fix: support CR line endings in SSE

src/client/stream.ts

@@ -10,11 +10,10 @@ export async function* parseSSE(response: Response): AsyncGenerator<ServerSentEv
 
   const decoder = new TextDecoder();
   let buffer = '';
+  let skipLeadingLF = false;
   let event: Partial<ServerSentEvent> = {};
 
-  const processLine = (rawLine: string): ServerSentEvent | undefined => {
-    const line = rawLine.endsWith('\r') ? rawLine.slice(0, -1) : rawLine;
-
+  const processLine = (line: string): ServerSentEvent | undefined => {
     if (line === '') {
       const completed = event.data !== undefined
         ? { data: event.data, event: event.event, id: event.id }
@@ -51,9 +50,18 @@ export async function* parseSSE(response: Response): AsyncGenerator<ServerSentEv
       const { done, value } = await reader.read();
       if (done) break;
 
-      buffer += decoder.decode(value, { stream: true });
+      let chunk = decoder.decode(value, { stream: true });
+      if (chunk.length === 0) continue;
+
+      // A CR completes its line immediately; swallow a paired LF in the next chunk.
+      if (skipLeadingLF) {
+        if (chunk.startsWith('\n')) chunk = chunk.slice(1);
+        skipLeadingLF = false;
+      }
+      buffer += chunk;
+      skipLeadingLF = buffer.endsWith('\r');
 
-      const lines = buffer.split('\n');
+      const lines = buffer.split(/\r\n|\r|\n/);
       buffer = lines.pop() || '';
 
       for (const line of lines) {

test/client/stream.test.ts

@@ -280,6 +280,75 @@ describe('parseSSE', () => {
     expect(events).toEqual([{ event: 'message', data: 'hello' }]);
   });
 
+  for (const newline of ['\n', '\r\n', '\r']) {
+    it(`preserves events at every byte boundary with ${JSON.stringify(newline)} line endings`, async () => {
+      const bytes = new TextEncoder().encode([
+        ': keepalive', 'id: 7', 'event: message', 'data: 你好',
+        'data: world', '', 'data: second', '', '',
+      ].join(newline));
+
+      for (let boundary = 0; boundary <= bytes.length; boundary++) {
+        const body = new ReadableStream<Uint8Array>({
+          start(controller) {
+            controller.enqueue(bytes.slice(0, boundary));
+            controller.enqueue(new Uint8Array());
+            controller.enqueue(bytes.slice(boundary));
+            controller.close();
+          },
+        });
+
+        expect(await collectEvents(new Response(body))).toEqual([
+          { id: '7', event: 'message', data: '你好\nworld' },
+          { data: 'second' },
+        ]);
+      }
+    });
+  }
+
+  it('handles mixed line endings in byte-by-byte chunks', async () => {
+    const bytes = new TextEncoder().encode(
+      'event: message\rdata: 你好\r\ndata: world\n\rdata: second\r\n\r\n',
+    );
+    const body = new ReadableStream<Uint8Array>({
+      start(controller) {
+        for (const byte of bytes) controller.enqueue(new Uint8Array([byte]));
+        controller.close();
+      },
+    });
+
+    expect(await collectEvents(new Response(body))).toEqual([
+      { event: 'message', data: '你好\nworld' },
+      { data: 'second' },
+    ]);
+  });
+
+  it('dispatches a CR-terminated event before the stream closes', async () => {
+    let controller!: ReadableStreamDefaultController<Uint8Array>;
+    const body = new ReadableStream<Uint8Array>({
+      start(streamController) { controller = streamController; },
+    });
+    const response = new Response(body);
+    const iterator = parseSSE(response);
+    const next = iterator.next();
+    let timeout: ReturnType<typeof setTimeout> | undefined;
+    controller.enqueue(new TextEncoder().encode('data: hello\r\r'));
+
+    try {
+      expect(await Promise.race([
+        next,
+        new Promise<never>((_resolve, reject) => {
+          timeout = setTimeout(() => reject(new Error('event was not dispatched')), 1000);
+        }),
+      ])).toEqual({ value: { data: 'hello' }, done: false });
+    } finally {
+      clearTimeout(timeout);
+      controller.close();
+      await next;
+      await iterator.return(undefined);
+    }
+    expect(response.body?.locked).toBe(false);
+  });
+
   // -------------------------------------------------------------------------
   // Helpers
   // -------------------------------------------------------------------------