diff --git a/packages/sdk/js/script/build.ts b/packages/sdk/js/script/build.ts
index 79e0879c9e14..95428209d4b5 100755
--- a/packages/sdk/js/script/build.ts
+++ b/packages/sdk/js/script/build.ts
@@ -112,6 +112,20 @@ if (sseTypesPatched === sseTypesSource) {
 }
 await Bun.write(sseTypesPath, sseTypesPatched)
 
+// Abort handlers cannot await ReadableStreamDefaultReader.cancel(), but the
+// returned promise can reject after the body stream has already errored.
+const sseClientPath = "./src/v2/gen/core/serverSentEvents.gen.ts"
+const sseClientFile = Bun.file(sseClientPath)
+const sseClientSource = await sseClientFile.text()
+const sseClientPatched = sseClientSource.replace(
+  "            reader.cancel()",
+  "            void reader.cancel().catch(() => {})",
+)
+if (sseClientPatched === sseClientSource) {
+  throw new Error(`SSE cancel patch did not apply; @hey-api/openapi-ts output may have changed (${sseClientPath})`)
+}
+await Bun.write(sseClientPath, sseClientPatched)
+
 await $`bun prettier --write src/gen`
 await $`bun prettier --write src/v2`
 await $`rm -rf dist`
diff --git a/packages/sdk/js/src/gen/core/serverSentEvents.gen.ts b/packages/sdk/js/src/gen/core/serverSentEvents.gen.ts
index ffc4f16dc1f3..a631612b0793 100644
--- a/packages/sdk/js/src/gen/core/serverSentEvents.gen.ts
+++ b/packages/sdk/js/src/gen/core/serverSentEvents.gen.ts
@@ -111,7 +111,7 @@ export const createSseClient = <TData = unknown>({
 
         const abortHandler = () => {
           try {
-            void reader.cancel()
+            void reader.cancel().catch(() => {})
           } catch {
             // noop
           }
diff --git a/packages/sdk/js/src/v2/gen/core/serverSentEvents.gen.ts b/packages/sdk/js/src/v2/gen/core/serverSentEvents.gen.ts
index 056a81259322..05e6dd371dba 100644
--- a/packages/sdk/js/src/v2/gen/core/serverSentEvents.gen.ts
+++ b/packages/sdk/js/src/v2/gen/core/serverSentEvents.gen.ts
@@ -138,7 +138,7 @@ export const createSseClient = <TData = unknown>({
 
         const abortHandler = () => {
           try {
-            reader.cancel()
+            void reader.cancel().catch(() => {})
           } catch {
             // noop
           }
diff --git a/packages/sdk/js/test/server-sent-events.test.ts b/packages/sdk/js/test/server-sent-events.test.ts
new file mode 100644
index 000000000000..55e109b05b84
--- /dev/null
+++ b/packages/sdk/js/test/server-sent-events.test.ts
@@ -0,0 +1,30 @@
+import { expect, test } from "bun:test"
+import { createSseClient } from "../src/v2/gen/core/serverSentEvents.gen"
+
+test("observes reader cancellation errors when an SSE request is aborted", async () => {
+  const abort = new AbortController()
+  const result = createSseClient({
+    fetch: async () =>
+      new Response(
+        new ReadableStream({
+          start: (controller) =>
+            abort.signal.addEventListener("abort", () =>
+              controller.error(new DOMException("The operation was aborted", "AbortError")),
+            ),
+        }),
+        { headers: { "content-type": "text/event-stream" } },
+      ),
+    method: "GET",
+    signal: abort.signal,
+    sseMaxRetryAttempts: 1,
+    url: "http://localhost/events",
+  })
+
+  const next = result.stream.next()
+  // Let the generator park in reader.read() before erroring the body stream.
+  await Bun.sleep(10)
+  abort.abort()
+  expect(await next).toEqual({ done: true, value: undefined })
+  // Give any unobserved cancellation rejection time to reach Bun's test runner.
+  await Bun.sleep(10)
+})