Render plain Responses completions

When Responses mode accepts a plain-text final answer, reuse the active generating log item as a finished response entry so the WebUI does not remain on the Calling LLM step.

Skip normal tool JSON and existing live response-tool logs, and cover the fallback with focused regression tests.

extensions/python/_functions/AGENTS.md

@@ -15,6 +15,7 @@
 - Do not flatten nested qualname paths into retired legacy folder names.
 - Extension functions must match the implicit hook's supplied arguments.
 - Preserve ordering prefixes where exception handling, watchdog registration, or cleanup depends on them.
+- Hooks that mirror persisted AI responses into UI logs must reuse existing stream log items and avoid duplicating live response-tool logs.
 
 ## Work Guidance
 

extensions/python/_functions/agent/Agent/hist_add_ai_response/end/_10_log_plain_responses.py

@@ -0,0 +1,44 @@
+from typing import Any
+
+from helpers import extract_tools
+from helpers.extension import Extension
+
+
+class LogPlainResponses(Extension):
+    def execute(self, data: dict[str, Any] | None = None, **kwargs):
+        if not self.agent or not isinstance(data, dict):
+            return
+
+        call_kwargs = data.get("kwargs")
+        if not isinstance(call_kwargs, dict):
+            call_kwargs = {}
+
+        llm_result = call_kwargs.get("llm_result")
+        if getattr(llm_result, "mode", "") != "responses":
+            return
+
+        message = call_kwargs.get("message")
+        call_args = data.get("args")
+        if message is None and isinstance(call_args, tuple) and len(call_args) > 1:
+            message = call_args[1]
+        if not isinstance(message, str) or not message:
+            return
+        if extract_tools.json_parse_dirty(message) is not None:
+            return
+
+        params = getattr(getattr(self.agent, "loop_data", None), "params_temporary", None)
+        if not isinstance(params, dict) or "log_item_response" in params:
+            return
+
+        log_item = params.get("log_item_generating")
+        if log_item is None:
+            return
+
+        params["log_item_response"] = log_item
+        log_item.update(
+            type="response",
+            heading="",
+            content=message,
+            finished=True,
+            update_progress="none",
+        )

tests/test_plain_response_logging.py

@@ -0,0 +1,66 @@
+from types import SimpleNamespace
+
+from helpers.log import Log
+from extensions.python._functions.agent.Agent.hist_add_ai_response.end._10_log_plain_responses import (
+    LogPlainResponses,
+)
+
+
+def _agent_with_generating_log():
+    log = Log()
+    item = log.log(type="agent", heading="A0: Calling LLM...", id="msg-1")
+    agent = SimpleNamespace(
+        loop_data=SimpleNamespace(params_temporary={"log_item_generating": item})
+    )
+    return agent, item
+
+
+def test_responses_plain_text_completion_finishes_generating_log_as_response():
+    agent, item = _agent_with_generating_log()
+    data = {
+        "args": (agent, "Plain final answer."),
+        "kwargs": {"id": "msg-1", "llm_result": SimpleNamespace(mode="responses")},
+    }
+
+    LogPlainResponses(agent=agent).execute(data=data)
+
+    assert item.type == "response"
+    assert item.heading == ""
+    assert item.content == "Plain final answer."
+    assert item.update_progress == "none"
+    assert item.kvps["finished"] is True
+    assert agent.loop_data.params_temporary["log_item_response"] is item
+
+
+def test_responses_tool_json_keeps_generating_log_as_agent_step():
+    agent, item = _agent_with_generating_log()
+    data = {
+        "args": (
+            agent,
+            '{"tool_name":"search_engine","tool_args":{"query":"today news"}}',
+        ),
+        "kwargs": {"id": "msg-1", "llm_result": SimpleNamespace(mode="responses")},
+    }
+
+    LogPlainResponses(agent=agent).execute(data=data)
+
+    assert item.type == "agent"
+    assert item.heading == "A0: Calling LLM..."
+    assert item.content == ""
+    assert "log_item_response" not in agent.loop_data.params_temporary
+
+
+def test_responses_plain_text_completion_does_not_replace_live_response_log():
+    agent, item = _agent_with_generating_log()
+    live_response = Log().log(type="response", content="Already live")
+    agent.loop_data.params_temporary["log_item_response"] = live_response
+    data = {
+        "args": (agent, "Plain final answer."),
+        "kwargs": {"id": "msg-1", "llm_result": SimpleNamespace(mode="responses")},
+    }
+
+    LogPlainResponses(agent=agent).execute(data=data)
+
+    assert item.type == "agent"
+    assert item.content == ""
+    assert agent.loop_data.params_temporary["log_item_response"] is live_response