Bug Description

When using ctx.sign_in() with microsoft-teams-apps in a personal chat, the SDK indicates the sign-in prompt was sent, but no OAuth button/card appears in Teams.

Backend logs show Token Service calls succeed (GetSignInResource 200, activity post accepted), yet user never sees a usable prompt and cannot complete native sign-in.

In our testing, fallback magic-code flow (explicit sign-in link + pasted 6-digit code) works reliably, which suggests the issue is in native OAuth prompt/token-exchange handling path.

Tech Details

• SDK: microsoft-teams-apps (alpha line in use)
• OS: macOS (Darwin 25.1.0)
• Bot type: Teams bot, personal scope
• Flow used:
  • await ctx.sign_in()
  • @app.event("sign_in") handler present
• Observed backend sequence:
  • GET /api/usertoken/GetToken -> 404 (expected when signed out)
  • GET /api/botsignin/GetSignInResource -> 200
  • POST /v3/conversations/.../activities -> 202 Accepted
  • App log: native sign_in prompted user
  • No prompt/button visible in Teams client

Steps to Reproduce

Create a minimal bot with:

• @app.on_message calling await ctx.sign_in() when not ctx.is_signed_in
• @app.event("sign_in") handler
  Install app in Teams personal scope.
  Ensure user is signed out (ctx.sign_out()), then send hi.
  Observe backend logs and client UI.

Expected Behavior

• Teams shows OAuth prompt/button/card for user to authenticate.
• On completion, app receives sign_in callback and token is available.

Actual Behavior

• Backend indicates sign-in prompt was requested/sent.
• No prompt/button/card appears in Teams UI.
• No successful sign-in callback.
• In comparable test path, Teams emits signin/failure (resourcematchfailed), but native app flow does not provide a clear first-class failure surface.

SDK Version

3.13.12

Python Version

2.0.0a10

Additional Context

No response