# fastC

> A small systems language with capability-typed I/O, mandatory contracts, and zero executable build scripts — built for the age of agent-generated code. Compiles to portable C11. v1.0 feature-complete; MIT-licensed; Sigstore + SLSA L3 on releases.

fastC is a research project of Skelf-Research. The compiler is written in Rust (1.85+), emits readable C11, and ships eight pre-wired cross-compile targets via `zig cc`. The language is designed around four properties: capability-typed I/O as function arguments (no ambient `fs::read`), mandatory `@requires`/`@ensures` contracts on public APIs with three-tier discharge (syntactic → Z3 → runtime trap), declarative-only package manifests with no executable build scripts, and a compile-time budget enforced in CI.

The honest framing is in [docs/MANIFESTO.md](https://github.com/Skelf-Research/fastc/blob/main/docs/MANIFESTO.md): fastC is not "Rust minus features" — it is the smaller language that combines capability typing, mandatory contracts, no `build.rs`-class scripts, vendored content-hashed deps with cosign keyless + SLSA L3, and one curated answer per domain via the 11-package `fastc-core` ecosystem.

## Docs
- [Overview](https://fastC.skelfresearch.com/): tagline, syntax samples, measured numbers, top-level wedge
- [About](https://fastC.skelfresearch.com/about/): the thesis, what we commit to, what we don't commit to
- [fastc-core](https://fastC.skelfresearch.com/fastc-core/): the 11-package curated stdlib ecosystem
- [Tooling](https://fastC.skelfresearch.com/tooling/): the v1.3 agent surface (`fix` / `context` / `diff` / `mcp` / `explain`)
- [Documentation](https://docs.skelfresearch.com/fastc/): full language guide, CLI reference, C interop, getting started

## Agent tooling (v1.3, shipped)
- `fastc fix` — applies the fix-it hints the compiler already emits
- `fastc context` — dumps the cap / contract / annotation surface for a function or module
- `fastc diff` — capability-shape changes across a commit range
- `fastc mcp` — Model Context Protocol server for Claude Code / Cursor / Codex
- `fastc explain --json` — structured annotations + capabilities + contracts per item, plus the `modules` array of v1.3 module headers

## Comparisons
- [vs Rust](https://fastC.skelfresearch.com/compare/rust/): row-by-row with verdicts
- [vs Zig](https://fastC.skelfresearch.com/compare/zig/): closest in spirit; differs on capabilities + contracts

## Blog
- [What goes wrong when LLMs write C: the recurring bugs](https://fastC.skelfresearch.com/blog/llm-c-recurring-bugs/)
- [Reading fastC: side-by-side syntax with plain C](https://fastC.skelfresearch.com/blog/reading-fastc-vs-c/)
- [Why agent-friendly is a real language design goal](https://fastC.skelfresearch.com/blog/agent-friendly-language-design/)

## Source
- [github.com/Skelf-Research/fastc](https://github.com/Skelf-Research/fastc): MIT, 340+ tests, Cargo workspace
- 11-package fastc-core ecosystem: github.com/Skelf-Research/fastc-core-{cli,log,json,toml,http,time,base64,uuid,crypto-primitives,regex,sqlite}, each at `v0.1.0` preview