diff --git a/src/models/zone.py b/src/models/zone.py
index 173ffc4..5e53333 100644
--- a/src/models/zone.py
+++ b/src/models/zone.py
@@ -21,8 +21,8 @@ def _maybe_migrate_tab_json_to_zone():
 class Zone(Model):
     """Preset layout row (stored in ``db/zone.json``); legacy storage was ``tab.json`` / Tab.
 
-    Optional ``content_kind`` on a row: ``\"presets\"`` (preset tiles only) or ``\"sequences\"``
-    (sequence tiles only). Legacy rows without ``content_kind`` are inferred on load.
+    Optional legacy ``content_kind`` (``\"presets\"`` / ``\"sequences\"``) is kept for older data;
+    zones may hold both preset tiles and ``sequence_ids``.
     """
 
     def __init__(self):
@@ -95,13 +95,8 @@ class Zone(Model):
         return "presets"
 
     def _enforce_content_kind_invariants(self, doc):
-        """Presets-only zones hold no sequences; sequences-only hold no preset tiles."""
-        kind = self._normalized_content_kind(doc)
-        if kind == "presets":
-            doc["sequence_ids"] = []
-        elif kind == "sequences":
-            doc["presets"] = []
-            doc["presets_flat"] = []
+        """No-op: presets and sequences may coexist on one zone."""
+        _ = doc
 
     def create(self, name="", names=None, presets=None, group_ids=None, content_kind=None):
         next_id = self.get_next_id()
@@ -135,13 +130,7 @@ class Zone(Model):
         if id_str not in self:
             return False
         patch = dict(data) if isinstance(data, dict) else {}
-        doc = self[id_str]
-        locked_kind = self._normalized_content_kind(doc) or self._infer_content_kind(doc)
-        if "content_kind" in patch:
-            patch["content_kind"] = locked_kind
         self[id_str].update(patch)
-        if "content_kind" in patch:
-            self._enforce_content_kind_invariants(self[id_str])
         self.save()
         return True
 
diff --git a/tests/test_zone_content_kind.py b/tests/test_zone_content_kind.py
index e0e49a6..bcc4315 100644
--- a/tests/test_zone_content_kind.py
+++ b/tests/test_zone_content_kind.py
@@ -1,4 +1,4 @@
-"""Zone content_kind is fixed after create."""
+"""Zones may hold both presets and sequences."""
 
 import json
 import os
@@ -12,7 +12,7 @@ sys.path.insert(0, str(PROJECT_ROOT / "src"))
 from models.zone import Zone  # noqa: E402
 
 
-def test_update_cannot_change_content_kind():
+def test_zone_presets_and_sequences_can_coexist():
     with tempfile.TemporaryDirectory() as tmp:
         path = os.path.join(tmp, "zone.json")
         with open(path, "w", encoding="utf-8") as f:
@@ -20,8 +20,16 @@ def test_update_cannot_change_content_kind():
         z = Zone()
         z.file = path
         z.clear()
-        zid = z.create("preset zone", group_ids=[], content_kind="presets")
-        z.update(zid, {"content_kind": "sequences", "name": "preset zone"})
+        zid = z.create("mixed zone", group_ids=[], content_kind="presets")
+        z.update(
+            zid,
+            {
+                "presets": [["p1", "p2"]],
+                "sequence_ids": ["seq1"],
+            },
+        )
         doc = z.read(zid)
-        assert doc["content_kind"] == "presets"
-        assert doc.get("sequence_ids") == []
+        assert doc.get("sequence_ids") == ["seq1"]
+        preset_ids = Zone._preset_ids_in_doc(doc)
+        assert "p1" in preset_ids
+        assert "p2" in preset_ids