diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index fe5d4fd..6252b97 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -14,7 +14,7 @@ jobs:
   test:
     strategy:
       matrix:
-        python-version: [3.9, "3.10", 3.11, 3.12, 3.13]
+        python-version: [3.9, "3.10", 3.11, 3.12, 3.13, 3.14]
         os: [ubuntu-latest]
       fail-fast: false
 
diff --git a/pyproject.toml b/pyproject.toml
index 63337cc..551a3cf 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -17,6 +17,8 @@ classifiers = [
     "Programming Language :: Python :: 3.10",
     "Programming Language :: Python :: 3.11",
     "Programming Language :: Python :: 3.12",
+    "Programming Language :: Python :: 3.13",
+    "Programming Language :: Python :: 3.14",
 ]
 requires-python = ">=3.9"
 license = {text = "MIT license"}
diff --git a/requirements.sh b/requirements.sh
index 18482f1..1fba851 100755
--- a/requirements.sh
+++ b/requirements.sh
@@ -5,4 +5,6 @@ set -u
 
 cd "$(dirname "$0")"
 
-python3.10 -m piptools compile "pyproject.toml" --extra "dev"
+python3 -m uv pip compile "pyproject.toml" \
+    --extra "dev" --python-version "3.9" \
+    | tee requirements.txt
diff --git a/requirements.txt b/requirements.txt
index 32c7f56..74417f6 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,48 +1,53 @@
-#
-# This file is autogenerated by pip-compile with Python 3.10
-# by the following command:
-#
-#    pip-compile --extra=dev pyproject.toml
-#
+# This file was autogenerated by uv via the following command:
+#    uv pip compile pyproject.toml --extra dev --python-version 3.9
 black==22.10.0
     # via joinem (pyproject.toml)
-build==1.0.3
+build==1.4.0
     # via pip-tools
 bump2version==1.0.1
     # via joinem (pyproject.toml)
-click==8.1.7
+click==8.1.8
     # via
     #   black
     #   pip-tools
+importlib-metadata==8.7.1
+    # via build
 isort==5.12.0
     # via joinem (pyproject.toml)
-mypy-extensions==1.0.0
+mypy-extensions==1.1.0
     # via black
-packaging==23.2
-    # via build
-pathspec==0.12.1
+packaging==26.0
+    # via
+    #   build
+    #   wheel
+pathspec==1.0.4
     # via black
+pip==26.0.1
+    # via pip-tools
 pip-tools==7.3.0
     # via joinem (pyproject.toml)
-platformdirs==4.2.0
+platformdirs==4.4.0
     # via black
-polars==1.26.0
+polars==1.36.1
     # via joinem (pyproject.toml)
-pyproject-hooks==1.0.0
+polars-runtime-32==1.36.1
+    # via polars
+pyproject-hooks==1.2.0
     # via build
 ruff==0.1.11
     # via joinem (pyproject.toml)
-tomli==2.0.1
+setuptools==82.0.0
+    # via pip-tools
+tomli==2.4.0
     # via
     #   black
     #   build
     #   pip-tools
-    #   pyproject-hooks
-tqdm==4.66.2
+tqdm==4.67.3
     # via joinem (pyproject.toml)
-wheel==0.42.0
+typing-extensions==4.15.0
+    # via black
+wheel==0.46.3
     # via pip-tools
-
-# The following packages are considered to be unsafe in a requirements file:
-# pip
-# setuptools
+zipp==3.23.0
+    # via importlib-metadata
diff --git a/tests/assets/horizontal1.pqt b/tests/assets/horizontal1.pqt
new file mode 100644
index 0000000..5938af0
Binary files /dev/null and b/tests/assets/horizontal1.pqt differ
diff --git a/tests/assets/horizontal2.pqt b/tests/assets/horizontal2.pqt
new file mode 100644
index 0000000..fc41a4f
Binary files /dev/null and b/tests/assets/horizontal2.pqt differ
diff --git a/tests/test_smoke.sh b/tests/test_smoke.sh
index e637856..fdf41f5 100755
--- a/tests/test_smoke.sh
+++ b/tests/test_smoke.sh
@@ -61,3 +61,7 @@ cat assets/x.0.csv | python3 -m joinem "/dev/stdout" --stdin --read-kwarg infer_
 cat assets/x.0.csv.gz | python3 -m joinem "/dev/stdout" --stdin --output-filetype csv --input-filetype csv --shrink-dtypes > out/stdout
 
 cat assets/x.0.csv.gz | python3 -m joinem "/dev/stdout" --stdin --output-filetype csv --input-filetype csv.gz --string-cache > out/stdout
+
+ls assets/horizontal{1,2}.pqt | python3 -m joinem out/horizontal.csv --how horizontal
+
+ls assets/horizontal{1,2}.pqt | python3 -m joinem out/horizontal.pqt --how horizontal --shrink-dtypes