diff --git a/tests/tui_gateway/test_session_hidden_rpc.py b/tests/tui_gateway/test_session_hidden_rpc.py
index a44a5cf455..25a35293e9 100644
--- a/tests/tui_gateway/test_session_hidden_rpc.py
+++ b/tests/tui_gateway/test_session_hidden_rpc.py
@@ -59,6 +59,16 @@ def test_set_hidden_unknown_id_still_errors(db):
     assert envelope.get("error"), envelope
 
 
+def test_set_hidden_stored_id_does_not_log_a_rejection(db, caplog):
+    """The stored-id tier is this method's design, not a stale-runtime-id rejection: a fulfilled hide must
+    not emit the "session-scoped RPC rejected … not in memory" warning that diagnoses vanished messages."""
+    _seed(db, "stored-chat")
+    with caplog.at_level("WARNING", logger=srv.logger.name):
+        envelope = _call("session.set_hidden", {"session_id": "stored-chat", "hidden": True})
+    assert "error" not in envelope, envelope
+    assert not [r for r in caplog.records if "session-scoped RPC rejected" in r.getMessage()]
+
+
 def test_session_list_include_hidden(db):
     _seed(db, "plain-chat")
     _seed(db, "bot-chat")
diff --git a/tui_gateway/methods_session.py b/tui_gateway/methods_session.py
index 729478d9e8..e56bae5cc8 100644
--- a/tui_gateway/methods_session.py
+++ b/tui_gateway/methods_session.py
@@ -1040,7 +1040,10 @@ def _(rid, params: dict) -> dict:
     """Set/clear ``hidden`` (leaves the default list, stays resumable by its owner) on a session + lineage:
     LIVE runtime id first (unpersisted drafts via ``pending_hidden``), then a stored id/key in the profile db."""
     hidden = is_truthy_value(params.get("hidden", True))
-    session, err = _sess_nowait(params, rid)
+    # Quiet live lookup: a stored id that is not in memory is this method's expected second tier, not a
+    # rejection — _sess_nowait would log "session-scoped RPC rejected … not in memory" for a request that is
+    # then fulfilled from the profile db, burying the real stale-runtime-id signal under sweep noise.
+    session = _sessions.get(str(params.get("session_id") or ""))
     with (_profile_db(params, writer=True) if session is None else _session_db(session)) as db:
         if db is None:
             return _db_unavailable_error(rid, code=5007)
@@ -1053,7 +1056,7 @@ def _(rid, params: dict) -> dict:
                 # ``resolve_session_id`` follows key/title aliases like the REST pin/archive path.
                 target = _str_param(params, "session_id")
                 if not (key := db.resolve_session_id(target) if hasattr(db, "resolve_session_id") else target):
-                    return err
+                    return _err(rid, 4001, "session not found")
                 db.set_session_hidden(key, hidden)
             return _ok(rid, {"hidden": hidden, "session_key": key})
         except Exception as e: