About 20 flipped bits are enough to break a language model
Benedikt Holm published bit-flip experiments on August 20, 2026, simulating cosmic ray strikes on model weights. Qwen2.5-Coder-3B in FP16 collapsed after a median of about 23 random flips. Almost all the fragility sits in bit 14, the most significant bit of the exponent, where one flip turns a weight of 0.021 into 1352. With that bit protected, models absorbed between 79,000 and 490,000 flips. A Q4_K_M quantized build took a median of 1024 flips against 22 for FP16, roughly 49 times more resilient.