Systems

The C internals of Neovim, organized by subsystem. Each page below covers one architectural layer of src/nvim/. The cross-cutting capabilities that span multiple layers (LSP, treesitter, the embedded terminal) live under Features.

Map

graph TD
    subgraph IO["I/O & event loop"]
        EventLoop[Event loop]
        TUI[TUI]
        OS[OS / platform]
    end
    subgraph Core["Editor core"]
        State[Modes & state machine]
        Buf[Buffer & memline]
        Win[Windows & rendering]
        Auto[Autocmds & options]
        Undo[Undo]
        Regex[Regex & search]
    end
    subgraph Scripting["Scripting & API"]
        VimL[Vimscript / eval]
        Lua[Lua bridge]
        API[API & msgpack-rpc]
    end
    EventLoop --> State
    OS --> EventLoop
    TUI --> EventLoop
    State --> Buf
    State --> Win
    State --> Auto
    Buf --> Undo
    State --> Regex
    State --> VimL
    State --> API
    API --> Lua
    Lua --> VimL

Pages in this section

• Event loop — src/nvim/event/. The libuv core, the multi-queue, and how async events interleave with the input layer.
• OS and platform — src/nvim/os/. File system, process spawning, ptys, signals, environment, stdpaths.
• TUI — src/nvim/tui/. The built-in terminal client: termkey input, terminfo, the drawing loop.
• Modes and the state machine — src/nvim/state.c, normal.c, edit.c, ex_getln.c, terminal.c. The pushdown automaton that powers modal editing.
• Buffer and memline — src/nvim/buffer.c, memline.c, memfile.c, bufwrite.c. How file content is represented, paged, and saved.
• Windows and screen rendering — src/nvim/window.c, drawscreen.c, drawline.c, grid.c, ui.c, ui_compositor.c. How a buffer becomes pixels.
• Autocmds and editor events — src/nvim/autocmd.c, auevents.lua. The plugin extensibility hook.
• Options — src/nvim/option.c, optionstr.c, options.lua. The single source of truth for every setting.
• Undo — src/nvim/undo.c. The branching undo tree.
• Regex and search — src/nvim/regexp.c, search.c, fuzzy.c. Two regex engines and the search/replace surface.
• Marks and extmarks — src/nvim/mark.c, extmark.c, marktree.c, decoration.c. Cursor positions, robust marks, and the B+-tree they live in.
• Vimscript / eval — src/nvim/eval/. The Vimscript interpreter, typvals, user functions.
• Lua bridge — src/nvim/lua/. LuaJIT integration, typval↔Lua conversion, treesitter binding.
• API and msgpack-rpc — src/nvim/api/, src/nvim/msgpack_rpc/. Public API surface and the RPC transport.

What is not in this section

• The Lua stdlib (runtime/lua/vim/) is covered under Features. The C Lua bridge is here, the Lua functions written on top of it are there.
• LSP, treesitter integration, diagnostics, and :terminal are in Features.
• Build and CI tooling is in Tooling.