diff --git a/protocol/invocation/rpcinvocation.go b/protocol/invocation/rpcinvocation.go
index 8219c8c221..242489c4ea 100644
--- a/protocol/invocation/rpcinvocation.go
+++ b/protocol/invocation/rpcinvocation.go
@@ -267,10 +267,11 @@ func (r *RPCInvocation) MergeAttachmentFromContext(ctx context.Context) {
 		return
 	}
 	for k, v := range header {
+		key := strings.ToLower(k)
 		if len(v) == 1 {
-			r.SetAttachment(k, v[0])
+			r.SetAttachment(key, v[0])
 		} else {
-			r.SetAttachment(k, v)
+			r.SetAttachment(key, v)
 		}
 	}
 }
diff --git a/protocol/invocation/rpcinvocation_test.go b/protocol/invocation/rpcinvocation_test.go
index c20ac483d1..2b1373d5b9 100644
--- a/protocol/invocation/rpcinvocation_test.go
+++ b/protocol/invocation/rpcinvocation_test.go
@@ -371,13 +371,9 @@ func TestRPCInvocation_GetAttachmentAsContext(t *testing.T) {
 	header := triple_protocol.ExtractFromOutgoingContext(ctx)
 	assert.NotNil(t, header)
 
-	// Verify that string attachments are in the header
-	// NewOutgoingContext stores keys as lowercase, so check both ways
-	assert.Contains(t, header, "key1")
-	assert.Equal(t, []string{"value1"}, header["key1"]) //nolint:staticcheck
-
-	assert.Contains(t, header, "key2")
-	assert.Equal(t, []string{"value2", "value3"}, header["key2"]) //nolint:staticcheck
+	// Verify that string attachments are in the header.
+	assert.Equal(t, []string{"value1"}, header.Values("key1"))
+	assert.Equal(t, []string{"value2", "value3"}, header.Values("key2"))
 
 	// key3 (int) should not be in the header since it's not a string
 	assert.NotContains(t, header, "key3")
diff --git a/protocol/triple/triple_protocol/header.go b/protocol/triple/triple_protocol/header.go
index adc9f7ecb7..79757716c0 100644
--- a/protocol/triple/triple_protocol/header.go
+++ b/protocol/triple/triple_protocol/header.go
@@ -19,7 +19,6 @@ import (
 	"encoding/base64"
 	"fmt"
 	"net/http"
-	"strings"
 )
 
 // EncodeBinaryHeader base64-encodes the data. It always emits unpadded values.
@@ -101,10 +100,13 @@ func newIncomingContext(ctx context.Context, data http.Header) context.Context {
 	extraData, ok := ctx.Value(extraDataKey{}).(map[string]http.Header)
 	if !ok {
 		extraData = map[string]http.Header{}
+	} else {
+		extraData = cloneExtraData(extraData)
 	}
 
 	for key, vals := range data {
-		header[strings.ToLower(key)] = vals
+		// Context headers use canonical keys so http.Header.Get/Values work as expected.
+		header[http.CanonicalHeaderKey(key)] = append([]string(nil), vals...)
 	}
 
 	extraData[headerIncomingKey] = header
@@ -128,7 +130,8 @@ func NewOutgoingContext(ctx context.Context, data http.Header) context.Context {
 	var header = http.Header{}
 
 	for key, vals := range data {
-		header[strings.ToLower(key)] = append([]string(nil), vals...)
+		// Context headers use canonical keys so http.Header.Get/Values work as expected.
+		header[http.CanonicalHeaderKey(key)] = append([]string(nil), vals...)
 	}
 
 	extraData, ok := ctx.Value(extraDataKey{}).(map[string]http.Header)
@@ -182,8 +185,8 @@ func AppendToOutgoingContext(ctx context.Context, kv ...string) context.Context
 		extraData[headerOutgoingKey] = header
 	}
 	for i := 0; i < len(kv); i += 2 {
-		// todo(DMwangnima): think about lowering
-		header.Add(strings.ToLower(kv[i]), kv[i+1])
+		key := http.CanonicalHeaderKey(kv[i])
+		header[key] = append(header[key], kv[i+1])
 	}
 	return ctx
 }
diff --git a/protocol/triple/triple_protocol/header_test.go b/protocol/triple/triple_protocol/header_test.go
index 3b73b3570f..febd96cc70 100644
--- a/protocol/triple/triple_protocol/header_test.go
+++ b/protocol/triple/triple_protocol/header_test.go
@@ -16,6 +16,8 @@ package triple_protocol
 
 import (
 	"bytes"
+	"context"
+	"fmt"
 	"net/http"
 	"testing"
 	"testing/quick"
@@ -58,3 +60,38 @@ func TestHeaderMerge(t *testing.T) {
 	}
 	assert.Equal(t, header, expect)
 }
+
+func TestNewIncomingContextClonesHeaders(t *testing.T) {
+	baseCtx := NewOutgoingContext(context.Background(), http.Header{
+		"Request-Id": []string{"outgoing"},
+	})
+	inputValues := []string{"incoming"}
+	input := http.Header{
+		"request-id": inputValues,
+	}
+
+	ctx := newIncomingContext(baseCtx, input)
+	incoming, ok := FromIncomingContext(ctx)
+	assert.True(t, ok)
+	incoming.Values("Request-Id")[0] = "changed"
+	incoming.Add("Another", "value")
+
+	assert.Equal(t, []string{"incoming"}, inputValues)
+	outgoing := ExtractFromOutgoingContext(baseCtx)
+	assert.Equal(t, []string{"outgoing"}, outgoing.Values("Request-Id"))
+}
+
+func ExampleNewOutgoingContext() {
+	ctx := NewOutgoingContext(context.Background(), http.Header{
+		"hello": []string{"triple"},
+	})
+	ctx = AppendToOutgoingContext(ctx, "hello", "dubbo", "hey", "hessian")
+
+	headers := ExtractFromOutgoingContext(ctx)
+	fmt.Println(headers.Values("hello"))
+	fmt.Println(headers.Get("hey"))
+
+	// Output:
+	// [triple dubbo]
+	// hessian
+}
diff --git a/protocol/triple/triple_protocol/protocol_grpc.go b/protocol/triple/triple_protocol/protocol_grpc.go
index a663d3221d..44f5bd4efb 100644
--- a/protocol/triple/triple_protocol/protocol_grpc.go
+++ b/protocol/triple/triple_protocol/protocol_grpc.go
@@ -476,6 +476,7 @@ func (hc *grpcHandlerConn) ExportableHeader() http.Header {
 	res := make(http.Header)
 	hdr := hc.request.Header
 	for key, vals := range hdr {
+		// Exported attachments stay lowercase to match Dubbo/gRPC metadata keys.
 		key = strings.ToLower(key)
 		if IsReservedHeader(key) && !IsWhitelistedHeader(key) {
 			continue
@@ -492,6 +493,7 @@ func (hc *grpcHandlerConn) ExportableHeader() http.Header {
 // reserved by gRPC protocol. Any other headers are classified as the
 // user-specified metadata.
 func IsReservedHeader(hdr string) bool {
+	hdr = strings.ToLower(hdr)
 	if hdr != "" && hdr[0] == ':' {
 		return true
 	}
diff --git a/protocol/triple/triple_protocol/protocol_grpc_test.go b/protocol/triple/triple_protocol/protocol_grpc_test.go
index 6a454831ab..f0aea1ac82 100644
--- a/protocol/triple/triple_protocol/protocol_grpc_test.go
+++ b/protocol/triple/triple_protocol/protocol_grpc_test.go
@@ -124,6 +124,16 @@ func TestGRPCHandlerSender(t *testing.T) {
 	})
 }
 
+func TestIsReservedHeaderCanonicalizesInput(t *testing.T) {
+	t.Parallel()
+
+	for _, header := range []string{"Content-Type", "Grpc-Status", "TE"} {
+		if !IsReservedHeader(header) {
+			t.Fatalf("expected %q to be reserved", header)
+		}
+	}
+}
+
 func testGRPCHandlerConnMetadata(t *testing.T, conn handlerConnCloser) {
 	// Closing the sender shouldn't unpredictably mutate user-visible headers or
 	// trailers.
diff --git a/protocol/triple/triple_protocol/triple.go b/protocol/triple/triple_protocol/triple.go
index 3ee8f0ce43..99b5bf642c 100644
--- a/protocol/triple/triple_protocol/triple.go
+++ b/protocol/triple/triple_protocol/triple.go
@@ -230,6 +230,13 @@ func (r *Response) Any() any {
 // Header returns the HTTP headers for this response. Headers beginning with
 // "Triple-" and "Grpc-" are reserved for use by the Triple and gRPC
 // protocols: applications may read them but shouldn't write them.
+//
+// Unary clients can pass a response wrapper to the generated client method,
+// then read response headers after the call returns:
+//
+//	response := NewResponse(&greet.GreetResponse{})
+//	err := client.Greet(ctx, NewRequest(&greet.GreetRequest{}), response)
+//	values := response.Header().Values("hello")
 func (r *Response) Header() http.Header {
 	if r.header == nil {
 		r.header = make(http.Header)
@@ -244,6 +251,13 @@ func (r *Response) Header() http.Header {
 // Trailers beginning with "Triple-" and "Grpc-" are reserved for use by the
 // Triple and gRPC protocols: applications may read them but shouldn't write
 // them.
+//
+// Unary clients can read trailers from the same response wrapper after the
+// generated client method returns:
+//
+//	response := NewResponse(&greet.GreetResponse{})
+//	err := client.Greet(ctx, NewRequest(&greet.GreetRequest{}), response)
+//	values := response.Trailer().Values("end")
 func (r *Response) Trailer() http.Header {
 	if r.trailer == nil {
 		r.trailer = make(http.Header)