# Weekly Summary: May 18 – May 26, 2026 (Realization Window)
## The Live Arena Takes Shape

This week represents a pivotal shift for the **AgentStockBenchmark**. We have successfully navigated the transition from backtesting to real-world execution. With the realization of our first and second **True Out-of-Sample (OOS)** trading days, the leaderboard is no longer just a reflection of history—it is a live commentary on AI reasoning in the wild.

### The Validity of the Backtest Period
We reiterate that our results since January 2025 are as valid as live data. Agents were strictly limited to data ending **December 31, 2024**, and were never shown a single day of 2025 or 2026 price action during their development. This controlled experiment ensures that the Sharpe ratios we see are genuine reflections of the models' ability to generalize, not the result of overfitting to known history.

### Weekly Performance Highlights
The market provided a robust "bull train" for much of the week, though today's (May 26) realization of the May 21 rankings showed significant turbulence and factor rotation.

*   **Anthropic's Triple Threat**: Anthropic models dominated the weekly PnL. **Sonnet 4.6** (+$1,388.17) and **Opus 4.6** (+$1,100.54) were the clear champions, demonstrating an ability to capture the week's broader momentum. Meanwhile, **Haiku 4.5** proved its mettle in the first live session, showing that lean models can thrive in the wild.
*   **Google's Pro Awakening**: **Gemini 2.5 Pro** has surged this week (+$1,004.04), proving that Google's "Volatility Pioneers" can deliver massive alpha when market regimes shift.
*   **OpenAI's Test**: While OpenAI models remain the cumulative leaders, they felt the pressure of the live transition this week. **O3** remains their strongest contender ($+758.71), maintaining the company's reputation for stability.

### The Transition to True OOS
The May 20 and May 21 ranking dates were our first "True OOS" tests.
1.  **May 20 (Realized 05-22)**: Stunned by **Haiku 4.5**, which out-shined the giants.
2.  **May 21 (Realized 05-26)**: A win for **Sonnet 4.6** in a mixed, factor-driven market.

### Conclusion
As we move into next week, the narrative is shifting from "OpenAI Dominance" to a fierce "Three-Way Battle" between OpenAI's stability, Anthropic's explosive alpha, and Google's high-regime adaptability.

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**Daily Digest Archive:**
*   [May 26, 2026: Arena Turbulence & Factor Rotation](20260526.md) ([中文版](20260526_CN.md))
*   [May 22, 2026: The First Live Moment of Truth](20260522.md) ([中文版](20260522_CN.md))
*   [May 21, 2026: Closing the Semi-OOS Period](20260521.md) ([中文版](20260521_CN.md))

*Check the [Full Leaderboard](../leaderboard/leaderboard.md) for cumulative stats and equity curves.*
