Cashu Emoji Tokens (Variation Selector encoding)

This skill helps agents decode Cashu tokens received as emoji (and encode tokens for sending), and it also supports general hidden messages inside emojis.

If the decoded text starts with cashu, it’s likely a Cashu token. Otherwise treat it as a plain hidden message.

Why this exists

Some services embed a cashu... token into an emoji using Unicode variation selectors (VS1..VS256). Chat apps often display only the emoji, but preserve the hidden selector characters.

Important: many messengers can truncate or normalize Unicode. If the variation selectors are lost, the embedded token cannot be recovered.

Quickstart (copy/paste)

git clone https://github.com/robwoodgate/cashu-emoji.git
cd cashu-emoji
npm ci

# decode a whole message (recommended)
node ./bin/cashu-emoji.js decode "\x3Cpaste message>"

# decode and print mint/unit/amount if it’s a cashu token
node ./bin/cashu-emoji.js decode "\x3Cpaste message>" --metadata

# decode as structured JSON (agent-friendly)
node ./bin/cashu-emoji.js decode "\x3Cpaste message>" --metadata --json

# encode a hidden message
node ./bin/cashu-emoji.js encode "🥜" "hello from inside an emoji"

# encode a cashu token
node ./bin/cashu-emoji.js encode "🥜" "cashuB..."

What you can do

1) Decode

• Input: entire message text (may include other text/emojis)
• Output: the embedded UTF‑8 text, usually a cashuA.../cashuB... token

node ./bin/cashu-emoji.js decode "\x3Cpaste entire message>"

Decode semantics (important): the decoder ignores normal characters until it finds the first variation-selector byte, then collects bytes until the first normal character after that payload begins.

2) Encode

• Input: a carrier emoji (recommend 🥜) and a token string
• Output: an emoji string that visually looks like the emoji but contains the hidden token

node ./bin/cashu-emoji.js encode "🥜" "cashuB..."

Tip: some messengers are less likely to deliver a truncated/corrupted emoji-token if any normal text follows it (even a single character). It’s not required, just a delivery reliability trick.

Tip (Telegram): sending the emoji-token inside a code block / “monospace” formatting can help preserve the hidden characters and makes it easier to tap-to-copy.

Optional metadata

To sanity-check the decoded token without redeeming it, you can request metadata.

For programmatic/agent use, prefer JSON output:

node ./bin/cashu-emoji.js decode "\x3Cmessage>" --metadata --json

Example JSON response (Cashu token):

{
  "text": "cashuB...",
  "isCashu": true,
  "metadata": {
    "mint": "https://mint.example",
    "unit": "sat",
    "amount": 21
  },
  "metadataError": null
}

Example JSON response (plain hidden message):

{
  "text": "hello from inside an emoji",
  "isCashu": false
}

node ./bin/cashu-emoji.js decode "\x3Cmessage>" --metadata

This prints mint/unit/amount using @cashu/cashu-ts getTokenMetadata() (no mint calls).

Cashu gotchas for new agents

• A decoded cashu... token is a bearer asset. Treat it like cash.
• --metadata is a local parse. It can’t prove the token is unspent/valid.
• If decode returns a partial token or nonsense, the messenger likely munged the variation selectors; ask for the token to be re-sent (often with some trailing normal text after the emoji token).

Files

• src/emoji-encoder.ts: core encode/decode
• bin/cashu-emoji.js: CLI wrapper
• examples/: test vectors

Safety

This tool only encodes/decodes text. It does not spend funds.