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The FastEdge extension for VS Code compiles Rust, JavaScript, or AssemblyScript source into a Wasm binary, serves it locally through a bundled debugger, and opens a request panel inside the editor for sending test requests and inspecting responses — no separate build tools or terminal commands required.
The build toolchain for the target language must be installed:
  • Rust: rustup target add wasm32-wasip1
  • JavaScript: @gcoredev/fastedge-sdk-js
  • AssemblyScript: assemblyscript, @assemblyscript/wasi-shim, and @gcoredev/proxy-wasm-sdk-as

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Supported languages and app types

The extension builds both FastEdge application types, each tied to a specific language and SDK: Once a project is opened, the extension detects its language automatically, from whichever signal is present: a VS Code language ID of rust for Rust, an asconfig.json file at the project root for AssemblyScript, or a JS/TS file without asconfig.json for JavaScript.

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Install the extension

Install FastEdge Launcher from the Visual Studio Marketplace.
Editors built on the VS Code extension host without access to the Visual Studio Marketplace can install the OS-specific .vsix package instead, downloaded from GitHub releases: {editor-cli} --install-extension fastedge-{os}-{version}.vsix.

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Initialize a workspace

A .vscode/launch.json file is required before debugging. Create one automatically from the Command Palette (Ctrl+Shift+P): FastEdge: Initialize workspace (create launch.json).
The entrypoint field is the only value the extension reads from launch.json:

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Debug an application

Press F5, or run Debug: Start Debug from the Command Palette, to build the active file and open the debugger. Each running app gets an isolated local server on a port between 5179 and 5188, so multiple apps in the same workspace can be debugged at the same time. The debugger opens as a panel inside the editor for building a request — URL, method, headers, body — sending it to the running app, and inspecting the response. Test configurations can be saved and reloaded from the same panel. Two more actions are available from the file explorer’s right-click menu instead of the Command Palette: FastEdge: Load in Debugger on a .wasm file loads a precompiled binary directly, and FastEdge: Load Config in Debugger on a *test.json file loads a saved test configuration.

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Configure runtime values

Environment variables, secrets, and request or response headers are set through test configuration files, not launch.json. The debugger panel writes and reads these controls from a fastedge-config.test.json file in the app root.

As an alternative, the extension auto-discovers .env files in the app root. Add both to .gitignore before storing secrets in either:

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Connect the FastEdge MCP server

Beyond local debugging, the extension can also configure the FastEdge MCP server for AI-assisted workflows. AI clients that support the Model Context Protocol can reach the server directly from VS Code. Running FastEdge (Generate mcp.json) from the Command Palette writes a working server configuration into the workspace — the same Docker-based setup described in AI-assisted development — without editing the JSON file by hand.

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Settings

Two settings control the bundled debugger and its generated MCP configuration: