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The VS Code extension gives you real-time dead code and duplication diagnostics, powered by the fallow LSP server.
Code Lens shows reference counts above each export. Click to peek all usages. Exports with zero references stand out immediately.

Features

  • Real-time diagnostics for all 11 dead code issue types
  • Code Lens showing reference counts above each export (click to peek references)
  • Hover information showing export usage counts, unused status, and duplicate block locations
  • Quick-fix code actions: remove unused export, delete unused file
  • Refactor actions: extract duplicate into shared function
  • Tree views in the sidebar: dead code grouped by type, duplicates by clone family
  • Status bar showing issue count and duplication percentage
  • Auto-download of the LSP binary

Installation

1

Install the extension

Search for “fallow” in the VS Code extensions marketplace, or install from the command line:
code --install-extension fallow-rs.fallow-vscode
2

LSP auto-download

The extension automatically downloads the fallow-lsp binary on first use. No manual setup required.
3

Start coding

Open any JavaScript or TypeScript project. Fallow activates automatically and begins analyzing your codebase. Diagnostics appear inline, and Code Lens annotations show above exports.

Commands

CommandDescription
Fallow: AnalyzeRun full analysis
Fallow: Auto-fixApply auto-fixes
Fallow: Dry RunPreview auto-fixes
Fallow: Restart LSPRestart the language server
SettingDefaultDescription
fallow.lspPathPath to fallow-lsp binary (auto-downloaded if not set)
fallow.autoDownloadtrueAuto-download the LSP binary
fallow.issueTypesallWhich issue types to report
fallow.duplication.thresholdDuplication threshold percentage
fallow.duplication.modemildDuplication detection mode
fallow.productionfalseEnable production mode
fallow.trace.serveroffLSP trace level for debugging
Tree views in the sidebar group issues by type and duplicates by clone family. Great for focused cleanup sessions.

Part of the three tracks

VS Code is one of three ways to use fallow:
  1. Agents run fallow check from CLI or call MCP tools to generate code and verify their own output
  2. You in VS Code see real-time diagnostics to review agent output and spot issues as you code
  3. CI catches the rest so nothing lands in main without passing fallow
The same analysis engine powers all three. What your agent found via CLI, what you see in VS Code, and what CI reports are all consistent.

See also

Agent integration

How AI agents use fallow via CLI and MCP.

CI integration

Add fallow to your CI pipeline.

Dead code analysis

The 11 issue types surfaced in real-time by the extension.