BioMint-

        state.max_ltv_bps = max_ltv_bps;        state.mint_cap_usd = mint_cap_usd;        state.version = state.version.checked_add(1).unwrap();        state.updated_at = Clock::get()?.unix_timestamp;        Ok(())    }} #[derive(Accounts)]pub struct Initialize<'info> {    #[account(mut)]    pub admin: Signer<'info>,    #[account(        init,        payer = admin,        space = 8 + PolicyState::LEN,        seeds = [b"policy-state", admin.key().as_ref()],        bump    )]    pub policy_state: Account<'info, PolicyState>,    pub system_program: Program<'info, System>,} #[derive(Accounts)]

1. Line 39 state.version = state.version.checked_add(1).unwrap();: Uses checked arithmetic so overflow fails instead of wrapping.
2. Line 40 state.updated_at = Clock::get()?.unix_timestamp;: Reads on-chain time from the Clock sysvar.
3. Line 48 pub admin: Signer<'info>,: Requires this account to have signed the transaction.
4. Line 50 init,: Creates and pays for a new account. Space and payer must be specified.
5. Line 53 seeds = [b"policy-state", admin.key().as_ref()],: Declares the PDA seeds. Anchor re-derives the address and rejects the account if it doesn't match.
6. Line 54 bump: Uses the bump seed, the extra byte that pushes the derived address off the ed25519 curve.

        record.evaluation_count = record.evaluation_count.checked_add(1).unwrap_or(u32::MAX);        record.improvement_count = record.improvement_count.checked_add(1).unwrap_or(u32::MAX);         emit!(ImprovementSettled {            dataset_record: ctx.accounts.dataset_record.key(),            buyer: ctx.accounts.buyer.key(),            contributor: ctx.accounts.contributor.key(),            delta_bps,            payment_lamports,            timestamp: Clock::get()?.unix_timestamp,        });         Ok(())    }     // ── No-improvement recording ─────────────────────────────────────────────     /// Record an evaluation where the dataset did NOT improve the model.    ///    /// No payment occurs.  This still updates on-chain stats so buyers can    /// see the evaluation-to-improvement ratio of a listing.    pub fn record_no_improvement(ctx: Context<RecordEvaluation>) -> Result<()> {        let record = &mut ctx.accounts.dataset_record;        require!(record.status == ListingStatus::Listed, DataMarketError::NotListed);

1. Line 121 record.evaluation_count = record.evaluation_count.checked_add(1).unwrap_or(u32::MAX);: Uses checked arithmetic so overflow fails instead of wrapping.
2. Line 124 emit!(ImprovementSettled {: Emits an Anchor event that clients can parse from the logs.
3. Line 130 timestamp: Clock::get()?.unix_timestamp,: Reads on-chain time from the Clock sysvar.
4. Line 144 require!(record.status == ListingStatus::Listed, DataMarketError::NotListed);: An explicit validation that aborts the instruction with an error.

} /** * Build and sign a Solana SOL transfer for an x402 payment requirement. * * @param {object} requirement   - { payTo, maxAmountRequired, asset, network } * @param {Keypair} payer * @param {Connection} connection * @returns {Promise<string>}  Base64-encoded signed transaction */async function buildX402Payment(requirement, payer, connection) {  const { payTo, maxAmountRequired } = requirement;   // maxAmountRequired is in lamports for SVM networks  const amountLamports = Number(maxAmountRequired);   const recipient = new PublicKey(payTo);  const { blockhash, lastValidBlockHeight } = await connection.getLatestBlockhash("finalized");   const tx = new Transaction({    feePayer: payer.publicKey,    blockhash,    lastValidBlockHeight  }).add(

1. Line 52 * Build and sign a Solana SOL transfer for an x402 payment requirement.: Uses x402, an HTTP 402 pattern where an agent pays per request with an on-chain payment.
2. Line 66 const { blockhash, lastValidBlockHeight } = await connection.getLatestBlockhash("finalized: Fetches a recent blockhash. Transactions expire if it gets too old.

    if (!swapRes.ok) {      const txt = await swapRes.text();      return { skipped: false, error: `Jupiter swap error ${swapRes.status}: ${txt.slice(0, 200)}` };    }     const { swapTransaction } = await swapRes.json();     // ── 3. Sign + send ──────────────────────────────────────────────────────    const connection = new Connection(rpcUrl, "confirmed");    const txBuf = Buffer.from(swapTransaction, "base64");    const tx = VersionedTransaction.deserialize(txBuf);    tx.sign([admin]);     const signature = await connection.sendTransaction(tx, {      skipPreflight: false,      maxRetries: 3    });     const latest = await connection.getLatestBlockhash();    await connection.confirmTransaction(      { signature, blockhash: latest.blockhash, lastValidBlockHeight: latest.lastValidBlockHeight },      "confirmed"    );

1. Line 158 const signature = await connection.sendTransaction(tx, {: Submits the signed transaction to the cluster.
2. Line 163 const latest = await connection.getLatestBlockhash();: Fetches a recent blockhash. Transactions expire if it gets too old.