Sigma
The assistant runs locally by default — no tracking, no cloud dependency, page content that doesn't leave the machine.
Sigma's differentiator is where the inference happens. Its assistant runs locally by default, which changes the answer to the question that decides whether a firm can actually use one of these: when the agent reads this page, where does the page go?
That question is not academic in venture. Portfolio-company correspondence, LP communications, and anything under an NDA carry obligations that don't evaporate because the tool is convenient. Orientation: Agent-Native Browsers makes the point that you should know the answer before the first export, not after — and Sigma, along with Aside's on-device memory, exists because that question has real and differing answers across the category.
The trade is the usual one: local models are less capable than frontier models, so expect a lower ceiling on complex multi-step tasks than Comet or Aside will give you. Good fit for the well-defined, repetitive, confidential jobs — form filling, data entry, extraction from a known layout — rather than open-ended agentic work.