> For the complete documentation index, see [llms.txt](https://docs.axis.to/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.axis.to/susdx-the-rewards-vault/susdx.md).

# What is sUSDx?

sUSDx is **the Axis Rewards Vault**, the staking rewards vault of the protocol. Staking **USDx, the Axis Dollar** (a synthetic dollar), into the vault makes a holder **eligible for the protocol's incentive reward distributions**, and in return you receive sUSDx, a tokenized position in the vault whose value grows as rewards accrue to it. Rewards accrue directly to the staking contract, so the amount of USDx each sUSDx represents rises over time **with no further action required**. You are never required to rebase or claim, and the reward accrues into the position itself.

Those rewards are **discretionary and forward-looking**, a signal of what the protocol is willing to pay for capital (a capital cost), **unbundled** from the reserve yield rather than a direct pass-through of it. The reserves may grow or contract with little direct relationship to the rewards available in the vault. How rewards are funded and vest is covered in [How Rewards Reach sUSDx](/susdx-the-rewards-vault/reward-distribution.md).

## The vault in one line

sUSDx is the share token of an **ERC-4626 vault** (`StakedUSDx`) whose underlying asset is USDx. One sUSDx is a claim on a growing amount of USDx:

$$
\text{USDx per sUSDx} = \frac{\text{vault assets (incl. vested rewards)}}{\text{total sUSDx supply}}
$$

## How a share accrues value

The vault's returns come from **Axis's structural edge in cross-venue and cross-asset fragmentation**, a durable, market-neutral yield source that does not rely on any single mechanism, with Axis's trading engine capturing pricing differences across venues and assets offchain (see [How Axis Earns Yield](/susdx-the-rewards-vault/how-axis-earns-yield.md)). Funding is one component (and can be the larger share in a given period); see the Transparency Dashboard for current attribution. Market-neutral arbitrage, capturing price differences while hedging out market direction, is an established institutional trading strategy, not a crypto invention. Realized results are delivered to the vault as USDx rewards by the reward manager (`fundRewards`, gated by `REWARD_MANAGER_ROLE`). The backing behind the yield is evidenced separately. See [Backing, Custody & Transparency](/backing-reserves-and-transparency/backing-custody-transparency.md).

Rewards do **not** hit the share price all at once. They **vest linearly over a configured window**. The live value is a configured parameter of the deployed contract, and only the vested portion counts toward vault assets. So the exchange rate rises smoothly as rewards vest, rather than jumping on each funding, which also means a large deposit can't front-run a reward and capture it instantly.

Your sUSDx balance never changes; each token simply comes to represent more USDx.

By design, the vault's accounting only ever vests **positive or flat** rewards into the exchange rate: rewards are added when they are funded and vest forward over the window, so the intended behaviour is for the USDx-per-sUSDx rate to rise or hold steady rather than step down on each funding. This is a description of how vesting works, not a promise that the rate can never fall. Separately, the protocol is designed to be **over-collateralized**: backing is intended to exceed outstanding USDx, so that this buffer can **absorb contractions in the reserves** rather than passing them straight through to stakers. The buffer is a design intent, sized against reserves; it is not a named guarantee fund, and it does not remove the risks described below.

## Staking and redeeming

* **Stake.** Deposit USDx and receive sUSDx immediately, priced at the current exchange rate.
* **Request redemption.** Redemption is **asynchronous** (ERC-7540): you `requestRedeem` your shares, which burns them and opens a request subject to a per-policy **cooldown**, currently **7 days**.
* **Wait and claim.** Once the cooldown elapses, the request is serviced. An account holding `REDEMPTION_SERVICER_ROLE` calls `serviceRedemptions` to mark it claimable, after which you claim the underlying USDx.
* **Change your mind.** A request can be **cancelled while it is still pending** (`cancelRedeemRequest`), which restores the burned shares.

Amounts reserved for pending and claimable redemptions are tracked as vault liabilities, so the vault can always weigh what it holds against what it owes.

## Two different price questions

| Question                                    | Measure                              |
| ------------------------------------------- | ------------------------------------ |
| How much USDx does one sUSDx represent?     | Vault exchange rate                  |
| How many US dollars is that position worth? | USDx market price × USDx represented |

An increasing exchange rate does not prevent a loss in dollar terms if USDx trades below its target or cannot be exited on expected terms.

## Yield is not fixed

The vault promises no fixed rate. Realized return depends on whether strategy returns are generated, whether they are delivered to the vault, when rewards vest, and the exchange rate at which you enter and exit. A period with no new rewards creates no yield by itself, and past returns do not determine future ones.

## Key risks

sUSDx holders keep every risk of USDx and add vault-specific ones, smart contract risk, dependence on reward delivery, and redemption delay (your assets are not liquid until a request is serviced). See [Risk Overview](/risk/risk-overview.md) and the [Stake & Unstake guide](/susdx-the-rewards-vault/stake-and-unstake.md).


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