Figures collapsing in bokeh tabs wrapped in bokeh column only when rendered with Panel

[PrateekArya]

ALL software version info

(this library, plus any other relevant software, e.g. bokeh, python, notebook, OS, browser, etc should be added within the dropdown below.)

Software Version Info

python==3.10.16
bokeh==3.9.1 
panel==1.9.3
holoviews==1.21.0

Description of expected behavior and the observed behavior

Bokeh figures are collapsing (in size) when rendered (via pn.panel(fig).show()) when the figures are placed in Bokeh Tabs wrapped in Bokeh column. They should be rendered correctly.

All works fine if one uses pn.Column instead of bokeh.layouts.column or uses bokeh.plotting.show for rendering!

Complete, minimal, self-contained example code that reproduces the issue

from bokeh.plotting import figure, show
from bokeh.models import TabPanel, Tabs
from bokeh.layouts import row, column

import panel as pn

x = list(range(11))
y0 = x
y1 = [10 - i for i in x]
y2 = [abs(i - 5) for i in x]

# create three plots
s1 = figure(background_fill_color="#fafafa", aspect_ratio=1)
s1.scatter(x, y0, size=12, alpha=0.8, color="#53777a")

s2 = figure(background_fill_color="#fafafa", aspect_ratio=1)
s2.scatter(x, y1, size=12, alpha=0.8, color="#c02942")

s3 = figure(background_fill_color="#fafafa", aspect_ratio=1)
s3.scatter(x, y2, size=12, alpha=0.8, color="#d95b43")

figsList = [row(s1, Tabs(tabs=[TabPanel(child=s2, title="s2"), TabPanel(child=s3, title="s3")]), height=800, sizing_mode="inherit"), 
       row(s1, Tabs(tabs=[TabPanel(child=s2, title="s2"), TabPanel(child=s3, title="s3")]), height=800, sizing_mode="inherit")]

# show(column(*figsList))  # Works well

# pn.panel(pn.Column(*figsList)).show()  # Works well!

pn.panel(column(*figsList)).show()  # Not working as expected!

Screenshots or screencasts of the bug in action

• I may be interested in making a pull request to address this

[adityaanikam]

Traced this down to two separate pieces working together rather than one bug. pn.panel(bokeh_column) resolves to the Bokeh pane since a raw bokeh.layouts.column is a LayoutDOM but not a Viewable, and Bokeh._get_model treats the wrapped object as opaque, model = self.object, it never recurses into or rewraps the nested Tabs or figures, so their own sizing_mode is untouched by Panel directly. But Bokeh._updates is unset, so it inherits Pane._updates = False, which means _get_root_model still wraps it in self.layout, a Panel Row built with no explicit sizing_mode, before rendering. Your raw column's inherit sizing_mode was authored assuming its real parent supplies concrete sizing, and that assumption breaks once Panel inserts an extra, independently sized Row above it. Using pn.Column instead avoids this because Panel recurses through its own children and builds a fresh Bokeh pane leaf per figure, so there's no extra opaque layer sitting between Panel's wrapper and the Tabs.

This looks like it has at least three defensible fixes: make the Bokeh pane recursively re-derive sizing_mode when wrapping a tree that's already built, skip the extra Row wrapper when a lone Bokeh pane is already the root, or just document that raw bokeh layouts using inherit sizing aren't fully supported through pn.panel(). Which direction fits how Panel wants to handle opaque bokeh trees generally?