Modern information retrieval increasingly employs both embedding and generative models to handle complex queries. However, current serving systems suffer from low throughput and poor GPU utilization because they execute these models in isolation. Coarse-grained partitioning, such as dedicating GPUs to specific tasks, fails to adapt to dynamic workloads and creates computational “bubbles”. To address these, we present Orthrus, a serving system that performs heterogeneous batching within a single GPU kernel. The primary challenge lies in unifying embedding and generation workloads with conflicting computational patterns while optimizing batch composition for high performance. Orthrus addresses these challenges by employing incremental computing to match compute patterns and by adjusting batch composition in a workload-aware manner. Evaluation on four A100 GPUs shows that Orthrus achieves 1.28×–4.52× higher throughput and up to 52.0% lower latency than various deployment scenarios based on homogeneous batching, including those built on vLLM. We release our code at [https://github.com/illinoisdata/Orthrus](https://github.com/illinoisdata/Orthrus)