From c2ee5039ee822806dbbc7a64c945d4d999f217f2 Mon Sep 17 00:00:00 2001
From: TheEpTic <nexus@eptic.me>
Date: Mon, 27 Jul 2026 01:04:36 +0100
Subject: [PATCH] fix(gateway): preserve media dedup after streamed replies

---
 gateway/run.py                                |  2 +-
 .../test_42039_duplicate_user_message.py      | 48 +++++++++++++++++++
 2 files changed, 49 insertions(+), 1 deletion(-)

diff --git a/gateway/run.py b/gateway/run.py
index e78b9de77dc2..d06512c043a0 100644
--- a/gateway/run.py
+++ b/gateway/run.py
@@ -14710,7 +14710,7 @@ class GatewayRunner(GatewayAuthorizationMixin, GatewayKanbanWatchersMixin, Gatew
                     if _media_adapter:
                         await self._deliver_media_from_response(
                             response, event, _media_adapter,
-                            history_media_paths=_history_media_paths,
+                            history_media_paths=_collect_history_media_paths(history),
                         )
                 # Streaming already delivered the body text, but the footer was
                 # intentionally held back (see the `not already_sent` gate above).
diff --git a/tests/gateway/test_42039_duplicate_user_message.py b/tests/gateway/test_42039_duplicate_user_message.py
index 88f8b8961e97..129b1ce9266c 100644
--- a/tests/gateway/test_42039_duplicate_user_message.py
+++ b/tests/gateway/test_42039_duplicate_user_message.py
@@ -212,6 +212,54 @@ async def test_not_new_messages_skip_db_when_agent_has_session_db(
     )
 
 
+# ── Post-stream MEDIA delivery keeps prior-turn deduplication ──────────
+
+
+@pytest.mark.asyncio
+async def test_streamed_response_receives_prior_turn_media_paths(
+    monkeypatch, tmp_path
+):
+    """An ordinary streamed reply completes the post-stream delivery branch.
+
+    The history-derived dedup set is part of that branch's contract, rather
+    than an optional best-effort hint: passing an undefined local crashes the
+    entire reply, while passing an empty set reintroduces duplicate MEDIA
+    attachments on later streamed responses.
+    """
+    runner = _bootstrap(monkeypatch, tmp_path)
+    prior_path = "/tmp/already-delivered.png"
+    runner.session_store.load_transcript.return_value = [
+        {"role": "assistant", "content": f"MEDIA:{prior_path}"},
+    ]
+    runner.adapters = {Platform.TELEGRAM: MagicMock()}
+    runner._deliver_media_from_response = AsyncMock()
+    runner._run_agent = AsyncMock(
+        return_value={
+            "final_response": "the streamed reply completed normally",
+            "messages": [
+                {"role": "assistant", "content": f"MEDIA:{prior_path}"},
+                {"role": "user", "content": "what is my status?"},
+                {"role": "assistant", "content": "the streamed reply completed normally"},
+            ],
+            "tools": [],
+            "history_offset": 1,
+            "last_prompt_tokens": 0,
+            "already_sent": True,
+            "failed": False,
+        }
+    )
+
+    response = await runner._handle_message_with_agent(
+        _event(), _source(), "agent:main:telegram:group:-1001:12345", 1
+    )
+
+    assert response is None
+    runner._deliver_media_from_response.assert_awaited_once()
+    assert runner._deliver_media_from_response.await_args.kwargs[
+        "history_media_paths"
+    ] == {prior_path}
+
+
 # ── Test 4: normal path (new_messages found) uses skip_db=True ────────