diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
new file mode 100644
index 0000000..3c66f09
--- /dev/null
+++ b/.github/workflows/ci.yaml
@@ -0,0 +1,10 @@
+name: CI
+on:
+  pull_request:
+    branches: [main]
+
+jobs:
+  ci:
+    uses: Sea-Haven-Industries/.github/.github/workflows/ci-python-sam.yaml@main
+    with:
+      source-dirs: "src"
diff --git a/src/handler.py b/src/handler.py
index 738ec4d..6a320f3 100644
--- a/src/handler.py
+++ b/src/handler.py
@@ -14,6 +14,7 @@ logger.setLevel(logging.INFO)
 # US Eastern (handles DST automatically via zoneinfo on Python 3.9+)
 try:
     from zoneinfo import ZoneInfo
+
     EASTERN = ZoneInfo("America/New_York")
 except ImportError:
     EASTERN = timezone(timedelta(hours=-5))
@@ -21,7 +22,9 @@ except ImportError:
 
 def load_schedule() -> dict:
     """Load schedule from config bundled in the Lambda package."""
-    config_path = os.path.join(os.path.dirname(__file__), "..", "config", "schedule.yaml")
+    config_path = os.path.join(
+        os.path.dirname(__file__), "..", "config", "schedule.yaml"
+    )
     with open(config_path) as f:
         return yaml.safe_load(f)
 
@@ -44,7 +47,9 @@ def get_3cx_credentials() -> dict:
 WEEKEND_DAYS = {"Saturday", "Sunday"}
 
 
-def check_dynamodb_override(date_str: str, day_name: str, shift_type: str = "night") -> str | None:
+def check_dynamodb_override(
+    date_str: str, day_name: str, shift_type: str = "night"
+) -> str | None:
     """Check the afterhours-shifts DynamoDB table for a Slack-driven override.
 
     Args:
@@ -72,9 +77,16 @@ def check_dynamodb_override(date_str: str, day_name: str, shift_type: str = "nig
             # Open shift with no pickup — use fallback from DynamoDB config or default 100
             config_resp = table.get_item(Key={"PK": "CONFIG", "SK": "CONFIG"})
             fallback = config_resp.get("Item", {}).get("fallback_extension", "100")
-            logger.info("DynamoDB override for %s (%s): OPEN — using fallback Ext %s", override_sk, shift_type, fallback)
+            logger.info(
+                "DynamoDB override for %s (%s): OPEN — using fallback Ext %s",
+                override_sk,
+                shift_type,
+                fallback,
+            )
             return fallback
-        logger.info("DynamoDB override for %s (%s): Ext %s", override_sk, shift_type, ext)
+        logger.info(
+            "DynamoDB override for %s (%s): Ext %s", override_sk, shift_type, ext
+        )
         return ext
 
     # Check DynamoDB weekly schedule (takes precedence over YAML when SHIFT_TABLE is set)
@@ -83,7 +95,13 @@ def check_dynamodb_override(date_str: str, day_name: str, shift_type: str = "nig
     item = resp.get("Item")
     if item:
         ext = item["extension"]
-        logger.info("DynamoDB weekly schedule for %s (%s, %s): Ext %s", date_str, weekly_sk, shift_type, ext)
+        logger.info(
+            "DynamoDB weekly schedule for %s (%s, %s): Ext %s",
+            date_str,
+            weekly_sk,
+            shift_type,
+            ext,
+        )
         return ext
 
     return None
@@ -126,7 +144,9 @@ def resolve_extension(schedule: dict, now: datetime, shift_type: str = "night")
 
     # YAML config only covers night shifts (legacy)
     if shift_type == "day":
-        logger.info("No DynamoDB entry for %s day shift — using fallback Ext 100", date_str)
+        logger.info(
+            "No DynamoDB entry for %s day shift — using fallback Ext 100", date_str
+        )
         return "100"
 
     # Fall back to YAML config
@@ -140,7 +160,9 @@ def resolve_extension(schedule: dict, now: datetime, shift_type: str = "night")
     if day_name not in weekly:
         raise ValueError(f"No schedule entry for {day_name}")
     ext = str(weekly[day_name])
-    logger.info("Using YAML weekly schedule for %s (%s): Ext %s", date_str, day_name, ext)
+    logger.info(
+        "Using YAML weekly schedule for %s (%s): Ext %s", date_str, day_name, ext
+    )
     return ext
 
 
@@ -158,8 +180,15 @@ def handler(event, context):
     force = event.get("force", False)
     valid_hours = {8, 17} if day_name in WEEKEND_DAYS else {8}
     if not force and current_hour not in valid_hours:
-        logger.info("Current ET hour is %d on %s — skipping (wrong DST rule fired)", current_hour, day_name)
-        return {"skipped": True, "reason": f"ET hour is {current_hour}, not in {valid_hours}"}
+        logger.info(
+            "Current ET hour is %d on %s — skipping (wrong DST rule fired)",
+            current_hour,
+            day_name,
+        )
+        return {
+            "skipped": True,
+            "reason": f"ET hour is {current_hour}, not in {valid_hours}",
+        }
 
     schedule = load_schedule()
     shift_type = determine_shift_type(now)
diff --git a/src/three_cx_client.py b/src/three_cx_client.py
index f6b4996..39c792d 100644
--- a/src/three_cx_client.py
+++ b/src/three_cx_client.py
@@ -16,13 +16,17 @@ class ThreeCXClient:
         """
         self.base_url = f"https://{domain}"
         self.session = requests.Session()
-        self.session.headers.update({
-            "OData-Version": "4.0",
-            "Content-Type": "application/json",
-        })
+        self.session.headers.update(
+            {
+                "OData-Version": "4.0",
+                "Content-Type": "application/json",
+            }
+        )
 
         if auth_mode == "oauth":
-            self._authenticate_oauth(auth_kwargs["client_id"], auth_kwargs["client_secret"])
+            self._authenticate_oauth(
+                auth_kwargs["client_id"], auth_kwargs["client_secret"]
+            )
         else:
             self._authenticate_user(auth_kwargs["username"], auth_kwargs["password"])