# Formatting Build Output

> Use /usr/local/bin/xcsift for all Swift and Xcode build commands. Pipe xcodebuild build, xcodebuild test, swift build, swift test through xcsift to get structured TOON output with compile errors, warnings, test failures, code coverage, slow tests, and build timing. Essential for parsing Xcode build output, diagnosing compile errors, analyzing test results, and measuring code coverage in any Swift or Xcode project. Use when this capability is needed.

- Skill: `tomevault-io/formatting-build-output` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add tomevault-io/formatting-build-output`
- Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/formatting-build-output/raw
- Safety review: pending (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: tomevault-io (https://skillmd.com/u/tomevault-io)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/tomevault-io/formatting-build-output

---


# xcsift - Xcode Build Output Formatter

xcsift parses and formats xcodebuild/SPM output into token-efficient TOON format optimized for LLM consumption. It extracts compile errors, warnings, test failures, code coverage, and build timing from verbose Xcode output.

## When to Use

**Always** pipe through xcsift when running:
- `xcodebuild build` / `xcodebuild test`
- `swift build` / `swift test`
- Any command that produces Xcode/SPM build output

## Usage Pattern

Always redirect stderr and use TOON format:

```bash
# Build
xcodebuild build 2>&1 | xcsift -f toon
swift build 2>&1 | xcsift -f toon

# Test
swift test 2>&1 | xcsift -f toon
xcodebuild test 2>&1 | xcsift -f toon

# With warnings
xcodebuild build 2>&1 | xcsift -f toon -w

# With code coverage
swift test --enable-code-coverage 2>&1 | xcsift -f toon -c
xcodebuild test -enableCodeCoverage YES 2>&1 | xcsift -f toon -c

# With detailed per-file coverage
swift test --enable-code-coverage 2>&1 | xcsift -f toon -c --coverage-details

# With executable targets
xcodebuild build 2>&1 | xcsift -f toon -e

# Strict CI mode (fail on warnings or errors)
xcodebuild build 2>&1 | xcsift -f toon -W -E

# Slow test detection
swift test 2>&1 | xcsift -f toon --slow-threshold 1.0

# Build info (per-target phases, timing, dependencies)
xcodebuild build 2>&1 | xcsift -f toon --build-info
```

## Key Flags

| Flag | Description |
|------|-------------|
| `-f toon` | TOON format (30-60% fewer tokens than JSON) |
| `-w` | Show detailed warnings list |
| `-W` | Treat warnings as errors (Werror) |
| `-q` | Quiet mode (no output on clean success) |
| `-c` | Include code coverage summary |
| `--coverage-details` | Per-file coverage breakdown (use with `-c`) |
| `-e` | Include executable targets |
| `-E` | Exit with non-zero code on build failure |
| `--build-info` | Per-target phases, timing, and dependencies |
| `--slow-threshold N` | Flag tests slower than N seconds |
| `--config PATH` | Use custom config file (default: `.xcsift.toml`) |
| `--init` | Generate `.xcsift.toml` template in current directory |

## Interpreting TOON Output

TOON uses indentation-based structure with tabular arrays:

```toon
status: failed
summary:
  errors: 1
  warnings: 3
  failed_tests: 2
  passed_tests: 10
  build_time: 12.4s
  test_time: 5.2s
errors[1]{file,line,message}:
  main.swift,15,"use of undeclared identifier 'foo'"
warnings[3]{file,line,message,type}:
  Parser.swift,20,"unused variable 'result'",compile
  View.swift,42,"Publishing changes from background threads",swiftui
  Util.swift,10,"Custom warning message",runtime
failed_tests[2]{suite,test,file,line,message,duration}:
  MyTests,testExample,MyTests.swift,25,"XCTAssertEqual failed",0.123
  MyTests,testOther,MyTests.swift,30,"XCTAssertTrue failed",0.456
```

**Key patterns:**
- `status`: `succeeded` or `failed`
- `errors[N]{columns}:` — tabular array with N items, column names in braces
- `warnings` have `type`: `compile`, `runtime`, or `swiftui`
- `failed_tests` include file/line for navigation and duration
- `null` values mean the data wasn't available (e.g., `build_time: null` if not parsed)

## Troubleshooting

| Problem | Solution |
|---------|----------|
| No errors shown but build failed | Add `2>&1` to capture stderr |
| Coverage shows `null` | Add `--enable-code-coverage` (SPM) or `-enableCodeCoverage YES` (xcodebuild) |
| "xcsift not found" | Install: `brew install xcsift` or `swift build -c release && cp .build/release/xcsift /usr/local/bin/` |
| Coverage for wrong target | xcsift auto-filters to tested target; use `--coverage-path` to override |
| Config not loading | Check `.xcsift.toml` in CWD or `~/.config/xcsift/config.toml` |

## Important

- **Always use `2>&1`** to capture stderr (compiler errors and warnings go to stderr)
- TOON format reduces tokens by 30-60% compared to raw xcodebuild output
- The pre-tool hook automatically wraps build commands when the plugin is installed
- Flaky test detection is automatic (no flag needed) — detects tests that both pass and fail

---
> Source: [ldomaradzki/xcsift](https://github.com/ldomaradzki/xcsift) — distributed by [TomeVault](https://tomevault.io).
<!-- tomevault:4.0:skill_md:2026-07-08 -->