Claude Opus 4.6 Analyzes Buffett Letters to Pick Stocks Blindly

Experiment Setup: Extracting Buffett's Philosophy

A developer tested whether Claude Opus 4.6 could pick stocks better than Warren Buffett by analyzing 48 years of his shareholder letters (1977-2024, 561,849 words). The experiment used Claude Code as an orchestrator with subagents handling different pipeline stages to prevent information leakage.

In the first stage, Claude Code wrote a script to fetch the 48 letters, then extracted key investing principles from each. It identified 15 principles total, with 9 being quantitative enough to turn into a scoring rubric. These included ROE thresholds, debt-to-equity limits, margin of safety, and moat durability. Six parallel subagents each read different eras of letters for this extraction.

Blind Testing Architecture

The developer created a Claude Code setup with this structure:

buffett-analysis/
├── orchestrator # Main controller - runs full pipeline per ticker
├── skills/
│   ├── collect-financials # Pulls 10-K data, ratios, segment breakdowns
│   ├── anonymize-company # Strips names, tickers, brands → "Company A"
│   ├── moat-analysis # Scores durable competitive advantages
│   ├── management-quality # Evaluates capital allocation & incentives
│   ├── valuation-model # DCF + owner earnings + margin of safety
│   └── generate-verdict # Final buy/pass/watch recommendation
└── sub-agents/
    └── (spawned per company) # Blind analysis - no identity, just fundamentals

For the blind test, Opus anonymized 50 stocks by stripping all names, tickers, and sectors, leaving only anonymized identifiers like "Company Alpha" and "Company Bravo." The sample contained 20 actual Berkshire holdings, 15 value candidates, and 15 anti-Buffett controls (including GameStop, Rivian, Beyond Meat, and MicroStrategy).

Multiple subagents then scored all 50 companies using only the extracted rubric and anonymized financials, not applying Opus's own reasoning but strictly following the Buffett-derived principles.

Results and Findings

The Opus 4.6 analysis produced these results:

• 6 out of its top 10 picks were actual Berkshire holdings (60% overlap, completely blind)
• 13 out of 15 anti-Buffett controls landed in the bottom half and were properly rejected
• It ranked Berkshire Hathaway itself as the #7 most Buffett-like stock without knowing what it was

Top 10 picks were:

1. Alphabet (GOOGL)
2. Visa (V)
3. Moody's (MCO)
4. Coinbase (COIN)
5. Mastercard (MA)
6. Procter & Gamble (PG)
7. Berkshire Hathaway (BRK-B)
8. Coca-Cola (KO)
9. Apple (AAPL)
10. Texas Instruments (TXN)

An interesting failure occurred with Coinbase ranking 4th despite being intended as an anti-Buffett control (Buffett has previously called crypto "rat poison squared"). The analysis noted Coinbase had a 39% profit margin.

This experiment demonstrates how Claude Code with subagents can systematically extract and apply complex investment principles from large text corpora while maintaining blind testing protocols to reduce bias.