Multilingual Long-Form Speech Instruction Following: KIT’s Submission to IWSLT 2026

Enes Yavuz Ugan, Maike Züfle, Yuka Ko, Supriti Sinhamahapatra, Fabian Retkowski, Seymanur Akti, Jan Niehues, Alexander Waibel


Abstract
With the advent of Large Language Models, single-task and token-based multi-task models have evolved into instruction-based systems that infer task and target language implicitly from natural language prompts. This trend is reflected in IWSLT’s Instruction Following Track, which this year introduced new tasks including an unknown surprise task, posing a genuine challenge against overfitting to known tasks. We present KIT’s submission to the Long and Short Instruction Following tracks in the unconstrained setting. Our approach combines a general data augmentation pipeline that converts short-form corpora into long-form training data through segment concatenation, LLM-based label generation, and cross-lingual translation, yielding over 1M instances across six tasks and four languages. We further show that likelihood-based re-ranking, while highly effective for ASR, systematically degrades semantic tasks by spuriously selecting candidates generated from segmented audio processing rather than holistic long-form inference, a failure mode resolved by combining likelihood with Minimum Bayes Risk decoding.
Anthology ID:
2026.iwslt-1.16
Volume:
Proceedings of the 23rd International Conference on Spoken Language Translation (IWSLT 2026)
Month:
July
Year:
2026
Address:
San Diego, USA (in-person and online)
Editors:
Elizabeth Salesky, Antonios Anastasopoulos, Matteo Negri, Marcello Federico
Venues:
IWSLT | WS
SIG:
SIGSLT
Publisher:
Association for Computational Linguistics
Note:
Pages:
132–149
Language:
URL:
https://aclanthology.org/2026.iwslt-1.16/
DOI:
Bibkey:
Cite (ACL):
Enes Yavuz Ugan, Maike Züfle, Yuka Ko, Supriti Sinhamahapatra, Fabian Retkowski, Seymanur Akti, Jan Niehues, and Alexander Waibel. 2026. Multilingual Long-Form Speech Instruction Following: KIT’s Submission to IWSLT 2026. In Proceedings of the 23rd International Conference on Spoken Language Translation (IWSLT 2026), pages 132–149, San Diego, USA (in-person and online). Association for Computational Linguistics.
Cite (Informal):
Multilingual Long-Form Speech Instruction Following: KIT’s Submission to IWSLT 2026 (Ugan et al., IWSLT 2026)
Copy Citation:
PDF:
https://aclanthology.org/2026.iwslt-1.16.pdf