TYPE 0x0601 · PLC FAMILY

HYSTERESIS_FEE

Fee rate band check. SATISFIED if the transaction fee rate (sat/vB) falls within a configurable [low, high] band. Prevents fee overpayment and enforces economic constraints on spending. No Tapscript equivalent exists.

PLC Invertible

Ladder Diagram

Fields

Field	Data Type	Size	Side	Description
high_sat_vb	NUMERIC	1-4 B	Conditions	Upper bound of the fee rate band (sat/vB)
low_sat_vb	NUMERIC	1-4 B	Conditions	Lower bound of the fee rate band (sat/vB)

No witness fields required. Evaluation uses the transaction context (inputs, outputs, vsize) to compute fee rate.

Wire Format Breakdown

0x0601 0 2 NUMERIC · 3B NUMERIC · 3B Conditions = 14 bytes

0x0601 0 0 Witness = 4 bytes (empty block)

Total 18 bytes

Evaluation Logic

1.Collect conditions NUMERIC fields. Fewer than 2 → ERROR. ReadNumeric the first as high and the second as low; either undecodable → ERROR

2.Range/order check: high < 0, low < 0, or low > high → UNSATISFIED

3.Require ctx.tx, ctx.spent_outputs, and ctx.tx_weight > 0; missing → ERROR (fail-closed).

4.Compute fee = Σ(spent_outputs[i].value) - Σ(tx.outputs[i].value). fee < 0 → UNSATISFIED

5.Compute vsize = (tx_weight + 3) / 4 (BIP 141 WITNESS_SCALE_FACTOR). vsize ≤ 0 → ERROR. Then fee_rate = fee / vsize — truncating integer division, so the consensus check uses the floor (sub-sat/vB precision is intentionally not enforced).

6.If low ≤ fee_rate ≤ high → SATISFIED; else → UNSATISFIED

Return Values

Condition	Result
Fewer than 2 NUMERIC fields, or either undecodable	ERROR
Missing tx / spent_outputs / tx_weight context, or vsize ≤ 0	ERROR
`high < 0`, `low < 0`, or `low > high`	UNSATISFIED
`fee < 0` (outputs exceed inputs)	UNSATISFIED
`fee_rate` below `low` or above `high`	UNSATISFIED
`low ≤ fee_rate ≤ high`	SATISFIED

JSON Wire Format

Conditions (fee band 5-50 sat/vB)

{
  "type": "HYSTERESIS_FEE",
  "inverted": false,
  "fields": [
    { "type": "NUMERIC", "value": 50 },
    { "type": "NUMERIC", "value": 5 }
  ]
}

This creates a fee rate band of 5-50 sat/vB. Transactions with fee rates outside this range will fail the block check.

Use Cases

Fee Overpay Prevention

Covenant-locked UTXOs enforce a maximum fee rate, preventing accidental or malicious fee overpayment when spending from shared or automated wallets.

Fee Band Enforcement

Institutional treasury outputs can only be spent within a reasonable fee band, ensuring transactions are neither too cheap (risk of non-confirmation) nor too expensive.

Economic Constraint on Spending

Combined with other PLC blocks, fee hysteresis creates economic guardrails that prevent value extraction through inflated fees in automated covenant chains.

← DATA_RETURN HYSTERESIS_VALUE →