fix(codex): reset the streamed-text buffer at each completed agentMessage

codex app-server emits commentary deltas + completed, then final deltas +
completed. The delta buffer accumulated "commentary + final", so the completed
final no longer prefix-matched its own deltas, was delivered with
already_streamed=False and the gateway posted a second copy next to the
streamed message (#74248 boundary 2). Drop the buffer once a completed
agentMessage has been compared against its own deltas.

agent/codex_runtime.py

@@ -337,6 +337,11 @@ def make_codex_app_server_event_bridge(agent) -> Callable[[dict], None]:
         if isinstance(text, str) and text.strip() and getattr(agent, "show_commentary", True):
             agent_cb("_emit_interim_assistant_message", "_emit_interim_assistant_message raised",
                      args=({"role": "assistant", "content": text},))
+        # Each agentMessage item is its own delivered message: the completed item was just compared
+        # against ITS deltas, so drop them before the next item's deltas arrive. Otherwise the buffer
+        # holds "commentary + final", the final agentMessage no longer prefix-matches, and it is
+        # re-delivered with already_streamed=False as a second copy (#74248 boundary 2).
+        agent._current_streamed_assistant_text = ""
 
     def _on_item(params: dict, completed: bool) -> None:
         item = params.get("item")

tests/agent/test_run_agent_codex_responses.py

@@ -1997,6 +1997,31 @@ def test_interim_commentary_is_not_marked_already_streamed_without_callbacks(mon
     }
 
 
+def test_app_server_bridge_commentary_then_final_agent_messages_are_each_already_streamed(monkeypatch):
+    """#74248 boundary 2: codex app-server emits commentary deltas + completed, then final deltas +
+    completed. The completed final must compare against ITS OWN deltas, not "commentary + final", or
+    it is re-delivered with already_streamed=False and the gateway posts a second copy."""
+    from agent.codex_runtime import make_codex_app_server_event_bridge
+
+    agent = _build_agent(monkeypatch)
+    agent.stream_delta_callback = lambda text: None
+    deliveries = []
+    agent.interim_assistant_callback = lambda text, *, already_streamed=False: deliveries.append(
+        (text, already_streamed)
+    )
+    on_event = make_codex_app_server_event_bridge(agent)
+
+    def _agent_message(item_id, text, phase):
+        on_event({"method": "item/agentMessage/delta", "params": {"itemId": item_id, "delta": text}})
+        on_event({"method": "item/completed", "params": {
+            "item": {"id": item_id, "type": "agentMessage", "text": text, "phase": phase}}})
+
+    _agent_message("m1", "Checking the config.", "commentary")
+    _agent_message("m2", "Native compaction is active.", "final_answer")
+
+    assert deliveries == [("Checking the config.", True), ("Native compaction is active.", True)]
+    assert agent._current_streamed_assistant_text == ""
+
 
 
 def test_interim_content_was_streamed_matches_prefix_not_exact(monkeypatch):