FIFA World Cup 2026

⛓️ Parametric Settlement Architecture

🦀 Anchor Rust Implementation

Here is the core Anchor code of the custom Escrow Program executing CPI settlement into TxLINE's validate_stat instruction:

use anchor_lang::prelude::*;
use anchor_lang::solana_program::instruction::Instruction;

declare_id!("PrEd1ct10nMarketEscrow111111111111111111");

#[program]
pub mod prediction_escrow {
    use super::*;

    pub fn place_prediction(ctx: Context<PlacePrediction>, outcome: u8, amount: u64) -> Result<()> {
        let prediction = &mut ctx.accounts.prediction;
        prediction.predictor = ctx.accounts.user.key();
        prediction.outcome = outcome;
        prediction.amount = amount;
        prediction.settled = false;

        // Transfer funds to the escrow PDA
        anchor_lang::system_program::transfer(
            CpiContext::new(
                ctx.accounts.system_program.to_account_info(),
                anchor_lang::system_program::Transfer {
                    from: ctx.accounts.user.to_account_info(),
                    to: ctx.accounts.escrow_pda.to_account_info(),
                },
            ),
            amount,
        )?;
        Ok(())
    }

    pub fn settle_prediction(
        ctx: Context<SettlePrediction>,
        proof: Vec<[u8; 32]>,
        expected_root: [u8; 32],
    ) -> Result<()> {
        let prediction = &mut ctx.accounts.prediction;
        require!(!prediction.settled, ErrorCode::AlreadySettled);

        // 1. Prepare Cross-Program Invocation (CPI) into TxLINE validation program
        // TxLINE Program ID: 6pW64gN1s2uqjHkn1unFeEjAwJkPGHoppGvS715wyP2J
        let txline_program_info = ctx.accounts.txline_program.to_account_info();
        
        // CPI accounts required by TxLINE validate_stat instruction
        let accounts = vec![
            AccountMeta::new_readonly(ctx.accounts.txline_state.key(), false),
            AccountMeta::new_readonly(ctx.accounts.txline_proof_registry.key(), false),
        ];

        // 2. Build validate_stat instruction data
        // Verify that the match outcome (leaf hash) is present in the verified root
        let mut data = vec![];
        data.extend_from_slice(&expected_root);
        for node in proof {
            data.extend_from_slice(&node);
        }

        let cpi_instruction = Instruction {
            program_id: txline_program_info.key(),
            accounts,
            data,
        };

        // 3. Invoke TxLINE validation on-chain
        anchor_lang::solana_program::program::invoke(
            &cpi_instruction,
            &[
                ctx.accounts.txline_state.to_account_info(),
                ctx.accounts.txline_proof_registry.to_account_info(),
            ],
        )?;

        // 4. Verification succeeded - Release Escrow
        prediction.settled = true;
        let payout = prediction.amount * 2; // Example 1:1 odds pool multiplier
        
        let escrow_seeds = &[
            b"escrow",
            ctx.accounts.escrow_pda.owner.as_ref(),
            &[ctx.bumps.escrow_pda],
        ];
        let signer = &[&escrow_seeds[..]];

        anchor_lang::system_program::transfer(
            CpiContext::new_with_signer(
                ctx.accounts.system_program.to_account_info(),
                anchor_lang::system_program::Transfer {
                    from: ctx.accounts.escrow_pda.to_account_info(),
                    to: ctx.accounts.winner.to_account_info(),
                },
                signer,
            ),
            payout,
        )?;

        Ok(())
    }
}

#[derive(Accounts)]
pub struct PlacePrediction<'info> {
    #[account(mut)]
    pub user: Signer<'info>,
    #[account(
        init,
        payer = user,
        space = 8 + 32 + 1 + 8 + 1,
        seeds = [b"prediction", user.key().as_ref()],
        bump
    )]
    pub prediction: Account<'info, PredictionState>,
    #[account(mut, seeds = [b"escrow"], bump)]
    pub escrow_pda: SystemAccount<'info>,
    pub system_program: Program<'info, System>,
}

#[derive(Accounts)]
pub struct SettlePrediction<'info> {
    #[account(mut)]
    pub prediction: Account<'info, PredictionState>,
    #[account(mut, seeds = [b"escrow"], bump)]
    pub escrow_pda: SystemAccount<'info>,
    #[account(mut)]
    pub winner: SystemAccount<'info>,
    /// CHECK: Target TxLINE Solana validation program
    pub txline_program: UncheckedAccount<'info>,
    /// CHECK: Signed state account containing root
    pub txline_state: UncheckedAccount<'info>,
    /// CHECK: Merkle Registry account containing valid indices
    pub txline_proof_registry: UncheckedAccount<'info>,
    pub system_program: Program<'info, System>,
}

#[account]
pub struct PredictionState {
    pub predictor: Pubkey,
    pub outcome: u8,
    pub amount: u64,
    pub settled: bool,
}

#[error_code]
pub mod ErrorCode {
    #[msg("This prediction has already been settled.")]
    AlreadySettled,
}