Patch webgl give different result on 3.10

Software versions

Python version : 3.14.7 | packaged by conda-forge | (main, Sep 2 2026, 21:08:32) [GCC 15.3.0] IPython version : 9.17.1 Tornado version : 6.5.8 NumPy version : 2.5.3 Bokeh version : 3.10.0 BokehJS static path : /home/shh/.local/conda/envs/holoviz/lib/python3.14/site-packages/bokeh/server/static node.js version : v26.8.1 npm version : 11.19.0 jupyter_bokeh version : 4.1.0 Operating system : Linux-7.2.4-arch1-2-x86_64-with-glibc2.44

Browser name and version

No response

Jupyter notebook / Jupyter Lab version

No response

Expected behavior

WebGL should match canvas, seems to be caused by https://github.com/bokeh/bokeh/pull/14853

Observed behavior

It does not.

Example code

import numpy as np
from bokeh.layouts import row
from bokeh.plotting import figure, show

xs = np.linspace(0, np.pi * 4, 40)
x = np.concatenate([xs, xs[::-1]])
y = np.concatenate([np.zeros(40), np.sin(xs)[::-1]])

plots = []
for backend in ["webgl", "canvas"]:
    p = figure(title=backend, output_backend=backend, width=300, height=300)
    p.patch(x, y)
    plots.append(p)

show(row(*plots))

Stack traceback or browser console output

No response

Screenshots