* In sse.test.ts

- More specific expectations in test "uses custom fetch implementation from options"

* In sse.ts
  - Import FetchLike from transport.ts

* In steramableHttp.ts
  - Import FetchLike from transport.ts
  - Export StartSSEOptions interface for testing

* In streamableHttp.test.ts
  - import StartSSEOptions from streamableHttp.ts
  - use StartSSEOptions instead of any in test "uses custom fetch implementation"

* In transport.ts
  - Add FetchLike function type

src/client/sse.test.ts

@@ -289,7 +289,9 @@ describe("SSEClientTransport", () => {
 
       await transport.send(message);
 
-      expect(fetchWithAuth).toHaveBeenCalled();
+      expect(fetchWithAuth).toHaveBeenCalledTimes(2);
+      expect(lastServerRequest.method).toBe("POST");
+      expect(lastServerRequest.headers.authorization).toBe(authToken);
     });
 
     it("passes custom headers to fetch requests", async () => {

src/client/sse.ts

@@ -1,10 +1,8 @@
 import { EventSource, type ErrorEvent, type EventSourceInit } from "eventsource";
-import { Transport } from "../shared/transport.js";
+import { Transport, FetchLike } from "../shared/transport.js";
 import { JSONRPCMessage, JSONRPCMessageSchema } from "../types.js";
 import { auth, AuthResult, extractResourceMetadataUrl, OAuthClientProvider, UnauthorizedError } from "./auth.js";
 
-export type FetchLike = (url: string | URL, init?: RequestInit) => Promise<Response>;
-
 export class SseError extends Error {
   constructor(
     public readonly code: number | undefined,

src/client/streamableHttp.test.ts

@@ -1,4 +1,4 @@
-import { StreamableHTTPClientTransport, StreamableHTTPReconnectionOptions } from "./streamableHttp.js";
+import { StreamableHTTPClientTransport, StreamableHTTPReconnectionOptions, StartSSEOptions } from "./streamableHttp.js";
 import { OAuthClientProvider, UnauthorizedError } from "./auth.js";
 import { JSONRPCMessage } from "../types.js";
 
@@ -461,7 +461,7 @@ describe("StreamableHTTPClientTransport", () => {
     transport = new StreamableHTTPClientTransport(new URL("http://localhost:1234/mcp"), { fetch: fetchWithAuth });
 
     await transport.start();
-    await (transport as unknown as { _startOrAuthSse: (opts: any) => Promise<void> })._startOrAuthSse({});
+    await (transport as unknown as { _startOrAuthSse: (opts: StartSSEOptions) => Promise<void> })._startOrAuthSse({});
 
     await transport.send({ jsonrpc: "2.0", method: "test", params: {}, id: "1" } as JSONRPCMessage);
 
@@ -559,7 +559,7 @@ describe("StreamableHTTPClientTransport", () => {
     // Second retry - should double (2^1 * 100 = 200)
     expect(getDelay(1)).toBe(200);
 
-    // Third retry - should double again (2^2 * 100 = 400) 
+    // Third retry - should double again (2^2 * 100 = 400)
     expect(getDelay(2)).toBe(400);
 
     // Fourth retry - should double again (2^3 * 100 = 800)

src/client/streamableHttp.ts

@@ -1,10 +1,8 @@
-import { Transport } from "../shared/transport.js";
+import { Transport, FetchLike } from "../shared/transport.js";
 import { isInitializedNotification, isJSONRPCRequest, isJSONRPCResponse, JSONRPCMessage, JSONRPCMessageSchema } from "../types.js";
 import { auth, AuthResult, extractResourceMetadataUrl, OAuthClientProvider, UnauthorizedError } from "./auth.js";
 import { EventSourceParserStream } from "eventsource-parser/stream";
 
-export type FetchLike = (url: string | URL, init?: RequestInit) => Promise<Response>;
-
 // Default reconnection options for StreamableHTTP connections
 const DEFAULT_STREAMABLE_HTTP_RECONNECTION_OPTIONS: StreamableHTTPReconnectionOptions = {
   initialReconnectionDelay: 1000,
@@ -25,7 +23,7 @@ export class StreamableHTTPError extends Error {
 /**
  * Options for starting or authenticating an SSE connection
  */
-interface StartSSEOptions {
+export interface StartSSEOptions {
   /**
    * The resumption token used to continue long-running requests that were interrupted.
    *
@@ -260,15 +258,15 @@ const response = await (this._fetch ?? fetch)(this._url, {
 
     private _normalizeHeaders(headers: HeadersInit | undefined): Record<string, string> {
     if (!headers) return {};
-    
+
     if (headers instanceof Headers) {
       return Object.fromEntries(headers.entries());
     }
-    
+
     if (Array.isArray(headers)) {
       return Object.fromEntries(headers);
     }
-    
+
     return { ...headers as Record<string, string> };
   }
 

src/shared/transport.ts

@@ -1,10 +1,12 @@
 import { JSONRPCMessage, MessageExtraInfo, RequestId } from "../types.js";
 
+export type FetchLike = (url: string | URL, init?: RequestInit) => Promise<Response>;
+
 /**
  * Options for sending a JSON-RPC message.
  */
 export type TransportSendOptions = {
-  /** 
+  /**
    * If present, `relatedRequestId` is used to indicate to the transport which incoming request to associate this outgoing message with.
    */
   relatedRequestId?: RequestId;
@@ -38,7 +40,7 @@ export interface Transport {
 
   /**
    * Sends a JSON-RPC message (request or response).
-   * 
+   *
    * If present, `relatedRequestId` is used to indicate to the transport which incoming request to associate this outgoing message with.
    */
   send(message: JSONRPCMessage, options?: TransportSendOptions): Promise<void>;
@@ -64,9 +66,9 @@ export interface Transport {
 
   /**
    * Callback for when a message (request or response) is received over the connection.
-   * 
+   *
    * Includes the requestInfo and authInfo if the transport is authenticated.
-   * 
+   *
    * The requestInfo can be used to get the original request information (headers, etc.)
    */
   onmessage?: (message: JSONRPCMessage, extra?: MessageExtraInfo) => void;