Fix: IntelliSense Not Working

Wrong language mode

VS Code only runs language features for files it recognizes. If the language mode is wrong, no IntelliSense.

Check: Bottom-right corner shows the language. Click it to change.

Common cases:

• .vue file shows "Plain Text" → change to "Vue"
• .jsx file shows "JavaScript" instead of "JavaScript React"
• .tsx file shows "TypeScript" instead of "TypeScript React"
• .mjs or .cjs file shows "Plain Text"

Language server crashed

Each language has a "language server" — a background process that powers IntelliSense. If it crashes, all language features stop.

Restart by language:

TypeScript/JavaScript:
  Ctrl+Shift+P → "TypeScript: Restart TS Server"

Python:
  Ctrl+Shift+P → "Python: Restart Language Server"

Any language:
  Ctrl+Shift+P → "Developer: Restart Extension Host"

tsconfig.json or jsconfig.json issue

For JavaScript and TypeScript, the language server reads tsconfig.json (or jsconfig.json) to understand your project. A broken config disables IntelliSense.

Quick diagnostic — Open TS Server log:

1. Command Palette → "TypeScript: Open TS Server Log"
2. Look for "Config file error" or "Cannot find module"
3. Or check the status bar: it shows a warning icon if the config is broken

Common config problems:

• JSON syntax error in tsconfig.json (trailing comma)
• Wrong moduleResolution setting
• Missing paths mapping that code imports rely on
• include or exclude pattern that excludes the file

Extension intercepting completions

AI completion extensions (Copilot, Cursor Tab, Tabnine, Codeium) sometimes take over and suppress native IntelliSense. Or two AI extensions fight each other.

Test: Disable all AI completion extensions temporarily.

# Quick test — disable all extensions
code --disable-extensions

# If IntelliSense works, one of your extensions was suppressing it
# Re-enable one at a time to find which

Common setting to check:

"editor.inlineSuggest.enabled": true   // enable Copilot-style suggestions
"github.copilot.enable": { "*": true }  // global Copilot toggle

// If Copilot is intercepting too aggressively:
"github.copilot.enable": {
  "*": true,
  "markdown": false,
  "plaintext": false
}

Memory / project size

On very large projects, the TS server or Python language server runs out of memory and stops responding. Symptoms: IntelliSense works at first, then dies after a few minutes.

Fix: Increase the memory limit.

// .vscode/settings.json
{
  "typescript.tsserver.maxTsServerMemory": 4096,
  "python.analysis.memory": 4096
}

// Or exclude heavy folders from the project
"typescript.tsserver.exclude": [
  "**/node_modules",
  "**/dist",
  "**/build"
]