not mandatory to have the command metadata field set

src/deltaglider/core/models.py

@@ -2,11 +2,13 @@
 
 from dataclasses import dataclass
 from datetime import datetime
+import logging
 
 # Metadata key prefix for DeltaGlider
 # AWS S3 automatically adds 'x-amz-meta-' prefix, so our keys become 'x-amz-meta-dg-*'
 METADATA_PREFIX = "dg-"
 
+logger = logging.getLogger(__name__)
 
 @dataclass(frozen=True)
 class DeltaSpace:
@@ -96,6 +98,12 @@ class DeltaMeta:
     @classmethod
     def from_dict(cls, data: dict[str, str]) -> "DeltaMeta":
         """Create from S3 metadata dict with DeltaGlider namespace prefix."""
+        delta_cmd_key = f"{METADATA_PREFIX}delta-cmd"
+        delta_cmd_value = data.get(delta_cmd_key)
+        if delta_cmd_value is None:
+            object_name = data.get(f"{METADATA_PREFIX}original-name", "<unknown>")
+            logger.warning("Delta metadata missing %s for %s; using empty command", delta_cmd_key, object_name)
+            delta_cmd_value = ""
         return cls(
             tool=data[f"{METADATA_PREFIX}tool"],
             original_name=data[f"{METADATA_PREFIX}original-name"],
@@ -105,7 +113,7 @@ class DeltaMeta:
             ref_key=data[f"{METADATA_PREFIX}ref-key"],
             ref_sha256=data[f"{METADATA_PREFIX}ref-sha256"],
             delta_size=int(data[f"{METADATA_PREFIX}delta-size"]),
-            delta_cmd=data[f"{METADATA_PREFIX}delta-cmd"],
+            delta_cmd=delta_cmd_value,
             note=data.get(f"{METADATA_PREFIX}note"),
         )