v1.6 SDK Release

What's Changed

New Features

Slack Extension (Microsoft.Agents.Extensions.Slack)

New first-class Slack channel extension, enabling agents to communicate directly with Slack without requiring Azure Bot Service as an intermediary:

• SlackAgentExtension: Extension class with routing helpers (OnSlackMessage, OnSlackEvent*) for handling Slack-specific events and messages.
• SlackStream: Streaming support for Slack, allowing agents to stream responses back to Slack channels.
• SlackApi: Low-level Slack API client for direct Slack Web API calls.
• SlackChannelData: Strongly-typed channel data model with Payload support for action events.
• MapSlackEndpoints: ASP.NET Core endpoint routing for Slack event subscriptions and interactions.
• SlackExtensionAttribute: Source-generated attribute for declarative Slack event routing.
• Includes a full SlackAgent sample demonstrating streaming, event handling, and action payloads.

Named Pipe Transport (Microsoft.Agents.Hosting.DirectLine.NamedPipes)

New Named Pipe transport layer for high-performance local inter-process agent communication:

• NamedPipeProtocol: Binary protocol with chunked transfer, payload size limits, and content-type negotiation.
• NamedPipeTransport: Reliable duplex transport with disconnect handling and error recovery.
• NamedPipeMessageHandler: Activity message handler with streaming attachment support.
• NamedPipeHostedService: IHostedService implementation for ASP.NET Core integration.
• Enforces payload size limits and handles large object heap (LOH) pressure via 64 KB chunked trailing-byte drain.
• Idempotent DisposeAsync to prevent ObjectDisposedException on double-dispose.
• Comprehensive test coverage for chunking, content type handling, end flag semantics, boundary conditions, and streaming behavior.

Declarative Route Attributes (AgentApplicationAttributes)

New attribute-based routing model for agent handlers, complementing the existing fluent API:

• AgentExtensionAttribute: Base attribute for agent extension registration with source-generated routing via AgentExtensionSourceGenerator.
• Route builder base classes: ConversationUpdateRouteBuilderBase, EventRouteBuilderBase, FeedbackRouteBuilderBase, HandoffRouteBuilderBase, MessageRouteBuilderBase, TypeRouteBuilderBase — enabling extensible, attribute-driven route registration.
• IRouteAttribute: Public interface for custom route attributes.
• Full test coverage for attribute-based routing.

Agentic Header Propagation

• AgenticHeaderProvider / IHeaderValueProvider: New infrastructure for propagating agentic context headers across agent-to-agent calls.
• Enables forwarding of correlation and orchestration headers through the call chain.
• Integrated in the AgentAI sample.

OAuth Sign-In Cancellation

• TeamsSignInInProgressMessage: New message shown to Teams users when a sign-in flow is already in progress.
• Added cancel options allowing users to abort an in-progress OAuth flow.

Authentication: IdentityProxyManager Auth Type

• New AuthTypes.IdentityProxyManager replaces the UserManagedIdentity + EnableContainerIMDS combination with a single, clearer auth type for container identity proxy scenarios.

Authentication: Azure Region Support

• AzureRegion handling added to MsalAuth, enabling region-aware token acquisition for improved latency and resilience.

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Improvements

ServiceUrl Validation

• Added optional Activity.ServiceUrl check against the serviceurl claim in authentication for defense-in-depth validation.
• Graceful handling of invalid ServiceUrl format instead of throwing unhandled exceptions.
• Removed unnecessary DeliveryMode guard in ValidateServiceUrl.

AgentState Thread Safety

• Switched AgentState to lock-based concurrency to preserve serialization order and prevent crashes under streaming workloads.
• Added argument validation and comprehensive locking across AgentState operations.
• New AgentStateThreadSafetyTests and AgentStateValidationTests test suites.

Serialization / JSON

• DictionaryOfObjectConverter: Fixed round-trip for primitive arrays in IDictionary<string, object> — complex types are excluded from primitive array promotion to preserve existing shape for callers expecting IList.
• DictionaryOfObjectConverter: Fixed crash on 2D arrays in IDictionary<string, object>.
• Added comprehensive DictionaryOfObjectConverter unit tests.

Proactive Messaging Instrumentation

• New OpenTelemetry scopes for proactive operations: ContinueConversation, CreateConversation, DeleteConversation, GetConversation, SendActivity, StoreConversation.
• Proactive services are now registered on the TurnContext in Proactive.OnTurnAsync.

Route Builders

• Refactored core route builders (ConversationUpdateRouteBuilder, EventRouteBuilder) to use base classes, enabling future extensibility.
• Added protected constructors to route builder base classes for subclassing.
• Fixed ChannelId wildcard to include subchannel matching.

Logging

• CloudAdapterLog: New structured log class for CloudAdapter operations.
• Changed LogNoRouteMatched from Information to Debug level to reduce log noise.
• Surface OAuthHandlers delegate errors in route JSON output for easier diagnostics.
• Added BeginScope to CloudAdapter and HostedActivityService for structured log correlation.

Connector

• ConversationsRestClient: Sanitize truncated agents-channel conversation IDs (#840).
• GetConversationReference: Added parameterless overload.
• Wrapping the returned task for DeleteConversation.
• Null or whitespace check for audience when creating ConnectorClient.

Startup

• AgentApplication now defaults to MemoryStorage if no IStorage is registered, eliminating the most common startup misconfiguration.
• HttpClientFactory added to AgentApplicationOptions.

OAuth Flow

• Changed OAuth flow to not rely on exceptions for control flow, improving performance and debuggability.
• Added OAuthFlowResult type for structured flow outcomes.

TypingWorker

• Fixed race condition in TypingWorker under concurrent turns.

ObjectPath

• Fixed ObjectPath issues and added comprehensive unit tests.

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Bug Fixes

• AgentState thread-safety crash under streaming (#841): Concurrent streaming operations could corrupt AgentState due to ConcurrentDictionary not preserving serialization order for DictionaryOfObjectConverter. Switched to lock-based concurrency to fix.
• DictionaryOfObjectConverter crash on primitive arrays: Primitive arrays in IDictionary<string, object> were not round-tripping correctly, causing data loss or runtime exceptions. Fixed array promotion logic.
• DictionaryOfObjectConverter crash on 2D arrays: Multi-dimensional arrays in IDictionary<string, object> would throw during deserialization. Added proper nested array handling.
• Truncated conversation IDs (#840): Agents-channel conversation IDs could be truncated in ConversationsRestClient, causing 404s or misrouted messages. IDs are now sanitized before use.
• Citation icon names (#823): Added Microsoft OneNote and SharePoint to AI Citation icon names, fixing deserialization failures for activities from Copilot Studio.
• Fix for #827.
• StreamingResponse final message regression: Fixed regression in StreamingResponse final message handling introduced during v1.5.x.
• CultureNotFoundException in TypeExtensions: Fixed crash during BotState serialization when running under certain culture settings.
• SerializationInit race conditions: Fixed races in SerializationInit paths, including improper initialization in the SharePoint extension.
• TypingWorker race condition: Fixed race in TypingWorker that could cause missed or duplicate typing indicators under concurrent turns.

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Infrastructure & Tooling

• Bumped .NET SDK from 8.0.420 to 8.0.422.
• Updated pull request workflows to include rel/** branches (#804).
• Added AnalyzerReleases shipped/unshipped tracking files to Core.Analyzers.
• Added extensive test coverage across Authentication, Slack, AgentState, NamedPipe, Route, and DictionaryOfObjectConverter.
• Using launchSettings consistently for sample projects.
• Added architecture diagrams, copilot instructions, and developer documentation.

Full Changelog: v1.5.184...v1.6.150