compression-utils

name	compression-utils
description	Work with the URL compression system in kheMessage. Use when modifying how content is stored in URLs, debugging encoding issues, or optimizing compression.

Compression Utilities Skill

Work with the URL-based storage and compression system.

When to Use

• Debugging URL encoding issues
• Optimizing compression performance
• Extending the storage format
• Handling special characters

Compression Pipeline

blocks → serializeBlocks (binary + compact props) → CompressionStream (deflate or brotli) → format byte + Base85 → URL hash

Format Versions

Format byte	Encoding	Compression
(legacy)	base64url	deflate-raw
0x01	base64url	deflate-raw
0x02	base85	deflate-raw
0x03	base85	encrypted (AES-GCM)
0x04	base85	brotli

Format detection: if hash contains chars outside base64url (A-Za-z0-9_-), it's base85. Otherwise legacy base64url.

Compact Property Keys

Block properties use short keys when serialized:

• lang → l
• checked → c
• start → s
• emoji → e
• depth → d

Encryption (Format 0x03)

AES-GCM-256 with PBKDF2 key derivation (120k iterations). Payload: salt(12) + IV(12) + ciphertext+tag(16). Triggered via "Lock with password" in Share menu.

URL Structure

https://example.com/?theme=dark#base85EncodedContent

Limitations

• URL length limits (~2000 chars safe, ~8000 max in modern browsers)
• Base85 adds ~25% overhead (vs base64 ~33%)
• Brotli supported in Safari 18.4+, Firefox 147+; deflate used as fallback

Debugging Tips

1. Check browser console for compression errors
2. Test with content containing special characters
3. Verify URL doesn't exceed limits
4. Use DevTools Network tab to check actual URL
5. For encrypted content: ensure Web Crypto API is available