An agent-native terminal editor. A spiritual successor to Light Table for the age of coding agents, with the terminal as a first-class citizen.

Rust core, Steel (embedded Scheme) editor layer, ratatui for drawing.

This is a build in progress, not a released editor. It opens files, edits them the way vim's grammar does, talks to real language servers, and draws the surfaces its design specifies — but a great deal of the vocabulary is declared and not yet built.

That is deliberate and it is visible rather than hidden. Every capability is a row in one registry, and a row whose implementation has not landed answers by naming the task that will build it:

$ phosphor open-timeline
#refused · not built yet — T073 builds it

So if you press a key and get a sentence with a task id in it, that is the editor being honest, not broken. docs/TASKS.md is what those ids refer to.

Needs the pinned toolchain in rust-toolchain.toml (rustup installs it automatically) and just.

$ just install          # builds and puts `phosphor` on your PATH
$ phosphor src/main.rs

ZQ or ctrl-c leaves. :help lists the keymap, :repl opens a Scheme prompt against the running editor.

Without a file it opens an empty buffer; :write <path> gives it a name.

Four things are unusual enough to be worth knowing before reading any code.

There is no keymap in Rust. Every binding in the editor lives in runtime/keymaps.scm, and the input machine asks that file on every keystroke without caching the answer. A binding you change at :repl is in force on the very next key, with no reload step. crates/phosphor-steel/tests/no_bindings_in_rust.rs fails if any Rust file binds a key.

One registry, three doors. A capability is declared once; the Steel, MCP and CLI front-ends are total functions over that table and none of them may name a capability. That is what makes a one-door capability unconstructible rather than merely tested against — and crates/phosphor/tests/parity.rs walks every row through all three doors so the claim is enumerated rather than asserted.

The lints are structural, and each exists because the thing it catches already happened. They live in scripts/lint-*.sh, run under just lint, and enforce things a type system cannot: no literal colours outside the theme, no Action construction in the widget layer, every mutation a ticked task declares reachable from a keystroke, every claim in the docs recomputed from the tree it describes. Adding one means dropping a script into that directory — never editing the justfile or CI.

The design documents are the specification. docs/design/*.dc.html are imported verbatim from the design project that produced them; the palette, the 37 mockup screens and the voice come from there. Where the build and the design disagree, that gets flagged rather than quietly reconciled.

vendor/ holds two git subtree forks kept deliberately outside the workspace so our lints stop at the seam. Every hunk that diverges from upstream has to be explained in that fork's VENDOR.md.

$ just            # list every recipe
$ just gate       # everything CI runs, in CI's order — run this before calling something green
$ just test       # cargo-nextest, plus the doctests nextest cannot see
$ just lint       # the structural lints

just --list is the authority on what exists, not this file.

• docs/README.md — the reading order for the design documents and the plan. Start there.
• CLAUDE.md — the working agreement: commands, the lints and what each one caught, the rules about vendored code, and the standard for asserting things you have not read.
• docs/TASKS.md — the task breakdown, with acceptance criteria and the checkpoints.

Dual-licensed under either of

• Apache License, Version 2.0 (LICENSE-APACHE)
• MIT license (LICENSE-MIT)

at your option. This is the convention across Rust crates, and it matches the vendored forks.

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in this work by you, as defined in the Apache-2.0 licence, shall be dual licensed as above, without any additional terms or conditions.