Architecture

Vibe CLI follows the Functional Core, Imperative Shell pattern for maintainability and testability.

Project Structure

src/
  main.rs           # CLI entry point (thin shell)
  lib.rs            # Module exports
  core/
    mod.rs
    config.rs       # Provider detection (pure, testable)
  providers/
    mod.rs
    anthropic.rs    # Anthropic API client
    openai.rs       # OpenAI/Ollama API client
  cli/
    mod.rs
    output.rs       # Spinner, colors, clipboard

Design Principles

Functional Core

The core/ module contains pure functions with no side effects:

• Config detection - Takes environment variable getter as a parameter
• Testable - Unit tests don’t need mocks for environment variables
• Predictable - Same inputs always produce same outputs

#![allow(unused)]
fn main() {
// Pure function - testable without mocking env vars
pub fn detect(
    model_override: Option<&str>,
    endpoint_override: Option<&str>,
    env_vars: &dyn Fn(&str) -> Option<String>,
) -> Option<Config>
}

Imperative Shell

The main.rs is a thin shell that:

1. Parses CLI arguments
2. Wires dependencies together
3. Handles I/O (network, terminal, clipboard)
4. Reports errors

Side Effects Isolated

The providers/ and cli/ modules handle I/O:

• providers/ - HTTP calls to LLM APIs
• cli/ - Terminal output, clipboard operations

Data Flow

┌─────────────┐     ┌──────────────┐     ┌─────────────┐
│   CLI Args  │ ──▶ │  Config      │ ──▶ │  Provider   │
│   (clap)    │     │  Detection   │     │  API Call   │
└─────────────┘     └──────────────┘     └─────────────┘
                                               │
                                               ▼
┌─────────────┐     ┌──────────────┐     ┌─────────────┐
│   Execute   │ ◀── │  Display     │ ◀── │  LLM        │
│   Command   │     │  Result      │     │  Response   │
└─────────────┘     └──────────────┘     └─────────────┘

Error Handling

• Uses anyhow for error propagation with context
• Semantic exit codes via exitcode crate
• Friendly panic messages via human-panic

Dependencies