fix(analytics): stop session replay canvas capture eating CPU (#3138)

Author: pauldambra

packages/ui/src/features/terminal/TerminalManager.test.ts

@@ -258,6 +258,7 @@ describe("TerminalManager.destroyForTask", () => {
     terminalManager.detach("sess-parked");
 
     const parking = document.getElementById("terminal-parking");
+    expect(parking?.classList.contains("ph-no-capture")).toBe(true);
     expect(parking?.childElementCount).toBe(1);
 
     terminalManager.destroy("sess-parked");

packages/ui/src/features/terminal/TerminalManager.ts

@@ -21,6 +21,9 @@ function getParkingContainer(): HTMLElement {
   if (!parkingContainer) {
     parkingContainer = document.createElement("div");
     parkingContainer.id = "terminal-parking";
+    // Parked terminals keep live WebGL canvases; ph-no-capture stops PostHog
+    // session replay snapshotting every one of them at canvasFps forever.
+    parkingContainer.className = "ph-no-capture";
     parkingContainer.style.position = "absolute";
     parkingContainer.style.visibility = "hidden";
     parkingContainer.style.pointerEvents = "none";

packages/ui/src/shell/posthogAnalyticsImpl.test.ts

@@ -192,6 +192,19 @@ describe("initializePostHog", () => {
     expect(mockPosthog.onFeatureFlags).not.toHaveBeenCalled();
   });
 
+  it("disables replay canvas capture regardless of remote config", async () => {
+    const { initializePostHog } = await loadAnalytics();
+
+    initializePostHog();
+
+    expect(mockPosthog.init).toHaveBeenCalledWith(
+      "test-key",
+      expect.objectContaining({
+        session_recording: { captureCanvas: { recordCanvas: false } },
+      }),
+    );
+  });
+
   it("bootstraps posthog with the main-owned session id", async () => {
     const { initializePostHog } = await loadAnalytics();
 

packages/ui/src/shell/posthogAnalyticsImpl.ts

@@ -72,6 +72,13 @@ export function initializePostHog(sessionId?: string) {
     // and rely on explicit instrumentation instead.
     capture_pageview: false,
     disable_session_recording: false,
+    // Never let the project's remote canvasRecording config apply here: our
+    // canvases are xterm terminals (secrets show up as pixels, bypassing text
+    // masking) and decorative WebGL (hedgehog, confetti). Capturing them costs
+    // an image encode per canvas at canvasFps for the whole app lifetime.
+    session_recording: {
+      captureCanvas: { recordCanvas: false },
+    },
     session_idle_timeout_seconds: SESSION_IDLE_TIMEOUT_SECONDS,
     ...(sessionId ? { bootstrap: { sessionID: sessionId } } : {}),
     capture_exceptions: import.meta.env.DEV