September 21, 2026
Less than a year of experience with agents: Charlie Marsh started using them in December 2025
Developer Charlie Marsh only started working with agents in December 2025: Opus 4.5 and GPT-5.2 were in use, followed by [GPT-5.3-Codex](/tools/codex). Less than a year has passed since then.
Charlie Marsh
@charliermarsh
I only started using agents seriously in December 2025. Over the holidays, I went completely mad. We had Opus 4.5 and GPT-5.2 (GPT-5.3-Codex came next). It's crazy that less than a year has passed.
· 30.5K views
Developer Charlie Marsh only started working with agents in December 2025: Opus 4.5 and GPT-5.2 were in use, followed by [GPT-5.3-Codex](/tools/codex). Less than a year has passed since then.
By December 2026, the earliest agentic experience will turn one year old.
