diff --git a/src/client/streamableHttp.test.ts b/src/client/streamableHttp.test.ts
index f748a2be..0b85da17 100644
--- a/src/client/streamableHttp.test.ts
+++ b/src/client/streamableHttp.test.ts
@@ -1,6 +1,7 @@
 import { StreamableHTTPClientTransport, StreamableHTTPReconnectionOptions } from "./streamableHttp.js";
-import { OAuthClientProvider, UnauthorizedError } from "./auth.js";
-import { JSONRPCMessage } from "../types.js";
+import { JSONRPCMessage, LATEST_PROTOCOL_VERSION } from "../types.js";
+import { OAuthClientProvider } from "./auth.js";
+import { OAuthTokens } from "src/shared/auth.js";
 
 
 describe("StreamableHTTPClientTransport", () => {
@@ -517,19 +518,117 @@ describe("StreamableHTTPClientTransport", () => {
       id: "test-id"
     };
 
+    const clientInfo = {
+      "issuer": "http://localhost:1234",
+      "authorization_endpoint": "http://localhost:1234/authorize",
+      "token_endpoint": "http://localhost:1234/token",
+      "revocation_endpoint": "http://localhost:1234/revoke",
+      "scopes_supported": [
+        'wow',
+      ],
+      "grant_types_supported": [
+        "authorization_code",
+        "refresh_token"
+      ],
+      "token_endpoint_auth_methods_supported": [
+        "client_secret_basic",
+        "client_secret_post"
+      ],
+      "code_challenge_methods_supported": [
+        "S256"
+      ],
+      "registration_endpoint": "http://localhost:1234/register",
+      "response_types_supported": [
+        "code"
+      ],
+      "response_modes_supported": [
+        "query",
+        "fragment"
+      ]
+    };
+
     (global.fetch as jest.Mock)
-      .mockResolvedValueOnce({
-        ok: false,
+      .mockResolvedValueOnce(new Response("{}", {
         status: 401,
-        statusText: "Unauthorized",
         headers: new Headers()
+      }))
+      .mockImplementationOnce(async (url: URL | string, _init?: RequestInit) => {
+        expect((url as URL).pathname).toBe('/.well-known/oauth-authorization-server')
+        return new Response(JSON.stringify(clientInfo), {
+          status: 200,
+          headers: new Headers({ 'content-type': 'application/json' })
+        })
       })
-      .mockResolvedValue({
-        ok: false,
-        status: 404
-      });
+      .mockImplementationOnce(async (url: URL | string, _init?: RequestInit) => {
+        expect((url as URL).pathname).toBe('/.well-known/oauth-authorization-server')
+        return new Response(JSON.stringify(clientInfo), {
+          status: 200,
+          headers: new Headers({ 'content-type': 'application/json' })
+        })
+      })
+      .mockImplementationOnce(async (url: URL | string, init?: RequestInit) => {
+        expect(String(url)).toBe(clientInfo.token_endpoint)
+        expect(init).toBeDefined()
+        expect(init!.body).toBeDefined()
+        expect(new URLSearchParams(init!.body! as string).get('code')).toBe('any code')
+        return new Response(JSON.stringify({
+          "access_token": "anything",
+          "token_type": "Bearer",
+          "expires_at": new Date(Date.now() + 5000),
+          "scope": "anything",
+          "refresh_token": "something else"
+        }), {
+          status: 200,
+          headers: new Headers({ 'content-type': 'application/json' })
+        })
+      })
+      .mockImplementationOnce(async (url: URL | string, init?: RequestInit) => {
+        expect((url as URL).pathname).toBe('/mcp')
+        expect(init).toBeDefined()
+        expect(init!.body).toBeDefined()
+        expect(init!.headers).toBeDefined()
+        expect(new Headers(init!.headers).get('authorization')).toBe(`Bearer anything`)
+        const body = JSON.parse(init!.body! as string)
+        return new Response(JSON.stringify({
+          jsonrpc: '2.0',
+          id: body.id,
+          result: {
+            protocolVersion: LATEST_PROTOCOL_VERSION,
+            capabilities: {},
+            serverInfo: {
+              name: "test",
+              version: "1.0",
+            },
+          },
+        }), {
+          status: 200,
+          headers: new Headers({ 'content-type': 'application/json' })
+        })
+      })
+
 
-    await expect(transport.send(message)).rejects.toThrow(UnauthorizedError);
-    expect(mockAuthProvider.redirectToAuthorization.mock.calls).toHaveLength(1);
+    let tokens: OAuthTokens
+    mockAuthProvider.tokens = jest.fn(() => {
+      return tokens!
+    })
+    mockAuthProvider.saveTokens = jest.fn((t: OAuthTokens) => {
+      tokens = t
+    })
+
+    mockAuthProvider.redirectToAuthorization = jest.fn(async (redirectUrl: URL) => {
+      expect(redirectUrl.searchParams.get('response_type')).toBe('code')
+      expect(redirectUrl.searchParams.get('code_challenge_method')).toBe('S256')
+      expect(redirectUrl.searchParams.get('code_challenge')).toBe('test_challenge')
+      expect(redirectUrl.searchParams.get('client_id')).toBe('test-client-id')
+      expect(redirectUrl.searchParams.get('redirect_uri')).toBe('http://localhost/callback')
+      expect(redirectUrl.pathname).toBe('/authorize')
+
+      await transport.finishAuth('any code')
+    })
+
+    await transport.send(message)
+    expect(mockAuthProvider.redirectToAuthorization.mock.calls.length).toBe(1)
+    expect(mockAuthProvider.saveTokens.mock.calls.length).toBe(1)
+    expect(mockAuthProvider.tokens.mock.calls.length).toBe(3)
   });
 });
diff --git a/src/client/streamableHttp.ts b/src/client/streamableHttp.ts
index 3462b2ab..111ee705 100644
--- a/src/client/streamableHttp.ts
+++ b/src/client/streamableHttp.ts
@@ -401,10 +401,8 @@ export class StreamableHTTPClientTransport implements Transport {
 
       if (!response.ok) {
         if (response.status === 401 && this._authProvider) {
-          const result = await auth(this._authProvider, { serverUrl: this._url });
-          if (result !== "AUTHORIZED") {
-            throw new UnauthorizedError();
-          }
+          // Whether this is REDIRECT or AUTHORIZED, retry sending the message.
+          await auth(this._authProvider, { serverUrl: this._url });
 
           // Purposely _not_ awaited, so we don't call onerror twice
           return this.send(message);