From 39d8da2697428501b2157a327ea752fa96325fe5 Mon Sep 17 00:00:00 2001
From: ciregenz <ciregenz@berkeley.edu>
Date: Wed, 19 Aug 2026 11:41:02 -0700
Subject: [PATCH] [eric] agents: a vanishing quit (nothing persisted) on a
 session that already silent-quit is claimed and compacted; the poke-storm
 hole the one-for-one repro exposed (ENG-354)

---
 backend/apps/agents/manager/run/empty_finish.py |  6 +++++-
 backend/tests/test_empty_finish.py              | 13 +++++++++++++
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/backend/apps/agents/manager/run/empty_finish.py b/backend/apps/agents/manager/run/empty_finish.py
index fc79cbf6..521fb672 100644
--- a/backend/apps/agents/manager/run/empty_finish.py
+++ b/backend/apps/agents/manager/run/empty_finish.py
@@ -157,7 +157,11 @@ def turn_finished_empty(session: AgentSession) -> bool:
             p_last_call_name = p_tool_name_of(m)
             return not any(marker in p_last_call_name for marker in P_ANSWER_TOOL_MARKERS)
         if role in ("user", "system"):
-            return False
+            # A user-message tail normally means a bare prompt (never claimed). But when the model
+            # QUIT so hard it persisted nothing at all, and this session has already silent-quit
+            # before, that vanishing act IS the quit repeating (Haik's poke storms: "continue" ->
+            # instant thinking-only end_turn -> nothing persisted -> detector shrugged).
+            return role == "user" and getattr(session, "empty_finish_total", 0) >= 1
     return False
 
 
diff --git a/backend/tests/test_empty_finish.py b/backend/tests/test_empty_finish.py
index 4339ddcd..aa90bf9d 100644
--- a/backend/tests/test_empty_finish.py
+++ b/backend/tests/test_empty_finish.py
@@ -202,3 +202,16 @@ def test_drill_seam_disables_compaction(monkeypatch):
     s.tokens["input"] = 190_000
     assert maybe_nudge_empty_finish(s, "sid-seam") is True
     assert s.compacted_through_msg_id is None
+
+
+def test_vanishing_quit_on_repeat_session_is_claimed():
+    """Haik's poke storm: 'continue' -> instant thinking-only quit -> NOTHING persisted. A session
+    that already silent-quit must claim that vanishing act; a truly bare first prompt stays unclaimed."""
+    from backend.apps.agents.manager.run.empty_finish import turn_finished_empty
+    s = p_session(("user", "task"),
+                  ("tool_call", {"tool": "Read", "input": {}}),
+                  ("tool_result", {"text": "x"}),
+                  ("user", "you stopped. continue."))
+    assert turn_finished_empty(s) is False, "first-time session: user tail stays unclaimed"
+    s.empty_finish_total = 1
+    assert turn_finished_empty(s) is True, "repeat session: the vanishing quit is claimed"