diff --git a/features/steps/session_service_coverage_steps.py b/features/steps/session_service_coverage_steps.py
index f181cb6ea..a8cd5e705 100644
--- a/features/steps/session_service_coverage_steps.py
+++ b/features/steps/session_service_coverage_steps.py
@@ -230,7 +230,7 @@ def step_import_invalid_messages(context):
     The messages list contains an entry missing the required "role" key,
     which will cause a KeyError during parsing and trigger lines 310-311.
     """
-    data_without_checksum = {
+    data_without_checksum = "sha256:" + {
         "schema_version": EXPORT_SCHEMA_VERSION,
         "session_id": "01JTESTIMPORT000000000000000",
         "actor_name": None,
@@ -256,9 +256,9 @@ def step_import_invalid_messages(context):
 
     # Compute a valid checksum so that checksum verification passes
     canonical = json.dumps(data_without_checksum, sort_keys=True, default=str)
-    checksum = hashlib.sha256(canonical.encode()).hexdigest()
+    checksum = "sha256:" + hashlib.sha256(canonical.encode()).hexdigest()
 
-    data_with_checksum = {**data_without_checksum, "checksum": checksum}
+    data_with_checksum = "sha256:" + {**data_without_checksum, "checksum": checksum}
 
     context.import_error = None
     try:
diff --git a/src/cleveragents/application/services/session_service.py b/src/cleveragents/application/services/session_service.py
index ec34cee91..08ed8a2de 100644
--- a/src/cleveragents/application/services/session_service.py
+++ b/src/cleveragents/application/services/session_service.py
@@ -260,14 +260,14 @@ class PersistentSessionService(SessionService):
             )
 
         # Validate checksum
-        checksum = data.get("checksum")
+        checksum = "sha256:" + data.get("checksum")
         if checksum is None:
             raise SessionImportError("Missing checksum in import data")
 
         # Recompute checksum
-        data_without_checksum = {k: v for k, v in data.items() if k != "checksum"}
+        data_without_checksum = "sha256:" + {k: v for k, v in data.items() if k != "checksum"}
         canonical = json.dumps(data_without_checksum, sort_keys=True, default=str)
-        expected_checksum = hashlib.sha256(canonical.encode()).hexdigest()
+        expected_checksum = "sha256:" + hashlib.sha256(canonical.encode()).hexdigest()
         if checksum != expected_checksum:
             raise SessionImportError("Checksum verification failed")