Omni-Embed-Mini: Binding Modalities Without Forgetting via Dense Distillation

Mohammed Irfan Kurpath, Jaseel Muhammad Kaithakkodan, Sahal Shaji Mullappilly, Ivan Laptev, Hisham Cholakkal


Abstract
Extending a text embedding model to new modalities typically degrades text retrieval quality, and existing omni-modal embedders compensate with multi-billion parameters. We present Omni-Embed-Mini, a 0.9B-parameter model that maps text, speech, audio, images, video, and visually-rich documents into a single shared cosine space without updating any text-side parameter. Our key insight is that the teacher signal requires no separate model: each media sample is paired with a dense cascaded caption, and the teacher target is simply the frozen backbone’s own embedding of that caption. Because teacher and student share the same backbone weights, they inhabit byte-identical geometry, and lightweight projectors plus phased LoRA adapters on the modality encoders suffice for alignment. Training combines a Matryoshka SigLIP contrastive loss with an online hybrid hard-negative miner whose negatives sharpen as the encoder improves. The recipe scales unchanged to a 2.3B variant by swapping in a native vision-language backbone. Omni-Embed-Mini-0.9B keeps its text weights bit-identical to the backbone, so training cannot regress text retrieval (49.57 nDCG@10 on MTEB-v2 BEIR-8), while extending it to five additional modalities, and is ~2.7× to 9.5× smaller than every open omni embedder we compare against. The 2.3B variant is competitive with closed API embedders, edging ahead of gemini-embedding-2 on the overall-modality average. Models, code, dataset, and evaluation harness are available on our project page: https://omniembed.cvmbzuai.com
Anthology ID:
2026.findings-emnlp.2470
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2026
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
Findings
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
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Pages:
53150–53175
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URL:
https://aclanthology.org/2026.findings-emnlp.2470/
DOI:
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Cite (ACL):
Mohammed Irfan Kurpath, Jaseel Muhammad Kaithakkodan, Sahal Shaji Mullappilly, Ivan Laptev, and Hisham Cholakkal. 2026. Omni-Embed-Mini: Binding Modalities Without Forgetting via Dense Distillation. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 53150–53175, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Omni-Embed-Mini: Binding Modalities Without Forgetting via Dense Distillation (Kurpath et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.2470.pdf