Before it
Agent loops were research prototypes described in papers.
The problem
Nobody had packaged one so that an ordinary developer could run it against a goal.
What it introduced
An open loop that plans, calls tools, writes files and recurses until a goal is met, using GPT-4.
Why it matters
It made autonomous agents a mainstream idea, and its unreliability taught the field what was actually hard.
What modern models inherit
Public expectations about agents, both the enthusiasm and the scepticism.
What came next
The sober descendants are today's coding agents with tight scopes and verification.