Cesium

Every agent.
Your machine.
One workbench.

Chat with any coding agent, edit real files, and run real terminals — on your machine, from anywhere.

Open workbench

55132.905

caesium

the element that defines the second

Cesium workbench, light theme: an agent conversation tracing WebSocket reconnect logic with tool calls and a backoff table — A live session — an agent tracing WebSocket reconnect logic in this repo.

Cesium workbench, dark theme: an agent conversation tracing WebSocket reconnect logic with tool calls and a backoff table — A live session — an agent tracing WebSocket reconnect logic in this repo.

Works with the agents you already use

CesiumCursorCodexClaude CodeOpenCodeDevinGrok BuildPi AgentAntigravityCesiumCursorCodexClaude CodeOpenCodeDevinGrok BuildPi AgentAntigravity

9,192,631,770

oscillations of a caesium-133 atom define one second. Named for the element that keeps time honest — every agent event is streamed live, so nothing goes unaccounted for.

01·Versatility

A full workbench, not another chat box

Everything an agent needs to work — and everything you need to watch it — in one window.

Agent conversations

Streaming chats with tool approvals and history that survives restarts.

A real IDE, in the browser

Editor, file tree, and tabs on the folders on your disk — not a sandbox.

Integrated terminals

Watch what your agents run, scroll back through it, and take over whenever you want.

Workspaces on your terms

Switch between real directories. Access stays scoped to folders you chose.

Voice input

Dictate prompts. Configure transcription once and talk to your codebase.

Storage that scales with you

Plain files by default — no services to run. Switch to a database when you need to.

02·Architecture

Cloud reach. Local roots.

The client is a window you can open from anywhere. The engine stays on hardware you control. Your source never has to leave home.

The client

Open from anywhere

A window onto your machine — nothing sensitive lives here.
Installable as an app; one setting points it at your engine.
Open it from a laptop, a phone, or a tablet.

REST + WebSockets

The engine

Runs with your code

Files, terminals, and agents never leave your machine.
Auth and rate limits when you open it beyond this computer.
Local files by default; a database when you scale.

03·Agents

One conversation, many minds

Switch agents mid-thread with context intact. Pick models from one composer. You approve every tool call, whichever agent is driving.

You approve each tool call.
Recent messages go with the handoff.
Bring your own keys. You own the accounts.

Handoff, mid-thread

Cursorscaffolds the migration plan

handoff

Claude Codeimplements and edits files

handoff

Codexreviews the diff and runs tests

04·Platform support

One engine, every screen

Start a task at your desk. Approve the last tool call from the couch.

Web

Any modern browser, installable as an app.

Desktop

A native windowed workbench on the same engine.

Mobile

Your agents, pocket-sized.

Tablet

Touch-tuned layout for iPad.

Your code stays home. Your agents don't rest.