diff --git a/.github/workflows/test-registry.yml b/.github/workflows/test-registry.yml
new file mode 100644
index 0000000..9ead23a
--- /dev/null
+++ b/.github/workflows/test-registry.yml
@@ -0,0 +1,13 @@
+on:
+  push:
+    paths:
+      - registry/**
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-go@v4
+        with:
+          go-version: '1.22.1'
+      - run: make test-registry
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index b503198..df5675a 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -6,7 +6,7 @@ jobs:
       - uses: actions/checkout@v4
       - uses: actions/setup-go@v4
         with:
-          go-version: '1.21.0'
+          go-version: '1.22.1'
       - uses: aviate-labs/setup-dfx@v0.3.2
         with:
           dfx-version: 0.18.0
diff --git a/registry/client.go b/registry/client.go
index 281698d..917c7da 100644
--- a/registry/client.go
+++ b/registry/client.go
@@ -16,7 +16,7 @@ type Client struct {
 func New() (*Client, error) {
 	dp, err := NewDataProvider()
 	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("failed to create data provider: %w", err)
 	}
 	return &Client{
 		dp: dp,
@@ -26,15 +26,19 @@ func New() (*Client, error) {
 func (c *Client) GetNNSSubnetID() (*principal.Principal, error) {
 	v, _, err := c.dp.GetValueUpdate([]byte("nns_subnet_id"), nil)
 	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("failed to get NNS subnet ID: %w", err)
 	}
 	var nnsSubnetID v1.SubnetId
 	if err := proto.Unmarshal(v, &nnsSubnetID); err != nil {
-		return nil, err
+		return nil, fmt.Errorf("failed to unmarshal NNS subnet ID: %w", err)
 	}
 	return &principal.Principal{Raw: nnsSubnetID.PrincipalId.Raw}, nil
 }
 
+func (c *Client) GetLatestVersion() (uint64, error) {
+	return c.dp.GetLatestVersion()
+}
+
 func (c *Client) GetNodeListSince(version uint64) (NodeMap, error) {
 	nnsSubnetID, err := c.GetNNSSubnetID()
 	if err != nil {
@@ -56,7 +60,7 @@ func (c *Client) GetNodeListSince(version uint64) (NodeMap, error) {
 	for {
 		records, _, err := c.dp.GetCertifiedChangesSince(currentVersion, nnsPublicKey)
 		if err != nil {
-			return nil, err
+			return nil, fmt.Errorf("failed to get certified changes: %w", err)
 		}
 		currentVersion = records[len(records)-1].Version
 		for _, record := range records {
@@ -66,7 +70,7 @@ func (c *Client) GetNodeListSince(version uint64) (NodeMap, error) {
 				} else {
 					var nodeRecord v1.NodeRecord
 					if err := proto.Unmarshal(record.Value, &nodeRecord); err != nil {
-						return nil, err
+						return nil, fmt.Errorf("failed to unmarshal node record: %w", err)
 					}
 					nodeMap[strings.TrimPrefix(record.Key, "node_record_")] = &nodeRecord
 				}
@@ -76,7 +80,7 @@ func (c *Client) GetNodeListSince(version uint64) (NodeMap, error) {
 				} else {
 					var nodeOperatorRecord v1.NodeOperatorRecord
 					if err := proto.Unmarshal(record.Value, &nodeOperatorRecord); err != nil {
-						return nil, err
+						return nil, fmt.Errorf("failed to unmarshal node operator record: %w", err)
 					}
 					nodeOperatorMap[strings.TrimPrefix(record.Key, "node_operator_record_")] = &nodeOperatorRecord
 				}
@@ -124,11 +128,11 @@ func (c *Client) GetNodeListSince(version uint64) (NodeMap, error) {
 func (c *Client) GetSubnetDetails(subnetID principal.Principal) (*v1.SubnetRecord, error) {
 	v, _, err := c.dp.GetValueUpdate([]byte(fmt.Sprintf("subnet_record_%s", subnetID)), nil)
 	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("failed to get subnet details: %w", err)
 	}
 	var record v1.SubnetRecord
 	if err := proto.Unmarshal(v, &record); err != nil {
-		return nil, err
+		return nil, fmt.Errorf("failed to unmarshal subnet details: %w", err)
 	}
 	return &record, nil
 }
@@ -136,11 +140,11 @@ func (c *Client) GetSubnetDetails(subnetID principal.Principal) (*v1.SubnetRecor
 func (c *Client) GetSubnetIDs() ([]principal.Principal, error) {
 	v, _, err := c.dp.GetValueUpdate([]byte("subnet_list"), nil)
 	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("failed to get subnet IDs: %w", err)
 	}
 	var list v1.SubnetListRecord
 	if err := proto.Unmarshal(v, &list); err != nil {
-		return nil, err
+		return nil, fmt.Errorf("failed to unmarshal subnet IDs: %w", err)
 	}
 	var subnets []principal.Principal
 	for _, subnet := range list.Subnets {
@@ -152,11 +156,11 @@ func (c *Client) GetSubnetIDs() ([]principal.Principal, error) {
 func (c *Client) GetSubnetPublicKey(subnetID principal.Principal) ([]byte, error) {
 	v, _, err := c.dp.GetValueUpdate([]byte(fmt.Sprintf("crypto_threshold_signing_public_key_%s", subnetID)), nil)
 	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("failed to get subnet public key: %w", err)
 	}
 	var publicKey v1.PublicKey
 	if err := proto.Unmarshal(v, &publicKey); err != nil {
-		return nil, err
+		return nil, fmt.Errorf("failed to unmarshal subnet public key: %w", err)
 	}
 	if publicKey.Algorithm != v1.AlgorithmId_ALGORITHM_ID_THRES_BLS12_381 {
 		return nil, fmt.Errorf("unsupported public key algorithm")
diff --git a/registry/client_test.go b/registry/client_test.go
index a7dc6fc..61c0129 100644
--- a/registry/client_test.go
+++ b/registry/client_test.go
@@ -1,17 +1,25 @@
-package registry
+package registry_test
 
 import (
+	"github.com/aviate-labs/agent-go/registry"
 	"os"
 	"testing"
 )
 
 func TestClient_GetNodeListSince(t *testing.T) {
 	checkEnabled(t)
-	c, err := New()
+
+	c, err := registry.New()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	latestVersion, err := c.GetLatestVersion()
 	if err != nil {
 		t.Fatal(err)
 	}
-	if _, err := c.GetNodeListSince(0); err != nil {
+
+	if _, err := c.GetNodeListSince(latestVersion - 100); err != nil {
 		t.Fatal(err)
 	}
 }
diff --git a/registry/dataprovider.go b/registry/dataprovider.go
index d7514ec..42aa870 100644
--- a/registry/dataprovider.go
+++ b/registry/dataprovider.go
@@ -22,7 +22,7 @@ type DataProvider struct {
 func NewDataProvider() (*DataProvider, error) {
 	a, err := agent.New(agent.DefaultConfig)
 	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("failed to create agent: %w", err)
 	}
 	return &DataProvider{a: a}, nil
 }
@@ -37,28 +37,28 @@ func (d DataProvider) GetCertifiedChangesSince(version uint64, publicKey []byte)
 		},
 		&resp,
 	); err != nil {
-		return nil, 0, err
+		return nil, 0, fmt.Errorf("failed to get certified changes: %w", err)
 	}
 	ht, err := NewHashTree(resp.HashTree)
 	if err != nil {
-		return nil, 0, err
+		return nil, 0, fmt.Errorf("failed to create hash tree: %w", err)
 	}
 	rawCurrentVersion, err := ht.Lookup(hashtree.Label("current_version"))
 	if err != nil {
-		return nil, 0, err
+		return nil, 0, fmt.Errorf("failed to lookup current version: %w", err)
 	}
 	currentVersion, err := leb128.DecodeUnsigned(bytes.NewReader(rawCurrentVersion))
 	if err != nil {
-		return nil, 0, err
+		return nil, 0, fmt.Errorf("failed to decode current version: %w", err)
 	}
 
 	deltaNodes, err := ht.LookupSubTree(hashtree.Label("delta"))
 	if err != nil {
-		return nil, 0, err
+		return nil, 0, fmt.Errorf("failed to lookup delta nodes: %w", err)
 	}
 	rawDeltas, err := hashtree.AllChildren(deltaNodes)
 	if err != nil {
-		return nil, 0, err
+		return nil, 0, fmt.Errorf("failed to get all children: %w", err)
 	}
 
 	var deltas []VersionedRecord
@@ -66,7 +66,7 @@ func (d DataProvider) GetCertifiedChangesSince(version uint64, publicKey []byte)
 	for _, delta := range rawDeltas {
 		req := new(v1.RegistryAtomicMutateRequest)
 		if err := proto.Unmarshal(delta.Value, req); err != nil {
-			return nil, 0, err
+			return nil, 0, fmt.Errorf("failed to unmarshal atomic mutate request: %w", err)
 		}
 
 		v := binary.BigEndian.Uint64(delta.Path[0])
@@ -99,7 +99,7 @@ func (d DataProvider) GetCertifiedChangesSince(version uint64, publicKey []byte)
 		publicKey,
 		digest[:],
 	); err != nil {
-		return nil, 0, err
+		return nil, 0, fmt.Errorf("failed to verify certified data: %w", err)
 	}
 
 	return deltas, currentVersion.Uint64(), nil
@@ -116,7 +116,7 @@ func (d DataProvider) GetChangesSince(version uint64) ([]*v1.RegistryDelta, uint
 		},
 		&resp,
 	); err != nil {
-		return nil, 0, err
+		return nil, 0, fmt.Errorf("failed to get changes since: %w", err)
 	}
 	if resp.Error != nil {
 		return nil, 0, fmt.Errorf("error: %s", resp.Error.String())
@@ -132,7 +132,7 @@ func (d DataProvider) GetLatestVersion() (uint64, error) {
 		nil,
 		&resp,
 	); err != nil {
-		return 0, err
+		return 0, fmt.Errorf("failed to get latest version: %w", err)
 	}
 	return resp.Version, nil
 }
@@ -154,7 +154,7 @@ func (d DataProvider) GetValue(key []byte, version *uint64) ([]byte, uint64, err
 		},
 		&resp,
 	); err != nil {
-		return nil, 0, err
+		return nil, 0, fmt.Errorf("failed to get value: %w", err)
 	}
 	if resp.Error != nil {
 		return nil, 0, fmt.Errorf("error: %s", resp.Error.String())
@@ -178,7 +178,7 @@ func (d DataProvider) GetValueUpdate(key []byte, version *uint64) ([]byte, uint6
 		},
 		&resp,
 	); err != nil {
-		return nil, 0, err
+		return nil, 0, fmt.Errorf("failed to get value: %w", err)
 	}
 	if resp.Error != nil {
 		return nil, 0, fmt.Errorf("error: %s", resp.Error.String())
diff --git a/registry/dataprovider_test.go b/registry/dataprovider_test.go
new file mode 100644
index 0000000..98031e5
--- /dev/null
+++ b/registry/dataprovider_test.go
@@ -0,0 +1,18 @@
+package registry_test
+
+import (
+	"github.com/aviate-labs/agent-go/registry"
+	"testing"
+)
+
+func TestDataProvider_GetLatestVersion(t *testing.T) {
+	checkEnabled(t)
+
+	dp, err := registry.NewDataProvider()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err := dp.GetLatestVersion(); err != nil {
+		t.Error(err)
+	}
+}
diff --git a/request.go b/request.go
index fa62027..eb80020 100644
--- a/request.go
+++ b/request.go
@@ -79,7 +79,9 @@ func (r *Request) MarshalCBOR() ([]byte, error) {
 	if len(r.MethodName) != 0 {
 		m["method_name"] = r.MethodName
 	}
-	if len(r.Arguments) != 0 {
+	if r.Arguments != nil {
+		// Some endpoints require the argument to be an empty array, not null.
+		// This is the case with the protobuf endpoints on the registry.
 		m["arg"] = r.Arguments
 	}
 	if len(r.Sender.Raw) != 0 {