diff --git a/nslsii/sync_experiment/sync_experiment.py b/nslsii/sync_experiment/sync_experiment.py
index 844f127..f9c88b6 100644
--- a/nslsii/sync_experiment/sync_experiment.py
+++ b/nslsii/sync_experiment/sync_experiment.py
@@ -24,6 +24,17 @@ def get_current_cycle() -> str:
     return cycle_response.json()["cycle"]
 
 
+def is_commissioning_proposal(proposal_number, beamline) -> bool:
+    """True if proposal_number is registered as a commissioning proposal; else False."""
+    commissioning_proposals_response = nslsii_api_client.get(
+        f"/v1/proposals/commissioning?beamline={beamline}"
+    ).raise_for_status()
+    commissioning_proposals = commissioning_proposals_response.json()[
+        "commissioning_proposals"
+    ]
+    return proposal_number in commissioning_proposals
+
+
 def validate_proposal(data_session_value, beamline) -> Dict[str, Any]:
 
     proposal_data = {}
@@ -38,6 +49,7 @@ def validate_proposal(data_session_value, beamline) -> Dict[str, Any]:
     try:
         current_cycle = get_current_cycle()
         proposal_number = data_session_match.group("proposal_number")
+        proposal_commissioning = is_commissioning_proposal(proposal_number, beamline)
         proposal_response = nslsii_api_client.get(
             f"/v1/proposal/{proposal_number}"
         ).raise_for_status()
@@ -49,7 +61,10 @@ def validate_proposal(data_session_value, beamline) -> Dict[str, Any]:
                 f"{proposal_data}"
             )
         else:
-            if current_cycle not in proposal_data["cycles"]:
+            if (
+                not proposal_commissioning
+                and current_cycle not in proposal_data["cycles"]
+            ):
                 raise ValueError(
                     f"Proposal {data_session_value} is not valid in the current NSLS2 cycle ({current_cycle})."
                 )
@@ -154,7 +169,11 @@ def sync_experiment(proposal_number, beamline, verbose=False, prefix=""):
         md["data_session"] = new_data_session
         md["username"] = username
         md["start_datetime"] = datetime.now().isoformat()
-        md["cycle"] = get_current_cycle()
+        md["cycle"] = (
+            "commissioning"
+            if is_commissioning_proposal(str(proposal_number), beamline)
+            else get_current_cycle()
+        )
         md["proposal"] = {
             "proposal_id": proposal_data.get("proposal_id"),
             "title": proposal_data.get("title"),