Fuel and Emissions

XRB is the network token that powers both sides of SCL execution: contracts stake and burn it to pay for the compute and storage they consume, and validators earn it for verifying every execution. This page covers the mechanism as it applies to nodes and validators; the full economic model lives in Tokenomics.

Fuel: metering and burning

Every SCL execution is metered. The VM counts each instruction as it runs, records cross-contract calls, and tracks net storage written. There is no per-opcode gas table: one opcode is one instruction, which keeps replay deterministic and cheap for validators.

Every call gets a free envelope: 200 instructions, 1 cross-contract hop, 1 KB of net-new storage. A plain token transfer runs about 65 instructions, so single basic operations (transfers, simple mints, balance updates) are free, for every user, forever. What pays is complexity: multi-hop composition, batch compute, and bulk state growth.

Staking tiers

Contracts stake XRB to set their execution capacity. The stake is refundable on wind-down and doubles as the reserve that charges burn against, so it works like a prepaid fuel tank:

An unstaked contract can never owe anything: it simply halts at the envelope if it attempts complex work.

What burns

Past the free envelope, execution burns XRB outright: 0.001 XRB per 1,000 instructions, 0.001 XRB per extra cross-contract hop, and 0.01 XRB per KB of bulk storage (deletions credit). Every charge is capped at 1% of the contract's stake, so the worst case per call is always bounded and predictable.

The two cost dimensions pull in different directions by design. Complexity burns: batch compute and deep call chains pay as they run. Growth locks: organic user growth burns nothing but steadily fills a tier's storage quota, pushing the contract up a tier. A project pays in refundable lockup as it grows, and in burn only when it does complex work.

A contract that runs out of fuel is not switched off; it degrades to the free envelope. Plain operations (transfers, balance reads) keep working forever, so holders of a token can always move their money out. Only the contract's complex logic halts until its fuel balance is topped up.

Burned XRB is destroyed permanently. Cumulative burn is governed by a burn-budget rule, a pure function of total supply that every validator reproduces identically from chain state: burn per execution decays as cumulative burn grows, total burn can never exceed 40% of supply, and total supply can never fall below the 300M floor.

Validator emissions

Validators replay every contract execution deterministically and verify SCL state against Bitcoin. Validation rounds are seeded from Bitcoin block hashes, so validator selection is anchored to the same chain the contracts are.

Rewards come from a dedicated validator emission pool of 40,000,000 XRB (8% of supply). The validator coordinator releases the pool as a steady per-block drip anchored to Bitcoin:

Validators stake XRB to participate in validation rounds and earn from the pool in proportion to the validation work they perform. Alongside emission, fee flows from SCL products (swap fees, DEX trading fees, treasury and minting fees) are routed to validators, so validator revenue outlives the pool.

Emission never exceeds 1.6% of supply in any year, and once the pool closes in early 2031, issuance ends permanently. From that point, every burned token is a net reduction in supply: stake lockups and fuel burns both pull liquid supply down as network usage grows.