fix(client): accept larger SSE events (#36442)

packages/client/src/promise/generated/client-error.ts

@@ -1,4 +1,9 @@
-export type ClientErrorReason = "Transport" | "UnexpectedStatus" | "UnsupportedContentType" | "MalformedResponse"
+export type ClientErrorReason =
+  | "Transport"
+  | "UnexpectedStatus"
+  | "UnsupportedContentType"
+  | "MalformedResponse"
+  | "SseEventTooLarge"
 
 export class ClientError extends Error {
   override readonly name = "ClientError"

packages/client/src/promise/generated/client.ts

@@ -213,6 +213,8 @@ interface RequestDescriptor {
   readonly binary?: true
 }
 
+const maxSseEventBytes = 16 * 1024 * 1024
+
 export function make(options: ClientOptions) {
   const fetch = options.fetch ?? globalThis.fetch
 
@@ -289,7 +291,7 @@ export function make(options: ClientOptions) {
             throw new ClientError("Transport", { cause })
           }
           buffer += decoder.decode(next.value, { stream: !next.done })
-          if (buffer.length > 1_048_576) throw new ClientError("MalformedResponse")
+          if (buffer.length > maxSseEventBytes) throw new ClientError("SseEventTooLarge")
           const trailingCarriageReturn = !next.done && buffer.endsWith("\r")
           if (trailingCarriageReturn) buffer = buffer.slice(0, -1)
           buffer = buffer.replaceAll("\r\n", "\n").replaceAll("\r", "\n")

packages/client/test/promise.test.ts

@@ -284,6 +284,43 @@ test("event.subscribe terminates on malformed Promise SSE data", async () => {
   })
 })
 
+test("event.subscribe accepts a fragmented SSE event below the size limit", async () => {
+  const event = { id: "evt_large", type: "test.large", data: { output: "x".repeat(12 * 1024 * 1024) } }
+  const encoded = new TextEncoder().encode(`data: ${JSON.stringify(event)}\n\n`)
+  const client = OpenCode.make({
+    baseUrl: "http://localhost:3000",
+    fetch: async () =>
+      new Response(
+        new ReadableStream({
+          start(controller) {
+            for (let offset = 0; offset < encoded.length; offset += 64 * 1024) {
+              controller.enqueue(encoded.slice(offset, offset + 64 * 1024))
+            }
+            controller.close()
+          },
+        }),
+        { headers: { "content-type": "text/event-stream" } },
+      ),
+  })
+
+  await expect(client.event.subscribe()[Symbol.asyncIterator]().next()).resolves.toEqual({ done: false, value: event })
+})
+
+test("event.subscribe rejects an SSE event above the size limit", async () => {
+  const client = OpenCode.make({
+    baseUrl: "http://localhost:3000",
+    fetch: async () =>
+      new Response(`data: ${JSON.stringify({ output: "x".repeat(16 * 1024 * 1024) })}`, {
+        headers: { "content-type": "text/event-stream" },
+      }),
+  })
+
+  await expect(client.event.subscribe()[Symbol.asyncIterator]().next()).rejects.toMatchObject({
+    name: "ClientError",
+    reason: "SseEventTooLarge",
+  })
+})
+
 test("session methods use the public HTTP contract", async () => {
   const requests: Array<{ url: string; init?: RequestInit }> = []
   const client = OpenCode.make({