diff --git a/src/selfhost/metrics.ts b/src/selfhost/metrics.ts
index 044d04c7a..a2b93e545 100644
--- a/src/selfhost/metrics.ts
+++ b/src/selfhost/metrics.ts
@@ -96,6 +96,7 @@ export const DEFAULT_METRIC_META: readonly (readonly [string, MetricMeta])[] = [
   ["loopover_redis_gh_response_cache_total", { help: "Redis-backed GitHub response cache outcomes.", type: "counter" }],
   ["loopover_redis_gh_response_cache_hit_ratio", { help: "Redis GitHub response cache hit ratio (hits / (hits + misses)) at scrape time.", type: "gauge" }],
   ["loopover_redis_token_cache_total", { help: "Redis-backed GitHub token cache outcomes.", type: "counter" }],
+  ["loopover_redis_webhook_dedup_cache_total", { help: "Redis-backed webhook-dedup cache outcomes.", type: "counter" }],
   ["loopover_qdrant_queries_total", { help: "Qdrant vector query attempts.", type: "counter" }],
   ["loopover_qdrant_upserts_total", { help: "Qdrant vector upserted item count.", type: "counter" }],
   ["loopover_qdrant_errors_total", { help: "Qdrant vector operation errors.", type: "counter" }],
diff --git a/src/selfhost/redis-cache.ts b/src/selfhost/redis-cache.ts
index 50d692eb0..2404503eb 100644
--- a/src/selfhost/redis-cache.ts
+++ b/src/selfhost/redis-cache.ts
@@ -8,6 +8,17 @@ import { incr } from "./metrics";
 
 const WEBHOOK_DELIVERY_CACHE_PREFIX = "delivery:";
 
+const REDIS_WEBHOOK_DEDUP_CACHE_METRIC = "loopover_redis_webhook_dedup_cache_total";
+
+/** Records a webhook-dedup Redis cache outcome. Mirrors redis-token-cache.ts's recordTokenCacheMetric /
+ *  redis-response-cache.ts's recordRedisResponseCacheMetric: a named recorder over a `{result}`-labeled
+ *  counter, so a sustained Redis outage on this cache is as visible as one on either sibling. Kept separate
+ *  from `loopover_webhook_dedup_total{backend="redis"}`, which counts actual dedup HITS -- folding errors
+ *  into that counter would conflate "deliveries deduplicated" with "cache unavailable". */
+function recordWebhookDedupCacheMetric(result: "error"): void {
+  incr(REDIS_WEBHOOK_DEDUP_CACHE_METRIC, { result });
+}
+
 export function webhookDeliveryCacheKey(deliveryId: string): string {
   return `${WEBHOOK_DELIVERY_CACHE_PREFIX}${deliveryId}`;
 }
@@ -24,6 +35,9 @@ export async function isWebhookDeliveryDuplicate(cache: RedisCache, deliveryId:
     }
     return false;
   } catch {
+    // Fail open (unchanged): a cache outage must never block webhook processing -- but record it so the
+    // outage is visible, matching both sibling Redis caches.
+    recordWebhookDedupCacheMetric("error");
     return false;
   }
 }
@@ -33,7 +47,9 @@ export async function rememberWebhookDelivery(cache: RedisCache, deliveryId: str
   try {
     await cache.set(webhookDeliveryCacheKey(deliveryId), "1", ttlSeconds);
   } catch {
-    // best-effort — never block the response on a cache write failure
+    // best-effort — never block the response on a cache write failure (unchanged), but make the failure
+    // observable on the same metric surface as the sibling caches.
+    recordWebhookDedupCacheMetric("error");
   }
 }
 
diff --git a/test/unit/selfhost-redis-cache.test.ts b/test/unit/selfhost-redis-cache.test.ts
index b4b56fa78..345b35ef0 100644
--- a/test/unit/selfhost-redis-cache.test.ts
+++ b/test/unit/selfhost-redis-cache.test.ts
@@ -121,11 +121,22 @@ describe("isWebhookDeliveryDuplicate (#2075)", () => {
     expect(await renderMetrics()).toContain('loopover_webhook_dedup_total{backend="redis"} 1');
   });
 
-  it("returns false without incrementing when Redis get throws", async () => {
+  it("returns false without counting a dedup hit, and records an error metric, when Redis get throws (#8363)", async () => {
     const brokenRedis = { async get() { throw new Error("connection refused"); } } as unknown as Redis;
     const cache = createRedisCache(brokenRedis);
     await expect(isWebhookDeliveryDuplicate(cache, "delivery-3")).resolves.toBe(false);
-    expect(await renderMetrics()).not.toContain('loopover_webhook_dedup_total{backend="redis"}');
+    const rendered = await renderMetrics();
+    // Fail-open behavior is unchanged: a cache outage is never counted as a deduplicated delivery.
+    expect(rendered).not.toContain('loopover_webhook_dedup_total{backend="redis"}');
+    // ...but the outage is now observable, matching redis-token-cache / redis-response-cache.
+    expect(rendered).toContain('loopover_redis_webhook_dedup_cache_total{result="error"} 1');
+  });
+
+  it("rememberWebhookDelivery records an error metric when the Redis set throws, and still resolves (#8363)", async () => {
+    const brokenRedis = { async set() { throw new Error("connection refused"); } } as unknown as Redis;
+    const cache = createRedisCache(brokenRedis);
+    await expect(rememberWebhookDelivery(cache, "delivery-5")).resolves.toBeUndefined();
+    expect(await renderMetrics()).toContain('loopover_redis_webhook_dedup_cache_total{result="error"} 1');
   });
 
   it("rememberWebhookDelivery stores the delivery key for later dedup", async () => {