OneCAD-Simulation/docs/privacy.md

Privacy and anonymous usage

FieldCraft can share anonymous usage with its developers: which tools are used, where people get stuck and how far they get from a design to results. It is off until you agree. The first time the app starts it asks once:

Help improve FieldCraft by sharing anonymous usage: which tools you use, nothing from your models.

Share Anonymous Usage turns it on, Don't Share (or closing the question) leaves it off. Change it any time in Help › Settings… › Privacy, which also has Include scripts and AI agents (MCP): commands run by scripts, the control channel and AI agents are counted apart from yours (from), and this leaves them out.

Crash reports and the log never leave your computer on their own; Help › Report a Bug sends only what you submit yourself (crash-reports.md).

Never sent

File names or paths, geometry, meshes, model contents, parameter values (sizes, materials, loads…), names you give things, error messages, or anything else you typed. The events below are built from FieldCraft's own lists (its command ids, sample names and requirement names) and durations, so they cannot carry any of it; a test runs a scripted session and fails if a payload holds anything else.

When nothing is sent

• until you agree, and after you turn it off (what was waiting is dropped);
• in builds without an analytics key: everything built from source, development and fork builds. Only the release builds have one;
• with FIELDCRAFT_TELEMETRY=0 (or false, off, no) in the environment;
• in runs driven by automation (--control) and in CI (CI set), unless FIELDCRAFT_TELEMETRY=1 asks for it;
• fieldcraft-cli and the MCP server never send anything themselves; the app counts the commands they send it.

Where it goes

PostHog Cloud, EU region (https://eu.i.posthog.com), a batch of events every 30 seconds and when the window closes, on a background thread (the web build uses fetch). A batch that cannot be sent (offline, a slow network) is dropped; at most 1000 events wait. Each event goes with $process_person_profile: false (no person profile is built) and $geoip_disable: true (no location is derived from the connection's IP address). FIELDCRAFT_TELEMETRY_HOST sends to another host instead (to check what is sent against a local listener).

What is sent

Every event has these properties:

Property	Value
distinct_id	a random id made for this install when you agree (a UUID), kept in the preferences; nothing about the computer or you
app_version	FieldCraft's version, 0.5.8
platform	desktop or web
os	macos, linux, windows, or web
arch	aarch64, x86_64, or wasm32
$process_person_profile	false
$geoip_disable	true

The events:

Event	Properties	When
app_started	—	the app starts with sharing on, or you turn it on
app_closed	duration_s: seconds since app_started	the window closes (the page is closed or left)
command_run	command: the command's id (mesh.tet.generate); kind: model or session; duration_ms; ok: whether it succeeded; error (when it failed): the class of the error, one of unknown_command, params, model, geometry, mesh, file, deck, solver, explicit, fluid, unavailable, internal; from: ui (a click, a form, a menu), palette (the command search or command line), script (a script or the control channel) or mcp (an AI agent)	a command ends; a command run by another (a script's steps inside it) is not counted on its own
milestone	name: design_opened (a design, mesh or model opened), meshed (a mesher made elements), solved (a solve finished), results_viewed (results shown)	the first time in a run
sample_opened	name: the sample's name (cantilever)	a sample opens
form_cancelled	command: the form's command id	a command's form closes without running it
unavailable_clicked	command: the command id; missing: what the model lacks, by requirement name (material, step, …)	a command is clicked before the model has what it needs

A command_run as sent:

{"event": "command_run", "distinct_id": "5f0c…-…", "properties": {"command": "solve.run", "kind": "model", "duration_ms": 412, "ok": true, "from": "ui", "app_version": "0.5.8", "platform": "desktop", "os": "macos", "arch": "aarch64", "$process_person_profile": false, "$geoip_disable": true}}

For developers

The events and the policy are fieldcraft_engine::usage; the consent question and the settings are crates/ui-egui/src/privacy.rs; the desktop sender is apps/fieldcraft/src/usage.rs, the web one apps/fieldcraft-web/src/usage.rs. The PostHog project key is the build-time variable FIELDCRAFT_POSTHOG_KEY, which the release workflow and the Pages build of main set from the repository secret POSTHOG_KEY; it is an ingest-only key. A new event or property is added here first.