fix: validate /model values before saving

tests/test_cli_model_command.py

@@ -0,0 +1,60 @@
+"""Regression tests for the `/model` slash command."""
+
+import os
+import sys
+from unittest.mock import patch
+
+sys.path.insert(0, os.path.join(os.path.dirname(__file__), ".."))
+
+from cli import HermesCLI
+
+
+class TestModelCommand:
+    def _make_cli(self):
+        cli_obj = HermesCLI.__new__(HermesCLI)
+        cli_obj.model = "anthropic/claude-opus-4.6"
+        cli_obj.agent = object()
+        cli_obj.provider = "openrouter"
+        cli_obj.requested_provider = "openrouter"
+        cli_obj.base_url = "https://openrouter.ai/api/v1"
+        cli_obj._explicit_api_key = None
+        cli_obj._explicit_base_url = None
+        return cli_obj
+
+    def test_invalid_model_does_not_change_current_model(self, capsys):
+        cli_obj = self._make_cli()
+
+        with patch("hermes_cli.auth.resolve_provider", return_value="openrouter"), \
+             patch("hermes_cli.models.validate_requested_model", return_value={
+                 "accepted": False,
+                 "persist": False,
+                 "recognized": False,
+                 "message": "OpenRouter model IDs should use the `provider/model` format.",
+             }), \
+             patch("cli.save_config_value") as save_mock:
+            cli_obj.process_command("/model invalid-model")
+
+        output = capsys.readouterr().out
+        assert "Current model unchanged" in output
+        assert cli_obj.model == "anthropic/claude-opus-4.6"
+        assert cli_obj.agent is not None
+        save_mock.assert_not_called()
+
+    def test_unknown_model_stays_session_only(self, capsys):
+        cli_obj = self._make_cli()
+
+        with patch("hermes_cli.auth.resolve_provider", return_value="openrouter"), \
+             patch("hermes_cli.models.validate_requested_model", return_value={
+                 "accepted": True,
+                 "persist": False,
+                 "recognized": False,
+                 "message": "Using it for this session only; config unchanged.",
+             }), \
+             patch("cli.save_config_value") as save_mock:
+            cli_obj.process_command("/model anthropic/claude-sonnet-next")
+
+        output = capsys.readouterr().out
+        assert "session only" in output
+        assert cli_obj.model == "anthropic/claude-sonnet-next"
+        assert cli_obj.agent is None
+        save_mock.assert_not_called()