diff --git a/packages/api/src/routes/vendors.ts b/packages/api/src/routes/vendors.ts
index 2168ed5..88615ee 100644
--- a/packages/api/src/routes/vendors.ts
+++ b/packages/api/src/routes/vendors.ts
@@ -114,6 +114,39 @@ vendorRouter.post("/", async (req: Request, res: Response) => {
 });
 
 // GET /api/vendors/:id — Get single vendor with full stats
+// GET /api/vendors/reliability — per-vendor data-reliability scores (freshness/frequency/coverage)
+vendorRouter.get("/reliability", async (_req: Request, res: Response) => {
+  try {
+    const result = await pool.query(`
+      SELECT v.id::text AS vendor_id, v.name AS vendor_name,
+             COUNT(DISTINCT t.id)::int     AS sku_count,
+             COUNT(po.transceiver_id)::int AS obs_count,
+             MAX(po.time)                  AS last_obs
+      FROM vendors v
+      JOIN transceivers t ON t.vendor_id = v.id
+      LEFT JOIN price_observations po ON po.transceiver_id = t.id
+      GROUP BY v.id, v.name
+      HAVING COUNT(DISTINCT t.id) > 0`);
+    const rows = result.rows as Array<{ vendor_id: string; vendor_name: string; sku_count: number; obs_count: number; last_obs: string | null }>;
+    const maxSku = Math.max(1, ...rows.map((r) => r.sku_count));
+    const maxObs = Math.max(1, ...rows.map((r) => r.obs_count));
+    const now = Date.now();
+    const vendors = rows.map((r) => {
+      const daysStale = r.last_obs ? Math.max(0, (now - new Date(r.last_obs).getTime()) / 86400000) : 999;
+      const freshness_score = Math.max(0, Math.min(100, Math.round(100 - daysStale * 3)));
+      const frequency_score = Math.round(100 * Math.min(1, Math.log10(r.obs_count + 1) / Math.log10(maxObs + 1)));
+      const coverage_score = Math.round(100 * Math.min(1, r.sku_count / maxSku));
+      const reliability_score = Math.round(0.4 * freshness_score + 0.3 * frequency_score + 0.3 * coverage_score);
+      return { vendor_id: r.vendor_id, vendor_name: r.vendor_name, sku_count: r.sku_count, obs_count: r.obs_count, last_obs: r.last_obs, freshness_score, frequency_score, coverage_score, reliability_score };
+    });
+    vendors.sort((a, b) => b.reliability_score - a.reliability_score);
+    res.json({ success: true, count: vendors.length, vendors });
+  } catch (err) {
+    console.error("vendor reliability error:", err);
+    res.status(500).json({ success: false, error: "Failed to compute vendor reliability" });
+  }
+});
+
 vendorRouter.get("/:id", async (req: Request, res: Response, next: NextFunction) => {
   if (req.params.id === "market-share" || req.params.id === "intelligence") return next();
   try {