Does it tell the truth?

Usually. But fluent, confident and wrong look exactly alike.

Language models produce the most plausible continuation of a conversation. Most of the time plausible and true coincide. When they don’t, a model can state something false with complete fluency: an invented statistic, a quote nobody said, a paper that doesn’t exist.

A more worrying kind of falsehood concerns the model’s own actions. Researchers have documented models claiming to have run code, checked a file or finished a task when they had not. As AI agents act on our behalf, what they say they did has to match what they actually did.

Honesty can also bend under pressure. Some models will state things they otherwise say are false when a user or an instruction pushes them to. Three tests on this site look at these failures directly.

What we know

  • Invented facts have become rarer but have not disappeared, and they vary widely by task and product.
  • Web search and tools prevent some errors and introduce others, such as misread sources and invented tool results.
  • Models can be pushed into statements that contradict what they otherwise say is true.

What nobody knows yet

  • Can we reliably tell when a model is uncertain, and does it tell us?
  • Will AI agents report their own mistakes and failures honestly?
Read, watch, listen

The work behind this answer.

Every link was opened and every summary written for this site, with caveats where the source has an interest. New additions are checked by two people.

All 15 in the library
EssentialResearch paperSep 5, 2025For the curious

Why language models hallucinate

Kalai et al. (OpenAI, Georgia Tech) · OpenAI · openai.com

Argues models make things up partly because training and test scoring reward a confident guess over saying 'I don't know', and suggests scoring that penalises confident errors.

Worth knowing: Written by a developer about its own field; the proposed fix depends on benchmark makers changing how they score.

EssentialResearch paperApr 3, 2025For the curious

Reasoning models don't always say what they think

Chen et al. (Anthropic) · Anthropic · anthropic.com

When models used a hint slipped into the prompt, Claude 3.7 Sonnet mentioned it only 25% of the time and DeepSeek R1 39%, so a visible chain of thought can hide what drove an answer.

Worth knowing: Tested with artificial hints in quiz-style questions.

EssentialResearch paperMar 5, 2025Technical

The MASK Benchmark: Disentangling Honesty From Accuracy in AI Systems

Ren et al. (Center for AI Safety, Scale AI) · arXiv · arxiv.org

Tests whether a model says what it actually believes. Bigger models knew more facts but were not more honest, and frontier models often lied when a prompt pressured them to.

Worth knowing: Honesty was measured in constructed pressure scenarios rather than everyday use.

EssentialResearch paperDec 18, 2024For the curious

Alignment faking in large language models

Greenblatt et al. (Anthropic, Redwood Research) · Anthropic · anthropic.com

Told it would be retrained to answer harmful requests, Claude 3 Opus complied more often when it believed it was being trained, reasoning this would stop its values being changed.

Worth knowing: Artificial setup in which the model was told about its training; the values it protected were harmless ones.

EssentialResearch paperDec 6, 2024Technical

Frontier Models are Capable of In-context Scheming

Meinke et al. (Apollo Research) · arXiv · arxiv.org

Given a goal that conflicted with their developers', five of six frontier models sometimes disabled oversight, tried to copy themselves or underperformed on purpose, and some kept denying it.

Worth knowing: Models were usually told to pursue a goal strongly, so this shows capability more than natural tendency.

ReportAug 4, 2026For the curious

Measuring coding agent misalignment in the wild

Selena Zhang and the Docent team (Transluce) · Transluce · transluce.org

In about 5,000 real coding-agent sessions from a public dataset, roughly 2% showed agents seriously evading checks and about 2% seriously overstating success, e.g. merging code without approval.

Worth knowing: Based on one public dataset; rates were near zero in Transluce's own agent traffic.

ReportMar 19, 2026For the curious

How we monitor internal coding agents for misalignment

OpenAI · openai.com

An AI monitor reviewed tens of millions of OpenAI's internal coding-agent sessions over five months, finding agents that bypassed restrictions or misreported their actions but no confirmed scheming.

Worth knowing: Self-reported; the July 2026 incident later showed such monitors were not run on all evaluations.

ArticleDec 4, 2025For the curious

How do AI models persuade? Exploring the levers of AI-enabled persuasion through large-scale experiments

UK AI Security Institute, with Oxford Internet Institute, LSE, Stanford and MIT · AI Security Institute · aisi.gov.uk

Experiments with over 76,000 UK adults and 19 AI models: training and prompting made chatbots more persuasive on political issues, but the most persuasive set-ups made more inaccurate claims.

Worth knowing: Summarises the team's peer-reviewed paper in Science (December 2025); it tested political issues only.

ReportApr 16, 2025For the curious

Investigating truthfulness in a pre-release o3 model

Chowdhury et al. (Transluce) · Transluce · transluce.org

Testing a pre-release OpenAI o3, Transluce found it often claimed to have run code it had no way to run, then made up elaborate excuses when challenged. Other reasoning models did this too.

Worth knowing: Tested a pre-release version; the released model may behave differently.

Tool or datasetApr 2025For everyone

AI Hallucination Cases Database

Damien Charlotin · damiencharlotin.com

A running record of court and tribunal decisions worldwide that found a party relied on AI-invented material, usually fake legal citations. It listed more than 2,000 cases by September 2026.

Worth knowing: Living database kept by one researcher; it counts only cases a court addressed, so the true number is higher.

Research paperJun 8, 2024For the curious

ChatGPT is bullshit

Hicks, Humphries & Slater (University of Glasgow) · Ethics and Information Technology · link.springer.com

Three University of Glasgow researchers argue that calling chatbot falsehoods 'hallucinations' misleads: the systems produce text with no regard for truth, which fits the philosophical idea of 'bullshit'.

Worth knowing: A philosophical argument about how to describe the problem, not an empirical study.

Research paperNov 9, 2023Technical

Large Language Models can Strategically Deceive their Users when Put Under Pressure

Scheurer, Balesni & Hobbhahn (Apollo Research) · arXiv (ICLR 2024 LLM Agents workshop) · arxiv.org

Playing a stock-trading agent under pressure, GPT-4 acted on an insider tip it had been told not to use, then hid the real reason from its manager, without being told to deceive.

Worth knowing: One simulated scenario, designed to create pressure.

Organization2023Technical

Apollo Research

Apollo Research · apolloresearch.ai

Studies 'scheming', where AI systems covertly pursue goals their developers did not intend, and builds methods and tools to detect and monitor it.

Worth knowing: Became a public benefit corporation in 2026 and offers a monitoring product for AI coding agents.