The big step function here seems to be RL on tool calling.
Claude 3.7/3.5 are the only models that seem to be able to handle "pure agent" usecases well (agent in a loop, not in an agentic workflow scaffold[0]).
OpenAI has made a bet on reasoning models as the core to a purely agentic loop, but it hasn't worked particularly well yet (in my own tests, though folks have hacked a Claude Code workaround[1]).
o3-mini has been better at some technical problems than 3.7/3.5 (particularly refactoring, in my experience), but still struggles with long chains of tool calling.
My hunch is that these new models were tuned _with_ OpenAI Codex[2], which is presumably what Anthropic was doing internally with Claude Code on 3.5/3.7
tl;dr - GPT-3 launched with completions (predict the next token), then OpenAI fine-tuned that model on "chat completions" which then led GPT-3.5/GPT-4, and ultimately the success of ChatGPT. This new agent paradigm, requires fine-tuning on the LLM interacting with itself (thinking) and with the outside world (tools), sans any human input.
The big step function here seems to be RL on tool calling.
Claude 3.7/3.5 are the only models that seem to be able to handle "pure agent" usecases well (agent in a loop, not in an agentic workflow scaffold[0]).
OpenAI has made a bet on reasoning models as the core to a purely agentic loop, but it hasn't worked particularly well yet (in my own tests, though folks have hacked a Claude Code workaround[1]).
o3-mini has been better at some technical problems than 3.7/3.5 (particularly refactoring, in my experience), but still struggles with long chains of tool calling.
My hunch is that these new models were tuned _with_ OpenAI Codex[2], which is presumably what Anthropic was doing internally with Claude Code on 3.5/3.7
tl;dr - GPT-3 launched with completions (predict the next token), then OpenAI fine-tuned that model on "chat completions" which then led GPT-3.5/GPT-4, and ultimately the success of ChatGPT. This new agent paradigm, requires fine-tuning on the LLM interacting with itself (thinking) and with the outside world (tools), sans any human input.
[0]https://www.anthropic.com/engineering/building-effective-age...
[1]https://github.com/1rgs/claude-code-proxy
[2]https://openai.com/index/openai-codex/