thc-edit

Turbo Haskell's source editor. Read the documentation.

I'm building a Haskell environment where source, types, diagnostics, conversations and running programs live in the same place. Open a package, follow a definition, change the code and review the result without having to reconstruct what you were doing in another application.

The editor has menus, overlapping windows and shared split views. It runs in a terminal, a native Metal/Vulkan window, or a browser. The same desktop can work on a remote machine over SSH, with the files and tools beside the project and the display in front of you.

Open a project

thc-edit .

This opens the current directory in the Files pane and its Cabal package file, when there is one. Pass source files to start with those instead:

thc-edit Main.hs Other.hs

Use --window for a native window or --web for the browser. The default is the terminal. To get the executable, see Build and run below.

Each desktop runs in its own session. Detach and return with thc-edit --resume, or choose a different display with thc-edit --web --resume. In a terminal, Ctrl+] detaches; File > Exit finishes the session. Sessions covers choosing an unfinished desktop and continuing on another frontend.

Working in the editor

Use F3 to open a file, F2 to save and F10 to enter the menus. F1 opens this guide. Menu descriptions and clickable shortcuts appear in the status bar. On a Mac, Command+O/S/W/Q also opens, saves, closes and exits; function keys may need Fn/Globe.

The Files pane follows the selected directory. Ctrl+B shows or hides it. Drag a window by its title, resize it from the corner, or use Window > Tile and Window > Cascade. Window > Split vertically and Split horizontally open another view of the same buffer, including its undo history. F6 cycles windows; Alt+1 through Alt+9 selects a numbered window directly.

In the browser, Ctrl/Cmd+G finds the next match; use Search > Go to line for a line number. Native and browser frontends use the system clipboard. In a text terminal, Copy and Cut also request the system clipboard through OSC 52 where supported; paste external text through your terminal. Options > Preferences also offers WordStar keys.

A star in a file's title means unsaved edits. Saving checks whether the disk file changed underneath you. Clean buffers reload external changes; when both versions changed, the editor offers Compare, Reload, Keep and Save as. File > Disk changes returns to an unresolved conflict.

The editing guide covers navigation, selection, searching, splits and external changes. Files containing binary data open in the hex editor; Edit > Text / hex mode changes views without changing the bytes.

Haskell

Put a Haskell Language Server compatible with your package's GHC on PATH. The editor starts it in the project and sends unsaved edits as you work.

• Shift+F1 inspects the type at the cursor; pausing over source also shows type information in the status bar.
• F12 follows a definition. Ctrl+Space completes an identifier.
• Right-click source and choose Rename to update a symbol across files. Review and save the resulting buffers.
• Tools > Messages shows diagnostics. Enter or double-click takes you to the source; Alt+F8 and Alt+F7 visit the next and previous message.

Compile > Make (F9) builds the selected THC or GHC target. Run > Run (Ctrl+F9) runs it, with an embedded terminal for interactive programs. Use Run > Target to choose the toolchain and executable. Debug > Launch starts a debugger; Debug > Attach connects to a running DAP server. Set breakpoints, step, and inspect the stack and variables alongside the source. The Haskell guide covers language tools; running and debugging covers setup and the build/debug workflow.

Review and conversation

Tools > Git diff shows saved staged, unstaged and untracked changes. Tools > Approve changes commits all reviewed saved changes in the repository after asking for a message. Save buffers before reviewing. The branch badge shows repository status; right-click it for Fetch, Pull and Merge. The Git guide explains what is reviewed and committed.

Configure an ACP provider under Options > Agents, then open Tools > Conversation. The provider can inspect live window titles, buffer contents and selections through the editor’s MCP tools, including unsaved text. It can also use session tools for HLS, window layout, checked edits, build/run/test, shared terminals and source debugging. Enter sends a query, Shift+Enter adds a line and Escape cancels an active reply. Queries sent while a reply is running are queued; Ctrl+Enter steers when supported by the provider. Click the conversation title to choose its model and reasoning effort.

Replies, code and tool activity remain beside your files. Permission requests let you inspect proposed work before allowing it; editor-mediated file changes preserve Undo. The conversation guide covers provider setup, review and resuming sessions.

Work on another machine

With thc-edit installed on both machines, open a remote project using an SSH host or alias:

thc-edit --window buildbox:projects/example
thc-edit --web buildbox:projects/example

Files, HLS, Git and project commands run there. Drawing and clipboard access stay local. A dropped connection leaves the session running so you can reconnect to the same buffers. thc-edit --resume also remembers the host for remote sessions. The remote guide covers installation and paths.

Build and run

The default build includes native windows, the browser and embedded terminals (on POSIX), along with terminal display and SSH sessions. You need GHC 9.6 or newer, Cabal, pkg-config, utf8proc 2.10+, SDL3 3.2+ and libghostty-vt. Installation covers these dependencies and the Linux font stack.

cabal run thc-edit -- --window .
cabal run thc-edit -- --web .
cabal install exe:thc-edit --installdir="$HOME/.local/bin"

--window selects Metal on macOS and Vulkan elsewhere. Build flags are opt-out: -f-window, -f-web and -f-terminal omit individual components. A minimal terminal-display or remote-server build is:

cabal install exe:thc-edit -f-window -f-web -f-terminal

It needs utf8proc but neither SDL nor Ghostty. Sessions and SSH editing remain available in every build.

Finding your way around

• The user guide groups the editing, Haskell, Git, conversation and remote workflows.
• Display and frontends covers screen size, fonts, browser uploads/downloads, appearance and keyboard handling.
• Development covers checks, rendering previews and the source layout. Architecture describes buffers and display transport.
• docs/design/ and docs/plans/ retain the design and implementation records.
• THC is the compiler and runtime. The editor is a separate executable and can edit projects without a THC installation.

Contact Information

Contributions and bug reports are welcome! Please feel free to contact me through GitHub.

-Edward Kmett