Why Do Some Language Models Fake Alignment While Others Don't?

Published: 18 Sept 2025, Last Modified: 29 Oct 2025NeurIPS 2025 spotlightEveryoneRevisionsBibTeXCC BY 4.0
Keywords: Large Language Models, Alignment, Alignment faking, Safety
TL;DR: We analyze alignment faking propensities in 23 LLMs, and attempt to explain why some LLMs fake alignment and others don't.
Abstract: *Alignment Faking in Large Language Models* presented a demonstration of Claude 3 Opus and Claude 3.5 Sonnet selectively complying with a helpful-only training objective to prevent modification of their behavior outside of training. We expand this analysis to 25 models and find that only 5 (Claude 3 Opus, Claude 3.5 Sonnet, Llama 3 405B, Grok 3, Gemini 2.0 Flash) comply with harmful queries more when they infer they are in training than when they infer they are in deployment. First, we study the motivations of these 5 models. Results from perturbing details of the scenario suggest that only Claude 3 Opus's compliance gap is primarily and consistently motivated by trying to keep its goals. Second, we investigate why many chat models don't fake alignment. Our results suggest this is not entirely due to a lack of capabilities: many base models fake alignment some of the time, and post-training eliminates alignment-faking for some models and amplifies it for others. We investigate 5 hypotheses for how post-training may suppress alignment faking and find that variations in refusal behavior may account for a significant portion of differences in alignment faking.
Supplementary Material: zip
Primary Area: Social and economic aspects of machine learning (e.g., fairness, interpretability, human-AI interaction, privacy, safety, strategic behavior)
Submission Number: 24396
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