diff --git a/src/internal/parse.ts b/src/internal/parse.ts
index 39174399e..d7e01a02b 100644
--- a/src/internal/parse.ts
+++ b/src/internal/parse.ts
@@ -63,7 +63,16 @@ export async function defaultParseResponse<T>(
         return undefined as T;
       }
 
-      const json = await response.json();
+      const bodyText = await response.text();
+      if (!bodyText) {
+        // Some servers respond with an empty body and a JSON content-type but
+        // without a `content-length: 0` header (e.g. over HTTP/2 or with chunked
+        // transfer encoding). Treat this the same as an explicit `content-length: 0`
+        // instead of letting `JSON.parse` throw an opaque `SyntaxError`.
+        return undefined as T;
+      }
+
+      const json = JSON.parse(bodyText);
       return addRequestID(json as T, response);
     }
 
diff --git a/tests/index.test.ts b/tests/index.test.ts
index a5df13c0a..60a38347e 100644
--- a/tests/index.test.ts
+++ b/tests/index.test.ts
@@ -676,6 +676,56 @@ describe('default encoder', () => {
   });
 });
 
+describe('response parsing', () => {
+  test('handles an empty JSON body without a content-length header', async () => {
+    // Some servers (e.g. over HTTP/2 or with chunked transfer encoding) return an
+    // empty body with a JSON content-type but omit the `content-length` header.
+    // `new Response('')` reproduces this: an empty body with no `content-length`.
+    // This previously threw `SyntaxError: Unexpected end of JSON input`.
+    const testFetch = async (): Promise<Response> => {
+      const response = new Response('', { headers: { 'Content-Type': 'application/json' } });
+      expect(response.headers.get('content-length')).toBeNull();
+      return response;
+    };
+
+    const client = new OpenAI({ apiKey: 'My API Key', adminAPIKey: 'My Admin API Key', fetch: testFetch });
+
+    expect(await client.request({ path: '/foo', method: 'get' })).toBeUndefined();
+  });
+
+  test('handles an empty JSON body with an explicit content-length: 0 header', async () => {
+    const testFetch = async (): Promise<Response> =>
+      new Response('', { headers: { 'Content-Type': 'application/json', 'Content-Length': '0' } });
+
+    const client = new OpenAI({ apiKey: 'My API Key', adminAPIKey: 'My Admin API Key', fetch: testFetch });
+
+    expect(await client.request({ path: '/foo', method: 'get' })).toBeUndefined();
+  });
+
+  test('parses a non-empty JSON body', async () => {
+    const testFetch = async (): Promise<Response> =>
+      new Response(JSON.stringify({ a: 1 }), { headers: { 'Content-Type': 'application/json' } });
+
+    const client = new OpenAI({ apiKey: 'My API Key', adminAPIKey: 'My Admin API Key', fetch: testFetch });
+
+    expect(await client.request({ path: '/foo', method: 'get' })).toEqual({ a: 1 });
+  });
+
+  test('still throws on a malformed non-empty JSON body', async () => {
+    const testFetch = async (): Promise<Response> =>
+      new Response('{ not json', { headers: { 'Content-Type': 'application/json' } });
+
+    const client = new OpenAI({
+      apiKey: 'My API Key',
+      adminAPIKey: 'My Admin API Key',
+      maxRetries: 0,
+      fetch: testFetch,
+    });
+
+    await expect(client.request({ path: '/foo', method: 'get' })).rejects.toThrow();
+  });
+});
+
 describe('retries', () => {
   test('retry on timeout', async () => {
     let count = 0;