Feat: 8021 Schema v2 support for x402

examples/go/clients/builder-codes/go.mod

@@ -0,0 +1,35 @@
+module github.com/x402-foundation/x402/examples/go/clients/builder-codes
+
+go 1.25.4
+
+replace github.com/x402-foundation/x402/go => ../../../../go
+
+require (
+	github.com/joho/godotenv v1.5.1
+	github.com/x402-foundation/x402/go v0.0.0-00010101000000-000000000000
+)
+
+require (
+	github.com/Microsoft/go-winio v0.6.2 // indirect
+	github.com/ProjectZKM/Ziren/crates/go-runtime/zkvm_runtime v0.0.0-20251001021608-1fe7b43fc4d6 // indirect
+	github.com/StackExchange/wmi v1.2.1 // indirect
+	github.com/bits-and-blooms/bitset v1.20.0 // indirect
+	github.com/consensys/gnark-crypto v0.18.0 // indirect
+	github.com/crate-crypto/go-eth-kzg v1.4.0 // indirect
+	github.com/crate-crypto/go-ipa v0.0.0-20240724233137-53bbb0ceb27a // indirect
+	github.com/deckarep/golang-set/v2 v2.6.0 // indirect
+	github.com/decred/dcrd/dcrec/secp256k1/v4 v4.0.1 // indirect
+	github.com/ethereum/c-kzg-4844/v2 v2.1.5 // indirect
+	github.com/ethereum/go-ethereum v1.16.7 // indirect
+	github.com/ethereum/go-verkle v0.2.2 // indirect
+	github.com/go-ole/go-ole v1.3.0 // indirect
+	github.com/gorilla/websocket v1.4.2 // indirect
+	github.com/holiman/uint256 v1.3.2 // indirect
+	github.com/shirou/gopsutil v3.21.4-0.20210419000835-c7a38de76ee5+incompatible // indirect
+	github.com/supranational/blst v0.3.16-0.20250831170142-f48500c1fdbe // indirect
+	github.com/tklauser/go-sysconf v0.3.12 // indirect
+	github.com/tklauser/numcpus v0.6.1 // indirect
+	golang.org/x/crypto v0.46.0 // indirect
+	golang.org/x/sync v0.19.0 // indirect
+	golang.org/x/sys v0.39.0 // indirect
+)

examples/go/clients/builder-codes/main.go

@@ -0,0 +1,101 @@
+package main
+
+import (
+	"bytes"
+	"encoding/base64"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"os"
+
+	"github.com/joho/godotenv"
+	x402 "github.com/x402-foundation/x402/go"
+	x402http "github.com/x402-foundation/x402/go/http"
+	evm "github.com/x402-foundation/x402/go/mechanisms/evm/exact/client"
+	evmsigners "github.com/x402-foundation/x402/go/signers/evm"
+)
+
+// peek is a logging RoundTripper that prints the buildercode extension data
+// flowing in both directions: the codes the server declared in its 402, and
+// the codes the SDK forwarded back in the X-Payment header.
+type peek struct{ inner http.RoundTripper }
+
+func (p *peek) RoundTrip(req *http.Request) (*http.Response, error) {
+	if h := req.Header.Get("X-Payment"); h != "" {
+		if raw, err := base64.StdEncoding.DecodeString(h); err == nil {
+			var payload map[string]any
+			if json.Unmarshal(raw, &payload) == nil {
+				if ext, ok := payload["extensions"]; ok {
+					b, _ := json.MarshalIndent(ext, "", "  ")
+					fmt.Printf("➡️  payload.extensions sent:\n%s\n", b)
+				}
+			}
+		}
+	}
+
+	resp, err := p.inner.RoundTrip(req)
+	if err != nil {
+		return resp, err
+	}
+
+	// Server returns 402 with PaymentRequired in the Payment-Required header,
+	// not the body. Decode and log the extensions so we can confirm what the
+	// server declared.
+	if resp.StatusCode == http.StatusPaymentRequired {
+		if hdr := resp.Header.Get("Payment-Required"); hdr != "" {
+			if raw, err := base64.StdEncoding.DecodeString(hdr); err == nil {
+				var pr map[string]any
+				if json.Unmarshal(raw, &pr) == nil {
+					if ext, ok := pr["extensions"]; ok {
+						b, _ := json.MarshalIndent(ext, "", "  ")
+						fmt.Printf("⬅️  402 extensions:\n%s\n", b)
+					}
+				}
+			}
+		}
+		// Restore body in case downstream wants to read it
+		body, _ := io.ReadAll(resp.Body)
+		resp.Body = io.NopCloser(bytes.NewReader(body))
+	}
+	return resp, nil
+}
+
+func main() {
+	_ = godotenv.Load()
+
+	priv := os.Getenv("EVM_PRIVATE_KEY_CLIENT")
+	url := os.Getenv("SERVER_URL")
+	if priv == "" || url == "" {
+		fmt.Println("EVM_PRIVATE_KEY_CLIENT and SERVER_URL required")
+		os.Exit(1)
+	}
+
+	signer, err := evmsigners.NewClientSignerFromPrivateKey(priv)
+	if err != nil {
+		fmt.Printf("signer: %v\n", err)
+		os.Exit(1)
+	}
+
+	x402Client := x402.Newx402Client()
+	x402Client.Register("eip155:*", evm.NewExactEvmScheme(signer, nil))
+
+	httpInner := &http.Client{Transport: &peek{inner: http.DefaultTransport}}
+	wrapped := x402http.WrapHTTPClientWithPayment(httpInner, x402http.Newx402HTTPClient(x402Client))
+
+	resp, err := wrapped.Get(url)
+	if err != nil {
+		fmt.Printf("request: %v\n", err)
+		os.Exit(1)
+	}
+	defer resp.Body.Close()
+
+	body, _ := io.ReadAll(resp.Body)
+	fmt.Printf("\n✅ %s\n%s\n", resp.Status, body)
+
+	if pr := resp.Header.Get("PAYMENT-RESPONSE"); pr != "" {
+		if raw, err := base64.StdEncoding.DecodeString(pr); err == nil {
+			fmt.Printf("\n💰 settlement: %s\n", raw)
+		}
+	}
+}

examples/go/facilitator/builder-codes/go.mod

@@ -0,0 +1,68 @@
+module github.com/x402-foundation/x402/examples/go/facilitator/builder-codes
+
+go 1.25.4
+
+replace github.com/x402-foundation/x402/go => ../../../../go
+
+require (
+	github.com/ethereum/go-ethereum v1.17.3
+	github.com/gin-gonic/gin v1.11.0
+	github.com/joho/godotenv v1.5.1
+	github.com/x402-foundation/x402/go v0.0.0-00010101000000-000000000000
+)
+
+require (
+	github.com/Microsoft/go-winio v0.6.2 // indirect
+	github.com/ProjectZKM/Ziren/crates/go-runtime/zkvm_runtime v0.0.0-20251001021608-1fe7b43fc4d6 // indirect
+	github.com/StackExchange/wmi v1.2.1 // indirect
+	github.com/bits-and-blooms/bitset v1.20.0 // indirect
+	github.com/bytedance/sonic v1.14.0 // indirect
+	github.com/bytedance/sonic/loader v0.3.0 // indirect
+	github.com/cespare/xxhash/v2 v2.3.0 // indirect
+	github.com/cloudwego/base64x v0.1.6 // indirect
+	github.com/consensys/gnark-crypto v0.18.1 // indirect
+	github.com/crate-crypto/go-eth-kzg v1.5.0 // indirect
+	github.com/deckarep/golang-set/v2 v2.6.0 // indirect
+	github.com/decred/dcrd/dcrec/secp256k1/v4 v4.0.1 // indirect
+	github.com/ethereum/c-kzg-4844/v2 v2.1.6 // indirect
+	github.com/gabriel-vasile/mimetype v1.4.8 // indirect
+	github.com/gin-contrib/sse v1.1.0 // indirect
+	github.com/go-logr/logr v1.4.3 // indirect
+	github.com/go-logr/stdr v1.2.2 // indirect
+	github.com/go-ole/go-ole v1.3.0 // indirect
+	github.com/go-playground/locales v0.14.1 // indirect
+	github.com/go-playground/universal-translator v0.18.1 // indirect
+	github.com/go-playground/validator/v10 v10.27.0 // indirect
+	github.com/goccy/go-json v0.10.4 // indirect
+	github.com/goccy/go-yaml v1.18.0 // indirect
+	github.com/gorilla/websocket v1.4.2 // indirect
+	github.com/holiman/uint256 v1.3.2 // indirect
+	github.com/json-iterator/go v1.1.12 // indirect
+	github.com/klauspost/cpuid/v2 v2.3.0 // indirect
+	github.com/leodido/go-urn v1.4.0 // indirect
+	github.com/mattn/go-isatty v0.0.20 // indirect
+	github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd // indirect
+	github.com/modern-go/reflect2 v1.0.2 // indirect
+	github.com/pelletier/go-toml/v2 v2.2.4 // indirect
+	github.com/quic-go/qpack v0.5.1 // indirect
+	github.com/quic-go/quic-go v0.55.0 // indirect
+	github.com/shirou/gopsutil v3.21.4-0.20210419000835-c7a38de76ee5+incompatible // indirect
+	github.com/supranational/blst v0.3.16 // indirect
+	github.com/tklauser/go-sysconf v0.3.12 // indirect
+	github.com/tklauser/numcpus v0.6.1 // indirect
+	github.com/twitchyliquid64/golang-asm v0.15.1 // indirect
+	github.com/ugorji/go/codec v1.3.0 // indirect
+	go.opentelemetry.io/auto/sdk v1.2.1 // indirect
+	go.opentelemetry.io/otel v1.40.0 // indirect
+	go.opentelemetry.io/otel/metric v1.40.0 // indirect
+	go.opentelemetry.io/otel/trace v1.40.0 // indirect
+	golang.org/x/arch v0.20.0 // indirect
+	golang.org/x/crypto v0.47.0 // indirect
+	golang.org/x/mod v0.31.0 // indirect
+	golang.org/x/net v0.49.0 // indirect
+	golang.org/x/sync v0.19.0 // indirect
+	golang.org/x/sys v0.40.0 // indirect
+	golang.org/x/text v0.33.0 // indirect
+	golang.org/x/tools v0.40.0 // indirect
+	google.golang.org/protobuf v1.36.11 // indirect
+)