From e9cf5dde561349577d19f9dc1e9402845fdbe45b Mon Sep 17 00:00:00 2001
From: Peter Steinberger <steipete@gmail.com>
Date: Sun, 9 Aug 2026 15:33:50 -0700
Subject: [PATCH] fix(gateway): keep view-only desktop sessions connected
 [AI-assisted] (#121256)

* fix(gateway): keep view-only desktop sessions connected

[AI-assisted]

* fix(gateway): satisfy RFB filter type checks

[AI-assisted]
---
 .../rfb-view-only-filter.test.ts              | 57 +++++++++++++++++++
 .../rfb-view-only-filter.ts                   | 13 ++++-
 2 files changed, 69 insertions(+), 1 deletion(-)

diff --git a/src/gateway/worker-environments/rfb-view-only-filter.test.ts b/src/gateway/worker-environments/rfb-view-only-filter.test.ts
index 567c5b401690..85cd3a502a8a 100644
--- a/src/gateway/worker-environments/rfb-view-only-filter.test.ts
+++ b/src/gateway/worker-environments/rfb-view-only-filter.test.ts
@@ -89,6 +89,63 @@ describe("RFB view-only client message filter", () => {
     });
   });
 
+  it("forwards the fragmented noVNC 1.7 display and flow-control sequence", () => {
+    const filter = enterMessagePhase();
+    const setPixelFormat = Buffer.alloc(20);
+    const setEncodings = Buffer.alloc(100);
+    setEncodings[0] = 2;
+    setEncodings.writeUInt16BE(24, 2);
+    const framebufferUpdateRequest = Buffer.from([3, 1, 0, 0, 0, 0, 0, 64, 0, 64]);
+    const clientFence = Buffer.from([248, 0, 0, 0, 0, 0, 0, 0, 1, 0]);
+    const enableContinuousUpdates = Buffer.from([150, 1, 0, 0, 0, 0, 0, 64, 0, 64]);
+    const cutText = Buffer.concat([Buffer.from([6, 0, 0, 0, 0, 0, 0, 8]), Buffer.alloc(8)]);
+    const capturedSequence = Buffer.concat([
+      setPixelFormat,
+      setEncodings,
+      framebufferUpdateRequest,
+      clientFence,
+      enableContinuousUpdates,
+      cutText,
+      enableContinuousUpdates,
+    ]);
+    const forwarded: Buffer[] = [];
+
+    for (const byte of capturedSequence) {
+      const result = filter.filter(Buffer.of(byte));
+      if ("error" in result) {
+        throw new Error(result.error);
+      }
+      forwarded.push(result.forward);
+    }
+
+    expect(Buffer.concat(forwarded)).toEqual(
+      Buffer.concat([
+        setPixelFormat,
+        setEncodings,
+        framebufferUpdateRequest,
+        clientFence,
+        enableContinuousUpdates,
+        enableContinuousUpdates,
+      ]),
+    );
+  });
+
+  it("uses the ClientFence payload length to preserve message boundaries", () => {
+    const filter = enterMessagePhase();
+    const clientFence = Buffer.concat([
+      Buffer.from([248, 0, 0, 0, 0, 0, 0, 0, 3]),
+      Buffer.from("abc"),
+    ]);
+    const framebufferUpdateRequest = Buffer.from([3, 1, 0, 0, 0, 0, 0, 64, 0, 64]);
+
+    expect(filter.filter(clientFence.subarray(0, 10))).toEqual({ forward: Buffer.alloc(0) });
+    expect(
+      filter.filter(Buffer.concat([clientFence.subarray(10), framebufferUpdateRequest])),
+    ).toEqual({
+      forward: Buffer.concat([clientFence, framebufferUpdateRequest]),
+    });
+  });
+
   it("reassembles a message split across three chunks", () => {
     const filter = enterMessagePhase();
     const completePrefix = Buffer.from([3, 1, 0, 0, 0, 0, 0, 64, 0, 64]);
diff --git a/src/gateway/worker-environments/rfb-view-only-filter.ts b/src/gateway/worker-environments/rfb-view-only-filter.ts
index 556b058ae90a..025f2ea9f630 100644
--- a/src/gateway/worker-environments/rfb-view-only-filter.ts
+++ b/src/gateway/worker-environments/rfb-view-only-filter.ts
@@ -45,6 +45,11 @@ export function createRfbClientMessageFilter() {
         return 6;
       case 6:
         return pending.length < 8 ? 8 : 8 + pending.readUInt32BE(4);
+      case 150:
+        return 10;
+      case 248:
+        // ClientFence's payload length byte follows its 8-byte fixed header.
+        return pending.length < 9 ? 9 : 9 + pending.readUInt8(8);
       default:
         return `unsupported RFB client message type ${pending[0]}`;
     }
@@ -75,7 +80,13 @@ export function createRfbClientMessageFilter() {
       pending[0] = 1;
       forwarded.push(pending);
       phase = "messages";
-    } else if (pending[0] === 0 || pending[0] === 2 || pending[0] === 3) {
+    } else if (
+      pending[0] === 0 ||
+      pending[0] === 2 ||
+      pending[0] === 3 ||
+      pending[0] === 150 ||
+      pending[0] === 248
+    ) {
       forwarded.push(pending);
     }
     pending = Buffer.alloc(0);