spek

Turn a SPEC.md into an installable, tested Python package.

spek is a small LLM-powered coding agent. You write a markdown file describing what you want, point spek at it, and a few minutes later there's a working Python package on disk that builds and passes its own tests.

For the design rationale and a worked example end-to-end, see Here is how I built a simple coding agent.

Requirements

• Python 3.11+
• uv (recommended) or pip
• A running Docker daemon — spek runs every shell command and file write inside a sandboxed container. If Docker isn't running, spek build refuses to start.
• An Anthropic API key in the environment (ANTHROPIC_API_KEY).

Install

The PyPI distribution is spek-cli; the binary is still spek:

uv tool install spek-cli      # recommended: isolated, on $PATH
# or:
pip install spek-cli

Verify:

spek --help

Configure credentials

spek looks for .env in the current directory or any ancestor of the spec file. Copy the template and fill it in:

cp .env.example .env
$EDITOR .env                  # paste your ANTHROPIC_API_KEY

You can also override the model:

ANTHROPIC_API_KEY=sk-ant-...
ANTHROPIC_MODEL=claude-sonnet-4-6        # optional
ANTHROPIC_BASE_URL=https://api.anthropic.com   # optional, for proxies

Quick start

Two commands:

spek init my-project                           # scaffold SPEC.md skeleton
$EDITOR my-project/SPEC.md                     # describe what you want
spek build my-project/SPEC.md \
  --workdir my-project --confirm-plan          # run the agent

When the run finishes green, my-project/ contains a normal Python project (pyproject.toml, src/, tests/) you can use immediately:

cd my-project
uv run pytest                                  # tests pass
uv run <your-cli> --help                       # the binary you specified

A real example

The repo ships with a worked example at examples/weather-tool/SPEC.md:

spek build examples/weather-tool/SPEC.md --workdir /tmp/weather

A run produces a working weather-converter CLI with 27 tests passing. The full session log and final plan are described in BLOG.md.

CLI

spek --help

usage: spek [-h] {init,build} ...

  init     Scaffold an empty SPEC.md and .spek/.
  build    Run the agent against a SPEC.md spec.

Useful spek build flags:

What spek writes

Everything is scoped to the working directory. After a successful run:

<workdir>/
├── SPEC.md                   # your input (untouched)
├── pyproject.toml            # generated
├── src/...                   # generated
├── tests/...                 # generated
└── .spek/
    ├── journal.jsonl         # full event log (resume + audit)
    ├── plan.md               # the plan (numbered checklist)
    └── command_config.json   # build/test/lint commands the agent uses

There is no global state and no ~/.config/spek. Wipe .spek/ and the next run starts from scratch.

Development

make install       # uv-managed venv with dev extras
make test          # pytest
make lint          # ruff + black --check
make typecheck     # mypy strict
make build         # sdist + wheel into ./dist

Full target list: make help.

License

MIT.