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Using Activity.ChannelId to conditionally format responses in Teams vs. Copilot app

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Posted on by mnamvar

I've built a Copilot Studio agent deployed to both Microsoft Teams (DM) and the Copilot app. The default citation format renders beautifully in the Copilot app but shows as raw [turn1doc12] style tags in Teams DM, which is a bad experience for users.

I want to detect which channel the user is on and conditionally apply different formatting instructions. I tried resolving ${Activity.ChannelId} in the behavior prompt but Cliff confirmed it comes through as a literal string, not a resolved value.

My setup: GPT-5.5 Chat, SharePoint/OneDrive/Teams/Mail MCP tools connected.

Questions:

Can Activity.ChannelId be captured in a topic at conversation start and stored as a variable Cliff can reference?

If yes, can that variable conditionally affect response formatting?

Is there a better approach entirely?

CItation format i...

Citation format i...

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Building Copilot Studio chatbots in Microsoft Teams

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sannavajjala87 515 Super User 2026 Season 1 on at

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Hi,

what you’re trying to do is conceptually right, but not fully supported in the new agent experience today. While Activity.ChannelId is part of the underlying activity context, it isn’t reliably resolved inside behavior prompts (which is why you’re seeing it as a literal string), and in practice it’s also not exposed in a way that Cliff/instructions can dynamically branch on during response generation.
In theory, you can capture System.Activity.ChannelId inside a topic at runtime and store it in a variable (this is a known pattern for channel-aware behavior), but the limitation is that those topic variables don’t influence the behavior prompt or model formatting decisions directly, so you can’t use them to conditionally change citation formatting at the instruction level.
Given that, most people end up using workarounds instead of true channel detection in prompts. The more reliable approaches today are: (1) handle formatting after generation (e.g., using System.Response.FormattedText + custom citation rendering), (2) normalize output so it works acceptably in both channels, or (3) apply post-processing via topics like OnGeneratedResponse or OnPlanComplete where you can reshape citations into links or plain text depending on what renders correctly in Teams.
So overall: capturing the channel is possible at the topic level, but using it to dynamically drive formatting in the new Copilot response pipeline isn’t fully wired yet, which is why you’re hitting that gap.

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mnamvar 4 on at

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Thanks, that's the confirmation I needed. We ended up implementing a normalized citation format that works in both channels. Appreciate the thorough explanation.

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