Python: .NET: Show Aspire traces in DevUI

[Saibernard]

Summary

Fixes #5806.

This makes Aspire traces available in the existing DevUI Traces tab. The aggregator now:

• propagates a unique trace context to the selected agent service
• captures the OpenAI response ID without changing the proxied response
• retrieves the matching spans from the local Aspire Dashboard telemetry API
• exposes those spans to the shared DevUI frontend
• handles delayed span export, cancellation, dashboard failures, and concurrent responses

I also fixed three issues in the Aspire sample that prevented the current sample from starting cleanly: conflicting dashboard ports, AppHost target-framework discovery, and an Aspire Azure package-version mismatch.

Testing

• 100/100 unit tests passed
• Release package build passed with 0 warnings and 0 errors
• Release AppHost sample build passed with 0 warnings and 0 errors
• Frontend production build passed
• Frontend lint completed with 0 errors
• git diff --check passed

I tested streaming and non-streaming responses against a real Azure GPT-4.1 deployment. Both responses mapped to the correct four-span Aspire trace. I also verified that cancelling a response does not leave a stale trace mapping.

The live Azure deployment had capacity for one request, so the two-request live concurrency check was rate-limited. The regression suite covers 12 simultaneous responses and trace lookups, plus 100 parallel SSE response-ID captures.

[Saibernard]

Here are the screenshots from the live validation run.

The first one shows the successful streaming response and the four Aspire spans that DevUI retrieved for it.

The second one shows the matching trace ID, successful status, and the redacted Azure HTTP span.

I replayed the captured live response and trace payload through the built DevUI so the screenshots are reproducible.

Full validation log | Sanitized trace payload

[Copilot]

Pull request overview

Adds Aspire Dashboard trace retrieval to the shared DevUI frontend for .NET agent services.

Changes:

• Correlates responses with Aspire OpenTelemetry traces.
• Adds cancellable frontend trace polling and runtime-specific guidance.
• Fixes Aspire sample configuration and package mismatches.

Reviewed changes

Copilot reviewed 15 out of 17 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
python/packages/devui/frontend/src/types/index.ts	Adds tracing capabilities.
python/packages/devui/frontend/src/services/api.ts	Polls trace endpoints.
python/packages/devui/frontend/src/components/layout/debug-panel.tsx	Updates .NET trace guidance.
python/packages/devui/frontend/src/components/features/agent/context-inspector.tsx	Updates context guidance.
python/packages/devui/frontend/src/components/features/agent/agent-view.tsx	Starts and cancels trace polling.
python/packages/devui/frontend/src/App.tsx	Configures tracing from metadata.
python/packages/devui/agent_framework_devui/ui/assets/index.css	Regenerates frontend CSS.
dotnet/tests/Aspire.Hosting.AgentFramework.DevUI.UnitTests/AspireDashboardTracingTests.cs	Tests trace correlation and failures.
dotnet/src/Aspire.Hosting.AgentFramework.DevUI/SseResponseIdCapture.cs	Extracts response IDs from SSE.
dotnet/src/Aspire.Hosting.AgentFramework.DevUI/README.md	Documents Aspire tracing.
dotnet/src/Aspire.Hosting.AgentFramework.DevUI/DevUIAggregatorHostedService.cs	Implements trace propagation and retrieval.
dotnet/src/Aspire.Hosting.AgentFramework.DevUI/AspireDashboardTraceClient.cs	Converts Dashboard spans for DevUI.
dotnet/src/Aspire.Hosting.AgentFramework.DevUI/AgentFrameworkBuilderExtensions.cs	Supplies AppHost configuration.
dotnet/samples/05-end-to-end/DevUIAspireIntegration/DevUIIntegration.AppHost/Properties/launchSettings.json	Resolves dashboard port conflicts.
dotnet/samples/05-end-to-end/DevUIAspireIntegration/DevUIIntegration.AppHost/DevUIIntegration.AppHost.csproj	Fixes framework and Azure references.
dotnet/Directory.Packages.props	Pins the Aspire Azure package.

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[Saibernard]

@microsoft-github-policy-service agree

[Saibernard]

Addressed all three review findings in b74e546d.

What changed:

• Unset OTLP statuses now match the frontend contract.
• Trace retrieval now uses Aspire’s trace-by-ID endpoint and rejects count mismatches.
• The frontend merges snapshots by span ID and waits for three identical merged snapshots before publishing.

Validation:

• Aspire DevUI tests: 102 passed, 0 failed
• Frontend lint: 0 errors, 13 existing warnings in unrelated files
• Frontend production build: passed
• Aspire package Release build for net10.0: 0 warnings, 0 errors
• DevUI Aspire integration sample Release build for net10.0: 0 warnings, 0 errors
• dotnet format: 0 files changed
• git diff --check: passed

The existing screenshots are still representative because these changes affect trace completeness and status handling, not the layout.

[Copilot]

Pull request overview

Copilot reviewed 15 out of 17 changed files in this pull request and generated 3 comments.

[Saibernard]

@microsoft-github-policy-service agree

[Saibernard]

Addressed the latest review feedback in 269d2cbc and revalidated the change locally.

• Aspire tracing tests: 103 passed, 0 failed
• Cancellation regression: passed 5 consecutive runs
• Frontend lint: 0 errors, with the same 13 existing warnings
• Frontend production build: passed
• Aspire package Release build: 0 warnings, 0 errors
• Aspire integration sample Release build: 0 warnings, 0 errors
• dotnet format: 0 files changed
• git diff --check: passed

The existing Aspire screenshots are still representative. This revision changes the empty-state guidance for non-Aspire .NET servers and adds cancellation coverage. It does not change the Aspire trace layout or the successful trace display.

[Copilot]

Pull request overview

Copilot reviewed 16 out of 18 changed files in this pull request and generated no new comments.

[Copilot]

Pull request overview

Copilot reviewed 16 out of 18 changed files in this pull request and generated 1 comment.

[Copilot]

Pull request overview

Copilot reviewed 16 out of 18 changed files in this pull request and generated no new comments.

Suppressed comments (1)

Previously missed (1) — in code that hasn't changed since the last review.

dotnet/src/Aspire.Hosting.AgentFramework.DevUI/SseResponseIdCapture.cs:63

• The 64 KiB cap can discard valid response IDs. This repository's StreamingResponseCreated serializes a full Response, including request instructions and tool definitions (Microsoft.Agents.AI.Hosting.OpenAI/Responses/AgentResponseUpdateExtensions.cs:242-272), so a valid data: line can exceed this limit. Once that happens, this parser drops the entire line; the later lifecycle response events can carry the same large response payload, leaving ResponseId null and preventing any trace mapping. Keep memory bounded while extracting response.id without requiring the complete line to fit in 64 KiB, and add coverage with an oversized response.created event.

            if (this._lineBuffer.WrittenCount >= MaxLineLength)
            {
                this._lineBuffer.Clear();
                this._discardingOversizedLine = true;
                continue;

[Saibernard]

Fixed the oversized SSE case in 3a97a67d and preserved the existing response ID precedence in df8a439d. Response ID capture now parses the entire bounded JSON prefix, so large valid response.created payloads still map to traces without removing the 64 KiB memory limit, while malformed prefixes are rejected. Added fragmented coverage with an event over 80 KiB, plus malformed JSON and precedence coverage. All 110 tracing tests pass, including five repeated full-suite runs.

[Copilot]

Pull request overview

Copilot reviewed 16 out of 18 changed files in this pull request and generated no new comments.