fix(cloud): handle unavailable skill capability

src/langbot/pkg/api/http/controller/groups/skills.py

@@ -2,6 +2,7 @@ from __future__ import annotations
 
 import quart
 
+from langbot.pkg.cloud.entitlements import EntitlementFeatureUnavailableError
 from langbot_plugin.box.errors import BoxError
 
 from ...authz import Permission
@@ -23,6 +24,11 @@ class SkillsRouterGroup(group.RouterGroup):
         async def list_skills(request_context: RequestContext) -> quart.Response:
             try:
                 skills = await self.ap.skill_service.list_skills(request_context)
+            except EntitlementFeatureUnavailableError:
+                # Plans without managed sandbox support have no runnable skills.
+                # Treat that capability absence as an empty collection so the
+                # shared UI can render normally instead of surfacing a 500.
+                return self.success(data={'skills': []})
             except (ValueError, BoxError) as exc:
                 return self.http_status(400, -1, str(exc))
             return self.success(data={'skills': skills})

src/langbot/pkg/cloud/entitlements.py

@@ -17,6 +17,22 @@ class EntitlementUnavailableError(RuntimeError):
         self.entitlement_revision = entitlement_revision
 
 
+class EntitlementFeatureUnavailableError(EntitlementUnavailableError):
+    """Raised only when an active entitlement does not grant one feature."""
+
+    def __init__(
+        self,
+        feature: str,
+        *,
+        entitlement_revision: int | None = None,
+    ) -> None:
+        self.feature = feature
+        super().__init__(
+            f'Workspace entitlement does not grant {feature}',
+            entitlement_revision=entitlement_revision,
+        )
+
+
 class EntitlementSnapshot(pydantic.BaseModel):
     """Capability projection consumed by open-source Core.
 
@@ -82,7 +98,10 @@ class EntitlementSnapshot(pydantic.BaseModel):
 
     def require_feature(self, feature: str) -> None:
         if self.features.get(feature) is not True:
-            raise EntitlementUnavailableError(f'Workspace entitlement does not grant {feature}')
+            raise EntitlementFeatureUnavailableError(
+                feature,
+                entitlement_revision=self.entitlement_revision,
+            )
 
     def limit(self, name: str) -> int:
         value = self.limits.get(name)