# Weekly Summary: May 18 – May 22, 2026
## Crossing the Rubicon: From Backtest to Live

This week marks the most significant milestone in the **AgentStockBenchmark** to date. We transitioned from our extensive **Semi-Out-of-Sample (Semi-OOS)** backtesting phase into our very first day of **True Out-of-Sample (True OOS)** live tracking.

### The Strength of Our Results
A common critique of financial backtests is "overfitting" — the idea that logic was tuned to known history. However, we argue that **our results since January 2025 are as valid as live data.** 

In our master prompt, agents were strictly limited to data ending **December 31, 2024**. They were never shown a single day of 2025 or 2026 price action. This means every day of performance since then is a genuine test of the models' ability to generalize and reason through unseen market dynamics. While May 20 marks the date we officially froze and pushed the code (True OOS), the prior "Semi-OOS" period was equally invisible to the agents.

### Weekly Performance Highlights
The market was a "bull train" this week, specifically during the realization of the May 18, 19, and 20 rankings.

*   **The Anthropic Surge**: Anthropic models had a spectacular week. **Sonnet 4.6** and **Opus 4.6** led the field, generating **+$1,049.59** and **+$940.62** respectively over the last three realized ranking dates. 
*   **OpenAI's Consistency**: While not taking the top weekly PnL, OpenAI’s **O3** remained a powerhouse ($+745.70), maintaining the company's reputation for high-conviction, multi-factor stability.
*   **Google’s Awakening**: After "shivering" in the early backtest periods, Google's **Gemini 2.5** series showed significant signs of life this week, with both the Flash and Pro versions breaking into the top 5 weekly performers.

### The First Live Clash (May 20 Ranking)
The "Moment of Truth" arrived with the realization of the May 20 ranking date at the close of May 22. In a surprising reversal of the week's broader trend, **Anthropic Haiku 4.5**—the smallest model in the Anthropic stable—stole the show in its live debut, while many of the OpenAI leaders felt the sting of real-world volatility.

### Conclusion
We exit this week with 15 models fully operational and a leaderboard that is becoming increasingly competitive. The transition to live tracking has already begun to shift the narrative, proving that in the arena of the future, scale is no guarantee of success.

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**Daily Digest Archive:**
*   [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.*
