CAD Viewer

Start or reuse CAD Viewer and return review links for explicit CAD, implicit CAD, robot-description, and G-code files. Use when visually reviewing .step, `...

Provenance: maintained in earthtojake/text-to-cad. Use the installed local skill files as the runtime source of truth; the repository link is only for provenance and release review.

Use this skill to open existing or newly generated CAD, implicit CAD, robot-description, DXF, or plain FDM G-code files in CAD Viewer and hand back live review links. The expected input is one or more explicit file paths.

Start Viewer

Start or reuse one local CAD Viewer with npm run agent:start, passing the absolute artifact directory as --dir. The agent:start launcher owns port selection, compatible-server reuse, directory activation, and the ?dir= query parameter. Dev-mode viewers are reused only for matching git identities; dist bundle viewers can be reused across git branches when their viewer versions match. It activates reused servers through the Viewer's lightweight directory activation API, without requiring agents to probe ports or trigger catalog scans manually. Use the Viewer URL printed by agent:start as-is, then add only a file= query value for the artifact you want to review.

Choose --dir as the absolute directory that contains the model artifacts and sidecars, commonly <repo>/models or the consuming project's equivalent model directory. The file= value must be relative to that --dir. Do not manually choose ports, probe servers, rewrite ?dir=, or start a separate Viewer just to change directories.

Run from this skill directory:

bash

npm --prefix scripts/viewer run agent:start -- --host 127.0.0.1 --dir <absolute-model-root>

Use the printed Viewer URL and append file=:

bash

http://127.0.0.1:<printed-port>/?dir=/absolute/project/models&file=path/to/model.step

If a non-Viewer process or another worktree's Viewer occupies the candidate port, the launcher will continue automatically. In sandboxed agent environments, local binding or probe failures such as EPERM or EACCES can be expected; rerun the same command with the needed permission/escalation.

Links

• Before returning any file= link, resolve <dir>/<file> and confirm the artifact exists. Pass the generated artifact (e.g. .step), not its generator source (e.g. .py). If the resolved path is missing, do not return the link, and instead report the problem and point to the correct generated artifact path.
• Return one Viewer URL per requested file.
• Start/reuse the Viewer once per absolute directory --dir, then append file=<path> for each requested file. The file path must be relative to --dir.
• For directory-only review links, return the URL printed by agent:start without adding file=.
• Do not stop an existing Viewer server unless the user asks.
• If Viewer startup fails, report the failure and continue with the owning skill's non-GUI validation or artifacts.

Claude Preview

The viewer port is dynamic — it is chosen at startup and may differ across worktrees. To integrate with the Claude Preview tool, add --json to the agent:start command:

bash

npm --prefix scripts/viewer run agent:start -- --host 127.0.0.1 --dir <absolute-model-root> --json

The launcher writes a JSON result line to stdout after the human-readable lines. Parse it by taking the last line of stdout that begins with {:

json

{"url":"http://127.0.0.1:<port>/?dir=<absolute-model-root>","port":<port>,"action":"reuse"}

action is "reuse" when an existing server was reused and is immediately ready, or "start" when a new server process was spawned and may still be initializing. For a "start" result, probe GET /__cad/server on the base URL (e.g. http://127.0.0.1:<port>/__cad/server) until it returns HTTP 200 before passing the url value to the Claude Preview tool.

References

• Read references/development.md when the user asks to modify, debug, or iterate on CAD Viewer source.
• Read references/viewer-features.md when you need supported file types, Viewer controls, or file-specific feature details.
• Read references/moveit2-server.md only when the user specifically needs optional SRDF MoveIt2 IK or path-planning controls.