[bot] Add instrumentation for Azure.AI.Agents.Persistent (Azure AI Foundry Agents Service)

[braintrust-bot]

Summary

The Azure.AI.Agents.Persistent NuGet package (v1.1.0 stable, v1.2.0-beta.10 prerelease, ~2.2M total downloads) is Microsoft's official .NET client library for the Azure AI Foundry Agents Service — the production-ready stateful agent execution service built into Azure AI Foundry. It provides execution-oriented surfaces for running AI agents on conversation threads, streaming agent responses, and handling tool calls — none of which are instrumented in this SDK.

This package is distinct from every already-instrumented or already-filed package:

• Azure.AI.OpenAI (already instrumented) — direct model calls
• Azure.AI.Inference (issue [bot] Add instrumentation for Azure.AI.Inference (Azure AI Foundry model inference) #66) — Azure AI Foundry model inference API
• Azure.AI.Projects — project-level resource management

Azure.AI.Agents.Persistent is the package used in the official C# quickstart for executing agents: it owns the full run lifecycle (create thread → create run → poll status → retrieve messages).

Execution surfaces missing instrumentation

• Run creation: RunsClient.CreateRun(threadId, agentId, ...) — submits a thread for execution against a configured agent, invoking the underlying LLM
• Streaming runs: RunsClient.CreateRunStreamingAsync(threadId, agentId, ...) — streams StreamingUpdate events including ThreadRun, RunStep, and MessageDelta as the agent generates a response
• Tool output submission: RunsClient.SubmitToolOutputsToRunAsync(threadId, runId, toolOutputs) — resumes a paused run after function/tool calls complete; the agent then continues generation
• Streaming tool output: RunsClient.SubmitToolOutputsToStreamAsync(...) — streaming variant of tool output submission
• Agent administration: AdministrationClient.CreateAgent(model, name, instructions, tools) — creates the agent configuration that drives model selection and system prompt

Braintrust docs status

not_found — The Braintrust Azure integration page documents only chat completion instrumentation via Braintrust.Sdk.AzureOpenAI and does not mention the Azure AI Foundry Agents Service or Azure.AI.Agents.Persistent. No C#-specific agent-run instrumentation is referenced anywhere in Braintrust docs.

Upstream sources

• NuGet: https://www.nuget.org/packages/Azure.AI.Agents.Persistent (v1.1.0 stable, July 25, 2025; v1.2.0-beta.10 prerelease, March 21, 2026)
• Official C# quickstart: https://learn.microsoft.com/en-us/azure/ai-services/agents/quickstart?tabs=dotnet — demonstrates RunsClient.CreateRun, polling, and message retrieval
• API reference: https://learn.microsoft.com/en-us/dotnet/api/overview/azure/ai.agents.persistent-readme
• GitHub source: https://github.com/Azure/azure-sdk-for-net/tree/main/sdk/ai/Azure.AI.Agents.Persistent
• Azure AI Foundry Agents overview: https://learn.microsoft.com/en-us/azure/ai-services/agents/overview

Local repo files inspected

• src/Braintrust.Sdk.OpenAI/ — instruments OpenAI chat client only
• src/Braintrust.Sdk.AzureOpenAI/ — instruments Azure.AI.OpenAI chat client only
• src/Braintrust.Sdk.Anthropic/ — instruments Anthropic messages only
• src/Braintrust.Sdk.AgentFramework/ — instruments Microsoft.Extensions.AI.IChatClient middleware only
• Grep for Azure.AI.Agents, PersistentAgentsClient, RunsClient, CreateRun, and AgentsClient across the entire src/ tree returned zero results