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Hady Elsahar

Hady Elsahar

Staff Research Scientist at FAIR, Meta Superintelligence Labs, on the Content Seal team. I work at the intersection of generative AI and safety, currently on invisible watermarking and content provenance, helping scale AI-generated-media detection to billions of users and protecting millions of videos a day.

I've worked in generative AI since 2014, training my first language models back when we still derived gradients by hand, before autodiff made it effortless. Since then I've had a front-row seat to the field's evolution: from teaching models to copy words they had never seen before, to generating text in any language and steering what models say, to today's harder question: telling what's real in the age of deepfakes.

At Meta, I helped found the Content Seal team to establish invisible watermarking and provenance across the company's generative AI products. Beyond watermarking, I worked on the Seamless Project, a single model for speech translation across close to 100 languages, named a TIME Best Invention of 2023 and published in Nature. Before Meta, at Naver Labs Europe, I worked with Marc Dymetman on reinforcement learning for fine-tuning language models without catastrophic forgetting, foundational research into RL-based alignment. Earlier, I was at Bloomberg, IBM, and Microsoft, and did my Ph.D. at Université de Lyon with Christophe Gravier and Frédérique Laforest on generating natural language from knowledge graphs.

Beyond research, I was a board member of Masakhane, whose participatory-research paper received the Wikimedia Foundation Research Award, and I helped organize AfricaNLP. I care about making AI work for underrepresented languages and communities.

Open to mentorship. If you're an early-career researcher from an underrepresented group and want advice or encouragement, feel free to reach out.

No borders, free identities. We treat borders as physical realities and identities as fixed labels. I see them differently: borders are constructs we choose to believe in, and identity is a Ship of Theseus.

Selected projects

2024 – 2026

Content Seal

Helped found the Content Seal team, establishing watermarking inside Meta. Scaled watermarking research into products including Muse Image and Video, now watermarking millions of videos and audio clips per day across the family of apps, powered by our work on AudioSeal, Video Seal, Pixel Seal, and Text Seal.

Try invisible watermarking in your browser

2020 – 2022

Masakhane

Board member (2020–2022) of Masakhane, a grassroots community of 2,000+ researchers across 30+ African countries. Helped put African languages on the NLP map, co-organizing the AfricaNLP workshops, securing research funding, and building open datasets, benchmarks, and machine translation for 40+ African languages. Our participatory-research paper received the Wikimedia Foundation Research Award.

Try invisible watermarking

Research journey

Full, always-current publication list on Google Scholar and DBLP.

2014 – 2018

Ph.D., Université de Lyon

Knowledge-grounded generation & copy mechanisms for language models

My thesis addressed data-to-text generation and relation extraction, in the pre-Transformer era when models were still small enough to reason about by hand. I worked on out-of-vocabulary tokens and copy actions (early attention and pointer mechanisms, from a time when named entities were a plague before byte-pair encoding), and on conditioning recurrent language models (stacked LSTMs / GRUs) on retrieved knowledge-base facts via early KB embeddings (TransE): in retrospect, a precursor to retrieval-augmented generation (RAG). Attention of this kind is what self-attention would soon scale into the default way the world trains language models.

Zero-shot question generation model with a fact encoder, textual context encoders, and a copy-action GRU decoder using GloVe and TransE embeddings
A GRU decoder with part-of-speech copy actions, conditioned on knowledge-base facts (TransE) and textual context.

Selected papers

  • Zero-Shot Question Generation from Knowledge Graphs for Unseen Predicates and Entity Types · NAACL 2018 [paper][code]
  • Mind the (Language) Gap: Generation of Multilingual Wikipedia Summaries from Wikidata for ArticlePlaceholders · ESWC 2018 [paper][code]
  • Neural Wikipedian: Generating Textual Summaries from Knowledge Base Triples · Journal of Web Semantics · 2018 [paper]
  • Learning to Generate Wikipedia Summaries for Underserved Languages from Wikidata · NAACL 2018 [paper]

2018

Bloomberg, London

Neural abstractive summarization in production

I spent a year extending my summarization research into a summarization engine now deployed at scale in the Bloomberg Terminal, an early lesson in taking neural generation from paper to product.

Bloomberg Terminal NSTM (Key News Themes) output, grouping news into summarized themes
Bloomberg Terminal, NSTM (Key News Themes). The summarization engine ships under NSTM <GO>. Click to watch the demo.

2019 – 2022

Naver Labs Europe

Reinforcement learning for language models, without catastrophic forgetting

With Marc Dymetman, I studied fine-tuning language models under reinforcement learning while avoiding catastrophic forgetting, an early approach to RL-based alignment. We formalized control as constraint satisfaction over distributions, solved via Energy-Based Models and distributional policy gradients.

Information-geometry diagram: projecting from a Maximum-Entropy specification to an Energy-Based Model
Distributional control via Information Geometry.
Training curves showing Reinforce collapsing in BLEU-4 while CDPG maintains quality
Standard RL (Reinforce) catastrophically loses quality; CDPG satisfies the constraint while preserving it.

Selected papers

  • A Distributional Approach to Controlled Text Generation · ICLR 2021 · Oral (top 2.1%) [paper][code][blog]
  • Controlling conditional language models without catastrophic forgetting · ICML 2022 [paper][slides][code]
  • On Reinforcement Learning and Distribution Matching for Fine-Tuning Language Models with no Catastrophic Forgetting · NeurIPS 2022 [paper]
  • An Approximate Sampler for Energy-Based Models with Divergence Diagnostics · TMLR 2022 [paper]

2022 – 2024

Meta AI - FAIR

Seamless: Massively multilingual & multimodal translation

I joined the Seamless effort and worked on the Seamless Project, a single foundation model for direct speech-to-speech and speech-to-text translation across close to 100 languages. It was named one of Time's Best Inventions of 2023, and published in Nature (2025).

Excited → German
Fast talking → French
Sad → Spanish
Whispering → English

Visit the SeamlessExpressive demo for more examples, or explore all Seamless demos.

Selected papers

  • SeamlessM4T: Multilingual & Multimodal Translation · Meta AI · 2023 [blog][paper][HF]
  • Joint Speech and Text Machine Translation for up to 100 Languages · Nature · 2025 [Nature paper]

2024 – now

Meta Superintelligence Labs - FAIR

Invisible watermarking & content provenance

As voice cloning and strong image/video generators emerged, content provenance and AI-generated-media detection became urgent. I helped build a world-class research team at Meta around watermarking and content provenance, from the ground up. The team has established state-of-the-art open-source models for watermarking across audio, images, video, and text. Content Seal now watermarks content from Meta's Muse Image/Video and powers meta.ai/identification, running across the family of apps to watermark and detect AI-generated media at massive scale. I also organized the Watermarking Workshop at ICLR 2025.

Video Seal: invisible video watermarking demo
Video Seal: invisible watermarks that survive re-encoding, cropping, and edits. Header film from the Content Seal site. Try the live demo.

Selected papers

  • TextSeal: A Localized LLM Watermark for Provenance & Distillation Protection · arXiv · 2026 [arXiv][code]
  • PixelSeal: Adversarial-Only Training for Invisible Image and Video Watermarking · Meta AI · 2025 [paper][code]
  • ChunkySeal: We Can Hide More Bits, The Unused Watermarking Capacity in Theory and in Practice · arXiv · 2025 [arXiv][code]
  • VideoSeal: Open and Efficient Video Watermarking · arXiv · Dec 2024 [arXiv][code][demo]
  • AudioSeal: Proactive Detection of Voice Cloning with Localized Watermarking · ICML 2024 [paper][code][HF]