[AspireE2E][Aspire CLI]An unexpected error occurred: The JSON-RPC connection with the remote party was lost before the request could complete when dotnet watch on Aspire AppHost project

[jinzhao1127]

INSTALL STEPS

1. Clean machine: Win11 x64 23h2 ENU
2. Install SDK 10.0.102
3. Install Aspire.Cli 13.1.0 iex "& { $(irm https://aspire.dev/install.ps1) }"
4. Enable the hot reload feature in aspire CLI with aspire config set features.defaultWatchEnabled true

REPRO STEPS

1. Open CMD and create an Aspire Starter App (ASP.NET Core/Blazor)

    dotnet new aspire-starter -o aspire01
    cd aspire01/aspire01.AppHost
   

2. Run aspire run
3. Open the URL on browser.
4. Open AppHost.cs file under xxx.AppHost, and add code .WithReplicas(2); then save the file.
   

ACTUAL
The process is shut down and An unexpected error occurred: The JSON-RPC connection with the remote party was lost before the request could complete.

Note:

1. This issue does not reproduce on Web project and ApiService project

ERROR LOG

❌ An unexpected error occurred: The JSON-RPC connection with the remote party was lost before the request
could complete.
dotnet watch 🔥 Hot reload enabled. For a list of supported edits, see https://aka.ms/dotnet/hot-reload.
dotnet watch 💡 Press Ctrl+R to restart.
dotnet watch 🔨 Building C:\Users\v-zhajin\Aspire2\Aspire2.Apphost\Aspire2.AppHost.csproj ...
dotnet watch 🔨 Build succeeded: C:\Users\v-zhajin\Aspire2\Aspire2.Apphost\Aspire2.AppHost.csproj
Using launch settings from C:\Users\v-zhajin\Aspire2\Aspire2.Apphost\Properties\launchSettings.json...
info: Aspire.Hosting.DistributedApplication[[0]]
      Aspire version: 13.2.0-preview.1.26064.8+12d27ad489e97bcfa37c074f3fa310643c8dc7f7
info: Aspire.Hosting.DistributedApplication[[0]]
      Distributed application starting.
info: Aspire.Hosting.DistributedApplication[[0]]
      Application host directory is: C:\Users\v-zhajin\Aspire2\Aspire2.Apphost
info: Aspire.Hosting.DistributedApplication[[0]]
      Now listening on: https://localhost:17017
info: Aspire.Hosting.DistributedApplication[[0]]
      Login to the dashboard at https://localhost:17017/login?t=2aac32108ba777016e1172b8cca5c35e
info: Aspire.Hosting.DistributedApplication[[0]]
      Distributed application started. Press Ctrl+C to shut down.
dotnet watch ⌚ File updated: .\AppHost.cs
dotnet watch 🔥 Restart is needed to apply the changes.
dotnet watch ⌚ [[Aspire2.ApiService (net10.0)]] Exited
dotnet watch ⌚ [[Aspire2.Web (net10.0)]] Exited

EXPECTED
The hot reload should be successfully or restart the app automatically.

[jinzhao1127]

@davidfowl , this is about the aspire hot reload when aspire run, could you take a look?

[balachir]

@jinzhao1127 does this happen with Aspire Starter App only when you have .WithReplicas(2) in the app host?

[jinzhao1127]

@jinzhao1127 does this happen with Aspire Starter App only when you have .WithReplicas(2) in the app host?

@balachir Yes, this issue only occurs when adding .WithReplicas(2) in the app host. for now the error change to below:

When I editing the .razor/.css file for Aspire.Web project, it works well
When I editing program.cs file in Aspire.ApiService project, it works well.

Details log

[2026-02-10 02:40:52.429] [INFO] [Program] Command: aspire run
[2026-02-10 02:40:52.429] [INFO] [Program] Working directory: C:\Users\v-zhajin\aspire01\aspire01.AppHost
[2026-02-10 02:40:55.075] [FAIL] [AppHost] dotnet watch 🔥 Hot reload enabled. For a list of supported edits, see https://aka.ms/dotnet/hot-reload.
[2026-02-10 02:40:55.075] [FAIL] [AppHost] dotnet watch 💡 Press Ctrl+R to restart.
[2026-02-10 02:40:55.077] [FAIL] [AppHost] dotnet watch 🔨 Building C:\Users\v-zhajin\aspire01\aspire01.AppHost\aspire01.AppHost.csproj ...
[2026-02-10 02:41:02.796] [FAIL] [AppHost] dotnet watch 🔨 Build succeeded: C:\Users\v-zhajin\aspire01\aspire01.AppHost\aspire01.AppHost.csproj
[2026-02-10 02:41:05.827] [INFO] [AppHost] Using launch settings from C:\Users\v-zhajin\aspire01\aspire01.AppHost\Properties\launchSettings.json...
[2026-02-10 02:41:09.313] [INFO] [AppHost] info: Aspire.Hosting.DistributedApplication[0]
[2026-02-10 02:41:09.313] [INFO] [AppHost]       Aspire version: 13.2.0-preview.1.26109.3+c900804cf27eaac8216e471802fd443e15d9e5dc
[2026-02-10 02:41:09.314] [INFO] [AppHost] info: Aspire.Hosting.DistributedApplication[0]
[2026-02-10 02:41:09.314] [INFO] [AppHost]       Distributed application starting.
[2026-02-10 02:41:09.314] [INFO] [AppHost] info: Aspire.Hosting.DistributedApplication[0]
[2026-02-10 02:41:09.314] [INFO] [AppHost]       Application host directory is: C:\Users\v-zhajin\aspire01\aspire01.AppHost
[2026-02-10 02:41:09.313] [INFO] [AppHost/Aspire.Hosting.DistributedApplication] Aspire version: 13.2.0-preview.1.26109.3+c900804cf27eaac8216e471802fd443e15d9e5dc
[2026-02-10 02:41:09.314] [INFO] [AppHost/Aspire.Hosting.DistributedApplication] Distributed application starting.
[2026-02-10 02:41:09.314] [INFO] [AppHost/Aspire.Hosting.DistributedApplication] Application host directory is: C:\Users\v-zhajin\aspire01\aspire01.AppHost
[2026-02-10 02:41:11.473] [INFO] [AppHost] info: Aspire.Hosting.DistributedApplication[0]
[2026-02-10 02:41:11.473] [INFO] [AppHost]       Now listening on: https://localhost:17003
[2026-02-10 02:41:11.474] [INFO] [AppHost] info: Aspire.Hosting.DistributedApplication[0]
[2026-02-10 02:41:11.474] [INFO] [AppHost]       Login to the dashboard at https://localhost:17003/login?t=d2b6a3a4a4b46c45586ff1059d14be5c
[2026-02-10 02:41:11.473] [INFO] [AppHost/Aspire.Hosting.DistributedApplication] Now listening on: https://localhost:17003
[2026-02-10 02:41:11.473] [INFO] [AppHost/Aspire.Hosting.DistributedApplication] Login to the dashboard at https://localhost:17003/login?t=d2b6a3a4a4b46c45586ff1059d14be5c
[2026-02-10 02:41:15.436] [INFO] [AppHost] info: Aspire.Hosting.DistributedApplication[0]
[2026-02-10 02:41:15.436] [INFO] [AppHost]       Distributed application started. Press Ctrl+C to shut down.
[2026-02-10 02:41:15.436] [INFO] [AppHost/Aspire.Hosting.DistributedApplication] Distributed application started. Press Ctrl+C to shut down.
[2026-02-10 02:41:35.741] [FAIL] [AppHost] dotnet watch ⌚ File updated: C:\Users\v-zhajin\aspire01\aspire01.Web\Components\Pages\Home.razor
[2026-02-10 02:41:36.670] [FAIL] [AppHost] dotnet watch 🔥 [aspire01.AppHost (net10.0)] Hot reload succeeded.
[2026-02-10 02:41:36.670] [FAIL] [AppHost] dotnet watch 🔥 [aspire01.ApiService (net10.0)] Hot reload succeeded.
[2026-02-10 02:41:36.919] [FAIL] [AppHost] dotnet watch 🔥 [aspire01.Web (net10.0)] Hot reload succeeded.
[2026-02-10 02:41:47.941] [FAIL] [AppHost] dotnet watch ⌚ File updated: C:\Users\v-zhajin\aspire01\aspire01.Web\Components\Pages\Home.razor
[2026-02-10 02:41:48.035] [FAIL] [AppHost] dotnet watch 🔥 [aspire01.ApiService (net10.0)] Hot reload succeeded.
[2026-02-10 02:41:48.035] [FAIL] [AppHost] dotnet watch 🔥 [aspire01.AppHost (net10.0)] Hot reload succeeded.
[2026-02-10 02:41:48.188] [FAIL] [AppHost] dotnet watch 🔥 [aspire01.Web (net10.0)] Hot reload succeeded.
[2026-02-10 02:42:09.324] [FAIL] [AppHost] dotnet watch ⌚ File updated: .\AppHost.cs
[2026-02-10 02:42:09.443] [FAIL] [AppHost] dotnet watch 🔥 Restart is needed to apply the changes.
[2026-02-10 02:42:09.530] [FAIL] [AppHost] dotnet watch ⌚ [aspire01.ApiService (net10.0)] Exited
[2026-02-10 02:42:14.465] [FAIL] [AppHost] dotnet watch ❌ [aspire01.Web (net10.0)] Exited with error code -1
[2026-02-10 02:42:14.523] [FAIL] [AspireCliTelemetry] An unexpected error occurred: The JSON-RPC connection with the remote party was lost before the request could complete.
StreamJsonRpc.ConnectionLostException: The JSON-RPC connection with the remote party was lost before the request could complete.
   at StreamJsonRpc.JsonRpc.<InvokeCoreAsync>d__170.MoveNext() + 0x80c
--- End of stack trace from previous location ---
   at StreamJsonRpc.JsonRpc.<InvokeCoreAsync>d__159`1.MoveNext() + 0x6e
--- End of stack trace from previous location ---
   at StreamJsonRpc.Reflection.MessageFormatterEnumerableTracker.AsyncEnumerableProxy`1.AsyncEnumeratorProxy.<MoveNextAsync>d__12.MoveNext() + 0x383
--- End of stack trace from previous location ---
   at Aspire.Cli.Backchannel.AppHostCliBackchannel.<EnumerateWithReconnect>d__15`1.MoveNext() + 0x21f
--- End of stack trace from previous location ---
   at Aspire.Cli.Backchannel.AppHostCliBackchannel.<EnumerateWithReconnect>d__15`1.MoveNext() + 0x3fc
--- End of stack trace from previous location ---
   at Aspire.Cli.Backchannel.AppHostCliBackchannel.<GetAppHostLogEntriesAsync>d__13.MoveNext() + 0x72a
--- End of stack trace from previous location ---
   at Aspire.Cli.Backchannel.AppHostCliBackchannel.<GetAppHostLogEntriesAsync>d__13.MoveNext() + 0xb2b
--- End of stack trace from previous location ---
   at Aspire.Cli.Commands.RunCommand.<CaptureAppHostLogsAsync>d__23.MoveNext() + 0x17e
--- End of stack trace from previous location ---
   at Aspire.Cli.Commands.RunCommand.<CaptureAppHostLogsAsync>d__23.MoveNext() + 0x85c
--- End of stack trace from previous location ---
   at Aspire.Cli.Commands.RunCommand.<ExecuteAsync>d__19.MoveNext() + 0x379
[2026-02-10 02:42:14.525] [INFO] [Program] Exit code: 2
[2026-02-10 02:42:14.590] [FAIL] [AppHost] dotnet watch ⌚ [aspire01.AppHost (net10.0)] Exited