Member of Technical Staff - Research Engineer

About Black Forest Labs

We’re the team behind Latent Diffusion, Stable Diffusion, and FLUX—foundational technologies that changed how the world creates images and video. We’re creating the generative models that power how people make images and video—tools used by millions of creators, developers, and businesses worldwide. Our FLUX models are among the most advanced in the world, and we’re just getting started.

Headquartered in Freiburg, Germany with a growing presence in San Francisco, we’re scaling fast while staying true to what makes us different: research excellence, open science, and building technology that expands human creativity.

Large-scale training is where research ideas become real, and where many of the hardest problems are no longer cleanly separated into “research” or “engineering.” A promising architecture only matters if we can train it stably, efficiently, and correctly across large GPU fleets.

In this role, you will be embedded in production training and help where the hardest systems and performance problems arise: attention performance, custom kernels, low-precision training, profiling, memory behavior, data movement, distributed training stability, and throughput regressions. You will work directly with researchers, but your output will often be code, measurements, kernels, debugging tools, and training-system changes that make better research possible.

We are open to a range of seniority for this role. The common thread is deep technical ownership: you should be able to make progress in ambiguous training-system problems, verify your results, and own the outcome.

• Improve the performance, reliability, and numerical stability of production training runs for large multimodal generative models
• Profile full training steps across model code, attention, kernels, data loading, encoders, communication, optimizer steps, checkpointing, and memory pressure
• Implement and validate GPU-level optimizations: fused kernels, attention paths, low-precision matmuls, quantization kernels, CUDA/Triton/CuTe/CUTLASS experiments, and no‑compile alternatives where they make sense
• Push lower‑precision training forward, including FP8 / MXFP8 / FP4‑style paths, weight and activation quantization, accumulation choices, convergence risk, and quality tradeoffs against baseline training runs
• Work with researchers to translate architecture changes into efficient training implementations, and help distinguish real model‑quality progress from changes that only look good in a microbenchmark
• Debug distributed training failures:
  NaNs, loss spikes, silent numerical drift, memory leaks, stragglers, bad nodes, NCCL issues, and throughput cliffs
• Build benchmarking and profiling harnesses that make performance claims trustworthy across hardware, shapes, sequence lengths, and training configurations
• Help the training team move quickly when an urgent bottleneck appears, while turning repeated failures into better abstractions and tools

• Experience working deeply on large‑scale training systems, ideally as part of a training group working closely with researchers
• Strong PyTorch fluency, including comfort reading and modifying low‑level training code rather than only using high‑level APIs
• Experience with distributed training concepts such as FSDP, tensor/model/context/sequence parallelism, activation checkpointing, NCCL, and overlapping compute and communication
• Hands‑on experience improving training throughput, memory footprint, or stability in real training runs
• Experience profiling GPU workloads with tools like Nsight Systems, Nsight Compute, torch profiler, trace viewers, or custom telemetry
• Practical GPU performance judgment: you may use modern coding agents and tools as much as you want, but you need the understanding to verify correctness, numerical behavior, and performance, and to own the result
• Understanding of low‑precision training and quantization tradeoffs: FP8, MXFP8, FP4/NVFP4‑style formats, scaling, accumulation, numerical validation, and convergence risk
• Good research judgment: you can partner with researchers on ablations, understand what the measurements do and…