> For the complete documentation index, see [llms.txt](https://docs.mosaicgalaxy.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.mosaicgalaxy.io/documentation/mosaic-chain/architecture-and-technology/actors-validators-and-delegators/pos-validators.md).

# PoS Validators

PoS (Proof of Stake) Validators are **solo validators** who secure Mosaic Chain by running validator nodes and producing blocks. They stake exclusively via their Validator NFT's nominal value and operate independently without accepting delegations.

***

### **What PoS Validators Do**

PoS Validators are active participants in Mosaic Chain's consensus mechanism.

**Core responsibilities:**

* ✅ Run full validator nodes
* ✅ Produce new blocks (if selected by the subset algorithm)
* ✅ Validate transactions and maintain network security
* ✅ Stake via their Validator NFT's nominal value
* ✅ Earn block rewards and transaction fees

**In Polkadot terms:**

* Mosaic validators are technically **collators** (they collect transactions and produce blocks for the Polkadot relay chain to finalize)
* However, within Mosaic Chain's internal consensus, they function as **validators**

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### **How Staking Works for PoS Validators**

PoS Validators have a unique staking model:

**Staking:**

* ✅ Stake **only via their Validator NFT's nominal value**
* ❌ **Cannot stake MOS coins**
* ❌ **Cannot accept delegations from others**

**Why this limitation?**

* PoS Validators are designed for **solo operation**
* Simpler setup with no delegation management
* Full control over their own stake and rewards

***

### **Requirements to Become a PoS Validator**

To participate as a PoS Validator, you must:

1. **Own and bind a PoS Validator NFT** - Grants permission to validate and represents your stake
2. **Run a validator node** - Using Validator OS (plug-and-play system)
3. **Maintain uptime** - Keep your node online and synced 24/7
4. **Be selected by the subset algorithm** - \~200 validators are randomly selected each session (1 hour)

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### **PoS Validator NFTs**

The **PoS Validator NFT** represents both your permission to validate and your stake.

**Key features:**

* **Nominal value** - The NFT's nominal value is your stake (subject to slashing)
* **Transferable** - Can be sold or transferred to another account
* **Binding required** - Must be bound to your account to participate
* **Unbinding conditions** - Can only unbind if validator is chilled, not active, and the staking contract has ended

**Your stake = Your NFT's nominal value**

Unlike DPoS Validators who can add MOS coins to their stake, PoS Validators stake exclusively through their NFT's nominal value.

***

### **Rewards**

PoS Validators earn rewards from two sources:

#### **1. Block Rewards**

* Newly minted MOS coins (calculated via expansion formula)
* Distributed at the end of each session to active validators

#### **2. Transaction Fees**

* **50% of transaction fees** go to the block producer
* **100% of tips** go to the block producer
* **40% of fees are burnt** (removed from circulation)
* **10% of fees go to the Treasury**

**Reward distribution:**

* Rewards are distributed at the end of each **session** (1 hour ≈ 600 blocks)
* Only **active validators** (selected for that session) earn rewards
* PoS Validators keep **100% of their rewards** (no commission sharing)

***

### **Slashing & Auto-Chilling**

PoS Validators can be slashed for poor behavior or downtime.

#### **Slashing**

**What gets slashed:**

* **Validator NFT's nominal value** (0.1% of nominal value per slashing event)

**Slashing triggers:**

* Extended downtime
* Double-signing blocks
* Other malicious behavior

#### **Auto-Chilling**

Validators are automatically removed from the active set if:

1. **Slashed in two consecutive sessions**
2. **Validator NFT's nominal value drops below 80% of its initial value**

**Recovery:**

* Validators can unchill manually
* Validators must **top up their NFT's nominal value** to resume validation if it has dropped below 80% of its initial value
* After topping up, they can rejoin the waiting set

***

**Learn more:**

* [DPoS Validators →](/documentation/mosaic-chain/architecture-and-technology/actors-validators-and-delegators/dpos-validators.md) - Compare with delegation-accepting validators
* [Delegators (Stakers) →](/documentation/mosaic-chain/architecture-and-technology/actors-validators-and-delegators/delegators-stakers.md) - Learn about passive staking

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