> ## Documentation Index
> Fetch the complete documentation index at: https://docs.polygon.technology/llms.txt
> Use this file to discover all available pages before exploring further.
# Staking manager
> Contract reference for the StakeManager contract on Polygon PoS, covering validator management, staking, and reward distribution.
`StakeManager` is the main contract for validator-related activities including `checkPoint` signature verification, reward distribution, and stake management on Ethereum. Ownership is tracked via NFT IDs; transferring ownership or changing the signer does not affect system state.
Stakers are divided into validators, delegators, and watchers (for fraud reporting).
Source: [`StakeManager.sol`](https://github.com/0xPolygon/pos-contracts/blob/develop/contracts/staking/stakeManager/StakeManager.sol)
From a single Ethereum address, a staker can only function as either a validator or a delegator (design choice, not a technical constraint).
## Validator admissions and replacement
### Admissions
The system allows a maximum of 105 active validators at any given time. New validators join the active set only when a currently active validator unbonds or is removed for low performance.
* Applications: [Polygon validators hub](https://polygoncommunity.typeform.com/validatorshub)
* Becoming a validator: [becoming-a-validator guide](/pos/get-started/becoming-a-validator/)
### Replacement
[PIP4](https://forum.polygon.technology/t/pip-4-validator-performance-management/9956) introduced validator performance management. Validators in an unhealthy state for an extended period are off-boarded; the slot is made available to the next in the waitlist.
* Performance requirements: [validator performance requirements](/pos/how-to/operate-validator-node/validator-performance/)
## Methods and variables
### `validatorThreshold`
Stores the maximum number of validators (slots) accepted by the system.
### `AccountStateRoot`
* Account root for validator and delegator accounting on Heimdall, submitted with each `checkpoint`.
* Used by `claimRewards` and `unStakeClaim`.
### `stake` / `stakeFor`
```solidity title="StakeManager.sol" theme={null}
function stake(
uint256 amount,
uint256 heimdallFee,
bool acceptDelegation,
bytes calldata signerPubkey
) public;
function stakeFor(
address user,
uint256 amount,
uint256 heimdallFee,
bool acceptDelegation,
bytes memory signerPubkey
) public;
```
* Allows staking if `amount` exceeds `minDeposit` and `currentValidatorSetSize` is less than `validatorThreshold`.
* Requires transfer of `amount + heimdallFee`.
* `updateTimeLine` updates the timeline data structure tracking active validators and stake per epoch/checkpoint.
* Mints one unique NFT per `stake` or `stakeFor` call (one NFT per Ethereum address).
* Setting `acceptDelegation` to `true` deploys a `ValidatorShare` contract for the validator.
### `unstake`
* Removes validator from validator set in the next epoch.
* Updates the timeline data structure; records exit epoch.
* If delegation is active, collects all rewards and locks the delegation contract against new delegations.
### `unstakeClaim`
```solidity theme={null}
function unstakeClaim(uint256 validatorId) public;
```
After `WITHDRAWAL_DELAY` period, validators call this function to settle with `stakeManager`: collect remaining rewards, retrieve staked tokens, and burn the NFT.
### `restake`
```solidity theme={null}
function restake(uint256 validatorId, uint256 amount, bool stakeRewards) public;
```
* Allows validators to increase stake using new tokens, accumulated rewards, or both.
* Updates the timeline for active stake.
### `withdrawRewards`
```solidity theme={null}
function withdrawRewards(uint256 validatorId) public;
```
Withdraws accumulated rewards for a validator. If the validator accepts delegation, rewards from the delegation contract are also included.
### `updateSigner`
```solidity theme={null}
function updateSigner(uint256 validatorId, bytes memory signerPubkey) public
```
Updates the signer address used to validate blocks on Polygon and checkpoint signatures on `stakeManager`.
### `topUpForFee`
```solidity theme={null}
function topUpForFee(uint256 validatorId, uint256 heimdallFee) public;
```
Tops up a validator's Heimdall fee balance.
### `claimFee`
```solidity theme={null}
function claimFee(
uint256 validatorId,
uint256 accumSlashedAmount,
uint256 accumFeeAmount,
uint256 index,
bytes memory proof
) public;
```
Withdraws fees from Heimdall. `accountStateRoot` is updated on each checkpoint; validators provide a proof of inclusion in this root to withdraw fees. `accountStateRoot` is re-written per checkpoint to prevent double exits.
### Staking NFT
Standard ERC721 contract with one token per user, minted sequentially.
### `checkSignatures`
```solidity theme={null}
function checkSignatures(
uint256 blockInterval,
bytes32 voteHash,
bytes32 stateRoot,
bytes memory sigs
) public;
```
* Called by the RootChain contract when submitting checkpoints.
* Validates unique signatures and checks for $2/3+1$ stake weight on `voteHash`.
* `currentValidatorSetTotalStake` provides the current active stake.
* Rewards are distributed proportionally to validator stake.
### `isValidator`
Checks whether a given validator is active in the current epoch.
## Timeline data structure
```solidity theme={null}
struct State {
int256 amount;
int256 stakerCount;
}
mapping(uint256 => State) public validatorState;
```
## `StakingInfo`
Centralized logging contract for validator and delegation events. Includes read-only functions.
Source: [`StakingInfo.sol`](https://github.com/0xPolygon/pos-contracts/blob/develop/contracts/staking/StakingInfo.sol)
## `ValidatorShareFactory`
Factory contract that deploys a `ValidatorShare` contract for each validator that opts into delegation.
Source: [`ValidatorShareFactory.sol`](https://github.com/0xPolygon/pos-contracts/blob/develop/contracts/staking/validatorShare/ValidatorShareFactory.sol)