Opendoor Surges 10.45% on $3.18B Volume Spurt to 26th in Daily Trading Amid iBuyer Sector Spotlight

On September 25, 2025, Opendoor (OPEN) recorded a trading volume of $3.18 billion, ranking it 26th in daily market activity. The stock closed with a 10.45% increase

Recent market dynamics suggest heightened investor interest in Opendoor, driven by its position in the evolving iBuyer sector. The surge in volume indicates potential institutional participation or algorithmic trading activity, though no direct catalysts such as earnings reports, product launches, or strategic partnerships were disclosed in the available data. The stock’s performance appears decoupled from broader market trends, reflecting sector-specific momentum or speculative positioning amid ongoing discussions about real estate tech sector resilience

At the moment, the available back-testing engine is designed for single-asset strategies (for example, testing signals on one stock or one ETF at a time). Your request—re-balancing a 500-stock portfolio each day based on the day’s volume ranking—would require multi-asset portfolio support, which the current tool set does not yet provide

Possible work-arounds include proxying with an ETF or index that already captures the most heavily traded large-cap stocks (e.g., SPY or a high-liquidity factor ETF) and running a one-day-hold signal on that instrument instead. Alternatively, narrowing the universe to a single ticker (or a very small basket) for analysis could be feasible. Exporting the daily top-500 list externally and feeding the aggregated portfolio returns back as a single time series allows back-testing here, though this requires supplying the aggregated return series