diff --git a/common/json/badjson/merge_objects.go b/common/json/badjson/merge_objects.go
new file mode 100644
index 0000000..37a5daf
--- /dev/null
+++ b/common/json/badjson/merge_objects.go
@@ -0,0 +1,60 @@
+package badjson
+
+import (
+	E "github.com/sagernet/sing/common/exceptions"
+	"github.com/sagernet/sing/common/json"
+)
+
+func MarshallObjects(objects ...any) ([]byte, error) {
+	if len(objects) == 1 {
+		return json.Marshal(objects[0])
+	}
+	var content JSONObject
+	for _, object := range objects {
+		objectMap, err := newJSONObject(object)
+		if err != nil {
+			return nil, err
+		}
+		content.PutAll(objectMap)
+	}
+	return content.MarshalJSON()
+}
+
+func UnmarshallExcluded(inputContent []byte, parentObject any, object any) error {
+	parentContent, err := newJSONObject(parentObject)
+	if err != nil {
+		return err
+	}
+	var content JSONObject
+	err = content.UnmarshalJSON(inputContent)
+	if err != nil {
+		return err
+	}
+	for _, key := range parentContent.Keys() {
+		content.Remove(key)
+	}
+	if object == nil {
+		if content.IsEmpty() {
+			return nil
+		}
+		return E.New("unexpected key: ", content.Keys()[0])
+	}
+	inputContent, err = content.MarshalJSON()
+	if err != nil {
+		return err
+	}
+	return json.UnmarshalDisallowUnknownFields(inputContent, object)
+}
+
+func newJSONObject(object any) (*JSONObject, error) {
+	inputContent, err := json.Marshal(object)
+	if err != nil {
+		return nil, err
+	}
+	var content JSONObject
+	err = content.UnmarshalJSON(inputContent)
+	if err != nil {
+		return nil, err
+	}
+	return &content, nil
+}
diff --git a/common/json/badoption/duration.go b/common/json/badoption/duration.go
new file mode 100644
index 0000000..d9f9e7b
--- /dev/null
+++ b/common/json/badoption/duration.go
@@ -0,0 +1,32 @@
+package badoption
+
+import (
+	"time"
+
+	"github.com/sagernet/sing/common/json"
+	"github.com/sagernet/sing/common/json/badoption/internal/my_time"
+)
+
+type Duration time.Duration
+
+func (d Duration) Build() time.Duration {
+	return time.Duration(d)
+}
+
+func (d Duration) MarshalJSON() ([]byte, error) {
+	return json.Marshal((time.Duration)(d).String())
+}
+
+func (d *Duration) UnmarshalJSON(bytes []byte) error {
+	var value string
+	err := json.Unmarshal(bytes, &value)
+	if err != nil {
+		return err
+	}
+	duration, err := my_time.ParseDuration(value)
+	if err != nil {
+		return err
+	}
+	*d = Duration(duration)
+	return nil
+}
diff --git a/common/json/badoption/http.go b/common/json/badoption/http.go
new file mode 100644
index 0000000..e8f0579
--- /dev/null
+++ b/common/json/badoption/http.go
@@ -0,0 +1,15 @@
+package badoption
+
+import "net/http"
+
+type HTTPHeader map[string]Listable[string]
+
+func (h HTTPHeader) Build() http.Header {
+	header := make(http.Header)
+	for name, values := range h {
+		for _, value := range values {
+			header.Add(name, value)
+		}
+	}
+	return header
+}
diff --git a/common/json/badoption/internal/my_time/format.go b/common/json/badoption/internal/my_time/format.go
new file mode 100644
index 0000000..aec8a6e
--- /dev/null
+++ b/common/json/badoption/internal/my_time/format.go
@@ -0,0 +1,226 @@
+package my_time
+
+import (
+	"errors"
+	"time"
+)
+
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+const durationDay = 24 * time.Hour
+
+var unitMap = map[string]uint64{
+	"ns": uint64(time.Nanosecond),
+	"us": uint64(time.Microsecond),
+	"µs": uint64(time.Microsecond), // U+00B5 = micro symbol
+	"μs": uint64(time.Microsecond), // U+03BC = Greek letter mu
+	"ms": uint64(time.Millisecond),
+	"s":  uint64(time.Second),
+	"m":  uint64(time.Minute),
+	"h":  uint64(time.Hour),
+	"d":  uint64(durationDay),
+}
+
+// ParseDuration parses a duration string.
+// A duration string is a possibly signed sequence of
+// decimal numbers, each with optional fraction and a unit suffix,
+// such as "300ms", "-1.5h" or "2h45m".
+// Valid time units are "ns", "us" (or "µs"), "ms", "s", "m", "h".
+func ParseDuration(s string) (time.Duration, error) {
+	// [-+]?([0-9]*(\.[0-9]*)?[a-z]+)+
+	orig := s
+	var d uint64
+	neg := false
+
+	// Consume [-+]?
+	if s != "" {
+		c := s[0]
+		if c == '-' || c == '+' {
+			neg = c == '-'
+			s = s[1:]
+		}
+	}
+	// Special case: if all that is left is "0", this is zero.
+	if s == "0" {
+		return 0, nil
+	}
+	if s == "" {
+		return 0, errors.New("time: invalid duration " + quote(orig))
+	}
+	for s != "" {
+		var (
+			v, f  uint64      // integers before, after decimal point
+			scale float64 = 1 // value = v + f/scale
+		)
+
+		var err error
+
+		// The next character must be [0-9.]
+		if !(s[0] == '.' || '0' <= s[0] && s[0] <= '9') {
+			return 0, errors.New("time: invalid duration " + quote(orig))
+		}
+		// Consume [0-9]*
+		pl := len(s)
+		v, s, err = leadingInt(s)
+		if err != nil {
+			return 0, errors.New("time: invalid duration " + quote(orig))
+		}
+		pre := pl != len(s) // whether we consumed anything before a period
+
+		// Consume (\.[0-9]*)?
+		post := false
+		if s != "" && s[0] == '.' {
+			s = s[1:]
+			pl := len(s)
+			f, scale, s = leadingFraction(s)
+			post = pl != len(s)
+		}
+		if !pre && !post {
+			// no digits (e.g. ".s" or "-.s")
+			return 0, errors.New("time: invalid duration " + quote(orig))
+		}
+
+		// Consume unit.
+		i := 0
+		for ; i < len(s); i++ {
+			c := s[i]
+			if c == '.' || '0' <= c && c <= '9' {
+				break
+			}
+		}
+		if i == 0 {
+			return 0, errors.New("time: missing unit in duration " + quote(orig))
+		}
+		u := s[:i]
+		s = s[i:]
+		unit, ok := unitMap[u]
+		if !ok {
+			return 0, errors.New("time: unknown unit " + quote(u) + " in duration " + quote(orig))
+		}
+		if v > 1<<63/unit {
+			// overflow
+			return 0, errors.New("time: invalid duration " + quote(orig))
+		}
+		v *= unit
+		if f > 0 {
+			// float64 is needed to be nanosecond accurate for fractions of hours.
+			// v >= 0 && (f*unit/scale) <= 3.6e+12 (ns/h, h is the largest unit)
+			v += uint64(float64(f) * (float64(unit) / scale))
+			if v > 1<<63 {
+				// overflow
+				return 0, errors.New("time: invalid duration " + quote(orig))
+			}
+		}
+		d += v
+		if d > 1<<63 {
+			return 0, errors.New("time: invalid duration " + quote(orig))
+		}
+	}
+	if neg {
+		return -time.Duration(d), nil
+	}
+	if d > 1<<63-1 {
+		return 0, errors.New("time: invalid duration " + quote(orig))
+	}
+	return time.Duration(d), nil
+}
+
+var errLeadingInt = errors.New("time: bad [0-9]*") // never printed
+
+// leadingInt consumes the leading [0-9]* from s.
+func leadingInt[bytes []byte | string](s bytes) (x uint64, rem bytes, err error) {
+	i := 0
+	for ; i < len(s); i++ {
+		c := s[i]
+		if c < '0' || c > '9' {
+			break
+		}
+		if x > 1<<63/10 {
+			// overflow
+			return 0, rem, errLeadingInt
+		}
+		x = x*10 + uint64(c) - '0'
+		if x > 1<<63 {
+			// overflow
+			return 0, rem, errLeadingInt
+		}
+	}
+	return x, s[i:], nil
+}
+
+// leadingFraction consumes the leading [0-9]* from s.
+// It is used only for fractions, so does not return an error on overflow,
+// it just stops accumulating precision.
+func leadingFraction(s string) (x uint64, scale float64, rem string) {
+	i := 0
+	scale = 1
+	overflow := false
+	for ; i < len(s); i++ {
+		c := s[i]
+		if c < '0' || c > '9' {
+			break
+		}
+		if overflow {
+			continue
+		}
+		if x > (1<<63-1)/10 {
+			// It's possible for overflow to give a positive number, so take care.
+			overflow = true
+			continue
+		}
+		y := x*10 + uint64(c) - '0'
+		if y > 1<<63 {
+			overflow = true
+			continue
+		}
+		x = y
+		scale *= 10
+	}
+	return x, scale, s[i:]
+}
+
+// These are borrowed from unicode/utf8 and strconv and replicate behavior in
+// that package, since we can't take a dependency on either.
+const (
+	lowerhex  = "0123456789abcdef"
+	runeSelf  = 0x80
+	runeError = '\uFFFD'
+)
+
+func quote(s string) string {
+	buf := make([]byte, 1, len(s)+2) // slice will be at least len(s) + quotes
+	buf[0] = '"'
+	for i, c := range s {
+		if c >= runeSelf || c < ' ' {
+			// This means you are asking us to parse a time.Duration or
+			// time.Location with unprintable or non-ASCII characters in it.
+			// We don't expect to hit this case very often. We could try to
+			// reproduce strconv.Quote's behavior with full fidelity but
+			// given how rarely we expect to hit these edge cases, speed and
+			// conciseness are better.
+			var width int
+			if c == runeError {
+				width = 1
+				if i+2 < len(s) && s[i:i+3] == string(runeError) {
+					width = 3
+				}
+			} else {
+				width = len(string(c))
+			}
+			for j := 0; j < width; j++ {
+				buf = append(buf, `\x`...)
+				buf = append(buf, lowerhex[s[i+j]>>4])
+				buf = append(buf, lowerhex[s[i+j]&0xF])
+			}
+		} else {
+			if c == '"' || c == '\\' {
+				buf = append(buf, '\\')
+			}
+			buf = append(buf, string(c)...)
+		}
+	}
+	buf = append(buf, '"')
+	return string(buf)
+}
diff --git a/common/json/badoption/listable.go b/common/json/badoption/listable.go
new file mode 100644
index 0000000..a4e88e3
--- /dev/null
+++ b/common/json/badoption/listable.go
@@ -0,0 +1,30 @@
+package badoption
+
+import (
+	E "github.com/sagernet/sing/common/exceptions"
+	"github.com/sagernet/sing/common/json"
+)
+
+type Listable[T any] []T
+
+func (l Listable[T]) MarshalJSON() ([]byte, error) {
+	arrayList := []T(l)
+	if len(arrayList) == 1 {
+		return json.Marshal(arrayList[0])
+	}
+	return json.Marshal(arrayList)
+}
+
+func (l *Listable[T]) UnmarshalJSON(content []byte) error {
+	err := json.UnmarshalDisallowUnknownFields(content, (*[]T)(l))
+	if err == nil {
+		return nil
+	}
+	var singleItem T
+	newError := json.UnmarshalDisallowUnknownFields(content, &singleItem)
+	if newError != nil {
+		return E.Errors(err, newError)
+	}
+	*l = []T{singleItem}
+	return nil
+}
diff --git a/common/json/badoption/netip.go b/common/json/badoption/netip.go
new file mode 100644
index 0000000..61aef82
--- /dev/null
+++ b/common/json/badoption/netip.go
@@ -0,0 +1,84 @@
+package badoption
+
+import (
+	"net/netip"
+
+	"github.com/sagernet/sing/common/json"
+)
+
+type Addr netip.Addr
+
+func (a *Addr) Build(defaultAddr netip.Addr) netip.Addr {
+	if a == nil {
+		return defaultAddr
+	}
+	return netip.Addr(*a)
+}
+
+func (a *Addr) MarshalJSON() ([]byte, error) {
+	return json.Marshal(netip.Addr(*a).String())
+}
+
+func (a *Addr) UnmarshalJSON(content []byte) error {
+	var value string
+	err := json.Unmarshal(content, &value)
+	if err != nil {
+		return err
+	}
+	addr, err := netip.ParseAddr(value)
+	if err != nil {
+		return err
+	}
+	*a = Addr(addr)
+	return nil
+}
+
+type Prefix netip.Prefix
+
+func (p *Prefix) MarshalJSON() ([]byte, error) {
+	return json.Marshal(netip.Prefix(*p).String())
+}
+
+func (p *Prefix) UnmarshalJSON(content []byte) error {
+	var value string
+	err := json.Unmarshal(content, &value)
+	if err != nil {
+		return err
+	}
+	prefix, err := netip.ParsePrefix(value)
+	if err != nil {
+		return err
+	}
+	*p = Prefix(prefix)
+	return nil
+}
+
+type Prefixable netip.Prefix
+
+func (p *Prefixable) MarshalJSON() ([]byte, error) {
+	prefix := netip.Prefix(*p)
+	if prefix.Bits() == prefix.Addr().BitLen() {
+		return json.Marshal(prefix.Addr().String())
+	} else {
+		return json.Marshal(prefix.String())
+	}
+}
+
+func (p *Prefixable) UnmarshalJSON(content []byte) error {
+	var value string
+	err := json.Unmarshal(content, &value)
+	if err != nil {
+		return err
+	}
+	prefix, prefixErr := netip.ParsePrefix(value)
+	if prefixErr == nil {
+		*p = Prefixable(prefix)
+		return nil
+	}
+	addr, addrErr := netip.ParseAddr(value)
+	if addrErr == nil {
+		*p = Prefixable(netip.PrefixFrom(addr, addr.BitLen()))
+		return nil
+	}
+	return prefixErr
+}
diff --git a/common/json/badoption/regexp.go b/common/json/badoption/regexp.go
new file mode 100644
index 0000000..67dda5f
--- /dev/null
+++ b/common/json/badoption/regexp.go
@@ -0,0 +1,31 @@
+package badoption
+
+import (
+	"regexp"
+
+	"github.com/sagernet/sing/common/json"
+)
+
+type Regexp regexp.Regexp
+
+func (r *Regexp) Build() *regexp.Regexp {
+	return (*regexp.Regexp)(r)
+}
+
+func (r *Regexp) MarshalJSON() ([]byte, error) {
+	return json.Marshal((*regexp.Regexp)(r).String())
+}
+
+func (r *Regexp) UnmarshalJSON(content []byte) error {
+	var stringValue string
+	err := json.Unmarshal(content, &stringValue)
+	if err != nil {
+		return err
+	}
+	regex, err := regexp.Compile(stringValue)
+	if err != nil {
+		return err
+	}
+	*r = Regexp(*regex)
+	return nil
+}