Goal: Ship a small but real Anchor program + client.

Cover: Accounts macros, constraints, events, errors, IDL, TypeScript client.

Activity: Counter or notes app with create → update → close flows.

Takeaway: “I can build faster with Anchor’s patterns safely.”

1) Module overview

Anchor reduces boilerplate via Rust macros (#[derive(Accounts)], #[account]), account constraints (init, payer, space, seeds, bump, has_one), custom errors (#[error_code], require!), and events (emit!). The IDL generated on build powers a TypeScript client via @coral-xyz/anchor (web3.js v1).

2) Plain-English explainer

Project anatomy (what Anchor adds)

• Program module: instruction handlers + account types (Anchor adds an 8-byte discriminator to accounts).
• Accounts structs: #[derive(Accounts)] validates required accounts and enforces constraints at runtime.
• Constraints: init/payer/space create state. seeds/bump derive PDAs. has_one binds relationships.
• Errors: define #[error_code] enums. Use require!, require_keys_eq!, etc.
• Events: typed logs via emit! (and emit_cpi! across CPIs).
• IDL: JSON emitted to target/idl/<program>.json.
• TypeScript client: @coral-xyz/anchor loads your IDL (use web3.js v1).

3) Activity — build a minimal Notes program (create → update → close)

A) Scaffold and run local tests