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fix(appkit): harden SSE response headers in setupHeaders #331

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Merged
MarioCadenas merged 3 commits into from
Apr 30, 2026
Merged

fix(appkit): harden SSE response headers in setupHeaders #331

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d88576e
fix(appkit): harden SSE response headers in setupHeaders
MarioCadenas Apr 30, 2026
7c56cb1
fix(appkit): remove sentinel write from setupHeaders
MarioCadenas Apr 30, 2026
0e818ad
fix(appkit): update tests and serving plugin to match new SSE headers
MarioCadenas Apr 30, 2026
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4 changes: 3 additions & 1 deletion packages/appkit/src/plugins/analytics/tests/analytics.integration.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -105,7 +105,9 @@ describe("Analytics Plugin Integration", () => {
);

expect(response.status).toBe(200);
expect(response.headers.get("Content-Type")).toBe("text/event-stream");
expect(response.headers.get("Content-Type")).toBe(
"text/event-stream; charset=utf-8",
);

const sseData = await parseSSEResponse(response);
expect(sseData.eventType).toBe("result");
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11 changes: 4 additions & 7 deletions packages/appkit/src/plugins/analytics/tests/analytics.test.ts
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Expand Up @@ -174,16 +174,13 @@ describe("Analytics Plugin", () => {

expect(mockRes.setHeader).toHaveBeenCalledWith(
"Content-Type",
"text/event-stream",
"text/event-stream; charset=utf-8",
);
expect(mockRes.setHeader).toHaveBeenCalledWith(
"Cache-Control",
"no-cache",
);
expect(mockRes.setHeader).toHaveBeenCalledWith(
"Connection",
"keep-alive",
"no-cache, no-transform",
);
expect(mockRes.setHeader).toHaveBeenCalledWith("X-Accel-Buffering", "no");

expect(mockRes.write).toHaveBeenCalledWith("event: result\n");
expect(mockRes.write).toHaveBeenCalledWith(
Expand Down Expand Up @@ -245,7 +242,7 @@ describe("Analytics Plugin", () => {

expect(mockRes.setHeader).toHaveBeenCalledWith(
"Content-Type",
"text/event-stream",
"text/event-stream; charset=utf-8",
);

expect(mockRes.write).toHaveBeenCalledWith("event: result\n");
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4 changes: 2 additions & 2 deletions packages/appkit/src/plugins/genie/tests/genie.test.ts
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Expand Up @@ -299,11 +299,11 @@ describe("Genie Plugin", () => {
// Verify SSE headers
expect(mockRes.setHeader).toHaveBeenCalledWith(
"Content-Type",
"text/event-stream",
"text/event-stream; charset=utf-8",
);
expect(mockRes.setHeader).toHaveBeenCalledWith(
"Cache-Control",
"no-cache",
"no-cache, no-transform",
);

// Verify SSE events are written
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6 changes: 3 additions & 3 deletions packages/appkit/src/plugins/serving/serving.ts
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Expand Up @@ -261,9 +261,9 @@ export class ServingPlugin extends Plugin {
return;
}

res.setHeader("Content-Type", "text/event-stream");
res.setHeader("Cache-Control", "no-cache");
res.setHeader("Content-Encoding", "none");
res.setHeader("Content-Type", "text/event-stream; charset=utf-8");
res.setHeader("Cache-Control", "no-cache, no-transform");
res.setHeader("X-Accel-Buffering", "no");
res.flushHeaders();

const nodeStream = Readable.fromWeb(
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7 changes: 5 additions & 2 deletions packages/appkit/src/plugins/serving/tests/serving.test.ts
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Expand Up @@ -286,9 +286,12 @@ describe("Serving Plugin", () => {

expect(res.setHeader).toHaveBeenCalledWith(
"Content-Type",
"text/event-stream",
"text/event-stream; charset=utf-8",
);
expect(res.setHeader).toHaveBeenCalledWith(
"Cache-Control",
"no-cache, no-transform",
);
expect(res.setHeader).toHaveBeenCalledWith("Cache-Control", "no-cache");
expect(mockStream).toHaveBeenCalledWith(
expect.anything(),
"test-endpoint",
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14 changes: 9 additions & 5 deletions packages/appkit/src/stream/sse-writer.ts
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Expand Up @@ -11,11 +11,15 @@ import { StreamValidator } from "./validator";
export class SSEWriter {
// setup SSE headers
setupHeaders(res: IAppResponse): void {
res.setHeader("Content-Type", "text/event-stream");
res.setHeader("Cache-Control", "no-cache");
res.setHeader("Connection", "keep-alive");
res.setHeader("Content-Encoding", "none");

res.setHeader("Content-Type", "text/event-stream; charset=utf-8");
res.setHeader("Cache-Control", "no-cache, no-transform");
// X-Accel-Buffering: no — disables nginx-style proxy response buffering
// for SSE (used by Cloudflare, AWS, GCP, and most corporate proxies).
res.setHeader("X-Accel-Buffering", "no");
// Intentionally NOT setting:
// - Connection: keep-alive (HTTP/2 forbids it; Node manages keep-alive)
// - Content-Encoding: none (invalid value; can trigger 502/RST in
// strict intermediaries)
res.flushHeaders?.();
}

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2 changes: 1 addition & 1 deletion packages/appkit/src/stream/tests/stream.test.ts
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Expand Up @@ -44,7 +44,7 @@ describe("StreamManager", () => {

expect(mockRes.setHeader).toHaveBeenCalledWith(
"Content-Type",
"text/event-stream",
"text/event-stream; charset=utf-8",
);
expect(events).toContain(
'data: {"type":"start","message":"Starting"}\n\n',
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