Bret Taylor(@btaylor):Today, most agents are built with the help of other agents like Sierra's Ghostwriter. Yesterday, Sierra open-sourced hyper-𝜏-bench (published as 𝜏^𝜏-bench), a new long horizon agent evaluation that measures how well models can not only act as an agent, but construct one.

Bret Taylor

@btaylor

Co-Founder @SierraPlatform. Board @OpenAI.

Joined July 2007

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Bret Taylor@btaylor

2026.09.09 17:31

Today, most agents are built with the help of other agents like Sierra's Ghostwriter. Yesterday, Sierra open-sourced hyper-𝜏-bench (published as 𝜏^𝜏-bench), a new long horizon agent evaluation that measures how well models can not only act as an agent, but construct one.