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fix(engine): warm-up seek after session init to prevent parallel worker flash frames #633

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fix(engine): warm-up seek after session init to prevent parallel worker flash frames #633

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16 changes: 16 additions & 0 deletions packages/engine/src/services/frameCapture.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -426,6 +426,17 @@ export async function initializeSession(session: CaptureSession): Promise<void>
await initTransparentBackground(session.page);
}

// Warm-up seek: prime the page's render pipeline (WebGL transmission
// buffers, canvas compositing, etc.) before real frame capture begins.
// Without this, parallel workers whose first assigned frame is mid-
// animation can capture an uninitialized render state — typically a
// single flash frame with wrong 3D object orientation or missing
// transmission effects. Two seeks at different times ensure both the
// initial state and mid-animation state are primed.
await page.evaluate(`window.__hf?.seek?.(0)`);
await page.evaluate(`window.__hf?.seek?.(window.__hf?.duration * 0.5 || 0)`);
await page.evaluate(`window.__hf?.seek?.(0)`);

session.isInitialized = true;
return;
}
Expand Down Expand Up @@ -522,6 +533,11 @@ export async function initializeSession(session: CaptureSession): Promise<void>
await initTransparentBackground(session.page);
}

// Warm-up seek (same rationale as the screenshot-mode branch above).
await page.evaluate(`window.__hf?.seek?.(0)`);
await page.evaluate(`window.__hf?.seek?.(window.__hf?.duration * 0.5 || 0)`);
await page.evaluate(`window.__hf?.seek?.(0)`);

session.isInitialized = true;
}

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