POST /prompt_manager/logs/config forwarded the whole request body into PromptManagerLogger.update_config(), so any key could be injected into the logging configuration. The handler now accepts only LOG_CONFIG_KEYS (level, max_file_size, backup_count, console_logging, file_logging, buffer_size), type-checks each value (level name, non-negative int, bool) and answers 400 listing unknown keys. Malformed or non-object bodies are 400 instead of 500.