diff --git a/superset/commands/dashboard/update.py b/superset/commands/dashboard/update.py
index 56d15befb3f9..dd81d96deeb1 100644
--- a/superset/commands/dashboard/update.py
+++ b/superset/commands/dashboard/update.py
@@ -66,6 +66,10 @@ def run(self) -> Model:
         if (tags := self._properties.pop("tags", None)) is not None:
             update_tags(ObjectType.dashboard, self._model.id, self._model.tags, tags)
 
+        # Re-serialize position_json to escape 4-byte Unicode characters
+        if position_json := self._properties.get("position_json"):
+            self._properties["position_json"] = json.dumps(json.loads(position_json))
+
         dashboard = DashboardDAO.update(self._model, self._properties)
         if self._properties.get("json_metadata"):
             DashboardDAO.set_dash_metadata(
diff --git a/tests/integration_tests/dashboards/test_update_emoji.py b/tests/integration_tests/dashboards/test_update_emoji.py
new file mode 100644
index 000000000000..28abf0e70ed5
--- /dev/null
+++ b/tests/integration_tests/dashboards/test_update_emoji.py
@@ -0,0 +1,111 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+"""Tests that emoji characters in position_json are persisted correctly via PUT."""
+
+from superset import db
+from superset.models.dashboard import Dashboard
+from superset.utils import json
+from tests.integration_tests.base_tests import SupersetTestCase
+from tests.integration_tests.constants import ADMIN_USERNAME
+
+# position_json payload containing a 4-byte emoji in a MARKDOWN component,
+# matching the real-world payload that triggered the truncation bug
+POSITION_JSON_WITH_EMOJI = json.dumps(
+    {
+        "DASHBOARD_VERSION_KEY": "v2",
+        "ROOT_ID": {"type": "ROOT", "id": "ROOT_ID", "children": ["GRID_ID"]},
+        "GRID_ID": {
+            "type": "GRID",
+            "id": "GRID_ID",
+            "children": ["ROW-test"],
+            "parents": ["ROOT_ID"],
+        },
+        "ROW-test": {
+            "type": "ROW",
+            "id": "ROW-test",
+            "children": ["MARKDOWN-test"],
+            "parents": ["ROOT_ID", "GRID_ID"],
+            "meta": {"background": "BACKGROUND_TRANSPARENT"},
+        },
+        "MARKDOWN-test": {
+            "type": "MARKDOWN",
+            "id": "MARKDOWN-test",
+            "children": [],
+            "parents": ["ROOT_ID", "GRID_ID", "ROW-test"],
+            "meta": {"code": "📈 See Tab\n\ntest\ntest2", "height": 50, "width": 4},
+        },
+    },
+)
+
+
+class TestDashboardUpdateEmoji(SupersetTestCase):
+    """Verify that emoji in position_json survive a dashboard PUT round-trip."""
+
+    def setUp(self) -> None:
+        super().setUp()
+        admin = self.get_user("admin")
+        self.dashboard = self.insert_dashboard(
+            "emoji test dashboard", "emoji-test-slug", [admin.id]
+        )
+
+    def tearDown(self) -> None:
+        db.session.delete(self.dashboard)
+        db.session.commit()
+        super().tearDown()
+
+    def test_position_json_emoji_survives_put(self) -> None:
+        """Emoji in position_json must be stored and retrievable after PUT."""
+        self.login(ADMIN_USERNAME)
+        uri = f"api/v1/dashboard/{self.dashboard.id}"
+
+        rv = self.client.put(
+            uri,
+            json={"position_json": POSITION_JSON_WITH_EMOJI},
+        )
+
+        assert rv.status_code == 200, rv.json
+
+        db.session.expire(self.dashboard)
+        saved = db.session.get(Dashboard, self.dashboard.id)
+        assert saved is not None
+
+        parsed = json.loads(saved.position_json)
+        code = parsed["MARKDOWN-test"]["meta"]["code"]
+
+        # The emoji and the text after it must not be truncated
+        assert code == "📈 See Tab\n\ntest\ntest2"
+
+    def test_position_json_emoji_is_ascii_safe_in_db(self) -> None:
+        """position_json stored in DB must be ASCII-safe (emoji escaped as \\uXXXX)
+        so it is safe for MySQL utf8 (3-byte) charset columns."""
+        self.login(ADMIN_USERNAME)
+        uri = f"api/v1/dashboard/{self.dashboard.id}"
+
+        rv = self.client.put(
+            uri,
+            json={"position_json": POSITION_JSON_WITH_EMOJI},
+        )
+
+        assert rv.status_code == 200, rv.json
+
+        db.session.expire(self.dashboard)
+        saved = db.session.get(Dashboard, self.dashboard.id)
+        assert saved is not None
+
+        # Raw 4-byte emoji must not appear in the stored string
+        assert "📈" not in saved.position_json
+        assert all(ord(c) < 128 for c in saved.position_json)