PegKeeper¶

crvUSD-style Curve StableSwap-NG peg defender. Mints/deposits TARE when pool price above $1; withdraws/burns when below.

Source: TARE-Stablecoin/src/peg_keeper.vy (Vyper 0.4.3)

Curve pool (Sepolia): 0xcBa8532fb8c16B7c193977e1A76E49fd06142d54 — address book

Concept guide: PegKeeper protocol page

Implementation overview¶

Above peg — mint TARE (minter role), single-sided add_liquidity → increase pool supply, push price down.
Below peg — remove_liquidity_one_coin + burn TARE (up to debt previously provided) → reduce supply, lift price.
Partial correction — each update() moves 1/5 of imbalance (CORRECTION_DIVISOR = 5).
Rate limit — ACTION_DELAY 15 min between state-changing ops.
Minter bound — debt_ceiling + engine grants minter via set_peg_keeper.

flowchart LR
    PK[PegKeeper] --> Pool[Curve NG pool]
    PK -->|mint/burn| TARE[TareToken]
    Engine[TareEngine] -->|set_peg_keeper| PK

Immutables¶

Name	Role
`POOL`	Curve StableSwap-NG pool
`TARE` / `PEGGED`	TARE token
`I` / `I_OTHER`	TARE vs paired stable coin indices
`PAIRED_DECIMALS`	Paired stable decimals for balance normalization

Events¶

Event	When
`Provided`	TARE minted into pool
`Withdrawn`	TARE removed and burned
`DebtCeilingUpdated`	Admin changes ceiling
`SlippageSet`	Slippage tolerance updated
`AdminSet`	Admin transferred

Admin¶

`set_debt_ceiling`¶

PegKeeper.set_debt_ceiling(new_ceiling)

Sets max TARE the keeper may have outstanding in the Curve pool (debt). Caps mint-and-provide peg defense.

Param	Type	Description
`new_ceiling`	`uint256`	Max outstanding TARE debt (18 decimals)

Returns / state: Writes debt_ceiling.

Access: admin only.

Events: DebtCeilingUpdated(ceiling=new_ceiling).

Source (TARE-Stablecoin/src/peg_keeper.vy:160-167):

@external
def set_debt_ceiling(new_ceiling: uint256):
    assert msg.sender == self.admin, "PegKeeper: not admin"
    self.debt_ceiling = new_ceiling
    log DebtCeilingUpdated(ceiling=new_ceiling)

Example:

peg_keeper.set_debt_ceiling(1_000_000 * 10**18)

Cross-links: update · TareEngine set_peg_keeper

`set_slippage_bps`¶

PegKeeper.set_slippage_bps(new_bps)

Sets min-out slippage tolerance for pool provide/withdraw ops. Hard-capped at MAX_SLIPPAGE_BPS (1000 = 10%).

Param	Type	Description
`new_bps`	`uint256`	Slippage tolerance in basis points

Returns / state: Writes slippage_bps. Drives non-zero min_mint_amount / min_received on Curve calls.

Access: admin only. new_bps <= MAX_SLIPPAGE_BPS.

Events: SlippageSet(slippage_bps=new_bps).

Source (TARE-Stablecoin/src/peg_keeper.vy:170-182):

@external
def set_slippage_bps(new_bps: uint256):
    assert msg.sender == self.admin, "PegKeeper: not admin"
    assert new_bps <= MAX_SLIPPAGE_BPS, "PegKeeper: slippage too high"
    self.slippage_bps = new_bps
    log SlippageSet(slippage_bps=new_bps)

Example:

peg_keeper.set_slippage_bps(50)  # 0.5% min-out floor

Cross-links: update · set_debt_ceiling

`set_admin`¶

PegKeeper.set_admin(new_admin)

Transfers keeper admin rights (debt ceiling, slippage config). Typically engine owner.

Param	Type	Description
`new_admin`	`address`	New admin address (non-zero)

Returns / state: Writes admin.

Access: current admin only.

Events: AdminSet(admin=new_admin).

Source (TARE-Stablecoin/src/peg_keeper.vy:185-193):

@external
def set_admin(new_admin: address):
    assert msg.sender == self.admin, "PegKeeper: not admin"
    assert new_admin != empty(address), "PegKeeper: zero admin"
    self.admin = new_admin
    log AdminSet(admin=new_admin)

Cross-links: set_debt_ceiling · set_slippage_bps

Keeper¶

`update`¶

PegKeeper.update() -> uint256

Permissionless peg nudge. Corrects 1/5 of pool imbalance: mint+provide when TARE scarce (above peg), withdraw+burn when abundant (below peg). EMA price gate prevents flash-manipulation mints.

Param	Type	Description
—	—	No inputs

Returns: uint256 — TARE provided (mint direction) or withdrawn (burn direction); 0 if no action.

State: May update debt, last_change. Respects ACTION_DELAY (15 min), debt_ceiling, slippage_bps.

Access: anyone. Reverts if called too soon after last action.

Events: Provided or Withdrawn when change > 0.

Source (TARE-Stablecoin/src/peg_keeper.vy:200-243):

@external
def update() -> uint256:
    assert block.timestamp >= self.last_change + ACTION_DELAY, "PegKeeper: too soon"
    p_tare: uint256 = self._tare_price()  # EMA guard
    if balance_pegged > balance_other and p_tare <= PRECISION:
        change = self._withdraw((balance_pegged - balance_other) // CORRECTION_DIVISOR)
    elif balance_other > balance_pegged and p_tare >= PRECISION:
        change = self._provide((balance_other - balance_pegged) // CORRECTION_DIVISOR)
    if change > 0:
        self.last_change = block.timestamp
    return change

Example:

# Keeper bot — max once per 15 min
amount = peg_keeper.update()

Cross-links: tare_price · peg_deviation_bps · estimate_update · TareToken API

Views¶

`tare_price`¶

PegKeeper.tare_price() -> uint256

TARE's Curve pool EMA price in paired-stable terms (18-decimal; 1e18 = $1 target).

Param	Type	Description
—	—	No inputs

Returns: uint256 — USD value of 1 TARE from POOL.price_oracle(0), oriented via coin index I.

State: None (view). Uses manipulation-resistant EMA, not spot balances.

Access: anyone (@view).

Events: None.

Source (TARE-Stablecoin/src/peg_keeper.vy:322-338):

@external
@view
def tare_price() -> uint256:
    raw: uint256 = staticcall POOL.price_oracle(0)
    if I == 1:
        return raw
    return PRECISION * PRECISION // raw

Example:

price = peg_keeper.tare_price()
above_peg = price > 10**18

Cross-links: peg_deviation_bps · update · estimate_update

`peg_deviation_bps`¶

PegKeeper.peg_deviation_bps() -> uint256

Absolute TARE peg deviation from $1 in basis points (pool EMA).

Param	Type	Description
—	—	No inputs

Returns: uint256 — |price - 1e18| / 1e18 × 10_000 bps.

State: None (view). Uses _tare_price() internally.

Access: anyone (@view).

Events: None.

Source (TARE-Stablecoin/src/peg_keeper.vy:341-348):

@external
@view
def peg_deviation_bps() -> uint256:
    price: uint256 = self._tare_price()
    if price >= PRECISION:
        return (price - PRECISION) * 10_000 // PRECISION
    return (PRECISION - price) * 10_000 // PRECISION

Example:

bps = peg_keeper.peg_deviation_bps()  # 50 => 0.5% off peg

Cross-links: tare_price · update

`estimate_update`¶

PegKeeper.estimate_update() -> (bool, uint256)

Preview next update() direction and size from pool balances. Does not apply EMA gate or ACTION_DELAY — dry-run sizing only.

Param	Type	Description
—	—	No inputs

Returns: (is_provide, amount) — True = mint/provide path; False = withdraw/burn. amount = TARE that would move (withdraw capped at debt).

State: None (view).

Access: anyone (@view).

Events: None.

Source (TARE-Stablecoin/src/peg_keeper.vy:360-378):

@external
@view
def estimate_update() -> (bool, uint256):
    if balance_pegged > balance_other:
        return (False, min((balance_pegged - balance_other) // CORRECTION_DIVISOR, self.debt))
    if balance_other > balance_pegged:
        return (True, (balance_other - balance_pegged) // CORRECTION_DIVISOR)
    return (True, 0)

Example:

is_provide, amount = peg_keeper.estimate_update()

Cross-links: update · peg_deviation_bps

PegKeeper¶

Implementation overview¶

Immutables¶

Events¶

Admin¶

set_debt_ceiling¶

set_slippage_bps¶

set_admin¶

Keeper¶

update¶

Views¶

tare_price¶

peg_deviation_bps¶

estimate_update¶

`set_debt_ceiling`¶

`set_slippage_bps`¶

`set_admin`¶

`update`¶

`tare_price`¶

`peg_deviation_bps`¶

`estimate_update`¶