fix(desktop): report session override provider in session info

tests/test_tui_gateway_server.py

@@ -4537,6 +4537,51 @@ def get_session_title(self, key):
     assert info["title"] == "Dashboard title"
 
 
+def test_session_info_prefers_session_model_override_provider_for_custom_runtime():
+    agent = types.SimpleNamespace(
+        tools=[],
+        model="shared-model",
+        provider="custom",
+        base_url="https://provider-a.example/v1",
+        api_mode="codex_responses",
+    )
+    session = {
+        "session_key": "session-key",
+        "history": [],
+        "model_override": {
+            "model": "shared-model",
+            "provider": "custom-provider-a",
+            "base_url": "https://provider-a.example/v1",
+            "api_mode": "codex_responses",
+        },
+    }
+
+    info = server._session_info(agent, session)
+
+    assert info["model"] == "shared-model"
+    assert info["provider"] == "custom-provider-a"
+
+
+def test_session_info_ignores_stale_model_override_provider():
+    agent = types.SimpleNamespace(
+        tools=[],
+        model="current-model",
+        provider="openai-codex",
+    )
+    session = {
+        "session_key": "session-key",
+        "history": [],
+        "model_override": {
+            "model": "old-model",
+            "provider": "custom-provider-a",
+        },
+    }
+
+    info = server._session_info(agent, session)
+
+    assert info["provider"] == "openai-codex"
+
+
 # ---------------------------------------------------------------------------
 # History-mutating commands must reject while session.running is True.
 # Without these guards, prompt.submit's post-run history write either

tui_gateway/server.py

@@ -3028,6 +3028,31 @@ def _current_profile_name() -> str:
 DESKTOP_BACKEND_CONTRACT = 2
 
 
+def _session_info_provider(agent, session: dict | None = None) -> str:
+    """Return the user-facing provider identity for ``session.info``.
+
+    ``agent.provider`` is the resolved runtime/billing class. For named custom
+    providers that value can be the literal ``custom`` even though the user chose
+    a routable provider slug from the desktop picker. If Desktop persists that
+    internal value into its sticky composer state, the next ``session.create``
+    can pair the right model with the wrong provider group.
+
+    The per-session ``model_override`` is the source of truth for picker and
+    live ``/model`` switches, so prefer it while it still describes the agent's
+    current model. Fall back to the runtime provider for older sessions and
+    built-in providers.
+    """
+    provider = str(getattr(agent, "provider", "") or "").strip()
+    override = (session or {}).get("model_override") if isinstance(session, dict) else None
+    if isinstance(override, dict):
+        override_provider = str(override.get("provider") or "").strip()
+        override_model = str(override.get("model") or "").strip()
+        agent_model = str(getattr(agent, "model", "") or "").strip()
+        if override_provider and (not override_model or override_model == agent_model):
+            return override_provider
+    return provider
+
+
 def _session_info(agent, session: dict | None = None) -> dict:
     if session is None:
         for candidate in _sessions.values():
@@ -3070,7 +3095,7 @@ def _session_info(agent, session: dict | None = None) -> dict:
         yolo = False
     info: dict = {
         "model": getattr(agent, "model", ""),
-        "provider": getattr(agent, "provider", ""),
+        "provider": _session_info_provider(agent, session),
         "reasoning_effort": reasoning_effort,
         "service_tier": service_tier,
         "fast": service_tier == "priority",