A working example of Anchor-based CPI (Cross Program Invocation) — when one Solana program calls another. This project demonstrates best practices for inter-program communication using the Anchor framework.

📚 GitHub Repository

This project illustrates how to structure two Solana programs (program-a and program-b) where Program A performs a CPI to Program B, and also interacts with System Program (for SOL transfers).

CPI (Cross-Program Invocation) is a critical building block for modular, reusable smart contracts on Solana. This example is ideal for:

  • Developers learning advanced Solana development
  • Those building protocol layers or modular dApps
  • Projects where multiple programs need to coordinate actions

🔧 Stack & Tools

  • 🦀 Rust — primary language
  • ⚓ Anchor — Solana framework
  • 🔁 CPI Pattern
  • 🔍 Transaction Explorer
  • 🧪 Anchor tests with local validator

✨ Features

  1. Call Another Program from Your Program

    • CPI pattern with invoke_signed() in Anchor

  2. Pass Accounts & Instruction Data

    • Structured instruction building for inner program calls

  3. Work with System Program

    • Demonstrates how to invoke built-in programs (e.g., SOL transfers)

  4. Observe Execution Flow

    • View log output to understand program interaction sequence

🚀 Setup & Usage

1. 🏗️ Initialize Projects

Create two Anchor programs:

anchor init program-a
cd ..
anchor init program-b

2. 🔁 Configure Dependencies

In Cargo.toml of program-a, add:

program-b = { path = "../program-b", features = ["cpi"] }

In Anchor.toml of program-a, disable auto-resolution of dependencies:

[programs.localnet]
program_b = "..." # Your local key

[workspace.dependencies]
program-b = { path = "../program-b", features = ["cpi"], resolution = false }

3. 🧪 Run Tests

Build and test CPI interaction:

anchor build && anchor test

4. 🧱 Start Local Validator

cd .anchor/
solana-test-validator

5. 🔍 View Transactions

  1. Open explorer.solana.com
  2. Switch to "Localhost" network
  3. Find your transaction signature in test output logs

🖥️ Sample Logs

Program logged: "Instruction: Initialize"
Program logged: "Greetings from: Program A"
Program invoked: System Program
Program returned success
Program invoked: Unknown Program (...)
Program logged: "Instruction: Initialize"
Program logged: "Greetings from: Program B"
Program consumed: 676 of 190087 compute units
Program returned success

These logs show:

  • Instruction flow through both programs
  • System-level interaction
  • Success/failure of each step

📄 License

This project is licensed under the MIT License — free to use, modify, and extend.