fix: docutils error

Author: dgarcia360

docs/source/upgrade/1-8-to-1-9.rst

@@ -12,6 +12,11 @@ The theme version is displayed in the footer of the project's documentation site
 
 If your project theme's version is **>=1.8**, follow this guide to get the latest version.
 
+Known issues
+------------
+
+- **sphinx-tabs incompatible with docutils 0.22+**: ``sphinx-tabs`` 3.4.7 (latest) raises a ``KeyError: 'backrefs'`` when building with docutils 0.22 or later (`executablebooks/sphinx-tabs#212 <https://github.com/executablebooks/sphinx-tabs/issues/212>`_). As a workaround, pin ``docutils<0.22`` in your project's dependencies until a new ``sphinx-tabs`` release is available.
+
 What's new in 1.9
 ------------------
 

pyproject.toml

@@ -6,7 +6,7 @@ authors = [{name = "David García", email = "david@techdocs.studio"}]
 readme = "PYPI.rst"
 requires-python = ">=3.11"
 dependencies = [
-    "sphinx-collapse>=0.1.1,<0.2",
+    "sphinx-collapse>=0.1.4,<0.2",
     "sphinx-copybutton>=0.5.2,<0.6",
     "beautifulsoup4>=4.12.3,<5",
     "sphinx-tabs>=3.4.5,<4",
@@ -31,6 +31,7 @@ breathe = "^4.36.0"
 [dependency-groups]
 dev = [
     "sphinx>=9.0",
+    "docutils<0.22",  # pin until sphinx-tabs releases a fix for KeyError: 'backrefs' (executablebooks/sphinx-tabs#212)
     "pytest>=9.0.1",
     "sphinx-autobuild>=2025.08.25",
     "pre-commit>=4.5.0",
@@ -41,9 +42,6 @@ dev = [
     "breathe>=4.36.0,<5",
 ]
 
-
-
-
 [build-system]
 requires = ["hatchling"]
 build-backend = "hatchling.build"