (#135): T8.3 — одна синхронизация на корень
+SYNC = [{"type": "wiki_sync", "params": {"label": "AWPCA", "root": "DOC-1"}}]
+
+
+def test_check_batch_refuses_second_sync_same_root(conn):
+    b = queue.create_batch(conn, "t", "u", SYNC, project="AWPCA")
+    with pytest.raises(CommandError, match=f"#{b['id']}"):
+        queue.create_batch(conn, "t", "u", SYNC, project="AWPCA")
+
+
+def test_check_batch_other_root_allowed(conn):
+    queue.create_batch(conn, "t", "u", SYNC, project="AWPCA")
+    other = [{"type": "wiki_sync", "params": {"label": "AWPCA", "root": "DOC-2"}}]
+    assert queue.create_batch(conn, "t", "u", other, project="AWPCA")["count"] == 1
+
+
+def test_retry_failed_sync_without_active_passes(conn):
+    b = queue.create_batch(conn, "t", "u", SYNC, project="AWPCA")
+    conn.execute("UPDATE command SET status = 'failed' WHERE batch_id = ?", (b["id"],))
+    assert queue.create_batch(conn, "t", "u", SYNC, project="AWPCA")["count"] == 1
+
+
+def test_enqueue_sync_returns_active_same_root(conn):
+    _root(conn)
+    first = commands.enqueue_sync(conn, "AWPCA", "DOC-1", "u")
+    again = commands.enqueue_sync(conn, "AWPCA", "DOC-1", "u")
+    assert again == first and _count(conn) == 1
diff --git a/tests/test_wiki_projects.py b/tests/test_wiki_projects.py
index fe51f38..aeb396b 100644
--- a/tests/test_wiki_projects.py
+++ b/tests/test_wiki_projects.py
@@ -190,3 +190,34 @@ def test_create_project_batches(hub_server):
     c.post("/projects", {"label": "AWPCA", "name": "A"})
     patched = c.patch("/projects/AWPCA", {"wiki_root": "DOC-000777"})
     assert patched["batches"] == [{"module": "wiki", "id": patched["batch_ids"][0]}]
+
+
+def test_root_back_while_old_claimed(hub_server):
+    """A → B → A, пока синхронизация A у агента: PATCH не 422, идущий пакет A остаётся (#135, T8.3)."""
+    c = hub_server["client"]
+    c.post("/projects", {"label": "AWPCA", "name": "АРМ КА", "wiki_root": "DOC-12"})
+    conn = hub_server["hub"].conn()
+    try:
+        conn.execute("UPDATE command SET status = 'claimed' WHERE type = 'wiki_sync'")
+    finally:
+        conn.close()
+    c.patch("/projects/AWPCA", {"wiki_root": "DOC-21"})
+    c.patch("/projects/AWPCA", {"wiki_root": "DOC-12"})
+    assert [(s, p["root"]) for _, s, p in _syncs(hub_server["hub"])] == [("claimed", "DOC-12"), ("cancelled", "DOC-21")]
+
+
+def test_retry_while_sync_running_refused(hub_server):
+    """Повтор упавшей wiki_sync при идущей того же корня — 422 с номером идущего пакета (#135, T8.3)."""
+    c = hub_server["client"]
+    c.post("/projects", {"label": "AWPCA", "name": "АРМ КА", "wiki_root": "DOC-1"})
+    conn = hub_server["hub"].conn()
+    try:
+        failed = conn.execute("SELECT id FROM command WHERE type = 'wiki_sync'").fetchone()["id"]
+        conn.execute("UPDATE command SET status = 'failed' WHERE id = ?", (failed,))
+    finally:
+        conn.close()
+    running = c.post("/wiki/sync", {"project": "AWPCA"})["batch_id"]
+    with pytest.raises(HubError) as e:
+        c.post(f"/commands/{failed}/retry", {})
+    assert e.value.status == 422 and f"#{running}" in str(e.value)
+    assert len(_syncs(hub_server["hub"])) == 2