MOGWAI Language Support for Visual Studio Code

Full language support for MOGWAI — a stack-based RPN scripting engine for .NET

Features

Syntax Highlighting

MOGWAI .mog files are fully colorized out of the box:

Control keywords — if, then, else, while, for, foreach, forever, switch, guard, trap, task, class, and more
Operators — -> (store), => (typed store), --> (pipeline), ->+ ->- ->* ->/ (compound store)
Sigils — &A (in-place reference), @A (static eval), !A (auto-eval)
Strings — with {! ... } interpolation blocks
Variable names — 'A', 'myVar'
Numbers — integers, floats, hexadecimal
Constants — true, false, null, empty
Comments — # line comment
Delimiters — «» (functions), {} (blocks), [] (records), () (lists)

Dynamic Primitive Highlighting

When connected to a MOGWAI runtime, all runtime primitives are colorized according to their group:

Group	Category	Color
`GE`	General	function color
`MH`	Math	numeric color
`SK`	Stack	keyword color
`RT`	Runtime	macro color
`ER`	Error	type color
`DG`	Debug	comment color (dimmed)

The highlighting updates automatically when you connect to a different runtime.

Locally Declared Functions

Functions you declare with to '...' do { }, to '...' with [...] do { }, to '...' params [...] do { }, with or without a returns (...) clause, are automatically recognized:

Colored in golden italic — visually distinct from language keywords and runtime primitives
Go to Definition (F12 or right-click) — jump directly to a function's declaration from any call site
Insert Function Call — Quick Pick of all declared functions, insert the selected name at the cursor position

If a function name conflicts with a runtime primitive, the primitive color takes priority. This feature works even without a connected runtime.

Function List

All functions declared in the current file are listed in two places:

Outline panel (Explorer sidebar) — full signature for each function
Go to Symbol (Ctrl+Shift+O) — filter by name, jump directly to the declaration

Snippets

Ready-to-use snippets for all common structures:

Prefix	Structure
`if`	if / then
`ife`	if / then / else
`while`	while / do
`dowhile`	do / while
`for`	for loop
`fors`	for loop with step
`repeat`	repeat N times
`forever`	infinite loop
`foreach`	foreach / do
`transform`	foreach / transform (map)
`filter`	foreach / filter
`switch`	switch block
`to`	function declaration
`tow`	function with typed parameters
`top`	function with default parameters
`store`	`->` variant store
`storet`	`=>` typed store
`interp`	string interpolation

Runtime Connection & Execution

The extension connects directly to a running MOGWAI runtime over TCP/IP.

Auto-discovery — broadcasts a UDP discovery message on the local network and lists all responding runtimes
Quick Pick — select the runtime to connect to (name, IP:port, version, OS, framework)
Run — executes the current .mog file, results stream to the MOGWAI Output Channel
Error navigation — on execution error, the cursor jumps to the exact error position and the zone is highlighted in red
Status bar — shows the connected runtime name and version

Debugging

Debug mode — honors breakpoints (debug.halt primitive or ¤ symbol)
Pause / Step / Resume / Halt — full control over execution from the editor toolbar
Current instruction highlighted in blue while paused
Multi-file debugging — when a script includes other files via mogwai.include, the debugger follows execution across files, opening included files side by side automatically
TRON mode — debug.tron animates execution instruction by instruction with a configurable delay, following the code in real time across included files too

Runtime Panel

A dedicated MOGWAI panel in the sidebar shows, in real time:

Stack — current contents of the MOGWAI stack (RPN)
Local Variables — name, type, and value
Global Variables — name, type, and value

Refreshes automatically after each execution, pause, or step. Manual refresh available.

Autocompletion

Suggestions as you type:

MOGWAI static keywords (if, while, foreach, forever, class...)
Primitives from the connected runtime, with their group shown as detail

Requirements

A running MOGWAI runtime (v8.0 or later) with the studio mode active
The runtime must be reachable on the local network (UDP port 1968 for discovery, TCP port provided by the runtime)

Getting Started

Open any .mog file — syntax highlighting activates automatically
Click $(plug) MOGWAI: not connected in the status bar, or run MOGWAI: Connect to Runtime from the Command Palette (Ctrl+Shift+P)
Select a runtime from the list
Click the ▶ button in the editor toolbar or run MOGWAI: Run Current File

Commands

Command	Description
`MOGWAI: Connect to Runtime`	Discover and connect to a MOGWAI runtime
`MOGWAI: Disconnect`	Disconnect from the current runtime
`MOGWAI: Run Current File`	Execute the current `.mog` file
`MOGWAI: Debug Current File`	Execute with breakpoint support
`MOGWAI: Pause`	Pause execution
`MOGWAI: Step`	Execute the next instruction
`MOGWAI: Resume`	Resume execution
`MOGWAI: Halt`	Stop execution immediately
`MOGWAI: Refresh`	Refresh the Runtime panel
`MOGWAI: Insert Function Call`	Insert a declared function's name at the cursor

Extension Settings

Setting	Default	Description
`mogwai.runtime.udpPort`	`1968`	UDP port used for runtime discovery
`mogwai.runtime.discoveryTimeoutMs`	`5000`	Discovery timeout in milliseconds

About MOGWAI

MOGWAI is a stack-based RPN scripting engine for .NET, inspired by HP RPL (HP 28S, HP 48). It has been in development for over 10 years and was open-sourced in February 2026 under the Apache 2.0 license.

→ MOGWAI on GitHub

→ Full VS Code integration guide