error-toon

Compress verbose browser errors for LLMs. Save 70-90% tokens.

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The Problem

When you copy a browser console error and paste it to an LLM, you're wasting tokens on noise:

Warning: validateDOMNesting(...): <p> cannot appear as a descendant of <p>.
    at p
    at MDXContent (http://localhost:6006/node_modules/.cache/sb-vite/deps/chunk-THCTKSJA.js?v=a1b2c3d4:12754:23)
    at MDXProvider (http://localhost:6006/node_modules/.cache/sb-vite/deps/chunk-THCTKSJA.js?v=a1b2c3d4:12629:3)
    at DocsContainer (http://localhost:6006/node_modules/.cache/sb-vite/deps/chunk-QIBLKSSA.js?v=a1b2c3d4:24567:3)
    at ErrorBoundary (http://localhost:6006/node_modules/.cache/sb-vite/deps/chunk-QIBLKSSA.js?v=a1b2c3d4:24123:5)
    at Docs (http://localhost:6006/node_modules/.cache/sb-vite/deps/chunk-QIBLKSSA.js?v=a1b2c3d4:24892:3)
    ... [30 more lines of framework internals]

4,000+ characters of webpack paths, React internals, and cache hashes — all consumed as tokens before your actual question.

The Solution

error-toon

╭───────────────────────────────────────╮
│ 󰅖 DOM_NESTING                         │
├───────────────────────────────────────┤
│  Guide.mdx:79                         │
│  <p> cannot be descendant of <p>      │
│ frames:                               │
│   MDXContent @ Guide.mdx:79           │
│   DocsContainer @ chunk-QIBLKSSA:24   │
├───────────────────────────────────────┤
│ 📦 4521c → 198c (95% saved)           │
╰───────────────────────────────────────╯

198 characters. The LLM gets exactly what it needs: error type, location, message, and relevant stack frames.

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Quick Start

Install

# Cargo (recommended)
cargo install error-toon

# Or build from source
git clone https://github.com/adrozdenko/error-toon
cd error-toon && cargo install --path .

Use

# 1. Copy an error from your browser console
# 2. Run error-toon
error-toon       # Compresses clipboard, auto-copies result back

# 3. Paste to your LLM — done!

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Output Formats

Colored (default)

Beautiful terminal output with error-type colors and icons:

error-toon

Plain Text

For piping or scripts:

error-toon --plain

type: DOM_NESTING
file: Guide.mdx:79
issue: <p> cannot appear as a descendant of <p>
frames:
  MDXContent @ Guide.mdx:79

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compressed: 4521c → 198c (95% saved)

TOON Format

TOON (Token-Oriented Object Notation) — optimized for LLM parsing:

error-toon --toon

type: DOM_NESTING
file: Guide.mdx:79
issue: <p> cannot appear as a descendant of <p>
frames[1]{fn,loc}:
  MDXContent,Guide.mdx:79
stats{orig,comp,pct}: 4521,198,95

TOON uses tabular arrays (frames[N]{fields}:) and inline objects (stats{fields}:) for maximum token efficiency.

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Supported Error Types

error-toon automatically detects and categorizes 27 error types:

Category	Types	Example
React/DOM	DOM_NESTING, HYDRATION, INVALID_HOOK, REACT_MINIFIED, REACT_KEY	<p> inside <p>, duplicate keys
JavaScript	TYPE_ERROR, REF_ERROR, SYNTAX_ERROR, RANGE_ERROR	undefined is not a function
Network	CORS_ERROR, HTTP_ERROR, NETWORK_ERROR, WEBSOCKET_ERROR	CORS blocked, 404/500 responses
Security	CSP_ERROR, SECURITY_ERROR, MIXED_CONTENT	Content Security Policy violations
Build Tools	STORYBOOK, NEXTJS, MODULE_NOT_FOUND	SB_* codes, build failures
Testing	PLAYWRIGHT	Timeout, locator errors, assertions
System	SYSTEM_ERROR, SERVICE_WORKER, INDEXEDDB_ERROR	ENOENT, ECONNREFUSED

Each type has optimized extraction rules to capture the most relevant information.

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How It Works

┌─────────────────────────────────────────────────────────────────┐
│                     Browser Console Error                        │
│  4000+ chars of webpack paths, React internals, cache hashes    │
└─────────────────────────────────────────────────────────────────┘
                              │
                              ▼
┌─────────────────────────────────────────────────────────────────┐
│                         error-toon                                  │
│  1. Detect error type (25 patterns)                              │
│  2. Extract file location (prefers user code)                    │
│  3. Extract error message                                        │
│  4. Filter stack frames (removes framework noise)                │
└─────────────────────────────────────────────────────────────────┘
                              │
                              ▼
┌─────────────────────────────────────────────────────────────────┐
│                     Compressed Output                            │
│  ~200 chars: type, file, issue, relevant frames                  │
└─────────────────────────────────────────────────────────────────┘

Key optimizations:

• Smart file detection — Finds your code, not node_modules
• Framework noise filter — Removes React, Webpack, Vite internals
• Context-aware extraction — Different logic per error type

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CLI Reference

error-toon [OPTIONS]

Options:
      --no-copy  Don't copy result to clipboard (copies by default)
  -p, --plain    Plain text output (no colors)
  -t, --toon     TOON format output (token-optimized)
  -h, --help     Print help
  -V, --version  Print version

Input Methods

# Clipboard (default)
error-toon                      # Reads from clipboard, copies result back

# Pipe
pbpaste | error-toon            # macOS
xclip -o | error-toon           # Linux
cat error.log | error-toon      # File

# Interactive
error-toon                      # If clipboard empty, prompts for paste

Common Workflows

# Quick compress (auto-copies result to clipboard)
error-toon

# Compress to TOON format for Claude/GPT
error-toon -t

# Use in scripts (no auto-copy when piped)
ERROR=$(pbpaste | error-toon -p)

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Why Rust?

Single binary	No Node.js, Python, or runtime dependencies
Fast startup	~1ms cold start (no JIT warmup)
Small size	1.3MB stripped binary
Cross-platform	macOS, Linux, Windows
Reliable	Strong typing catches bugs at compile time

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Contributing

PRs welcome! Ideas:

• More error patterns (Vue, Angular, Svelte, Cypress, Jest)
• Homebrew formula
• GitHub Actions releases
• VS Code extension

Development

# Run tests
cargo test

# Run with sample input
echo "TypeError: foo is not a function" | cargo run

# Build release
cargo build --release

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License

MIT

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_{Built for developers who talk to LLMs}