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fix: isolate cursor telemetry samples per recording session #457

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Merged
siddharthvaddem merged 5 commits into from
Apr 28, 2026
Merged

fix: isolate cursor telemetry samples per recording session #457

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84ec5a7
fix: isolate cursor telemetry samples per recording session
Apr 16, 2026
fac0b40
fix: handle recording discard and write-failure in cursor telemetry b…
shaun0927 Apr 16, 2026
adc6105
docs: document cursor telemetry buffer API and surface drop events
shaun0927 Apr 21, 2026
96765e4
docs: correct cx/cy units and sanitize buffer option limits
shaun0927 Apr 21, 2026
3b9b419
fix: key cursor telemetry batches by recordingId for safe discard
shaun0927 Apr 28, 2026
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3 changes: 2 additions & 1 deletion electron/electron-env.d.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -63,7 +63,8 @@ interface Window {
message?: string;
error?: string;
}>;
setRecordingState: (recording: boolean) => Promise<void>;
setRecordingState: (recording: boolean, recordingId?: number) => Promise<void>;
discardCursorTelemetry: (recordingId: number) => Promise<void>;
getCursorTelemetry: (videoPath?: string) => Promise<{
success: boolean;
samples: CursorTelemetryPoint[];
Expand Down
61 changes: 36 additions & 25 deletions electron/ipc/handlers.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -11,6 +11,10 @@ import {
shell,
systemPreferences,
} from "electron";
import {
type CursorTelemetryPoint,
createCursorTelemetryBuffer,
} from "../../src/lib/cursorTelemetryBuffer";
import {
normalizeProjectMedia,
normalizeRecordingSession,
Expand Down Expand Up @@ -275,14 +279,23 @@ async function storeRecordedSessionFiles(payload: StoreRecordedSessionInput) {
currentProjectPath = null;

const telemetryPath = `${screenVideoPath}.cursor.json`;
if (pendingCursorSamples.length > 0) {
await fs.writeFile(
telemetryPath,
JSON.stringify({ version: CURSOR_TELEMETRY_VERSION, samples: pendingCursorSamples }, null, 2),
"utf-8",
);
const pendingBatch = cursorTelemetryBuffer.takeNextBatch();
if (pendingBatch && pendingBatch.samples.length > 0) {
try {
await fs.writeFile(
telemetryPath,
JSON.stringify(
{ version: CURSOR_TELEMETRY_VERSION, samples: pendingBatch.samples },
null,
2,
),
"utf-8",
);
} catch (err) {
cursorTelemetryBuffer.prependBatch(pendingBatch);
throw err;
}
}
pendingCursorSamples = [];

const sessionManifestPath = path.join(
RECORDINGS_DIR,
Expand All @@ -302,16 +315,11 @@ const CURSOR_TELEMETRY_VERSION = 1;
const CURSOR_SAMPLE_INTERVAL_MS = 100;
const MAX_CURSOR_SAMPLES = 60 * 60 * 10; // 1 hour @ 10Hz

interface CursorTelemetryPoint {
timeMs: number;
cx: number;
cy: number;
}

let cursorCaptureInterval: NodeJS.Timeout | null = null;
let cursorCaptureStartTimeMs = 0;
let activeCursorSamples: CursorTelemetryPoint[] = [];
let pendingCursorSamples: CursorTelemetryPoint[] = [];
const cursorTelemetryBuffer = createCursorTelemetryBuffer({
maxActiveSamples: MAX_CURSOR_SAMPLES,
});

function clamp(value: number, min: number, max: number) {
return Math.min(max, Math.max(min, value));
Expand All @@ -338,15 +346,11 @@ function sampleCursorPoint() {
const cx = clamp((cursor.x - bounds.x) / width, 0, 1);
const cy = clamp((cursor.y - bounds.y) / height, 0, 1);

activeCursorSamples.push({
cursorTelemetryBuffer.push({
timeMs: Math.max(0, Date.now() - cursorCaptureStartTimeMs),
cx,
cy,
});

if (activeCursorSamples.length > MAX_CURSOR_SAMPLES) {
activeCursorSamples.shift();
}
}

export function registerIpcHandlers(
Expand Down Expand Up @@ -531,18 +535,21 @@ export function registerIpcHandlers(
}
});

ipcMain.handle("set-recording-state", (_, recording: boolean) => {
ipcMain.handle("set-recording-state", (_, recording: boolean, recordingId?: number) => {
if (recording) {
stopCursorCapture();
activeCursorSamples = [];
pendingCursorSamples = [];
// The renderer is the source of truth for the recording id (it
// uses the same id as the saved fileName). Fall back to a
// timestamp only if the renderer didn't supply one, so the
// buffer always has a stable key per session.
const id = typeof recordingId === "number" ? recordingId : Date.now();
cursorTelemetryBuffer.startSession(id);
Comment on lines +545 to +546
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@coderabbitai coderabbitai Bot Apr 28, 2026

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⚠️ Potential issue | 🟡 Minor

Harden recordingId validation before starting a session.

Line 545 accepts any JS number, including NaN/Infinity. That can produce non-matchable or unstable batch keys. Use a finite positive integer guard before startSession, else fallback to Date.now().

🤖 Prompt for AI Agents 
Verify each finding against the current code and only fix it if needed.

In `@electron/ipc/handlers.ts` around lines 545 - 546, The code currently treats
any JS number as a valid recordingId before calling
cursorTelemetryBuffer.startSession; change the validation so that recordingId is
only accepted when it's a finite positive integer (use
Number.isFinite(recordingId) && Number.isInteger(recordingId) && recordingId >
0); otherwise compute id = Date.now() and then call
cursorTelemetryBuffer.startSession(id). Update the id assignment and use the
existing cursorTelemetryBuffer.startSession call (and any downstream logic that
relies on id) to ensure unstable values like NaN/Infinity are never passed.

cursorCaptureStartTimeMs = Date.now();
sampleCursorPoint();
cursorCaptureInterval = setInterval(sampleCursorPoint, CURSOR_SAMPLE_INTERVAL_MS);
} else {
stopCursorCapture();
pendingCursorSamples = [...activeCursorSamples];
activeCursorSamples = [];
cursorTelemetryBuffer.endSession();
}

const source = selectedSource || { name: "Screen" };
Expand All @@ -551,6 +558,10 @@ export function registerIpcHandlers(
}
});

ipcMain.handle("discard-cursor-telemetry", (_, recordingId: number) => {
cursorTelemetryBuffer.discardBatch(recordingId);
});

ipcMain.handle("get-cursor-telemetry", async (_, videoPath?: string) => {
const targetVideoPath = normalizeVideoSourcePath(
videoPath ?? currentRecordingSession?.screenVideoPath,
Expand Down
7 changes: 5 additions & 2 deletions electron/preload.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -47,12 +47,15 @@ contextBridge.exposeInMainWorld("electronAPI", {
getRecordedVideoPath: () => {
return ipcRenderer.invoke("get-recorded-video-path");
},
setRecordingState: (recording: boolean) => {
return ipcRenderer.invoke("set-recording-state", recording);
setRecordingState: (recording: boolean, recordingId?: number) => {
return ipcRenderer.invoke("set-recording-state", recording, recordingId);
},
getCursorTelemetry: (videoPath?: string) => {
return ipcRenderer.invoke("get-cursor-telemetry", videoPath);
},
discardCursorTelemetry: (recordingId: number) => {
return ipcRenderer.invoke("discard-cursor-telemetry", recordingId);
},
onStopRecordingFromTray: (callback: () => void) => {
const listener = () => callback();
ipcRenderer.on("stop-recording-from-tray", listener);
Expand Down
3 changes: 2 additions & 1 deletion src/hooks/useScreenRecorder.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -225,6 +225,7 @@ export function useScreenRecorder(): UseScreenRecorderReturn {
try {
const screenBlob = await activeScreenRecorder.recordedBlobPromise;
if (discardRecordingId.current === activeRecordingId) {
window.electronAPI?.discardCursorTelemetry(activeRecordingId);
return;
}
if (screenBlob.size === 0) {
Expand Down Expand Up @@ -553,7 +554,7 @@ export function useScreenRecorder(): UseScreenRecorderReturn {
setRecording(true);
setPaused(false);
setElapsedSeconds(0);
window.electronAPI?.setRecordingState(true);
window.electronAPI?.setRecordingState(true, recordingId.current);

const activeScreenRecorder = screenRecorder.current;
const activeWebcamRecorder = webcamRecorder.current;
Expand Down
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