Stable PyPI release needed: 2026.7.20 cannot display structures with current pymatgen and flask-caching

[computron]

The latest stable release (2026.7.20) no longer displays any Structure or Molecule in Jupyter for a fresh install. I would like a stable PyPI release that fixes both of the problems below, so that my pymatgen and atomate2 tutorials can go back to a plain pip install crystal-toolkit.

Repro in a fresh environment (a fresh pip install crystal-toolkit jupyter today gives crystal-toolkit 2026.7.20, pymatgen 2026.9.24 / pymatgen-core 2026.9.23, flask-caching 2.5.1, dash 3.4.0; tested on Python 3.12 with JupyterLab 4.6.4):

import crystal_toolkit
from pymatgen.core import Lattice, Structure
Structure(Lattice.cubic(3.9), ["Pb"], [[0, 0, 0]])  # last line of a notebook cell

1. pymatgen >= 2026.9.23 removed StructureGraph.with_empty_graph / with_local_env_strategy and the MoleculeGraph equivalents ([Breaking] Remove deprecated function/class/methods whose deadlines are in 2025 pymatgen-core#103). This is fixed on main in Fix deprecated from pmg #542, but so far only in pre-releases (e.g. 2026.8.28rc4). The from_* replacements already exist in pymatgen 2024.10.22, the current minimum in the requirements, so Fix deprecated from pmg #542 does not need a new pymatgen floor.

   AttributeError: type object 'StructureGraph' has no attribute 'with_empty_graph'
   

2. flask-caching >= 2.5.0 (released 2026-08-24) removed the lowercase cache-type aliases. This is [Bug]: Flask-Caching compatibility issue: need explicit class name #544 and is not fixed yet, including in 2026.8.28rc4.

   ImportStringError: import_string() failed for 'flask_caching.backends.simple'.
   

   The fix is more than the one line in [Bug]: Flask-Caching compatibility issue: need explicit class name #544. Every lowercase CACHE_TYPE needs its class name:

   • crystal_toolkit/core/plugin.py: "simple" -> "SimpleCache", and "null" -> "NullCache" (the DEBUG_MODE path breaks the same way)
   • crystal_toolkit/apps/main.py: "null" -> "NullCache" and "redis" -> "RedisCache"

   The class names also work on older flask-caching (Cache(config={"CACHE_TYPE": "SimpleCache"}) and "NullCache" initialize on 2.2.0 and 2.4.1), so no new minimum version is needed.

A release with only #542 still breaks every structure display because of (2).

For now the tutorials pin to the following, which works with pymatgen 2026.9.24 on Python 3.12 and 3.14:

pip install "crystal-toolkit==2026.8.28rc4" "flask-caching<2.5"

I tested this by executing the pymatgen tutorial notebooks (https://github.com/computron/pymatgen_tutorials, Parts 1, 4, and 5; all structure and molecule displays render) and the structure display cell in https://github.com/computron/atomate2_tutorials Part 1. Once there is a release, I will switch both back to an unpinned install.