docs(server): clarify manual cleanup is runtime-dependent

Kubernetes providers may reject null timeout when the workload provider
does not support non-expiring sandboxes. Make this constraint explicit
in the OpenAPI spec and schema description.

Made-with: Cursor

Author: hittyt

server/src/api/schema.py

@@ -319,7 +319,9 @@ class CreateSandboxRequest(BaseModel):
         description=(
             "Sandbox timeout in seconds (minimum 60). "
             "The maximum is controlled by server.max_sandbox_timeout_seconds. "
-            "When omitted or null, the sandbox will not auto-terminate and must be deleted explicitly."
+            "When omitted or null, the sandbox will not auto-terminate and must be deleted explicitly. "
+            "Note: manual cleanup support is runtime-dependent; Kubernetes providers may reject "
+            "null timeout when the workload provider does not support non-expiring sandboxes."
         ),
     )
     resource_limits: ResourceLimits = Field(

specs/sandbox-lifecycle.yml

@@ -780,6 +780,8 @@ components:
             Sandbox timeout in seconds. The sandbox will automatically terminate after this duration.
             The maximum is controlled by the server configuration (`server.max_sandbox_timeout_seconds`).
             Omit or set null to disable automatic expiration and require explicit cleanup.
+            Note: manual cleanup support is runtime-dependent; Kubernetes providers may reject
+            null timeout when the underlying workload provider does not support non-expiring sandboxes.
 
         resourceLimits:
           $ref: '#/components/schemas/ResourceLimits'