Add environment variable override support for config.yaml (#1748)

* Initial plan

* Add environment variable override support for config.yaml

Co-authored-by: RockChinQ <45992437+RockChinQ@users.noreply.github.com>

* Refactor env override code based on review feedback

Co-authored-by: RockChinQ <45992437+RockChinQ@users.noreply.github.com>

* Add test for template completion with env overrides

Co-authored-by: RockChinQ <45992437+RockChinQ@users.noreply.github.com>

* Move env override logic to load_config.py as requested

Co-authored-by: RockChinQ <45992437+RockChinQ@users.noreply.github.com>

* perf: add print log

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: RockChinQ <45992437+RockChinQ@users.noreply.github.com>
Co-authored-by: Junyan Qin <rockchinq@gmail.com>

pkg/core/stages/load_config.py

@@ -1,11 +1,93 @@
 from __future__ import annotations
 
 import os
+from typing import Any
 
 from .. import stage, app
 from ..bootutils import config
 
 
+def _apply_env_overrides_to_config(cfg: dict) -> dict:
+    """Apply environment variable overrides to data/config.yaml
+
+    Environment variables should be uppercase and use __ (double underscore)
+    to represent nested keys. For example:
+    - CONCURRENCY__PIPELINE overrides concurrency.pipeline
+    - PLUGIN__RUNTIME_WS_URL overrides plugin.runtime_ws_url
+
+    Arrays and dict types are ignored.
+
+    Args:
+        cfg: Configuration dictionary
+
+    Returns:
+        Updated configuration dictionary
+    """
+
+    def convert_value(value: str, original_value: Any) -> Any:
+        """Convert string value to appropriate type based on original value
+
+        Args:
+            value: String value from environment variable
+            original_value: Original value to infer type from
+
+        Returns:
+            Converted value (falls back to string if conversion fails)
+        """
+        if isinstance(original_value, bool):
+            return value.lower() in ('true', '1', 'yes', 'on')
+        elif isinstance(original_value, int):
+            try:
+                return int(value)
+            except ValueError:
+                # If conversion fails, keep as string (user error, but non-breaking)
+                return value
+        elif isinstance(original_value, float):
+            try:
+                return float(value)
+            except ValueError:
+                # If conversion fails, keep as string (user error, but non-breaking)
+                return value
+        else:
+            return value
+
+    # Process environment variables
+    for env_key, env_value in os.environ.items():
+        # Check if the environment variable is uppercase and contains __
+        if not env_key.isupper():
+            continue
+        if '__' not in env_key:
+            continue
+
+        print(f'apply env overrides to config: env_key: {env_key}, env_value: {env_value}')
+
+        # Convert environment variable name to config path
+        # e.g., CONCURRENCY__PIPELINE -> ['concurrency', 'pipeline']
+        keys = [key.lower() for key in env_key.split('__')]
+
+        # Navigate to the target value and validate the path
+        current = cfg
+
+        for i, key in enumerate(keys):
+            if not isinstance(current, dict) or key not in current:
+                break
+
+            if i == len(keys) - 1:
+                # At the final key - check if it's a scalar value
+                if isinstance(current[key], (dict, list)):
+                    # Skip dict and list types
+                    pass
+                else:
+                    # Valid scalar value - convert and set it
+                    converted_value = convert_value(env_value, current[key])
+                    current[key] = converted_value
+            else:
+                # Navigate deeper
+                current = current[key]
+
+    return cfg
+
+
 @stage.stage_class('LoadConfigStage')
 class LoadConfigStage(stage.BootingStage):
     """Load config file stage"""
@@ -54,6 +136,10 @@ class LoadConfigStage(stage.BootingStage):
         ap.instance_config = await config.load_yaml_config(
             'data/config.yaml', 'templates/config.yaml', completion=False
         )
+
+        # Apply environment variable overrides to data/config.yaml
+        ap.instance_config.data = _apply_env_overrides_to_config(ap.instance_config.data)
+
         await ap.instance_config.dump_config()
 
         ap.sensitive_meta = await config.load_json_config(