Theo says over 60 percent of T3 Code users who used Codex in the last two weeks also used Claude Code

Context

This is self reported usage data from Theo, who runs T3 Code and T3 Chat, covering only his own product's users. He did not share the underlying numbers or how usage was counted.

Deep dive

On October 19, Theo posted that for the last two weeks, over 60 percent of T3 Code users who used Codex also used Claude Code. He added that the majority of Codex users are Claude Code users.

The post gives one statistic and no chart. It does not say how many people use T3 Code, how many used Codex in that period, or whether the overlap means people switch between the two within the same projects or simply tried both. Since the statistic comes from a tool where both agents can be used, its users may be more likely than average to try several, which would make the overlap higher than among developers in general.

Theo has shared his own usage data on Claude and Codex before, including a chart on October 14 of how models behave in his requests, covered in that day's deck.

The numbers land as OpenAI and Anthropic compete heavily for developers, with OpenAI's Codex team running daily usage resets and Anthropic promoting Claude Code. A large overlap would suggest that loyalty to one coding agent is weak and that developers move to whichever gives them the most usage or the best results that week.

The statistic covers only Codex users, so it says nothing about how many Claude Code users also use Codex.

What to expect next

Watch whether Theo or other tool makers that support several agents, such as Cursor, publish similar overlap data, which would show whether developers really mix agents. Also watch whether OpenAI or Anthropic change pricing or usage limits to win back users who split their time, since a weak lock in means each lab can lose share quickly. The reverse number, how many Claude Code users also use Codex, would complete the picture.