diff --git a/docs/release-control/v6/internal/subsystems/notifications.md b/docs/release-control/v6/internal/subsystems/notifications.md
index 6760b98d8..22ebb76e1 100644
--- a/docs/release-control/v6/internal/subsystems/notifications.md
+++ b/docs/release-control/v6/internal/subsystems/notifications.md
@@ -154,6 +154,26 @@ verifies three requests and the two-second exponential wait before the final
 request. This is transport timing proof, not durable queue retry, installed
 provider acceptance or recipient receipt.
 
+### Webhook transport retry exhaustion
+
+The enhanced retry sender makes one initial HTTP attempt plus `RetryCount`
+retries; non-positive counts select `WebhookDefaultRetries`. Repeated valid
+zero-delay 429 hints do not reset that budget. When all attempts fail, the
+sender returns the total attempt count and records one failed webhook history
+entry with the final status and the number of retries, not one entry per HTTP
+attempt. Every attempt retains the event ID and payload. A queue delivery that
+uses this sender has a transport ceiling of effective retry count plus one;
+layering up to `MaxAttempts` queue deliveries multiplies that ceiling, but does
+not guarantee destination receipt. Permanent errors may stop retries earlier.
+
+`TestSendWebhookWithRetry_RateLimitExhaustion` in
+`internal/notifications/webhook_enhanced_test.go` verifies configured counts
+1 and 2 and default selection for 0 and -1 against an owned HTTP fixture that
+always returns 429 with `Retry-After: 0`. It checks request identity and body,
+attempt exhaustion, and the single failed history record's status, retry
+count, payload size and error text. This is transport-budget and local history
+proof only, not queue persistence, provider receipt or installed qualification.
+
 Notification-management HTTP production and its unit/contract proof now live
 together under `internal/api/alerting/`. Router-level scope and integration
 tests remain in `internal/api`, while the compatibility aliases there keep the
diff --git a/internal/notifications/webhook_enhanced.go b/internal/notifications/webhook_enhanced.go
index 0917468ed..3c8d79a3c 100644
--- a/internal/notifications/webhook_enhanced.go
+++ b/internal/notifications/webhook_enhanced.go
@@ -302,10 +302,11 @@ func (n *NotificationManager) shouldSendWebhook(webhook EnhancedWebhookConfig, a
 
 // sendWebhookWithRetry implements exponential backoff retry with enhanced error tracking
 // Note: When used with the persistent queue, retry behavior is layered:
-// - Transport retries (this function): up to RetryCount attempts with exponential backoff
-// - Queue retries: up to MaxAttempts (default 3) with exponential backoff
-// Total attempts = RetryCount * MaxAttempts (e.g., 3 * 3 = 9 HTTP calls for a single notification)
-// This ensures delivery even during transient failures at either layer.
+// - Transport: one initial attempt plus RetryCount retries (non-positive counts use WebhookDefaultRetries)
+// - Queue: up to MaxAttempts delivery attempts with exponential backoff
+// The HTTP attempt ceiling is (effective RetryCount + 1) * MaxAttempts when
+// each queue delivery uses this transport. Permanent errors can stop earlier;
+// exhausting either retry budget does not guarantee delivery.
 func (n *NotificationManager) sendWebhookWithRetry(webhook EnhancedWebhookConfig, payload []byte, eventID string) error {
 	maxRetries := webhook.RetryCount
 	if maxRetries <= 0 {
diff --git a/internal/notifications/webhook_enhanced_test.go b/internal/notifications/webhook_enhanced_test.go
index 68a2ce0c9..48f2396f0 100644
--- a/internal/notifications/webhook_enhanced_test.go
+++ b/internal/notifications/webhook_enhanced_test.go
@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"io"
 	"net/http"
+	"sync/atomic"
 	"testing"
 	"time"
 
@@ -292,6 +293,49 @@ func TestParseRetryAfterBackoff(t *testing.T) {
 	}
 }
 
+// Even repeated valid zero-delay hints must not reset the transport retry budget.
+func TestSendWebhookWithRetry_RateLimitExhaustion(t *testing.T) {
+	for _, retries := range []int{1, 2, 0, -1} {
+		t.Run(fmt.Sprint(retries), func(t *testing.T) {
+			nm := NewNotificationManager("http://pulse.local")
+			t.Cleanup(nm.Stop)
+			require.NoError(t, nm.UpdateAllowedPrivateCIDRs("127.0.0.1"))
+			var attempts atomic.Int32
+			payload := []byte(`{"test":true}`)
+			server := newIPv4HTTPServer(t, http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+				attempts.Add(1)
+				assert.Equal(t, "limited:alert", r.Header.Get("X-Pulse-Event-ID"))
+				body, err := io.ReadAll(r.Body)
+				assert.NoError(t, err)
+				assert.Equal(t, payload, body)
+				w.Header().Set("Retry-After", "0")
+				w.WriteHeader(http.StatusTooManyRequests)
+			}))
+			defer server.Close()
+			webhook := EnhancedWebhookConfig{
+				WebhookConfig: WebhookConfig{Name: "Limited webhook", URL: server.URL},
+				RetryEnabled:  true,
+				RetryCount:    retries,
+			}
+			wantRetries := retries
+			if wantRetries <= 0 {
+				wantRetries = WebhookDefaultRetries
+			}
+			err := nm.sendWebhookWithRetry(webhook, payload, "limited:alert")
+			require.Error(t, err)
+			assert.Contains(t, err.Error(), fmt.Sprintf("after %d attempts", wantRetries+1))
+			assert.Equal(t, int32(wantRetries+1), attempts.Load())
+			history := nm.GetWebhookHistory()
+			require.Len(t, history, 1, "one failed delivery, not one history entry per HTTP attempt")
+			assert.False(t, history[0].Success)
+			assert.Equal(t, http.StatusTooManyRequests, history[0].StatusCode)
+			assert.Equal(t, wantRetries, history[0].RetryAttempts)
+			assert.Equal(t, len(payload), history[0].PayloadSize)
+			assert.Contains(t, history[0].ErrorMessage, "HTTP 429")
+		})
+	}
+}
+
 func TestSendWebhookWithRetry_429RetryAfter(t *testing.T) {
 	nm := NewNotificationManager("http://pulse.local")
 	_ = nm.UpdateAllowedPrivateCIDRs("127.0.0.1")