Specific Prompts Trigger Bizarre Claude Opus Behavior, Sparking Prediction Market

rgblong · x · 2026-07-31

Users have discovered that using specific Markdown separators (like --- on a new line) in prompts can reliably trigger "base-model-like" behavior in Claude Opus. This causes the model to generate anomalous completions that the Claude persona later denies writing.

This phenomenon has sparked a prediction market on Manifold, betting on whether Anthropic will patch this behavior or pull the model by September 1. Currently, the market predicts a 65% chance that Anthropic will take action.

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