[SergeyMenshykh]

Motivation & Context

A streamed A2A response could be yielded before its context ID was checked against the context already associated with the provided session. This could allow callers to observe an update from a different context before the mismatch was reported.

Description & Review Guide

• What are the major changes? Validate the context ID of message, task, status-update, and artifact-update payloads before yielding their corresponding updates. Apply the same behavior to the .NET and Python A2A implementations and add regression coverage for all four payload types.
• What is the impact of these changes? When both the session and response contain context IDs, a mismatch now fails before the response update is exposed to the caller. Responses without a context ID remain accepted. Continuation requirements, session-persistence timing, and public API signatures are unchanged.
• What do you want reviewers to focus on? The timing of context validation, parity between the .NET and Python implementations, and preservation of existing session and continuation behavior.

Related Issue

N/A.

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. If it is a breaking change, add the breaking change label (or add "[BREAKING]" to the title prefix, before or after any language prefix) — a workflow keeps the label and title prefix in sync automatically.

[Copilot]

Copilot review overview

🟡 Changes recommended

Whitespace-only context IDs can bypass the new unbound-session validation.

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Review effort: Balanced
Findings: 1

Open (1)

• Treat whitespace-only ContextId as unbound before continuation · New

What changed in this PR

Improves A2A continuation session validation and preserves streaming session state during interrupted enumeration.

Changes:

• Requires context-bound sessions for continuation tokens.
• Updates session state before yielding streaming responses.
• Adds regression tests for continuation and streaming behavior.

File	Description
dotnet/​src/​Microsoft.Agents.AI.A2A/​A2AAgent.cs	Implements continuation validation and incremental session updates.
dotnet/​tests/​Microsoft.Agents.AI.A2A.UnitTests/​A2AAgentTests.cs	Adds continuation and interrupted-stream coverage.

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[github-actions]

MAF Automated Review — Iteration 1

Result: Findings reported
Scope: full PR (2 commit(s)): cf4c6f6734fa, a0bea7bcae57
Model: gpt-5.6-sol-fast

Overview

The change consistently requires a context-bound session for continuation calls and moves streaming session updates ahead of each yielded update, with strong regression coverage for mismatched contexts and early abandonment. The shared continuation guard and pre-yield validation prevent several cross-context failure modes. Two residual gaps remain: context-less continuation responses bypass the new binding guarantee, and artifact-only updates can erase persisted task state during an interrupted reconnection.

Reviewed the supplied pull-request change set across correctness, security/reliability, architecture, and failure behavior.
2 verified findings remained after source verification (2 medium) across 1 file. Details are attached to the affected lines below.

Affected areas: dotnet/src/Microsoft.Agents.AI.A2A/A2AAgent.cs