xcsift

A Swift command-line tool to parse and format xcodebuild/SPM output for coding agents, optimized for token efficiency.

Overview

xcsift transforms verbose Xcode build output into concise, structured formats that coding agents and LLMs can efficiently parse and act upon. Unlike xcbeautify and xcpretty which focus on human-readable output, xcsift prioritizes information density and machine readability.

Features

• Multiple output formats — JSON (default), TOON (30-60% fewer tokens), GitHub Actions
• Structured error reporting — errors, warnings, linker errors, test failures with file/line locations
• Automatic code coverage — converts .profraw (SPM) and .xcresult (xcodebuild) to JSON
• Build info — per-target phases, timing, dependencies, and slowest targets
• Test analysis — slow test detection, flaky test detection, duration tracking
• GitHub Actions integration — auto-detected workflow annotations with inline PR comments
• Configuration files — .xcsift.toml for project or user-wide defaults
• Quiet/Werror/exit-on-failure modes — for CI pipelines
• xcbeautify/Tuist input — parse pre-formatted output with --xcbeautify
• Streaming large-log parsing — consumes stdin incrementally with bounded line buffering
• MCP proxy — xcsift mcp wraps an Xcode MCP server so agents get structured results

See the full documentation for details.

Installation

Homebrew (Recommended)

brew install xcsift

Build from Source

git clone https://github.com/ldomaradzki/xcsift.git
cd xcsift
swift build -c release
cp .build/release/xcsift /usr/local/bin/

Also available via mise and Mint. Since 1.7.0, releases publish a signed packslip manifest, so mise's packslip: backend verifies the archive before installing it and can link the agent skill of that version (mise skills sync).

Verify a Release

Since 1.7.0, every release is signed by this repository's release workflow. The signer's packslip fingerprint is:

ps1_p3pqpu6mhfthsvnwyk2rm3leli

It names this repository by its numeric ID, not its name, so --pin refuses a release signed from any other repository, including one that later takes over the name:

# Install the latest release, checked against the fingerprint
packslip install github.com/ldomaradzki/xcsift --pin ps1_p3pqpu6mhfthsvnwyk2rm3leli

# Or check archives you downloaded yourself, with the release's packslip.sigstore.json
packslip verify packslip.sigstore.json --pin ps1_p3pqpu6mhfthsvnwyk2rm3leli \
  --artifact xcsift-vX.Y.Z-macos-arm64.tar.gz

Plugin Installation

Integrate with coding assistants via built-in installers:

See Plugin Installation for options and verification steps.

MCP Proxy

xcsift mcp sits between a coding agent and an Xcode MCP server, forwarding the protocol untouched and sifting only the tool results that carry build output:

agent  ⇄  xcsift mcp  ⇄  xcrun mcpbridge  ⇄  Xcode

By default it wraps Xcode's own MCP server (Xcode 26+), reached through xcrun mcpbridge:

xcsift mcp --print-config     # Print an MCP client configuration snippet
xcsift mcp --install          # Register the proxy with Claude Code
xcsift mcp --uninstall        # Remove that registration again
xcsift mcp                    # Same as: xcsift mcp -- xcrun mcpbridge
xcsift mcp -- <any other stdio Xcode MCP server>

{
  "mcpServers": {
    "xcode": {
      "command": "xcsift",
      "args": ["mcp", "--", "xcrun", "mcpbridge"]
    }
  }
}

Setup for a coding agent, in three steps:

1. Enable Xcode's MCP server — Xcode ▸ Settings ▸ Intelligence, or sudo xcrun mcp-server enable (xcrun mcp-server status reports the current state).
2. Register the proxy instead of the bridge: xcsift mcp --install (the same thing as claude mcp add --transport stdio xcode -- xcsift mcp, with the flags you pass recorded in it).
3. Approve the agent xcsift when Xcode asks, on the first project open or build.

xcsift mcp --uninstall takes the registration back out, whichever way it was made.

Xcode approves an agent by binary and signature, so install xcsift (Homebrew) rather than pointing the config at a build directory, and expect one fresh approval after an upgrade.

Raw xcodebuild transcripts are replaced by the structured result. A server that already summarises the build and writes the full log to disk keeps its summary, and the complete diagnostics parsed from that log are appended. The proxy also adds an xcsift_parse_build_log tool so an agent can pull the full diagnostics behind any build log.

See MCP Proxy for the full reference.

Quick Start

Pipe any xcodebuild or SPM command through xcsift. Always use 2>&1 to capture stderr.

# Build
xcodebuild build 2>&1 | xcsift
swift build 2>&1 | xcsift

# Test with coverage
swift test --enable-code-coverage 2>&1 | xcsift --coverage
xcodebuild test -enableCodeCoverage YES 2>&1 | xcsift -c --coverage-details

# TOON format (30-60% fewer tokens)
xcodebuild build 2>&1 | xcsift -f toon -w

# Warnings as errors + exit on failure (CI)
xcodebuild build 2>&1 | xcsift --Werror --exit-on-failure

# Configuration file
xcsift --init                    # Generate .xcsift.toml template

See Usage for the full CLI reference, Output Formats for JSON/TOON/GitHub Actions details, and Configuration for config file options.

Comparison with xcbeautify/xcpretty

Platform Support

• macOS 15+: Full support including code coverage
• Linux (Swift 6.0+): Build/test parsing supported; coverage features unavailable

Development

swift build                            # Build
swift test                             # Run tests
swift format --recursive --in-place .  # Format (required before committing)

Large-log release benchmarks are available in Benchmarks/:

Benchmarks/large-log.sh 10          # Pull-request smoke benchmark
Benchmarks/large-log.sh 10 100 500  # Full size progression

Documentation source is in Sources/xcsift.docc/. Preview locally:

swift package --disable-sandbox preview-documentation --target xcsift

Hosted docs: ldomaradzki.github.io/xcsift

License

MIT License