Route threaded replies through reply endpoint

[Mehak Bindra (MehakBindra)]

Summary

• add endpoint-based activity replies at POST /v3/conversations/{conversationId}/activities/{rootId}
• route proactive and context-derived channel/group thread replies without constructing ;messageid= conversation IDs
• translate legacy suffixed IDs passed to app.SendAsync() into reply-endpoint calls
• expose inbound channelData.thread.id and retain legacy suffix parsing as a compatibility fallback
• separate quoting from placement by standardizing on MessageActivityInput.AddQuote() and deprecating legacy context quote/reply conveniences without removing them
• update threading and quoting samples

Validation

• Microsoft.Teams.Core.UnitTests: 170 passed on net8.0 and net10.0
• Microsoft.Teams.Apps.UnitTests: 535 passed on net8.0 and net10.0
• updated sample projects build successfully

[azure-pipelines]

Azure Pipelines:
There may be pipelines that require an authorized user to comment /azp run to run.

[Copilot]

Pull request overview

This PR updates the SDK’s threading model to route threaded replies via the Bot Framework reply endpoint (POST /v3/conversations/{conversationId}/activities/{rootId}) rather than relying on ;messageid=-suffixed conversation IDs, and standardizes quoting via MessageActivityInput.AddQuote() while deprecating legacy convenience helpers.

Changes:

• Add ConversationClient.ReplyToActivityAsync(...) and route reply calls through the reply endpoint.
• Expose inbound channelData.thread.id and use it (plus legacy ;messageid= parsing) to determine thread roots for context-derived replies.
• Update/deprecate quoting/reply convenience APIs and refresh samples/tests accordingly.

Reviewed changes

Copilot reviewed 17 out of 17 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
test/Microsoft.Teams.Core.UnitTests/ConversationClientTests.cs	Adds unit coverage for reply-endpoint URL construction and validation.
test/Microsoft.Teams.Apps.UnitTests/TeamsChannelDataDeserializationTests.cs	Verifies deserialization of channelData.thread.id.
test/Microsoft.Teams.Apps.UnitTests/TeamsBotApplicationTests.cs	Ensures proactive replies use base conversation ID + reply endpoint.
test/Microsoft.Teams.Apps.UnitTests/PromptPreviewTests.cs	Adds coverage for context-derived thread-root selection (channel, channelData thread, legacy suffix).
src/Microsoft.Teams.Core/Schema/ConversationExtensions.cs	Updates docs and deprecates ToThreadedConversationId.
src/Microsoft.Teams.Core/ConversationClient.cs	Introduces ReplyToActivityAsync to call the reply endpoint.
src/Microsoft.Teams.Apps/TeamsBotApplication.cs	Routes proactive threaded replies via reply endpoint and validates thread root IDs.
src/Microsoft.Teams.Apps/Schema/TeamsChannelData.cs	Adds TeamsChannelDataThread model and TeamsChannelData.Thread.
src/Microsoft.Teams.Apps/Context.cs	Deprecates legacy quote/reply conveniences; adds reply-endpoint routing based on inferred thread root.
src/Microsoft.Teams.Apps/Clients/ConversationApiClient.cs	Switches reply behavior to use reply endpoint instead of setting ReplyToId.
src/Microsoft.Teams.Apps/Clients/ActivityClient.cs	Routes reply methods through ConversationClient.ReplyToActivityAsync.
samples/TargetedMessages/Program.cs	Updates sample to use AddQuote(...)+SendAsync(...) rather than ReplyAsync.
samples/M365ExtensionsBot/MyTeamsBot.cs	Updates quoting sample to explicit AddQuote usage.
samples/InteractingWithMessagesBot/ThreadingHandlers.cs	Demonstrates direct use of reply endpoint and channelData.thread.id fallback.
samples/InteractingWithMessagesBot/README.md	Refreshes docs to reflect explicit quoting and reply-endpoint threading.
samples/InteractingWithMessagesBot/QuotingHandlers.cs	Updates quoting handlers to use AddQuote + SendAsync.
samples/InteractingWithMessagesBot/Program.cs	Updates CLI/help text to match explicit-quote semantics.

Suppressed comments (2)

src/Microsoft.Teams.Apps/TeamsBotApplication.cs:335

• Reply() strips the conversation ID via conversationId.Split(';')[0], which removes everything after the first ; (not specifically the legacy ;messageid= suffix) and is case-sensitive. Strip only the ;messageid= marker (case-insensitive) and pass that base ID into ReplyToActivityAsync.

        return ConversationClient.ReplyToActivityAsync(
            conversationId.Split(';')[0],
            messageId,

src/Microsoft.Teams.Core/Schema/ConversationExtensions.cs:32

• This method is now marked obsolete with guidance about legacy ;messageid= suffixes, but it currently strips the base ID by splitting on any ;. Consider stripping only the legacy ;messageid= marker (case-insensitive) so other semicolon-delimited suffixes are preserved.

    [Obsolete("Thread placement is endpoint-based. Use the base conversation ID with ReplyToActivityAsync instead.")]
    public static string ToThreadedConversationId(string conversationId, string messageId)
    {
        if (string.IsNullOrEmpty(conversationId))

---

💡 Add a code-review agent skill or configure MCP servers for context-aware, tailored reviews. Learn more in the docs.