What causes invalid argument type errors when calling functions in Godot?

A call passed a value of the wrong type — a String where a NodePath or Callable is expected, an int into a typed-array parameter, or Godot 3 calling conventions used after migrating to Godot 4.

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 “Invalid type in function: Cannot convert argument” in Godot

Quick answer: Read which argument index the error names, convert or construct the expected type explicitly, and update Godot 3-style call sites to their Godot 4 signatures.

The error tells you the function, the argument number, and both types — everything needed. Most hits are migration leftovers and String-vs-specific-type confusion. Here is the decoding routine.

How to fix it

1. Match the exact expected type

Construct what the signature wants: NodePath("Player") not "Player", Callable(self, "on_hit") not a method name string, Vector2i not Vector2 for tile coordinates.

2. Update migrated call sites

Godot 4 changed many signatures (connect, tweens, physics queries). When the error appears in ported code, check the current docs for that method rather than trusting the old call shape.

3. Mind int vs float and Vector2 vs Vector2i

TileMap, texture, and window APIs use integer vectors; passing the float variant raises exactly this.

4. Add types to your own functions

Typed parameters push the failure to the caller with a clear editor-time warning instead of a runtime conversion error deep in engine code.

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 Godot 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.