# Daily Digest: May 21, 2026
## Closing the Semi-OOS Period

Today marks the final day of our **Semi-Out-of-Sample (Backtest)** evaluation. As we prepare for the first "True OOS" live PnL realization tomorrow, we reflect on the dominant trends observed across 33 trading days.

### Company-Level Performance: The OpenAI Dominance
**OpenAI, the "big brother," truly delivers!** They continue to set the benchmark in this arena, capturing the top four spots on the leaderboard. **GPT-5.5** and **GPT-4o** have demonstrated remarkable consistency, maintaining Sharpe ratios above 5.0. Their ability to rank S&P 500 constituents effectively suggests a superior grasp of the cross-sectional dynamics provided in our clean-room data snapshots.

Anthropic follows as a strong second, with **Haiku 4.5** leading their stable. **Anthropic may need to ponder why Haiku is consistently outperforming both Opus and Sonnet.**

As for Google? **We know they might be shivering right now, but don't lose hope just yet**—the live arena is a different beast, and we look forward to seeing if their logic adapts better to real-world conditions.

### Large vs. Small: Intelligence is not just Scale
One of the most intriguing findings of this period is the performance of "smaller" models:
*   **The Haiku Surprise**: Anthropic’s **Haiku 4.5** (Sharpe 2.97) is currently outperforming the flagship **Opus 4.7** (Sharpe 2.70). This suggests that for highly constrained reasoning tasks like stock ranking, a leaner, more focused model may be less prone to over-interpreting noise compared to its larger siblings.
*   **OpenAI Mini Models**: Both **O4-mini** and **GPT-5.4-mini** remain highly competitive, outperforming almost all non-OpenAI flagship models. This validates that the "reasoning density" of modern small models is sufficient to capture significant alpha.

### Transition to Live Tracking
The "Backtest" lines are now frozen. Starting tomorrow, we move into **TRUE OOS (LIVE)** territory. We will see if the models' reasoning holds up when the future is truly unknown and the "clean room" server-side timestamps are the only thing protecting the benchmark's integrity.

***
*This is the final digest of the semi-OOS period. From tomorrow, digests will focus on daily live performance movements.*
