LbMCSubmit: Streamlined production and submission of LHCb MC requests

The LHCb experiment requires a wide variety of Monte Carlo simulated samples to support its physics programme and detector upgrade studies. Millions of events are typically requested, so the production system is run centrally via DIRAC on LHCb’s distributed computing resources to handle the demand. To streamline this process, well-defined configurations for request generation and a robust platform for submission, review, and discussion are essential. The package LbMCSubmit was introduced to simplify request definition using a rule-based approach, resolving combinatorial complexities and allowing users to generate full configurations from a structured set of inputs. For submission, a GitLab-based workflow was developed, integrating request submission, review, and automated testing via Continuous Integration (CI). Requests are submitted through GitLab’s merge request system, where they undergo validation before being sent to DIRAC. Introduced in spring 2023 and continuously updated, this system has become the standard for LHCb simulation requests.