fix(xai): resolve Grok Build context for OAuth

agent/model_metadata.py

@@ -209,6 +209,7 @@ 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-build": 256000,       # grok-build-0.1
     "grok-code-fast": 256000,   # grok-code-fast-1
     "grok-4-1-fast": 2000000,   # grok-4-1-fast-(non-)reasoning
     "grok-2-vision": 8192,      # grok-2-vision, -1212, -latest

agent/models_dev.py

@@ -167,6 +167,9 @@ PROVIDER_TO_MODELS_DEV: Dict[str, str] = {
     "gemini": "google",
     "google": "google",
     "xai": "xai",
+    # xAI OAuth is an authentication/transport path for the same xAI model
+    # catalog, so model metadata should resolve through the xAI provider.
+    "xai-oauth": "xai",
     "xiaomi": "xiaomi",
     "nvidia": "nvidia",
     "groq": "groq",