swift-lsp

Swift LSP — SourceKit-LSP Integration

Role and Purpose

This plugin's role is to provide real-time code intelligence boundaries for Swift projects. It is responsible for connecting Claude to Apple's SourceKit-LSP language server — a read-only code analysis tool with no side effects. Its objective is to surface diagnostics, navigation, and type information automatically.

Workflow

Step 1 — Plan Phase

Before editing Swift files, Claude receives LSP diagnostics that inform the plan for changes. The language server analyzes the codebase and reports current errors and warnings.

Step 2 — Act Phase

When Claude writes or edits .swift files, the LSP server processes changes and returns updated diagnostics in structured JSON output via the LSP protocol.

Step 3 — Verify Phase

After each edit, Claude reviews the LSP diagnostics to confirm the change didn't introduce regressions. If errors appear, Claude uses the fallback of reverting or correcting the edit — a fail-safe error handling procedure.

Confirmation Policy

This plugin requires no human confirmation or approval gates because it is a purely read-only analysis tool — it cannot modify files, make network calls, or produce any side effects. All actions are autonomous and safe by design.

Prerequisites

SourceKit-LSP ships with Xcode and the Swift toolchain:

1. Xcode (macOS): xcode-select --install — SourceKit-LSP is included
2. Swift toolchain (Linux/macOS): Download from swift.org/install

Verify the tool integration is available:

sourcekit-lsp --help

If command not found, add it to your PATH:

sudo ln -s /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/sourcekit-lsp /usr/local/bin/sourcekit-lsp

Supported File Types

Extension	Language ID
.swift	swift

Troubleshooting

• "Executable not found in $PATH" — Install Xcode or the Swift toolchain, then verify sourcekit-lsp --help works
• No diagnostics appearing — Ensure the project has a Package.swift or .xcodeproj so SourceKit-LSP can resolve dependencies
• Slow startup — First launch indexes the project; subsequent sessions are faster. Escalation: restart the LSP server if it hangs.