diff --git a/prod/clean_arch/dita_v2/rust_backend.py b/prod/clean_arch/dita_v2/rust_backend.py
index 5ed721e..4985e98 100644
--- a/prod/clean_arch/dita_v2/rust_backend.py
+++ b/prod/clean_arch/dita_v2/rust_backend.py
@@ -437,9 +437,25 @@ def _first_invalid_intent_field(intent: KernelIntent) -> Optional[tuple[str, flo
     return None
 
 
+def _utc_isoformat(ts: Any) -> str:
+    """Return an RFC3339 timestamp string with UTC offset (+00:00).
+
+    Rust's chrono::DateTime<Utc> serde deserializer requires a timezone-aware
+    string. A naive datetime (no tzinfo) produces e.g. '2026-06-04T14:26:55.098914'
+    (26 chars) which chrono rejects with 'premature end of input at column 41'
+    (14-char JSON key prefix + 26-char value + closing quote = column 41).
+    """
+    from datetime import timezone as _tz
+    if hasattr(ts, "tzinfo"):
+        if ts.tzinfo is None:
+            ts = ts.replace(tzinfo=_tz.utc)
+        return ts.isoformat()
+    return str(ts)
+
+
 def _intent_to_payload(intent: KernelIntent) -> Dict[str, Any]:
     return {
-        "timestamp": intent.timestamp.isoformat() if hasattr(intent.timestamp, "isoformat") else str(intent.timestamp),
+        "timestamp": _utc_isoformat(intent.timestamp),
         "intent_id": intent.intent_id,
         "trade_id": intent.trade_id,
         "slot_id": intent.slot_id,