agents

• Add live shell output reporting: ShellExecutor.outputEvents broadcasts typed ShellOutputChunk values while commands run, local and Docker options accept an onOutput callback, and persistent shell sessions now capture stderr instead of discarding it.

• Add AnthropicChatClient under anthropic/: a ChatClient backed by Anthropic's Messages API, with client builder extensions and shared defaults.
• Add GeminiChatClient and GeminiClient under gemini/: a ChatClient backed by the Gemini API, with builder extensions and defaults. Handles thoughtSignature round-tripping on function calls (including the documented skip-validation placeholder for replayed calls), strips unsupported additionalProperties from tool and response schemas, and enables server-side tool invocations when mixing Gemini built-in tools with function tools.
• Add MCP integration under mcp/: AgentMcpSkillsSource discovers Agent Skills exposed over MCP (AgentMcpSkill, McpSkillIndex, AgentMcpSkillResource, plus options), McpClientTaskExtensions exposes MCP tools as AI functions (McpClientAIFunction, TaskAwareMcpClientAIFunction, McpTaskOptions), and the skills provider builder gains MCP registration extensions.
• Add sequential and concurrent orchestrations to the workflows engine: SequentialWorkflowBuilder and ConcurrentWorkflowBuilder on the shared OrchestrationBuilderBase, with OutputTag (+ JSON converter), WorkflowOutputEvent extensions, and checkpoint support for output executors in WorkflowInfo.
• Add session-store composition under hosting/: DelegatingAgentSessionStore, IsolationKeyScopedAgentSessionStore (+ options), and SessionIsolationKeyProvider for partitioning stored sessions by user, tenant, or composite keys.
• Expand OpenAI hosting: HostedAgentResponseExecutor routes Responses API requests to hosted agents by agent.name or metadata["entity_id"], with OpenAIResponseRequestInfo / OpenAIChatCompletionRequestInfo request descriptors, per-API map options, AgentReference, and standardized response error codes.
• Add OpenAI conversion helpers under ai/open_ai/: extensions mapping AgentResponse and ChatClientAgent results onto OpenAI wire formats.
• Add auto-approval rules to the tool-approval middleware: ToolApprovalAgentOptions with ordered autoApprovalRules (evaluated after standing rules, before prompting the user) and an approve-all rule.
• Expand the file access and file memory providers: new replace and replace_lines editing tools backed by the shared FileEditor / FileLineEdit helpers, FileStoreEntry metadata, configurable tool names, and read-only / full auto-approval rule presets.
• Add chat-client decorators: MessageInjectingChatClient lets external code (such as tool delegates) enqueue messages into the function invocation loop, and NonApprovalRequiredFunctionBypassingChatClient strips approval requests for tools that do not require approval, re-injecting them pre-approved on the next request.
• Add BackgroundTaskCompletionLoopEvaluator (+ options): keeps a LoopAgent iterating until tracked background tasks complete, with a templated feedback message listing the still-running tasks.
• Add skills improvements: a CachingAgentSkillsSource decorator (+ options), AgentSkillsSourceContext, and AgentFileSkillFilterContext for filtering file-based skills.
• Add evaluation types: GeneratedEvaluatorRef (versioned references to generated evaluators) and RubricScore (typed per-dimension score breakdown for rubric evaluators).
• Export InvokedContext and InvokingContext as standalone libraries (previously hidden from the public API) and publicly export ChatMessageJsonConverter.
• Fix AIContextProvider.getService to resolve requests for concrete provider types (matching the runtimeType idiom used by AgentSession and DelegatingAIAgent); concrete-type lookups previously returned null, breaking provider resolution in BackgroundTaskCompletionLoopEvaluator and TodoCompletionLoopEvaluator.
• Add anthropic_sdk_dart: ^5.0.0, archive: ^4.0.9, http: ^1.6.0, and mcp_dart: ^2.2.1 dependencies; bump extensions to ^0.5.0.

• Add loop agents under harness/loop/: LoopAgent and LoopAgentOptions run an inner agent repeatedly until an evaluator signals completion, with pluggable LoopEvaluator strategies — AIJudgeLoopEvaluator, CompletionMarkerLoopEvaluator, TodoCompletionLoopEvaluator, and DelegateLoopEvaluator — plus LoopContext, LoopEvaluation, and JudgeVerdict support types.
• Add Magentic multi-agent orchestration to the workflows engine: MagenticWorkflowBuilder, MagenticOrchestrator, the plan-review request/response messages, and the progress ledger (ports the upstream Magentic manager/orchestrator pattern).
• Add OpenAI-compatible hosting under hosting/open_ai/: shelf-based routers and handlers for the Chat Completions, Conversations, and Responses APIs, backed by in-memory storage, exposed through open_ai_hosting_service_collection_extensions.
• Add shelf: ^1.4.0 and shelf_router: ^1.1.0 dependencies for the OpenAI hosting routers.
• Fix fan-in edges losing buffered messages across checkpoint/resume: pending fan-in contributions are now captured in Checkpoint.fanInState and restored on resume (both the in-proc and legacy execution engines). Old checkpoint JSON without the field remains loadable.
• Fix fan-in edges dropping all but the last message from a source that sent more than once before the edge released; all buffered messages are now delivered, ordered by source then arrival (matches upstream FanInEdgeState semantics).
• Fix streamed responses losing responseId, messageId, createdAt, usage, modelId, rawRepresentation, and additionalProperties when coalesced by ChatClientAgent and PerServiceCallChatHistoryPersistingChatClient; all call sites now share one toChatResponse() extension (ports C# ToChatResponse).
• Fix A2AAgentSession.serialize() dropping the session stateBag; it now round-trips, and legacy payloads without it remain loadable.
• Remove the unused StatefulEdgeRunner interface (breaking; it had no implementors — fan-in state is checkpointed via Checkpoint.fanInState).
• Rename agent_response_t_.dart → agent_response_of.dart and provider_session_state_t_state_.dart → provider_session_state.dart (library paths only; type names unchanged).
• Simplify shell executor timeout handling with a shared waitForProcessExit helper; removes an unmanaged kill timer and ensures the force-kill is awaited before draining output.

• Add A2A (Agent-to-Agent) protocol support:
  • Client-side A2AAgent, A2AAgentOptions, A2AAgentSession, and A2AContinuationToken for consuming remote agents over the A2A protocol.
  • a2a_client_extensions and a2a_agent_card_extensions helpers.
  • Server-side hosting bridge: A2AAgentHandler, A2ARunDecisionContext, A2AServerRegistrationOptions, agentRunMode, the a2a_server_service_collection_extensions registration helpers, and a MessageConverter.
• Add a2a: ^4.2.0 dependency.

New

• AIContentExtensions — adds concatText() on List<ChatMessage>, concatenating each message's text with newline separators (skipping empty values). Ports AIContentExtensions.ConcatText(IList<ChatMessage>) from Microsoft.Agents.AI.Abstractions. The companion overload on Iterable<AIContent> is already provided by the extensions package.

Breaking

• Renamed five workflow execution interfaces to conform to the Dart convention that every class is an implicit interface (no IFoo prefixes):
  • IStepTracer → StepTracer
  • IEventSink → EventSink
  • IStatefulEdgeRunner → StatefulEdgeRunner
  • IDelayedDeserialization → DelayedDeserialization
  • ISuperStepRunner → SuperStepRunnable (renamed to avoid collision with the concrete SuperStepRunner class)

Fixed

• Harness files (HarnessAgent, HarnessAgentOptions, ChatClientHarnessExtensions) were placed at lib/src/harness/ but their relative imports and the barrel export in agents.dart expected lib/src/hosting/harness/. Files moved to the correct location, resolving 73 analyzer errors.

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Initial release — Dart port of four C# namespaces from the Microsoft Agents AI framework.

Abstractions (Microsoft.Agents.AI.Abstractions)

• AIAgent — base class for all agents; defines run, runStreaming, createSession, serializeSession, and deserializeSession
• AgentSession / AgentSessionStateBag — stateful conversation context serializable to/from JSON
• AgentResponse / AgentResponseUpdate — typed wrappers around ChatResponse / ChatResponseUpdate
• AgentRunOptions / AgentRunContext — per-call options and ambient context
• DelegatingAIAgent — base for decorator agents that forward to an inner agent
• ChatHistoryProvider / InMemoryChatHistoryProvider — pluggable chat history persistence
• AIContextProvider / MessageAIContextProvider — context enrichment hooks that inject instructions, messages, and tools before each run

AI (Microsoft.Agents.AI)

• ChatClientAgent — production AIAgent backed by any ChatClient (automatic function-invocation middleware, conversation-id tracking, per-service-call history persistence)
• ChatClientAgentOptions — fluent configuration for instructions, tools, chat options, and history providers
• AIAgentBuilder — composable decorator pipeline builder
• LoggingAgent — decorator that emits structured Logger output at debug/trace granularity
• FunctionInvocationDelegatingAgent — injects custom middleware around every tool call
• AnonymousDelegatingAIAgent — lightweight decorator from a lambda
• Extension methods: ChatClient.asAIAgent, ChatClientBuilder.buildAIAgent, ChatClientBuilder.usePerServiceCallChatHistoryPersistence
• Compaction — CompactionChatClient, CompactionTelemetry, CompactionGroupKind, CompactionTrigger
• Evaluation — AgentEvaluator, EvalCheck, CheckResult, AgentEvaluationExtensions
• Skills — AgentSkillsProvider, AgentSkillsSource, AgentInMemorySkillsSource, AgentFileSkillsSource, DeduplicatingAgentSkillsSource, AgentSkillFrontmatter, AgentSkillResource, AgentSkillScript
• Harness — file store, file access, file memory, todo, sub-agents, agent mode, and tool-approval providers for local agent runtimes

Hosting (Microsoft.Agents.AI.Hosting)

• HostApplicationBuilderAgentExtensions — DI registration helpers
• AgentHostingServiceCollectionExtensions — service-collection extensions
• HostedAgentBuilder / HostedWorkflowBuilder — lifecycle-managed agent and workflow wiring
• WorkflowCatalog — registry for named workflow definitions

Workflows (Microsoft.Agents.AI.Workflows)

• Executor / Workflow / WorkflowContext — multi-agent orchestration engine
• MessageRouter / ProtocolBuilder / ProtocolDescriptor — message routing and protocol description
• Checkpointing, observability, in-process execution, and specialised workflow sub-areas