fix(model): default --provider switches to session-only persistence

cli.py

@@ -7947,7 +7947,9 @@ def _handle_model_switch(self, cmd_original: str):
         # config-gated default, --global forces persist, otherwise defer to
         # model.persist_switch_by_default (defaults to True so /model survives
         # across sessions).
-        persist_global = resolve_persist_behavior(is_global_flag, is_session)
+        persist_global = resolve_persist_behavior(
+            is_global_flag, is_session, explicit_provider
+        )
 
         # --refresh: wipe the on-disk picker cache before building the
         # provider list. Forces a live re-fetch of every authed provider's

gateway/slash_commands.py

@@ -1399,7 +1399,9 @@ async def _handle_model_command(self, event: MessageEvent) -> Optional[str]:
             force_refresh,
             is_session,
         ) = parse_model_flags(raw_args)
-        persist_global = resolve_persist_behavior(is_global_flag, is_session)
+        persist_global = resolve_persist_behavior(
+            is_global_flag, is_session, explicit_provider
+        )
 
         # --refresh: bust the disk cache so the picker shows live data.
         if force_refresh:

hermes_cli/model_switch.py

@@ -365,14 +365,22 @@ def parse_model_flags(raw_args: str) -> tuple[str, str, bool, bool, bool]:
     return (model_input, explicit_provider, is_global, force_refresh, is_session)
 
 
-def resolve_persist_behavior(is_global: bool, is_session: bool) -> bool:
+def resolve_persist_behavior(
+    is_global: bool,
+    is_session: bool,
+    explicit_provider: str = "",
+) -> bool:
     """Decide whether a ``/model`` switch should persist to ``config.yaml``.
 
     Resolution order:
 
     1. ``--session`` explicitly opts out → ``False`` (this session only).
     2. ``--global`` explicitly opts in → ``True``.
-    3. Otherwise defer to ``model.persist_switch_by_default`` in
+    3. ``--provider`` given without an explicit persist flag → ``False``
+       (session only).  Provider switches are typically exploratory — the
+       user is trying a different backend for this conversation, not
+       reconfiguring the default.  ``--global`` can still force persist.
+    4. Otherwise defer to ``model.persist_switch_by_default`` in
        ``config.yaml`` (defaults to ``True``, so a plain ``/model <name>``
        survives across sessions — the behavior users expect).
 
@@ -384,6 +392,8 @@ def resolve_persist_behavior(is_global: bool, is_session: bool) -> bool:
         return False
     if is_global:
         return True
+    if explicit_provider:
+        return False
     try:
         from hermes_cli.config import load_config
 

tests/hermes_cli/test_model_switch_persist_default.py

@@ -96,6 +96,26 @@ def test_session_overrides_global_when_both_set(self):
         with _config({"model": {"persist_switch_by_default": True}}):
             assert resolve_persist_behavior(True, True) is False
 
+    def test_provider_flag_defaults_to_session_only(self):
+        # --provider without --global/--session → session only.
+        with _config({"model": {"persist_switch_by_default": True}}):
+            assert resolve_persist_behavior(False, False, "anthropic") is False
+
+    def test_provider_with_global_still_persists(self):
+        # --provider + --global → persists.
+        with _config({"model": {"persist_switch_by_default": False}}):
+            assert resolve_persist_behavior(True, False, "anthropic") is True
+
+    def test_provider_with_session_still_session_only(self):
+        # --provider + --session → session only.
+        with _config({"model": {"persist_switch_by_default": True}}):
+            assert resolve_persist_behavior(False, True, "anthropic") is False
+
+    def test_no_provider_uses_config_default(self):
+        # No --provider → respects config default (True).
+        with _config({"model": {"persist_switch_by_default": True}}):
+            assert resolve_persist_behavior(False, False, "") is True
+
 
 # ---------------------------------------------------------------------------
 # helper

tui_gateway/server.py

@@ -2628,7 +2628,9 @@ def _apply_model_switch(
         _force_refresh,
         is_session,
     ) = parsed_flags
-    persist_global = resolve_persist_behavior(is_global_flag, is_session)
+    persist_global = resolve_persist_behavior(
+        is_global_flag, is_session, explicit_provider
+    )
     if not model_input:
         raise ValueError("model value required")