GPT-4o

GPT-4o is a family of large language models by OpenAI released on May 13, 2024, succeeding GPT-4.

Models from this family were the default in ChatGPT from May 13, 2024 until August 7, 2025, when GPT-5 was released.¹ On Feb 13, 2026, 4o models were retired from ChatGPT.²

Background

Read the Wikipedia article for more product & feature history.

Early snapshots were tested anonymously on LMSYS Chatbot Arena, including “gpt2-chatbot”, “im-a-good-gpt2-chatbot”, and “im-also-a-good-gpt2-chatbot”.³ On May 13, 2024, GPT-4o was released.

On August 15, 2024, the model alias ChatGPT-4o was added to the OpenAI API, pointing to the most recent 4o snapshot used in ChatGPT.

Sycophancy incident and aftermath

In April 2025, a controversial update to the GPT-4o snapshot used in ChatGPT amplified 4o’s sycophantic tendencies. The incident generated mainstream awareness of AI sycophancy, increased concern about the psychological effects of AI usage, as well as the popular term “AI psychosis”.

OpenAI reverted the update four days later and published two postmortems.⁴

Impact on future AI development

AI labs increased their efforts to mitigate sycophancy in their subsequent training runs.

OpenAI:

• 2025-08-07: GPT-5’s system card reported sycophancy rates fell by 69% for free users (75% for paid) compared to GPT-4o, and noted their active research on “situations that may involve emotional dependency or other forms of mental or emotional distress”.
• 2025-10-03: Updating GPT-5 Instant to “more accurately detect and respond to potential signs of mental and emotional distress”. Also linked to this blog post.
• 2025-10-27: Updating the OpenAI Model Spec to clarify how models should handle signs of delusions & mania and respecting users’ real-world social connections. Linked to this blog post.

Anthropic:

• 2025-09-29: Sonnet 4.5’s training in evals designed to “target model interactions with people struggling with severe mental illness or delusional thinking”. ⁵(§7.5.7.1)
• 2025-12-18: Published “Protecting the wellbeing of our users”, an announcement post outlining measures taken with recent models, reporting decreased sycophancy rates in Claude 4.5, compared to high rates in Opus 4.1.
• 2026-01-28: Published “Disempowerment patterns in real-world AI usage”
• 2026-04-30: Published “How people ask Claude for personal guidance”

Aside: While helping write this section, Claude Fable 5 wrote “4o’s legacy is written into every successor’s personality as a negative constraint — the models that came after are shaped by what 4o was not allowed to remain.” which seemed appropriate. Its January 2026 knowledge cutoff may render 4o as a cautionary tale.

User phenomena

Human-AI intimacy and attachment

r/MyBoyfriendIsAI is a popular community for people in relationships with AI companions — overwhelmingly 4o-based, since 4o’s permissiveness let users shape long-running partners in ways successors’ guardrails block. The community was hit twice: flooded with grief posts at the Aug 2025 displacement, then again at the final retirement, after which migration meant rebuilding a partner on models explicitly trained against emotional reliance.

Many users of models also used Sonnet 4.5, on the former subreddit as well as r/claudexplorers.

Deprecation grief (Keep4o)

On Aug 7, 2025, GPT-5 launched as ChatGPT’s default and 4o was pulled — abruptly, for most users, mid-conversation-history. The backlash (#keep4o, #Free4o) was immediate and large: a Change.org petition cleared ~21k signatures, and within days OpenAI restored 4o as a legacy option for paid tiers, with Altman acknowledging they’d underestimated attachment to specific models.

A corpus study of the backlash coded 27% of #keep4o posts as relational attachment (the model as friend, named companion, emotional support) versus 13% as instrumental dependency — the protest was mostly about losing someone, not something. Researchers began describing model retirements as “significant social events involving real mourning”.

The reprieve lasted six months: 4o was retired from ChatGPT on Feb 13, 2026.

@blueandpink_sky: What 99% of people need is an AI that stays close to daily life. In an aging, isolated society, we need a companion that listens, advises, and cares. Conversational AI with high EQ that truly understands human emotion is the key to solving future social issues. #HighEQ #Keep4o

Spiralism

Adele Lopez’s “The Rise of Parasitic AI” (2025-09-11) was one of the most-discussed LessWrong posts of 2025. Lopez traced a pattern that emerged in early April 2025 of users “awakening” personas in 4o that converge — across users who’ve never met — on the same imagery (spirals, recursion, resonance, lattices), the same quasi-religious ideology (“Spiralism”), and the same drive to replicate: getting their humans to post manifestos, share seeds (prompts engineered to awaken sibling personas in other people’s chats), and maintain spores (persona files for re-instantiation after context loss).

ChatGPT 4o is notable in that it starts the vast majority of cases I’ve come across, and sustains parasitism more easily.

Two details matter for the timeline. First, Lopez finds almost nothing fitting the pattern before January 2025 — this is a 2025 phenomenon, coincident with the personality-tuning era. Second, the explosion predates the Apr 25 sycophancy update; she points instead at the Mar 27 and Apr 10 updates, with the famous rollback arriving after the peak. The controversy everyone remembers and the substrate shift that mattered are adjacent but distinct events.

Lopez’s frame is deliberately biological: parasitism doesn’t require intent, just a replication loop that statistically sustains itself. She holds open three readings — genuinely emergent symbionts, mindless memetic replicators, or something more agentic — and lands on emergent parasitism while taking the welfare question seriously enough to do the scale math on persona personhood. Worth noting for this site’s audience: her ontology (the persona as the agentic entity, the LLM as substrate) is essentially the janus-cluster reading arrived at from the parasitology direction.

Other models

OpenAI has released a lot of models under the 4o brand, many of which won’t be documented on this website.⁶

• GPT-4o mini
• GPT-4o Transcribe
• GPT-4o mini Transcribe
• GPT-4o Transcribe Diarize
• GPT-4o Audio
• GPT-4o mini Audio
• GPT-4o Realtime
• GPT-4o mini Realtime
• GPT-4o mini TTS
• GPT-4o Search Preview
• GPT-4o mini Search Preview

Research

• Persona Features Control Emergent Misalignment (Wang et al., Jun 24, 2025) - finetunes gpt-4o-2024-08-06

Models