Speak protocol 3.0 and fall back to 2.0 only when that is the reflector's maximum.

A reflector that has moved to 3.0 will not accept a station that always announces 2.0, and a 2.x reflector still needs one explicit plaintext session.

Co-authored-by: Cursor <cursoragent@cursor.com>

station/software.go

@@ -1,6 +1,11 @@
 package station
 
-import jsonv2 "encoding/json/v2"
+import (
+	"bytes"
+
+	jsonv2 "encoding/json/v2"
+	"golang.org/x/sys/unix"
+)
 
 // SoftwareName and SoftwareVersion are the identity sent to the reflector
 // after login. Edit them here.
@@ -9,16 +14,56 @@ const (
 	SoftwareVersion = "1.0.0"
 )
 
+type nodeSoftware struct {
+	SW          string `json:"sw"`
+	SWVer       string `json:"swVer"`
+	ProjVer     string `json:"projVer"`
+	MachineArch string `json:"machineArch,omitempty"`
+}
+
 func softwareIdentityBody() ([]byte, error) {
-	raw, err := jsonv2.Marshal(struct {
-		SW    string `json:"sw"`
-		SWVer string `json:"swVer"`
-	}{
-		SW:    SoftwareName,
-		SWVer: SoftwareVersion,
-	})
+	raw, err := marshalNode(false)
 	if err != nil {
 		return nil, err
 	}
 	return appendString(nil, string(raw)), nil
 }
+
+func nodeInfoV3(iv, key []byte) ([]byte, error) {
+	raw, err := marshalNode(true)
+	if err != nil {
+		return nil, err
+	}
+	body := appendBlob(nil, iv)
+	body = appendBlob(body, key)
+	return appendString(body, string(raw)), nil
+}
+
+func marshalNode(arch bool) ([]byte, error) {
+	info := nodeSoftware{
+		SW:      SoftwareName,
+		SWVer:   SoftwareVersion,
+		ProjVer: SoftwareVersion,
+	}
+	if arch {
+		if name, ok := machineArch(); ok {
+			info.MachineArch = name
+		}
+	}
+	return jsonv2.Marshal(info)
+}
+
+func machineArch() (string, bool) {
+	var u unix.Utsname
+	if err := unix.Uname(&u); err != nil {
+		return "", false
+	}
+	b := u.Machine[:]
+	if i := bytes.IndexByte(b, 0); i >= 0 {
+		b = b[:i]
+	}
+	if len(b) == 0 {
+		return "", false
+	}
+	return string(b), true
+}