Tabulator row_content does not display Holoviews plot

While trying to revive an old app of mine, I ran into a weird problem. The panel info from my freshly install conda env is

Python version        :  3.12.10 | packaged by conda-forge | (main, Apr 10 2025, 22:08:16) [MSC v.1943 64 bit (AMD64)]
IPython version       :  9.2.0
Tornado version       :  6.4.2
NumPy version         :  2.2.5
Bokeh version         :  3.7.2
BokehJS static path   :  C:\Users\felder\AppData\Local\mambaforge\envs\panel\Lib\site-packages\bokeh\server\static
node.js version       :  v20.10.0
npm version           :  10.2.3
jupyter_bokeh version :  (not installed)
Operating system      :  Windows-11-10.0.26100-SP0

Here is my test code:

import holoviews as hv
import numpy as np
import pandas as pd
import panel as pn

pn.extension("tabulator")  # <- leave holoviews out!

df = pd.DataFrame(dict(id=[1, 2, 3], amp=[1, 0.7, 1.3], freq=[1, 2, 0.5]))


def row_plot(row):
    x = np.linspace(0, 2 * np.pi, 200)
    y = row.amp * np.sin(row.freq * x)
    curve = hv.Curve((x, y)).opts(width=450, height=220)  # <- fixed size
    return pn.pane.HoloViews(curve)  # displays nothing!
    # return pn.pane.Markdown(str(curve)) # displays text correctly


tab = pn.widgets.Tabulator(
    df,
    row_content=row_plot,
    embed_content=False,  # makes not difference
    height=240,
    sizing_mode="stretch_width",
)


# make another dummy plot
def dummy_plot():
    x = np.linspace(0, 2 * np.pi, 200)
    y = np.sin(x)
    curve = hv.Curve((x, y)).opts(width=450, height=220)  # <- fixed size
    return pn.pane.HoloViews(curve)  # displays correctly


pn.Column("### Click a ▸ – a sine wave should appear", tab, dummy_plot()).servable()

I’m running this with panel serve testapp.py.

As you can see from the comments, I get a standalone Holoviews plot alright, and Markdown row_content. But plots in the row_content fail to appear. Browser console says “bokeh rendered successfully”, no errors in Python console, Private tab makes no difference, developer tools show a row_content <div> when using Markdown, but the Holoviews plot does not show up in a <div>: nothing happens to the DOM when I click the triangle. Same effect when reinstalling the conda env under Linux. I’m at a loss here.

Even the best AI can’t make my row content plot reappear. Can you?