TYPE 0x0403 · RECURSION FAMILY

RECURSE_UNTIL

Time-bounded covenant. Must re-encumber the output with identical conditions until block height reaches the specified threshold, at which point the covenant terminates and the UTXO is free. No Tapscript equivalent.

Recursion Invertible

Ladder Diagram

Fields

Field	Data Type	Size	Side	Description
until_height	NUMERIC	1-4 B	Conditions	Target block height at which the covenant terminates. Before this height, output must re-encumber with same conditions.

Wire Format Breakdown

0x0403 0 1 NUMERIC · until_height Conditions = 9 bytes

0x0403 0 0 Witness = 4 bytes

Total 15 bytes

Evaluation Logic

1.Read until_height from NUMERIC field

2.Read effective_height from evaluation context (current block height)

3.If effective_height ≥ until_height → SATISFIED (covenant terminates, no re-encumbrance required)

4.Otherwise, verify output carries identical conditions to input

5.If conditions match → SATISFIED

6.If conditions differ → UNSATISFIED

Worked Example

Vesting covenant: until_height = 850,000

Current block height: 849,500. Spend must re-encumber.

849,500 < 850,000 → must re-encumber

Output carries identical conditions → SATISFIED

Same covenant at block 850,000:

850,000 ≥ 850,000 → SATISFIED (covenant terminates, output is free)

JSON Wire Format

{
  "type": "RECURSE_UNTIL",
  "fields": [
    { "type": "NUMERIC", "value": 850000 }
  ]
}

The until_height is an absolute block height. For a ~6-month lockup from current height ~840,000: use 840,000 + 26,280 = 866,280.

Use Cases

Vesting Schedules with Unlock Date

Employee token vesting that enforces re-encumbrance until a future block height. Before the cliff, funds can be moved but must remain covenanted. After the cliff, the covenant drops and funds are fully liquid.

Temporary Covenants

Restrictions that are useful only during a specific period (e.g., a governance vote window). The covenant enforces rules during the active period and automatically dissolves afterward.

Auto-Expiring Restrictions

Spending restrictions imposed by a counterparty that expire after a known block height. Useful for escrow arrangements where restrictions must not persist indefinitely.

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