R-ConstraintBench is a framework designed to test large language models (LLMs) on complex, real-world operational challenges such as project management and resource allocation, by evaluating their ability to generate schedules that satisfy multiple constraints simultaneously. It introduces a systematic approach to assess LLM reasoning by incrementally increasing task complexity and applying realistic operational rules, thus serving as a stress test for their reasoning capabilities. Initial findings reveal that no current model maintains consistent feasibility under high-complexity scenarios, with o3 and GPT-5 showing the best performance in synthetic stress tests and GPT-5 leading in domain-specific tasks such as data center migration. The results suggest that effective scheduling under tight constraints remains a challenge, as constraint interaction often leads to reliability breakdowns, highlighting a need for targeted improvements in model training. R-ConstraintBench offers a practical tool for laboratories to evaluate LLM-generated plans, identify feasibility breakdowns, and ensure that successes on synthetic tasks translate to real-world applications, while also providing guidance on improving model performance by focusing on global consistency and domain-specific evaluations.