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Answer in the Language They Wrote In
The rule is one line and almost everybody gets the exception wrong. Detection from the message rather than the profile, what happens with Russian typed in Latin letters, and the one case where the reply changes language on purpose.
Costa4 min read
Short answer
Reply in the language of the message, detected from the message itself rather than from a profile, a phone prefix or a country. The exception is the handover: when a conversation goes to a person who does not read that language, the customer should be told which language the reply will arrive in rather than discovering it. Contracts and legal documents stay in their own language regardless of the conversation.
Key facts
- The assistant answers in the language a message was written in, across sixteen languages.
- Detection reads the message, not the profile, the phone prefix or the country.
- A conversation is handed to a person with the thread in its original language and a summary in the language the person reads.
- Contracts, terms and invoices stay in their governing language, whatever language the conversation is in.
The rule fits in one line: reply in the language the message was written in. Almost everybody agrees with it and a surprising number of systems break it within a week, always in the same two places.
Detect from the message, not the profile
A phone prefix says where a number was issued. A country says where somebody is standing. A profile language says what a person once selected in an app, possibly years ago, possibly because the app defaulted to it.
None of them says what language this message is in, and each of them will confidently disagree with the message several times a week. A German number belonging to a Turkish speaker who is on holiday in Spain and typed a sentence in English is not an edge case; it is a Tuesday. Read the text.
Latin letters, Russian words
The case that breaks naive detection is the message that is written in one language and typed in another alphabet.
Somebody writes Russian in Latin characters. Somebody writes Greek the same way. Somebody mixes English syntax with a local noun for a specific document because there is no English word for it. A system matching character sets will get all three wrong, and the reply that comes back in the wrong language is worse than a slow one, because it reads as not having been read at all.
The correct behaviour on a mixed message is to answer in the dominant language and leave the borrowed term exactly as the customer wrote it. They will be saying that word at a counter later, and translating it helps nobody.
The one case where the language changes
Handover.
An assistant answering in sixteen languages can hand a conversation to a team that reads three. That is a normal state of affairs and not a defect, and how it is handled decides what the customer thinks of the whole exchange.
What must not happen is silence followed by a reply in a language the customer did not choose. What should happen is one sentence before the transfer: a named person is taking this, they will answer in English, here is when. Told in advance it is a logistics detail. Discovered afterwards it reads as having been moved somewhere that does not deal with people like you.
The record and the summary are not the same thing
The thread in its original language, untouched, because that is the record. Above it, the summary in the language the person taking over actually reads.
Translating the customer's own words inside the record is a mistake that looks like helpfulness: the moment there is a dispute about what somebody agreed to, the only useful artefact is what they actually typed. Keep both, and keep them separate.
Documents do not follow the conversation
A contract stays in its governing language. So does an invoice with legal requirements attached to it, and so do terms somebody may end up standing on.
The conversation about the document happens in the customer's language, the summary of what it says happens in the customer's language, and the document itself does not move. Getting this backwards produces a translated contract that nobody can rely on, which is worse than an untranslated one everybody knows to have checked.
Sixteen is not a marketing number
It matters in exactly one situation: when the person on the other end has been typing in their second-best language all week and gets a reply in their first.
Everything above is about not spending that on a detection shortcut. Whether it is Omni AI across channels or Social AI inside a room, the mechanism is identical and the failure mode is the same one — a system that decided in advance which language you speak, and turned out to be sure about it.
Questions this raises
- Should we ask people to pick a language at the start?
- No. They picked one when they typed their message, and asking a person who has just written a clear sentence in Portuguese to select Portuguese from a menu is a small insult with a measurable cost.
- What about someone who writes in two languages at once?
- Answer in the dominant one and keep any term they used in the other. Somebody writing English with the local word for a document type wants that word to come back unchanged, not translated into something they will not recognise at the counter.
- Does the customer need to know a human is answering in another language?
- Yes, before it happens. Being told the reply will come in English is a courtesy; discovering it after waiting an hour reads as being passed to a department that does not deal with you.