diff --git a/examples/gno.land/r/demo/tests/test20/gno.mod b/examples/gno.land/r/demo/tests/test20/gno.mod
new file mode 100644
index 00000000000..5be8c8d409f
--- /dev/null
+++ b/examples/gno.land/r/demo/tests/test20/gno.mod
@@ -0,0 +1,3 @@
+module gno.land/r/demo/tests/test20
+
+require gno.land/p/demo/grc/grc20 v0.0.0-latest
diff --git a/examples/gno.land/r/demo/tests/test20/test20.gno b/examples/gno.land/r/demo/tests/test20/test20.gno
new file mode 100644
index 00000000000..6d1aaf108bf
--- /dev/null
+++ b/examples/gno.land/r/demo/tests/test20/test20.gno
@@ -0,0 +1,18 @@
+// Package test20 implements a deliberately insecure ERC20 token for testing purposes.
+// The Test20 token allows anyone to mint any amount of tokens to any address, making
+// it unsuitable for production use. The primary goal of this package is to facilitate
+// testing and experimentation without any security measures or restrictions.
+//
+//	WARNING: This token is highly insecure and should not be used in any
+//	 production environment. It is intended solely for testing and
+//	 educational purposes.
+package test20
+
+import "gno.land/p/demo/grc/grc20"
+
+var (
+	Banker = grc20.NewBanker("Test20", "TST", 4)
+	Token  = Banker.Token()
+)
+
+// XXX func init() { grc20reg.Register(Pub, "") } // Depends on #2516
diff --git a/examples/gno.land/r/demo/vault/gno.mod b/examples/gno.land/r/demo/vault/gno.mod
new file mode 100644
index 00000000000..a6a5907e35f
--- /dev/null
+++ b/examples/gno.land/r/demo/vault/gno.mod
@@ -0,0 +1,6 @@
+module gno.land/r/demo/vault
+
+require (
+	gno.land/p/demo/avl v0.0.0-latest
+	gno.land/p/demo/grc/grc20 v0.0.0-latest
+)
diff --git a/examples/gno.land/r/demo/vault/types.gno b/examples/gno.land/r/demo/vault/types.gno
new file mode 100644
index 00000000000..82cc35e1f58
--- /dev/null
+++ b/examples/gno.land/r/demo/vault/types.gno
@@ -0,0 +1,8 @@
+package vault
+
+import "errors"
+
+var (
+	ErrTooEarlyToRedeem = errors.New("too early to redeem")
+	ErrNoSuchVault      = errors.New("no such vault")
+)
diff --git a/examples/gno.land/r/demo/vault/vault.gno b/examples/gno.land/r/demo/vault/vault.gno
new file mode 100644
index 00000000000..ea24a12a393
--- /dev/null
+++ b/examples/gno.land/r/demo/vault/vault.gno
@@ -0,0 +1,121 @@
+package vault
+
+import (
+	"std"
+
+	"gno.land/p/demo/avl"
+	"gno.land/p/demo/grc/grc20"
+)
+
+type Vault interface {
+	Deposit(amount uint, recovery std.Address, lockDuration uint) error
+	Unvault(amount uint) error
+	Recover(dest std.Address) error
+	Redeem() error
+}
+
+func New(adminToken *grc20.Banker) Vault {
+	return &impl{
+		adminToken: adminToken,
+		users:      avl.Tree{},
+	}
+}
+
+type impl struct {
+	adminToken *grc20.Banker
+	users      avl.Tree // std.Address -> userVault
+}
+
+type userVault struct {
+	// constructor parameters.
+	recover      std.Address
+	lockDuration uint
+
+	// internal parameters.
+	owner           std.Address
+	redeemMinHeight int64
+	unvaultedAmount uint
+}
+
+func (v *impl) Deposit(amount uint, recover std.Address, lockDuration uint) error {
+	caller := std.GetOrigCaller()
+	pkgAddr := std.GetOrigPkgAddr()
+
+	uv := userVault{
+		lockDuration:    lockDuration,
+		redeemMinHeight: 0, // will be set in Unvault.
+		unvaultedAmount: 0, // will be increased in Unvault, zeroed in Redeem.
+		owner:           caller,
+	}
+
+	// deposit.
+	err := v.adminToken.Transfer(caller, pkgAddr, uint64(amount))
+	if err != nil {
+		return err
+	}
+	v.users.Set(caller.String(), &uv)
+
+	return nil
+}
+
+func (v *impl) Unvault(amount uint) error {
+	caller := std.GetOrigCaller()
+	uv, err := v.getUserVault(caller)
+	if err != nil {
+		return err
+	}
+
+	balance := v.adminToken.BalanceOf(caller)
+	if balance < uint64(amount) {
+		return grc20.ErrInsufficientBalance
+	}
+
+	println("AAA1", std.GetHeight(), uv.redeemMinHeight, uv.lockDuration)
+	uv.redeemMinHeight = std.GetHeight() + int64(uv.lockDuration)
+	uv.unvaultedAmount += amount
+	v.users.Set(caller.String(), uv)
+	println("AAA2", std.GetHeight(), uv.redeemMinHeight, uv.lockDuration)
+	return nil
+}
+
+func (v *impl) Redeem() error {
+	pkgAddr := std.GetOrigPkgAddr()
+	caller := std.GetOrigCaller()
+	uv, err := v.getUserVault(caller)
+	if err != nil {
+		return err
+	}
+
+	println("AAA3", std.GetHeight(), uv.redeemMinHeight, uv.lockDuration)
+	if std.GetHeight() < uv.redeemMinHeight {
+		return ErrTooEarlyToRedeem
+	}
+	// TODO: check balance. (should be optional, but let's be sure).
+	// TODO: check height.
+
+	// transfer token.
+	err = v.adminToken.Transfer(pkgAddr, caller, uint64(uv.unvaultedAmount))
+	if err != nil {
+		return err
+	}
+
+	uv.unvaultedAmount = 0
+	// TODO: if balance == 0 -> destroy?
+	return nil
+}
+
+func (v *impl) Recover(dest std.Address) error {
+	// TODO: assert caller (recovery).
+	// TODO: trasfertToken.
+	// TODO: destroy?
+	return nil
+}
+
+func (v *impl) getUserVault(address std.Address) (*userVault, error) {
+	uvI, exists := v.users.Get(address.String())
+	if !exists {
+		return nil, ErrNoSuchVault
+	}
+	uv := uvI.(*userVault)
+	return uv, nil
+}
diff --git a/examples/gno.land/r/demo/vault/vault_test.gno b/examples/gno.land/r/demo/vault/vault_test.gno
new file mode 100644
index 00000000000..c0dc6499300
--- /dev/null
+++ b/examples/gno.land/r/demo/vault/vault_test.gno
@@ -0,0 +1,3 @@
+package vault
+
+// TODO: unit tests, edge cases.
diff --git a/examples/gno.land/r/demo/vault/z1_filetest.gno b/examples/gno.land/r/demo/vault/z1_filetest.gno
new file mode 100644
index 00000000000..4f2c3b1e597
--- /dev/null
+++ b/examples/gno.land/r/demo/vault/z1_filetest.gno
@@ -0,0 +1,78 @@
+package main
+
+import (
+	"std"
+
+	"gno.land/p/demo/testutils"
+	"gno.land/p/demo/ufmt"
+	"gno.land/r/demo/tests/test20"
+	"gno.land/r/demo/vault"
+)
+
+func main() {
+	var (
+		alice    = testutils.TestAddress("alice")
+		bob      = testutils.TestAddress("bob")    // recovery request address (cold wallet).
+		charly   = testutils.TestAddress("charly") // recovery dest.
+		pkgaddr  = std.GetOrigPkgAddr()
+		t20token = test20.Token
+	)
+
+	printBalances := func() {
+		aliceBalance := t20token.BalanceOf(alice)
+		bobBalance := t20token.BalanceOf(bob)
+		charlyBalance := t20token.BalanceOf(charly)
+		pkgBalance := t20token.BalanceOf(pkgaddr)
+		height := std.GetHeight()
+		println(ufmt.Sprintf(
+			"balances: alice=%d, bob=%d, charly=%d, pkg=%d, height=%d",
+			aliceBalance, bobBalance, charlyBalance, pkgBalance, height))
+	}
+
+	// create a vault for t20token.
+	v := vault.New(t20token)
+	printBalances()
+
+	return // XXX
+
+	// alice deposits 300 with an unlock duration of 5 blocks.
+	std.TestSetOrigCaller(alice)
+	lockAmount := uint(300)
+	lockDuration := uint(5)
+	checkErr(v.Deposit(lockAmount, bob, lockDuration))
+	printBalances()
+
+	// alice calls unvault for 200 t20tokens.
+	checkErr(v.Unvault(200))
+	printBalances()
+
+	// alice waits for few blocks.
+	std.TestSkipHeights(int64(lockDuration) + 1)
+	printBalances()
+
+	// alice redeems 200 t20tokens.
+	checkErr(v.Redeem())
+	printBalances()
+
+	// bob instantly recover everything in the wallet.
+	std.TestSetOrigCaller(bob)
+	checkErr(v.Recover(charly))
+	printBalances()
+}
+
+func checkErr(err error) {
+	if err != nil {
+		panic(err)
+	}
+}
+
+// Output:
+// balances: alice=1000, bob=0, charly=0, pkg=0, height=123
+// balances: alice=700, bob=0, charly=0, pkg=300, height=123
+// AAA1 123 0 5
+// AAA2 123 128 5
+// balances: alice=700, bob=0, charly=0, pkg=300, height=123
+// balances: alice=700, bob=0, charly=0, pkg=300, height=129
+// AAA3 129 128 5
+// balances: alice=900, bob=0, charly=0, pkg=100, height=129
+// balances: alice=900, bob=0, charly=0, pkg=100, height=129