Qgis 3,40.10 nor 3.44.2 Couldn't load qgis-stac-plugin

[lterpan]

When attempting to load the "Stac Api Browser" plugin, QGIS sends the following error message:

Could not load plugin 'qgis_stac' due to an error when calling its classFactory() method

ImportError: cannot import name 'validate_core_schema' from 'pydantic_core' (C:\OSGeo4W\apps\Python312\Lib\site-packages\pydantic_core_init_.py)
Traceback (most recent call last):
File "C:\OSGeo4W/apps/qgis-ltr/./python\qgis\utils.py", line 478, in startPlugin
plugins[packageName] = package.classFactory(iface)
^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Users/~/AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins\qgis_stac_init.py", line 41, in classFactory
from .main import QgisStac
File "C:\OSGeo4W/apps/qgis-ltr/./python\qgis\utils.py", line 1100, in _import
mod = _builtin_import(name, globals, locals, fromlist, level)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Users//AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins\qgis_stac\main.py", line 23, in
from .gui.qgis_stac_widget import QgisStacWidget
File "C:\OSGeo4W/apps/qgis-ltr/./python\qgis\utils.py", line 1100, in _import
mod = _builtin_import(name, globals, locals, fromlist, level)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Users//AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins\qgis_stac\gui\qgis_stac_widget.py", line 31, in
from ..gui.connection_dialog import ConnectionDialog
File "C:\OSGeo4W/apps/qgis-ltr/./python\qgis\utils.py", line 1100, in _import
mod = _builtin_import(name, globals, locals, fromlist, level)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Users//AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins\qgis_stac\gui\connection_dialog.py", line 26, in
from ..api.client import Client
File "C:\OSGeo4W/apps/qgis-ltr/./python\qgis\utils.py", line 1100, in _import
mod = _builtin_import(name, globals, locals, fromlist, level)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Users//AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins\qgis_stac\api\client.py", line 9, in
from .base import BaseClient
File "C:\OSGeo4W/apps/qgis-ltr/./python\qgis\utils.py", line 1100, in _import
mod = _builtin_import(name, globals, locals, fromlist, level)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Users//AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins\qgis_stac\api\base.py", line 28, in
from .network import ContentFetcherTask, NetworkFetcher
File "C:\OSGeo4W/apps/qgis-ltr/./python\qgis\utils.py", line 1100, in _import
mod = _builtin_import(name, globals, locals, fromlist, level)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Users//AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins\qgis_stac\api\network.py", line 47, in
from ..lib import planetary_computer as pc
File "C:\OSGeo4W/apps/qgis-ltr/./python\qgis\utils.py", line 1100, in _import
mod = builtin_import(name, globals, locals, fromlist, level)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Users/~/AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins\qgis_stac\lib\planetary_computer_init.py", line 4, in
from planetary_computer.sas import (
File "C:\OSGeo4W/apps/qgis-ltr/./python\qgis\utils.py", line 1100, in _import
mod = builtin_import(name, globals, locals, fromlist, level)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Users~\AppData\Roaming\QGIS\QGIS3\profiles\default\python\plugins\qgis_stac\lib\planetary_computer_init.py", line 4, in
from planetary_computer.sas import (
File "C:\OSGeo4W/apps/qgis-ltr/./python\qgis\utils.py", line 1100, in _import
mod = _builtin_import(name, globals, locals, fromlist, level)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Users~\AppData\Roaming\QGIS\QGIS3\profiles\default\python\plugins\qgis_stac\lib\planetary_computer\sas.py", line 9, in
from pydantic import BaseModel, Field
File "C:\OSGeo4W/apps/qgis-ltr/./python\qgis\utils.py", line 1100, in import
mod = builtin_import(name, globals, locals, fromlist, level)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\OSGeo4W\apps\Python312\Lib\site-packages\pydantic_init.py", line 435, in getattr
module = import_module(module_name, package=package)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\OSGeo4W\apps\Python312\Lib\importlib_init.py", line 90, in import_module
return _bootstrap._gcd_import(name[level:], package, level)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\OSGeo4W\apps\Python312\Lib\site-packages\pydantic\main.py", line 36, in
from ._internal import (
File "C:\OSGeo4W/apps/qgis-ltr/./python\qgis\utils.py", line 1100, in _import
mod = _builtin_import(name, globals, locals, fromlist, level)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\OSGeo4W\apps\Python312\Lib\site-packages\pydantic_internal_decorators.py", line 18, in
from ._core_utils import get_type_ref
File "C:\OSGeo4W/apps/qgis-ltr/./python\qgis\utils.py", line 1100, in _import
mod = _builtin_import(name, globals, locals, fromlist, level)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\OSGeo4W\apps\Python312\Lib\site-packages\pydantic_internal_core_utils.py", line 9, in
from pydantic_core import validate_core_schema as validate_core_schema
ImportError: cannot import name 'validate_core_schema' from 'pydantic_core' (C:\OSGeo4W\apps\Python312\Lib\site-packages\pydantic_core_init.py)

Python version: 3.12.11 (main, Jun 17 2025, 13:41:12) [MSC v.1943 64 bit (AMD64)]
QGIS version: 3.40.10-Bratislava Bratislava, c98da2e682

Python Path:
C:/OSGeo4W/apps/qgis-ltr/./python
C:/Users//AppData/Roaming/QGIS/QGIS3\profiles\default/python
C:/Users//AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins
C:/OSGeo4W/apps/qgis-ltr/./python/plugins
C:\OSGeo4W\apps\grass\grass84\etc\python
C:\Windows\System32
C:\OSGeo4W\bin\python312.zip
C:\OSGeo4W\apps\Python312\DLLs
C:\OSGeo4W\apps\Python312\Lib
C:\OSGeo4W\bin
C:\OSGeo4W\apps\Python312
C:\OSGeo4W\apps\Python312\Lib\site-packages
C:\OSGeo4W\apps\Python312\Lib\site-packages\win32
C:\OSGeo4W\apps\Python312\Lib\site-packages\win32\lib
C:\OSGeo4W\apps\Python312\Lib\site-packages\Pythonwin
C:/Users//AppData/Roaming/QGIS/QGIS3\profiles\default/python
C:\Users\AppData\Roaming\QGIS\QGIS3\profiles\default\python\plugins\kmltools\libs
C:\Users~\AppData\Roaming\QGIS\QGIS3\profiles\default\python\plugins\qfieldsync\libqfieldsync_62853968a3cc98953ff7f41f8770a7f9d1b6a80e.whl
C:\Users//AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins\qgis_resource_sharing
C:\Users\AppData\Roaming\QGIS\QGIS3\profiles\default\python\plugins\qgis_resource_sharing
C:\Users~\AppData\Roaming\QGIS\QGIS3\profiles\default\python\plugins\qgis_resource_sharing\ext_libs
C:\Users~\AppData\Roaming\QGIS\QGIS3\profiles\default\python\plugins\qgis_stac\lib

This occurs with QGIS versions 3.40.10 and 3.44.2:
Installed Python Version: 3.12.11 (main, Jun 17 2025, 13:41:12) [MSC v.1943 64 bit (AMD64)]

[whereisagnes]

(First time commenting and I don't know a lot about programming and computer science, so excuse any incorrect terminology, and feel free to correct me)

I've just had the exact same issue after having recently downloaded QGIS and trying to use the STAC API Browser plugin.

Thought at first it was an issue with how I had installed QGIS (standalone installer vs OSGeo4W) or what packages I had installed, but after reinstalling from OSGeo4W with a bunch of libraries selected it still didn't work.

I solved the issue by downgrading the version of Pydantic used by QGIS from version 2 to version 1. This may of course cause issues elsewhere down the line, but in that case I'll just update Pydantic again. I only need to use the plugin once at the moment, hence it's not a big issue in my case, but it may not be the best solution for others.

This worked for me with QGIS installed with OSGeo4W on Windows 11:

• Open OSGeo4W Shell
• Run pip show pydantic to check what version is currently used
• To downgrade Pydantic: pip install "pydantic<2.0"
• Restart QGIS

I'm still a bit confused about why this is an issue in the first place though, since the latest update of the plugin was in April 2024, well after the release of Pydantic version 2 (June 2023)?