TYPE 0x0401 · RECURSION FAMILY

RECURSE_SAME

Covenant self-replication. Verifies the spending output carries identical rung conditions as the input. Creates perpetual covenant chains where each spend must re-encumber the output with the same conditions. No Tapscript equivalent.

Recursion Invertible

Ladder Diagram

Fields

Field	Data Type	Size	Side	Description
max_depth	NUMERIC	1-4 B	Conditions	Maximum recursion depth (> 0). Bounds the number of recursive spends allowed.

Wire Format Breakdown

0x0401 0 1 NUMERIC · max_depth Conditions = 9 bytes

0x0401 0 0 Witness = 4 bytes

Total 15 bytes

Evaluation Logic

1.Read max_depth from NUMERIC field

2.If max_depth ≤ 0 → UNSATISFIED

3.Retrieve input_conditions and spending_output from evaluation context

4.Deserialize output conditions from spending output

5.Compare using FullConditionsEqual — must match exactly

6.If conditions match → SATISFIED

7.Otherwise → UNSATISFIED

Worked Example

Perpetual vault with max_depth = 100

Input has RECURSE_SAME(100) + SIG(pubkey_A). Output must carry identical conditions.

max_depth = 100 > 0 → proceed

Output conditions: RECURSE_SAME(100) + SIG(pubkey_A)

FullConditionsEqual → SATISFIED

Output tries to remove the SIG block:

Output conditions: RECURSE_SAME(100) only

FullConditionsEqual fails → UNSATISFIED

JSON Wire Format

{
  "type": "RECURSE_SAME",
  "fields": [
    { "type": "NUMERIC", "value": 100 }
  ]
}

The max_depth field bounds recursion depth. Typical values: 10–1000 depending on expected covenant lifetime.

Use Cases

Perpetual Vaults

A UTXO that can only ever be spent into an output with identical conditions. Combined with SIG or MULTISIG, creates a vault where the signing key can move funds but never remove the covenant restrictions.

Self-Enforcing Contracts

Contracts that guarantee their own perpetuation. Every spend must re-encumber the output with the same rules, ensuring the contract terms survive indefinitely across the UTXO chain.

State Machines

Combined with other blocks, creates state machines where the base covenant structure persists while external state (amounts, timelocks) may change through other block evaluations.

← AMOUNT_LOCK RECURSE_MODIFIED →