fix: clear session-scoped model overrides during session reset

gateway/run.py

@@ -3264,6 +3264,10 @@ class GatewayRunner:
         except Exception:
             pass
 
+        # Clear any session-scoped model override so the next agent picks up
+        # the configured default instead of the previously switched model.
+        self._session_model_overrides.pop(session_key, None)
+
         # Reset the session
         new_entry = self.session_store.reset_session(session_key)
 

tests/gateway/test_session_model_reset.py

@@ -0,0 +1,126 @@
+"""Tests that /new (and its /reset alias) clears the session-scoped model override."""
+from datetime import datetime
+from types import SimpleNamespace
+from unittest.mock import AsyncMock, MagicMock
+
+import pytest
+
+from gateway.config import GatewayConfig, Platform, PlatformConfig
+from gateway.platforms.base import MessageEvent
+from gateway.session import SessionEntry, SessionSource, build_session_key
+
+
+def _make_source() -> SessionSource:
+    return SessionSource(
+        platform=Platform.TELEGRAM,
+        user_id="u1",
+        chat_id="c1",
+        user_name="tester",
+        chat_type="dm",
+    )
+
+
+def _make_event(text: str) -> MessageEvent:
+    return MessageEvent(text=text, source=_make_source(), message_id="m1")
+
+
+def _make_runner():
+    from gateway.run import GatewayRunner
+
+    runner = object.__new__(GatewayRunner)
+    runner.config = GatewayConfig(
+        platforms={Platform.TELEGRAM: PlatformConfig(enabled=True, token="***")}
+    )
+    adapter = MagicMock()
+    adapter.send = AsyncMock()
+    runner.adapters = {Platform.TELEGRAM: adapter}
+    runner._voice_mode = {}
+    runner.hooks = SimpleNamespace(emit=AsyncMock(), loaded_hooks=False)
+    runner._session_model_overrides = {}
+    runner._pending_model_notes = {}
+    runner._background_tasks = set()
+
+    session_key = build_session_key(_make_source())
+    session_entry = SessionEntry(
+        session_key=session_key,
+        session_id="sess-1",
+        created_at=datetime.now(),
+        updated_at=datetime.now(),
+        platform=Platform.TELEGRAM,
+        chat_type="dm",
+    )
+    runner.session_store = MagicMock()
+    runner.session_store.get_or_create_session.return_value = session_entry
+    runner.session_store.reset_session.return_value = session_entry
+    runner.session_store._entries = {session_key: session_entry}
+    runner.session_store._generate_session_key.return_value = session_key
+    runner._running_agents = {}
+    runner._pending_messages = {}
+    runner._pending_approvals = {}
+    runner._session_db = None
+    runner._agent_cache_lock = None  # disables _evict_cached_agent lock path
+    runner._is_user_authorized = lambda _source: True
+    runner._format_session_info = lambda: ""
+
+    return runner
+
+
+@pytest.mark.asyncio
+async def test_new_command_clears_session_model_override():
+    """/new must remove the session-scoped model override for that session."""
+    runner = _make_runner()
+    session_key = build_session_key(_make_source())
+
+    # Simulate a prior /model switch stored as a session override
+    runner._session_model_overrides[session_key] = {
+        "model": "gpt-4o",
+        "provider": "openai",
+        "api_key": "sk-test",
+        "base_url": "",
+        "api_mode": "openai",
+    }
+
+    await runner._handle_reset_command(_make_event("/new"))
+
+    assert session_key not in runner._session_model_overrides
+
+
+@pytest.mark.asyncio
+async def test_new_command_no_override_is_noop():
+    """/new with no prior model override must not raise."""
+    runner = _make_runner()
+    session_key = build_session_key(_make_source())
+
+    assert session_key not in runner._session_model_overrides
+
+    await runner._handle_reset_command(_make_event("/new"))
+
+    assert session_key not in runner._session_model_overrides
+
+
+@pytest.mark.asyncio
+async def test_new_command_only_clears_own_session():
+    """/new must only clear the override for the session that triggered it."""
+    runner = _make_runner()
+    session_key = build_session_key(_make_source())
+    other_key = "other_session_key"
+
+    runner._session_model_overrides[session_key] = {
+        "model": "gpt-4o",
+        "provider": "openai",
+        "api_key": "sk-test",
+        "base_url": "",
+        "api_mode": "openai",
+    }
+    runner._session_model_overrides[other_key] = {
+        "model": "claude-sonnet-4-6",
+        "provider": "anthropic",
+        "api_key": "sk-ant-test",
+        "base_url": "",
+        "api_mode": "anthropic",
+    }
+
+    await runner._handle_reset_command(_make_event("/new"))
+
+    assert session_key not in runner._session_model_overrides
+    assert other_key in runner._session_model_overrides