long tail is not working in MS teams for non English languages

Ivascu, Raluca-Diana 0 Reputation points
2026-04-23T07:08:27.45+00:00

Hello,

I have a copilot studio agent deployed in MS Teams . As knowledge sources integrated I use SharePoint sites as primarily sources for the generative answers , and in the long tail we have a flow that is triggering a function app for crawling some internal knowledge tool. Since couple of days we noticed - in MS Teams - that the long tail is not working anymore , instead an error is displayed . It is properly working for English language, but when I switch the language in MS Teams , as the agent is supposed to offer multi language support- the error message is there . If I try to reproduce the same issue in Copilot Studio - changing the language - I don't have the same issue .

So the issue seems to be only in MS Teams.

Any thoughts? does anyone did encounter a similar issue?

Microsoft Copilot | Other
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  1. AI answer

    2026-04-23T07:08:42.7633333+00:00

    The behavior is consistent with language-support limitations rather than a Teams-only configuration issue.

    Key points from the available information:

    1. Microsoft 365 Copilot and Copilot Studio do not support all UI languages for prompts and responses. The UI in Teams can be set to many languages, but Copilot features work only with a subset of languages.
    2. When a prompt or operation uses a language that is not supported, Copilot can return an error instead of a normal response. This is explicitly documented for Microsoft 365 Copilot: unsupported languages cause an error message and require switching to a supported language.
    3. Copilot Studio real-time/voice and AI-based features are only formally validated for a limited set of languages. Other languages may technically work but are not guaranteed to behave correctly and must be thoroughly tested before production.
    4. The list of supported prompt/response languages for Microsoft 365 Copilot is fixed and smaller than the list of UI languages. If Teams is switched to a language outside that supported list, long-tail behavior (including flows calling external services) can fail even if the same scenario appears to work in the Copilot Studio design/test surface.

    Given that:

    • The long-tail flow works in English in Teams.
    • The same agent and long-tail flow work in Copilot Studio when changing language.
    • The failure occurs only in Teams when using non‑English languages.

    The most likely cause is that the language selected in Teams is not one of the languages officially supported for prompts/responses in the Copilot runtime path that executes inside Teams, or that the language is not yet fully validated for the specific AI/long-tail feature path being used.

    Recommended actions:

    1. Verify that the language used in Teams is in the list of supported prompt/response languages for Microsoft 365 Copilot (for example: English (US/UK), Spanish, French, German, Italian, Portuguese (Brazil/Portugal), Japanese, etc.). If it is not listed, switch Teams to a supported language and retest.
    2. If using a language that is technically supported by Copilot Studio but not listed as formally supported/validated for the runtime scenario, treat it as experimental and test thoroughly. For production, keep Teams in one of the formally supported languages until Microsoft adds full support.
    3. If the language is on the supported list and the issue persists only in Teams, collect the exact error message and open a support case, as this may indicate a regression or a service-side issue in the Teams integration path rather than in the agent or flow itself.

    References:

    AI-generated content may be incorrect. Read our transparency notes for more information.

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