diff --git a/api/__tests__/handlers.test.ts b/api/__tests__/handlers.test.ts
index bc4763b9..d20c8ba1 100644
--- a/api/__tests__/handlers.test.ts
+++ b/api/__tests__/handlers.test.ts
@@ -1,6 +1,19 @@
 import { describe, it, expect, vi, beforeEach, afterEach } from "vitest";
 import type { VercelRequest, VercelResponse } from "@vercel/node";
 
+vi.mock("../_lib/middleware.js", async () => {
+  const actual = await vi.importActual<typeof import("../_lib/middleware.js")>(
+    "../_lib/middleware.js"
+  );
+  return {
+    ...actual,
+    checkRateLimit: vi.fn(
+      async (...args: Parameters<typeof actual.checkRateLimit>) =>
+        actual.checkRateLimit(...args)
+    ),
+  };
+});
+
 // Stub the workspace builders/readers — these tests exercise the HTTP handler
 // contract (method guards, field validation, status codes, payload shape), not
 // the Soroban transaction building, which is unit-tested in the helpers package.
@@ -96,7 +109,10 @@ import vaultsHandler from "../v1/vaults/index";
 import positionsHandler from "../v1/positions/[publicKey]";
 import keeperHandler from "../v1/keepers/accrue";
 import rebalanceHandler from "../v1/keepers/rebalance";
-import { resetRateLimitForTesting } from "../_lib/middleware.js";
+import {
+  checkRateLimit,
+  resetRateLimitForTesting,
+} from "../_lib/middleware.js";
 import {
   buildDepositTx,
   runBlendAccrualKeeper,
@@ -146,6 +162,30 @@ beforeEach(() => {
 });
 
 describe("POST /api/v1/tx/deposit", () => {
+  it("returns 503 when the upstream rate limiter fails", async () => {
+    vi.mocked(checkRateLimit).mockRejectedValueOnce(
+      new Error("Upstash timeout")
+    );
+
+    const res = makeRes();
+    await depositHandler(
+      fakeReq({
+        method: "POST",
+        body: {
+          walletAddress: PUBKEY,
+          vaultId: "blend-usdc-fixed",
+          amount: "10",
+        },
+      }),
+      res
+    );
+
+    expect(res.statusCode).toBe(503);
+    expect(res.body).toEqual({
+      error: "Rate limiter unavailable; refusing to run",
+    });
+  });
+
   it("rejects non-POST methods with 405", async () => {
     const res = makeRes();
     await depositHandler(fakeReq({ method: "GET", body: {} }), res);
diff --git a/api/v1/positions/[publicKey].ts b/api/v1/positions/[publicKey].ts
index c236b51a..b1161523 100644
--- a/api/v1/positions/[publicKey].ts
+++ b/api/v1/positions/[publicKey].ts
@@ -4,7 +4,14 @@ import { applyCors, checkRateLimit } from "../../_lib/middleware.js";
 
 export default async function handler(req: VercelRequest, res: VercelResponse) {
   if (applyCors(req, res)) return;
-  if (!(await checkRateLimit(req, res))) return;
+  try {
+    if (!(await checkRateLimit(req, res))) return;
+  } catch (err) {
+    console.error("[positions] rate limit check failed:", err);
+    return res
+      .status(503)
+      .json({ error: "Rate limiter unavailable; refusing to run" });
+  }
   const { publicKey } = req.query as { publicKey: string };
 
   const result = await handleGetPositions(publicKey);
diff --git a/api/v1/tx/add-trustline.ts b/api/v1/tx/add-trustline.ts
index 5050e9be..c1a96395 100644
--- a/api/v1/tx/add-trustline.ts
+++ b/api/v1/tx/add-trustline.ts
@@ -4,7 +4,14 @@ import { applyCors, checkRateLimit } from "../../_lib/middleware.js";
 
 export default async function handler(req: VercelRequest, res: VercelResponse) {
   if (applyCors(req, res)) return;
-  if (!(await checkRateLimit(req, res, { strict: true }))) return;
+  try {
+    if (!(await checkRateLimit(req, res, { strict: true }))) return;
+  } catch (err) {
+    console.error("[tx/add-trustline] rate limit check failed:", err);
+    return res
+      .status(503)
+      .json({ error: "Rate limiter unavailable; refusing to run" });
+  }
   if (req.method !== "POST")
     return res.status(405).json({ error: "Method not allowed" });
 
diff --git a/api/v1/tx/deposit.ts b/api/v1/tx/deposit.ts
index 55ffa260..3e4e1e65 100644
--- a/api/v1/tx/deposit.ts
+++ b/api/v1/tx/deposit.ts
@@ -4,7 +4,14 @@ import { applyCors, checkRateLimit } from "../../_lib/middleware.js";
 
 export default async function handler(req: VercelRequest, res: VercelResponse) {
   if (applyCors(req, res)) return;
-  if (!(await checkRateLimit(req, res, { strict: true }))) return;
+  try {
+    if (!(await checkRateLimit(req, res, { strict: true }))) return;
+  } catch (err) {
+    console.error("[tx/deposit] rate limit check failed:", err);
+    return res
+      .status(503)
+      .json({ error: "Rate limiter unavailable; refusing to run" });
+  }
   if (req.method !== "POST")
     return res.status(405).json({ error: "Method not allowed" });
 
diff --git a/api/v1/tx/submit.ts b/api/v1/tx/submit.ts
index 34fb1823..a4bd863a 100644
--- a/api/v1/tx/submit.ts
+++ b/api/v1/tx/submit.ts
@@ -4,7 +4,14 @@ import { applyCors, checkRateLimit } from "../../_lib/middleware.js";
 
 export default async function handler(req: VercelRequest, res: VercelResponse) {
   if (applyCors(req, res)) return;
-  if (!(await checkRateLimit(req, res, { strict: true }))) return;
+  try {
+    if (!(await checkRateLimit(req, res, { strict: true }))) return;
+  } catch (err) {
+    console.error("[tx/submit] rate limit check failed:", err);
+    return res
+      .status(503)
+      .json({ error: "Rate limiter unavailable; refusing to run" });
+  }
   if (req.method !== "POST")
     return res.status(405).json({ error: "Method not allowed" });
 
diff --git a/api/v1/tx/withdraw.ts b/api/v1/tx/withdraw.ts
index 7b8711da..66db5379 100644
--- a/api/v1/tx/withdraw.ts
+++ b/api/v1/tx/withdraw.ts
@@ -4,7 +4,14 @@ import { applyCors, checkRateLimit } from "../../_lib/middleware.js";
 
 export default async function handler(req: VercelRequest, res: VercelResponse) {
   if (applyCors(req, res)) return;
-  if (!(await checkRateLimit(req, res, { strict: true }))) return;
+  try {
+    if (!(await checkRateLimit(req, res, { strict: true }))) return;
+  } catch (err) {
+    console.error("[tx/withdraw] rate limit check failed:", err);
+    return res
+      .status(503)
+      .json({ error: "Rate limiter unavailable; refusing to run" });
+  }
   if (req.method !== "POST")
     return res.status(405).json({ error: "Method not allowed" });
 
diff --git a/api/v1/vaults/[vaultId].ts b/api/v1/vaults/[vaultId].ts
index 9b3ec055..95286858 100644
--- a/api/v1/vaults/[vaultId].ts
+++ b/api/v1/vaults/[vaultId].ts
@@ -13,7 +13,14 @@ const KNOWN_VAULT_IDS = new Set(
 
 export default async function handler(req: VercelRequest, res: VercelResponse) {
   if (applyCors(req, res)) return;
-  if (!(await checkRateLimit(req, res))) return;
+  try {
+    if (!(await checkRateLimit(req, res))) return;
+  } catch (err) {
+    console.error("[vaults] rate limit check failed:", err);
+    return res
+      .status(503)
+      .json({ error: "Rate limiter unavailable; refusing to run" });
+  }
   const raw = req.query["vaultId"];
   const vaultId = typeof raw === "string" ? raw : undefined;
   if (!vaultId) return res.status(400).json({ error: "vaultId is required" });
diff --git a/api/v1/vaults/index.ts b/api/v1/vaults/index.ts
index c464788f..4512b55d 100644
--- a/api/v1/vaults/index.ts
+++ b/api/v1/vaults/index.ts
@@ -16,7 +16,14 @@ const TESTNET_CACHE_CONTROL = "no-store";
 
 export default async function handler(req: VercelRequest, res: VercelResponse) {
   if (applyCors(req, res)) return;
-  if (!(await checkRateLimit(req, res))) return;
+  try {
+    if (!(await checkRateLimit(req, res))) return;
+  } catch (err) {
+    console.error("[vaults] rate limit check failed:", err);
+    return res
+      .status(503)
+      .json({ error: "Rate limiter unavailable; refusing to run" });
+  }
 
   const result = await handleGetVaults();
   if (result.error) {