RuntimeError: Models must be owned by only a single document with ImportedStyleSheet after upgrading to Panel 1.6.3 (from 1.3.8))

ivanna · April 30, 2025, 1:57pm

I’ve encountered an issue after upgrading my app from Panel 1.3.8 to Panel 1.6.3.

Everything worked fine with version 1.3.8, but after upgrading to 1.6.3, I started getting the following error under specific circumstances:

RuntimeError: Models must be owned by only a single document, ImportedStyleSheet(id='p1108', ...) is already in a doc

This happens when I follow these steps in my app:

Navigate to the Article page.
Click the “Start local session” button (this dynamically updates part of the layout).
Navigate to the Settings page.
Return to the Article page.
Click the “Start local session” button again.

At this point, the error is triggered. The same code and workflow worked without issues in Panel 1.3.8.

From the error message, it seems to be related to the ImportedStyleSheet being added to the Bokeh document multiple times. My guess is that some components (maybe a template or a dynamically created view) are being reused or not properly cleaned up when switching pages.

I’ve created a minimal reproducible example that demonstrates the issue and would be happy to share it if helpful.

github.com

parfeniukir/panel-error-example/blob/e1c86b6698b0200717ea7a6b6f0753700b7c1b09/src/app.py

import panel as pn
from tornado.ioloop import IOLoop
from abc import ABC, abstractmethod
from jinja2 import Template
from param.parameterized import Event
from typing import Optional
from functools import partial


class PanelAbstract(ABC):
    @property
    @abstractmethod
    def is_root(self):
        """Show if panel is root panel."""

    @property
    @abstractmethod
    def template(self):
        """Navigation bar element template."""

This file has been truncated. show original

Could you help me understand what changed in recent versions that might be causing this? And what is the recommended way to avoid or handle this error?

Thank you in advance for your time and support!

Full traceback

Exception in callback functools.partial(<bound method IOLoop._discard_future_result of <tornado.platform.asyncio.AsyncIOMainLoop object at 0x105d0b700>>, <Task finished name='Task-304' coro=<ServerSession.with_document_locked() done, defined at /Users/ivannaparfeniuk/.local/share/virtualenvs/panel_example-ClUGGO8J/lib/python3.10/site-packages/bokeh/server/session.py:77> exception=RuntimeError("Models must be owned by only a single document, ImportedStyleSheet(id='p1094', ...) is already in a doc")>)
Traceback (most recent call last):
  File "/Users/ivannaparfeniuk/.local/share/virtualenvs/panel_example-ClUGGO8J/lib/python3.10/site-packages/tornado/ioloop.py", line 750, in _run_callback
    ret = callback()
  File "/Users/ivannaparfeniuk/.local/share/virtualenvs/panel_example-ClUGGO8J/lib/python3.10/site-packages/tornado/ioloop.py", line 774, in _discard_future_result
    future.result()
  File "/Users/ivannaparfeniuk/.local/share/virtualenvs/panel_example-ClUGGO8J/lib/python3.10/site-packages/bokeh/server/session.py", line 94, in _needs_document_lock_wrapper
    result = func(self, *args, **kwargs)
  File "/Users/ivannaparfeniuk/.local/share/virtualenvs/panel_example-ClUGGO8J/lib/python3.10/site-packages/bokeh/server/session.py", line 226, in with_document_locked
    return func(*args, **kwargs)
  File "/Users/ivannaparfeniuk/.local/share/virtualenvs/panel_example-ClUGGO8J/lib/python3.10/site-packages/bokeh/document/callbacks.py", line 495, in wrapper
    return invoke_with_curdoc(doc, invoke)
  File "/Users/ivannaparfeniuk/.local/share/virtualenvs/panel_example-ClUGGO8J/lib/python3.10/site-packages/bokeh/document/callbacks.py", line 453, in invoke_with_curdoc
    return f()
  File "/Users/ivannaparfeniuk/.local/share/virtualenvs/panel_example-ClUGGO8J/lib/python3.10/site-packages/bokeh/document/callbacks.py", line 494, in invoke
    return f(*args, **kwargs)
  File "/Users/ivannaparfeniuk/.local/share/virtualenvs/panel_example-ClUGGO8J/lib/python3.10/site-packages/bokeh/document/callbacks.py", line 184, in remove_then_invoke
    return callback()
  File "/Users/ivannaparfeniuk/.local/share/virtualenvs/panel_example-ClUGGO8J/lib/python3.10/site-packages/panel/reactive.py", line 326, in _scheduled_update_model
    self._update_model(events, msg, root, model, doc, comm)
  File "/Users/ivannaparfeniuk/.local/share/virtualenvs/panel_example-ClUGGO8J/lib/python3.10/site-packages/panel/layout/base.py", line 257, in _update_model
    with freeze_doc(doc, model, msg, force=update_children):
  File "/opt/homebrew/Cellar/python@3.10/3.10.17/Frameworks/Python.framework/Versions/3.10/lib/python3.10/contextlib.py", line 142, in __exit__
    next(self.gen)
  File "/Users/ivannaparfeniuk/.local/share/virtualenvs/panel_example-ClUGGO8J/lib/python3.10/site-packages/panel/io/document.py", line 624, in freeze_doc
    doc.models._pop_freeze()
  File "/Users/ivannaparfeniuk/.local/share/virtualenvs/panel_example-ClUGGO8J/lib/python3.10/site-packages/bokeh/document/models.py", line 288, in _pop_freeze
    self.recompute()
  File "/Users/ivannaparfeniuk/.local/share/virtualenvs/panel_example-ClUGGO8J/lib/python3.10/site-packages/bokeh/document/models.py", line 235, in recompute
    ma._attach_document(document)
  File "/Users/ivannaparfeniuk/.local/share/virtualenvs/panel_example-ClUGGO8J/lib/python3.10/site-packages/bokeh/model/model.py", line 596, in _attach_document
    raise RuntimeError(f"Models must be owned by only a single document, {self!r} is already in a doc")
RuntimeError: Models must be owned by only a single document, ImportedStyleSheet(id='p1094', ...) is already in a doc

ahuang11 · April 30, 2025, 5:23pm

Thanks for sharing. Can you report this on GitHub?

dwr-psandhu · April 30, 2025, 8:02pm

Great, I was getting this but couldn’t quite reproduce it. Thanks

ivanna · May 1, 2025, 5:52am

Sure, of course

github.com/holoviz/panel

RuntimeError: Models must be owned by only a single document with ImportedStyleSheet after upgrading to Panel 1.6.3 (from 1.3.8))

opened 07:27AM - 01 May 25 UTC

iparfeniuk

#### ALL software version info <details> <summary>Software Version Info</su…mmary> ```plaintext macOS == 15.4.1 python == 3.10 panel == 1.6.3 bokeh == 3.7.2 param == 2.2.0 tornado == 6.4 ``` </details> #### Description of expected behavior and the observed behavior I’ve encountered an issue after upgrading my app from Panel 1.3.8 to Panel 1.6.3. Everything worked fine with version 1.3.8, but after upgrading to 1.6.3, I started getting the following error under specific circumstances: RuntimeError: Models must be owned by only a single document, ImportedStyleSheet(id='p1108', ...) is already in a doc This happens when I follow these steps in my app: 1. Navigate to the Article page. 2. Click the “Start local session” button (this dynamically updates part of the layout). 3. Navigate to the Settings page. 4. Return to the Article page. 5. Click the “Start local session” button again. 6. At this point, the error is triggered. The same code and workflow worked without issues in Panel 1.3.8. From the error message, it seems to be related to the ImportedStyleSheet being added to the Bokeh document multiple times. My guess is that some components (maybe a template or a dynamically created view) are being reused or not properly cleaned up when switching pages. I’ve created a minimal reproducible example that demonstrates the issue and would be happy to share it if helpful. #### Complete, minimal, self-contained example code that reproduces the issue <details> <summary>Minimal reproducible example</summary> ```python import panel as pn from tornado.ioloop import IOLoop from abc import ABC, abstractmethod from jinja2 import Template from param.parameterized import Event from typing import Optional from functools import partial class PanelAbstract(ABC): @property @abstractmethod def is_root(self): """Show if panel is root panel.""" @property @abstractmethod def template(self): """Navigation bar element template.""" @property @abstractmethod def href(self): """Navigation bar element href.""" @property @abstractmethod def title(self): """Navigation bar element title.""" @abstractmethod def build_template(self): """Template initialize method.""" @abstractmethod def add_sidebar(self, sidebar_html): """Add sidebar to the template.""" class Panel(PanelAbstract, ABC): def __init__(self): self._root = False self._template = pn.template.MaterialTemplate(title=self.title) self.build_template() def get_page(self): return self._template def add_sidebar(self, sidebar_html): navigation_bar = pn.pane.HTML(sidebar_html) self._template.sidebar.append(navigation_bar) self._template.sidebar_width = 150 @property def is_root(self): return self._root @property def template(self): return self._template class Articles(Panel): href = "articles" title = "Articles" def __init__(self): self._session_control_col: Optional[pn.Column] = None super().__init__() def _filter_protocols(self, event: Event = None, **kwargs): pass def _clean_articl_list(self): try: if "Articles" in self._session_control_col[-1][0].title: print("Cleaning article list") self._session_control_col.pop(-1) except AttributeError: pass except TypeError: pass def _get_articles( self, event: Event = None, ): self._clean_articl_list() self._article_name = pn.widgets.TextInput(name="Article name") articles_card = pn.Card( self._article_name, title="Articles", styles={"background": "WhiteSmoke"}, ) filter_article_by_name = pn.widgets.TextInput( name="Filter by article name", placeholder="Enter article name", ) submit_filter_button = pn.widgets.Button( name="Filter", button_type="primary", on_click=partial( self._filter_protocols, filter_by_name=filter_article_by_name, ), ) filters_card = pn.Card( filter_article_by_name, submit_filter_button, title="Filters", styles={"background": "WhiteSmoke"}, ) articles_column = pn.Column( articles_card, filters_card, ) print("-----------\n", self._session_control_col) self._session_control_col.append(articles_column) def build_template(self): start_local_session_btn = pn.widgets.Button( name="Start local session", on_click=partial( self._get_articles, ), ) self._session_control_col = pn.Column(start_local_session_btn) self._template.main.append(self._session_control_col) class Settings(Panel): href = "settings" title = "Settings" def build_template(self): self._template.main.append( pn.pane.Markdown( """ ## Settings This is the settings page. """ ) ) def get_navigation_bar_html(panel_list: list[Panel]): navigation_bar_template = """ <ul> {% for href, title in items %} <li><a href="{{ href }}">{{ title }}</a></li> {% endfor %} </ul> """ li_elements = [ (panel.href, panel.title) if not panel.is_root else ("/", panel.title) for panel in panel_list ] template = Template(navigation_bar_template) navigation_bar_html = template.render(items=li_elements) return navigation_bar_html loop = IOLoop.current() articles = Articles() settings = Settings() panels = [articles, settings] navigation_bar_html = get_navigation_bar_html(panels) for panel in panels: panel.add_sidebar(navigation_bar_html) panel_routes = dict() for panel in panels: panel_routes[panel.href] = panel.get_page if panel.is_root: panel_routes[""] = panel.get_page pn.serve(panels=panel_routes, loop=loop) ``` </details> <details> <summary>Traceback</summary> ```plaintext Exception in callback functools.partial(<bound method IOLoop._discard_future_result of <tornado.platform.asyncio.AsyncIOMainLoop object at 0x1083575e0>>, <Task finished name='Task-380' coro=<ServerSession.with_document_locked() done, defined at /Users/ivannaparfeniuk/.local/share/virtualenvs/panel_example-ClUGGO8J/lib/python3.10/site-packages/bokeh/server/session.py:77> exception=RuntimeError("Models must be owned by only a single document, ImportedStyleSheet(id='p1145', ...) is already in a doc")>) Traceback (most recent call last): File "/Users/ivannaparfeniuk/.local/share/virtualenvs/panel_example-ClUGGO8J/lib/python3.10/site-packages/tornado/ioloop.py", line 750, in _run_callback ret = callback() File "/Users/ivannaparfeniuk/.local/share/virtualenvs/panel_example-ClUGGO8J/lib/python3.10/site-packages/tornado/ioloop.py", line 774, in _discard_future_result future.result() File "/Users/ivannaparfeniuk/.local/share/virtualenvs/panel_example-ClUGGO8J/lib/python3.10/site-packages/bokeh/server/session.py", line 94, in _needs_document_lock_wrapper result = func(self, *args, **kwargs) File "/Users/ivannaparfeniuk/.local/share/virtualenvs/panel_example-ClUGGO8J/lib/python3.10/site-packages/bokeh/server/session.py", line 226, in with_document_locked return func(*args, **kwargs) File "/Users/ivannaparfeniuk/.local/share/virtualenvs/panel_example-ClUGGO8J/lib/python3.10/site-packages/bokeh/document/callbacks.py", line 495, in wrapper return invoke_with_curdoc(doc, invoke) File "/Users/ivannaparfeniuk/.local/share/virtualenvs/panel_example-ClUGGO8J/lib/python3.10/site-packages/bokeh/document/callbacks.py", line 453, in invoke_with_curdoc return f() File "/Users/ivannaparfeniuk/.local/share/virtualenvs/panel_example-ClUGGO8J/lib/python3.10/site-packages/bokeh/document/callbacks.py", line 494, in invoke return f(*args, **kwargs) File "/Users/ivannaparfeniuk/.local/share/virtualenvs/panel_example-ClUGGO8J/lib/python3.10/site-packages/bokeh/document/callbacks.py", line 184, in remove_then_invoke return callback() File "/Users/ivannaparfeniuk/.local/share/virtualenvs/panel_example-ClUGGO8J/lib/python3.10/site-packages/panel/reactive.py", line 326, in _scheduled_update_model self._update_model(events, msg, root, model, doc, comm) File "/Users/ivannaparfeniuk/.local/share/virtualenvs/panel_example-ClUGGO8J/lib/python3.10/site-packages/panel/layout/base.py", line 257, in _update_model with freeze_doc(doc, model, msg, force=update_children): File "/opt/homebrew/Cellar/python@3.10/3.10.17/Frameworks/Python.framework/Versions/3.10/lib/python3.10/contextlib.py", line 142, in __exit__ next(self.gen) File "/Users/ivannaparfeniuk/.local/share/virtualenvs/panel_example-ClUGGO8J/lib/python3.10/site-packages/panel/io/document.py", line 624, in freeze_doc doc.models._pop_freeze() File "/Users/ivannaparfeniuk/.local/share/virtualenvs/panel_example-ClUGGO8J/lib/python3.10/site-packages/bokeh/document/models.py", line 288, in _pop_freeze self.recompute() File "/Users/ivannaparfeniuk/.local/share/virtualenvs/panel_example-ClUGGO8J/lib/python3.10/site-packages/bokeh/document/models.py", line 235, in recompute ma._attach_document(document) File "/Users/ivannaparfeniuk/.local/share/virtualenvs/panel_example-ClUGGO8J/lib/python3.10/site-packages/bokeh/model/model.py", line 596, in _attach_document raise RuntimeError(f"Models must be owned by only a single document, {self!r} is already in a doc") RuntimeError: Models must be owned by only a single document, ImportedStyleSheet(id='p1145', ...) is already in a doc ``` </details> #### Screenshots or screencasts of the bug in action **panel version 1.6.3** https://github.com/user-attachments/assets/5dd3ca10-3841-4291-b918-0f9e4e008d34 **panel version 1.3.8** https://github.com/user-attachments/assets/086340e8-9b44-463b-9adc-750e5aa79a7a