jaunt 0.3.2

Spec-driven code generation framework: write intent as decorated Python stubs, generate implementations and tests with LLMs.

Jaunt

_{William Blake, The Tyger, plate 42 from Songs of Experience (1794). The Metropolitan Museum of Art, Open Access.}

Tyger Tyger, burning bright, In the forests of the night; What immortal hand or eye, Could frame thy fearful symmetry?

-- William Blake, via Alfred Bester's The Stars My Destination

Jaunt is a small Python library + CLI for spec-driven code generation:

• Write implementation intent as normal Python stubs decorated with @jaunt.magic(...).
• Optionally write test intent as stubs decorated with @jaunt.test(...).
• Jaunt generates real modules under __generated__/ using an LLM backend (OpenAI, Anthropic, or Cerebras).
• Async support is available for both implementation and test specs through async def plus the build.async_runner setting.
• @magic works on individual class methods too — decorate instance methods, @classmethod, @staticmethod, or @abstractmethod stubs and Jaunt generates only those methods while preserving the rest of the class.

Installation

pip install jaunt[openai]      # for OpenAI
pip install jaunt[anthropic]   # for Anthropic/Claude
pip install jaunt[cerebras]    # for Cerebras
pip install jaunt[all]         # both providers

Quickstart (This Repo)

Prereqs: uv installed.

uv sync
export OPENAI_API_KEY=...   # or ANTHROPIC_API_KEY for Claude
uv run jaunt --version

See docs-site/ for rendered docs, or DOCS.md for a plain-text walkthrough.

All examples live under examples/. See examples/README.md for the full list.

Hackathon Demo (JWT Auth)

Headline demo: JWT auth (the "wow gap" example: short spec, real generated glue + tests).

# Generate implementations for @jaunt.magic specs.
uv run jaunt build --root examples/jwt_auth

# Generate pytest tests for @jaunt.test specs and run them.
PYTHONPATH=examples/jwt_auth/src uv run jaunt test --root examples/jwt_auth

Eval Suite

Run the built-in eval suite against your configured backend:

uv run jaunt eval
uv run jaunt eval --model gpt-4o
uv run jaunt eval --provider anthropic --model claude-sonnet-4-5-20250929

Compare explicit provider/model targets:

uv run jaunt eval --compare openai:gpt-4o anthropic:claude-sonnet-4-5-20250929

Eval outputs are written under .jaunt/evals/<timestamp>/.

Eval Results (2026-02-15 UTC)

Run (UTC)	Mode	Target	Reasoning	Passed	Failed	Skipped	Total	Notes	Artifacts
2026-02-15T21-34-58Z	single	cerebras:gpt-oss-120b	none	0	10	0	10	Missing cerebras-cloud-sdk dependency	examples/expr_eval/.jaunt/evals/2026-02-15T21-34-58Z
2026-02-15T21-35-17Z	single	cerebras:gpt-oss-120b	none	0	10	0	10	Cerebras 402 payment_required quota/billing error	examples/expr_eval/.jaunt/evals/2026-02-15T21-35-17Z
2026-02-15T21-36-54Z	single	cerebras:gpt-oss-120b	none	10	0	0	10	All eval cases passed	examples/expr_eval/.jaunt/evals/2026-02-15T21-36-54Z
2026-02-15T22-01-24Z-custom-compare	compare	cerebras:gpt-oss-120b	low	10	0	0	10	All eval cases passed	examples/expr_eval/.jaunt/evals/2026-02-15T22-01-24Z-custom-compare
2026-02-15T22-01-24Z-custom-compare	compare	openai:gpt-5.2	none	10	0	0	10	All eval cases passed	examples/expr_eval/.jaunt/evals/2026-02-15T22-01-24Z-custom-compare
2026-02-15T22-01-24Z-custom-compare	compare	anthropic:opus-4.6	none	0	10	0	10	Anthropic 404 not_found_error for model name	examples/expr_eval/.jaunt/evals/2026-02-15T22-01-24Z-custom-compare
2026-02-15T22-04-19Z-custom-compare	compare	cerebras:gpt-oss-120b	low	10	0	0	10	All eval cases passed	examples/expr_eval/.jaunt/evals/2026-02-15T22-04-19Z-custom-compare
2026-02-15T22-04-19Z-custom-compare	compare	openai:gpt-5.2	none	10	0	0	10	All eval cases passed	examples/expr_eval/.jaunt/evals/2026-02-15T22-04-19Z-custom-compare
2026-02-15T22-04-19Z-custom-compare	compare	anthropic:claude-haiku-4-5	none	9	1	0	10	One assertion failure (example_slugify_smoke)	examples/expr_eval/.jaunt/evals/2026-02-15T22-04-19Z-custom-compare

Prompt snapshots:

uv run pytest tests/test_prompt_snapshots.py --snapshot-update

Auto-Generate PyPI Skills (Build)

jaunt build includes a best-effort pre-build step that auto-generates “skills” for external libraries your project imports and injects them into the build prompt.

What happens:

• Scan paths.source_roots for import ... / from ... import ... (ignores stdlib, internal modules, and relative imports).
• Resolve imports to installed PyPI distributions + versions from the current environment.
• Ensure a skill exists per distribution at:
  • <project_root>/.agents/skills/<dist-normalized>/SKILL.md
• If missing/outdated, fetch the exact PyPI README for <dist>==<version> and generate SKILL.md using the configured LLM provider.
• Inject the concatenated skills text into the build LLM prompt.

Overwrite rules:

• Jaunt only overwrites a skill if it was previously Jaunt-generated (it has a <!-- jaunt:skill=pypi ... --> header) and the installed version changed.
• If the header is missing, the file is treated as user-managed and will never be overwritten.

Failure mode: warnings to stderr, and the build continues without missing skills.

Docs Site (Fumadocs)

The repository includes a Fumadocs (Next.js) documentation site under docs-site/.

cd docs-site
npm run dev

Publish to PyPI

If you keep your token in .env as UV_PUBLISH_TOKEN=..., load it into your shell first:

set -a
source .env
set +a

Build and validate artifacts:

uv build
uvx twine check dist/*

Upload to PyPI:

uv publish --check-url https://pypi.org/simple/

Dev

uv run ruff check .
uv run ty check
uv run pytest

Why "Jaunt"?

Named after jaunting -- teleportation by thought alone -- from Alfred Bester's 1956 novel The Stars My Destination (originally published as Tiger! Tiger!). You think about where you want to be, and you're there.

Jaunt works the same way: describe your intent, and arrive at working code.

The forge-and-furnace imagery you'll find scattered through the codebase comes from William Blake's poem "The Tyger," which Bester used as the novel's epigraph and alternate title. The poem's vision of creation -- hammer, chain, furnace, anvil -- mirrors the act of forging code from pure specification.