March 2025 was the start of the boom, IMO. Sonnet 3.7 and CC released feb 24th, Responses API + Agents SDK from OAI launched March 11. Two months after we got the first Terminal Bench, then a month later we got tau2 bench.

I guess, its debatable that o1 was the real start- but I think its hard to deny that Claude Code CLI was the first time we had what we now call a coding harness hit the mainstream. And- Sonnet 3.7 was kinda Anthropic's "o1 moment".

God. Opus 4.6 and 5.3-codex feel like ancient history.