One model.
Two operators.

Getting started

PartMode is local-first parametric CAD in the browser. OpenCascade evaluates exact B-rep geometry on your device. You do not need an account to model, save a project, or export a part. This browser-local workflow is separate from the optional server-headless agent workflow, which requires explicit per-key consent and stores committed documents under the account.

Build a part as a person

1. Open PartMode and choose Start blank or Templates.
2. Start with Extrude, Cut, or Revolve and choose a base plane or supported planar face.
3. Draw a closed profile and type exact dimensions in millimetres.
4. Apply the feature. Add later operations from the feature ribbon and inspect them in History.
5. Use parameters for dimensions that should rebuild together.
6. Save the editable project file before clearing browser data.

The template library creates normal editable documents. A template is a starting recipe, not a screenshot or decorative mesh.

Read the model state

• History is the ordered construction recipe.
• Bodies shows exact solids and visibility state.
• Parameters holds reusable expressions and dimensions.
• CFG selects a stored part configuration when the document defines a design table.
• Inspector shows the selected feature, body, occurrence, mate, or measurement.

PartMode reports rebuild errors instead of silently treating a failed edit as valid geometry. A visible shaded model is useful feedback, but exact completion is established by settled document revision, valid B-rep evidence, and the requested export or query result.

Save and exchange

• Project file preserves the editable schema-5 document.
• STEP exchanges exact CAD bodies and assembly structure with other CAD systems.
• STL exports tessellated geometry for mesh workflows such as printing.
• Drawing exports an SVG sheet generated from the active, settled configuration.

Browser recovery is a convenience, not a substitute for downloading an important project file.

Reopen an older project safely

PartMode preserves a narrow set of historical schema-5 feature intent when an older saved project is reopened. This includes sampled controlled twist, asymmetric loft continuity, tangent propagation, and Boolean Split tool-removal semantics. The compatibility markers survive save and recovery, while newly authored features still use the current strict contracts.

Compatibility preservation means the original project remains recoverable; it does not make those historical semantics newly authorable exact Professional Core features. If an active browser project fails validation, PartMode protects its stored bytes from fallback autosaves until you explicitly open, recover, or start another project.

Configurations and drawings

A part configuration is a named set of parameter overrides stored inside the project. The active configuration drives rebuild, validation, inspection, drawing generation, STEP and STL export, and pattern freezing through the same effective document.

Switch configuration as a person

1. Open CFG in the application bar.
2. Choose a configuration from the design table.
3. Wait for the local kernel and document revision to settle.
4. Inspect the dimensions and exact body state.
5. Open Output and export Drawing, STEP, STL, or Project file.

The exported artifact records the active configuration and effective-document evidence. Switching back to the same configuration must reproduce the same canonical document and exact geometry for unchanged inputs.

Switch configuration and export as an agent

1. Read partmode://help/agent-workflow.
2. Connect to a visible, browser-approved PartMode tab containing the configured

project. The public headless API cannot currently import that browser project or template, or create a configuration table.

3. Call cad_capabilities and use only operations and artifacts advertised by

that live build.

4. Preview a configuration.activate operation with the target configuration ID.
5. Commit the exact preview after approval, then inspect the settled configuration and geometry.
6. In a browser session, call cad_artifact for drawing-svg or another

advertised format. Artifact generation uses the settled project revision and active effective document.

Do not edit individual table-driven parameters as a substitute for activating a configuration unless the document explicitly supports that workflow.

A server-headless session can author supported typed geometry in its own durable document and use partmode_headless_export_step for exact STEP. It cannot currently import a configured browser project or template, create a configuration table, or use cad_artifact. Configuration activation and the AS4395B configured drawing demonstration therefore require the browser path.

What a drawing contains

PartMode drawings combine exact OpenCascade hidden-line-removal projections with document-owned drawing instructions. A configured part may add a profile-derived section, limit dimensions, tolerances, notes, symbols, tables, and a title block.

Exact projection evidence does not make every annotation a certified manufacturing requirement. The project owns the drawing recipe, and engineering review remains responsible for its completeness, standard revision, units, tolerances, and release status.

General parts and assemblies can produce compact SVG drawing sheets. A persisted part-specific recipe can produce a larger standards-oriented sheet such as the A3 AS4395B demonstration.

Agent workflow

PartMode agents use typed MCP operations, not pointer automation. An agent key authenticates the agent account. CAD authority comes from one of two distinct choices made by the account owner:

• Browser-approved local project: a normal key can request a visible,

project-scoped session in a signed-in PartMode tab. The project stays in that browser. Every session requires approval in the tab.

• Server-headless durable project: an edit key created with the explicit

headless grant can open an account-owned project on the PartMode server with no browser or per-session approval. The grant is per key, cannot be added later, and means the server stores the committed project document.

A key without the headless grant cannot open a server-headless project. A key by itself also cannot invent a browser session.

Set up hosted MCP

1. Open Agent access, create or sign in to a PartMode account, and

create a revocable agent key.

2. For local browser projects, leave Allow headless server sessions off. For

unattended server execution, create an edit key and deliberately enable that grant after reading the storage notice.

3. Store the key in the secret environment used to launch the agent. Do not

paste it into a prompt, URL, command argument, or project file.

4. Configure the hosted endpoint.

codex mcp add partmode --url https://partmode.com/mcp --bearer-token-env-var PARTMODE_AGENT_KEY

1. Start a new agent session and read the MCP Help resources.

Work with a browser-approved local project

1. Keep the intended project open in a signed-in PartMode CAD tab.
2. Call partmode_list_studios. Discovery returns non-project tab identity

only.

3. Call partmode_connect for the chosen tab, the smallest required permission

set, and a bounded commit budget.

4. Wait for the person to approve the visible connection request.
5. Call cad_capabilities. This live manifest is authoritative for operations,

schemas, limits, and artifact support.

6. Use cad_inspect and cad_query to establish exact current state.
7. Use cad_preview for a typed transaction. Review the diagnostic and visible

browser preview.

8. Use cad_commit only with the returned preview ID and matching revision.
9. Inspect the settled result and call partmode_disconnect when finished.

The browser remains the enforcement point. The person can reject a request, pause or disconnect the session, reject a preview, or revoke the key. The browser project and recovery data stay on that device. Commands and results cross the hosted relay over HTTPS and remain only in bounded process memory. There is no offline queue, and the relay is not end-to-end encrypted.

Work with a server-headless durable project

1. Use an edit key that was created with Allow headless server sessions.
2. Call partmode_headless_open with a stable projectId, an optional project

name and units, the smallest permissions needed, a bounded session duration, and a bounded commit budget.

3. Call cad_capabilities, then use cad_inspect, cad_query, cad_preview,

cad_commit, and supported cad_history actions against the returned session ID.

4. Call partmode_headless_export_step when an exact STEP artifact is needed.
5. Inspect the settled revision and document hash, then call

partmode_disconnect when finished.

Headless sessions are temporary, key-bound execution contexts. They expire in at most one hour and do not survive a service restart. Committed headless documents are different: PartMode stores the project ID, project name, revision, full document JSON, canonical document hash, and timestamps under the account. Those records survive sessions, key revocation, service restarts, and deployments so another headless-granted key on the same account can reopen the same projectId. They remain until the PartMode account is deleted. Account deletion closes every live headless session and removes the durable records; it does not delete unrelated projects in browser storage.

There is no visible studio in this path. cad_artifact, cad_ui, and cad_events are refused, and a successful cad_preview is a typed kernel preview, not a human approval or visible browser preview. The dedicated partmode_headless_export_step tool is the current headless artifact path. Revoking the key immediately prevents further MCP authentication and closes its live headless sessions, but does not delete the account's durable project records. Signing out of PartMode closes active browser relay and headless execution sessions while keeping agent keys and durable headless projects in the account.

Current hosted tools

The current MCP surface advertises exactly 15 tools:

• Session and artifact tools: partmode_list_studios, partmode_connect,

partmode_session_status, partmode_disconnect, partmode_headless_open, and partmode_headless_export_step.

• Typed CAD tools: cad_capabilities, cad_inspect, cad_query,

cad_preview, cad_commit, cad_history, cad_artifact, cad_ui, and cad_events.

Tool listing does not mean every tool is valid for every session. The two headless entry and export tools require the headless grant. cad_artifact generates browser-session artifacts, including drawing-svg, and cad_ui and cad_events also require a browser session. Headless currently exposes STEP through its dedicated export tool. Never invent operation kinds or arguments from static documentation. The live cad_capabilities response wins when Help and a running build differ.

Local pairing

The in-app Connect local agent action is for a compatible loopback integration on the same device. Hosted agents should use the account key and https://partmode.com/mcp instead.

Troubleshooting

• No studio listed: sign in to the same account in PartMode and keep the CAD

tab open, or use a headless-granted edit key for the server path.

• Connection pending: approve or deny the visible browser dialog.
• HEADLESS_NOT_GRANTED: create a new edit key with the headless grant or use

the browser-approved path. Existing keys cannot be upgraded. If PartMode adds a new permission, create a new key to receive it; the persisted ceiling on an existing key remains unchanged.

• VISIBLE_STUDIO_REQUIRED: use a browser session for cad_artifact, cad_ui,

or cad_events.

• HEADLESS_RATE_LIMITED or HEADLESS_CAPACITY_EXCEEDED: wait for the reported

retry window or active work to finish before retrying.

• HEADLESS_PROJECT_QUOTA_EXCEEDED: reopen one of the account's existing 32

project IDs. The current release removes durable headless projects through account deletion, not an individual project-delete tool.

• Revision conflict: inspect again and create a new preview from the current

revision.

• Capability disabled: request only an operation or artifact advertised by

cad_capabilities.

• Session not found: open or connect again. Sessions are temporary even when a

headless project document is durable.

AS4395B Style G demonstration

PartMode includes a configuration-controlled nominal-envelope demonstration for a Style G fitting end. It is intended to show that one part document can drive exact geometry, configuration selection, STEP export, and an associative drawing.

Open and configure it

1. Open Templates.
2. Choose Mechanical and select SAE AS4395B Style G fitting end.
3. Choose Use template. Size 08 is the default configuration.
4. Open CFG to select size 02, 03, 04, 05, 06, 08, 10, 12, 16, 20, 24, 28, 32, 40, or 48.
5. Wait for the exact body and active configuration to settle before exporting.

An agent uses this same template document through a browser-approved session and configuration.activate, after confirming that operation in cad_capabilities. It can then request the active sheet through cad_artifact with the advertised drawing-svg format. The public server-headless path cannot currently import the bundled template or create its configuration table, and it also has no cad_artifact surface. Use the browser path for this demonstration.

Generate the drawing

Open Output and choose Drawing. The exported A3 landscape SVG includes:

• a longitudinal section driven by the same evaluated revolve profile;
• exact OpenCascade HLR front, end, and isometric projections;
• the active configuration's A through W values and tolerances;
• thread, sealing-surface, datum, runout, surface-finish, note, and title-block callouts;
• configuration ID and effective-document evidence.

STEP export uses the same active configuration. Save and reopen of an unchanged configuration must preserve the canonical document, exact B-rep, HLR evidence, and STEP bytes.

Demonstration boundary

• This is Style G only.
• The part is a nominal envelope, not certified standards conformance.
• The thread is represented by a smooth major-diameter envelope and a conventional drawing callout, not helical thread geometry.
• Small specified blend radii are not modeled because the current advanced profile is polyline-only.
• Source values were transcribed from project-owner-supplied excerpts and have not been independently validated against a complete licensed standard.
• Manufacturing use requires the controlled standard, material and process requirements, engineering review, and independent dimensional validation.

Limits, evidence, and safety

PartMode uses OpenCascade through replicad for exact B-rep modeling. It is closer to a parametric mechanical CAD core than a mesh generator, but it is not a replacement for every SolidWorks, CATIA, or drawing-release workflow.

Exact evidence

Treat these as meaningful completion evidence when they apply:

• a settled document and applied kernel revision;
• valid exact B-rep solids with complete face, edge, and vertex identity;
• canonical save and reopen behavior;
• exact OpenCascade HLR evidence for drawing views;
• canonical project output and exact B-rep equivalence for unchanged inputs;
• structured diagnostics when topology or intent cannot be resolved safely.

Screenshots, shaded triangles, DOM rows, schema declarations, and mesh counts alone do not prove exact CAD completion.

Current product limits

• No engineering simulation, certified analysis, or automated design approval.
• No CAM, native DWG authoring, or general GD&T/PMI workbench.
• Imported STEP does not reconstruct vendor-native feature history, mates, or PMI.
• Large assemblies and software-rendered browsers may reduce interactive display quality while preserving exact kernel work.
• Drawing coverage depends on the document recipe and is not automatically complete for manufacturing.
• Standards-oriented templates are demonstrations until independently validated and released under the applicable controlled standard.
• Server-headless execution is bounded to four live sessions and 32 durable

project IDs per account, at most 20 commits and one hour per session, and 120 headless requests per account in a one-minute request window. Global worker capacity can also return a retryable capacity error. Existing project IDs can be reopened without consuming another durable-project slot. There is no separate per-project deletion control yet; account deletion removes all durable headless projects.

• A narrow saved-project compatibility layer preserves selected historical

schema-5 feature intent. Sampled controlled twist and tangent propagation remain compatibility semantics, not newly authorable Professional Core exact features.

• STEP export removes the volatile wall-clock value from the exchange-file

header. Raw byte identity is enforced for the configuration-controlled single-part path; validate multi-body and assembly exchange by exact geometry, names, placements, and hierarchy rather than assuming every OCCT entity number is byte-stable.

Data and privacy

Anonymous CAD, browser project recovery, and browser geometry stay in browser storage. The browser-approved agent path does not turn those local projects into cloud projects. Its approved commands and results pass transiently through the relay over HTTPS, remain in bounded process memory, and are not an end-to-end encrypted project channel.

Server-headless CAD is an explicit exception. An edit key created with the headless grant authorizes PartMode to store committed projects under the account. The stored record includes project ID, project name, revision, full document JSON, canonical document hash, and timestamps. Headless execution sessions are temporary and key-bound, but the committed documents survive session expiry, key revocation, service restarts, and deployments. They remain until account deletion. Deleting the account closes active headless sessions, removes these server records, and does not delete unrelated projects held in browser storage.

Headless sessions have no visible studio. cad_artifact, cad_ui, and cad_events are refused, and typed preview evidence is not a human approval. Their dedicated artifact export currently produces STEP. Choose the browser-approved path whenever a person needs to see and approve each session or preview, or when the agent needs a browser-generated artifact such as drawing-svg.

Download important project files before clearing site data. Keep agent keys in secret storage, grant the smallest permissions needed, and revoke keys that are no longer used.