From 75b1b43ec19f156070aa297e7ebbcbbb97220f4f Mon Sep 17 00:00:00 2001
From: KoNit-K <124019182+KoNit-K@users.noreply.github.com>
Date: Wed, 9 Sep 2026 17:20:58 +0800
Subject: [PATCH] fix(tui-gateway): reject sessionless config.set model with
 4001

Sessionless model switches (including legacy --global) could persist
profile defaults before session.create; fail closed unless --once.

Co-authored-by: Cursor <cursoragent@cursor.com>
(cherry picked from commit 1c4a29757bbde1304404f26b45b6becb841c069f)
---
 tests/test_tui_gateway_server.py  | 55 +++++++++++++++++++++++++++++++
 tui_gateway/methods_config_set.py |  8 ++++-
 2 files changed, 62 insertions(+), 1 deletion(-)

diff --git a/tests/test_tui_gateway_server.py b/tests/test_tui_gateway_server.py
index 4a15d7b257..54e29465fb 100644
--- a/tests/test_tui_gateway_server.py
+++ b/tests/test_tui_gateway_server.py
@@ -10316,6 +10316,61 @@ def test_config_set_model_once_requires_live_session(monkeypatch):
     assert "/model --once requires a live session" in resp["error"]["message"]
 
 
+def test_config_set_model_sessionless_rejected(monkeypatch):
+    """Sessionless config.set model must 4001 before _apply_model_switch.
+
+    Missing session_id and a stale session_id miss both take the sessionless
+    branch; unscoped values and legacy --global must be rejected the same way
+    so a Desktop client cannot persist model.default before session.create.
+    """
+    called = {"n": 0}
+
+    def boom(*a, **k):
+        called["n"] += 1
+        raise AssertionError("_apply_model_switch must not run")
+
+    monkeypatch.setattr(server, "_apply_model_switch", boom)
+    for value in ["some-model", "some-model --provider openai-codex --global"]:
+        resp = server.handle_request({
+            "id": "1", "method": "config.set",
+            "params": {"key": "model", "value": value},
+        })
+        assert resp["error"]["code"] == 4001
+        assert called["n"] == 0
+
+    resp = server.handle_request({
+        "id": "1", "method": "config.set",
+        "params": {"session_id": "missing-sid", "key": "model", "value": "some-model --global"},
+    })
+    assert resp["error"]["code"] == 4001
+    assert called["n"] == 0
+
+
+def test_config_set_model_live_session_still_applies_switch(monkeypatch):
+    """CONTROL: a live session still reaches _apply_model_switch, including --global."""
+    called = {"raw": []}
+
+    def fake_apply(sid, session, raw, **_kwargs):
+        called["raw"].append(raw)
+        return {"value": "some-model", "warning": "", "scope": "global"}
+
+    server._sessions["sid"] = _session()
+    monkeypatch.setattr(server, "_apply_model_switch", fake_apply)
+    try:
+        resp = server.handle_request({
+            "id": "1", "method": "config.set",
+            "params": {
+                "session_id": "sid",
+                "key": "model",
+                "value": "some-model --provider openai-codex --global",
+            },
+        })
+        assert "error" not in resp
+        assert called["raw"] == ["some-model --provider openai-codex --global"]
+    finally:
+        server._sessions.pop("sid", None)
+
+
 def test_config_set_model_session_switch_clears_pending_once_restore(monkeypatch):
     class Agent:
         model = "temp/model"
diff --git a/tui_gateway/methods_config_set.py b/tui_gateway/methods_config_set.py
index cd16baaed3..cd749a7353 100644
--- a/tui_gateway/methods_config_set.py
+++ b/tui_gateway/methods_config_set.py
@@ -140,7 +140,13 @@ def _set_model(rid, params, key, value, session):
             with _session_profile_runtime_scope(session):
                 _persist_live_session_runtime(session)
     else:
-        result = _apply_model_switch("", {"agent": None}, value, confirm_expensive_model=confirmed)
+        # --once keeps its specific 5001; other sessionless model sets 4001 so
+        # --global cannot persist profile defaults before session.create.
+        from hermes_cli.model_switch import parse_model_switch_args
+        if parse_model_switch_args(str(value)).is_once:
+            result = _apply_model_switch("", {"agent": None}, value, confirm_expensive_model=confirmed)
+        else:
+            return _err(rid, 4001, "config.set model requires a live session")
     return _kv(rid, key, result["value"], warning=result["warning"],
                confirm_required=result.get("confirm_required", False),
                confirm_message=result.get("confirm_message", ""), scope=result.get("scope", "session"))