diff --git a/src/app/api/wakatime/sync/route.ts b/src/app/api/wakatime/sync/route.ts
index 13eb04a9d..0c9fea88b 100644
--- a/src/app/api/wakatime/sync/route.ts
+++ b/src/app/api/wakatime/sync/route.ts
@@ -9,80 +9,106 @@ export async function GET(req: Request) {
   const authError = validateCronRequest(req);
   if (authError) return authError;
 
-  // Fetch users with wakatime keys
-  const { data: users, error } = await supabaseAdmin
-    .from("users")
-    .select("id, wakatime_api_key_encrypted, wakatime_api_key_iv")
-    .not("wakatime_api_key_encrypted", "is", null)
-    .not("wakatime_api_key_iv", "is", null);
-
-  if (error) {
-    console.error("Failed to fetch users for wakatime sync:", error);
-    return NextResponse.json({ error: "Database error" }, { status: 500 });
-  }
-
+  // Paginate the users query. The old implementation did one unbounded
+  // `.select()` and pulled every wakatime user (plus their encrypted keys)
+  // into serverless memory in a single response. At a few thousand users
+  // that either hits Supabase's ~4.5 MB response cap, blows the function
+  // timeout, or gets killed by the memory limit and the nightly sync
+  // silently fails. Mirror the pattern used by /api/cron/sync (which was
+  // already paginated) — 50-user pages, deterministic ordering by id,
+  // break out when the page is short. See issue #3161.
+  const PAGE_SIZE = 50;
+  const CHUNK_SIZE = 5;
   let successCount = 0;
   let failureCount = 0;
+  let page = 0;
+  let hasMore = true;
 
-  // Process in chunks to avoid overwhelming the API and improve speed
-  const CHUNK_SIZE = 5;
-  for (let i = 0; i < users.length; i += CHUNK_SIZE) {
-    const chunk = users.slice(i, i + CHUNK_SIZE);
-
-    await Promise.allSettled(chunk.map(async (user) => {
-      try {
-        const apiKey = decryptToken(
-          user.wakatime_api_key_encrypted!,
-          user.wakatime_api_key_iv!
-        );
-
-        if (!apiKey) {
-          console.error(`Decryption failed for user ${user.id}`);
-          failureCount++;
-          return;
-        }
+  while (hasMore) {
+    const { data: users, error } = await supabaseAdmin
+      .from("users")
+      .select("id, wakatime_api_key_encrypted, wakatime_api_key_iv")
+      .not("wakatime_api_key_encrypted", "is", null)
+      .not("wakatime_api_key_iv", "is", null)
+      .order("id")
+      .range(page * PAGE_SIZE, (page + 1) * PAGE_SIZE - 1);
 
-        // Fetch from Wakatime with no-store cache
-        const res = await fetch("https://wakatime.com/api/v1/users/current/summaries?range=Last%207%20Days", {
-          headers: {
-            Authorization: `Basic ${Buffer.from(apiKey + ":").toString("base64")}`,
-          },
-          cache: "no-store"
-        });
+    if (error) {
+      console.error("Failed to fetch users for wakatime sync:", error);
+      return NextResponse.json({ error: "Database error" }, { status: 500 });
+    }
 
-        if (!res.ok) {
-          console.error(`Wakatime API error for user ${user.id}: ${res.status}`);
-          failureCount++;
-          return;
-        }
+    if (!users || users.length === 0) {
+      hasMore = false;
+      break;
+    }
+
+    // Process each page in chunks to avoid overwhelming the Wakatime API
+    for (let i = 0; i < users.length; i += CHUNK_SIZE) {
+      const chunk = users.slice(i, i + CHUNK_SIZE);
+
+      await Promise.allSettled(chunk.map(async (user) => {
+        try {
+          const apiKey = decryptToken(
+            user.wakatime_api_key_encrypted!,
+            user.wakatime_api_key_iv!
+          );
+
+          if (!apiKey) {
+            console.error(`Decryption failed for user ${user.id}`);
+            failureCount++;
+            return;
+          }
 
-        const data = await res.json();
-        const now = new Date().toISOString();
+          // Fetch from Wakatime with no-store cache
+          const res = await fetch("https://wakatime.com/api/v1/users/current/summaries?range=Last%207%20Days", {
+            headers: {
+              Authorization: `Basic ${Buffer.from(apiKey + ":").toString("base64")}`,
+            },
+            cache: "no-store"
+          });
 
-        const statsToUpsert = data.data.map((day: any) => ({
-          user_id: user.id,
-          date: day.range.date,
-          total_seconds: Math.round(day.grand_total.total_seconds),
-          languages: day.languages.map((l: any) => ({ name: l.name, total_seconds: l.total_seconds, percent: l.percent })),
-          projects: day.projects.map((p: any) => ({ name: p.name, total_seconds: p.total_seconds, percent: p.percent })),
-          updated_at: now
-        }));
+          if (!res.ok) {
+            console.error(`Wakatime API error for user ${user.id}: ${res.status}`);
+            failureCount++;
+            return;
+          }
 
-        const { error: upsertError } = await supabaseAdmin
-          .from("wakatime_stats")
-          .upsert(statsToUpsert, { onConflict: "user_id, date" });
+          const data = await res.json();
+          const now = new Date().toISOString();
 
-        if (upsertError) {
-          console.error(`Failed to upsert wakatime stats for user ${user.id}:`, upsertError);
+          const statsToUpsert = data.data.map((day: any) => ({
+            user_id: user.id,
+            date: day.range.date,
+            total_seconds: Math.round(day.grand_total.total_seconds),
+            languages: day.languages.map((l: any) => ({ name: l.name, total_seconds: l.total_seconds, percent: l.percent })),
+            projects: day.projects.map((p: any) => ({ name: p.name, total_seconds: p.total_seconds, percent: p.percent })),
+            updated_at: now
+          }));
+
+          const { error: upsertError } = await supabaseAdmin
+            .from("wakatime_stats")
+            .upsert(statsToUpsert, { onConflict: "user_id, date" });
+
+          if (upsertError) {
+            console.error(`Failed to upsert wakatime stats for user ${user.id}:`, upsertError);
+            failureCount++;
+          } else {
+            successCount++;
+          }
+        } catch (e) {
+          console.error(`Error processing wakatime stats for user ${user.id}:`, e);
           failureCount++;
-        } else {
-          successCount++;
         }
-      } catch (e) {
-        console.error(`Error processing wakatime stats for user ${user.id}:`, e);
-        failureCount++;
-      }
-    }));
+      }));
+    }
+
+    // Short page means we've reached the tail — stop paging.
+    if (users.length < PAGE_SIZE) {
+      hasMore = false;
+    } else {
+      page += 1;
+    }
   }
 
   return NextResponse.json({ success: successCount, failure: failureCount });