From 083f5f7be1ba61932033e6d0a818e02e753629b2 Mon Sep 17 00:00:00 2001
From: Charles Vien <charles.v@posthog.com>
Date: Tue, 30 Jun 2026 18:52:41 -0700
Subject: [PATCH] flush proxy ingest uploads sooner

---
 .../src/server/event-stream-sender.test.ts    | 43 +++++++++++++++++++
 .../agent/src/server/event-stream-sender.ts   |  5 ++-
 2 files changed, 47 insertions(+), 1 deletion(-)

diff --git a/packages/agent/src/server/event-stream-sender.test.ts b/packages/agent/src/server/event-stream-sender.test.ts
index c57825d31..37dfd1575 100644
--- a/packages/agent/src/server/event-stream-sender.test.ts
+++ b/packages/agent/src/server/event-stream-sender.test.ts
@@ -208,6 +208,49 @@ describe("TaskRunEventStreamSender", () => {
     expect(lastCall[0]).not.toContain("/api/projects/");
   });
 
+  it("uses a short stream window for agent-proxy ingest so buffered uploads commit live events", async () => {
+    vi.useFakeTimers();
+    try {
+      const requestBodies: string[] = [];
+      let activeStreamClosed = false;
+      const fetchMock = vi.fn(
+        async (_url: string | URL | Request, init?: RequestInit) => {
+          if (!init?.body || typeof init.body === "string") {
+            return responseForBody(await readRequestBody(init));
+          }
+
+          const body = await readRequestBody(init);
+          activeStreamClosed = true;
+          requestBodies.push(body);
+          return responseForBody(body);
+        },
+      );
+      vi.stubGlobal("fetch", fetchMock);
+
+      const sender = createSender({
+        eventIngestBaseUrl: "http://agent-proxy:8003/",
+      });
+
+      sender.enqueue({
+        type: "notification",
+        notification: { method: "first" },
+      });
+      await vi.advanceTimersByTimeAsync(0);
+
+      expect(fetchMock).toHaveBeenCalledTimes(2);
+      expect(activeStreamClosed).toBe(false);
+
+      await vi.advanceTimersByTimeAsync(1_000);
+
+      expect(activeStreamClosed).toBe(true);
+      expect(eventSequences(requestBodies[0])).toEqual([1]);
+
+      await sender.stop();
+    } finally {
+      vi.useRealTimers();
+    }
+  });
+
   it("keeps the active ingest request open across scheduled flushes", async () => {
     const requestBodies: string[] = [];
     let activeStreamClosed = false;
diff --git a/packages/agent/src/server/event-stream-sender.ts b/packages/agent/src/server/event-stream-sender.ts
index 5e254ded4..83985de02 100644
--- a/packages/agent/src/server/event-stream-sender.ts
+++ b/packages/agent/src/server/event-stream-sender.ts
@@ -56,6 +56,7 @@ const DEFAULT_RETRY_DELAY_MS = 1_000;
 const DEFAULT_REQUEST_TIMEOUT_MS = 10_000;
 const DEFAULT_STOP_TIMEOUT_MS = 30_000;
 const DEFAULT_STREAM_WINDOW_MS = 5 * 60 * 1_000;
+const DEFAULT_PROXY_STREAM_WINDOW_MS = 1_000;
 const STREAM_COMPLETE_CONTROL_TYPE = "_posthog/stream_complete";
 
 export class TaskRunEventStreamSender {
@@ -111,7 +112,9 @@ export class TaskRunEventStreamSender {
     this.requestTimeoutMs =
       config.requestTimeoutMs ?? DEFAULT_REQUEST_TIMEOUT_MS;
     this.stopTimeoutMs = config.stopTimeoutMs ?? DEFAULT_STOP_TIMEOUT_MS;
-    this.streamWindowMs = config.streamWindowMs ?? DEFAULT_STREAM_WINDOW_MS;
+    this.streamWindowMs =
+      config.streamWindowMs ??
+      (usingProxy ? DEFAULT_PROXY_STREAM_WINDOW_MS : DEFAULT_STREAM_WINDOW_MS);
     this.createStreamingUpload =
       config.createStreamingUpload ?? createNodeStreamingUpload;
   }