Natural-language-driven CAE pipeline for DeepSeek Harness: the agent takes a plain-language simulation request and drives a complete CAD → mesh → solve → post-process chain over build123d, Gmsh, CalculiX, OpenFOAM, and PyVista. Six tools cover the chain end to end — geometry construction, tetrahedral meshing, linear static solving, result extraction/plotting, and a parallel CFD chain (blockMesh → steady incompressible solve → post) for internal-flow requests — with receipts (paths, volumes, mesh quality, field extremes) fed back to the model after every stage.

Install

Python stack first: pip install build123d gmsh pyvista ccx2paraview, plus a CalculiX solver — sudo apt install calculix-ccx on Debian/Ubuntu or conda install -c conda-forge calculix elsewhere (the ccx binary must be on PATH). For the CFD chain, OpenFOAM (Foundation v11–13 or ESI) must be installed; its etc/bashrc is auto-detected ($FOAM_BASHRC, /opt/openfoam*, /usr/lib/openfoam*) or set via openfoamBashrc. Then load the plugin into a profile — run dsh from a DeepSeek Harness checkout:

• Local checkout (plugin development): dsh plugin --profile web add /path/to/dsh-cae — installs as a link: dependency; after changing the plugin, pnpm build and restart the surface to pick it up.
• Direct git checkout: dsh plugin --profile web add https://github.com/DaiYuhangSustc/dsh-cae-plugin.git (git installs run the prepare build script; pnpm users may need to allow it via allowBuilds).
• npm registry (once published): dsh plugin --profile web add dsh-cae.

Each profile holds its own plugin list — repeat the add for every profile you use (e.g. headless).

Launch and use

• Browser: dsh web boots the web UI on http://127.0.0.1:3080 (--port to change; it opens the default browser automatically) — paste a plain-language request and watch the tool calls and receipts stream.
• Terminal: dsh --profile headless "20×20 mm square duct, 1 m long, water at 0.02 m/s inlet — steady laminar solve and a pressure contour" runs one task headlessly and prints the transcript. A surface started before the plugin was added cannot see it — restart the surface after add (or after a rebuild, for link: installs).

Try it

See examples/cantilever.md: a single Chinese sentence produces a fixed-end cantilever under tip load, solved on coarse and refined meshes with a von Mises contour and a mesh-independence check. And examples/duct-flow.md: one Chinese sentence produces a laminar duct-flow solution validated against the Shah–London friction constant.

The six tools

Tool	Input	Output
cae_cad_build	build123d script (defines part, optional NAMED_FACES) + name	.step path, volume, bounding box, named faces with areas/centroids
cae_mesh_generate	.step path, elementSizeMm, elementType (tet4/tet10)	.msh path, node/element counts, quality metrics
cae_solve_static	.msh path, material (youngMPa, poisson), loads/boundary conditions on named faces	.frd/.vtu paths, solver log tail, reaction summary
cae_post_process	.vtu/.frd path, field/point/plot queries	field extremes with locations, point values, contour PNG paths
cae_cfd_mesh	duct lengthMm/widthMm/heightMm/cellSizeMm (+ wallGrading, full blockMeshDict text, name)	caseDir (SI bounds, cell count, checkMesh quality, checksPassed)
cae_cfd_steady	caseDir, inletVelocityMS, kinematicViscosityM2S, densityKgM3, iterations, dict overrides	solver log tail, converged + final residuals, VTK path

Trust boundary

The script parameter is model-generated Python (and batch text) executed locally with trust level equal to the harness's own bash tool; treat it accordingly and use a profile permission layer (tools/pre-execute) for governance.

Units

Millimeters, newtons, megapascals everywhere: geometry in mm, forces in N, stresses in MPa, so deflections come out in mm and Young's modulus is entered as MPa (steel ≈ 210000). The CFD chain takes geometry in mm at cae_cfd_mesh (converted to m once) and is SI afterwards: m, m/s, Pa, Pa·s; cae_post_process converts kinematic pressure to Pa when given densityKgM3.

Configuration

Field	Default	Meaning
python	python3	Interpreter with build123d/gmsh/pyvista/ccx2paraview importable (CalculiX ccx on PATH)
workdir	./cae	Artifact directory (relative to agent cwd) for STEP/MSH/INP/FRD/VTU/PNG files
stageTimeoutMs	600000	Per-stage wall-clock budget in ms; exceeded kills the stage process group
openfoamBashrc	auto-detect	OpenFOAM etc/bashrc path; auto-detection checks $FOAM_BASHRC, /opt/openfoam*/etc/bashrc, /usr/lib/openfoam/*/etc/bashrc

Troubleshooting

If import build123d dies with pyexpat ... undefined symbol: XML_SetAllocTrackerActivationThreshold, the OCP wheel loaded an older bundled libexpat than your interpreter's: start Python with LD_PRELOAD=$(python -c 'import sysconfig; print(sysconfig.get_paths()["stdlib"])')/../../lib/libexpat.so.1 (or your env's libexpat path) to force the newer one first. Linux servers without a display need EGL or OSMesa for PyVista rendering — prefer conda's vtk, which ships an OSMesa-capable build via conda install -c conda-forge vtk osmesa; CI sets PYVISTA_OFF_SCREEN=true, under which vtk renders off-screen without X. OpenFOAM 11+ (Foundation) replaced standalone solvers: this plugin runs foamRun (solver incompressibleFluid), the simpleFoam successor; ESI releases keep simpleFoam but the invoked names here are Foundation's. foamToVTK writes legacy .vtk, which cae_post_process reads directly.

Limitations

Structural: linear static analysis only, tetrahedral meshes only; CFD: steady incompressible laminar internal flow only, block-hex meshes only; POSIX only; single-machine.

Roadmap

CAE skill for prompt guidance, background jobs via ctx.jobs, modal/thermal analysis, turbulence (kOmegaSST + y+ treatment), snappyHexMesh/STL geometry, pluggable solver providers.

Contributing

PRs and issues are welcome — a natural-language CAE stack covers a lot of ground, and it needs many hands: more physics, more solvers, better examples and docs.

Development setup (TS side): pnpm install. Note: @deepseek-ai/dsh-tools is at rc.1 and its runtime import chain pulls dsh-llm/dsh-scope/dsh-session/dsh-timeout; when installed out-of-tree into a profile, resolution normally comes from the in-profile dsh-base. For a standalone dev checkout, pnpm install needs autoInstallPeers: false (already in pnpm-workspace.yaml) plus the declared extra devDeps — if peers still fail to resolve, install within a dsh profile rather than standalone.

Kernel environment, no sudo required (the route CI-equivalent validation uses locally):

conda create -n dsh-cae -c conda-forge python=3.11 calculix -y
conda run -n dsh-cae python -m ensurepip --upgrade
conda run -n dsh-cae pip install build123d gmsh pyvista ccx2paraview pytest

Run the suite that matches your change:

Layer	Command	Notes
TS tools / runner	pnpm build && pnpm vitest run	keyless, runs everywhere
Python stages	pytest pytest -v	inside the kernel env; the pytest/ directory shadows the pytest package, so the console script is required — never python -m pytest from the repo root
Loader composition	DSH_COMPOSITION=1 pnpm vitest run tests/composition.e2e.ts	needs a dsh harness checkout; opt-in, CI does not gate it

Contracts every change must keep:

• The TS layer owns orchestration only (tool schemas, subprocesses, timeouts, receipts); all domain knowledge lives in python/dsh_cae/. The layers couple through argv and the stdout receipt line <<<DSH_CAE_JSON>>> — nothing else.
• Solver outcomes are data: a non-zero ccx exit is a normal receipt carrying exitCode and logTail for the model to diagnose; only infrastructure failures (missing binary, timeout, unparseable output) raise.
• Units are mm/N/MPa everywhere, with no conversion anywhere.
• Some solver realities are encoded deliberately, with comments: Gmsh tet10 mid-edge nodes 9/10 are swapped against Abaqus C3D10 in solve.py; ccx exits 0 even on a singular (unconstrained) system, so the domain-failure test drives ccx with a *CLOAD on a nonexistent node.

PR expectations: the tests covering your layer are green; kernel tests self-skip without kernels — say so in the PR and let CI run them for real; update README.md and README.zh.md together (the two files mirror each other); conventional commit subjects (feat:, fix:, docs:, test:).

Good first targets are the Roadmap items above: a new analysis type (*FREQUENCY, *HEAT TRANSFER), turbulence and snappyHexMesh extensions on top of the CFD chain, a cae skill teaching the model build123d/INP idioms, and more runnable examples in the style of examples/cantilever.md.

License

MIT