yeet@ is a tiny microblog that stores each post directly on-chain in a program-owned account. The webapp lets you:

• Post short messages ("yeets") up to 512 bytes
• Auto-create your on-chain user profile on first post
• Browse a user’s posts at /u/[address] and individual posts at /u/[address]/[index]

Under the hood, the frontend talks to a small Rust program that manages a per-user counter and writes each post’s header + content into a dedicated account.

• Node.js and npm
• A Solana wallet (Phantom, Backpack, or Android MWA)
• Devnet RPC (defaults to devnet; Helius URL optional)

Create a .env.local in web/ with:

# Required: the deployed program id of the microblog program
# Either var name works; NEXT_PUBLIC_YEET_PROGRAM_ID takes precedence in the app
NEXT_PUBLIC_YEET_PROGRAM_ID=YourProgramId111111111111111111111111111111
# NEXT_PUBLIC_MICROBLOG_PROGRAM_ID=YourProgramId111111111111111111111111111111

# Optional: RPC; defaults to "devnet" if unset
NEXT_PUBLIC_RPC_URL=https://rpc.helius.xyz/?api-key=YOUR_KEY

cd web
npm install
npm run dev

Open http://localhost:3000 and connect your wallet (devnet). Compose a message and click Post. Your posts are listed locally and can be viewed on-chain at:

• /u/<your_address> — all your posts
• /u/<your_address>/<index> — a single post

Production build:

npm run build
npm start

Path: program/yeet-at/src/lib.rs

The program exposes two instructions:

• InitUser (discriminator 0)

  • Accounts: [signer author], [writable user_profile]
  • Initializes a user profile account owned by the program and sets post_count = 0.

• CreatePost (discriminator 1)

  • Accounts: [signer author], [writable user_profile], [writable post_account]
  • Validates sizes/ownership, increments the user’s post_count, and writes the post header + UTF-8 content into post_account.

Account layouts (packed, little-endian):

• User profile: 1-byte tag (1) + 32-byte owner + u64 post_count → total 41 bytes
• Post account: 1-byte tag (2) + 32-byte author + u64 index + u16 content_len + content[0..512]

Addressing model used by the webapp:

• The client creates program-owned accounts with System Program createAccountWithSeed, using seeds:
  • User profile: seed "user"
  • Post: seed "post-{index}"
• The program itself does not derive or enforce a specific address scheme beyond ownership and size checks; it writes to the provided, writable accounts.

Limits and checks:

• Content must be 1..=512 bytes
• User profile and post accounts must be owned by the program and sized exactly as expected

There is a lightweight simulator test in program/yeet-at/tests/litesvm_test.rs. It loads an SBF build of the program if you set an environment variable:

cd program/yeet-at
# Point to a compiled SBF .so for the program
export YEET_AT_SBF_PATH=/absolute/path/to/yeet_at.so
cargo test -p yeet-at -- --nocapture