As I crossed over 1000 hours working with AI, I discovered 4 LLM failure modes and 1 user failure mode.
The five failure modes aren't edge cases or rare bugs. They're the structural reality of working with LLMs on any sustained technical task.
Anyone who doesn't understand them will lose work to them without knowing why.
Let's start with the most well-known LLM failure mode called ‘Hallucination’.
#1 LLM Failure Mode: Hallucination.
Hallucination is when the model produces content that isn't grounded in any source.
Common forms of hallucination:
- Inventing citations and references.
- Inventing facts ("the company was founded in 1987").
- Inventing API behaviour ("this function takes an optional X parameter").
- Inventing quotes from real people.
- Inventing technical details that sound plausible.
For subject matter experts, hallucinations are the easiest to catch, as domain knowledge enables pattern recognition.
For non-experts, Hallucination is the most damaging because they can't catch it without domain knowledge.