# Engineering Versions

Keep offline project checkpoints and compare alternatives without turning history into authority.

## What Versions stores

Engineering Versions is local project history. It is available without an AI subscription or network connection; managed AI usage and billing are separate. Saved revisions are immutable snapshots of project inputs. A revision is not a simulation result, safety approval or proof that it is still the current project.

## Save a milestone or alternative

Select Project versions (the stacked-page icon) in the assistant header, even when AI is off. This opens local project history without starting a conversation. Choose New… to save a named Milestone for a point you intend to keep, or an Alternative for a separate direction. Check the displayed project head before creating it. The label helps you find the snapshot; it does not alter its content or authorize Apply. Automatic checkpoints remain identified as automatic rather than being presented as named milestones.

## Compare before choosing

Choose two saved revisions and open Compare. Workcell identifies their common base when available and reports file changes separately from supported engineering-property values, text and opaque binary assets. It shows recorded values without inferring missing units; unknown or unsupported content stays opaque rather than being guessed or silently normalized. Resolve conflicts explicitly before preparing a merge proposal.

## Prepare, inspect and restore

For a selective merge, review each proposed path and its source side, then choose Prepare merge. This creates a new immutable proposal; it does not edit the canonical project. To return to an older revision, choose Prepare restore. The existing review flow shows the exact candidate and requires a separate explicit Apply. Later versions remain in history.

## Export and import safely

Use Export on a selected revision to create a portable history archive, then keep it with your project backup. Import reads a chosen archive as an untrusted proposal: it validates the archive and does not extract files into the open project. Inspect the imported revision before comparing or preparing a merge. If the archive is rejected or storage is full, keep the original project and retry only after checking the specific error; never bypass path, hash or size checks.

## Unsaved edits and active work

Save native project edits before creating a checkpoint, merge proposal or import. Read-only listing, comparison and export do not change project files. If a conversation or project is busy, wait for its exact run to finish before requesting a new proposal. Switching Versions views does not switch projects or restore an old chat, draft, approval or transaction authority.

## Expected result and recovery

A completed operation identifies its exact revision and source head. If Workcell reports a stale head, changed project, incomplete history or unavailable storage, stop and refresh the Versions view. Do not repeat a write after an uncertain acknowledgement until you reconcile the returned operation identity. For app-level problems, see [Troubleshooting](/docs/troubleshooting/) and include only a redacted error in a [private support request](/support/).

![Installed Engineering Versions, with AI off](/assets/engineering-versions-installed.png)

Actual installed Workcell on Linux ARM64, with AI switched off. A named QA milestone is selected; partial completeness and excluded inputs stay visible. This is history UI evidence, not a robot simulation result.