AlignAtt4LLM: Fast AlignAtt for Decoder-Only LLMs at IWSLT 2026 Simultaneous Speech Translation Task
Abstract
We describe AlignAtt4LLM, an IWSLT 2026 simultaneous speech translation system for English to German, Italian, and Chinese. The system is a synchronous cascade: Qwen3-ASR with forced alignment produces an incrementally updated source transcript, and Gemma-4 E4B-it translates that prefix under an MT-side AlignAtt policy. To our knowledge, this is the first application of AlignAtt to a decoder-only LLM, where the encoder-decoder cross-attention used by earlier AlignAtt systems is absent. We recover a usable policy by proposing (1) an explicit source span in the prompt, (2) offline selection of translation-specific alignment heads, (3) selective qk-fast replay of the draft-to-source attention block, and (4) runtime query/key capture that preserves model outputs bit-identically. On the IWSLT 2026 development set, AlignAtt4LLM outperforms the supplied baselines for the European target languages, English to German and English to Italian, in both the low-latency regime around 2 seconds and the high-latency regime below 4 seconds CU-LongYAAL. Results for English to Chinese are more mixed, but the method is not tied to Gemma-4: because AlignAtt4LLM only requires a deterministic prompt layout, calibrated attention heads, and query/key capture, the same policy can be reapplied to stronger translation-focused decoder-only MT backbones for non-European target languages.- Anthology ID:
- 2026.iwslt-1.32
- Volume:
[Proceedings of the 23rd International Conference on Spoken Language Translation (IWSLT 2026)](/volumes/2026.iwslt-1/)- Month:
- July
- Year:
- 2026
- Address:
- San Diego, USA (in-person and online)
- Editors:
Elizabeth Salesky,Antonios Anastasopoulos,Matteo Negri,Marcello Federico- Venues:
[IWSLT](/venues/iwslt/)|[WS](/venues/ws/)- SIG:
[SIGSLT](/sigs/sigslt/)- Publisher:
- Association for Computational Linguistics
- Note:
- Pages:
- 284–295
- Language:
- URL:
[https://aclanthology.org/2026.iwslt-1.32/](https://aclanthology.org/2026.iwslt-1.32/)- DOI:
- Cite (ACL):
- Quentin Fuxa and Dominik Macháček. 2026. AlignAtt4LLM: Fast AlignAtt for Decoder-Only LLMs at IWSLT 2026 Simultaneous Speech Translation Task. InProceedings of the 23rd International Conference on Spoken Language Translation (IWSLT 2026), pages 284–295, San Diego, USA (in-person and online). Association for Computational Linguistics. - Cite (Informal):
[AlignAtt4LLM: Fast AlignAtt for Decoder-Only LLMs at IWSLT 2026 Simultaneous Speech Translation Task](https://aclanthology.org/2026.iwslt-1.32/)(Fuxa & Macháček, IWSLT 2026)- PDF:
[https://aclanthology.org/2026.iwslt-1.32.pdf](https://aclanthology.org/2026.iwslt-1.32.pdf)