[Failing test]: Aspire.Cli.EndToEnd.Tests.MultipleAppHostTests.DetachFormatJsonProducesValidJson

### Is there an existing issue for this?

- [x] I have searched the existing issues

### Build information

Build: https://github.com/dotnet/aspire/actions/runs/22925166665
Build error leg or test failing: Aspire.Cli.EndToEnd.Tests.MultipleAppHostTests.DetachFormatJsonProducesValidJson
Pull Request: https://github.com/dotnet/aspire/pull/15110

### Fill in the error message template

## Error Message

Fill the error message using [step by step known issues guidance](https://github.com/dotnet/arcade/blob/main/Documentation/Projects/Build%20Analysis/KnownIssueJsonStepByStep.md).

```json
{
"ErrorMessage": "An unexpected error occurred: Expected depth to be zero at the end of the JSON payload.",
"ErrorPattern": "",
"BuildRetry": false,
"ExcludeConsoleLog": false
}
```

### Other info

- Failing job: https://github.com/dotnet/aspire/actions/runs/22925166665/job/66535776281
- Matching artifact: `logs-Cli.EndToEnd-MultipleAppHostTests-ubuntu-latest`
- Extracted TRX failure:
- `Hex1b.Automation.WaitUntilTimeoutException : WaitUntil timed out after 00:08:20 waiting for:`
- Stack trace points to `Aspire.Cli.EndToEnd.Tests.MultipleAppHostTests.DetachFormatJsonProducesValidJson()` in `tests/Aspire.Cli.EndToEnd.Tests/MultipleAppHostTests.cs:128`
- Test duration: `00:09:13.2227639`
- Artifact recording: `testresults/recordings/DetachFormatJsonProducesValidJson.cast`
- CiInsights currently reports this test as `broken` over the last 180 days with `29/29` failures and `0` passes.

### Full captured test output

Source artifact: `logs-Cli.EndToEnd-MultipleAppHostTests-ubuntu-latest`

TRX StdOut

```text
Temporary workspace created at: /tmp/Aspire.Cli.Tests/TemporaryWorkspaces/813fec7d-ce9f-4c83-a94b-6ffefdf68144
```

TRX ErrorInfo.Message

```text
Hex1b.Automation.WaitUntilTimeoutException : WaitUntil timed out after 00:08:20 waiting for: snapshot =>
{
var successPromptSearcher = new CellPatternSearcher()
.FindPattern(counter.Value.ToString())
.RightText(" OK] $ ");

var result = successPromptSearcher.Search(snapshot);
return result.Count > 0;
}
at Hex1bTestHelpers.cs:92
Terminal (160x48, cursor at 13,5, normal screen):
[10 OK] $ aspire run --detach --format json > output.json
DOTNET_DbgEnableMiniDump is set and the createdump binary does not exist: createdump
\ud83d\udd0d Finding apphosts...
❌ An unexpected error occurred: Expected depth to be zero at the end of the JSON payload. There is an open JSON object or array that should be closed.
LineNumber: 1 | BytePositionInLine: 0.
[11 ERR:1] $

```

TRX StackTrace

```text
at Hex1b.Automation.WaitUntilStep.ExecuteAsync(Hex1bTerminal terminal, Hex1bTerminalInputSequenceOptions options, CancellationToken ct) in /home/runner/work/hex1b/hex1b/src/Hex1b/Automation/WaitUntilStep.cs:line 39
at Hex1b.Automation.Hex1bTerminalInputSequence.ApplyAsync(Hex1bTerminal terminal, CancellationToken ct) in /home/runner/work/hex1b/hex1b/src/Hex1b/Automation/Hex1bTerminalInputSequence.cs:line 41
at Aspire.Cli.EndToEnd.Tests.MultipleAppHostTests.DetachFormatJsonProducesValidJson() in /_/tests/Aspire.Cli.EndToEnd.Tests/MultipleAppHostTests.cs:line 128
--- End of stack trace from previous location ---
```

Terminal output from DetachFormatJsonProducesValidJson.cast

```text
[10 OK] $ aspire run --detach --format json > output.json
DOTNET_DbgEnableMiniDump is set and the createdump binary does not exist: createdump
🔍 Finding apphosts...

⠋ Searching...

⠙ Searching...

⠚ Searching...

⠞ Searching...

⠖ Searching...

⠦ Searching...

⠴ Searching...

⠲ Searching...

⠳ Searching...

⠓ Searching...

⠋ Searching...

⠙ Searching...

⠚ Searching...

⠞ Searching...

⠖ Searching...

⠦ Searching...

⠴ Searching...

⠲ Searching...

⠳ Searching...

⠓ Searching...

⠋ Searching...

⠙ Searching...

⠚ Searching...

⠞ Searching...

⠖ Searching...

❌ An unexpected error occurred: Expected depth to be zero at the end of the JSON payload. There is an open JSON object or array that should be closed.
LineNumber: 1 | BytePositionInLine: 0.
[11 ERR:1] $
```

### Known issue validation
**Build: :mag_right:**
**Result validation:** :warning: Validation could not be done without an Azure DevOps build URL on the issue. Please add it to the "**Build:** :mag_right:" line.
**Validation performed at:** 3/10/2026 10:20:29 PM UTC

📊 **[View CI Failure Report](https://github.com/microsoft/aspire/issues/15113#issuecomment-4174836594)**