diff --git a/pyproject.toml b/pyproject.toml
index 06e90dc..fb65601 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -5,6 +5,7 @@ classifiers = [
     "Programming Language :: Python :: 3.10",
     "Programming Language :: Python :: 3.11",
     "Programming Language :: Python :: 3.12",
+    "Programming Language :: Python :: 3.13",
     "Programming Language :: Python :: 3.8",
     "Programming Language :: Python :: 3.9",
     "Topic :: Software Development :: Libraries :: Application Frameworks",
diff --git a/tox.ini b/tox.ini
index 2c70125..bae5008 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,4 +1,5 @@
 [tox]
+isolated_build = true
 envlist = py38, py39, py310, py311, py312, py313
 min_version = 4.0
 requires = tox-uv
@@ -7,12 +8,14 @@ skipsdist = true
 [testenv]
 uv_sync = true
 deps =
-    .
-    .[tox]
+    .[dev]
 commands =
-    pytest -m "not slow" -n 2 --dist=loadfile {posargs}
-passenv = *
+    pytest -m "not slow" {posargs}
+passenv =
+    CI
+    GITHUB_*
+    UV_*
+    PYTHON*
 setenv =
     PYTHONPATH = {toxinidir}/src
     PYTHONDONTWRITEBYTECODE = 1
-    QT_QPA_PLATFORM = offscreen