[SergeyMenshykh]

Motivation

Simplify A2A agent creation by using one options-based API and remove null-forgiving operators from response handling.

Description

• Remove the individual identity-parameter overloads from A2AAgent and IA2AClient.AsAIAgent. Callers configuring identity must now use A2AAgentOptions.
• Make options nullable and optional, clone supplied options, and avoid allocating default options when none are supplied.
• Use payload case checks with non-null patterns for responses and when guards for streaming updates.
• AI assistance was used for implementation, tests, documentation, and this PR description.

Related Issue

No linked issue.

[Copilot]

🟢 Approval recommended

No active review issues remain for the options-based API consolidation and null-safe response handling.

No open issues 🎉

What changed in this PR

Simplifies .NET A2A agent creation around a single options-based API and makes response payload handling explicitly null-safe. Removing the identity-parameter overloads is a breaking change for callers configuring agent identity.

Changes:

• Make A2AAgentOptions optional and nullable, preserving cloning when supplied and avoiding default-options allocation.
• Replace null-forgiving payload access with non-null patterns in regular and streaming responses.
• Migrate agent-card creation, sample documentation, and tests to the options-based API.

File	Description
dotnet/​tests/​Microsoft.Agents.AI.A2A.UnitTests/​Extensions/​A2AClientExtensionsTests.cs	Migrate identity tests and cover omitted options, null options, and null clients.
dotnet/​tests/​Microsoft.Agents.AI.A2A.UnitTests/​A2AAgentTests.cs	Update constructor tests for options-based identity and default behavior.
dotnet/​src/​Microsoft.Agents.AI.A2A/​Extensions/​A2AClientExtensions.cs	Consolidate client conversion into one optional-options overload.
dotnet/​src/​Microsoft.Agents.AI.A2A/​Extensions/​A2AAgentCardExtensions.cs	Pass card identity through A2AAgentOptions.
dotnet/​src/​Microsoft.Agents.AI.A2A/​A2AAgentOptions.cs	Remove documentation referring to individual constructor parameters.
dotnet/​src/​Microsoft.Agents.AI.A2A/​A2AAgent.cs	Consolidate construction, handle absent options, and guard response payloads.
dotnet/​samples/​02-agents/​A2A/​A2AAgent_ProtocolSelection/​README.md	Update the direct-client example to use options.

_{Review effort: Balanced}

[github-actions]

MAF Automated Review — Iteration 1

Result: No findings
Scope: full PR (2 commit(s)): 9ddf897ada77, 3d887614129e
Model: gpt-5.6-sol

Overview

This PR intentionally consolidates public A2A creation APIs around nullable optional options, clones supplied identity data, and replaces null-forgiving payload access with guarded patterns that fail closed on malformed unions. Constructor and extension tests cover omitted, null, and empty options, stable fallback identity, null-client guards, and mutation isolation; existing agent-card paths preserve card metadata. The sole compatibility concern is the deliberately declared breaking overload removal, which follows the repository's breaking-change policy for this preview package and is not a defect against the stated contract.

Reviewed the supplied pull-request change set across correctness, security/reliability, architecture, and failure behavior.
No publishable findings remained after source verification for this scope.