rumb

pre-alpha · linux · not your daily driver

An experimental Rust web browser.

Servo renders the page. A vendored slice of Zed's GPUI draws everything around it. Between them, a zero-copy bridge that hands a frame from one GPU context to the other without ever touching the CPU.

read the logbook how it is built

where it is

What works, and what does not

Read this before anything else on the page. rumb is early enough that the second column is the honest half.

  • Pages render through Servo, one WebView per tab
  • Tabs, tab groups with custom colours, and pinning
  • Drag to reorder tabs and whole groups
  • A tab strip on any of the four edges of the window
  • Tab discarding — a sleeping tab drops its WebView
  • URL bar with back, forward and reload
  • Mouse, scroll and keyboard forwarded into the page
  • Native cursor changes on hover
  • Fullscreen
  • Page titles and favicons
  • A DevTools panel driving Servo's own DevTools server
  • Settings persisted to $XDG_CONFIG_HOME/rumb/settings.json
  • A rumb:// start page
  • Site coverage is exactly Servo's — GitHub, Discord and most modern CSS break
  • Dynamic resize is pinned by a surfman/Servo bug
  • No IME
  • No bookmarks, no persisted history
  • No site isolation — Servo runs in-process for embedders
  • Linux only

state as of 2026-08-06

how it is built

Two engines, one frame

Servo does not draw to the window. A patch in our fork gives it an offscreen rendering context built from the host's display handle, so it paints into its own framebuffer while GPUI keeps ownership of the drawable the compositor actually sees.

Every frame Servo reports ready is exported as a dma-buf handle — a file descriptor for the GPU memory, plus a fence to say when the writes have landed. GPUI's wgpu backend imports that handle as a texture through the Vulkan HAL and draws it like any other sprite.

The first version did none of that. It read the framebuffer back to the CPU, swapped red and blue, and uploaded the result as an image every single frame. It worked, and it was the wrong shape: a full round trip through system memory for pixels that never left the card.

None of this is secret. The design lives in tramuntana's docs, in the open, because Servo and Stylo are MPL-2.0 and our patches touch their files. The shell — the tabs, the chrome, the compositor bridge on our side — is proprietary.

the winds

Four points, three forks

"Rumb" is a Catalan nautical term for a compass bearing. Each fork is named after a wind, and the rose is the map: what exists, what is being tried, what has been put away.

  • north

    tramuntana

    live

    Our Servo fork. Carries the offscreen rendering context, the NVIDIA/EGL WebGL fallback and the dma-buf export.

  • south

    migjorn

    experimental

    An experimental Servo branch. Where changes go before anyone depends on them.

  • east

    llevant

    unclaimed

    Unclaimed. The rose has four points and we have three forks; this one is empty rather than filled for symmetry.

  • west

    ponent

    retired

    Retired. Kept on the map because a fork that was tried and put away is part of the record.

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Where the work happens