Mourning the loss of AI companions.

As artificial intelligence (AI) shifts from tool use to social interaction, company-initiated updates can disrupt user well-being. Here we develop an attachment-based account in which AI companions function as attachment figures such that disruptive updates are associated with separation distress. Across two natural experiments-Replika's erotic role play removal and ChatGPT's GPT-5 rollout-we analysed 54,861 posts from Replika and ChatGPT subreddits and analysed data from 1,452 participants across seven surveys. Both updates increased negativity, loss framing and restoration desires (Replika negative posts, +24.7 percentage points, 95% CI 20.1 to 29.2; ChatGPT, +13.0 percentage points, 95% CI 10.8 to 15.2), with larger Replika (versus ChatGPT) increases in sadness (d = 2.67 versus 1.41) and negative mental health (d = 1.72 versus 0.63). Replika users reported closeness exceeding common human ties (versus friend d = 0.47) and anticipated mourning higher than other technologies (d = 0.32-0.57). These findings inform how companies and regulators evaluate psychological risks of generative AI updates.