chore(logging): suppress harmless empty-message-cache warning and drop dead code

* Add a narrow logging.Filter on agent_framework._workflows._agent_executor
  that drops only the 'Running agent with empty message cache' message.
  This warning fires by design in GroupChat orchestration when the orchestrator
  routes back to the same speaker (broadcast cache is empty because
  _broadcast_messages_to_participants excludes the source executor). The
  framework's parent client prepends system instructions before the LLM call,
  so the API request still has content. Other warnings/errors from the same
  logger remain visible.

* Remove three lines of commented-out duplicate callback invocation in
  groupchat_orchestrator._complete_agent_response. The live callback handler
  is in the block directly above; the commented block was refactor debris.

No behavioural change. All 833 tests pass.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: Prachig-Microsoft

src/processor/src/libs/agent_framework/groupchat_orchestrator.py

@@ -1250,10 +1250,6 @@ async def _complete_agent_response(
                     "on_agent_response callback failed (agent=%s)", agent_name
                 )
 
-        # # Invoke callback
-        # if callback:
-        #     await callback(response)
-
     async def _build_groupchat(self) -> Workflow:
         """Build the GroupChat Orchestrator workflow"""
         coordinator = self.agents[self.coordinator_name]

src/processor/src/utils/logging_utils.py

@@ -22,6 +22,29 @@
 from azure.core.exceptions import HttpResponseError
 
 
+class _EmptyMessageCacheFilter(logging.Filter):
+    """Suppress the harmless ``empty message cache`` warning emitted by
+    ``agent_framework._workflows._agent_executor``.
+
+    This warning fires by design in GroupChat orchestration when the orchestrator
+    routes back to the same speaker (its broadcast cache is empty because
+    ``_broadcast_messages_to_participants`` excludes the source executor). The
+    framework's parent client prepends the agent's system instructions before
+    calling the LLM, so the API call still has content. The warning is pure noise.
+
+    The filter is intentionally narrow: it matches only the exact message and
+    leaves every other warning/error from the same logger visible.
+    """
+
+    _MARKER = "Running agent with empty message cache"
+
+    def filter(self, record: logging.LogRecord) -> bool:  # noqa: D401
+        try:
+            return self._MARKER not in record.getMessage()
+        except Exception:
+            return True
+
+
 def configure_application_logging(debug_mode: bool = False):
     """
     Comprehensive logging configuration with third-party suppression.
@@ -120,6 +143,13 @@ def configure_application_logging(debug_mode: bool = False):
     for logger_name in always_warning_loggers:
         logging.getLogger(logger_name).setLevel(logging.WARNING)
 
+    # Suppress only the harmless "Running agent with empty message cache" warning
+    # emitted by agent_framework's GroupChat orchestration. Real warnings/errors
+    # from the same logger are still surfaced.
+    _executor_logger = logging.getLogger("agent_framework._workflows._agent_executor")
+    if not any(isinstance(f, _EmptyMessageCacheFilter) for f in _executor_logger.filters):
+        _executor_logger.addFilter(_EmptyMessageCacheFilter())
+
     # Set environment variables to suppress verbose output at the source
     os.environ.setdefault("HTTPX_LOG_LEVEL", "WARNING")
     os.environ.setdefault("AZURE_CORE_ENABLE_HTTP_LOGGER", "false")