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If you have made it this far in 100 Days of Solana, you have been working in JavaScript and on the command line. You have been calling RPC methods, building instructions, signing transactions, and reading and writing account data in JavaScript, and most recently minting and sending tokens and NFTs from the CLI. Either way, you have been driving Solana with tools that let you assign a value and move on with your life. Soon the ground shifts. You are going to open a file called lib.rs , and it is going to be Rust, and for a day or two it is going to feel like you forgot how to program. That feeling is normal, it is temporary, and it is not a sign you are in the wrong place. Here is the thing nobody says out loud: you do not need to learn all of Rust to write Solana programs. Rust is a big language with a steep reputation, but the slice of it that shows up in an Anchor program is small and repetitive. You will see the same handful of patterns on almost every line. Learn those patterns and the wall turns back into a floor. This post is that handful. Not a Rust course, just the parts you need to read your first Anchor program and understand what every line is doing. Next week we start Arc 9, the Anchor introduction, where this all becomes real. This week is about making the language stop being scary before you get there. Why it feels like a wall JavaScript is dynamically typed and garbage collected. You write const x = 5 , you never tell anyone it is a number, and when you are done with it the runtime quietly cleans up. The language trusts you and sorts out the consequences at runtime, which is why a typo surfaces as undefined is not a function three minutes into a demo. Rust is the opposite philosophy. It is compiled and statically typed, so every value has a type the compiler knows about before the program ever runs, and it has no garbage collector, so it tracks who is responsible for every piece of memory through a system called ownership. The trade is blunt: Rust mak

I run a content site, do-and-coffee.com . Like everyone else, it gets scraped by AI crawlers. Instead of blocking them, I did something else: I put a paywall in front of the site that returns HTTP 402 Payment Required to bots, with machine-readable payment instructions. If a crawler pays a cent in USDC, it gets the article. If it doesn't, it gets the 402 and nothing else. Then I let it run for 30 days and watched. Here's what actually happened — and it's not the number you'd put on a pitch deck. TL;DR A Cloudflare Worker sits in front of the site. AI crawlers get 402 + x402 payment requirements ; humans and search bots pass through free. Payment is USDC on Base , $0.01 per article, verified and settled through Coinbase's CDP facilitator. 30-day result: 5,811 crawler requests, 5 paid, 5,806 served a 402. Revenue at $0.01/article ≈ $0.05 . The interesting part isn't the revenue. It's who paid: GPTBot paid 4 times out of 48 requests; ClaudeBot paid once out of 651. Architecture do-and-coffee.com/blog/article/* ─▶ x402 Worker (Cloudflare) │ has X-PAYMENT-RESPONSE? ───────────┤─▶ yes ─▶ proxy origin (200) KV cache hit (payer:url)? ─────────┤─▶ yes ─▶ proxy origin (200) no X-PAYMENT? ─────────────────────┤─▶ 402 + payment requirements has X-PAYMENT? ────────────────────┘ │ ├─▶ CDP /verify (is the signed payment valid?) ├─▶ CDP /settle (waitUntil: confirmed — on-chain) └─▶ on success: KV.put(payer:url, receipt, ttl 24h) ─▶ proxy origin The worker speaks the x402 protocol: a 402 response carries an accepts array describing exactly how to pay (scheme exact , network base , asset USDC, amount, payTo wallet). A compliant agent reads that, signs a USDC payment, and retries with an X-PAYMENT header. The worker verifies and settles it through Coinbase's facilitator, then proxies the real article. How it works The 402 response When there's no payment, the worker builds the requirements and returns 402: function buildPaymentRequirements ( resourceUrl : string , env : Env ): Payment

Reentrancy is the oldest trick in smart contract exploitation. The DAO fell to it in 2016. You would think a bug this famous would be extinct by now. It isn't. Protocols still lose millions to reentrancy every year, because the textbook version is the easy one, and attackers stopped using the textbook version a long time ago. This post walks through the classic bug, then the modern variants that still bite in 2026: cross-function, cross-contract, read-only reentrancy through view functions, and callback reentrancy through ERC777 and ERC721. I'll show why ReentrancyGuard is not the silver bullet most developers think it is, and how an LLM-based auditor reasons about the call-then-state-change pattern in a way pattern matchers can't. The Classic: Single-Function Reentrancy Here is the canonical vulnerable withdraw. contract VulnerableVault { mapping(address => uint256) public balances; function deposit() external payable { balances[msg.sender] += msg.value; } function withdraw() external { uint256 amount = balances[msg.sender]; (bool success, ) = msg.sender.call{value: amount}(""); require(success, "transfer failed"); balances[msg.sender] = 0; // state update AFTER the external call } } The attack is simple. The attacker is a contract. When withdraw sends ETH via msg.sender.call , control passes to the attacker's receive() function before balances[msg.sender] is zeroed. The attacker calls withdraw again. The balance is still the original amount, so the vault pays out again. Repeat until the vault is empty. contract Attacker { VulnerableVault vault; receive() external payable { if (address(vault).balance >= 1 ether) { vault.withdraw(); // re-enter before balance is zeroed } } } The fix is checks-effects-interactions. Do all your checks, then update all your state, and only then make the external call. function withdraw() external { uint256 amount = balances[msg.sender]; balances[msg.sender] = 0; // effect first (bool success, ) = msg.sender.call{value: amount}(""); //

If you build agents on Base, two things landed recently that are worth connecting. First: Base shipped its own Agent Skills. There's now a base/skills repo with consolidated skills that teach an AI agent to connect to Base, deploy contracts, authenticate wallets, and run nodes — installed with one command via Vercel's npx skills CLI. Second: that CLI is part of a fast-growing, cross-agent ecosystem most crypto devs haven't clocked yet. So this post does two things — explains how npx skills and skills.sh actually work, and shows where the payment layer in Base's skills stops and how to extend it with x402 pay-per-call and batch disbursement . What npx skills actually is npx skills is an open CLI from Vercel Labs for installing "skills" — modular SKILL.md files that teach an agent a specific capability without stuffing everything into its context window. A few things make it different from what crypto devs usually expect: GitHub is the registry. There's no central package server. Any public GitHub repo with a SKILL.md at its root is a valid, installable skill. Install with npx skills add owner/repo . It's cross-agent. The same skill installs into Claude Code, Cursor, Codex, GitHub Copilot, Goose, Windsurf, Gemini, and dozens more. You write once; it works across the agent you (or your users) actually run. skills.sh is the directory + leaderboard. It ranks skills by real install counts pulled from telemetry, with all-time, trending, and hot lists. There's no editorial submission step — you publish by putting a skill in a repo, and installs surface it. The format underneath — SKILL.md — is an open spec, which is why Base, Vercel, Anthropic, and a long tail of independent devs all use the same files. Here's Base's install, for reference: # Base's official agent skills npx skills add base/skills --skill build-on-base npx skills add base/skills --skill base-mcp build-on-base is a consolidated Base dev playbook; base-mcp wires up a Base MCP server that gives an agent a wall

TL;DR — The DIFP protocol was designed to be data-compact and geo-aware from day one. We recently discovered it maps almost perfectly onto the Nostr event format. Here's how, and why it matters for decentralized food infrastructure. Background: What Is DIFP? DIFP (Djowda Interconnected Food Protocol) is an open protocol designed to sync food product data across distributed nodes — compactly, efficiently, and with geo-location awareness built in by default. One of its core design decisions is the PAD system (Preloaded Asset Distribution): Apps ship with a preloaded asset pack — item metadata, compressed images, category structure — all bundled at install time. Only price and availability need to travel over the wire during sync. This means the data footprint per product is tiny. Very tiny. Enter Nostr Nostr is a simple, open protocol for decentralized communication. One of its key specs: events support up to 64 KB of content . When we started exploring Nostr as a potential transport layer, we ran the numbers — and the fit was surprisingly clean. The Math: Products Per Event Baseline encoding A product represented with three fields: { "id" : 500 , "available" : true , "price" : 30000 } At this level of verbosity, a single 64 KB Nostr event can hold approximately: ~1,500 – 2,000 products Already useful. But we can do better. Optimized encoding Two key optimizations: 1. Drop the availability key — If a product entry exists in the JSON, it's available. If it's absent, it's not. No boolean needed. 2. Drop the field names — Instead of {"id": 500, "price": 30000} , just store: 500,30000 Field mapping is handled at the app level, not the protocol level. The device knows position 0 is the product ID, position 1 is the price (in smallest currency unit, e.g. cents). Result ~6,000 – 7,000 products per single Nostr event Possibly more, depending on the price distribution and ID ranges in a given catalog. Geo-Discovery: MinMax99 Cells DIFP uses a geo-cell system called MinMax99 to

On April 1, 2026, Solana's largest decentralized perpetual futures exchange Drift Protocol suffered an attack, losing approximately $285 million . This is the second-largest DeFi hack of 2026 (behind KelpDAO's $292M attack the same month). Together, these two incidents totaled $577M — 76% of all DeFi stolen funds in 2026 . Key Finding : This was not a smart contract vulnerability. The attacker penetrated protocol personnel through social engineering , used Solana's durable nonce feature to pre-sign malicious transactions, and drained the entire treasury in 12 minutes . Mandiant confirmed the attacker as North Korean state-sponsored APT group UNC6862. ⏱️ Attack Timeline Time Event 6 months prior North Korean hackers establish fake trading company identities, attend crypto industry events Weeks prior Operatives attend crypto conferences in person, build deep trust with Drift contributors Late Feb - Early Mar Telegram group discussions about trading strategies, posing as partners Dec 2025 - Jan 2026 Fake company "Ecosystem Vault" builds partnership with Drift, deposits $1M+ Feb - Mar Attackers gain access to some contributors' code repositories Mar 23 Create 4 malicious wallets using Solana durable nonce feature Mar 27 Security Council migrates to 0-second timelock , removing safety buffer Apr 1, 16:06:09 UTC Execute pre-signed malicious transactions 16:06 - 16:18 UTC Treasury completely drained in 12 minutes Post-Apr 1 Funds swapped via Jupiter, bridged to Ethereum via CCTP, mostly dormant 🔧 Attack Technical Analysis Initial Penetration The attackers used a multi-layered social engineering + technical infiltration combination: HUMINT Operation Spent months building credible identities, attending global industry events Used intermediaries rather than direct contact (classic Lazarus tactic) ZachXBT noted this layered identity structure is a hallmark of Lazarus operations Malicious Code Injection Shared code repositories containing malicious code Exploited unpatched VSCo

Bitcoin can look simple from the outside: paste an address, choose an amount, send. Under that simple interface are several concepts that are useful for developers and technical beginners to understand. This post is not trading advice and does not discuss price. It is a practical mental model for what is happening when someone sends Bitcoin. 1. A wallet does not "hold coins" the way an app balance does Many beginners imagine a wallet as a container full of coins. That is close enough for casual conversation, but it can be misleading. A Bitcoin wallet manages keys and helps create transactions. The Bitcoin network tracks spendable outputs on the ledger. When you send BTC, the wallet constructs a transaction that spends previous outputs and creates new outputs. You do not need to master every detail on day one, but the high-level idea matters: control of keys controls the ability to spend. 2. An address is a destination, not an identity A Bitcoin address is where funds can be sent. It is not a username and it is not automatically tied to a person in the way a social profile is. Before sending, beginners should check the address carefully. A small copy-paste mistake can be permanent. Malware can also replace clipboard contents, so visually checking the beginning and ending characters is a useful habit. For larger transfers, a tiny test transaction can reduce risk. 3. Fees are about block space Bitcoin transactions compete for limited block space. A fee is not a tip to a company. It is part of the transaction economics that helps miners decide which transactions to include. When the network is busy, low-fee transactions may wait longer. When the network is quieter, confirmations may happen faster. The beginner lesson is simple: do not assume "sent" means "fully settled." Check confirmations and understand that fee choice can affect waiting time. 4. The mempool is a waiting area Before a transaction is confirmed in a block, it may sit in the mempool, which is a pool of u

Welcome to our weekly digest, where we unpack the latest in account and chain abstraction and the broader infrastructure shaping Ethereum. This week: Base ships its first independent upgrade with a TEE+ZK multiproof system and confirms native AA is next; Biconomy turns the ERC-8211 smart batching standard into a TypeScript SDK; LI.FI launches an enterprise intents engine for stablecoin and RWA flows; and Vitalik steps back from technical essays to write fiction. Base Launches Azul, Bringing Multiproofs to Coinbase's L2 Biconomy Ships Smart Batching SDK for ERC-8211 LI.FI Launches Intents Engine for Enterprise Cross-Chain Flows Vitalik Pivots to Fiction and Floats a "Trust Dependency" Framework Please fasten your belts! Base Launches Azul, Bringing Multiproofs to Coinbase’s L2 Base activated Azul on mainnet on May 28, its first network upgrade built entirely on its own stack. The headline feature is a multiproof system that pairs Trusted Execution Environment (TEE) proofs with Zero-Knowledge (ZK) proofs, advancing the Coinbase-incubated L2 toward Stage 2 decentralization. Either proof type can finalize a withdrawal independently, but when both agree, finality drops to as little as one day, far faster than the typical multi-day optimistic rollup wait. Crucially, permissionless ZK proofs can override permissioned TEE proofs if the two conflict, a design Base says meaningfully improves censorship resistance. The upgrade also makes base reth the sole execution client and introduces a new consensus client, phasing out older software. Node operators must migrate to the new stack to stay in sync. For AA and chain abstraction builders, the more important signal is what comes next: Base confirmed its end-of-June upgrade will include native account abstraction, an enshrined token standard and Flashblock Access Lists. The largest L2 by activity moving toward native AA is a meaningful pull on the whole ecosystem. Biconomy Ships Smart Batching SDK for ERC-8211 Biconomy released t

I Built My First Token on Solana — Here's What Actually Surprised Me This week I went from zero tokens to minting, transferring, charging fees, and locking tokens so they can never move. Here's what stuck with me. Tokens don't live in your wallet Coming from Web2, I assumed tokens would just... show up in your account. Nope. On Solana, every wallet needs a separate token account for each token it holds. One mint, one folder. It felt weird at first. Now it makes sense. You can charge fees without writing a single backend The Token Extensions Program has a built-in transfer fee. One flag at mint creation time: spl-token create-token \ --program-id TokenzQdBNbLqP5VEhdkAS6EPFLC1PHnBqCXEpPxuEb \ --transfer-fee-basis-points 100 That's a 1% fee on every transfer, enforced by the blockchain. No middleware. No payment processor. No way to bypass it. You can make a token that literally cannot be transferred spl-token create-token \ --program-id TokenzQdBNbLqP5VEhdkAS6EPFLC1PHnBqCXEpPxuEb \ --enable-non-transferable I minted 10, tried to send 5, and watched the transaction get rejected. Not by my code — by the program itself. Perfect for credentials, badges, or certificates that should belong to one person forever. The biggest shift from Web2: these rules are set at creation and are permanent. You can't add a transfer fee to an existing token. You can't make a transferable token non-transferable later. It forces you to think about token design upfront, which is honestly a good constraint. solana #blockchain #webdev #beginners #100DaysOfSolana

Blockchain performance is determined by consensus rules. There is no acceleration layer within the protocol. One of the most common misconceptions about blockchain technology is the belief that transaction speed can be dramatically increased through special tools, hidden settings, or external services. While applications can improve user experience and optimize how information is presented, they cannot change the fundamental rules that govern how blockchain networks process transactions. At the core of every blockchain is a consensus mechanism. Consensus is responsible for ensuring that independent participants agree on the validity and order of transactions before they become part of the permanent ledger. Whether a network uses Proof of Work, Proof of Stake, or another consensus model, transaction processing remains tied to the protocol rules that all participants follow. Every transaction moves through a structured lifecycle: submit → validate → confirm Submission introduces the transaction to the network. Validation ensures that the transaction complies with protocol requirements and contains legitimate data. Confirmation establishes agreement across the network and records the transaction as part of the blockchain. These stages are not optional. They are essential to maintaining consistency and trust within decentralized systems. Because blockchain performance is governed by consensus, there is no protocol-level acceleration layer that can bypass validation or force immediate finality. No application can override consensus. No service can remove verification requirements. No external process can alter the execution sequence established by the protocol. What users often interpret as slow performance is usually the result of network conditions such as congestion, validator workload, transaction prioritization, or fee market activity. These factors can influence confirmation times, but they do not change the underlying rules of the system. Blockchain networks are d

I spent 7 days learning Solana token extensions. Here's what clicked, what surprised me, and the code you need to build tokens that can't be traded but can be revoked. The Problem (In Web2 Terms) Imagine you work in HR. You issue an employee a digital badge proving they're a certified security officer. Here's what you'd want: The badge stays in their wallet — they can't trade or sell it Only they can use it If they leave the company or fail a compliance check, you can revoke it silently without their permission The badge metadata (name, symbol, type) is on-chain and permanent You could build this with centralized databases and APIs. On Solana, it's just three extensions on a token mint . What Are Token Extensions? Solana's Token-2022 program lets you attach additional behaviors to any mint at creation time. Think of them like middleware for tokens. Before extensions, every token was the same — a mint with supply and decimals, token accounts holding balances, and transfer instructions. Extensions let you add rules on top : Extension What It Does Use Case Transfer Fee Charge a percentage on every transfer Protocol revenue, marketplace commissions Non-Transferable Make tokens unmovable after minting Soulbound badges, credentials, memberships Permanent Delegate Let the issuer burn tokens from anyone Revocable credentials, subscriptions with expiry Metadata Store name, symbol, URI on-chain Self-describing tokens, no external API needed Default Account State Freeze all new accounts by default Compliance gates, KYC verification The critical rule: extensions must be declared at mint creation . You cannot add them later. This forces you to think about your token's full lifecycle before deploying — which is good design discipline. The Journey: Three Combinations That Matter Over the past week I built three different token types. Here's what I learned from each. Day 34: Transfer Fees (The Marketplace Token) A token that charges 1% on every transfer, withheld automatically and

How combining Non-Transferable and Permanent Delegate extensions changed my understanding of digital ownership on Solana. Imagine earning a high rank in an online game. You can use it. You can benefit from it. Other players can see it. But you cannot transfer that rank to someone else. If you break the game's rules, the game company can revoke it. And if the game gets acquired by another company, authority over that rank can be handed over to a new administrator. That was the closest mental model I found for understanding one of the most interesting things I built this week on Solana: a credential token using Token-2022 extensions. What are Token Extensions? One thing I've learned during this phase of the challenge is that Token-2022 is not just about creating tokens. It allows you to define behaviors directly at the token level through extensions. Instead of relying on application logic to enforce rules, the token program itself can enforce them. For this experiment, I combined two extensions: Non-Transferable — prevents ownership from being transferred to another wallet. Permanent Delegate — gives a designated authority the ability to manage the token even after it has been issued. Individually, those are useful. Together, they create something that behaves less like a currency and more like a credential. The Transfer That Was Supposed to Fail After creating the token, I tried transferring it. spl-token transfer Gn5PZzwDENvpQESaFwgVqzCUFba5sSka59iLtjFTYNvz 1 $THIRD_PARTY \ --owner ~/recipient-wallet.json \ --fee-payer ~/.config/solana/id.json \ --program-id TokenzQdBNbLqP5VEhdkAS6EPFLC1PHnBqCXEpPxuEb \ --fund-recipient --allow-unfunded-recipient The result: Recipient: ErYcpQYcpdoaaiufrB3MqQE2QaVEhoACZGcssppszPpY Recipient Token Account: 8CvyoKt11UbkWYRVXey6UKK2gqQcvVvbh9Lv3crzo8C3 Funding ATA: 8Cvyokt11UbkWYRVXey6UKK2qqQcvVvbh9LV3crz0803 Status: ❌ Transaction failed during simulation Error: Transfer is disabled for this mint (Token-2022 restriction) What I liked a

🏦 Day 6 of 7: Building a Mini Uniswap in 80 Lines of Solidity Imagine a vending machine. It has 1,000 coffee beans and 1,000 coins. No menu, no cashier — just one iron rule: the product of the two numbers inside must never decrease. That's it! This is how Uniswap works — and this is what I built on Day 6, coming from .NET. Here's how, why it's elegant, and where you can step on a rake. Why an Order Book Doesn't Work on a Blockchain Traditional exchanges — Binance, NYSE, any CEX — run on an order book . Market makers post bids and asks. A matching engine pairs them. Millions of updates per second, all in a centralised database. In a blockchain, this is impossible. Transactions take 12 seconds. Every state change costs gas. Storing millions of constantly changing orders would eat all the profit before a single trade completes. Uniswap's solution: replace the order book with a liquidity pool — a smart contract holding two tokens — and replace the matching engine with pure math. Just a formula — below. x · y = k — The Formula That Broke Finance The Constant Product Invariant : x · y = k Where x is the reserve of Token0, y is the reserve of Token1, and k is a constant that must never decrease during swaps. When a trader sells Token0 into the pool, x increases. To keep k constant, y must decrease — the contract sends out Token1. The price is determined automatically by the ratio of reserves. Live example with numbers: Pool: 1,000 Token0, 1,000 Token1. k = 1,000,000. Trader sells 100 Token0: amountOut = (reserveOut × amountIn) / (reserveIn + amountIn) amountOut = (1000 × 100) / (1000 + 100) amountOut = 100,000 / 1,100 amountOut ≈ 90.9 Token1 The trader gets ~90.9, not 100. That gap is slippage — and it's not a bug. It's the formula protecting the pool. The more you buy relative to pool size, the worse your price gets. Naturally. Mathematically. After the swap: pool has 1,100 Token0 and ~909.1 Token1. k ≈ 1,000,000. Invariant holds. The Contract: SimpleAMM Three functions.

In the past, when people heard the word “token,” they usually thought about cryptocurrency, trading,...

If you have been following the 100 Days of Solana challenges, you have already worked with tokens. You created mints, set up token accounts, transferred SOL, and explored token extensions. But there is a distinction that comes up constantly in web3, and understanding it properly will change how you think about everything you build going forward. Fungible and non-fungible tokens. You have probably heard these terms before, especially NFTs. But what do they actually mean on Solana, and how does the same token system handle two very different concepts? What makes something fungible Fungible just means interchangeable. One unit is identical to another unit. If I have 10 USDC and you have 10 USDC, ours are exactly the same. It does not matter which specific USDC tokens I hold because they are all worth the same and behave the same way. We could swap them and nothing changes. This is how most things you are used to work. A dollar bill is fungible. A liter of petrol is fungible. One unit of SOL is the same as any other unit of SOL. When you built token transfers in the challenges, you were working with fungible tokens. You did not need to care about which specific tokens moved, just how many. Fungible tokens are used for currencies, stablecoins, utility tokens, governance tokens, loyalty points, in-game currencies, and anything where the quantity matters more than the individual unit. What makes something non-fungible Non-fungible means unique. Each token is different from every other token, even if they come from the same collection. If I have NFT #42 from a collection and you have NFT #87, those are not interchangeable. They might have different images, different properties, different rarity, or different utility. Think of it like event tickets. Two tickets to the same concert are not the same if one is front row and the other is in the back. They came from the same event, but each one is distinct. Non-fungible tokens are used for digital art, collectibles, membership pa