px0 is a lightweight browser-based IDE built for reading and verifying code written by AI agents rather than for writing code yourself. It boots in under 1 millisecond, idles at 20 MB of memory, and can fuzzy-search across the entire Linux kernel (95,710 files) in 6 milliseconds. That's roughly 70 times lighter than VS Code, which uses 1,440 MB across 15+ processes and takes several seconds to start. The tool runs as a single static Go binary with zero configuration, no Electron, no Node, and no external runtime dependencies. It binds to localhost by default but can be tunneled for remote use. The core feature set is built around fast navigation and inspection rather than editing. You get fuzzy file search, symbol lookup, and full-tree regex scanning all responding in milliseconds. Git awareness shows you file status and diffs against HEAD. There's rendered Markdown preview, language server support (gopls, rust-analyzer, pyright, and others) for go-to-definition and find-references, and a syntax highlighter using Chroma that supports roughly 280 languages. The rendering engine only mounts the visible window plus 24 rows of overscan—opening a 400,000-line file costs the same as opening a 10-line one. The scoring algorithm for fuzzy matching rewards basename hits, word boundaries, and camelCase humps the way fzf does, so results feel natural. The design philosophy is explicit: you're not editing, so traditional IDE overhead is waste. No write endpoints, no extension host, no plugin marketplace, no telemetry beyond a daily GitHub release check. The benchmarks show real numbers from shallow clones of actual repos—Flask indexes in 1 ms, Redis in 13 ms, Django in 39 ms, and the Linux kernel in 370 ms. Memory usage stays proportional to what you're indexing rather than exploding with a language server and extension host. It's positioned as a companion tool: keep your editor for the code you still type, use px0 to audit agent output or navigate a massive monorepo without spinning up the fans.