Cross-Tenant Chat (ACS + Entra ID)

A minimal demo showing how a user from one tenant (Fabrikam) can chat in Azure Communication Services (ACS) hosted in another tenant (Contoso) using Microsoft Entra ID.

Features

• Cross-tenant sign-in and ACS token exchange
• Blazor Server UI (.NET 9)
• Clear tenant indicators in the chat UI
• Auto-refresh for messages and newly created threads
• Enter key sends message; button click also supported

Quick Start (no Azure setup)

Run locally in demo mode to explore the UI and flows.

dotnet restore
dotnet run

Then open the app and go to /chat. Create a thread and start messaging.

Notes

• The app no longer auto-creates a default thread; you’ll be prompted to create one.
• New threads include a couple of demo participants by email so each side can see/join when they sign in.

Run against Live Azure

Use real ACS and Entra ID resources. For full steps, see LIVE_DEPLOYMENT_GUIDE.md and Infrastructure/MANUAL_SETUP_GUIDE.md.

Prereqs

• Two tenants (Contoso = ACS host, Fabrikam = user source)
• Azure subscription and permissions to deploy

Quick path

# From repo root
cd Infrastructure
./deploy-azure-resources.ps1
./setup-app-registrations.ps1 -ContosoTenantId "<contoso-tenant-guid>" -FabrikamTenantId "<fabrikam-tenant-guid>"

# Back to app root and run
cd ..
dotnet run

Configuration

• All settings: appsettings.json (now contains production configuration)
• Useful UI options: Chat:AutoRefreshEnabled (bool), Chat:AutoRefreshIntervalMs (500–10000)

Project layout (short)

CrossTenantChat/
├─ Components/Pages/Chat.razor        # Main chat UI
├─ Services/                          # Demo + Live ACS/Auth services
├─ Infrastructure/                    # Scripts to deploy and configure Azure
├─ appsettings*.json                  # Config (includes Live)
└─ LIVE_DEPLOYMENT_GUIDE.md           # Detailed live setup

UX tips

• Press Enter to send; the send button is also available.
• Messages and the thread list auto-refresh at a short interval.

Troubleshooting (quick)

• Build locking on Windows: if CrossTenantChat.exe is in use, stop the running process and rebuild.
• Configuration: all settings are now in appsettings.json - no environment switching needed.

References

• Azure Communication Services docs: https://learn.microsoft.com/azure/communication-services/
• Entra ID + ACS quickstart (C#): https://learn.microsoft.com/azure/communication-services/quickstarts/identity/microsoft-entra-id-authentication-integration?pivots=programming-language-csharp