chore (provider-utils): use eventsource-parser library (vercel#6781)

## Background

The eventsource-parser library has performance optimizations that will
speed up stream processing. It was removed before because of performance
issues, but has since then improved.

## Summary

Replace event source stream processing with `eventsource-parser`
library.

Author: lgrammel

.changeset/gold-planes-cheer.md

@@ -0,0 +1,5 @@
+---
+'@ai-sdk/provider-utils': patch
+---
+
+chore (provider-utils): use eventsource-parser library

packages/ai/core/tool/mcp/mcp-sse-transport.ts

@@ -1,4 +1,4 @@
-import { createEventSourceParserStream } from '@ai-sdk/provider-utils';
+import { EventSourceParserStream } from '@ai-sdk/provider-utils';
 import { MCPClientError } from '../../../src/error/mcp-client-error';
 import { JSONRPCMessage, JSONRPCMessageSchema } from './json-rpc-message';
 import { MCPTransport } from './mcp-transport';
@@ -55,7 +55,7 @@ export class SseMCPTransport implements MCPTransport {
 
           const stream = response.body
             .pipeThrough(new TextDecoderStream())
-            .pipeThrough(createEventSourceParserStream());
+            .pipeThrough(new EventSourceParserStream());
 
           const reader = stream.getReader();
 

packages/provider-utils/package.json

@@ -41,7 +41,8 @@
   "dependencies": {
     "@ai-sdk/provider": "workspace:*",
     "@standard-schema/spec": "^1.0.0",
-    "zod-to-json-schema": "^3.24.1"
+    "zod-to-json-schema": "^3.24.1",
+    "eventsource-parser": "^3.0.2"
   },
   "devDependencies": {
     "@types/node": "20.17.24",

packages/provider-utils/src/event-source-parser-stream.test.ts

@@ -1,8 +1,6 @@
 export * from './combine-headers';
 export { convertAsyncIteratorToReadableStream } from './convert-async-iterator-to-readable-stream';
 export * from './delay';
-export { createEventSourceParserStream } from './event-source-parser-stream';
-export type { EventSourceChunk } from './event-source-parser-stream';
 export * from './extract-response-headers';
 export * from './fetch-function';
 export { createIdGenerator, generateId } from './generate-id';
@@ -30,4 +28,10 @@ export * from './validate-types';
 export * from './validator';
 export * from './without-trailing-slash';
 export { zodSchema } from './zod-schema';
+
+// re-exports
+export {
+  type EventSourceMessage,
+  EventSourceParserStream,
+} from 'eventsource-parser/stream';
 export * from '@standard-schema/spec';