feat(xai): add grok-composer-2.5-fast to xAI OAuth model picker

The model is callable via xAI OAuth but omitted from models.dev and
/v1/models listings. Merge it into the curated xAI catalog so it appears
in `hermes model` without requiring a custom model name.

agent/model_metadata.py

@@ -275,6 +275,7 @@ DEFAULT_CONTEXT_LENGTHS = {
     # via a custom provider. Values sourced from models.dev (2026-04).
     # Keys use substring matching (longest-first), so e.g. "grok-4.20"
     # matches "grok-4.20-0309-reasoning" / "-non-reasoning" / "-multi-agent-0309".
+    "grok-composer": 200000,    # grok-composer-2.5-fast (Grok Build CLI)
     "grok-build": 256000,       # grok-build-0.1
     "grok-code-fast": 256000,   # grok-code-fast-1
     "grok-2-vision": 8192,      # grok-2-vision, -1212, -latest

hermes_cli/models.py

@@ -117,6 +117,11 @@ _XAI_STATIC_FALLBACK: list[str] = [
     "grok-4.20-multi-agent-0309",
 ]
 
+# Callable via xAI OAuth but omitted from models.dev and /v1/models listings.
+_XAI_CURATED_EXTRAS: list[str] = [
+    "grok-composer-2.5-fast",
+]
+
 
 _XAI_TOP_MODEL = "grok-build-0.1"
 
@@ -128,6 +133,18 @@ def _xai_promote_top(ids: list[str]) -> list[str]:
     return ids
 
 
+def _xai_merge_curated_extras(ids: list[str]) -> list[str]:
+    """Append Hermes-curated xAI models that are missing from models.dev."""
+    out = list(ids)
+    for extra in _XAI_CURATED_EXTRAS:
+        if extra in out:
+            continue
+        # Keep the headline model pinned; slot extras immediately after it.
+        insert_at = 1 if out and out[0] == _XAI_TOP_MODEL else len(out)
+        out.insert(insert_at, extra)
+    return out
+
+
 def _xai_curated_models() -> list[str]:
     """Derive the xAI-direct curated list from models.dev disk cache.
 
@@ -147,12 +164,12 @@ def _xai_curated_models() -> list[str]:
         if isinstance(models, dict) and models:
             ids = [mid for mid in models.keys() if isinstance(mid, str)]
             if ids:
-                return _xai_promote_top(sorted(ids))
+                return _xai_merge_curated_extras(_xai_promote_top(sorted(ids)))
     except Exception:
         # Any failure (missing file, malformed JSON, import error)
         # falls through to the static list.
         pass
-    return list(_XAI_STATIC_FALLBACK)
+    return _xai_merge_curated_extras(list(_XAI_STATIC_FALLBACK))
 
 
 _PROVIDER_MODELS: dict[str, list[str]] = {

tests/hermes_cli/test_xai_curated_models.py

@@ -0,0 +1,14 @@
+"""Regression tests for xAI curated model list (OAuth picker)."""
+
+from hermes_cli.models import _PROVIDER_MODELS, provider_model_ids
+
+
+def test_xai_oauth_includes_grok_composer_2_5_fast():
+    models = provider_model_ids("xai-oauth")
+    assert "grok-composer-2.5-fast" in models
+
+
+def test_grok_composer_slots_after_grok_build():
+    models = _PROVIDER_MODELS["xai-oauth"]
+    assert models[0] == "grok-build-0.1"
+    assert models[1] == "grok-composer-2.5-fast"