Multiple AppHosts with the same port report they launch successfully at the same time

[JamesNK]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

1. Create an AppHost with aspire new
2. Copy source it to a new directory
3. Run both instances of the source code
4. Both aspire run calls report the app started successfully

I expected the second aspire run call to fail because ports are in use.

Logs 1:

[2026-03-24 08:46:07.667] [INFO] [Program] Version: 13.2.0+1b339b0aab41b049e8e0d21ed1a79596cf8b8509
[2026-03-24 08:46:07.667] [INFO] [Program] Build ID: 13.200.26.17003
[2026-03-24 08:46:07.667] [INFO] [Program] Working directory: C:\Development\Temp\cli-ts\cli-ts
[2026-03-24 08:46:07.791] [INFO] [Program] Command: aspire run
[2026-03-24 08:46:07.794] [INFO] [ProjectLocator] Found AppHost path 'cli-ts.AppHost/cli-ts.AppHost.csproj' from config file in C:\Development\Temp\cli-ts\cli-ts
[2026-03-24 08:46:08.611] [INFO] [Build]   Determining projects to restore...
[2026-03-24 08:46:09.168] [INFO] [Build]   All projects are up-to-date for restore.
[2026-03-24 08:46:09.246] [INFO] [Build] C:\Program Files\dotnet\sdk\10.0.300-preview.26156.117\Sdks\Microsoft.NET.Sdk\targets\Microsoft.NET.RuntimeIdentifierInference.targets(383,5): message NETSDK1057: You are using a preview version of .NET. See: https://aka.ms/dotnet-support-policy [C:\Development\Temp\cli-ts\cli-ts\cli-ts.AppHost\cli-ts.AppHost.csproj]
[2026-03-24 08:46:09.560] [INFO] [Build]   cli-ts.ServiceDefaults -> C:\Development\Temp\cli-ts\cli-ts\cli-ts.ServiceDefaults\bin\Debug\net10.0\cli-ts.ServiceDefaults.dll
[2026-03-24 08:46:09.608] [INFO] [Build] C:\Program Files\dotnet\sdk\10.0.300-preview.26156.117\Sdks\Microsoft.NET.Sdk\targets\Microsoft.NET.RuntimeIdentifierInference.targets(383,5): message NETSDK1057: You are using a preview version of .NET. See: https://aka.ms/dotnet-support-policy [C:\Development\Temp\cli-ts\cli-ts\cli-ts.Web\cli-ts.Web.csproj]
[2026-03-24 08:46:09.764] [INFO] [Build]   cli-ts.ApiService -> C:\Development\Temp\cli-ts\cli-ts\cli-ts.ApiService\bin\Debug\net10.0\cli-ts.ApiService.dll
[2026-03-24 08:46:09.842] [INFO] [Build]   cli-ts.Web -> C:\Development\Temp\cli-ts\cli-ts\cli-ts.Web\bin\Debug\net10.0\cli-ts.Web.dll
[2026-03-24 08:46:10.011] [INFO] [Build]   cli-ts.AppHost -> C:\Development\Temp\cli-ts\cli-ts\cli-ts.AppHost\bin\Debug\net10.0\cli-ts.AppHost.dll
[2026-03-24 08:46:10.011] [INFO] [Build] 
[2026-03-24 08:46:10.011] [INFO] [Build] Build succeeded.
[2026-03-24 08:46:10.011] [INFO] [Build]     0 Warning(s)
[2026-03-24 08:46:10.011] [INFO] [Build]     0 Error(s)
[2026-03-24 08:46:10.011] [INFO] [Build] 
[2026-03-24 08:46:10.011] [INFO] [Build] Time Elapsed 00:00:01.53
[2026-03-24 08:46:11.528] [INFO] [AppHost] Using launch settings from C:\Development\Temp\cli-ts\cli-ts\cli-ts.AppHost\Properties\launchSettings.json...
[2026-03-24 08:46:12.398] [INFO] [AppHost] info: Aspire.Hosting.DistributedApplication[0]
[2026-03-24 08:46:12.398] [INFO] [AppHost]       Aspire version: 13.3.0-preview.1.26173.7+936a01a32a5a8fd69ae90c942d7741fd57fe1efa
[2026-03-24 08:46:12.399] [INFO] [AppHost] info: Aspire.Hosting.DistributedApplication[0]
[2026-03-24 08:46:12.399] [INFO] [AppHost]       Distributed application starting.
[2026-03-24 08:46:12.399] [INFO] [AppHost] info: Aspire.Hosting.DistributedApplication[0]
[2026-03-24 08:46:12.399] [INFO] [AppHost]       Application host directory is: C:\Development\Temp\cli-ts\cli-ts\cli-ts.AppHost
[2026-03-24 08:46:12.398] [INFO] [AppHost/DistributedApplication] Aspire version: 13.3.0-preview.1.26173.7+936a01a32a5a8fd69ae90c942d7741fd57fe1efa
[2026-03-24 08:46:12.399] [INFO] [AppHost/DistributedApplication] Distributed application starting.
[2026-03-24 08:46:12.399] [INFO] [AppHost/DistributedApplication] Application host directory is: C:\Development\Temp\cli-ts\cli-ts\cli-ts.AppHost
[2026-03-24 08:46:15.027] [INFO] [AppHost] info: Aspire.Hosting.DistributedApplication[0]
[2026-03-24 08:46:15.027] [INFO] [AppHost]       Now listening on: https://localhost:17058
[2026-03-24 08:46:15.028] [INFO] [AppHost] info: Aspire.Hosting.DistributedApplication[0]
[2026-03-24 08:46:15.028] [INFO] [AppHost]       Login to the dashboard at https://localhost:17058/login?t=f368734829c71fee900ca3b091d04282
[2026-03-24 08:46:15.027] [INFO] [AppHost/DistributedApplication] Now listening on: https://localhost:17058
[2026-03-24 08:46:15.028] [INFO] [AppHost/DistributedApplication] Login to the dashboard at https://localhost:17058/login?t=f368734829c71fee900ca3b091d04282
[2026-03-24 08:46:18.641] [INFO] [AppHost] info: Aspire.Hosting.DistributedApplication[0]
[2026-03-24 08:46:18.641] [INFO] [AppHost]       Distributed application started. Press Ctrl+C to shut down.
[2026-03-24 08:46:18.641] [INFO] [AppHost/DistributedApplication] Distributed application started. Press Ctrl+C to shut down.

Logs 2:

[2026-03-24 08:46:39.865] [INFO] [Program] Version: 13.2.0+1b339b0aab41b049e8e0d21ed1a79596cf8b8509
[2026-03-24 08:46:39.865] [INFO] [Program] Build ID: 13.200.26.17003
[2026-03-24 08:46:39.865] [INFO] [Program] Working directory: C:\Development\Temp\cli-ts\cli-ts-copy
[2026-03-24 08:46:39.981] [INFO] [Program] Command: aspire run
[2026-03-24 08:46:41.712] [INFO] [Build]   Determining projects to restore...
[2026-03-24 08:46:42.303] [INFO] [Build]   Restored C:\Development\Temp\cli-ts\cli-ts-copy\cli-ts.ApiService\cli-ts.ApiService.csproj (in 75 ms).
[2026-03-24 08:46:42.303] [INFO] [Build]   Restored C:\Development\Temp\cli-ts\cli-ts-copy\cli-ts.ServiceDefaults\cli-ts.ServiceDefaults.csproj (in 74 ms).
[2026-03-24 08:46:42.303] [INFO] [Build]   Restored C:\Development\Temp\cli-ts\cli-ts-copy\cli-ts.Web\cli-ts.Web.csproj (in 75 ms).
[2026-03-24 08:46:42.380] [INFO] [Build]   Restored C:\Development\Temp\cli-ts\cli-ts-copy\cli-ts.AppHost\cli-ts.AppHost.csproj (in 156 ms).
[2026-03-24 08:46:42.458] [INFO] [Build] C:\Program Files\dotnet\sdk\10.0.300-preview.26156.117\Sdks\Microsoft.NET.Sdk\targets\Microsoft.NET.RuntimeIdentifierInference.targets(383,5): message NETSDK1057: You are using a preview version of .NET. See: https://aka.ms/dotnet-support-policy [C:\Development\Temp\cli-ts\cli-ts-copy\cli-ts.AppHost\cli-ts.AppHost.csproj]
[2026-03-24 08:46:42.896] [INFO] [Build] C:\Program Files\dotnet\sdk\10.0.300-preview.26156.117\Sdks\Microsoft.NET.Sdk\targets\Microsoft.NET.RuntimeIdentifierInference.targets(383,5): message NETSDK1057: You are using a preview version of .NET. See: https://aka.ms/dotnet-support-policy [C:\Development\Temp\cli-ts\cli-ts-copy\cli-ts.Web\cli-ts.Web.csproj]
[2026-03-24 08:46:43.100] [INFO] [Build]   cli-ts.ServiceDefaults -> C:\Development\Temp\cli-ts\cli-ts-copy\cli-ts.ServiceDefaults\bin\Debug\net10.0\cli-ts.ServiceDefaults.dll
[2026-03-24 08:46:43.749] [INFO] [Build]   cli-ts.ApiService -> C:\Development\Temp\cli-ts\cli-ts-copy\cli-ts.ApiService\bin\Debug\net10.0\cli-ts.ApiService.dll
[2026-03-24 08:46:44.015] [INFO] [Build]   cli-ts.Web -> C:\Development\Temp\cli-ts\cli-ts-copy\cli-ts.Web\bin\Debug\net10.0\cli-ts.Web.dll
[2026-03-24 08:46:44.460] [INFO] [Build]   cli-ts.AppHost -> C:\Development\Temp\cli-ts\cli-ts-copy\cli-ts.AppHost\bin\Debug\net10.0\cli-ts.AppHost.dll
[2026-03-24 08:46:44.460] [INFO] [Build] 
[2026-03-24 08:46:44.460] [INFO] [Build] Build succeeded.
[2026-03-24 08:46:44.460] [INFO] [Build]     0 Warning(s)
[2026-03-24 08:46:44.460] [INFO] [Build]     0 Error(s)
[2026-03-24 08:46:44.460] [INFO] [Build] 
[2026-03-24 08:46:44.460] [INFO] [Build] Time Elapsed 00:00:02.88
[2026-03-24 08:46:46.038] [INFO] [AppHost] Using launch settings from C:\Development\Temp\cli-ts\cli-ts-copy\cli-ts.AppHost\Properties\launchSettings.json...
[2026-03-24 08:46:48.098] [INFO] [AppHost] info: Aspire.Hosting.DistributedApplication[0]
[2026-03-24 08:46:48.098] [INFO] [AppHost]       Aspire version: 13.3.0-preview.1.26173.7+936a01a32a5a8fd69ae90c942d7741fd57fe1efa
[2026-03-24 08:46:48.099] [INFO] [AppHost] info: Aspire.Hosting.DistributedApplication[0]
[2026-03-24 08:46:48.099] [INFO] [AppHost]       Distributed application starting.
[2026-03-24 08:46:48.099] [INFO] [AppHost] info: Aspire.Hosting.DistributedApplication[0]
[2026-03-24 08:46:48.099] [INFO] [AppHost]       Application host directory is: C:\Development\Temp\cli-ts\cli-ts-copy\cli-ts.AppHost
[2026-03-24 08:46:48.098] [INFO] [AppHost/DistributedApplication] Aspire version: 13.3.0-preview.1.26173.7+936a01a32a5a8fd69ae90c942d7741fd57fe1efa
[2026-03-24 08:46:48.099] [INFO] [AppHost/DistributedApplication] Distributed application starting.
[2026-03-24 08:46:48.099] [INFO] [AppHost/DistributedApplication] Application host directory is: C:\Development\Temp\cli-ts\cli-ts-copy\cli-ts.AppHost
[2026-03-24 08:46:50.671] [INFO] [AppHost] info: Aspire.Hosting.DistributedApplication[0]
[2026-03-24 08:46:50.671] [INFO] [AppHost]       Now listening on: https://localhost:17058
[2026-03-24 08:46:50.671] [INFO] [AppHost] info: Aspire.Hosting.DistributedApplication[0]
[2026-03-24 08:46:50.672] [INFO] [AppHost]       Login to the dashboard at https://localhost:17058/login?t=52703193be635e42b0bf80ffd59b375d
[2026-03-24 08:46:50.671] [INFO] [AppHost/DistributedApplication] Now listening on: https://localhost:17058
[2026-03-24 08:46:50.671] [INFO] [AppHost/DistributedApplication] Login to the dashboard at https://localhost:17058/login?t=52703193be635e42b0bf80ffd59b375d
[2026-03-24 08:46:54.388] [INFO] [AppHost] info: Aspire.Hosting.DistributedApplication[0]
[2026-03-24 08:46:54.388] [INFO] [AppHost]       Distributed application started. Press Ctrl+C to shut down.
[2026-03-24 08:46:54.388] [INFO] [AppHost/DistributedApplication] Distributed application started. Press Ctrl+C to shut down.

Expected Behavior

No response

Steps To Reproduce

No response

Exceptions (if any)

No response

.NET Version info

No response

Anything else?

No response

[MihuBot]

I'm a bot. Here is a possible related and/or duplicate issue (I may be wrong):

• Aspire dashboard sometimes doesn't start but the app host boots successfully #2198