diff --git a/golang/cosmos/x/vtransfer/types/baseaddr.go b/golang/cosmos/types/address_hooks.go
similarity index 60%
rename from golang/cosmos/x/vtransfer/types/baseaddr.go
rename to golang/cosmos/types/address_hooks.go
index 7ad65541746..4c4fcfd0803 100644
--- a/golang/cosmos/x/vtransfer/types/baseaddr.go
+++ b/golang/cosmos/types/address_hooks.go
@@ -1,11 +1,11 @@
 package types
 
 import (
+	"bytes"
 	"fmt"
-	"net/url"
-	"strings"
 
 	"github.com/cosmos/cosmos-sdk/codec"
+	"github.com/cosmos/cosmos-sdk/types/bech32"
 
 	transfertypes "github.com/cosmos/ibc-go/v6/modules/apps/transfer/types"
 	clienttypes "github.com/cosmos/ibc-go/v6/modules/core/02-client/types"
@@ -18,48 +18,90 @@ type AddressRole string
 const (
 	RoleSender   AddressRole = "Sender"
 	RoleReceiver AddressRole = "Receiver"
+
+	AddressHookVersion     = 0
+	BaseAddressLengthBytes = 2
 )
 
-func trimSlashPrefix(s string) string {
-	return strings.TrimPrefix(s, "/")
+// AddressHookMagic is a magic byte prefix that identifies a hooked address.
+// Chosen to make bech32 address hooks that look like "agoric10rch..."
+var AddressHookMagic = []byte{0x78, 0xf1, 0x70 | AddressHookVersion}
+
+func init() {
+	if AddressHookVersion&0x0f != AddressHookVersion {
+		panic(fmt.Sprintf("AddressHookVersion must be less than 0x10, got 0x%x", AddressHookVersion))
+	}
 }
 
 // ExtractBaseAddress extracts the base address from a parameterized address.
 // It removes all subpath and query components from addr.
 func ExtractBaseAddress(addr string) (string, error) {
-	parsed, err := url.Parse(addr)
+	baseAddr, _, err := SplitHookedAddress(addr)
 	if err != nil {
 		return "", err
 	}
+	return baseAddr, nil
+}
 
-	// Specify the fields and values we expect.  Unspecified fields will only
-	// match if they are zero values in order to be robust against extensions to
-	// the url.URL struct.
-	//
-	// Remove leading slashes from the path fields so that only parsed relative
-	// paths match the expected test.
-	expected := url.URL{
-		Path:        trimSlashPrefix(parsed.Path),
-		RawPath:     trimSlashPrefix(parsed.RawPath),
-		RawQuery:    parsed.RawQuery,
-		Fragment:    parsed.Fragment,
-		RawFragment: parsed.RawFragment,
+// SplitHookedAddress splits a hooked address into its base address and hook data.
+// For the JS implementation, look at @agoric/cosmic-proto/src/address-hooks.js.
+func SplitHookedAddress(addr string) (string, []byte, error) {
+	prefix, payload, err := bech32.DecodeAndConvert(addr)
+	if err != nil {
+		return "", []byte{}, err
+	}
 
-		// Skip over parsing control flags.
-		ForceQuery: parsed.ForceQuery,
-		OmitHost:   parsed.OmitHost,
+	bz := bytes.TrimPrefix(payload, AddressHookMagic)
+	if len(bz) == len(payload) {
+		// Return an unhooked address.
+		return addr, []byte{}, nil
 	}
 
-	if *parsed != expected {
-		return "", fmt.Errorf("address must be relative path with optional query and fragment, got %s", addr)
+	if len(bz) < BaseAddressLengthBytes {
+		return "", []byte{}, fmt.Errorf("hooked address must have at least %d bytes", BaseAddressLengthBytes)
 	}
 
-	baseAddr, _, _ := strings.Cut(expected.Path, "/")
-	if baseAddr == "" {
-		return "", fmt.Errorf("base address cannot be empty")
+	b := 0
+	for i := BaseAddressLengthBytes - 1; i >= 0; i -= 1 {
+		by := bz[len(bz)-1-i]
+		b <<= 8
+		b |= int(by)
 	}
 
-	return baseAddr, nil
+	if b > len(bz)-BaseAddressLengthBytes {
+		return "", []byte{}, fmt.Errorf("base address length 0x%x is longer than specimen length 0x%x", b, len(bz)-BaseAddressLengthBytes)
+	}
+
+	baseAddressBuf := bz[0:b]
+	baseAddress, err := bech32.ConvertAndEncode(prefix, baseAddressBuf)
+	if err != nil {
+		return "", []byte{}, err
+	}
+
+	return baseAddress, bz[b:], nil
+}
+
+// JoinHookedAddress joins a base bech32 address with hook data to create a
+// hooked bech32 address.
+// For the JS implementation, look at @agoric/cosmic-proto/src/address-hooks.js
+func JoinHookedAddress(baseAddr string, hookData []byte) (string, error) {
+	prefix, bz, err := bech32.DecodeAndConvert(baseAddr)
+	if err != nil {
+		return "", err
+	}
+
+	b := len(bz)
+	if b > 0xffff {
+		return "", fmt.Errorf("base address length 0x%x is longer than the maximum 0x%x", b, 1<<(8*BaseAddressLengthBytes-1)+1)
+	}
+
+	payload := make([]byte, 0, len(AddressHookMagic)+b+len(hookData)+BaseAddressLengthBytes)
+	payload = append(payload, AddressHookMagic...)
+	payload = append(payload, bz...)
+	payload = append(payload, hookData...)
+	payload = append(payload, byte(b>>8), byte(b))
+
+	return bech32.ConvertAndEncode(prefix, payload)
 }
 
 // extractBaseTransferData returns the base address from the transferData.Sender
diff --git a/golang/cosmos/x/vtransfer/types/baseaddr_test.go b/golang/cosmos/types/address_hooks_test.go
similarity index 65%
rename from golang/cosmos/x/vtransfer/types/baseaddr_test.go
rename to golang/cosmos/types/address_hooks_test.go
index eb83f07ddb6..e20e1540811 100644
--- a/golang/cosmos/x/vtransfer/types/baseaddr_test.go
+++ b/golang/cosmos/types/address_hooks_test.go
@@ -12,7 +12,7 @@ import (
 	clienttypes "github.com/cosmos/ibc-go/v6/modules/core/02-client/types"
 	channeltypes "github.com/cosmos/ibc-go/v6/modules/core/04-channel/types"
 
-	"github.com/Agoric/agoric-sdk/golang/cosmos/x/vtransfer/types"
+	"github.com/Agoric/agoric-sdk/golang/cosmos/types"
 )
 
 func TestExtractBaseAddress(t *testing.T) {
@@ -20,28 +20,12 @@ func TestExtractBaseAddress(t *testing.T) {
 		name string
 		addr string
 	}{
-		{"agoric address", "agoric1abcdefghiteaneas"},
-		{"cosmos address", "cosmos1abcdeffiharceuht"},
-		{"hex address", "0xabcdef198189818c93839ibia"},
-	}
-
-	prefixes := []struct {
-		prefix      string
-		baseIsWrong bool
-		isErr       bool
-	}{
-		{"", false, false},
-		{"/", false, true},
-		{"orch:/", false, true},
-		{"unexpected", true, false},
-		{"norch:/", false, true},
-		{"orch:", false, true},
-		{"norch:", false, true},
-		{"\x01", false, true},
+		{"agoric address", "agoric1qqp0e5ys"},
+		{"cosmos address", "cosmos1qqxuevtt"},
 	}
 
 	suffixes := []struct {
-		suffix      string
+		hookStr     string
 		baseIsWrong bool
 		isErr       bool
 	}{
@@ -50,31 +34,29 @@ func TestExtractBaseAddress(t *testing.T) {
 		{"/sub/account", false, false},
 		{"?query=something&k=v&k2=v2", false, false},
 		{"?query=something&k=v&k2=v2#fragment", false, false},
-		{"unexpected", true, false},
-		{"\x01", false, true},
+		{"unexpected", false, false},
+		{"\x01", false, false},
 	}
 
 	for _, b := range bases {
 		b := b
-		for _, p := range prefixes {
-			p := p
-			for _, s := range suffixes {
-				s := s
-				t.Run(b.name+" "+p.prefix+" "+s.suffix, func(t *testing.T) {
-					addr := p.prefix + b.addr + s.suffix
-					addr, err := types.ExtractBaseAddress(addr)
-					if p.isErr || s.isErr {
-						require.Error(t, err)
+		for _, s := range suffixes {
+			s := s
+			t.Run(b.name+" "+s.hookStr, func(t *testing.T) {
+				addrHook, err := types.JoinHookedAddress(b.addr, []byte(s.hookStr))
+				require.NoError(t, err)
+				addr, err := types.ExtractBaseAddress(addrHook)
+				if s.isErr {
+					require.Error(t, err)
+				} else {
+					require.NoError(t, err)
+					if s.baseIsWrong {
+						require.NotEqual(t, b.addr, addr)
 					} else {
-						require.NoError(t, err)
-						if p.baseIsWrong || s.baseIsWrong {
-							require.NotEqual(t, b.addr, addr)
-						} else {
-							require.Equal(t, b.addr, addr)
-						}
+						require.Equal(t, b.addr, addr)
 					}
-				})
-			}
+				}
+			})
 		}
 	}
 }
@@ -86,32 +68,37 @@ func TestExtractBaseAddressFromPacket(t *testing.T) {
 	channeltypes.RegisterInterfaces(ir)
 	clienttypes.RegisterInterfaces(ir)
 
+	cosmosHook, err := types.JoinHookedAddress("cosmos1qqxuevtt", []byte("?foo=bar&baz=bot#fragment"))
+	require.NoError(t, err)
+	agoricHook, err := types.JoinHookedAddress("agoric1qqp0e5ys", []byte("?bingo=again"))
+	require.NoError(t, err)
+
 	cases := []struct {
 		name  string
 		addrs map[types.AddressRole]struct{ addr, baseAddr string }
 	}{
 		{"sender has params",
 			map[types.AddressRole]struct{ addr, baseAddr string }{
-				types.RoleSender:   {"cosmos1abcdeffiharceuht?foo=bar&baz=bot#fragment", "cosmos1abcdeffiharceuht"},
-				types.RoleReceiver: {"agoric1abcdefghiteaneas", "agoric1abcdefghiteaneas"},
+				types.RoleSender:   {cosmosHook, "cosmos1qqxuevtt"},
+				types.RoleReceiver: {"agoric1qqp0e5ys", "agoric1qqp0e5ys"},
 			},
 		},
 		{"receiver has params",
 			map[types.AddressRole]struct{ addr, baseAddr string }{
-				types.RoleSender:   {"cosmos1abcdeffiharceuht", "cosmos1abcdeffiharceuht"},
-				types.RoleReceiver: {"agoric1abcdefghiteaneas?bingo=again", "agoric1abcdefghiteaneas"},
+				types.RoleSender:   {"cosmos1qqxuevtt", "cosmos1qqxuevtt"},
+				types.RoleReceiver: {agoricHook, "agoric1qqp0e5ys"},
 			},
 		},
 		{"both are base",
 			map[types.AddressRole]struct{ addr, baseAddr string }{
-				types.RoleSender:   {"cosmos1abcdeffiharceuht", "cosmos1abcdeffiharceuht"},
-				types.RoleReceiver: {"agoric1abcdefghiteaneas", "agoric1abcdefghiteaneas"},
+				types.RoleSender:   {"cosmos1qqxuevtt", "cosmos1qqxuevtt"},
+				types.RoleReceiver: {"agoric1qqp0e5ys", "agoric1qqp0e5ys"},
 			},
 		},
 		{"both have params",
 			map[types.AddressRole]struct{ addr, baseAddr string }{
-				types.RoleSender:   {"agoric1abcdefghiteaneas?bingo=again", "agoric1abcdefghiteaneas"},
-				types.RoleReceiver: {"cosmos1abcdeffiharceuht?foo=bar&baz=bot#fragment", "cosmos1abcdeffiharceuht"},
+				types.RoleSender:   {agoricHook, "agoric1qqp0e5ys"},
+				types.RoleReceiver: {cosmosHook, "cosmos1qqxuevtt"},
 			},
 		},
 	}
diff --git a/golang/cosmos/x/vtransfer/ibc_middleware_test.go b/golang/cosmos/x/vtransfer/ibc_middleware_test.go
index 23279bf8a63..ee9c80ebb56 100644
--- a/golang/cosmos/x/vtransfer/ibc_middleware_test.go
+++ b/golang/cosmos/x/vtransfer/ibc_middleware_test.go
@@ -16,6 +16,7 @@ import (
 	"github.com/tendermint/tendermint/libs/log"
 	dbm "github.com/tendermint/tm-db"
 
+	"github.com/Agoric/agoric-sdk/golang/cosmos/types"
 	swingsettesting "github.com/Agoric/agoric-sdk/golang/cosmos/x/swingset/testing"
 	swingsettypes "github.com/Agoric/agoric-sdk/golang/cosmos/x/swingset/types"
 	vibckeeper "github.com/Agoric/agoric-sdk/golang/cosmos/x/vibc/keeper"
@@ -332,11 +333,13 @@ func (s *IntegrationTestSuite) TestTransferFromAgdToAgd() {
 	s.Run("TransferFromAgdToAgd", func() {
 		// create a transfer packet's data contents
 		baseReceiver := s.chainB.SenderAccounts[1].SenderAccount.GetAddress().String()
+		receiverHook, err := types.JoinHookedAddress(baseReceiver, []byte("?what=arbitrary-data&why=to-test-bridge-targets"))
+		s.Require().NoError(err)
 		transferData := ibctransfertypes.NewFungibleTokenPacketData(
 			"uosmo",
 			"1000000",
 			s.chainA.SenderAccount.GetAddress().String(),
-			baseReceiver+"?what=arbitrary-data&why=to-test-bridge-targets",
+			receiverHook,
 			`"This is a JSON memo"`,
 		)
 
diff --git a/golang/cosmos/x/vtransfer/keeper/keeper.go b/golang/cosmos/x/vtransfer/keeper/keeper.go
index 0d99840c061..ed5b0f57cba 100644
--- a/golang/cosmos/x/vtransfer/keeper/keeper.go
+++ b/golang/cosmos/x/vtransfer/keeper/keeper.go
@@ -13,10 +13,11 @@ import (
 	capabilitykeeper "github.com/cosmos/cosmos-sdk/x/capability/keeper"
 	capabilitytypes "github.com/cosmos/cosmos-sdk/x/capability/types"
 
+	"github.com/Agoric/agoric-sdk/golang/cosmos/types"
 	"github.com/Agoric/agoric-sdk/golang/cosmos/vm"
 	"github.com/Agoric/agoric-sdk/golang/cosmos/x/vibc"
 	vibctypes "github.com/Agoric/agoric-sdk/golang/cosmos/x/vibc/types"
-	"github.com/Agoric/agoric-sdk/golang/cosmos/x/vtransfer/types"
+
 	channeltypes "github.com/cosmos/ibc-go/v6/modules/core/04-channel/types"
 	porttypes "github.com/cosmos/ibc-go/v6/modules/core/05-port/types"
 	host "github.com/cosmos/ibc-go/v6/modules/core/24-host"