fix(time): prevent overflow in ExponentialDelayWithJitter backoff

pkg/time/delay.go

@@ -18,6 +18,7 @@ package time
 
 import (
 	"context"
+	"math/bits"
 	"math/rand"
 	"time"
 )
@@ -39,8 +40,17 @@ func LinearDelay(ctx context.Context, attempt uint, increment, maxDelay time.Dur
 // ExponentialDelayWithJitter is an exponential backoff strategy with jitter for retries. It calculates delay based on the attempt number,
 // adds jitter, and sleeps for that duration, capped at maxDelay.
 func ExponentialDelayWithJitter(ctx context.Context, attempt uint, baseDelay, maxDelay time.Duration) error {
-	delay := baseDelay * time.Duration(1<<attempt)
-	delay = min(delay, maxDelay)
+	// Compute baseDelay * 2^attempt, capped at maxDelay. The shift is only applied when it
+	// cannot overflow time.Duration; otherwise the result would exceed maxDelay anyway, so
+	// the cap is used directly. Without this guard a large attempt overflows int64 before the
+	// cap is applied, yielding a negative or zero delay that silently skips the backoff.
+	var delay time.Duration
+	if baseDelay > 0 {
+		delay = maxDelay
+		if attempt < uint(bits.LeadingZeros64(uint64(baseDelay))) {
+			delay = min(baseDelay<<attempt, maxDelay)
+		}
+	}
 
 	if delay > 0 {
 		jitter := time.Duration(rand.Int63n(int64(delay)))

pkg/time/delay_test.go

@@ -149,6 +149,30 @@ func TestExponentialDelayWithJitter(t *testing.T) {
 			expectedMin: 650 * time.Millisecond,
 			expectedMax: 3000 * time.Millisecond,
 		},
+		{
+			name:        "overflow attempt stays capped at maxDelay",
+			attempt:     39,
+			baseDelay:   30 * time.Millisecond,
+			maxDelay:    1 * time.Second,
+			expectedMin: 380 * time.Millisecond,
+			expectedMax: 1500 * time.Millisecond,
+		},
+		{
+			name:        "shift overflow attempt stays capped at maxDelay",
+			attempt:     62,
+			baseDelay:   30 * time.Millisecond,
+			maxDelay:    1 * time.Second,
+			expectedMin: 380 * time.Millisecond,
+			expectedMax: 1500 * time.Millisecond,
+		},
+		{
+			name:        "huge attempt stays capped at maxDelay",
+			attempt:     100,
+			baseDelay:   30 * time.Millisecond,
+			maxDelay:    1 * time.Second,
+			expectedMin: 380 * time.Millisecond,
+			expectedMax: 1500 * time.Millisecond,
+		},
 		{
 			name:        "zero baseDelay with jitter",
 			attempt:     5,