Why Does a URCap Show as Missing in the Installation Tab?

The Installation tab flags a missing URCap when the installation file was saved against a URCap that no longer loads in the same form. Usually an older version is still referenced, or two versions are installed side by side. Sometimes the URCap failed to install at all. The robot keeps running because the currently installed URCap loads normally. The warning refers to data stored in the installation file, not to the URCap that is running now.

Read the Warning Before You Touch Anything

Everything still works, yet a warning sits in the Installation tab after every restart. Start here: work out which of these conditions matches your panel.

Understand Why the Installation Still Runs

A URCap is a packaged plugin bundle. When PolyScope starts, it loads every bundle in its URCap store, and each bundle registers its installation nodes, program nodes, and toolbar contributions.

The .installation file stores configuration data for every URCap contribution it contained at save time. That data is tied to the URCap that created it. When you load the file, PolyScope matches each stored contribution against the bundles running right now.

• If the matching bundle is present, the data loads into its node.
• If the stored data belongs to a URCap identity or version that is not running, PolyScope has nowhere to put it and raises the missing-URCap warning.
• The current URCap still registers its own fresh node, so the features work. You end up with a working node and an orphaned reference at the same time.

Two installed versions of one URCap produce the same symptom. The installation may have been saved against the old version, and whichever version loads, the other side of the reference is missing.

That is not a fault in your URCap code. It is a stale reference in the saved file.

Clear the Stale Reference

Do these steps in order. The first one fixes most cases.

1. Open the hamburger menu in the top-right corner of PolyScope and go to the URCaps list under the system settings.
2. Check every entry. Look for two versions of the same URCap and for any entry flagged as failed or not started.
3. Before removing anything, open the affected installation and write down the configuration values in the URCap's installation node. Re-saving can drop settings tied to the old version.
4. Remove the old or duplicate URCap version. Keep only the version you intend to run.
5. Restart PolyScope when prompted. The URCap store is only reloaded on restart.
6. Load the affected installation file.
7. Open the URCap's installation node and re-enter any values that did not carry over.
8. Save the installation. Use the same file name to overwrite it, or save under a new name and set it as the default installation that loads at boot.
9. Open every program that uses the URCap's program nodes. Check that the nodes are defined, then save each program so it references the current version.
10. Restart once more and confirm the warning is gone.

Fix an Invalid Manifest Install

If the URCaps list shows the URCap as failed, or the install threw an invalid manifest error, re-saving the installation will not help. The bundle itself is not loading.

Remote deployment is the usual trigger. Pushing a URCap to the robot over the network can leave an old copy in place or deliver an incomplete file. The same bundle installed from a USB flash drive often installs clean.

1. Delete the URCap from the robot in the URCaps list.
2. Restart PolyScope so the old bundle is fully unloaded.
3. Copy the .urcap file to a USB flash drive.
4. Install the URCap from the flash drive using the + button in the URCaps list.
5. Restart and check that the entry shows as installed and active.
6. Then run the stale-reference procedure above if the Installation tab warning is still present.

If the error returns with a USB install on a freshly deleted robot, the manifest in the bundle is wrong. Check it at build time. The symbolic name and version fields in the bundle manifest must be consistent between builds. A renamed bundle orphans every installation saved with the old name.

Verify the Fix

• The URCaps list shows exactly one entry for the URCap, marked active.
• After a full restart, the default installation loads with no warning in the Installation tab.
• The URCap's installation node shows the configuration values you recorded.
• Every program using URCap nodes loads without undefined nodes and runs through one cycle.
• Any other installation files on the robot also load clean. Each file saved before the update needs its own re-save.

Avoid the Repeat Offenders

• Installing over the top. Installing a new version without removing the old one is how duplicates happen. Remove, restart, install.
• Forgetting to save. Loading the installation clears nothing until you save it. The warning comes back on every boot until you save.
• Wrong default installation. You fixed one file, but the robot boots a different one. Confirm which installation loads at startup.
• Re-pushing remotely after a manifest error. Repeated network pushes waste time. Delete and install from USB.
• Changing bundle identity during development. Renaming the URCap or changing its symbolic name between builds orphans every saved installation. Only bump the version.
• Losing settings. Re-saving can discard data stored for the missing URCap. Record values first.
• Chasing the URCap code. If the features work and only the warning shows, do not debug your contribution logic. Fix the saved file.

FAQ