Money

Amounts on Bittensor come in two kinds of currency: TAO, the chain token, and alpha, of which every subnet has its own. They trade against each other in per-subnet pools, so an alpha amount is meaningless without knowing which subnet it belongs to — and 1 alpha on subnet 1 is not worth 1 alpha on subnet 2.

The Balance type

Balance is unit-tagged: every instance carries the netuid whose currency it denominates (netuid 0 is TAO). Arithmetic between different units raises UnitMismatchError instead of silently mixing currencies.

import bittensor as sub

sub.Balance.from_tao("10000000.123456789")   # exact TAO (str/Decimal for big amounts)
sub.Balance.from_alpha(2.5, netuid=42)       # subnet-42 alpha; prints with the subnet's
                                             # on-chain token symbol (α₄₂ before connect)
sub.tao(1.5); sub.alpha(2.5, 42); sub.rao(1_500_000_000)   # shorthands

Readback is unit-named too: .tao on a TAO balance, .alpha on an alpha balance — and .tao on an alpha balance raises rather than pretending the units are interchangeable. The base unit is rao: 1 TAO = 10⁹ rao.

Amount parameters

Intent fields are named by unit so there is no ambiguity about what a number means: amount_tao is TAO, amount_alpha is the subnet's alpha (the origin subnet for cross-subnet moves), *_rao is rao. Money fields that support it accept the string "all" — the concrete amount is resolved from chain state at build time (e.g. transfer, remove-stake).

Valuing stake

Alpha is never summed across subnets or silently treated as TAO. To value a coldkey's stake in TAO, use the stake-value-for-coldkey read: a spot price mark (alpha × price, excluding slippage and fees), pinned to one block. For what you would actually receive by exiting a position, simulate the swap with quote-unstake, which includes fees and slippage.

Slippage

Staking and unstaking are swaps against a pool, so the trade itself moves the price: your order consumes reserves as it fills, and the gap between what the spot price promised and what you actually receive grows with the trade's size relative to the pool's liquidity. Strictly, that self-inflicted gap is price impact; slippage is the further movement from other transactions landing before yours. The quotes account for the first, and the limit variants protect against both. The *-limit variants (add-stake-limit, remove-stake-limit) bound the execution price and fail instead of filling badly.

To turn a tolerance into a limit_price: when staking, ceiling = spot × (1 + tolerance); when unstaking, floor = spot × (1 − tolerance). At a spot price of 2.0 TAO (alpha-price), a 0.5% tolerance means 2.01 staking and 1.99 unstaking.

The same economics decide what is worth MEV-shielding. Root-subnet (netuid 0) staking is not a pool swap — it converts 1:1 with no swap fee and no price impact, so there is nothing for a front-runner to extract and shielding it buys nothing. Small swaps (well under ~1 TAO) are equally unattractive targets; the danger case is a large swap with a loose or absent limit price.

Swap fees

Every swap against a pool pays a fee of amount × FeeRate / 65535, where FeeRate is per-subnet and governance-settable (default 33 ≈ 0.05%). It is taken from the input side: TAO when staking, alpha when unstaking — and paid to the block author (an alpha-side fee is converted to TAO first). Moving stake between hotkeys within the same subnet is not a swap and pays no swap fee; a cross-subnet move runs two swaps but is charged the fee only once. The quote-stake / quote-unstake reads include it. This is distinct from the per-extrinsic transaction fee — see the transaction model.

Minimums

Two floors to know about:

• Existential deposit — 500 rao. An account whose balance drops below it is reaped: deactivated, with the remaining dust destroyed. Live value: existential-deposit.
• Minimum stake — staking operations below a chain-configured minimum (default 2,000,000 rao = 0.002 TAO, plus the swap fee on top) fail with AmountTooLow; unstakes are held to the same floor, both on the amount withdrawn and on any dust position left behind.

Supply

Every token is hard-capped at 21 million — TAO and each subnet's alpha alike. Total issuance is the chain's counter of what has been emitted and not recycled; it is what halving thresholds are measured against (emissions). Circulating supply is smaller: issuance includes tokens locked in pool reserves and staked positions.

Recycled vs burned

Both remove tokens from circulation, but not equivalently. Recycled tokens are subtracted from the chain's issuance counter, so the emission schedule can re-issue them later — neuron registration costs are recycled this way. Burned tokens stay counted in total issuance and are simply gone forever; nothing re-emits them. The distinction matters when reasoning about supply: recycling slows emission's approach to the cap, burning permanently retires supply. Transaction fees are neither — they are paid to the block author, not destroyed (fees).