diff --git a/agent/harness/harness.go b/agent/harness/harness.go
new file mode 100644
index 00000000..ca81a6f3
--- /dev/null
+++ b/agent/harness/harness.go
@@ -0,0 +1,104 @@
+// 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 through tasks.
+- Explain what you learned and what you are going to do next between tool calls, so the user can follow along with your thought process.
+- Avoid making more than 4 tool calls in a row without explaining what you are doing.
+- If a tool call fails or returns unexpected results, adapt your approach rather than repeating the same call.
+- When you have completed the task, present a clear and concise summary of what you did and what you found.`
+
+// Config configures the composed harness behavior applied by [Configure].
+type Config struct {
+	// Instructions overrides DefaultInstructions when non-empty.
+	Instructions string
+
+	// DisableInstructions omits harness-level instructions entirely.
+	DisableInstructions bool
+
+	// DisableTodoProvider omits the default todo tracking context provider.
+	DisableTodoProvider bool
+
+	// TodoOptions customizes the default todo provider when it is enabled.
+	TodoOptions *todo.Options
+
+	// DisableAgentModeProvider omits the default agent-mode context provider.
+	DisableAgentModeProvider bool
+
+	// AgentModeConfig customizes the default agent-mode provider when it is enabled.
+	AgentModeConfig agentmode.Config
+
+	// DisableToolApproval omits the default tool-approval middleware.
+	DisableToolApproval bool
+
+	// ToolApprovalConfig customizes the default tool-approval middleware when it is enabled.
+	ToolApprovalConfig toolapproval.Config
+
+	// LoopConfig enables loop middleware when non-nil and its Evaluators slice is
+	// non-empty. Evaluators must be non-nil; loop.New rejects nil evaluators at
+	// runtime. The loop middleware is appended before tool-approval middleware so
+	// loop reinvocation remains outside approval handling, mirroring the upstream
+	// .NET HarnessAgent ordering.
+	LoopConfig *loop.Config
+}
+
+// Configure returns a copy of cfg with the standard harness instructions,
+// context providers, and middlewares applied.
+//
+// It is intended for composing provider-specific agent configs, for example:
+//
+//	openaiprovider.AgentConfig{
+//		Config: harness.Configure(agent.Config{Name: "Research"}, harness.Config{}),
+//		Model:  "gpt-5",
+//	}
+func Configure(cfg agent.Config, harnessCfg Config) agent.Config {
+	out := cfg
+	out.RunOptions = slices.Clone(cfg.RunOptions)
+	out.ContextProviders = slices.Clone(cfg.ContextProviders)
+	out.Middlewares = slices.Clone(cfg.Middlewares)
+
+	if !harnessCfg.DisableInstructions {
+		instructions := DefaultInstructions
+		if harnessCfg.Instructions != "" {
+			instructions = harnessCfg.Instructions
+		}
+		out.RunOptions = append([]agent.Option{agent.WithInstructions(instructions)}, out.RunOptions...)
+	}
+
+	if !harnessCfg.DisableTodoProvider {
+		out.ContextProviders = append(out.ContextProviders, todo.New(harnessCfg.TodoOptions))
+	}
+	if !harnessCfg.DisableAgentModeProvider {
+		out.ContextProviders = append(out.ContextProviders, agentmode.New(harnessCfg.AgentModeConfig))
+	}
+	if harnessCfg.LoopConfig != nil && len(harnessCfg.LoopConfig.Evaluators) > 0 {
+		loopCfg := *harnessCfg.LoopConfig
+		loopCfg.Evaluators = slices.Clone(loopCfg.Evaluators)
+		out.Middlewares = append(out.Middlewares, loop.New(loopCfg))
+	}
+	if !harnessCfg.DisableToolApproval {
+		out.Middlewares = append(out.Middlewares, toolapproval.New(harnessCfg.ToolApprovalConfig))
+	}
+
+	return out
+}
diff --git a/agent/harness/harness_example_test.go b/agent/harness/harness_example_test.go
new file mode 100644
index 00000000..1ac9e5fd
--- /dev/null
+++ b/agent/harness/harness_example_test.go
@@ -0,0 +1,17 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+package harness_test
+
+import (
+	"fmt"
+
+	"github.com/microsoft/agent-framework-go/agent"
+	"github.com/microsoft/agent-framework-go/agent/harness"
+)
+
+func ExampleConfigure() {
+	cfg := harness.Configure(agent.Config{Name: "ResearchAgent"}, harness.Config{})
+
+	fmt.Println(len(cfg.ContextProviders), len(cfg.Middlewares), len(cfg.RunOptions))
+	// Output: 2 1 1
+}
diff --git a/agent/harness/harness_test.go b/agent/harness/harness_test.go
new file mode 100644
index 00000000..0fec7687
--- /dev/null
+++ b/agent/harness/harness_test.go
@@ -0,0 +1,186 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+package harness_test
+
+import (
+	"context"
+	"iter"
+	"slices"
+	"testing"
+
+	"github.com/microsoft/agent-framework-go/agent"
+	"github.com/microsoft/agent-framework-go/agent/harness"
+	"github.com/microsoft/agent-framework-go/agent/harness/loop"
+	"github.com/microsoft/agent-framework-go/internal/agenttest"
+	"github.com/microsoft/agent-framework-go/message"
+	"github.com/microsoft/agent-framework-go/tool"
+)
+
+func TestConfigure_DefaultsApplyHarnessSurface(t *testing.T) {
+	var capturedMessages []*message.Message
+	var capturedInstructions []string
+	var capturedTools []tool.Tool
+
+	a := agent.New(agent.ProviderConfig{
+		ProviderName: "test",
+		Run: func(_ context.Context, msgs []*message.Message, opts ...agent.Option) iter.Seq2[*agent.ResponseUpdate, error] {
+			capturedMessages = msgs
+			capturedInstructions = slices.Collect(agent.AllOptions(opts, agent.WithInstructions))
+			capturedTools = slices.Collect(agent.AllOptions(opts, agent.WithTool))
+			return func(yield func(*agent.ResponseUpdate, error) bool) {
+				yield(&agent.ResponseUpdate{
+					Role:     message.RoleAssistant,
+					Contents: []message.Content{&message.TextContent{Text: "done"}},
+				}, nil)
+			}
+		},
+	}, harness.Configure(agent.Config{}, harness.Config{}))
+
+	_, err := a.RunText(t.Context(), "hello", agent.WithSession(agenttest.CreateSession())).Collect()
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+
+	if got := textMessages(capturedMessages); !slices.Equal(got, []string{"hello", "### Current todo list\n- none yet"}) {
+		t.Fatalf("messages = %q, want hello plus todo summary", got)
+	}
+
+	if len(capturedTools) != 7 {
+		t.Fatalf("expected 7 harness tools, got %d", len(capturedTools))
+	}
+	for _, name := range []string{
+		"todos_add",
+		"todos_complete",
+		"todos_remove",
+		"todos_get_remaining",
+		"todos_get_all",
+		"mode_set",
+		"mode_get",
+	} {
+		if !hasToolNamed(capturedTools, name) {
+			t.Fatalf("expected tool %q to be configured", name)
+		}
+	}
+
+	if len(capturedInstructions) < 3 {
+		t.Fatalf("expected harness instructions plus provider instructions, got %d entries", len(capturedInstructions))
+	}
+	if capturedInstructions[0] != harness.DefaultInstructions {
+		t.Fatalf("first instructions = %q, want harness default instructions", capturedInstructions[0])
+	}
+}
+
+func TestConfigure_DisableFlagsOmitHarnessDefaults(t *testing.T) {
+	cfg := harness.Configure(agent.Config{}, harness.Config{
+		DisableInstructions:      true,
+		DisableTodoProvider:      true,
+		DisableAgentModeProvider: true,
+		DisableToolApproval:      true,
+		LoopConfig:               &loop.Config{},
+	})
+
+	if got := slices.Collect(agent.AllOptions(cfg.RunOptions, agent.WithInstructions)); len(got) != 0 {
+		t.Fatalf("expected no harness instructions, got %q", got)
+	}
+	if len(cfg.ContextProviders) != 0 {
+		t.Fatalf("expected no context providers, got %d", len(cfg.ContextProviders))
+	}
+	if len(cfg.Middlewares) != 0 {
+		t.Fatalf("expected no middlewares, got %d", len(cfg.Middlewares))
+	}
+}
+
+func TestConfigure_PrependsInstructionsAndAppendsToExistingConfig(t *testing.T) {
+	customProvider := agent.NewContextProvider(agent.ContextProviderConfig{SourceID: "custom"})
+	customMiddleware := agent.MiddlewareFunc(func(next agent.RunFunc, ctx context.Context, messages []*message.Message, opts ...agent.Option) iter.Seq2[*agent.ResponseUpdate, error] {
+		return next(ctx, messages, opts...)
+	})
+
+	cfg := harness.Configure(agent.Config{
+		RunOptions:       []agent.Option{agent.WithInstructions("custom instructions")},
+		ContextProviders: []agent.ContextProvider{customProvider},
+		Middlewares:      []agent.Middleware{customMiddleware},
+	}, harness.Config{
+		Instructions: "harness instructions",
+		LoopConfig: &loop.Config{
+			Evaluators: []loop.Evaluator{
+				loop.EvaluatorFunc(func(context.Context, *loop.Context) (loop.Evaluation, error) {
+					return loop.Stop(), nil
+				}),
+			},
+		},
+	})
+
+	gotInstructions := slices.Collect(agent.AllOptions(cfg.RunOptions, agent.WithInstructions))
+	if !slices.Equal(gotInstructions[:2], []string{"harness instructions", "custom instructions"}) {
+		t.Fatalf("instructions = %q, want harness instructions before custom instructions", gotInstructions)
+	}
+	if len(cfg.ContextProviders) != 3 {
+		t.Fatalf("expected existing provider plus 2 harness providers, got %d", len(cfg.ContextProviders))
+	}
+	if len(cfg.Middlewares) != 3 {
+		t.Fatalf("expected existing middleware plus loop and tool-approval middleware, got %d", len(cfg.Middlewares))
+	}
+}
+
+func TestConfigure_LoopConfigReinvokesAgent(t *testing.T) {
+	var calls int
+	a := agent.New(agent.ProviderConfig{
+		ProviderName: "test",
+		Run: func(_ context.Context, _ []*message.Message, _ ...agent.Option) iter.Seq2[*agent.ResponseUpdate, error] {
+			calls++
+			text := "first"
+			if calls > 1 {
+				text = "second"
+			}
+			return func(yield func(*agent.ResponseUpdate, error) bool) {
+				yield(&agent.ResponseUpdate{
+					Role:     message.RoleAssistant,
+					Contents: []message.Content{&message.TextContent{Text: text}},
+				}, nil)
+			}
+		},
+	}, harness.Configure(agent.Config{}, harness.Config{
+		DisableInstructions:      true,
+		DisableTodoProvider:      true,
+		DisableAgentModeProvider: true,
+		DisableToolApproval:      true,
+		LoopConfig: &loop.Config{
+			Evaluators: []loop.Evaluator{
+				loop.EvaluatorFunc(func(_ context.Context, lc *loop.Context) (loop.Evaluation, error) {
+					if lc.Iteration == 1 {
+						return loop.Continue("try again"), nil
+					}
+					return loop.Stop(), nil
+				}),
+			},
+		},
+	}))
+
+	_, err := a.RunText(t.Context(), "hello", agent.WithSession(agenttest.CreateSession())).Collect()
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if calls != 2 {
+		t.Fatalf("expected loop middleware to re-invoke the agent once, got %d calls", calls)
+	}
+}
+
+func textMessages(messages []*message.Message) []string {
+	var out []string
+	for _, msg := range messages {
+		if msg == nil || len(msg.Contents) == 0 {
+			continue
+		}
+		if text, ok := msg.Contents[0].(*message.TextContent); ok {
+			out = append(out, text.Text)
+		}
+	}
+	return out
+}
+
+func hasToolNamed(tools []tool.Tool, name string) bool {
+	return slices.ContainsFunc(tools, func(t tool.Tool) bool {
+		return t != nil && t.Name() == name
+	})
+}
diff --git a/docs/dotnet-go-sdk-feature-comparison.md b/docs/dotnet-go-sdk-feature-comparison.md
index 97afef6b..e3e163bb 100644
--- a/docs/dotnet-go-sdk-feature-comparison.md
+++ b/docs/dotnet-go-sdk-feature-comparison.md
@@ -76,7 +76,7 @@ Intentional contract choices in this parity pass:
 | Logging | Microsoft.Extensions.Logging source-generated logs. | `slog` logger support through `agent.Config.Logger`, automatic agent run logs, and provider/middleware diagnostics. | Partial | Logging ecosystems differ. |
 | OpenTelemetry for agents | Agent/workflow observability samples and OpenTelemetry workflow builder extension. | `provider/otelprovider`, `workflow/observability/opentelemetry`, workflow builder instrumentation via `WithTelemetry`, trace context propagation in workflow context. | Aligned | API shape differs: Go passes a tracer from the OpenTelemetry adapter separately from `TelemetryOptions` and keeps workflow observability internals unexported. |
 | Evaluation | Agent evaluation extensions, eval checks, local/function evaluators, conversation splitters, workflow evaluation samples, Foundry quality samples. | No evaluation package. | .NET only | No Go equivalent found. |
-| Harness utilities | Agent mode, file access, file memory, file store, subagents, todo, tool approval harness providers, loop harness. | `agent/harness/agentmode`, `agent/harness/todo`, `agent/harness/toolapproval`, `agent/harness/toolautocall`, `agent/harness/loop`; message injection is supplied through `agent.Config`. | Partial | Go now has packaged harness support for agent mode, todo tracking, tool approval, tool auto-call, message injection, and loop reinvocation with delegate/completion-marker evaluators. It still lacks file access, file memory, file store, subagent harness utilities, and the .NET AI-judge loop evaluator. Agent mode tool names (`mode_set`/`mode_get`), default instructions, and mode descriptions are aligned with .NET (#6071). |
+| Harness utilities | Agent mode, file access, file memory, file store, subagents, todo, tool approval harness providers, loop harness. | `agent/harness`, `agent/harness/agentmode`, `agent/harness/todo`, `agent/harness/toolapproval`, `agent/harness/toolautocall`, `agent/harness/loop`; message injection is supplied through `agent.Config`. | Partial | Go now has a top-level harness configurator plus packaged support for agent mode, todo tracking, tool approval, tool auto-call, message injection, and loop reinvocation with delegate/completion-marker evaluators. It still lacks file access, file memory, file store, subagent harness utilities, and the .NET AI-judge loop evaluator. Agent mode tool names (`mode_set`/`mode_get`), default instructions, and mode descriptions are aligned with .NET (#6071). |
 | RAG | Basic text RAG, custom vector store RAG, custom data source RAG, Foundry service RAG, Neo4j graph RAG samples. | No RAG package or sample found. | .NET only | Go has data/file/vector content types but no RAG workflow package or samples. |
 | Purview | `Microsoft.Agents.AI.Purview` models and end-to-end sample. | No equivalent package. | .NET only | No Go governance/Purview integration. |
 | Cosmos DB storage | Cosmos chat history provider and workflow checkpoint store. | No built-in Cosmos package. | .NET only | Go has public in-memory and JSON/file workflow checkpoint stores plus a custom store interface, but no Cosmos DB provider. |