Translating the Translator: Decomposing the Cost of English-Forced Inter-Agent Communication

Kushagra Agrawal, Yuming Feng, Man-Fai Leung


Abstract
Multi-agent LLM architectures, such as LangChain and AutoGen, largely assume English as the lingua franca for internal inter-agent communication, even when the end-user task is non-English. We fill this gap by evaluating a two-agent extraction-answer core, with an additional back-translation agent in the English-forced condition, across four typologically diverse languages (Hindi, Chinese, Spanish, Arabic; n=300 per language) using the Aya-23-8B model. We compare a native-language pipeline to an English-forced one (which incorporates a final back-translation step from English to the user’s language). We discover a statistically significant English-Forcing Tax (surviving a strict Bonferroni correction) that isolates the cost of English routing from general multi-agent orchestration overhead. Forcing inter-agent communication through English reduces Exact Match accuracy by 13.0 percentage points (Spanish) up to 30.6 percentage points (Hindi) compared to native-language multi-agent execution. Using chrF scores as a diagnostic measure of English-reference lexical overlap, we find that lower overlap is strongly associated with pipeline failure, consistent with translation loss being an important contributor to the observed performance drop. These findings suggest a compelling case for native-language routing in agent frameworks when the source and target languages are typologically distant, reducing a compounding translation tax.
Anthology ID:
2026.realm-1.32
Volume:
Proceedings of the Second Workshop for REsearch on Agent Language Models (REALM 2026)
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Ehsan Kamalloo, Nicolas Gontier, Nikolai Rozanov, Maryam Hashemzadeh, Akhil Arora
Venues:
REALM | WS
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
473–483
Language:
URL:
https://aclanthology.org/2026.realm-1.32/
DOI:
Bibkey:
Cite (ACL):
Kushagra Agrawal, Yuming Feng, and Man-Fai Leung. 2026. Translating the Translator: Decomposing the Cost of English-Forced Inter-Agent Communication. In Proceedings of the Second Workshop for REsearch on Agent Language Models (REALM 2026), pages 473–483, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Translating the Translator: Decomposing the Cost of English-Forced Inter-Agent Communication (Agrawal et al., REALM 2026)
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PDF:
https://aclanthology.org/2026.realm-1.32.pdf