Engineering is where the gap between a number on a screen and a fact in the world matters most. A stress value from a solver, a slicer’s print-time estimate and a caliper reading can all look like the same kind of number. They are not. JARVIS’s engineering layer is built to keep them apart, and to keep every software step apart from anything that moves a physical machine.
Units and quantities
All engineering maths uses a Quantity type that carries its dimensions across the seven SI base units. Converting a quantity straight to a plain number raises an error (“A quantity is not a number.”), so a value cannot silently lose its units halfway through a calculation. Unit errors are rejected. This is one of the capabilities the registry recorded LIVE, on 17 September 2026 (a historical reading).
Around this core, production has modules for reference frames, a parametric model, mesh validation and repair (writing STL and GLB), design of experiments, bounded optimisation, a run registry that records uncertainty, and a solver host. In tests, a spoken request can run a real CalculiX finite-element solve under WSL and light the engineering panel on the HUD.
CAD with FreeCAD (Advanced branch)
The Advanced Systems branch, which is not merged into production, adds governed FreeCAD operations on STEP files. They include booleans, centre and plane splits, component extraction, transform and mirror, edges and fillets, offsets, face listing and extension, and sealed hollowing. FreeCAD runs only fixed, isolated scripts: “No caller-supplied Python is executed.” A model or a web page cannot turn a CAD request into arbitrary code.
Every operation is journaled through four phases: PREPARED, CALCULATED, FILE_VERIFIED and REGISTERED. Every result carries evidence_class: CALCULATION. Project revisions use compare-and-set with E-stop commit fences, so two edits cannot silently overwrite each other and an E-stop can stop a commit. If an attempt is interrupted, it keeps its last durable phase for explicit reconciliation. It is never replayed blindly.
The limits are stated plainly. This is not a revision history graph, not a general feature engine and not natural-language CAD. A split is not an atomic two-file transaction.
There is also an open contradiction. Production’s own tool survey found FreeCAD absent from the system path, while the Advanced proofs used an installed FreeCAD 1.1.x. It is likely installed or located differently now, but that is uncertain.
The spatial engineering workspace (Advanced branch)
SceneStore holds a revision-bound 3D scene of at most 64 objects, 64 KiB and 4,096 revisions. It supports comparing revisions, labels and selective restore. It imports STL, OBJ and 3MF, displays STEP, and allows spinning a model under an E-stop lease. It renders with three.js inside the single HUD.
One rule stops the scene being mistaken for engineering truth: “Object transforms describe display placement, not CAD edits, fabrication dimensions, or observations of physical objects.” Moving a part on screen changes nothing about the design.
Trade spaces (Advanced branch)
A run registry records stamped values, evaluates constraints, archives evidence, draws a trade-off frontier and supports resumable sweeps, with plots on the HUD. The project is explicit about what a frontier is not: “Nominal frontier is not feasibility, causal comparability, uncertainty propagation, a global optimum, design promotion or physical approval.”
Slicing and print preparation
In production, OrcaSlicer runs as a sandboxed subprocess with exact profiles. It produces a G-code report and a job manifest with file hashes. The printer is reached over the local network, and its address must be private or loopback.
On the Advanced branch, STEP files are first converted to a verified slicing mesh through FreeCAD. This step exists because the installed OrcaSlicer 2.4.2 rejected STEP input, and that failure is kept as a receipt. The slicing commands publish time and filament estimates. For a synthetic 10 mm test cube, the slicer estimated 325 s and 0.73 g. That is an ESTIMATE on a fixture. Nothing was printed and nothing was weighed.
Print readiness, also Advanced-only, gives READY, NOT READY and WHY across nine checks. “READY IS SOFTWARE READINESS AND NOTHING MORE.”
Calculation, simulation, estimate, measurement, physical result
These five kinds of result are never merged, on the HUD or on this site:
| Kind | What it is | Example in JARVIS | What it cannot tell you |
|---|---|---|---|
| CALCULATION | Computed from a model or formula | Unit-checked arithmetic; FreeCAD STEP results stamped CALCULATION | Whether the real part matches the model |
| SIMULATION | A numerical model of behaviour | A finite-element solve such as CalculiX’s | How the physical part actually behaves |
| ESTIMATE | A tool’s prediction of cost or duration | The slicer’s 325 s and 0.73 g for a synthetic cube | How long a real print took or what it weighed |
| MEASUREMENT | An instrumented reading of a real object | None recorded for a physical part in the evidence this site uses | |
| PHYSICAL RESULT | A real-world outcome that was inspected | None. There is no evidence JARVIS has ever started a print. |
Why so strict? A calculated value shown as measured invites trust it has not earned. On the HUD, computed and simulated values have their own colour, distinct from measured ones, and status is never carried by colour alone. The “verified physical results” surface renders only when a real evidence chain exists. The project treats a solver value appearing there as a truth-state violation. As one of its method lessons puts it: “Arithmetic about a property is not the property.”
The physical door
Printing is called “the first irreversible physical capability” in the project’s printer order. Starting a print needs all of the following:
- a fresh, single-use approval bound to the G-code hash
- a responsible-adult attestation
- the E-stop clear
- re-validated G-code
- a proven stop path
- nothing already printing
Today the final send always refuses. Pause and stop are the E-stop’s physical arm and are never gated, because stopping a machine must never wait on an approval. See governance.
What is not proven yet
- No print has been started. Physical printing is a concept by design, and there is no evidence JARVIS has ever started one.
- No physical measurement of a produced part appears in the evidence this site uses.
- CAD, the 3D scene, trade spaces, STEP slicing and print readiness are on the Advanced branch only, not merged into production. Their live proofs used synthetic fixtures.
- The CalculiX solve is tested, not live-proven.
- FreeCAD availability in production is uncertain.
- Registry engineering rows are mostly BLOCKED. They are CAP-ENG-03 to 31, and the project later partly corrected the reasons behind those blocks. The unit-safety LIVE reading dates from 17 September 2026.