fix(vertex): surface vertex in the /model picker — credential gate + curated model list

Community verification of #56688 (zmack12344321) found two follow-up gaps
that kept Vertex invisible in the /model menu even after registry
registration:

1. hermes_cli/model_switch.py: list_authenticated_providers() had a
   credential gate hard-coded to API keys (with an aws_sdk special case
   only) — add a vertex branch using has_vertex_credentials(), mirroring
   the aws_sdk shape.
2. hermes_cli/models.py: Vertex's OpenAI-compatible endpoint has no
   /models listing route, so without a curated _PROVIDER_MODELS entry the
   picker only ever showed the current model — add a Gemini curated list.

Follow-up to #56688.

hermes_cli/model_switch.py

@@ -2024,6 +2024,16 @@ def list_authenticated_providers(
         has_creds = False
         if overlay.auth_type == "aws_sdk":
             has_creds = _has_aws_sdk_creds_for_listing(hermes_slug)
+        elif overlay.auth_type == "vertex":
+            # Vertex authenticates via OAuth2 (service-account JSON / ADC),
+            # not an API key — mirror the aws_sdk gate above, otherwise the
+            # provider is silently hidden from the /model picker even when
+            # fully configured.
+            try:
+                from agent.vertex_adapter import has_vertex_credentials
+                has_creds = has_vertex_credentials()
+            except Exception as exc:
+                logger.debug("Vertex credential check failed: %s", exc)
         elif overlay.extra_env_vars:
             has_creds = any(os.environ.get(ev) for ev in overlay.extra_env_vars)
         # Also check api_key_env_vars from PROVIDER_REGISTRY for api_key auth_type

hermes_cli/models.py

@@ -560,6 +560,18 @@ _PROVIDER_MODELS: dict[str, list[str]] = {
     # Azure Foundry: user-provided endpoint and model.
     # Empty list because models depend on the endpoint configuration.
     "azure-foundry": [],
+    # Google Vertex AI — static curated list.  Vertex's OpenAI-compatible
+    # endpoint has no /models listing route, so without this entry the
+    # /model picker only ever shows the currently-configured model.
+    # Model IDs use the "google/" publisher prefix Vertex's openapi
+    # endpoint expects (see hermes_cli/model_setup_flows.py).
+    "vertex": [
+        "google/gemini-3.1-pro-preview",
+        "google/gemini-3-pro-preview",
+        "google/gemini-3.5-flash",
+        "google/gemini-3-flash-preview",
+        "google/gemini-3.1-flash-lite-preview",
+    ],
     "novita": [
         "moonshotai/kimi-k2.5",
         "minimax/minimax-m2.7",

tests/hermes_cli/test_vertex_model_picker.py

@@ -0,0 +1,49 @@
+"""Vertex visibility in the /model picker (follow-up to PR #56688).
+
+Community verification of the vertex-registration fix found two remaining
+gaps that kept the provider invisible/unusable in the /model menu:
+
+1. ``list_authenticated_providers`` had no credential gate for the
+   ``vertex`` auth_type (only ``aws_sdk`` was special-cased), so the
+   provider was silently hidden even when fully configured.
+2. Vertex's OpenAI-compatible endpoint has no ``/models`` listing route,
+   so without a curated ``_PROVIDER_MODELS["vertex"]`` entry the picker
+   only ever showed the currently-configured model.
+
+No network calls.
+"""
+
+from __future__ import annotations
+
+from unittest.mock import patch
+
+from hermes_cli.model_switch import list_authenticated_providers
+from hermes_cli.models import _PROVIDER_MODELS
+
+
+def test_vertex_has_curated_model_list():
+    """Vertex has no /models route — the picker needs a static curated list."""
+    models = _PROVIDER_MODELS.get("vertex")
+    assert models, "_PROVIDER_MODELS must have a non-empty 'vertex' entry"
+    # Vertex's openapi endpoint expects the google/ publisher prefix.
+    assert all(m.startswith("google/") for m in models)
+
+
+def test_vertex_appears_when_credentials_configured():
+    """has_vertex_credentials() == True must surface vertex in the picker."""
+    with patch("agent.vertex_adapter.has_vertex_credentials", return_value=True):
+        providers = list_authenticated_providers(current_provider="openrouter", max_models=50)
+
+    vertex = next((p for p in providers if p["slug"] == "vertex"), None)
+    assert vertex is not None, "vertex should appear when credentials are configured"
+    assert vertex["models"], "vertex row must carry the curated model list"
+    assert "google/gemini-3-pro-preview" in vertex["models"]
+
+
+def test_vertex_hidden_without_credentials():
+    """No service-account path / project override → vertex stays hidden."""
+    with patch("agent.vertex_adapter.has_vertex_credentials", return_value=False):
+        providers = list_authenticated_providers(current_provider="openrouter", max_models=50)
+
+    vertex = next((p for p in providers if p["slug"] == "vertex"), None)
+    assert vertex is None, "vertex should not appear without credentials"