diff --git a/backend/apps/agents/manager/session/SessionPersistence.py b/backend/apps/agents/manager/session/SessionPersistence.py
index f2531de8..9809167f 100644
--- a/backend/apps/agents/manager/session/SessionPersistence.py
+++ b/backend/apps/agents/manager/session/SessionPersistence.py
@@ -4,6 +4,7 @@ on boot). Split from SessionLifecycle (which handles ONE session at a time) so e
 one concern. self.sessions resolves across the MRO as before."""
 
 import logging
+import os
 import sys
 
 from typeguard import typechecked
@@ -22,7 +23,15 @@ logger = logging.getLogger(__name__)
 def running_under_test() -> bool:
     """Auto-resume dispatches REAL turns: live credentials, live Bash, in whatever tree the process
     was started from. A test that boots the app lifespan must never do that to the developer's own
-    chats, so this is the one gate that keeps a suite run from becoming an agent run."""
+    chats, so this is the one gate that keeps a suite run from becoming an agent run.
+
+    The env var is the DECLARED signal and conftest sets it. `pytest in sys.modules` is kept only as
+    a belt-and-braces fallback, and deliberately not as the primary: an incidental signal fails in
+    the worst direction, because the day pytest becomes importable in a packaged build every
+    crash-interrupted turn stops resuming and NOTHING says so. Work vanishing quietly is the worst
+    bug this codebase can ship; a suite that loudly refuses to resume is merely annoying."""
+    if os.environ.get("OSW_DISABLE_AUTO_RESUME") == "1":
+        return True
     return "pytest" in sys.modules
 
 
diff --git a/backend/tests/conftest.py b/backend/tests/conftest.py
index cc1cbe36..ec57954a 100644
--- a/backend/tests/conftest.py
+++ b/backend/tests/conftest.py
@@ -33,6 +33,10 @@ def _isolate_browser_state(monkeypatch):
     monkeypatch.setenv("OPENSWARM_BROWSER_METRICS_DIR", metrics_dir)
     monkeypatch.setenv("OPENSWARM_BROWSER_PLAYBOOK_DIR", playbook_dir)
     # The speed levers are default-ON in prod; pin them off for the suite so mocked loop tests keep exact aux-call/turn expectations (same pattern as OPENSWARM_PERSISTENT_CLIENT). The levers are exercised by their own live gates + targeted tests that set the flag explicitly.
+    # DECLARED, not inferred: auto-resume sends real turns with live credentials and live Bash into
+    # whatever tree the suite runs from (ENG-388). The pytest-in-sys.modules fallback still exists,
+    # but a gate that depends on an accident fails silently the day the accident changes.
+    monkeypatch.setenv("OSW_DISABLE_AUTO_RESUME", "1")
     monkeypatch.setenv("OSW_PRESTAGE", "0")
     monkeypatch.setenv("OSW_FASTREAD_HOP", "0")
     monkeypatch.setenv("OSW_PRELUDE_TRIM", "0")
diff --git a/backend/tests/test_no_real_turns_under_test.py b/backend/tests/test_no_real_turns_under_test.py
index 3d085b84..3ce6e17a 100644
--- a/backend/tests/test_no_real_turns_under_test.py
+++ b/backend/tests/test_no_real_turns_under_test.py
@@ -47,3 +47,11 @@ def test_the_gate_is_what_stops_it(monkeypatch):
 
 def test_the_gate_sees_pytest():
     assert p_sp.running_under_test() is True
+
+
+def test_the_declared_signal_works_without_the_accidental_one(monkeypatch):
+    """The env var must stand on its own: the day `pytest in sys.modules` stops being true in some
+    runner, the gate has to keep holding, or crash-resume silently reactivates against real chats."""
+    monkeypatch.setenv("OSW_DISABLE_AUTO_RESUME", "1")
+    monkeypatch.setitem(__import__("sys").modules, "pytest", None)
+    assert p_sp.running_under_test() is True
diff --git a/frontend/src/app/Main.tsx b/frontend/src/app/Main.tsx
index 79dcb934..d396b181 100644
--- a/frontend/src/app/Main.tsx
+++ b/frontend/src/app/Main.tsx
@@ -408,7 +408,19 @@ const DefaultModelGuard: React.FC<{ children: React.ReactNode }> = ({ children }
     const fallback = pickFallbackModel(byProvider);
     if (!fallback) return;
     // A model absent from the catalog is genuinely gone; one merely absent from today's list is a provider we cannot reach this second, and moving the chat off it is never ours to do silently.
-    if (!catalogComplete || knownValues.length === 0) return;
+    // Going quiet here is itself a failure mode: a genuinely retired model then never heals and the
+    // user just gets an error on every send. So when the catalog cannot be vouched for, say so once
+    // for the sessions it would have touched instead of disabling the heal in silence.
+    if (!catalogComplete || knownValues.length === 0) {
+      const p_stranded = Object.values(store.getState().agents.sessions)
+        .filter((s2) => s2.model && !valid.has(s2.model));
+      if (p_stranded.length && !warnedSessionsRef.current.has('catalog-unverified')) {
+        warnedSessionsRef.current.add('catalog-unverified');
+        console.warn(`[models] catalog unverified (complete=${catalogComplete}, known=${knownValues.length}); ` +
+          `${p_stranded.length} session(s) hold a model that is not currently available and will NOT be auto-switched`);
+      }
+      return;
+    }
     const known = new Set(knownValues);
     const target = valid.has(settings.default_model) ? settings.default_model : fallback.value;
     let switched = false;