.NET: Pass IServiceProvider to ChatClientAgent in AddAIAgent overloads

[westey (westey-m)]

Motivation & Context

All four AddAIAgent overloads in AgentHostingServiceCollectionExtensions created a ChatClientAgent without forwarding the IServiceProvider. As a result, the FunctionInvokingChatClient in the agent's pipeline received no service provider, so AIFunctionArguments.Services was null at invocation time and tools registered via DI could not resolve their dependencies.

This is a replication of #4483 by Max Montes Soza (@max-montes), with the unit tests reworked so they pass in CI (see below). Thanks Max Montes Soza (@max-montes) for the original fix!

Description & Review Guide

• What are the major changes?

  • AgentHostingServiceCollectionExtensions: pass services: sp to each of the four ChatClientAgent constructor calls.
  • AgentHostingServiceCollectionExtensionsTests: added an end-to-end regression test (a [Theory] covering all four overloads) that registers a marker service in DI, registers a tool on the agent, runs the agent against a stub chat client that requests the tool, and asserts the tool could resolve the marker service from AIFunctionArguments.Services.

• What is the impact of these changes?

  • Tools registered via WithAITool/DI on hosted agents can now resolve their dependencies when invoked. No public API change.

• Notes on the tests (differences from .NET: fix: pass IServiceProvider to ChatClientAgent in AddAIAgent overloads #4483):

  • The original tests used reflection against a FunctionInvokingChatClient._serviceProvider private field, which does not exist — the four tests failed in CI. FunctionInvokingChatClient.FunctionInvocationServices is protected, so it can't be read directly either.
  • Instead, the new test verifies the behaviour end-to-end through public APIs only, which is what the review feedback on .NET: fix: pass IServiceProvider to ChatClientAgent in AddAIAgent overloads #4483 asked for. It is a true regression test: it fails with 4 failures when the source fix is reverted, and passes with it.

Related Issue

Fixes#4453

Contribution Checklist

• The code builds clean without any errors or warnings
• All unit tests pass, and I have added new tests where possible
• The PR follows the Contribution Guidelines
• This PR is linked to an issue and there is no other open PR for this issue (see Related Issue above).
• This is not a breaking change.

[Copilot]

Pull request overview

Fixes DI service resolution during hosted-agent tool invocation by forwarding the active IServiceProvider to ChatClientAgent.

Changes:

• Passes the service provider through all four built-in AddAIAgent overloads.
• Adds end-to-end regression coverage for each overload.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
dotnet/src/Microsoft.Agents.AI.Hosting/AgentHostingServiceCollectionExtensions.cs	Forwards DI services when constructing agents.
dotnet/tests/Microsoft.Agents.AI.Hosting.UnitTests/AgentHostingServiceCollectionExtensionsTests.cs	Verifies tools can resolve DI services.

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[github-actions]

MAF Automated Review — Iteration 1

Result: Findings reported
Scope: full PR (1 commit(s)): 55da434c9d7f
Model:gpt-5.6-sol

Overview

The change consistently forwards the agent factory's provider through all four convenience overloads, and the regression theory verifies the intended function-invocation path end to end. Existing keyed-tool isolation and lifetime validation remain intact. However, the default singleton registration forwards the root provider, so tools that resolve scoped dependencies can retain request- or tenant-specific state across unrelated invocations.

Reviewed the supplied pull-request change set across correctness, security/reliability, architecture, and failure behavior.
1 verified finding remained after source verification (1 medium) across 1 file. Details are attached to the affected lines below.

Affected areas:dotnet/src/Microsoft.Agents.AI.Hosting/AgentHostingServiceCollectionExtensions.cs