fix(gateway): preserve queued follow-up transcript history

Keep the outer history_offset when _run_agent drains queued follow-ups recursively so transcript persistence includes every queued turn in the chain instead of only the last one.

gateway/run.py

@@ -1139,6 +1139,38 @@ def _should_clear_resume_pending_after_turn(agent_result: dict) -> bool:
     return True
 
 
+def _preserve_queued_followup_history_offset(
+    current_result: dict,
+    followup_result: dict,
+) -> dict:
+    """Carry the outer history offset through queued follow-up drains.
+
+    ``_process_message_background()`` persists transcript rows only once, after the
+    entire in-band queued-follow-up chain returns.  Each recursive ``_run_agent()``
+    call advances ``history_offset`` to the history it received, so without
+    correction the outermost persistence step sees only the *last* queued turn as
+    "new" and silently drops earlier turns from the same drain chain.
+
+    Preserve the earliest (outermost) history offset so the final transcript slice
+    still includes every queued turn that ran during the chain.
+    """
+    if not isinstance(followup_result, dict):
+        return followup_result
+    if not isinstance(current_result, dict):
+        return followup_result
+
+    current_offset = current_result.get("history_offset")
+    followup_offset = followup_result.get("history_offset")
+    if not isinstance(current_offset, int):
+        return followup_result
+    if isinstance(followup_offset, int) and followup_offset <= current_offset:
+        return followup_result
+
+    merged = dict(followup_result)
+    merged["history_offset"] = current_offset
+    return merged
+
+
 class GatewayRunner:
     """
     Main gateway controller.
@@ -16042,7 +16074,7 @@ class GatewayRunner:
                     except Exception:
                         pass
 
-                return await self._run_agent(
+                followup_result = await self._run_agent(
                     message=next_message,
                     context_prompt=context_prompt,
                     history=updated_history,
@@ -16054,6 +16086,7 @@ class GatewayRunner:
                     event_message_id=next_message_id,
                     channel_prompt=next_channel_prompt,
                 )
+                return _preserve_queued_followup_history_offset(result, followup_result)
         finally:
             # Stop progress sender, interrupt monitor, and notification task
             if progress_task: