Vera language skill
The vera-language skill teaches an agent to write Vera, a language with required contracts, compiler checks, no variable names.
- 421 ★ on the repository
- Last commit
- MIT
Minimal access
Why this level
- Installs a compiler and runs Vera programs in a normal runtime; no access to external systems.
Install
- Works in
In your terminal, with SkillFoxx CLI
npx skillfoxx add skills/vera-languageDetects the agents on your machine, shows the access level and pins the version.
Other ways to install
Access and checks
How we reviewMinimal accessThe tool runs nothing and makes no network calls.
- Installs a compiler and runs Vera programs in a normal runtime; no access to external systems.
This is third-party code. Review the repository files before installing.
What it does
The `SKILL.md` file at the repository root describes Vera: typed references like `@Int.0` instead of variable names, mandatory `requires` and `ensures`, explicit effects and compiler diagnostics. An agent uses it to write, edit and check `.vera` files. The compiler installs from PyPI as `veralang`, and the command stays `vera`. `vera check` and `vera verify` return diagnostics with description, rationale and spec reference, so the agent fixes a program from compiler answers. Programs compile to WebAssembly.
Who it is for. Language researchers and experimenters who want to see how an agent copes with a language built for models.
Good fit when
- An agent must write a Vera program with provable contracts.
- A `vera verify` error must be fixed from the compiler hint.
- A program is compiled to WebAssembly for the browser or WASI.
- Vera's approach is compared with Dafny, Lean and Koka.
Not a fit when
- A production language with a large library ecosystem is needed.
- The project is already written in another language and no port is planned.
- Integration with existing systems is needed; Vera has no direct call into other-language code.
Example request
Write a safe-division function in Vera with contracts and run `vera verify`, fixing errors from the compiler's answers.Limitations
Vera is a young research language with a narrow ecosystem. Version 0.2.0 is stricter than 0.1.x: the compiler now rejects some earlier programs. The PyPI wheel carries only the compiler; examples and the specification live in the repository, so a source install is recommended for agents. `pip install vera` installs an unrelated project. macOS 14 and older and Linux aarch64 with glibc below 2.38 are unsupported.
How to disable. Delete `SKILL.md` or the skill folder from the agent skills directory and the `.venv` environment that holds `veralang`.
FAQ
How is the compiler installed?
With `python -m pip install veralang` inside a virtual environment. The command is named `vera`.
Is Node.js required?
No, only for `vera compile --target browser` and parity tests, version 22 or newer.
Where are the examples?
In the repository: the `examples/` directory, `tests/conformance/` and the specification. The PyPI wheel does not include them.
Is editor support available?
Yes, `vera lsp` via the `veralang[lsp]` extra provides diagnostics and hints in editors.
What does vera verify check?
The `requires` and `ensures` contracts of functions. What cannot be proved statically becomes a runtime check.
Discussion
No questions or reviews yet.
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README in short
The README explains the language-for-models idea, shows contract examples, the `vera check` and `vera verify` commands and lists files for agents.