Echo

Echo is a compiled language implemented in Rust. It uses a single LLVM backend and a Rust-owned runtime for both AOT native binaries and in-process JIT execution.

The command-line entrypoint is xo.

Status

Echo is early-stage software. The workspace is scaffolded for full vertical slices (frontend → semantics → IR → codegen → runtime → CLI). Language features are implemented incrementally with focused proofs.

Language design (in progress)

Echo 2026 is the current language edition and canonical public Language Spec (site /e26, ADR 0015). The executable contract is the echo26/ suite (e26 runner).

Keyword-free, statement-led core — implementer surface: docs/syntax.md.

Tree	Role
examples/misc/	Tiny xo run demos (print, loops, lists, result)
examples/app/	HTTP demo + kitchen-sink surface
examples/algos/	Classic algorithms (factorial, sort, primes, …)
std/	Standard library Echo sources (IO, TCP, HTTP stubs)

cargo build -p xo
./target/debug/xo run examples/misc/hello.echo
./target/debug/xo run examples/misc/sum_list.echo ; echo exit:$?
./target/debug/xo check examples/app/surface.echo

Track discussion in docs/roadmap.md.

Documentation

Doc	Role
AGENTS.md	Workflow and invariants for humans/agents
docs/README.md	Full docs map
docs/architecture.md	Pipeline and crate ownership
docs/glossary.md	Shared vocabulary
docs/development-speed.md	Local tools and gate
docs/adr/	Architecture decisions

Layer specs (docs/syntax.md, docs/parser.md, …) accumulate rules as each layer lands.

Workspace

See docs/architecture.md for crate ownership and the compilation pipeline.

• Frontend: echo_source, echo_diagnostics, echo_syntax, echo_lexer, echo_ast, echo_parser, echo_semantics
• IR and backend: echo_hir, echo_mir, echo_codegen, echo_codegen_abi, echo_runtime, echo_std
• Project tooling: echo_index, echo_resolver, echo_fingerprint, echo_cache, echo_build, echo_reflection, echo_lsp
• CLI: xo
• Browser check host: echo_wasm (just wasm, site /try)

Requirements

• Rust with edition 2024 support
• LLVM 22 when codegen is active (inkwell)
• clang and mold for native link speed
• sccache for compile caching
• cargo-nextest and just for the local gate

See docs/development-speed.md for setup and the edit/test loop.

Install (user toolchain)

Published builds are prereleases. The current tag is v0.0.1-alpha.12 and ships xo-linux-x86_64.tar.gz, xo-macos-arm64.tar.gz, and xo-windows-x86_64.tar.gz. from-release with no tag installs the newest published prerelease. Pass a tag to pin. GitHub /releases/latest only resolves a non-prerelease and 404s today.

curl -fsSL https://raw.githubusercontent.com/modoterra/echo/main/scripts/install.sh \
  | bash -s -- from-release

# Pin this tag
# … | bash -s -- from-release v0.0.1-alpha.12

From a checkout, build + install under XDG and link ~/.local/bin/xo:

./scripts/install.sh              # build from this tree
./scripts/install.sh from-release # newest published prerelease
./scripts/install.sh from-release v0.0.1-alpha.12
./scripts/install.sh upgrade      # new version, keep previous
./scripts/uninstall.sh            # remove toolchain ( --purge also clears $XO_HOME )
./scripts/install.sh doctor

Layout and env vars: docs/install.md.

Build and test

cargo check --workspace
scripts/gate changed --list
scripts/gate changed
scripts/gate workspace
just tools

cargo build -p xo always includes LSP and REPL (no Cargo features).

CI

GitHub Actions (.github/workflows/ci.yml) release-builds xo only when a GitHub release is published — not on push, PR, or bare tags.

Artifact	Runner
Linux x86_64	ubuntu-24.04
Windows x86_64	windows-2022
macOS arm64	macos-14

The current published tag (v0.0.1-alpha.12) attaches xo-linux-x86_64, xo-macos-arm64, and xo-windows-x86_64. Windows AOT xo run is not first-class yet; the Windows archive is xo.exe for check/fmt/lsp/repl.

On Linux, smoke (cargo test -p xo, xo run hello) and scripts/gate echo26 (Echo 2026 conformance) are hard gates when that workflow runs.

CLI surface (commands land as the language grows):

cargo run -p xo -- --help
cargo run -p xo -- lex <file>
cargo run -p xo -- ast <file>
cargo run -p xo -- ir <file>
cargo run -p xo -- run [--jit] <file>
cargo run -p xo -- build <file> -o <out>
cargo run -p xo -- lsp
cargo run -p xo -- repl

Website

The public site is https://xo.run (Cloudflare Pages). Sources live in www/ of this repository (Vite, React, Tailwind). GitHub Pages on this repo only redirects to that host; it does not publish www/.

npm --prefix www install
npm --prefix www run dev
npm --prefix www run lint
npm --prefix www run format
npm --prefix www run build
# or
just web-dev
just web-build
scripts/gate web

Contributing

Contributions are welcome. By contributing, you accept the project CLA, which assigns copyright and IP in your contribution to Modoterra Corporation.

• How to contribute: CONTRIBUTING.md
• Contributor License Agreement: CLA.md
• Security: SECURITY.md
• Help wanted (broad): docs/roadmap.md

Pull requests run a Linux gate (build, smoke, echo26). Multi-OS release builds run only when a GitHub Release is published.

Community

Use common sense and decency. There is no formal code of conduct. We reserve the right to moderate this community to the extent of the law and the policy of the host. Write community@modoterra.xyz if you need us.

License

Licensed under the MIT License.

Copyright (c) 2026 Modoterra Corporation.