Solana — Integration Study & Sample Contract

Goal: learn Solana's development model (it is not an EVM chain — different mental model, language, and tooling), ship one sample on-chain program to devnet, and call it from a rabbit demo page.

Source: jay's request, 2026-07-17 (no source file). Motivation: every other on-chain item in rabbit/verex is EVM (Hyperliquid, Sepolia AA, x402-on-Base); Solana is the biggest non-EVM ecosystem and keeps appearing in the agent-payments space (e.g. "ETH, SOL" native-gas note in agentic-aa.md).

1. Research scope (short note before coding)

Write a compact EVM-dev-oriented comparison into this doc (or docs/knowledge/):

• Account model — programs are stateless; state lives in separate accounts passed into each instruction (vs EVM contract storage). Rent-exempt balances.
• PDAs (Program Derived Addresses) — program-owned accounts derived from seeds; the Solana idiom for mappings/escrow vaults.
• Transactions — every account an ix touches is declared up front (enables parallel execution); compute units instead of gas; priority fees.
• Token standard — SPL Token (+ Token-2022 extensions), associated token accounts — vs ERC-20's balance-in-contract model.
• Toolchain — Rust + Anchor framework (the de-facto Hardhat/Foundry of Solana), solana-test-validator for local dev, devnet faucet for deploy.

2. Sample contract (Anchor program) — ladder

1. Counter / guestbook program — classic first Anchor program: init a PDA account, an increment/post instruction, an Anchor TS test. Local validator → devnet deploy.
2. SPL escrow (small) — two-party escrow of an SPL token using a PDA vault: deposit → release/refund. Exercises PDAs, CPIs to the token program, and account constraints — the three things EVM devs actually need to learn.
3. (stretch) x402-flavored tie-in — the escrow as a "pay for data" leg mirroring the AP2/x402 loop in ap2-test.md, but settled in SPL tokens on devnet.

3. Rabbit surface

• Page: /etc/solana — connect Phantom (Solana wallet-adapter), show devnet SOL/SPL balance, one button per program instruction (increment / deposit / release), tx-signature links to Solana Explorer (devnet).
• Client stack: @solana/web3.js (or the newer @solana/kit) + wallet-adapter-react; Anchor's generated IDL/TS client for typed calls.
• Repo shape: Solana programs need their own Rust workspace — spagetties/solana/ (or a new top-level solana/ folder) with the Anchor project; only the page + IDL live in the Next.js app.

4. Estimate & sequencing

• Research note ~0.5d · Anchor counter on devnet ~1d · escrow ~1–2d · /etc/solana page ~1d → first cut = research note + counter + minimal page (~2–2.5d); escrow after.
• Independent of the EVM items — can slot anywhere; pairs well after agentic-aa.md for an "EVM vs Solana agent payments" perspective.

Status

Backlog / to do — not yet scheduled.