diff --git a/src/__tests__/drepStatus.test.ts b/src/__tests__/drepStatus.test.ts
index 34dbd366..2eb18331 100644
--- a/src/__tests__/drepStatus.test.ts
+++ b/src/__tests__/drepStatus.test.ts
@@ -10,6 +10,16 @@ import { fetchDrepStatus } from "@/lib/governance/drep-status";
  * inactive.
  */
 
+/** What Mesh's BlockfrostProvider.get rejects with (parseHttpError). */
+const meshRejection = (status: number) =>
+  JSON.stringify({
+    data: { status_code: status, error: "x", message: "x" },
+    headers: { "content-type": "application/json" },
+    status,
+  });
+const MESH_404 = meshRejection(404);
+const MESH_500 = meshRejection(500);
+
 function provider(impl: (url: string) => Promise<unknown>) {
   return { get: jest.fn(impl) };
 }
@@ -45,6 +55,23 @@ describe("fetchDrepStatus", () => {
     await expect(fetchDrepStatus(byMessage, "drep1abc")).resolves.toEqual({ active: false });
   });
 
+  it("treats Mesh's real 404 rejection — a JSON string, not an Error — as inactive", async () => {
+    // Before this case was handled, an MCP vote draft for a never-registered
+    // DRep failed as DREP_LOOKUP_FAILED instead of telling the user to
+    // register first.
+    const p = provider(async () => {
+      throw MESH_404;
+    });
+    await expect(fetchDrepStatus(p, "drep1abc")).resolves.toEqual({ active: false });
+  });
+
+  it("rethrows Mesh's string rejection for any other status", async () => {
+    const p = provider(async () => {
+      throw MESH_500;
+    });
+    await expect(fetchDrepStatus(p, "drep1abc")).rejects.toBe(MESH_500);
+  });
+
   it("rethrows any other provider failure", async () => {
     const p = provider(async () => {
       throw Object.assign(new Error("Blockfrost 500"), { status: 500 });
diff --git a/src/__tests__/stakeAccountInfo.test.ts b/src/__tests__/stakeAccountInfo.test.ts
new file mode 100644
index 00000000..09b069ae
--- /dev/null
+++ b/src/__tests__/stakeAccountInfo.test.ts
@@ -0,0 +1,117 @@
+import { beforeAll, beforeEach, describe, expect, it, jest } from "@jest/globals";
+import type { NextApiRequest, NextApiResponse } from "next";
+import { createMockResponse } from "./apiTestUtils";
+
+const providerGetMock = jest.fn<(path: string) => Promise<unknown>>();
+const getProviderMock = jest.fn((_network: number) => ({ get: providerGetMock }));
+
+jest.mock("@/lib/cors", () => ({
+  __esModule: true,
+  addCorsCacheBustingHeaders: jest.fn(),
+  cors: jest.fn(async () => undefined),
+}));
+
+jest.mock("@/lib/security/requestGuards", () => ({
+  __esModule: true,
+  applyRateLimit: () => true,
+  applyBotRateLimit: () => true,
+}));
+
+jest.mock("@/lib/verifyJwt", () => ({
+  __esModule: true,
+  verifyJwt: (token: string) => (token === "good" ? { address: "addr_test1x" } : null),
+  isBotJwt: () => false,
+}));
+
+jest.mock("@/utils/get-provider", () => ({
+  __esModule: true,
+  getProvider: (network: number) => getProviderMock(network),
+}));
+
+let handler: (req: NextApiRequest, res: NextApiResponse) => Promise<unknown>;
+
+beforeAll(async () => {
+  ({ default: handler } = await import("../pages/api/v1/stakeAccountInfo"));
+});
+
+beforeEach(() => {
+  jest.clearAllMocks();
+  jest.spyOn(console, "error").mockImplementation(() => undefined);
+});
+
+// Well-formed bech32 reward addresses (header byte + 28-byte credential).
+const MAINNET = "stake1uyrswpc8qurswpc8qurswpc8qurswpc8qurswpc8qurswpc4vqlc2";
+const TESTNET = "stake_test1uqrswpc8qurswpc8qurswpc8qurswpc8qurswpc8qurswpcjx2auh";
+// Script-credential reward address (header 0xf1), as a multisig wallet has.
+const MAINNET_SCRIPT = "stake17yrswpc8qurswpc8qurswpc8qurswpc8qurswpc8qurswpcuyul02";
+
+/** What Mesh's BlockfrostProvider.get rejects with (parseHttpError). */
+const meshRejection = (status: number) =>
+  JSON.stringify({ data: { status_code: status }, headers: {}, status });
+
+async function call(stakeAddress: unknown, token = "good") {
+  const req = {
+    method: "GET",
+    headers: { authorization: `Bearer ${token}` },
+    query: stakeAddress === undefined ? {} : { stakeAddress },
+  } as unknown as NextApiRequest;
+  const res = createMockResponse();
+  await handler(req, res);
+  return res;
+}
+
+describe("GET /api/v1/stakeAccountInfo", () => {
+  it("requires a valid bearer token", async () => {
+    const res = await call(TESTNET, "bad");
+    expect(res.statusCode).toBe(401);
+    expect(providerGetMock).not.toHaveBeenCalled();
+  });
+
+  it("reads a registered account from the network its address names", async () => {
+    providerGetMock.mockResolvedValueOnce({ active: true, pool_id: "pool1abc" });
+    const res = await call(` ${TESTNET} `);
+    expect(getProviderMock).toHaveBeenCalledWith(0);
+    expect(providerGetMock).toHaveBeenCalledWith(`/accounts/${TESTNET}`);
+    expect(res.statusCode).toBe(200);
+    expect(res.json).toHaveBeenCalledWith({ active: true, poolId: "pool1abc" });
+
+    for (const address of [MAINNET, MAINNET_SCRIPT]) {
+      providerGetMock.mockResolvedValueOnce({ active: false, pool_id: null });
+      const mainnet = await call(address);
+      expect(mainnet.statusCode).toBe(200);
+      expect(getProviderMock).toHaveBeenLastCalledWith(1);
+      expect(providerGetMock).toHaveBeenLastCalledWith(`/accounts/${address}`);
+    }
+  });
+
+  it("answers 200 inactive for a never-registered account (Mesh's string 404)", async () => {
+    // A fresh multisig wallet's stake credential has never appeared on chain;
+    // that is the normal "not registered yet" answer, not a server error.
+    providerGetMock.mockRejectedValueOnce(meshRejection(404));
+    const res = await call(TESTNET);
+    expect(res.statusCode).toBe(200);
+    expect(res.json).toHaveBeenCalledWith({ active: false, poolId: null });
+  });
+
+  it("still answers 500 when the lookup itself fails", async () => {
+    providerGetMock.mockRejectedValueOnce(meshRejection(500));
+    const res = await call(TESTNET);
+    expect(res.statusCode).toBe(500);
+  });
+
+  it.each([
+    ["missing", undefined],
+    ["empty", "  "],
+    ["repeated", [TESTNET, TESTNET]],
+    ["a path escape", `${TESTNET}/../../addresses/addr_test1x`],
+    ["another endpoint", `${TESTNET}/history`],
+    ["a query string", `${TESTNET}?page=2`],
+    ["a payment address", "addr_test1qrswpc8qurswpc8qurswpc8qurswpc8qurswpc8qurswpcjx2auh"],
+    ["a truncated address", TESTNET.slice(0, -1)],
+    ["characters outside bech32", TESTNET.replace(/q/g, "b")],
+  ])("rejects %s with 400 before calling Blockfrost", async (_label, value) => {
+    const res = await call(value);
+    expect(res.statusCode).toBe(400);
+    expect(providerGetMock).not.toHaveBeenCalled();
+  });
+});
diff --git a/src/__tests__/stakeAccountStatus.test.ts b/src/__tests__/stakeAccountStatus.test.ts
index c044b24d..be7803e8 100644
--- a/src/__tests__/stakeAccountStatus.test.ts
+++ b/src/__tests__/stakeAccountStatus.test.ts
@@ -10,6 +10,16 @@ import { fetchStakeAccountStatus } from "@/lib/staking/stake-account-status";
  * surface rather than read as inactive.
  */
 
+/** What Mesh's BlockfrostProvider.get rejects with (parseHttpError). */
+const meshRejection = (status: number) =>
+  JSON.stringify({
+    data: { status_code: status, error: "x", message: "x" },
+    headers: { "content-type": "application/json" },
+    status,
+  });
+const MESH_404 = meshRejection(404);
+const MESH_500 = meshRejection(500);
+
 function provider(impl: (url: string) => Promise<unknown>) {
   return { get: jest.fn(impl) };
 }
@@ -67,6 +77,27 @@ describe("fetchStakeAccountStatus", () => {
     });
   });
 
+  it("treats Mesh's real 404 rejection — a JSON string, not an Error — as inactive", async () => {
+    // BlockfrostProvider.get rejects with parseHttpError's JSON.stringify of
+    // the axios response. Before this case was handled, every never-registered
+    // stake account surfaced as a lookup failure (a 500 from stakeAccountInfo,
+    // a 502 STAKE_LOOKUP_FAILED from the MCP draft pipeline).
+    const p = provider(async () => {
+      throw MESH_404;
+    });
+    await expect(fetchStakeAccountStatus(p, "stake_test1uqx")).resolves.toEqual({
+      active: false,
+      poolId: null,
+    });
+  });
+
+  it("rethrows Mesh's string rejection for any other status", async () => {
+    const p = provider(async () => {
+      throw MESH_500;
+    });
+    await expect(fetchStakeAccountStatus(p, "stake_test1uqx")).rejects.toBe(MESH_500);
+  });
+
   it("rethrows any other provider failure", async () => {
     const p = provider(async () => {
       throw Object.assign(new Error("Blockfrost 500"), { status: 500 });
@@ -74,3 +105,35 @@ describe("fetchStakeAccountStatus", () => {
     await expect(fetchStakeAccountStatus(p, "stake_test1uqx")).rejects.toThrow("Blockfrost 500");
   });
 });
+
+describe("fetchStakeAccountStatus against Mesh's real BlockfrostProvider", () => {
+  // The mocks above copy a rejection shape; this pins it to the library, so a
+  // Mesh upgrade that changes how get() rejects shows up here first.
+  it("reads Blockfrost's 404 for an unseen account as inactive", async () => {
+    const http = await import("node:http");
+    const { BlockfrostProvider } = await import("@meshsdk/core");
+    const server = http.createServer((_req, res) => {
+      res.writeHead(404, { "content-type": "application/json" });
+      res.end(JSON.stringify({ status_code: 404, error: "Not Found" }));
+    });
+    await new Promise<void>((resolve) => server.listen(0, "127.0.0.1", resolve));
+    // axios honours HTTP(S)_PROXY even for 127.0.0.1; a proxied dev shell
+    // would otherwise send this request somewhere else.
+    const savedNoProxy = { upper: process.env.NO_PROXY, lower: process.env.no_proxy };
+    process.env.NO_PROXY = process.env.no_proxy = "127.0.0.1,localhost";
+    try {
+      const { port } = server.address() as { port: number };
+      const p = new BlockfrostProvider(`http://127.0.0.1:${port}`);
+      await expect(fetchStakeAccountStatus(p, "stake_test1uqx")).resolves.toEqual({
+        active: false,
+        poolId: null,
+      });
+    } finally {
+      for (const [key, value] of [["NO_PROXY", savedNoProxy.upper], ["no_proxy", savedNoProxy.lower]] as const) {
+        if (value === undefined) delete process.env[key];
+        else process.env[key] = value;
+      }
+      await new Promise((resolve) => server.close(resolve));
+    }
+  });
+});
diff --git a/src/lib/governance/drep-profile.ts b/src/lib/governance/drep-profile.ts
index 77da092e..24dc9bd9 100644
--- a/src/lib/governance/drep-profile.ts
+++ b/src/lib/governance/drep-profile.ts
@@ -2,6 +2,7 @@ import type {
   BlockfrostDrepInfo,
   BlockfrostDrepMetadata,
 } from "@/types/governance";
+import { isBlockfrostNotFound } from "@/utils/blockfrost-not-found";
 
 /** Anything with Blockfrost's raw `get(path)`: the light reader or Mesh's provider. */
 type DrepReader = {
@@ -66,33 +67,6 @@ export async function fetchDrepProfile(
   };
 }
 
-/**
- * Whether a Blockfrost read failed with 404.
- *
- * The light reader (`src/utils/blockfrost-get.ts`) rejects with a JSON
- * *string* — `{"data":…,"status":404}` — copying Mesh's BlockfrostProvider,
- * while other code paths reject with an object. Checking only
- * `err.response.status` (what the explorer pages did) never matches the
- * string, so every DRep without metadata was logged as an error.
- */
-export function isBlockfrostNotFound(error: unknown): boolean {
-  let value: unknown = error;
-  if (typeof value === "string") {
-    try {
-      value = JSON.parse(value);
-    } catch {
-      return false;
-    }
-  }
-  if (!value || typeof value !== "object") return false;
-  const e = value as {
-    status?: unknown;
-    response?: { status?: unknown };
-    data?: { status_code?: unknown };
-  };
-  return (
-    e.status === 404 ||
-    e.response?.status === 404 ||
-    e.data?.status_code === 404
-  );
-}
+// Lives in a shared util so the registration probes use the same check;
+// re-exported for existing importers of this module.
+export { isBlockfrostNotFound };
diff --git a/src/lib/governance/drep-status.ts b/src/lib/governance/drep-status.ts
index 71989fae..1ecff87c 100644
--- a/src/lib/governance/drep-status.ts
+++ b/src/lib/governance/drep-status.ts
@@ -1,3 +1,5 @@
+import { isBlockfrostNotFound } from "@/utils/blockfrost-not-found";
+
 export type DrepStatus = {
   /** Registered as a DRep on chain right now (a registration not since retired). */
   active: boolean;
@@ -44,8 +46,10 @@ export async function fetchDrepStatus(
 }
 
 function isNotFound(error: unknown): boolean {
+  // Mesh's BlockfrostProvider rejects with a JSON string, not an Error, so
+  // the string shape is the one production actually sees.
   return (
-    (error as { status?: number })?.status === 404 ||
+    isBlockfrostNotFound(error) ||
     (error instanceof Error && error.message.includes("404"))
   );
 }
diff --git a/src/lib/staking/stake-account-status.ts b/src/lib/staking/stake-account-status.ts
index 9488ad61..c783af0b 100644
--- a/src/lib/staking/stake-account-status.ts
+++ b/src/lib/staking/stake-account-status.ts
@@ -1,3 +1,5 @@
+import { isBlockfrostNotFound } from "@/utils/blockfrost-not-found";
+
 export type StakeAccountStatus = {
   /** Registered on chain right now (a registration not since undone). */
   active: boolean;
@@ -48,8 +50,10 @@ export async function fetchStakeAccountStatus(
 }
 
 function isNotFound(error: unknown): boolean {
+  // Mesh's BlockfrostProvider rejects with a JSON string, not an Error, so
+  // the string shape is the one production actually sees.
   return (
-    (error as { status?: number })?.status === 404 ||
+    isBlockfrostNotFound(error) ||
     (error instanceof Error && error.message.includes("404"))
   );
 }
diff --git a/src/pages/api/v1/stakeAccountInfo.ts b/src/pages/api/v1/stakeAccountInfo.ts
index 76f229f6..1d9d2627 100644
--- a/src/pages/api/v1/stakeAccountInfo.ts
+++ b/src/pages/api/v1/stakeAccountInfo.ts
@@ -5,6 +5,19 @@ import { applyRateLimit, applyBotRateLimit } from "@/lib/security/requestGuards"
 import { fetchStakeAccountStatus } from "@/lib/staking/stake-account-status";
 import { getProvider } from "@/utils/get-provider";
 
+/**
+ * A lowercase bech32 reward address (key or script credential): `stake1` /
+ * `stake_test1` plus 53 characters of the bech32 alphabet (29 bytes of header
+ * + credential, then the checksum). The checksum itself is Blockfrost's to
+ * check; the shape is what keeps the value inside the path segment.
+ *
+ * The value is spliced into Blockfrost's `/accounts/{stake}` path with the
+ * server's project key, so anything else — `../…`, `?…`, a payment address —
+ * must not reach the request: it either reads another endpoint or comes
+ * back as a Blockfrost 400 that this route would report as a 500.
+ */
+const REWARD_ADDRESS = /^(stake|stake_test)1[qpzry9x8gf2tvdw0s3jn54khce6mua7l]{53}$/;
+
 export default async function handler(req: NextApiRequest, res: NextApiResponse) {
   addCorsCacheBustingHeaders(res);
   if (!applyRateLimit(req, res, { keySuffix: "v1/stakeAccountInfo" })) return;
@@ -21,16 +34,18 @@ export default async function handler(req: NextApiRequest, res: NextApiResponse)
   if (isBotJwt(payload) && !applyBotRateLimit(req, res, payload.botId)) return;
 
   const { stakeAddress } = req.query;
-  if (typeof stakeAddress !== "string" || !stakeAddress.trim()) {
+  const parsed =
+    typeof stakeAddress === "string" ? REWARD_ADDRESS.exec(stakeAddress.trim()) : null;
+  if (!parsed) {
     return res.status(400).json({ error: "Missing or invalid stakeAddress parameter" });
   }
 
-  const network = stakeAddress.startsWith("stake_test") ? 0 : 1;
+  const network = parsed[1] === "stake_test" ? 0 : 1;
   const provider = getProvider(network);
 
   try {
     // Never-registered accounts (Blockfrost 404) come back as inactive.
-    const info = await fetchStakeAccountStatus(provider, stakeAddress);
+    const info = await fetchStakeAccountStatus(provider, parsed[0]);
     return res.status(200).json(info);
   } catch (e) {
     console.error("stakeAccountInfo error:", e);
diff --git a/src/utils/blockfrost-not-found.ts b/src/utils/blockfrost-not-found.ts
new file mode 100644
index 00000000..c972fda5
--- /dev/null
+++ b/src/utils/blockfrost-not-found.ts
@@ -0,0 +1,31 @@
+/**
+ * Whether a Blockfrost read failed with 404.
+ *
+ * Mesh's `BlockfrostProvider.get` — and the light reader
+ * (`src/utils/blockfrost-get.ts`), which copies it — rejects with a JSON
+ * *string*: `{"data":{"status_code":404,…},"headers":…,"status":404}`, not an
+ * Error. Checking `err.status` or `err instanceof Error` never matches that
+ * string, so a "never seen on chain" answer was read as a lookup failure.
+ * Other code paths reject with an object, so both shapes are accepted.
+ */
+export function isBlockfrostNotFound(error: unknown): boolean {
+  let value: unknown = error;
+  if (typeof value === "string") {
+    try {
+      value = JSON.parse(value);
+    } catch {
+      return false;
+    }
+  }
+  if (!value || typeof value !== "object") return false;
+  const e = value as {
+    status?: unknown;
+    response?: { status?: unknown };
+    data?: { status_code?: unknown };
+  };
+  return (
+    e.status === 404 ||
+    e.response?.status === 404 ||
+    e.data?.status_code === 404
+  );
+}