What causes an Unreal functional test map missing from a cooked build?

Functional tests live in level maps, and those maps are not in the packaging maps list, so the cook omits them and the automation run cannot load them.

How do I catch this when it only happens for some players?

Capture it automatically from the player's device with the full stack trace, the device and OS, the build, and a breadcrumb trail of what they did. That turns a vague complaint into a specific, reproducible issue you can fix without owning the hardware it happens on.

How to Fix an Unreal Functional Test Map Missing After Cook

Quick answer: Add the functional test maps to the additional asset directories or maps to cook, and run automation against a build that includes them.

FFunctionalTest actors live in maps. If those maps are not cooked, the packaged run has nothing to execute. Adding them to the cook list fixes the missing-map failures.

How to fix it

1. Add test maps to the cook

In Project Settings under Packaging, add the test map folder to Additional Asset Directories to Cook or list the maps explicitly so they survive packaging.

2. Run automation against the right target

Invoke with -ExecCmds="Automation RunTests Project.Functional" on a build that includes the maps; running against a cooked client missing them yields load failures, not real results.

3. Keep a test-only build config

Use a separate target or config flag so test maps are cooked in CI runs but excluded from the shipping cook, keeping the shipped package lean.

Catching the ones you can't reproduce

The hardest version of this to fix is the one you can't reproduce — it only happens on a player's hardware, OS, driver, or save state, under conditions that simply aren't present on your machine. A report that says “it crashed” or “it froze” gives you nothing to act on, so the bug survives release after release while quietly costing you players.

Automatic error capture closes that gap. Each failure arrives with its full stack trace, the device and OS, the build number, and a breadcrumb trail of what the player did right before it broke, so even a failure you have never seen becomes a specific, reproducible issue. Fold identical failures into one signature ranked by how many players each hits, and your worklist sorts itself worst-first instead of arriving as a stream of vague complaints.

This is where a tool like Bugnet earns its place. Its SDK captures every Unreal Engine error automatically with the full stack trace plus device, OS, memory, build, and game-state context, folds duplicates into one grouped issue with an occurrence count, and ties each to the build it first appeared on — so you fix the problem that hurts the most players first and confirm it is gone when its signature disappears from the next release.

Reproduce it once with full context and the fix writes itself. The hunt is the expensive part.