Swift

Debugger: lldb (via lldb-dap, ships with the Swift toolchain) Status: Stable Swift version: 5.5+

Prerequisites

lldb-dap ships with the Swift toolchain and Xcode Command Line Tools. No separate installation needed.

# Install Xcode Command Line Tools (macOS)
xcode-select --install

# Or install the Swift toolchain (Linux)
# https://www.swift.org/download/

Verify: lldb-dap --version

Quick Start

# Debug a Swift package
krometrail launch "swift run" --break Sources/App/main.swift:42

# Debug a specific target
krometrail launch "swift run MyApp" --break Sources/MyApp/OrderService.swift:147

# Debug tests
krometrail launch "swift test" --break Sources/App/OrderService.swift:147

# Debug a specific test
krometrail launch "swift test --filter OrderServiceTests/testGoldDiscount" \
	--break Sources/App/OrderService.swift:147

Conditional Breakpoints

Swift expressions work directly in conditions:

krometrail break "Sources/App/OrderService.swift:147 when discount < 0.0"
krometrail break "Sources/App/OrderService.swift:25 when i == 99"

Inspecting Swift Types

The viewport renders Swift types using LLDB's type system:

Locals:
  discount  = -149.97
  order     = Order(id: 482, total: 149.97, tier: .gold)
  items     = Array<Item>(3 elements)
  result    = Optional<ChargeResult>.none

Enum cases show their associated values. Optionals render as .none or .some(value).

Tips

• Build with debug configuration (swift build without -c release) to include DWARF debug info
• debug_evaluate accepts Swift expressions including computed properties and closures
• On macOS, lldb-dap is typically at /usr/bin/lldb-dap or inside the Xcode bundle
• For iOS/watchOS/tvOS targets, device debugging is not yet supported — simulator only