[dotnet-port-api] Port .NET harness configurator

[github-actions]

Summary

Add a top-level agent/harness package that ports the narrow composed public API shape of .NET's HarnessAgent into Go without pulling in the broader .NET-only file access, file memory, or subagent features. The new harness.Configure helper applies default harness instructions, wires the existing todo and agent-mode context providers, and optionally adds loop and tool-approval middleware so provider-specific agent configs can opt into a batteries-included harness with one exported entry point.

This was selected from upstream microsoft/agent-framework commit c033adb1f4502d30b57149cb54f8683fab66297d because it adds a small, user-facing API surface that maps cleanly onto Go's existing harness packages and is reviewable as a standalone parity step. The feature comparison doc now lists the new top-level package, and focused tests plus an example cover the composed behavior.

Ported .NET PRs

• .NET: [BREAKING] Graduate HarnessAgent agent-framework#7119 - graduate HarnessAgent and expose a composed harness entry point for interactive agentic scenarios

Upstream commit: c033adb1f4502d30b57149cb54f8683fab66297d

Breaking Changes

No. This adds a new package and exported helper without changing existing public APIs.

Tests and Examples

• go test ./agent/harness/...
• Added agent/harness/harness_example_test.go
• Added focused coverage in agent/harness/harness_test.go for default composition, opt-out behavior, ordering, and loop wiring

Notes

This intentionally ports only the narrow composed harness configurator surface. The broader .NET harness features that still lack Go equivalents — file access, file memory, file store, subagent harness utilities, and the AI-judge loop evaluator — remain follow-up work. The Go helper composes the existing Go harness packages idiomatically instead of transliterating the full .NET HarnessAgent type and options tree.

Generated by .NET to Go API Porting Agent · gpt54 · 206.9 AIC · ⌖ 15.9 AIC · ⊞ 24.2K · ◷

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From f2743e4e5c4ca2bd8212d57a4f44a7f748f04ee7 Mon Sep 17 00:00:00 2001
From: "github-actions[bot]" <github-actions[bot]@users.noreply.github.com>
Date: Tue, 4 Aug 2026 06:26:17 +0000
Subject: [PATCH] [dotnet-port-api] Port .NET harness configurator

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
---
 agent/harness/harness.go                 | 101 ++++++++++++
 agent/harness/harness_example_test.go    |  17 +++
 agent/harness/harness_test.go            | 186 +++++++++++++++++++++++
 docs/dotnet-go-sdk-feature-comparison.md |   2 +-
 4 files changed, 305 insertions(+), 1 deletion(-)
 create mode 100644 agent/harness/harness.go
 create mode 100644 agent/harness/harness_example_test.go
 create mode 100644 agent/harness/harness_test.go

diff --git a/agent/harness/harness.go b/agent/harness/harness.go
new file mode 100644
index 000000000..3aeb93e41
--- /dev/null
+++ b/agent/harness/harness.go
@@ -0,0 +1,101 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+// Package harness provides a composed, cross-provider harness configuration
+// aligned with the upstream .NET HarnessAgent surface.
+package harness
+
+import (
+	"slices"
+
+	"github.com/microsoft/agent-framework-go/agent"
+	"github.com/microsoft/agent-framework-go/agent/harness/agentmode"
+	"github.com/microsoft/agent-framework-go/agent/harness/loop"
+	"github.com/microsoft/agent-framework-go/agent/harness/todo"
+	"github.com/microsoft/agent-framework-go/agent/harness/toolapproval"
+)
+
+// DefaultInstructions are the built-in harness-level instructions applied when
+// Config.DisableInstructions is false and Config.Instructions is empty.
+const DefaultInstructions = `You are a helpful AI assistant that uses tools to complete tasks.
+
+## General guidelines
+
+- Think through the task before acting. Break complex work into clear steps.
+- Use the tools available to you to gather information, perform actions, and verify results.
+- Explain your reasoning and thought process as you work thr
... (truncated)

[michelle-clayton-work]

Pull request #998 is linked to this issue and will close it when merged.