diff --git a/.github/workflows/rhiza_benchmark.yml b/.github/workflows/rhiza_benchmark.yml
index 5484c3a3..ccf7996f 100644
--- a/.github/workflows/rhiza_benchmark.yml
+++ b/.github/workflows/rhiza_benchmark.yml
@@ -20,5 +20,5 @@ on:
 
 jobs:
   benchmark:
-    uses: jebel-quant/rhiza/.github/workflows/rhiza_benchmark.yml@v0.16.0
+    uses: jebel-quant/rhiza/.github/workflows/rhiza_benchmark.yml@v0.18.4
     secrets: inherit
diff --git a/.github/workflows/rhiza_book.yml b/.github/workflows/rhiza_book.yml
index 11e7da2a..c2c4034e 100644
--- a/.github/workflows/rhiza_book.yml
+++ b/.github/workflows/rhiza_book.yml
@@ -24,7 +24,7 @@ on:
 
 jobs:
   book:
-    uses: jebel-quant/rhiza/.github/workflows/rhiza_book.yml@v0.16.0
+    uses: jebel-quant/rhiza/.github/workflows/rhiza_book.yml@v0.18.4
     secrets: inherit
     permissions:
       contents: read
diff --git a/.github/workflows/rhiza_ci.yml b/.github/workflows/rhiza_ci.yml
index acf8e75f..755df1de 100644
--- a/.github/workflows/rhiza_ci.yml
+++ b/.github/workflows/rhiza_ci.yml
@@ -21,5 +21,5 @@ on:
 
 jobs:
   ci:
-    uses: jebel-quant/rhiza/.github/workflows/rhiza_ci.yml@v0.16.0
+    uses: jebel-quant/rhiza/.github/workflows/rhiza_ci.yml@v0.18.4
     secrets: inherit
diff --git a/.github/workflows/rhiza_codeql.yml b/.github/workflows/rhiza_codeql.yml
index e78d05d1..29a9fb04 100644
--- a/.github/workflows/rhiza_codeql.yml
+++ b/.github/workflows/rhiza_codeql.yml
@@ -42,5 +42,5 @@ on:
 
 jobs:
   codeql:
-    uses: jebel-quant/rhiza/.github/workflows/rhiza_codeql.yml@v0.16.0
+    uses: jebel-quant/rhiza/.github/workflows/rhiza_codeql.yml@v0.18.4
     secrets: inherit
diff --git a/.github/workflows/rhiza_marimo.yml b/.github/workflows/rhiza_marimo.yml
index 67f29cc9..47e602ed 100644
--- a/.github/workflows/rhiza_marimo.yml
+++ b/.github/workflows/rhiza_marimo.yml
@@ -28,5 +28,5 @@ on:
 
 jobs:
   marimo:
-    uses: jebel-quant/rhiza/.github/workflows/rhiza_marimo.yml@v0.16.0
+    uses: jebel-quant/rhiza/.github/workflows/rhiza_marimo.yml@v0.18.4
     secrets: inherit
diff --git a/.github/workflows/rhiza_release.yml b/.github/workflows/rhiza_release.yml
index 7b94ee17..3a555a07 100644
--- a/.github/workflows/rhiza_release.yml
+++ b/.github/workflows/rhiza_release.yml
@@ -154,7 +154,7 @@ jobs:
           version: "0.11.16"
 
       - name: Configure git auth for private packages
-        uses: jebel-quant/rhiza/.github/actions/configure-git-auth@v0.15.2
+        uses: jebel-quant/rhiza/.github/actions/configure-git-auth@v0.18.4
         with:
           token: ${{ secrets.GH_PAT }}
 
diff --git a/.github/workflows/rhiza_sync.yml b/.github/workflows/rhiza_sync.yml
index a9b79185..f3eb45c4 100644
--- a/.github/workflows/rhiza_sync.yml
+++ b/.github/workflows/rhiza_sync.yml
@@ -28,7 +28,7 @@ on:
 
 jobs:
   sync:
-    uses: jebel-quant/rhiza/.github/workflows/rhiza_sync.yml@v0.16.0
+    uses: jebel-quant/rhiza/.github/workflows/rhiza_sync.yml@v0.18.4
     with:
       direct: ${{ github.event_name == 'push' }}
       create-pr: ${{ github.event_name != 'push' && (github.event_name == 'schedule' || inputs.create-pr == true) }}
diff --git a/.github/workflows/rhiza_weekly.yml b/.github/workflows/rhiza_weekly.yml
index d56ac34b..27801ade 100644
--- a/.github/workflows/rhiza_weekly.yml
+++ b/.github/workflows/rhiza_weekly.yml
@@ -25,5 +25,5 @@ on:
 
 jobs:
   weekly:
-    uses: jebel-quant/rhiza/.github/workflows/rhiza_weekly.yml@v0.16.0
+    uses: jebel-quant/rhiza/.github/workflows/rhiza_weekly.yml@v0.18.4
     secrets: inherit
diff --git a/pyproject.toml b/pyproject.toml
index 0a2f9115..46893b31 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -11,7 +11,7 @@ dependencies = [
     "narwhals>=2.0.0",
     "numpy>=2.0.0",
     "plotly>=6.0.0",
-    "polars>=1.18.0",
+    "polars>=1.35.2",
     "scipy>=1.14.1"
 ]
 license = "MIT"
diff --git a/tests/test_jquantstats/test__utils/test_utils.py b/tests/test_jquantstats/test__utils/test_utils.py
index 359ad8e9..91957fa8 100644
--- a/tests/test_jquantstats/test__utils/test_utils.py
+++ b/tests/test_jquantstats/test__utils/test_utils.py
@@ -7,6 +7,7 @@
 from __future__ import annotations
 
 import math
+import sys
 from datetime import date, timedelta
 from pathlib import Path
 
@@ -524,6 +525,10 @@ def test_exponential_cov_late_start_asset_partial(multi_asset_data):
     assert not np.isnan(cov[date(2020, 1, 3)][1, 1])
 
 
+@pytest.mark.skipif(
+    sys.platform == "win32",
+    reason="memory-intensive EWM covariance computation crashes the xdist worker on Windows CI",
+)
 def test_exponential_cov_matches_pandas_stock_prices():
     """exponential_cov must match pandas ewm(span).cov(bias=True) on real stock data.
 
diff --git a/tests/test_jquantstats/test_local.py b/tests/test_jquantstats/test_local.py
index 76359db1..cbaaae8c 100644
--- a/tests/test_jquantstats/test_local.py
+++ b/tests/test_jquantstats/test_local.py
@@ -10,6 +10,9 @@
 from datetime import date, timedelta
 
 import pytest
+
+pytest.importorskip("fastapi", reason="fastapi not installed (pip install jquantstats[api])")
+
 from starlette.testclient import TestClient
 
 from api.app import app
diff --git a/uv.lock b/uv.lock
index b89379cd..47e97671 100644
--- a/uv.lock
+++ b/uv.lock
@@ -837,7 +837,7 @@ requires-dist = [
     { name = "narwhals", specifier = ">=2.0.0" },
     { name = "numpy", specifier = ">=2.0.0" },
     { name = "plotly", specifier = ">=6.0.0" },
-    { name = "polars", specifier = ">=1.18.0" },
+    { name = "polars", specifier = ">=1.35.2" },
     { name = "python-multipart", marker = "extra == 'web'", specifier = ">=0.0.12" },
     { name = "scipy", specifier = ">=1.14.1" },
     { name = "uvicorn", marker = "extra == 'web'", specifier = ">=0.32.0" },