Add truncated fragment frames to malformed sequences

README.md

@@ -425,7 +425,7 @@ The concatenated `data` from all fragments yields the original message's payload
 
 The [ignore rules](#communication) also apply to fragmented messages. If the receiver does not implement `orig_type`, it MAY discard each fragment's `data` instead of allocating a reassembly buffer. It MUST still authenticate every Noise transport message, track the fragment sequence, and enforce the malformed-sequence rules below. The last fragment clears the sequence state. The discarded message is not dispatched.
 
-**Malformed sequences** are protocol errors; the receiver MUST close the connection. They are: a first fragment received while a fragmented message is in flight, a non-first fragment received with none in flight, a non-fragment binary message received while a fragmented message is in flight, a nonzero reserved flag bit, and an `orig_type` of `1`.
+**Malformed sequences** are protocol errors; the receiver MUST close the connection. They are: a first fragment received while a fragmented message is in flight, a non-first fragment received with none in flight, a non-fragment binary message received while a fragmented message is in flight, a nonzero reserved flag bit, an `orig_type` of `1`, a fragment missing its `flags` byte, and a first fragment missing its `orig_type` byte.
 
 ## Clock Synchronization
 

messaging.md

@@ -109,7 +109,7 @@ The concatenated `data` from all fragments yields the original message's payload
 
 The [ignore rules](#communication) also apply to fragmented messages. If the receiver does not implement `orig_type`, it MAY discard each fragment's `data` instead of allocating a reassembly buffer. It MUST still authenticate every Noise transport message, track the fragment sequence, and enforce the malformed-sequence rules below. The last fragment clears the sequence state. The discarded message is not dispatched.
 
-**Malformed sequences** are protocol errors; the receiver MUST close the connection. They are: a first fragment received while a fragmented message is in flight, a non-first fragment received with none in flight, a non-fragment binary message received while a fragmented message is in flight, a nonzero reserved flag bit, and an `orig_type` of `1`.
+**Malformed sequences** are protocol errors; the receiver MUST close the connection. They are: a first fragment received while a fragmented message is in flight, a non-first fragment received with none in flight, a non-fragment binary message received while a fragmented message is in flight, a nonzero reserved flag bit, an `orig_type` of `1`, a fragment missing its `flags` byte, and a first fragment missing its `orig_type` byte.
 
 ## Clock Synchronization