diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index c14c991..37af6ee 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -57,3 +57,27 @@ jobs:
 
       - name: Tests
         run: uv run pytest tests/ -v --cov=agentscore_commerce --cov-report=term-missing
+
+  test:
+    runs-on: blacksmith-2vcpu-ubuntu-2404-arm
+    timeout-minutes: 10
+    strategy:
+      fail-fast: false
+      matrix:
+        python: ["3.11", "3.12", "3.13", "3.14", "3.15"]
+    steps:
+      - uses: useblacksmith/checkout@v1
+
+      - name: Install uv
+        uses: astral-sh/setup-uv@v10.2.0
+        with:
+          version: "0.12.20"
+
+      - name: Set up Python
+        run: uv python install ${{ matrix.python }}
+
+      - name: Install dependencies
+        run: uv sync --frozen --all-extras --python ${{ matrix.python }}
+
+      - name: Tests
+        run: uv run --python ${{ matrix.python }} pytest tests/ -q
diff --git a/agentscore_commerce/checkout_compute_first.py b/agentscore_commerce/checkout_compute_first.py
index 8716cc7..d35cc02 100644
--- a/agentscore_commerce/checkout_compute_first.py
+++ b/agentscore_commerce/checkout_compute_first.py
@@ -33,7 +33,7 @@
 import logging
 import uuid
 from dataclasses import dataclass, field
-from datetime import UTC, datetime, timezone
+from datetime import UTC, datetime
 from decimal import Decimal
 from typing import TYPE_CHECKING, Any
 
@@ -207,7 +207,7 @@ def _decimals_for_unit(unit_price_cents: float) -> int:
 
 
 def _iso_now() -> str:
-    return datetime.now(timezone.utc).isoformat().replace("+00:00", "Z")
+    return datetime.now(UTC).isoformat().replace("+00:00", "Z")
 
 
 def _default_success_body(app_url: str) -> Callable[[SuccessBodyArgs], dict[str, Any]]:
diff --git a/examples/multi_rail_merchant.py b/examples/multi_rail_merchant.py
index 2cf24dd..cca5bcf 100644
--- a/examples/multi_rail_merchant.py
+++ b/examples/multi_rail_merchant.py
@@ -40,7 +40,7 @@
 
 import os
 from dataclasses import asdict
-from datetime import datetime, timezone
+from datetime import UTC, datetime
 from typing import Any
 
 from fastapi import FastAPI, Request
@@ -154,7 +154,7 @@ async def _on_settled(ctx: Any, outcome: SettleOutcome) -> dict[str, Any]:
     success = build_success_next_steps(order_status_url=f"{APP_URL}/orders/{ctx.reference_id}")
     receipt = Receipt(
         id=ctx.reference_id,
-        created_at=datetime.now(timezone.utc).isoformat(),
+        created_at=datetime.now(UTC).isoformat(),
         pricing=ctx.pricing.block,
         product=ProductInfo(name="Regulated Goods Cart"),
         payment_status="completed",
diff --git a/pyproject.toml b/pyproject.toml
index 8544246..b7596fd 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -19,6 +19,11 @@ classifiers = [
     "Intended Audience :: Developers",
     "License :: OSI Approved :: MIT License",
     "Programming Language :: Python :: 3",
+    "Programming Language :: Python :: 3.11",
+    "Programming Language :: Python :: 3.12",
+    "Programming Language :: Python :: 3.13",
+    "Programming Language :: Python :: 3.14",
+    "Programming Language :: Python :: 3.15",
     "Framework :: FastAPI",
     "Framework :: Flask",
     "Framework :: Django",
diff --git a/ruff.toml b/ruff.toml
index 40e2e29..8e52da7 100644
--- a/ruff.toml
+++ b/ruff.toml
@@ -1,4 +1,4 @@
-target-version = "py310"
+target-version = "py311"
 line-length = 120
 
 [lint]