fix: prevent infinite loop when sign-off validation rejects finish

When Coordinator repeatedly says finish=true but sign-off validation
fails, the selection_func routed back to Coordinator creating a 100-round
loop. Fix: track consecutive finish rejections and force-terminate after
5 attempts. Also reset counter when Coordinator routes to a participant.

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

Author: Prachig-Microsoft

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

@@ -310,6 +310,12 @@ def __init__(
         # Snapshot of progress_counter at the time we last saw _last_coordinator_selection.
         self._last_coordinator_selection_progress: int = 0
 
+        # Track consecutive finish rejections (sign-off validation failures).
+        # When the Coordinator keeps saying finish=true but sign-offs are
+        # incomplete, prevent infinite loops by force-terminating after a threshold.
+        self._finish_rejection_count: int = 0
+        self._max_finish_rejections: int = 5
+
     def _request_forced_termination(
         self, *, reason: str, termination_type: str
     ) -> None:
@@ -1278,10 +1284,26 @@ async def _complete_agent_response(
                         )
                         is_valid, reason = self._validate_sign_offs(sign_off_conversation)
                         if not is_valid:
+                            self._finish_rejection_count += 1
                             logger.warning(
-                                "Termination rejected for success completion: %s. Workflow continues.",
+                                "Termination rejected for success completion (%d/%d): %s. Workflow continues.",
+                                self._finish_rejection_count,
+                                self._max_finish_rejections,
                                 reason,
                             )
+                            if self._finish_rejection_count >= self._max_finish_rejections:
+                                logger.warning(
+                                    "Max finish rejections reached (%d). Force-terminating.",
+                                    self._finish_rejection_count,
+                                )
+                                self._request_forced_termination(
+                                    reason=(
+                                        f"Coordinator attempted finish {self._finish_rejection_count} times "
+                                        f"but sign-off validation kept failing: {reason}"
+                                    ),
+                                    termination_type="hard_timeout",
+                                )
+                                return
                             # Do NOT set _termination_requested.
                             return
 
@@ -1297,6 +1319,9 @@ async def _complete_agent_response(
                     and selected
                     and selected.lower() != "none"
                 ):
+                    # Non-finish routing: reset finish rejection counter since
+                    # Coordinator is doing productive work (selecting participants).
+                    self._finish_rejection_count = 0
                     # Record invocation time for non-termination coordinator selections
                     self._agent_invoked_at[selected] = completed_at
             except Exception as exc:
@@ -1396,6 +1421,12 @@ def selection_func(state: GroupChatState) -> str:
                         and selected in state.participants
                     ):
                         return selected
+
+                    # Coordinator said finish=true with no valid participant.
+                    # Route back to Coordinator to let the streaming loop's
+                    # termination/force-termination logic handle it.
+                    if manager_response.finish is True:
+                        return coordinator_name
             except Exception:
                 pass