[dotnet-port] Add BuildSequential and BuildConcurrent agent workflow builder helpers

[qmuntal]

Port .NET's AgentWorkflowBuilder.BuildSequential and AgentWorkflowBuilder.BuildConcurrent convenience functions to Go, including the concurrent aggregation path.

BuildSequential chains agents in order using the default Config (message forwarding and role reassignment enabled), matching .NET's pipeline behavior. It now terminates with an OutputMessages-style executor so the workflow output contains the full turn transcript.

BuildConcurrent fans the input to all agents simultaneously using a lightweight forwarding executor at the start, per-agent turn-message batchers, and a fan-in end executor. BuildConcurrentWithAggregator supports custom, context-aware aggregation and defaults to returning the last message from each non-empty agent batch.

Tests cover single-agent and multi-agent cases for both builders, invalid inputs, custom aggregation, multi-turn concurrent aggregation reset behavior, and the message forwarding executor spec helper.

The agent workflow patterns StartHere sample is synced with the .NET sample's sequential/concurrent builder usage while keeping Azure OpenAI agent construction in the translation agent factory.

Closes the "sequential/concurrent can be composed manually" gap in the feature comparison doc.

[github-actions]

Generated by Go API Consistency Review Agent for issue #196 · ● 3.2M

[github-actions]

Generated by Go API Consistency Review Agent for issue #196 · ● 5.1M

[Copilot]

Pull request overview

This PR ports .NET’s AgentWorkflowBuilder.BuildSequential / BuildConcurrent conveniences into Go by adding workflowhosting builder helpers, plus a small message-forwarding executor spec helper used by the concurrent fan-out path. It also adjusts workflow context handling for observability/tracing and syncs a workflow patterns example + feature comparison docs.

Changes:

• Add workflowhosting.BuildSequential, BuildConcurrent, and BuildConcurrentWithAggregator helpers (with transcript-style output for sequential and fan-out/fan-in aggregation for concurrent).
• Introduce messageworkflow.ConfigureForwarding and accompanying tests to forward chat messages / turn tokens (and optionally strings).
• Update workflow context/telemetry plumbing, refresh tests accordingly, and sync example + feature-comparison documentation.

Show a summary per file

File	Description
workflow/workflow.go	Removes GetContext() and changes telemetry lookup to use the workflow context directly.
workflow/executor.go	Passes *workflow.Context into telemetry span creation (instead of GetContext()).
workflow/executor_test.go	Updates tests to populate workflow.Context.Context so executor execution has a real context.
message/messageworkflow/messageworkflow_test.go	Sets workflow.Context.Context in tests to avoid nil embedded contexts.
message/messageworkflow/messageforwarding.go	Adds ConfigureForwarding helper for forwarding messages/turn tokens (optional string support).
message/messageworkflow/messageforwarding_test.go	Adds coverage for forwarding behavior and protocol description.
agent/hosting/workflowhosting/builders.go	Adds sequential/concurrent workflow builder helpers + internal executors (start forwarder, per-agent batchers, end aggregator, transcript sink).
agent/hosting/workflowhosting/builders_test.go	Adds comprehensive tests for sequential/concurrent builders, custom aggregation, and multi-turn reset behavior.
examples/03-workflows/_start-here/03_agent_workflow_patterns/main.go	Updates sample to use new builders and newer OpenAI agent provider package.
docs/dotnet-go-sdk-feature-comparison.md	Updates feature comparison to reflect new sequential/concurrent builders.

Copilot's findings

Tip

Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

Comments suppressed due to low confidence (1)

workflow/executor.go:285

• telemetry.StartExecutorProcess is now invoked with ctx (a *workflow.Context) as the context.Context argument. This will panic if ctx.Context (the embedded context) is nil because ctx.Value will dispatch to a nil embedded interface. Either ensure *workflow.Context safely implements context.Context with a non-nil fallback (e.g., background) or pass a guaranteed-non-nil context here.

	telemetry := ctx.telemetry()
	messageType := NewTypeID(reflect.TypeOf(message))
	spanCtx, span := telemetry.StartExecutorProcess(
		ctx,
		e.ID,
		observability.TypeName(e.ExecutorType),
		messageType.TypeName,
		message,
		ctx.traceContextStrings(),
	)

• Files reviewed: 10/10 changed files
• Comments generated: 5

[github-actions]

Cross-repo parity review ✅

This PR is a faithful port of .NET's AgentWorkflowBuilder.BuildSequential and BuildConcurrent to Go.

Verified alignment with .NET upstream:

• BuildSequential: chains agents with ForwardIncomingMessages = true and ReassignOtherAgentsAsUsers = true (matching AIAgentHostOptions defaults), terminates with an OutputMessagesExecutor — identical semantics to .NET.
• BuildConcurrent: fan-out via a forwarding executor, per-agent AggregateTurnMessages batchers, fan-in barrier, then a ConcurrentEndExecutor — identical graph topology to .NET.
• Default aggregator (last message per non-empty batch) matches the .NET fallback.
• The split into BuildConcurrentWithAggregator is an idiomatic Go adaptation of .NET's optional aggregator parameter (Go has no default args).
• The context.Context added to MessageAggregator is an idiomatic Go enhancement with no semantic regression.

Python: No equivalent build_sequential/build_concurrent helpers exist in the Python package yet; this is an explicit .NET → Go port, so no Python parity gap is introduced by this PR.

No cross-repo consistency issues found.

Generated by Go API Consistency Review Agent for issue #196 · ● 12.9M · ◷