promptc - Prompt Compiler for Agentic Programming

A fast, zero-dependency CLI tool (written in Go) that compiles .spec.promptc files into a single instructions.promptc output. Stop copy-pasting instructions between projects and tools.

The Problem

As developers using AI coding assistants, we face a few recurring problems:

• Scattered instructions: The same guidance gets duplicated across repos and tool-specific files.
• No reusability: Common patterns such as REST APIs, testing, and security are copied by hand.
• Inconsistency: Instructions drift between projects over time.
• No composition: It is hard to build on shared prompt libraries.

The Solution

promptc gives you a simple compiler flow:

1. Write instructions once in .spec.promptc
2. Import reusable prompt libraries
3. Compile to a single model-agnostic instructions.promptc
4. Optionally run promptc build to fetch resources and execute an agent in a sandbox

Mental Model

[Reusable Prompt Libraries] + [Project Spec] → Compiler → instructions.promptc

Installation

Shell script (Linux / macOS) — Recommended

curl -fsSL https://raw.githubusercontent.com/Geogboe/promptc/main/install.sh | sh

Installs to /usr/local/bin if writable, otherwise ~/.local/bin. Override with PROMPTC_INSTALL_DIR.

PowerShell (Windows)

irm https://raw.githubusercontent.com/Geogboe/promptc/main/install.ps1 | iex

Installs to %USERPROFILE%\.local\bin and adds it to your user PATH automatically. Override with $env:PROMPTC_INSTALL_DIR. The install scripts resolve published release assets from the GitHub release metadata instead of guessing archive names.

go install (requires Go 1.21+)

go install github.com/Geogboe/promptc/cmd/promptc@latest

Manual download

Download the latest release archive for your platform from the releases page.

Build from Source

git clone https://github.com/Geogboe/promptc.git
cd promptc
task build
# Or: go build -o bin/promptc.exe ./cmd/promptc

Examples

The examples/ directory is the canonical place to learn promptc through real workflows. Start with examples/README.md for runnable examples and expected outputs.

Quick Start

1. Initialize a new project

promptc init myapp.spec.promptc --template=web-api

2. Edit your .spec.promptc file

imports:
  - patterns.rest_api
  - constraints.security

context:
  language: go
  framework: fiber
  database: postgresql

features:
  - api_endpoint: "User authentication and JWT tokens"

constraints:
  - no_hardcoded_secrets
  - comprehensive_test_coverage

3. Validate and compile

promptc validate myapp.spec.promptc
promptc compile myapp.spec.promptc

Features

Built-in Prompt Libraries (8 total)

Patterns:

• patterns.rest_api - REST API best practices
• patterns.testing - Testing guidelines
• patterns.database - Database design and queries
• patterns.async_programming - Async/await patterns

Constraints:

• constraints.security - Security best practices
• constraints.code_quality - Code quality standards
• constraints.performance - Performance optimization
• constraints.accessibility - WCAG compliance

Project Templates

Initialize projects with templates:

promptc init myapp.spec.promptc --template=basic      # Basic template
promptc init myapp.spec.promptc --template=web-api    # Web API template
promptc init myapp.spec.promptc --template=cli-tool   # CLI tool template

Commands

Validate Specs

promptc validate myapp.spec.promptc

Compile Prompts

promptc compile myapp.spec.promptc
promptc compile myapp.spec.promptc --output=./output
promptc compile myapp.spec.promptc --debug
promptc compile myapp.spec.promptc --no-validate

Build Projects

promptc build myapp.spec.promptc --dry-run
promptc build myapp.spec.promptc

List Libraries

promptc list
promptc list --verbose

Initialize Projects

promptc init [name.spec.promptc] --template=<template>

Advanced Usage

Import Resolution

Prompts are resolved from multiple locations in order:

1. Project-local: ./prompts/ in your project
2. Global: ~/.prompts/ in your home directory
3. Built-in: Embedded in the binary

Exclusions

Exclude specific imports with the ! prefix:

imports:
  - patterns.rest_api
  - !patterns.rest_api.verbose_logging

Custom Libraries

Create your own reusable libraries:

~/.prompts/company/standards.prompt:

# Company Coding Standards

## Code Review
- All PRs require 2 approvals
- Must pass CI/CD pipeline

Use in any project:

imports:
  - company.standards

Use Cases

1. Team Knowledge Base

Share prompt libraries across your team:

# Create team prompts repository
mkdir ~/.prompts/team
# Everyone uses the same standards
imports:
  - team.api_standards

Why Go?

The Go rewrite provides significant advantages:

• ✅ Single binary - No Python runtime or dependencies needed
• ✅ Fast startup - Instant compilation (< 10ms for most operations)
• ✅ Cross-platform - Easy distribution for Linux, macOS, Windows
• ✅ Small footprint - ~8MB static binary
• ✅ Embedded resources - Built-in libraries compiled into binary

Technical Details

• Language: Go 1.21+
• Binary Size: ~8MB (static binary)
• Dependencies: Zero runtime dependencies
• Built-in Libraries: Embedded using go:embed
• Performance: Sub-10ms compilation for most operations
• CLI Framework: Cobra
• YAML Parser: gopkg.in/yaml.v3

Development

Building

task build          # Build for current platform
task build-all      # Build for all platforms
task test           # Run tests
task clean          # Clean build artifacts

Testing

go test ./...               # Run all tests
go test -v ./internal/...   # Verbose output

Roadmap

• Core compilation engine
• Generic instructions.promptc output
• Built-in prompt libraries (8 libraries)
• Project templates
• Validation system
• Go rewrite for performance
• Build pipeline with resource fetching and sandboxed agent execution
• Examples directory for real workflows
• Watch mode for auto-recompilation
• Library versioning
• Published library packages
• VSCode extension

Contributing

Contributions welcome! Please:

1. Fork the repository
2. Create a feature branch
3. Make your changes
4. Add tests if applicable
5. Submit a pull request

License

MIT License - see LICENSE file for details

Why promptc?

As AI-assisted development becomes standard, managing instructions across different tools is a growing pain. promptc treats prompts as code:

• Fast & Portable - Single binary, no dependencies
• Version controlled - Track changes to your instructions
• Composable - Build on reusable libraries
• Testable - See exactly what you're sending to the LLM
• Shareable - Collaborate on prompt engineering

Just like we don't copy-paste code between projects, we shouldn't copy-paste prompts. Compile them instead.