fix: prevent mixed-version pushy feedback

Assistant: codex
Assistant-Model: gpt-5.6-sol
Assistant-Session: 01a03397-4d51-7fd1-8ff2-946eb22ea2bc

src/tamq/broker.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import re
 from dataclasses import dataclass
 
 from .routing import RoutedMessage, parse_address_line
@@ -7,6 +8,12 @@ from .store import Store
 from .registry import RegistryError, validate_targets
 
 
+LEGACY_DELIVERY_SUFFIX = re.compile(
+    r"\s+\[(m-[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12})\]$",
+    re.IGNORECASE,
+)
+
+
 @dataclass(frozen=True)
 class BrokerIdentity:
     endpoint_id: str
@@ -24,6 +31,15 @@ class InputBroker:
         routed = parse_address_line(line)
         if routed is None:
             return None
+        receipt = LEGACY_DELIVERY_SUFFIX.search(routed.body)
+        if line.startswith("#") and receipt:
+            prior = self.store.message(receipt.group(1))
+            if (
+                prior is not None
+                and prior["sender_repo"] == routed.target_repo
+                and prior["target_repo"] == self.identity.source_repo
+            ):
+                return None
         try:
             validate_targets([routed.target_repo])
         except RegistryError: