Improve config validation error messages (#825)

* improve config validation error messages and update getting started demo

* fix black formatting

cli/planoai/config_generator.py

@@ -3,7 +3,7 @@ import os
 from planoai.utils import convert_legacy_listeners
 from jinja2 import Environment, FileSystemLoader
 import yaml
-from jsonschema import validate
+from jsonschema import validate, ValidationError
 from urllib.parse import urlparse
 from copy import deepcopy
 from planoai.consts import DEFAULT_OTEL_TRACING_GRPC_ENDPOINT
@@ -507,11 +507,15 @@ def validate_prompt_config(plano_config_file, plano_config_schema_file):
 
     try:
         validate(config_yaml, config_schema_yaml)
-    except Exception as e:
-        print(
-            f"Error validating plano_config file: {plano_config_file}, schema file: {plano_config_schema_file}, error: {e}"
+    except ValidationError as e:
+        path = (
+            " → ".join(str(p) for p in e.absolute_path) if e.absolute_path else "root"
         )
-        raise e
+        raise ValidationError(
+            f"{e.message}\n  Location: {path}\n  Value: {e.instance}"
+        ) from None
+    except Exception as e:
+        raise
 
 
 if __name__ == "__main__":

cli/planoai/native_runner.py

@@ -420,9 +420,16 @@ def native_validate_config(plano_config_file):
     with _temporary_env(overrides):
         from planoai.config_generator import validate_and_render_schema
 
-        # Suppress verbose print output from config_generator
-        with contextlib.redirect_stdout(io.StringIO()):
-            validate_and_render_schema()
+        # Suppress verbose print output from config_generator but capture errors
+        captured = io.StringIO()
+        try:
+            with contextlib.redirect_stdout(captured):
+                validate_and_render_schema()
+        except SystemExit:
+            # validate_and_render_schema calls exit(1) on failure after
+            # printing to stdout; re-raise so the caller gets a useful message.
+            output = captured.getvalue().strip()
+            raise Exception(output) if output else Exception("Config validation failed")
 
 
 def native_logs(debug=False, follow=False):