vera-language

Vera Language Reference

Vera is a programming language designed for LLMs to write. It uses typed slot references instead of variable names, requires contracts on every function, and makes all effects explicit.

Installation

Vera requires Python 3.11 or later. Node.js 22+ is optional (only needed for vera compile --target browser and browser parity tests).

Recommended — install from the GitHub source checkout. The checkout is the full environment this file teaches from: alongside the compiler and the vera CLI it carries the bundled examples/, the conformance suite in tests/conformance/ (minimal working programs, named by spec chapter and feature), and the specification in spec/:

git clone https://github.com/aallan/vera.git && cd vera
python -m venv .venv && source .venv/bin/activate   # Windows: .venv\Scripts\activate
python -m pip install -e .

For an editable source install with the language server, use python -m pip install -e ".[lsp]" — see LSP_SERVER.md. Verify the install end to end with the bundled example:

vera check examples/hello_world.vera    # prints "OK: examples/hello_world.vera"
vera run examples/hello_world.vera      # prints "Hello, World!"

Toolchain only — install the released veralang distribution from PyPI. This installs the vera command and all runtime dependencies (Lark parser, Z3 solver, wasmtime), but not the examples, conformance programs, or specification — those exist only in the checkout:

python -m venv .venv && source .venv/bin/activate   # Windows: .venv\Scripts\activate
python -m pip install veralang
vera version

For the language server on this route, install python -m pip install "veralang[lsp]".

If you are working on the compiler itself, install development dependencies too:

python -m pip install -e ".[dev]"

Platform support: README §Supported platforms lists the platforms and Python versions CI tests on, the ones that are out of scope (where install fails at dependency resolution), the workarounds, and the data behind the baseline.

For agents running in a sandbox (Claude.ai, Code Interpreter, container-based execution environments, etc.): the steps above work. Sandboxes typically have Python, git, pip, and outbound network access — that's all Vera needs. Run the install commands and verify with vera run examples/hello_world.vera before concluding that Vera "isn't available." Don't assume the sandbox lacks the toolchain — try it.

pip install vera installs a different package from PyPI (an ERAV citizen-science library — unrelated to this Vera). Use the veralang distribution or the GitHub source clone shown above; both install the vera command.