chemvas

Chemvas — 2D chemical structure drawing canvas

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Chemvas is a lightweight PyQt6 app for drawing 2D chemical structures and reaction schemes — ACS 1996 defaults, ChemDraw-compatible shortcuts, and publication-ready figure export. Draw fast, export exactly.

Chemvas — a C–P bond cleavage reaction scheme (KOtBu / THF) drawn on the canvas

Statement of need

Sketching a scheme for a lab notebook or paper should not require a commercial suite — and automating edits should not mean trusting an LLM with your drawing. Chemvas keeps the interactive canvas small and fast, and exposes headless CLI contracts for rendering, inspection, editing, and calculation handoff: document edits bind to the exact source hash and unsupported input fails closed. Agents propose, validation decides.

Quickstart

pip install chemvas              # core (PyQt6 included)
pip install "chemvas[rdkit]"     # + SMILES import, formula/weight, 3D
chemvas

Pick a tool from the toolbar and click/drag on the canvas. Type a SMILES string and press Insert to preview and place it (RDKit). Open examples/template2.chemvas via File ▸ Open to explore the document shown above.

What it does

Capability	Use it for	Details
Drawing	bonds, rings, arrows, brackets, atom labels — with ChemDraw-compatible shortcuts	REFERENCE
Figure export	plain SVG / PDF / PNG / TIFF, outlined glyphs, deterministic physical sizing	REFERENCE
Chemistry I/O	SMILES import, `.mol` interchange, 2D→3D `.xyz`, Molecule Info (RDKit)	REFERENCE
Agent CLI	headless compose / layout-check / render / inspect / hash-gated Graph Patch, no Qt window	AGENT_CLI
Calculation handoff	elementary steps, reviewed precomplexes, one `machine.json` per step	AGENT_CLI

Documents are .chemvas files (JSON, version 7 contract) with autosave and crash recovery; everything except the marked (RDKit) features runs without RDKit.

Development, testing, and full docs

make check runs the whole local gate — lint, formatting, mypy, the file-isolated headless test suite, and the machine.json conformance check. Read CONTRIBUTING.md before moving code: the architecture boundaries are enforced by tests.
Docs index: REFERENCE · AGENT_CLI · ARCHITECTURE · CHANGELOG · RELEASING
Known gaps (SDF interchange, one-file binaries, multi-molecule 3D export) → roadmap

License

MIT License

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chemvas-0.4.0.tar.gz (1.2 MB view details)

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Provenance

The following attestation bundles were made for chemvas-0.4.0.tar.gz:

Publisher: release.yml on dhsohn/Chemvas

Attestations: Values shown here reflect the state when the release was signed and may no longer be current.

Statement:
- Statement type: https://in-toto.io/Statement/v1
- Predicate type: https://docs.pypi.org/attestations/publish/v1
- Subject name: chemvas-0.4.0.tar.gz
- Subject digest: 8858a6edd86a0d091b5f573218253906a0275167aa0cc3414bcd74a9903296e2
- Sigstore transparency entry: 2498222516
- Sigstore integration time: Aug 17, 2026
Source repository:
- Permalink: dhsohn/Chemvas@95837b075579700609526304d1fa28ba1fd8cdf5
- Branch / Tag: refs/tags/v0.4.0
- Owner: https://github.com/dhsohn
- Access: public
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- Token Issuer: https://token.actions.githubusercontent.com
- Runner Environment: github-hosted
- Publication workflow: release.yml@95837b075579700609526304d1fa28ba1fd8cdf5
- Trigger Event: push