fix(cli): preserve JSON deploy errors

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

libs/cli/langgraph_cli/deploy.py

@@ -1604,11 +1604,15 @@ def _deploy_cmd(
     # -- 1. Preflight --
     validate_deploy_commands(install_command, build_command)
     if not config.exists():
-        raise click.ClickException(
+        message = (
             "We couldn't find a langgraph.json file. Run `langgraph deploy` from "
             "the root of a LangSmith Deployment project. To get started, visit "
             "https://docs.langchain.com/langsmith/application-structure."
         )
+        if json_output:
+            em.error(message)
+            raise click.exceptions.Exit(1)
+        raise click.ClickException(message)
     config_json = langgraph_cli.config.validate_config_file(config)
     warn_non_wolfi_distro(config_json, emit=em.note)
 

libs/cli/tests/unit_tests/cli/test_cli.py

@@ -333,6 +333,18 @@ def test_deploy_missing_config_shows_actionable_error(tmp_path, monkeypatch) ->
     assert "Traceback" not in result.output
 
 
+def test_deploy_missing_config_emits_json_error(tmp_path, monkeypatch) -> None:
+    runner = CliRunner()
+    monkeypatch.chdir(tmp_path)
+
+    result = runner.invoke(cli, ["deploy", "--json"])
+
+    assert result.exit_code == 1
+    events = [json.loads(line) for line in result.output.splitlines()]
+    assert events[-1]["event"] == "error"
+    assert "We couldn't find a langgraph.json file." in events[-1]["message"]
+
+
 def test_dev_command_requires_ssl_certfile_and_keyfile_together(tmp_path) -> None:
     config_path = tmp_path / "langgraph.json"
     config_path.write_text(