diff --git a/cmd/kat-agent/main.go b/cmd/kat-agent/main.go
index d227d53..c94acbc 100644
--- a/cmd/kat-agent/main.go
+++ b/cmd/kat-agent/main.go
@@ -248,124 +248,9 @@ func runInit(cmd *cobra.Command, args []string) {
 				log.Printf("Failed to create API server: %v", err)
 			} else {
 				// Register the join handler
-				apiServer.RegisterJoinHandler(func(w http.ResponseWriter, r *http.Request) {
-					log.Printf("Received join request from %s", r.RemoteAddr)
-					
-					// In Phase 2, we're not requiring client certificates yet
-					log.Printf("Processing join request without client certificate verification (Phase 2)")
-					
-					// Read request body
-					var joinReq cli.JoinRequest
-					if err := json.NewDecoder(r.Body).Decode(&joinReq); err != nil {
-						log.Printf("Error decoding join request: %v", err)
-						http.Error(w, "Invalid request format", http.StatusBadRequest)
-						return
-					}
-					
-					// Validate request
-					if joinReq.NodeName == "" || joinReq.AdvertiseAddr == "" || joinReq.CSRData == "" {
-						log.Printf("Invalid join request: missing required fields")
-						http.Error(w, "Missing required fields", http.StatusBadRequest)
-						return
-					}
-					
-					log.Printf("Processing join request for node: %s, advertise address: %s", 
-						joinReq.NodeName, joinReq.AdvertiseAddr)
-					
-					// Decode CSR data
-					csrData, err := base64.StdEncoding.DecodeString(joinReq.CSRData)
-					if err != nil {
-						log.Printf("Error decoding CSR data: %v", err)
-						http.Error(w, "Invalid CSR data", http.StatusBadRequest)
-						return
-					}
-					
-					// Create a temporary file for the CSR
-					tempCSRFile, err := os.CreateTemp("", "node-csr-*.pem")
-					if err != nil {
-						log.Printf("Error creating temp CSR file: %v", err)
-						http.Error(w, "Internal server error", http.StatusInternalServerError)
-						return
-					}
-					defer os.Remove(tempCSRFile.Name())
-					
-					// Write CSR data to temp file
-					if _, err := tempCSRFile.Write(csrData); err != nil {
-						log.Printf("Error writing CSR data to temp file: %v", err)
-						http.Error(w, "Internal server error", http.StatusInternalServerError)
-						return
-					}
-					tempCSRFile.Close()
-					
-					// Create a temp file for the signed certificate
-					tempCertFile, err := os.CreateTemp("", "node-cert-*.pem")
-					if err != nil {
-						log.Printf("Error creating temp cert file: %v", err)
-						http.Error(w, "Internal server error", http.StatusInternalServerError)
-						return
-					}
-					defer os.Remove(tempCertFile.Name())
-					tempCertFile.Close()
-					
-					// Sign the CSR
-					if err := pki.SignCertificateRequest(
-						filepath.Join(pkiDir, "ca.key"),
-						filepath.Join(pkiDir, "ca.crt"),
-						tempCSRFile.Name(),
-						tempCertFile.Name(),
-						365*24*time.Hour, // 1 year validity
-					); err != nil {
-						log.Printf("Error signing CSR: %v", err)
-						http.Error(w, "Failed to sign certificate", http.StatusInternalServerError)
-						return
-					}
-					
-					// Read the signed certificate
-					signedCert, err := os.ReadFile(tempCertFile.Name())
-					if err != nil {
-						log.Printf("Error reading signed certificate: %v", err)
-						http.Error(w, "Internal server error", http.StatusInternalServerError)
-						return
-					}
-					
-					// Read the CA certificate
-					caCert, err := os.ReadFile(filepath.Join(pkiDir, "ca.crt"))
-					if err != nil {
-						log.Printf("Error reading CA certificate: %v", err)
-						http.Error(w, "Internal server error", http.StatusInternalServerError)
-						return
-					}
-					
-					// Generate a unique node UID
-					nodeUID := uuid.New().String()
-					
-					// Store node registration in etcd (placeholder for now)
-					// In a future phase, we'll implement proper node registration with subnet assignment
-					
-					// Create response
-					joinResp := cli.JoinResponse{
-						NodeName:          joinReq.NodeName,
-						NodeUID:           nodeUID,
-						SignedCertificate: base64.StdEncoding.EncodeToString(signedCert),
-						CACertificate:     base64.StdEncoding.EncodeToString(caCert),
-						AssignedSubnet:    "10.100.0.0/24", // Placeholder, will be properly implemented in network phase
-					}
-					
-					// If etcd peer was requested, add join instructions (placeholder)
-					if etcdPeer {
-						joinResp.EtcdJoinInstructions = "Etcd peer join not implemented in this phase"
-					}
-					
-					// Send response
-					w.Header().Set("Content-Type", "application/json")
-					if err := json.NewEncoder(w).Encode(joinResp); err != nil {
-						log.Printf("Error encoding join response: %v", err)
-						http.Error(w, "Internal server error", http.StatusInternalServerError)
-						return
-					}
-					
-					log.Printf("Successfully processed join request for node: %s", joinReq.NodeName)
-				})
+				joinHandler := api.NewJoinHandler(etcdStore, caKeyPath, caCertPath)
+				apiServer.RegisterJoinHandler(joinHandler)
+				log.Printf("Registered join handler with CA key: %s, CA cert: %s", caKeyPath, caCertPath)
 
 				// Start the server in a goroutine
 				go func() {
diff --git a/internal/api/join_handler.go b/internal/api/join_handler.go
index 30808f2..804331e 100644
--- a/internal/api/join_handler.go
+++ b/internal/api/join_handler.go
@@ -1,9 +1,11 @@
 package api
 
 import (
+	"encoding/base64"
 	"encoding/json"
 	"fmt"
 	"io"
+	"log"
 	"net/http"
 	"os"
 	"path/filepath"
@@ -17,27 +19,31 @@ import (
 
 // JoinRequest represents the data sent by an agent when joining
 type JoinRequest struct {
-	CSR             []byte `json:"csr"`
+	CSRData         string `json:"csrData"`         // base64 encoded CSR
 	AdvertiseAddr   string `json:"advertiseAddr"`
 	NodeName        string `json:"nodeName,omitempty"` // Optional, leader can generate
-	WireguardPubKey string `json:"wireguardPubKey"`    // Placeholder for now
+	WireGuardPubKey string `json:"wireguardPubKey"`    // Placeholder for now
 }
 
 // JoinResponse represents the data sent back to the agent
 type JoinResponse struct {
-	NodeName      string `json:"nodeName"`
-	NodeUID       string `json:"nodeUID"`
-	SignedCert    []byte `json:"signedCert"`
-	CACert        []byte `json:"caCert"`
-	JoinTimestamp int64  `json:"joinTimestamp"`
+	NodeName          string `json:"nodeName"`
+	NodeUID           string `json:"nodeUID"`
+	SignedCertificate string `json:"signedCertificate"` // base64 encoded certificate
+	CACertificate     string `json:"caCertificate"`     // base64 encoded CA certificate
+	AssignedSubnet    string `json:"assignedSubnet"`    // Placeholder for now
+	EtcdJoinInstructions string `json:"etcdJoinInstructions,omitempty"`
 }
 
 // NewJoinHandler creates a handler for agent join requests
 func NewJoinHandler(stateStore store.StateStore, caKeyPath, caCertPath string) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
+		log.Printf("Received join request from %s", r.RemoteAddr)
+		
 		// Read and parse the request body
 		body, err := io.ReadAll(r.Body)
 		if err != nil {
+			log.Printf("Failed to read request body: %v", err)
 			http.Error(w, fmt.Sprintf("Failed to read request body: %v", err), http.StatusBadRequest)
 			return
 		}
@@ -45,16 +51,19 @@ func NewJoinHandler(stateStore store.StateStore, caKeyPath, caCertPath string) h
 
 		var joinReq JoinRequest
 		if err := json.Unmarshal(body, &joinReq); err != nil {
+			log.Printf("Failed to parse request: %v", err)
 			http.Error(w, fmt.Sprintf("Failed to parse request: %v", err), http.StatusBadRequest)
 			return
 		}
 
 		// Validate request
-		if len(joinReq.CSR) == 0 {
-			http.Error(w, "Missing CSR", http.StatusBadRequest)
+		if joinReq.CSRData == "" {
+			log.Printf("Missing CSR data")
+			http.Error(w, "Missing CSR data", http.StatusBadRequest)
 			return
 		}
 		if joinReq.AdvertiseAddr == "" {
+			log.Printf("Missing advertise address")
 			http.Error(w, "Missing advertise address", http.StatusBadRequest)
 			return
 		}
@@ -63,16 +72,26 @@ func NewJoinHandler(stateStore store.StateStore, caKeyPath, caCertPath string) h
 		nodeName := joinReq.NodeName
 		if nodeName == "" {
 			nodeName = fmt.Sprintf("node-%s", uuid.New().String()[:8])
+			log.Printf("Generated node name: %s", nodeName)
 		}
 
 		// Generate a unique node ID
 		nodeUID := uuid.New().String()
+		log.Printf("Generated node UID: %s", nodeUID)
+
+		// Decode CSR data
+		csrData, err := base64.StdEncoding.DecodeString(joinReq.CSRData)
+		if err != nil {
+			log.Printf("Failed to decode CSR data: %v", err)
+			http.Error(w, fmt.Sprintf("Failed to decode CSR data: %v", err), http.StatusBadRequest)
+			return
+		}
 
-		// Sign the CSR
 		// Create a temporary file for the CSR
 		tempDir := os.TempDir()
 		csrPath := filepath.Join(tempDir, fmt.Sprintf("%s.csr", nodeUID))
-		if err := os.WriteFile(csrPath, joinReq.CSR, 0600); err != nil {
+		if err := os.WriteFile(csrPath, csrData, 0600); err != nil {
+			log.Printf("Failed to save CSR: %v", err)
 			http.Error(w, fmt.Sprintf("Failed to save CSR: %v", err), http.StatusInternalServerError)
 			return
 		}
@@ -81,6 +100,7 @@ func NewJoinHandler(stateStore store.StateStore, caKeyPath, caCertPath string) h
 		// Sign the CSR
 		certPath := filepath.Join(tempDir, fmt.Sprintf("%s.crt", nodeUID))
 		if err := pki.SignCertificateRequest(caKeyPath, caCertPath, csrPath, certPath, 365*24*time.Hour); err != nil {
+			log.Printf("Failed to sign CSR: %v", err)
 			http.Error(w, fmt.Sprintf("Failed to sign CSR: %v", err), http.StatusInternalServerError)
 			return
 		}
@@ -89,6 +109,7 @@ func NewJoinHandler(stateStore store.StateStore, caKeyPath, caCertPath string) h
 		// Read the signed certificate
 		signedCert, err := os.ReadFile(certPath)
 		if err != nil {
+			log.Printf("Failed to read signed certificate: %v", err)
 			http.Error(w, fmt.Sprintf("Failed to read signed certificate: %v", err), http.StatusInternalServerError)
 			return
 		}
@@ -96,6 +117,7 @@ func NewJoinHandler(stateStore store.StateStore, caKeyPath, caCertPath string) h
 		// Read the CA certificate
 		caCert, err := os.ReadFile(caCertPath)
 		if err != nil {
+			log.Printf("Failed to read CA certificate: %v", err)
 			http.Error(w, fmt.Sprintf("Failed to read CA certificate: %v", err), http.StatusInternalServerError)
 			return
 		}
@@ -105,31 +127,36 @@ func NewJoinHandler(stateStore store.StateStore, caKeyPath, caCertPath string) h
 		nodeReg := map[string]interface{}{
 			"uid":             nodeUID,
 			"advertiseAddr":   joinReq.AdvertiseAddr,
-			"wireguardPubKey": joinReq.WireguardPubKey,
+			"wireguardPubKey": joinReq.WireGuardPubKey,
 			"joinTimestamp":   time.Now().Unix(),
 		}
 		nodeRegData, err := json.Marshal(nodeReg)
 		if err != nil {
+			log.Printf("Failed to marshal node registration: %v", err)
 			http.Error(w, fmt.Sprintf("Failed to marshal node registration: %v", err), http.StatusInternalServerError)
 			return
 		}
 
+		log.Printf("Storing node registration in etcd at key: %s", nodeRegKey)
 		if err := stateStore.Put(r.Context(), nodeRegKey, nodeRegData); err != nil {
+			log.Printf("Failed to store node registration: %v", err)
 			http.Error(w, fmt.Sprintf("Failed to store node registration: %v", err), http.StatusInternalServerError)
 			return
 		}
+		log.Printf("Successfully stored node registration in etcd")
 
 		// Prepare and send response
 		joinResp := JoinResponse{
-			NodeName:      nodeName,
-			NodeUID:       nodeUID,
-			SignedCert:    signedCert,
-			CACert:        caCert,
-			JoinTimestamp: time.Now().Unix(),
+			NodeName:          nodeName,
+			NodeUID:           nodeUID,
+			SignedCertificate: base64.StdEncoding.EncodeToString(signedCert),
+			CACertificate:     base64.StdEncoding.EncodeToString(caCert),
+			AssignedSubnet:    "10.100.0.0/24", // Placeholder for now, will be implemented in network phase
 		}
 
 		respData, err := json.Marshal(joinResp)
 		if err != nil {
+			log.Printf("Failed to marshal response: %v", err)
 			http.Error(w, fmt.Sprintf("Failed to marshal response: %v", err), http.StatusInternalServerError)
 			return
 		}
@@ -137,5 +164,6 @@ func NewJoinHandler(stateStore store.StateStore, caKeyPath, caCertPath string) h
 		w.Header().Set("Content-Type", "application/json")
 		w.WriteHeader(http.StatusOK)
 		w.Write(respData)
+		log.Printf("Successfully processed join request for node: %s", nodeName)
 	}
 }
diff --git a/internal/api/join_handler_test.go b/internal/api/join_handler_test.go
new file mode 100644
index 0000000..985ff44
--- /dev/null
+++ b/internal/api/join_handler_test.go
@@ -0,0 +1,168 @@
+package api
+
+import (
+	"bytes"
+	"context"
+	"encoding/base64"
+	"encoding/json"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"git.dws.rip/dubey/kat/internal/pki"
+	"git.dws.rip/dubey/kat/internal/store"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/mock"
+)
+
+// MockStateStore for testing
+type MockStateStore struct {
+	mock.Mock
+}
+
+func (m *MockStateStore) Put(ctx context.Context, key string, value []byte) error {
+	args := m.Called(ctx, key, value)
+	return args.Error(0)
+}
+
+func (m *MockStateStore) Get(ctx context.Context, key string) (*store.KV, error) {
+	args := m.Called(ctx, key)
+	if args.Get(0) == nil {
+		return nil, args.Error(1)
+	}
+	return args.Get(0).(*store.KV), args.Error(1)
+}
+
+func (m *MockStateStore) Delete(ctx context.Context, key string) error {
+	args := m.Called(ctx, key)
+	return args.Error(0)
+}
+
+func (m *MockStateStore) List(ctx context.Context, prefix string) ([]store.KV, error) {
+	args := m.Called(ctx, prefix)
+	return args.Get(0).([]store.KV), args.Error(1)
+}
+
+func (m *MockStateStore) Watch(ctx context.Context, keyOrPrefix string, startRevision int64) (<-chan store.WatchEvent, error) {
+	args := m.Called(ctx, keyOrPrefix, startRevision)
+	return args.Get(0).(chan store.WatchEvent), args.Error(1)
+}
+
+func (m *MockStateStore) Close() error {
+	args := m.Called()
+	return args.Error(0)
+}
+
+func (m *MockStateStore) Campaign(ctx context.Context, leaderID string, leaseTTLSeconds int64) (context.Context, error) {
+	args := m.Called(ctx, leaderID, leaseTTLSeconds)
+	if args.Get(0) == nil {
+		return nil, args.Error(1)
+	}
+	return args.Get(0).(context.Context), args.Error(1)
+}
+
+func (m *MockStateStore) Resign(ctx context.Context) error {
+	args := m.Called(ctx)
+	return args.Error(0)
+}
+
+func (m *MockStateStore) GetLeader(ctx context.Context) (string, error) {
+	args := m.Called(ctx)
+	return args.String(0), args.Error(1)
+}
+
+func (m *MockStateStore) DoTransaction(ctx context.Context, checks []store.Compare, onSuccess []store.Op, onFailure []store.Op) (bool, error) {
+	args := m.Called(ctx, checks, onSuccess, onFailure)
+	return args.Bool(0), args.Error(1)
+}
+
+func TestJoinHandler(t *testing.T) {
+	// Create temporary directory for test PKI files
+	tempDir, err := os.MkdirTemp("", "kat-test-pki-*")
+	if err != nil {
+		t.Fatalf("Failed to create temp directory: %v", err)
+	}
+	defer os.RemoveAll(tempDir)
+
+	// Generate CA for testing
+	caKeyPath := filepath.Join(tempDir, "ca.key")
+	caCertPath := filepath.Join(tempDir, "ca.crt")
+	err = pki.GenerateCA(tempDir, caKeyPath, caCertPath)
+	if err != nil {
+		t.Fatalf("Failed to generate test CA: %v", err)
+	}
+
+	// Generate a test CSR
+	nodeKeyPath := filepath.Join(tempDir, "node.key")
+	nodeCSRPath := filepath.Join(tempDir, "node.csr")
+	err = pki.GenerateCertificateRequest("test-node", nodeKeyPath, nodeCSRPath)
+	if err != nil {
+		t.Fatalf("Failed to generate test CSR: %v", err)
+	}
+
+	// Read the CSR file
+	csrData, err := os.ReadFile(nodeCSRPath)
+	if err != nil {
+		t.Fatalf("Failed to read CSR file: %v", err)
+	}
+
+	// Create mock state store
+	mockStore := new(MockStateStore)
+	mockStore.On("Put", mock.Anything, mock.MatchedBy(func(key string) bool {
+		return key == "/kat/nodes/registration/test-node"
+	}), mock.Anything).Return(nil)
+
+	// Create join handler
+	handler := NewJoinHandler(mockStore, caKeyPath, caCertPath)
+
+	// Create test request
+	joinReq := JoinRequest{
+		NodeName:        "test-node",
+		AdvertiseAddr:   "192.168.1.100",
+		CSRData:         base64.StdEncoding.EncodeToString(csrData),
+		WireGuardPubKey: "test-pubkey",
+	}
+	reqBody, err := json.Marshal(joinReq)
+	if err != nil {
+		t.Fatalf("Failed to marshal join request: %v", err)
+	}
+
+	// Create HTTP request
+	req := httptest.NewRequest("POST", "/internal/v1alpha1/join", bytes.NewBuffer(reqBody))
+	req.Header.Set("Content-Type", "application/json")
+	w := httptest.NewRecorder()
+
+	// Call handler
+	handler(w, req)
+
+	// Check response
+	resp := w.Result()
+	defer resp.Body.Close()
+	assert.Equal(t, http.StatusOK, resp.StatusCode)
+
+	// Read response body
+	respBody, err := io.ReadAll(resp.Body)
+	if err != nil {
+		t.Fatalf("Failed to read response body: %v", err)
+	}
+
+	// Parse response
+	var joinResp JoinResponse
+	err = json.Unmarshal(respBody, &joinResp)
+	if err != nil {
+		t.Fatalf("Failed to parse response: %v", err)
+	}
+
+	// Verify response fields
+	assert.Equal(t, "test-node", joinResp.NodeName)
+	assert.NotEmpty(t, joinResp.NodeUID)
+	assert.NotEmpty(t, joinResp.SignedCertificate)
+	assert.NotEmpty(t, joinResp.CACertificate)
+	assert.Equal(t, "10.100.0.0/24", joinResp.AssignedSubnet) // Placeholder value
+
+	// Verify mock was called
+	mockStore.AssertExpectations(t)
+}
diff --git a/internal/api/server.go b/internal/api/server.go
index 18ce1d7..caba510 100644
--- a/internal/api/server.go
+++ b/internal/api/server.go
@@ -136,6 +136,7 @@ func (s *Server) Stop(ctx context.Context) error {
 // RegisterJoinHandler registers the handler for agent join requests
 func (s *Server) RegisterJoinHandler(handler http.HandlerFunc) {
 	s.router.HandleFunc("POST", "/internal/v1alpha1/join", handler)
+	log.Printf("Registered join handler at /internal/v1alpha1/join")
 }
 
 // RegisterNodeStatusHandler registers the handler for node status updates