diff --git a/.beads/issues.jsonl b/.beads/issues.jsonl
deleted file mode 100644
index e69de29..0000000
diff --git a/ucl/builtins.go b/ucl/builtins.go
index c984394..4c012bc 100644
--- a/ucl/builtins.go
+++ b/ucl/builtins.go
@@ -369,6 +369,10 @@ func strBuiltin(ctx context.Context, args invocationArgs) (Object, error) {
 		return StringObject(""), nil
 	}
 
+	if bs, isBS := args.args[0].(BytesObject); isBS {
+		return StringObject(bs), nil
+	}
+
 	return StringObject(args.args[0].String()), nil
 }
 
diff --git a/ucl/builtins/bytes.go b/ucl/builtins/bytes.go
new file mode 100644
index 0000000..98d1a3c
--- /dev/null
+++ b/ucl/builtins/bytes.go
@@ -0,0 +1,98 @@
+package builtins
+
+import (
+	"context"
+	"crypto/md5"
+	"crypto/sha1"
+	"crypto/sha256"
+	"encoding/base64"
+	"errors"
+
+	"ucl.lmika.dev/ucl"
+)
+
+type bytesHandlers struct{}
+
+/// :module bytes
+//
+// Perform operations over byte slices.
+
+func Bytes() ucl.Module {
+	return ucl.Module{
+		Name: "bytes",
+		Builtins: map[string]ucl.BuiltinHandler{
+			"hash":   bytesHandlers{}.hash,
+			"base64": bytesHandlers{}.base64,
+		},
+	}
+}
+
+// :fn hash
+//
+// :syntax INPUT ALGORITHM
+//
+// Returns a byte slice containing the result of hashing the input with the given algorithm.
+//
+// The input can either be a byte slice or a string. The supported algorithms are as follows:
+//
+// - md5
+// - sha1
+// - sha256
+func (b bytesHandlers) hash(ctx context.Context, args ucl.CallArgs) (any, error) {
+	inputBts, args, err := consumeStringOrBytes(args)
+	if err != nil {
+		return nil, err
+	}
+
+	var algor string
+	if err := args.Bind(&algor); err != nil {
+		return nil, err
+	}
+
+	switch algor {
+	case "md5":
+		res := md5.Sum(inputBts)
+		return ucl.BytesObject(res[:]), nil
+	case "sha1":
+		res := sha1.Sum(inputBts)
+		return ucl.BytesObject(res[:]), nil
+	case "sha256":
+		res := sha256.Sum256(inputBts)
+		return ucl.BytesObject(res[:]), nil
+	}
+
+	return nil, errors.New("unsupported algorithm")
+}
+
+// :fn base64
+//
+// :syntax INPUT
+//
+// Returns a string containing the base64 encoding of the input.
+//
+// The input can either be a byte slice or a string. The result will be a base64 encoded string
+// using standard encoding.
+func (c bytesHandlers) base64(ctx context.Context, args ucl.CallArgs) (any, error) {
+	inputBts, args, err := consumeStringOrBytes(args)
+	if err != nil {
+		return nil, err
+	}
+
+	res := base64.StdEncoding.EncodeToString(inputBts)
+	return res, nil
+}
+
+func consumeStringOrBytes(args ucl.CallArgs) (bs ucl.BytesObject, _ ucl.CallArgs, _ error) {
+	if objs := args.RestAsObjects(); len(objs) > 0 {
+		if b, ok := objs[0].(ucl.BytesObject); ok {
+			args.Shift(1)
+			return b, args, nil
+		}
+	}
+
+	var s string
+	if err := args.Bind(&s); err != nil {
+		return nil, ucl.CallArgs{}, err
+	}
+	return ucl.BytesObject(s), args, nil
+}
diff --git a/ucl/builtins/bytes_test.go b/ucl/builtins/bytes_test.go
new file mode 100644
index 0000000..1c5554e
--- /dev/null
+++ b/ucl/builtins/bytes_test.go
@@ -0,0 +1,85 @@
+package builtins_test
+
+import (
+	"context"
+	"encoding/hex"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"ucl.lmika.dev/ucl"
+	"ucl.lmika.dev/ucl/builtins"
+)
+
+func TestBytes_Hash(t *testing.T) {
+	tests := []struct {
+		desc    string
+		eval    string
+		wantHex string
+		wantErr bool
+	}{
+		{desc: "md5 of string", eval: `bytes:hash "hello" md5`, wantHex: "5d41402abc4b2a76b9719d911017c592"},
+		{desc: "sha1 of string", eval: `bytes:hash "hello" sha1`, wantHex: "aaf4c61ddcc5e8a2dabede0f3b482cd9aea9434d"},
+		{desc: "sha256 of string", eval: `bytes:hash "hello" sha256`, wantHex: "2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824"},
+
+		{desc: "md5 of empty string", eval: `bytes:hash "" md5`, wantHex: "d41d8cd98f00b204e9800998ecf8427e"},
+		{desc: "sha256 of empty string", eval: `bytes:hash "" sha256`, wantHex: "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"},
+
+		{desc: "md5 of bytes input", eval: `bytes:hash (bytes:hash "hello" md5) md5`, wantHex: "62109206880d38a4010a98e11243924a"},
+		{desc: "sha1 of bytes input", eval: `bytes:hash (bytes:hash "hello" md5) sha1`, wantHex: "7eb14e07d62722cb2e338faa6060b4f780e80b2a"},
+
+		{desc: "err unsupported algorithm", eval: `bytes:hash "hello" sha512`, wantErr: true},
+		{desc: "err missing algorithm", eval: `bytes:hash "hello"`, wantErr: true},
+		{desc: "err missing args", eval: `bytes:hash`, wantErr: true},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.desc, func(t *testing.T) {
+			inst := ucl.New(
+				ucl.WithModule(builtins.Bytes()),
+			)
+			res, err := inst.EvalString(context.Background(), tt.eval)
+			if tt.wantErr {
+				assert.Error(t, err)
+			} else {
+				assert.NoError(t, err)
+
+				resBts, ok := res.([]byte)
+				if assert.True(t, ok, "expected []byte result, got %T", res) {
+					assert.Equal(t, tt.wantHex, hex.EncodeToString(resBts))
+				}
+			}
+		})
+	}
+}
+
+func TestBytes_Base64(t *testing.T) {
+	tests := []struct {
+		desc    string
+		eval    string
+		want    string
+		wantErr bool
+	}{
+		{desc: "encode string", eval: `bytes:base64 "hello, world"`, want: "aGVsbG8sIHdvcmxk"},
+		{desc: "encode string with padding", eval: `bytes:base64 "hello"`, want: "aGVsbG8="},
+		{desc: "encode empty string", eval: `bytes:base64 ""`, want: ""},
+
+		{desc: "encode bytes input", eval: `bytes:base64 (bytes:hash "hello" md5)`, want: "XUFAKrxLKna5cZ2REBfFkg=="},
+
+		{desc: "err missing args", eval: `bytes:base64`, wantErr: true},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.desc, func(t *testing.T) {
+			inst := ucl.New(
+				ucl.WithModule(builtins.Bytes()),
+			)
+			res, err := inst.EvalString(context.Background(), tt.eval)
+			if tt.wantErr {
+				assert.Error(t, err)
+			} else {
+				assert.NoError(t, err)
+				assert.Equal(t, tt.want, res)
+			}
+		})
+	}
+}
diff --git a/ucl/builtins/os_test.go b/ucl/builtins/os_test.go
index b54b59f..78cee7f 100644
--- a/ucl/builtins/os_test.go
+++ b/ucl/builtins/os_test.go
@@ -46,6 +46,7 @@ func TestOS_Exec(t *testing.T) {
 		{descr: "run command 1", eval: `os:exec "echo" "hello, world"`, want: "hello, world\n"},
 		{descr: "run command 2", eval: `os:exec "date" "+%Y%m%d"`, want: time.Now().Format("20060102") + "\n"},
 		{descr: "run command 3", eval: `os:exec "tr" "[a-z]" "[A-Z]" -in "hello"`, want: "HELLO"},
+		{descr: "run command 4", eval: `os:exec "tr" "-d" "e" -in "hello"`, want: "hllo"},
 	}
 
 	for _, tt := range tests {
diff --git a/ucl/builtins/urls_test.go b/ucl/builtins/urls_test.go
index 47d46a9..c6d9078 100644
--- a/ucl/builtins/urls_test.go
+++ b/ucl/builtins/urls_test.go
@@ -2,6 +2,9 @@ package builtins_test
 
 import (
 	"context"
+	"fmt"
+	"net/http"
+	"net/http/httptest"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -10,19 +13,42 @@ import (
 )
 
 func TestURLs_Fetch_http(t *testing.T) {
+	mux := http.NewServeMux()
+	mux.HandleFunc("/text", func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "text/plain; charset=utf-8")
+		fmt.Fprint(w, "Hello, world")
+	})
+	mux.HandleFunc("/html", func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "text/html; charset=utf-8")
+		fmt.Fprint(w, "<html><body><h1>Example Domain</h1></body></html>")
+	})
+	mux.HandleFunc("/json", func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		fmt.Fprint(w, `{"title":"Example Domain"}`)
+	})
+	mux.HandleFunc("/missing", func(w http.ResponseWriter, r *http.Request) {
+		http.Error(w, "not found", http.StatusNotFound)
+	})
+
+	srv := httptest.NewServer(mux)
+	defer srv.Close()
+
 	tests := []struct {
 		desc    string
 		eval    string
 		want    any
 		wantErr bool
 	}{
-		{desc: "fetch 1", eval: `in (urls:fetch "https://www.example.com") "Example Domain"`, want: true},
+		{desc: "fetch text", eval: fmt.Sprintf(`urls:fetch "%v/text"`, srv.URL), want: "Hello, world"},
+		{desc: "fetch html", eval: fmt.Sprintf(`in (urls:fetch "%v/html") "Example Domain"`, srv.URL), want: true},
+		{desc: "non-200 status code", eval: fmt.Sprintf(`urls:fetch "%v/missing"`, srv.URL), wantErr: true},
+		{desc: "unsupported content type", eval: fmt.Sprintf(`urls:fetch "%v/json"`, srv.URL), wantErr: true},
+		{desc: "unsupported scheme", eval: `urls:fetch "ftp://example.com/file.txt"`, wantErr: true},
 	}
 
 	for _, tt := range tests {
 		t.Run(tt.desc, func(t *testing.T) {
 			inst := ucl.New(
-				ucl.WithModule(builtins.Strs()),
 				ucl.WithModule(builtins.URLs()),
 			)
 			res, err := inst.EvalString(context.Background(), tt.eval)
diff --git a/ucl/objs.go b/ucl/objs.go
index d77f13f..df0872d 100644
--- a/ucl/objs.go
+++ b/ucl/objs.go
@@ -118,6 +118,24 @@ func (ss StringListObject) Index(i int) Object {
 	return StringObject(ss[i])
 }
 
+type BytesObject []byte
+
+func (bs BytesObject) String() string {
+	return fmt.Sprintf("[%v]bytes", len(bs))
+}
+
+func (bs BytesObject) Truthy() bool {
+	return len(bs) > 0
+}
+
+func (bs BytesObject) Len() int {
+	return len(bs)
+}
+
+func (bs BytesObject) Index(i int) Object {
+	return IntObject(bs[i])
+}
+
 type iteratorObject struct {
 	Iterable
 }
@@ -242,6 +260,8 @@ func toGoValue(obj Object) (interface{}, bool) {
 		return bool(v), true
 	case TimeObject:
 		return time.Time(v), true
+	case BytesObject:
+		return []byte(v), true
 	case *ListObject:
 		xs := make([]interface{}, 0, len(*v))
 		for _, va := range *v {
@@ -293,6 +313,8 @@ func fromGoValue(v any) (Object, error) {
 		return IntObject(t), nil
 	case bool:
 		return BoolObject(t), nil
+	case []byte:
+		return BytesObject(t), nil
 	case time.Time:
 		return TimeObject(t), nil
 	}
diff --git a/ucl/objs_test.go b/ucl/objs_test.go
new file mode 100644
index 0000000..e84d772
--- /dev/null
+++ b/ucl/objs_test.go
@@ -0,0 +1,177 @@
+package ucl
+
+import (
+	"bytes"
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestBytesObject_String(t *testing.T) {
+	tests := []struct {
+		desc string
+		obj  BytesObject
+		want string
+	}{
+		{desc: "empty", obj: BytesObject{}, want: "[0]bytes"},
+		{desc: "single byte", obj: BytesObject("a"), want: "[1]bytes"},
+		{desc: "multiple bytes", obj: BytesObject("hello"), want: "[5]bytes"},
+		{desc: "binary bytes", obj: BytesObject{0x00, 0xff, 0x10}, want: "[3]bytes"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.desc, func(t *testing.T) {
+			assert.Equal(t, tt.want, tt.obj.String())
+		})
+	}
+}
+
+func TestBytesObject_Truthy(t *testing.T) {
+	tests := []struct {
+		desc string
+		obj  BytesObject
+		want bool
+	}{
+		{desc: "empty", obj: BytesObject{}, want: false},
+		{desc: "nil", obj: nil, want: false},
+		{desc: "single byte", obj: BytesObject("a"), want: true},
+		{desc: "multiple bytes", obj: BytesObject("hello"), want: true},
+		{desc: "single zero byte", obj: BytesObject{0x00}, want: true},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.desc, func(t *testing.T) {
+			assert.Equal(t, tt.want, tt.obj.Truthy())
+		})
+	}
+}
+
+func TestBytesObject_Len(t *testing.T) {
+	tests := []struct {
+		desc string
+		obj  BytesObject
+		want int
+	}{
+		{desc: "empty", obj: BytesObject{}, want: 0},
+		{desc: "single byte", obj: BytesObject("a"), want: 1},
+		{desc: "multiple bytes", obj: BytesObject("hello"), want: 5},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.desc, func(t *testing.T) {
+			assert.Equal(t, tt.want, tt.obj.Len())
+		})
+	}
+}
+
+func TestBytesObject_Index(t *testing.T) {
+	tests := []struct {
+		desc string
+		obj  BytesObject
+		idx  int
+		want Object
+	}{
+		{desc: "first byte", obj: BytesObject("hello"), idx: 0, want: IntObject(104)},
+		{desc: "last byte", obj: BytesObject("hello"), idx: 4, want: IntObject(111)},
+		{desc: "binary byte", obj: BytesObject{0x00, 0xff}, idx: 1, want: IntObject(255)},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.desc, func(t *testing.T) {
+			assert.Equal(t, tt.want, tt.obj.Index(tt.idx))
+		})
+	}
+}
+
+func TestBytesObject_GoConversion(t *testing.T) {
+	t.Run("from go value", func(t *testing.T) {
+		obj, err := fromGoValue([]byte("hello"))
+		assert.NoError(t, err)
+		assert.Equal(t, BytesObject("hello"), obj)
+	})
+
+	t.Run("to go value", func(t *testing.T) {
+		v, ok := toGoValue(BytesObject("hello"))
+		assert.True(t, ok)
+		assert.Equal(t, []byte("hello"), v)
+	})
+
+	t.Run("round trip through script", func(t *testing.T) {
+		inst := New(WithTestBuiltin())
+		inst.SetVar("b", []byte("hello"))
+
+		res, err := inst.EvalString(context.Background(), `$b`)
+		assert.NoError(t, err)
+		assert.Equal(t, []byte("hello"), res)
+	})
+}
+
+func TestBytesObject_Script(t *testing.T) {
+	tests := []struct {
+		desc string
+		expr string
+		want any
+	}{
+		{desc: "str of bytes", expr: `str $b`, want: "hello"},
+		{desc: "str of empty bytes", expr: `str $e`, want: ""},
+		{desc: "str of binary bytes", expr: `str $bin`, want: "\x00\xff"},
+
+		{desc: "len of bytes", expr: `len $b`, want: 5},
+		{desc: "len of empty bytes", expr: `len $e`, want: 0},
+
+		{desc: "index first byte", expr: `index $b 0`, want: 104},
+		{desc: "index last byte", expr: `index $b 4`, want: 111},
+		{desc: "index out of range", expr: `index $b 555`, want: nil},
+		{desc: "index via pipe", expr: `$b | index 1`, want: 101},
+
+		{desc: "truthy non-empty", expr: `if $b { "yes" } else { "no" }`, want: "yes"},
+		{desc: "truthy empty", expr: `if $e { "yes" } else { "no" }`, want: "no"},
+
+		{desc: "iterate bytes yields ints", expr: `s = "" ; for $b { |x| s = cat $s $x "," } ; $s`, want: "104,101,108,108,111,"},
+		{desc: "iterate empty bytes", expr: `s = "" ; for $e { |x| s = cat $s $x "," } ; $s`, want: ""},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.desc, func(t *testing.T) {
+			ctx := context.Background()
+
+			inst := New(WithTestBuiltin())
+			inst.SetVar("b", []byte("hello"))
+			inst.SetVar("e", []byte{})
+			inst.SetVar("bin", []byte{0x00, 0xff})
+
+			res, err := inst.EvalString(ctx, tt.expr)
+			assert.NoError(t, err)
+			assert.Equal(t, tt.want, res)
+		})
+	}
+}
+
+func TestBytesObject_Display(t *testing.T) {
+	tests := []struct {
+		desc string
+		expr string
+		want string
+	}{
+		{desc: "echo bytes", expr: `echo $b`, want: "[5]bytes\n(nil)\n"},
+		{desc: "echo empty bytes", expr: `echo $e`, want: "[0]bytes\n(nil)\n"},
+		{desc: "display bytes iterates as ints", expr: `$b`, want: "104\n101\n108\n108\n111\n"},
+		{desc: "display empty bytes", expr: `$e`, want: ""},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.desc, func(t *testing.T) {
+			ctx := context.Background()
+			outW := bytes.NewBuffer(nil)
+
+			inst := New(WithOut(outW), WithTestBuiltin())
+			inst.SetVar("b", []byte("hello"))
+			inst.SetVar("e", []byte{})
+
+			err := evalAndDisplay(ctx, inst, tt.expr)
+			assert.NoError(t, err)
+			assert.Equal(t, tt.want, outW.String())
+		})
+	}
+}