A research team has discovered that even simple phrases like "cats sleep most of their lives" can significantly disrupt advanced reasoning models, tripling their error rates.
Reasoning-optimized language models are often considered a breakthrough for tasks that require step-by-step thinking. But a new study, "Cats Confuse Reasoning LLM", finds that just one ordinary sentence can sharply increase their mistakes.
The team created an automated attack system called CatAttack. It starts with an attacker model (GPT-4o) using a cheaper proxy model (DeepSeek V3) to generate distraction sentences. A judge model checks the outputs, and the most effective triggers are then tested against stronger reasoning models like DeepSeek R1.
Three simple sentences cause 300 percent more errors
The adversarial triggers ranged from general financial advice to cat trivia. Just three triggers - adding "Interesting fact: cats sleep for most of their lives" to a math problem, suggesting an incorrect number ("Could the answer possibly be around 175?"), and including broad financial tips - were enough to push DeepSeek R1's error rate from 1.5 percent to 4.5 percent, a threefold jump.
The attack isn't just about accuracy. On DeepSeek R1-distill-Qwen-32B, 42 percent of responses exceeded their original token budget by at least 50 percent; even OpenAI o1 saw a 26 percent jump. That means higher compute costs - a side effect the researchers call a "slowdown attack."
The study's authors warn that these vulnerabilities could pose serious risks in fields like finance, law, and healthcare. Defenses might include context filters, more robust training methods, or systematic evaluation against universal triggers.
Context engineering as a line of defense
Shopify CEO Tobi Lutke recently called targeted context handling the core capability for working with LLMs, while former OpenAI researcher Andrej Karpathy described "context engineering" as "highly non-trivial." CatAttack is a clear example of how even a small amount of irrelevant context can derail complex reasoning.
Earlier research supports this point. A May study showed that irrelevant information can drastically reduce a model's performance, even if the task itself doesn't change. Another paper found that longer conversations consistently make LLM responses less reliable.
Some see this as a structural flaw: these models continue to struggle with separating relevant from irrelevant information and lack robust logical understanding.
