ML Research Engineer

White Circle; Paris; Hybrid; EUR 90,000 - 130,000; Full time

Benefits offered by this job

Paid time off

Hybrid work (Paris/London)

Relocation support for Paris

Medical insurance for France-based

Hardware, tools and services

Team off-sites

Job summary

White Circle is seeking several ML Engineers to train, post-train, and evaluate the LLMs at the core of our platform. You will work hands-on with large-scale data pipelines, SFT/RLHF-style alignment, and distributed multi-GPU training to push safety and reliability.

Join a focused team building scalable representations, labeling, and diagnostics that feed product decisions and operations. Hybrid Paris/London roles with relocation support for Paris.

Qualifications

• Strong Python + SQL with an engineering mindset.
• Solid applied NLP/ML experience on real-world text.
• Experience with large-scale data processing and pipelines.
• Familiarity with safety/moderation datasets or policy/rule systems is a plus.
• Multilingual model training experience is a plus.

Responsibilities

• Turn petabytes of unstructured text into a structured, explorable view.
• Build scalable representation pipelines: sampling, preprocessing, embeddings, indexing, retrieval.
• Use LLMs pragmatically: labeling, weak supervision, data enrichment, diagnostics.
• Deliver insights that translate findings into product/actions.
• Ship self-serve analytics: datasets, data models, dashboards.
• Partner with engineering/research to align pipelines with production constraints.

Skills

Python

SQL

NLP/ML

Distributed training

Data pipelines

Model evaluation

Tools

PyTorch

HuggingFace

TensorFlow

Job description

TLDR: We are looking for several ML Engineers to train, post-train, and evaluate the LLMs at the core of our platform. This is hands-on modern model training work: large-scale data pipelines, SFT/RLHF/DPO-style alignment, reward models, distributed multi-GPU training, and evaluation.

About us

White Circle is an AI Safety company building the safety, reliability, and optimization layer for AI systems. At the core of our platform are policies - simple natural-language rules that define what an AI model should and shouldn’t do. We automatically test, enforce, and continuously improve these policies at scale.

• We’ve raised $11M from top funds, founders, and senior leaders at OpenAI, Anthropic, HuggingFace, Mistral, DeepMind, Datadog, Sentry, and others

• We process over 100M+ API calls every month

• We fine-tune and train our own LLMs so they run faster and cheaper than any open or proprietary model

We’re a small, highly focused team. If you want to work deeply on hard problems, see your work ship to production quickly, and influence how AI safety is actually built - you’re the one we need.

You will:

• Turn petabytes of unstructured text into a structured, explorable view (topics, clusters, segments, trends, anomalies): iterate from "unknown unknowns" to stable definitions we can track.

• Build scalable representation pipelines: sampling strategies, preprocessing/normalization, embeddings at scale, indexing, and retrieval to make the corpus searchable and analyzable.

• Use LLMs pragmatically: labeling/classification, weak supervision, data enrichment, summarization, and automated diagnostics of inbound volumes (with cost/quality controls).

• Deliver insights that change decisions: translate findings into product and operational actions (what data we have, what's missing, where quality breaks, what to prioritize next).

• Ship self-serve analytics: datasets, data models, and lightweight tools/dashboards so the team can explore and answer questions without ad-hoc requests.

• Partner closely with engineering/research: align pipelines with production constraints (latency/cost/privacy), and integrate outputs into workflows.

You’ll fit right in if you:

• Strong Python + SQL with an engineering mindset: you can build reliable pipelines, not just notebooks.

• Solid applied NLP/ML experience on real-world text: embeddings, clustering, topic modeling, semantic search, classification; you understand failure modes and how to debug them.

• Comfortable at scale: distributed processing, large-scale storage-querying, and performance-cost tradeoffs.

• You know how to evaluate fuzzy problems: offline/online metrics, human-in-the-loop labelling, inter-annotator agreement, drift monitoring, and reproducibility.

• Have prior work with safety/moderation datasets, policy/rule systems, or high-volume logging/observability

A big plus:

• A public builder footprint: open-source models, datasets, or training frameworks on HuggingFace/GitHub, benchmarks, papers (workshop or main conference), or technical posts with real usage

• Experience training models at a frontier or near-frontier lab, or leading open-source model releases with documented adoption

• Experience with RL methods for LLMs beyond standard RLHF: online RL, GRPO-style methods, or novel alignment approaches

• Experience with moderation, safety, or classification models at scale

• Multilingual model training experience

Why White Circle

• Paid time off in line with your local regulations, no matter where you work from

• Work from Paris (hybrid) with a relocation package available, or work from London (note: we are currently unable to provide relocation support and medical insurance for London-based roles)

• Comprehensive medical insurance for our France-based team

• All the hardware, tools, and services you need

• Covered subscriptions for AI agents and IDEs

• Team off-sites twice a year: we’ve recently been to the Alps and to Saint-Tropez