diff --git a/clients/cli/__tests__/stored-auth.test.ts b/clients/cli/__tests__/stored-auth.test.ts
index 3fb5c0b1..bea1ad49 100644
--- a/clients/cli/__tests__/stored-auth.test.ts
+++ b/clients/cli/__tests__/stored-auth.test.ts
@@ -873,3 +873,86 @@ describe("--wait-for-auth", () => {
     expect(result.stderr).toContain("positive number of seconds");
   });
 });
+
+/**
+ * The stored-token refresh path calls SDK discovery directly rather than
+ * through `InspectorClient.effectiveAuthFetch`, so it carries its own copy of
+ * the #2172 compatibility wrapper. This test injects no `discover`, because
+ * the wrapper lives in the *default* — injecting one would bypass exactly what
+ * is under test.
+ */
+describe("refreshStoredAuthToken discovery compatibility (#2172)", () => {
+  const REFRESHED = {
+    access_token: "refreshed-access-token",
+    token_type: "Bearer",
+    refresh_token: "rotated-refresh-token",
+    expires_in: 3600,
+  };
+
+  it("refreshes against an AS publishing RFC 8414 metadata at the OIDC path", async () => {
+    let base = "";
+    let rfc8414Probes = 0;
+    const server: Server = createServer((req, res) => {
+      const path = req.url ?? "";
+      if (path.startsWith("/.well-known/oauth-authorization-server")) {
+        rfc8414Probes += 1;
+        res.writeHead(404).end();
+        return;
+      }
+      // Plain OAuth 2.0: no jwks_uri, no subject_types_supported, no
+      // id_token_signing_alg_values_supported — the shape the SDK rejects when
+      // it finds it under this filename.
+      if (path === "/mcp/.well-known/openid-configuration") {
+        res.writeHead(200, { "content-type": "application/json" });
+        res.end(
+          JSON.stringify({
+            issuer: `${base}/mcp`,
+            authorization_endpoint: `${base}/oauth/authorize`,
+            token_endpoint: `${base}/oauth/token`,
+            response_types_supported: ["code"],
+            grant_types_supported: ["authorization_code", "refresh_token"],
+            token_endpoint_auth_methods_supported: ["client_secret_post"],
+          }),
+        );
+        return;
+      }
+      if (path === "/oauth/token") {
+        res.writeHead(200, { "content-type": "application/json" });
+        res.end(JSON.stringify(REFRESHED));
+        return;
+      }
+      res.writeHead(404).end();
+    });
+    await new Promise<void>((resolve) => {
+      server.listen(0, "127.0.0.1", resolve);
+    });
+    const addr = server.address();
+    base =
+      typeof addr === "object" && addr ? `http://127.0.0.1:${addr.port}` : "";
+    const serverUrl = `${base}/mcp`;
+    const fixture = writeOAuthFixture({
+      [serverUrl]: {
+        tokens: { refresh_token: "old-refresh", token_type: "Bearer" },
+        clientInformation: { client_id: "cid", client_secret: "sec" },
+      },
+    });
+    const warn = vi.spyOn(console, "warn").mockImplementation(() => {});
+    try {
+      await expect(refreshStoredAuthToken(serverUrl, fixture)).resolves.toBe(
+        "refreshed-access-token",
+      );
+      // The RFC 8414 location really was tried and really did 404, so the
+      // document could only have come from the OIDC path.
+      expect(rfc8414Probes).toBeGreaterThan(0);
+      expect(warn).toHaveBeenCalledWith(
+        expect.stringContaining("/mcp/.well-known/openid-configuration"),
+      );
+    } finally {
+      warn.mockRestore();
+      rmSync(dirname(fixture), { recursive: true, force: true });
+      await new Promise<void>((resolve) => {
+        server.close(() => resolve());
+      });
+    }
+  });
+});
diff --git a/clients/cli/src/cli.ts b/clients/cli/src/cli.ts
index af4bed16..6561e67b 100644
--- a/clients/cli/src/cli.ts
+++ b/clients/cli/src/cli.ts
@@ -52,6 +52,7 @@ import {
   getAuthorizationServerUrl,
   getAuthorizationServerUrlCandidates,
 } from "@inspector/core/auth/discovery.js";
+import { withRfc8414OidcCompat } from "@inspector/core/auth/oidcDiscoveryCompat.js";
 import { writeStoreFile } from "@inspector/core/storage/store-io.js";
 import {
   refreshAuthorization,
@@ -329,7 +330,21 @@ export async function refreshStoredAuthToken(
   deps: RefreshStoredAuthDeps = {},
 ): Promise<string> {
   const refresh = deps.refresh ?? refreshAuthorization;
-  const discover = deps.discover ?? discoverAuthorizationServerMetadata;
+  // #2172: this path calls SDK discovery directly rather than through
+  // `InspectorClient.effectiveAuthFetch`, so it needs the same compatibility
+  // wrapper — otherwise a stored refresh token with no persisted
+  // `serverMetadata` still cannot refresh against an authorization server that
+  // publishes RFC 8414 metadata at the OIDC well-known path (Copilot).
+  const compatFetch = withRfc8414OidcCompat(fetch);
+  const discover: typeof discoverAuthorizationServerMetadata =
+    deps.discover ??
+    ((authorizationServerUrl, options) =>
+      discoverAuthorizationServerMetadata(authorizationServerUrl, {
+        ...options,
+        // A caller-supplied fetch is left alone — it is theirs to compose. The
+        // walker below passes no options, so in practice this wraps the global.
+        fetchFn: options?.fetchFn ?? compatFetch,
+      }));
 
   const snapshot = await readOAuthSnapshot(statePath);
   const servers = snapshot.servers as StoredServers;
diff --git a/clients/web/src/test/core/auth/oidcDiscoveryCompat.test.ts b/clients/web/src/test/core/auth/oidcDiscoveryCompat.test.ts
index 88ef8d20..87500e0c 100644
--- a/clients/web/src/test/core/auth/oidcDiscoveryCompat.test.ts
+++ b/clients/web/src/test/core/auth/oidcDiscoveryCompat.test.ts
@@ -75,6 +75,16 @@ describe("oidcDiscoveryCandidates", () => {
   it("returns nothing for an unparseable URL", () => {
     expect(oidcDiscoveryCandidates("not a url")).toEqual([]);
   });
+
+  it("does not claim a path that merely shares the well-known prefix", () => {
+    // A bare prefix match would treat this as a discovery request and replace
+    // its failed response with a document from a derived URL (Copilot).
+    expect(
+      oidcDiscoveryCandidates(
+        "https://as.example.com/.well-known/oauth-authorization-server-backup",
+      ),
+    ).toEqual([]);
+  });
 });
 
 describe("isRfc8414OnlyMetadata", () => {
diff --git a/core/auth/oidcDiscoveryCompat.ts b/core/auth/oidcDiscoveryCompat.ts
index 498749cc..b45d8afc 100644
--- a/core/auth/oidcDiscoveryCompat.ts
+++ b/core/auth/oidcDiscoveryCompat.ts
@@ -115,6 +115,13 @@ export function oidcDiscoveryCandidates(rfc8414Url: string): string[] {
   }
   if (!url.pathname.startsWith(RFC8414_WELL_KNOWN)) return [];
   const path = url.pathname.slice(RFC8414_WELL_KNOWN.length);
+  // A bare prefix match would also claim `/.well-known/oauth-authorization-server-backup`
+  // — a path this wrapper has no business rewriting, and one whose failed
+  // response it would replace with a document fetched from somewhere else
+  // entirely (Copilot). The SDK appends the authorization server's pathname,
+  // which always begins with `/`, so requiring the exact path or a `/`
+  // boundary is precisely the set it can emit.
+  if (path !== "" && !path.startsWith("/")) return [];
   // The authorization server had no path, so the SDK emitted a single OIDC
   // candidate at the origin.
   if (path === "") return [new URL(OIDC_WELL_KNOWN, url.origin).href];