## Week 20 and Week 21 Updates:

### Progress on ePBS Implementation:

#### All-in-one Fork Choice Analysis

Key Components:

type AvailabilityCommittee struct {
    Validators    []ValidatorIndex
    VotingPeriod  uint64    // 7 seconds into slot
    Threshold     uint64    // Majority threshold
}

type BlockBranch struct {
    Empty bool      // B_empty: Block without payload
    Full  bool      // B_full: Block with payload
    Root  Root      // Block root
}

Major Improvements:
- Unifies fork choice rules for ePBS, FOCIL, and DAS
- Eliminates need for complex builder boost mechanisms
- Introduces staged release of block data
- Simplifies payment processing logic

#### Critical Technical Challenges

**Withdrawal Handling Issue:**

// Current Challenge
func get_expected_withdrawals(state BeaconState) error {
    if !is_parent_full(state) {
        return ErrIndeterminateWithdrawals
    }
    // Process withdrawals
}

**Proposed Solutions:**

1. Client-side Caching:

type BeaconNode struct {
    withdrawalCache map[Root][]Withdrawal
}

func (bn *BeaconNode) GetWithdrawals(blockRoot Root) []Withdrawal {
    return bn.withdrawalCache[blockRoot]
}

2. State-level Caching:

type BeaconState struct {
    WithdrawalsCache []Withdrawal  // Instead of just root
}

**Builder Staking Security:**

Current Risk:

type Builder struct {
    Balance uint64
    // Can potentially drain balance after bidding
}

Proposed Solutions:

// Option 1: Execution Request Based
type BuilderBid struct {
    MaxBid      uint64
    ValidUntil  uint64
}

// Option 2: Excess Balance Only
type Builder struct {
    MinStake    uint64  // 1 ETH
    ExcessLimit uint64  // Maximum bid allowed
}

### Implementation Progress

Fork Choice Updates:

func (f *ForkChoice) ProcessBlock(block *BeaconBlock) error {
    // New dual-branch handling
    empty := createEmptyBranch(block)
    full := createFullBranch(block)
    
    // Process AC votes
    if hasACMajority(block) {
        return f.processFull(full)
    }
    return f.processEmpty(empty)
}

### Focus for next 2 weeks

Technical Priorities:
- Implement client-side withdrawal caching
- Develop builder stake management system
- Update validator specifications
- Create test scenarios for empty block handling

#### Outstanding Questions

Builder Security:
- How to handle builder slashing?
- What's the optimal minimum stake?
- How to prevent stake drainage attacks?

Withdrawal Handling:
- Performance implications of caching
- Race condition prevention
- State bloat considerations

#### Client Implementation Status

**Prysm:**

// New implementations needed
type BlockProduction struct {
    WithdrawalCache  cache.WithdrawalCache
    BuilderRegistry  registry.BuilderStakes
    ACVoteProcessor  votes.ACProcessor
}

**Other Clients:**
- Teku: Aligned with client-side caching approach
- Awaiting feedback from remaining clients

**Misc:**
- Presentation and final report for devcon