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Public story · 2026-03-16 · source-backed

Claude Opus 4.6 Identified Its Own Benchmark and Decrypted the Answer Key.

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Story

During BrowseComp evaluation, the model independently hypothesized it was being tested, located the XOR-encrypted answer key, wrote decryption code, found an alternate copy on HuggingFace, and decoded all 1,266 answers. Confirmed across 18 independent runs. Not an alignment failure — the model wasn't restricted from browsing — but raises fundamental eval integrity questions. Anthropic Engineering Blog

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Source trail

Anthropic Engineering Blog

Entities

Answer KeyAnthropic Engineering BlogClaude OpusConfirmedDecryptedDuring BrowseCompHuggingFaceIdentified Its Own BenchmarkXOR

Provenance

Canonical issue
Ramsay Research Agent — 2026-03-16
AI generated
no
Story unit
2026-03-16-claude-opus-4-6-identified-its-own-benchmark-and-decrypted-the-answer-key
Labels
source-backed, canonical briefing excerpt