Lens studio preview verify

Previewing & verifying Lens Studio work

You're editing blind unless you reset, screenshot, and check compiles. Here's the loop.

There is no Save tool — and edits need a reset to take effect

• Ctrl+S is GUI-only; no MCP tool saves the project. Tell the user to press it to persist scene edits. A project reload wipes unsaved scene edits, so save before anything that reloads.
• MCP scene edits (new objects, property changes, new scripts) only reach the running preview after a reset. The reset tool keeps editor objects and re-runs scripts; a full reload is the one that wipes unsaved work.

Reset the preview with RunAndCollectLogsTool — with TINY params

RunAndCollectLogsTool resets the preview (re-runs onAwake/onStart, applies your edits) and then collects logs. On a real project the log collection hangs and the tool times out — but the reset still happened. Avoid the timeout by asking for almost nothing:

RunAndCollectLogsTool maxRuntimeMs:800 maxLines:3

A good result contains "msg": "Lens has been reset". That's your signal the edits are live. If it still times out, the reset usually occurred anyway — proceed to screenshot.

Runtime logs are often unreadable — don't depend on print

GetLensStudioLogsTool for the preview category frequently times out too, because a single broken import (e.g. a duplicated SpectaclesUIKit 2.lspkg) floods the log. Consequences:

• Don't rely on reading your own print() output to confirm runtime behaviour. Verify visually (screenshot) and structurally (read the property/scene back).
• For navigation/state logic you can't see in a still frame, add a debugAutoTour/startScreen knob to the controller and screenshot each state (see sik-interactivity).

Checking that TypeScript compiled

• CompileWithLogsTool also times out when a bad import floods logs — don't lean on it. Worse, it frequently reports a timeout even though the TypeScript compile actually SUCCEEDED. A timeout error from it is not a compile failure — don't act on it.
• Verify the compile from the logs, not the tool's exit. Read just the tsc category, tiny window: GetLensStudioLogsTool categories:["tsc"] maxLines:25 timeWindowMs:15000.
  • "TypeScript compilation succeeded!" in tsc = it compiled (trust this over the tool timeout).
  • An empty tsc result = no TypeScript errors either. Errors show up here as text.
• If a new script's @inputs never appear on its component, it didn't compile — check tsc.

Screenshotting the preview

The Lens Studio window won't come to the foreground; capture it occluded. A helper script grabs the window to a PNG:

pwsh -File <skills>/lens-studio-mcp/scripts/capture-preview.ps1 -Out D:\tmp\shot.png

Then crop/zoom the region you care about (the Preview panel, usually the right third) with a tiny System.Drawing script and Read the cropped PNG. Tips:

• Capture → read the pixels → decide next edit. Re-screenshot after every meaningful change; never assume an edit looks right.
• The preview camera reframes when scene content changes (disabling a big object, the stage auto-fitting). Re-locate your UI each time rather than trusting fixed crop coords.
• If another subsystem (e.g. a 3D stage) renders over your UI, temporarily disable it for a clean UI shot, then re-enable it. Restore what you toggled.

The verification loop, in order

1. Make edits (component-by-component for vectors).
2. Read back anything whose echo was {} (vectors, references) to confirm it took.
3. RunAndCollectLogsTool maxRuntimeMs:800 → expect "Lens has been reset".
4. GetLensStudioLogsTool categories:["tsc"] → expect empty (compiled).
5. capture-preview → crop → Read → judge → iterate.
6. When it looks right, remind the user to Ctrl+S.

Environment notes

• LS 5.x projects are .esproj. For LS 5.15.4 use SIK ≤ 0.17.3 / UI Kit ≤ 0.1.6.
• Package installs frequently duplicate folders (... 2.lspkg); a duplicate with a broken import is the usual cause of the log/compile floods above. Removing the stray duplicate restores normal logs.
• GenerateFast3DAssets / GenerateTexture / GenerateFaceMaskTexture often time out — don't put them on the critical path.
• The MCP port changes each LS restart; re-point the server when every call suddenly fails.