SigmaOS
SigmaOS is a macOS-only workspace browser that reimagines tabs as tasks — organized into workspaces, markable complete, lockable — with vertical tabs and split-screen. Tier T3 (first-party site). It's built on WebKit (Safari-like performance/battery) but supports Chrome extensions, and ships an AI assistant, Airis, for contextual help and summarization.
Re-verified against the live site 2026-08-16 (quality cycle). Prices unchanged after six weeks and still macOS-only, with iOS and Windows "coming soon." The tier names on the page are Basic (free, limited Airis), Personal Pro $20/mo (unlimited advanced Airis on GPT-4o) and Personal Max $30/mo (adds Claude and Llama, unlimited summaries) — this page had them as Personal/Pro/Max. Airis has grown two named features since: Look it up (searches and reads across several pages) and interactive summaries. The marketing has moved further toward AI than the pitch this page was written from: SigmaOS now calls itself "the first AI browser engine," built on something it names A1Kit.
SigmaOS anchors the productivity current — the browser as a work-organization surface (tabs = to-dos) rather than an AI agent — but note it also bundles AI (Airis), so even the productivity pole now reaches for an assistant. Its niche is the power-user / founder workflow, the same audience browser-wars-2026 groups with Zen and the tab-management lineage.