diff --git a/kobrax_client.py b/kobrax_client.py
index a46a0fd..86cddc2 100644
--- a/kobrax_client.py
+++ b/kobrax_client.py
@@ -144,6 +144,11 @@ class KobraXClient:
 
         # Dedup: last hash per topic suffix to suppress repeated identical messages
         self._last_rx_hash: dict[str, str] = {}
+        # Debug switch (MQTT_RAW_LOG=1): logs every RX message unfiltered on
+        # INFO, including dedup'd duplicates and topics with no registered
+        # callback - for capturing printer behavior the bridge doesn't
+        # normally surface (e.g. reverse-engineering a rejected command).
+        self._raw_log = os.environ.get("MQTT_RAW_LOG", "").strip().lower() in ("1", "true", "yes")
         # Fields that change every tick and should be stripped before dedup-hashing
         _VOLATILE = {"timestamp", "msgid", "progress", "curr_layer",
                      "curr_nozzle_temp", "curr_hotbed_temp",
@@ -422,6 +427,9 @@ class KobraXClient:
     def _dispatch(self, topic: str, payload: dict):
         suffix = "/".join(topic.split("/")[-2:])
 
+        if self._raw_log:
+            log.info("RX [raw] %s  %s", topic, json.dumps(payload, ensure_ascii=False))
+
         # Structured RX log with dedup suppression
         h = self._dedup_hash(suffix, payload)
         is_dup = self._last_rx_hash.get(suffix) == h