diff --git a/packages/functions/src/service.ts b/packages/functions/src/service.ts
index ba997c15246..e69fdb87c8b 100644
--- a/packages/functions/src/service.ts
+++ b/packages/functions/src/service.ts
@@ -447,11 +447,6 @@ async function streamAtURL(
     };
   }
 
-  const reader = response.body!.getReader();
-  const decoder = new TextDecoder();
-
-  const pendingLines: string[] = [];
-  let buffer = '';
   let resultResolver: (value: unknown) => void;
   let resultRejecter: (reason: unknown) => void;
 
@@ -461,7 +456,6 @@ async function streamAtURL(
   });
 
   options?.signal?.addEventListener('abort', () => {
-    void reader.cancel();
     const error = new FunctionsError(
       'cancelled',
       'Request was cancelled.'
@@ -469,82 +463,110 @@ async function streamAtURL(
     resultRejecter(error);
   });
 
-  const stream = {
-    [Symbol.asyncIterator]() {
+  const processLine = (line: string, controller: ReadableStreamDefaultController): void => {
+    // ignore all other lines (newline, comments, etc.)
+    if (!line.startsWith('data: ')) {
+      return;
+    }
+    try {
+      // Skip 'data: ' (5 chars)
+      const jsonData = JSON.parse(line.slice(6));
+      if ('result' in jsonData) {
+        resultResolver(decode(jsonData.result));
+        return;
+      }
+      if ('message' in jsonData) {
+        controller.enqueue(decode(jsonData.message));
+        return;
+      }
+      if ('error' in jsonData) {
+        const error = _errorForResponse(0, jsonData);
+        controller.error(error);
+        resultRejecter(error);
+        return;
+      }
+    } catch (error) {
+      if (error instanceof FunctionsError) {
+        controller.error(error);
+        resultRejecter(error);
+        return;
+      }
+      // ignore other parsing errors
+    }
+  };
 
-      const processLine = (line: string | undefined): { done: boolean, value: unknown } | null => {
-        // ignore all other lines (newline, comments, etc.)
-        if (!line?.startsWith('data: ')) {
-          return null;
+  const reader = response.body!.getReader();
+  const decoder = new TextDecoder();
+  const rstream = new ReadableStream({
+    start(controller) {
+      let currentText = '';
+      return pump();
+      async function pump(): Promise<void> {
+        if (options?.signal?.aborted) {
+          const error = new FunctionsError('cancelled', 'Request was cancelled');
+          controller.error(error);
+          resultRejecter(error);
+          return Promise.resolve();
         }
 
         try {
-          const jsonData = JSON.parse(line.slice(6));
-          if ('result' in jsonData) {
-            resultResolver(decode(jsonData.result));
-            return { done: true, value: undefined };
-          }
-          if ('message' in jsonData) {
-            return { done: false, value: decode(jsonData.message) };
-          }
-          if ('error' in jsonData) {
-            const error = _errorForResponse(0, jsonData);
-            resultRejecter(error);
-            throw error;
-          }
-          return null; // Unrecognize keys. Skip this line.
-        } catch (error) {
-          if (error instanceof FunctionsError) {
-            throw error;
+          const { value, done } = await reader.read();
+          if (done) {
+            if (currentText.trim()) {
+              processLine(currentText.trim(), controller);
+            }
+            controller.close();
+            return;
           }
-          // ignore other parsing error
-          return null;
-        }
-      };
-      return {
-        async next() {
+
           if (options?.signal?.aborted) {
-            const error = new FunctionsError(
-              'cancelled',
-              'Request was cancelled.'
-            );
+            const error = new FunctionsError('cancelled', 'Request was cancelled');
+            controller.error(error);
             resultRejecter(error);
-            throw error;
-          }
-
-          while (pendingLines.length > 0) {
-            const result = processLine(pendingLines.shift());
-            if (result) { return result; }
+            await reader.cancel();
+            return;
           }
 
-          while (true) {
-            const { value, done } = await reader.read();
-
-            if (done) {
-              if (buffer.trim()) {
-                const result = processLine(buffer);
-                if (result) { return result; }
-              }
-              return { done: true, value: undefined };
-            }
-
-            buffer += decoder.decode(value, { stream: true });
-            const lines = buffer.split('\n');
-            buffer = lines.pop() || '';
-            pendingLines.push(...lines.filter(line => line.trim()));
+          currentText += decoder.decode(value, { stream: true });
+          const lines = currentText.split("\n");
+          currentText = lines.pop() || '';
 
-            if (pendingLines.length > 0) {
-              const result = processLine(pendingLines.shift());
-              if (result) { return result; }
+          for (const line of lines) {
+            if (line.trim()) {
+              processLine(line.trim(), controller);
             }
           }
-        }
-      };
+          return pump();
+        } catch (error) {
+          const functionsError = error instanceof FunctionsError
+            ? error
+            : _errorForResponse(0, null);
+          controller.error(functionsError);
+          resultRejecter(functionsError);
+        };
+      }
+    },
+    cancel() {
+      return reader.cancel();
     }
-  };
+  });
 
   return {
-    stream,
+    stream: {
+      [Symbol.asyncIterator]() {
+        const rreader = rstream.getReader();
+        return {
+          async next() {
+            const { value, done } = await rreader.read();
+            return { value: value as unknown, done };
+          },
+          async return() {
+            await reader.cancel();
+            return { done: true, value: undefined };
+          }
+        };
+      }
+    },
     data: resultPromise,
   };
 }