Vite Checker Setup

Install and configure two complementary systems so all errors appear in the terminal during development:

• vite-plugin-checker — TypeScript compile-time errors (types, syntax).
• server.forwardConsole — Browser runtime errors (console.*, unhandled errors) via Vite 8 native support.

When to use

• Setting up a new Vite + TypeScript project
• User wants TS errors in terminal during dev
• User complains about not seeing type errors until build
• User wants browser console output (runtime errors, logs) in the terminal
• Adding dev-time error reporting to an existing Vite project

Pre-flight checks

Before making any changes, verify current state:

1. Check Vite version in package.json devDependencies to determine which approach to use:
   • Vite >= 8: use native server.forwardConsole
   • Vite < 8: use vite-plugin-terminal (legacy fallback)
2. Check package.json for vite-plugin-checker in devDependencies.
3. Check vite.config.ts for import checker and its entry in the plugins array, plus forwardConsole in server config (Vite 8+) or import terminal (Vite < 8).

If everything is already installed and configured, inform the user and skip all steps. Only install/configure what is missing.

If vite-plugin-terminal is installed but the project uses Vite 8+, suggest migrating:

npm uninstall vite-plugin-terminal

And remove its import and plugin entry from vite.config.ts.

Steps

1. Install dependencies (skip already installed)

npm i -D vite-plugin-checker

If Vite < 8, also install:

npm i -D vite-plugin-terminal

2. Configure vite.config.ts

Vite 8+ (recommended)

Add checker to plugins and forwardConsole to server config. No need to wrap defineConfig in a callback — checker only runs in dev by design, and forwardConsole only activates during dev server.

import checker from "vite-plugin-checker";

export default defineConfig({
  plugins: [
    // ...existing plugins
    checker({ typescript: true }),
  ],
  server: {
    // ...existing server config
    forwardConsole: {
      unhandledErrors: true,
      logLevels: ["log", "warn", "error", "info"],
    },
  },
});

Vite < 8 (legacy fallback)

Convert defineConfig to callback form if needed, and use vite-plugin-terminal:

import checker from "vite-plugin-checker";
import terminal from "vite-plugin-terminal";

export default defineConfig(({ mode }) => ({
  plugins: [
    // ...existing plugins
    mode === "development" && checker({ typescript: true }),
    mode === "development" && terminal({ console: "terminal", output: ["terminal", "console"] }),
  ].filter(Boolean),
}));

3. Commit changes

Commit the modified files:

git add vite.config.ts package.json package-lock.json
git commit -m "chore(dev): add vite-plugin-checker and forwardConsole"

Only include files that were actually changed.

4. Verify

Run npm run dev. You should now see:

• TypeScript errors in the terminal (inline, real-time) and as a browser overlay
• Runtime errors and console output mirrored in the terminal

Key details

• checker runs tsc in a worker thread — it does not block HMR or slow down the dev server.
• forwardConsole (Vite 8+) is a native Vite feature that forwards browser console.* calls and unhandled errors to the dev server terminal via WebSocket. No plugin needed.
• forwardConsole only activates during dev server — production builds are unaffected.
• forwardConsole default is auto-detected: true when an AI coding agent is detected, otherwise false. Explicit config overrides the detection.
• If the project also uses ESLint, checker supports eslint: true as an additional option.

forwardConsole options reference (Vite 8+)

Option	Type	Default	Description
unhandledErrors	boolean	true (when enabled)	Forward uncaught exceptions and unhandled promise rejections
logLevels	('error' | 'warn' | 'info' | 'log' | 'debug')[]	['error', 'warn'] (when enabled)	Which console.* calls are forwarded

Shorthand: forwardConsole: true enables defaults (unhandled errors + error/warn logs).

Vite version compatibility

Vite version	Runtime errors approach	TypeScript errors
>= 8	server.forwardConsole (native)	vite-plugin-checker
< 8	vite-plugin-terminal (plugin)	vite-plugin-checker