diff --git a/src/db/repositories.ts b/src/db/repositories.ts
index bee97c2fd..d461f16dd 100644
--- a/src/db/repositories.ts
+++ b/src/db/repositories.ts
@@ -1283,7 +1283,10 @@ export async function upsertDigestSubscription(
   const now = nowIso();
   const record: DigestSubscriptionRecord = {
     id: crypto.randomUUID(),
-    login: input.login,
+    // GitHub logins are case-insensitive, so normalize like every sibling subscription path
+    // (notification subscriptions, issue-watch) — otherwise a subscriber stored as "Foo" is missed on a
+    // "foo" lookup and the [login, email] conflict target accumulates case-variant duplicate rows.
+    login: input.login.toLowerCase(),
     email: input.email.toLowerCase(),
     status: input.status ?? "active",
     source: input.source ?? "app",
@@ -1319,7 +1322,7 @@ export async function upsertDigestSubscription(
 
 export async function listDigestSubscriptionsForLogin(env: Env, login: string): Promise<DigestSubscriptionRecord[]> {
   const db = getDb(env.DB);
-  const rows = await db.select().from(digestSubscriptions).where(eq(digestSubscriptions.login, login)).orderBy(desc(digestSubscriptions.updatedAt)).limit(20);
+  const rows = await db.select().from(digestSubscriptions).where(eq(digestSubscriptions.login, login.toLowerCase())).orderBy(desc(digestSubscriptions.updatedAt)).limit(20);
   return rows.map(toDigestSubscriptionRecord);
 }
 
diff --git a/test/unit/product-usage.test.ts b/test/unit/product-usage.test.ts
index c16df6d7c..77d0a8ed7 100644
--- a/test/unit/product-usage.test.ts
+++ b/test/unit/product-usage.test.ts
@@ -326,6 +326,21 @@ describe("product usage events", () => {
     ).resolves.toBeUndefined();
   });
 
+  it("matches digest subscriptions case-insensitively by login and dedupes case-variant logins", async () => {
+    const env = createTestEnv();
+    // Subscribe under a mixed-case login, then look up under a different casing — GitHub logins are
+    // case-insensitive, so it must still resolve (mirrors the notification/issue-watch subscription paths).
+    await upsertDigestSubscription(env, { login: "OktoFeesh1", email: "digest@example.com" });
+    await expect(listDigestSubscriptionsForLogin(env, "oktofeesh1")).resolves.toEqual([
+      expect.objectContaining({ login: "oktofeesh1", email: "digest@example.com", status: "active" }),
+    ]);
+    // Re-subscribing under another casing with the same email updates the one row instead of duplicating it.
+    await upsertDigestSubscription(env, { login: "OKTOFEESH1", email: "digest@example.com", status: "paused" });
+    await expect(listDigestSubscriptionsForLogin(env, "Oktofeesh1")).resolves.toEqual([
+      expect.objectContaining({ login: "oktofeesh1", email: "digest@example.com", status: "paused" }),
+    ]);
+  });
+
   it("summarizes recent events without counting stale records", async () => {
     const env = createTestEnv({ PRODUCT_USAGE_HASH_SALT: "fixed-test-salt" });
     await recordProductUsageEvent(env, {