fix(cli): defer AWS serverless support to the backend

Co-authored-by: open-swe[bot] <open-swe@users.noreply.github.com>

libs/cli/langgraph_cli/deploy.py

@@ -1548,11 +1548,6 @@ def _resolve_or_create(
     )
     if found is not None:
         return found.id, step
-    if ctx.endpoints.is_aws and ctx.deployment_type == "dev_zero":
-        raise click.UsageError(
-            "Serverless deployments are not supported on AWS yet. "
-            "Use --deployment-type dev instead."
-        )
     try:
         created, step = _create_deployment(
             ctx.client,
@@ -1565,6 +1560,14 @@ def _resolve_or_create(
             secrets=ctx.secrets,
         )
     except HostBackendError as err:
+        if err.status_code == 400 and err.detail == (
+            "Scale to zero deployments are not supported in AWS environments"
+        ):
+            raise HostBackendError(
+                f"{err.message}\nUse --deployment-type dev instead.",
+                status_code=err.status_code,
+                detail=err.detail,
+            ) from None
         if _needs_a_listener(err):
             raise ListenerRequiredError(
                 "The image has to come from a registry you manage, so re-run with "
@@ -2219,8 +2222,8 @@ def _deploy_base_options(
             click.option(
                 "--deployment-type",
                 type=click.Choice(["serverless", "dedicated", "dev", "prod"]),
-                default=None,
-                show_default="serverless; dev on AWS",
+                default="serverless",
+                show_default=True,
                 help=(
                     "Deployment type (used when creating a new deployment): "
                     "serverless (scale to zero) or dedicated (prod); "
@@ -2401,7 +2404,7 @@ def _deploy_cmd(
     host_url: str | None,
     api_key: str | None,
     deployment_id: str | None,
-    deployment_type: str | None,
+    deployment_type: str,
     name: str | None,
     agent_id: str | None,
     environment: str | None,
@@ -2493,9 +2496,6 @@ def _deploy_cmd(
     )
 
     client = _create_host_backend_client(host_url, api_key, env_vars=env_vars)
-    deployment_type = deployment_type or (
-        "dev" if client.endpoints.is_aws else "serverless"
-    )
     try:
         tracked_packages = find_tracked_packages(config, config_json) or None
     except Exception as exc: