Blog · Inventor · 1 Oct 2026 · 4 min read

Inventor API errors and what they really mean: err 5, 429, 0x80080005, Unspecified error

Inventor's COM errors rarely name the real cause, and some calls succeed while doing nothing. A reference of the errors and silent failures we met automating Inventor 2025 from scripts, with the cause and the fix for each.

Inventor's API errors are short and rarely point at the real problem. Worse, some calls return success and do nothing. This is the reference we wish we had: every error and silent failure we met while an AI agent drove Inventor 2025 from scripts, with the cause and the fix.

Connection errors

Error	Where	Cause	Fix
`0x80080005 CO_E_SERVER_EXEC_FAILURE`	`CreateObject("Inventor.Application")`	Inventor is already open; this tries to start a second one	`GetObject(, "Inventor.Application")`
`429`	`CreateObject`	Inventor is closed	Open Inventor, then `GetObject`
`0x80131165 Type library is not registered`	`GetActiveObject` from PowerShell	PowerShell route does not work	Run a `.vbs` with `cscript`
`FileNotFoundException`	Compiled C# at run time	Interop DLL not next to the `.exe`	Copy `Autodesk.Inventor.Interop.dll` beside it

Full setup: how to drive Inventor from the terminal without an MCP server.

Calls that fail from VBScript

Error	Call	Cause	Fix
`Invalid procedure call or argument` (err 5)	iLogic `AddRule`, `RunExternalRule`	From outside the process, calls taking a `Document` fail	Run the rule from inside: iLogic bridge
`Type mismatch` (13)	`SurfaceEvaluator.GetNormal`, `Evaluator2D.GetParamExtents`	They return arrays by reference	Compiled C#
does not work	`Matrix.AsArray()`	Same limit	Compiled C#
`err 500`, always	`CallByName` on Inventor objects	Not supported on these COM objects	Call the property directly
fails on the second loop	`Dim` inside `For Each`	VBScript limit	Declare variables before the loop
overflow	`CInt`	Limit of 32767	`CLng`

Calls that fail in the drawing

Error	Call	Cause	Fix
`Invalid procedure call or argument`	DXF `SaveCopyAs`	No translator ini file	Write the ini first: DXF and PDF export
`Unspecified error`	export, after a few files	Orphan models left open by earlier drawings	Close everything the script opened
`Unspecified error`, file rolled back	`Document.Save`	Several Inventor processes running	One Inventor only; back up before saving
err 5	`Transform` on an occurrence	Matrix built from printed values: determinant `1.00000015`	Copy `occ.Transformation` instead of rebuilding it
err 13	`Add(collection)` when inserting bodies	Wrong overload	`AddByDefinition`
`Style Conflict` dialog	editing a template	Template styles differ from the library	Copy the style (`TextStyle.Copy`) and change the copy

Calls that succeed and do nothing

These are the dangerous ones. No error, wrong result.

Call	What happens	What to do
`AddTitleBlock(..., PromptStrings)`	Returns OK, fills no field	Put the values in the part's iProperties, use property fields in the title block, then `Update()`
PDF `SaveCopyAs` with context `13075`	No file, no error	Context `13059`
`Unfold()` on a STEP solid	"Succeeds" on parts that are not bent plates	Check the result before trusting it
Flat view with `SheetMetalFoldedModel = False`	With no flat pattern, Inventor quietly draws the folded part	Check the part has a flat pattern first
`DrawingView.Camera` + `ApplyWithoutTransition`	Base view turns, projected views stay rotated: wrong but plausible dimensions	Create the three base views, measure them, keep the one with the largest area
`SurfaceBodies.Item("Solid8")`	Does not look up by name	Loop and compare `Name`
`SurfaceBody.Delete`	Does not delete a body imported from STEP	Copy the bodies you want into a new part instead
`DrawingCurve.Visible`	Always reports zero for hidden lines	Hidden state is on the curve segments
`Close` after a hung `Documents.Add`	Returns 0, closes nothing	Restart Inventor
a silent `Catch` in your own code	Hides the real error	Log every exception

Units: the error with no message

The API works in centimetres. Not the document units, not the sheet scale.

ModelValue of a dimension is in cm and is the size of the part. In a 2:1 view, a 40 mm line on paper returns 2.0.
An edge radius from ModelGeometry.Geometry.Radius is in model cm: diameter in mm is Radius * 20, with no view scale.
DrawingDimension.Precision changes the shown decimals only. ModelValue does not change.
On a dimension, precision is an integer (number of decimals). On a dimension style, LinearPrecision wants an enum. Pass the enum to the dimension and you get no error and zero decimals: 87.5 becomes 88.
A thickness of 10,0 with a decimal comma read from a CSV became 1000. It happened on 101 drawings out of 130.

Text and encoding

Symptom	Cause	Fix
Dimension text doubles up	`<<>>` appends text	Use the `<DimensionValue/>` token in `FormattedText`
Value still shows after editing text	Value not hidden	`HideValue = True` first
Line break shows as text	`\P` or `vbLf`	`<Br/>`
CSV read as garbage in VBScript	`OpenTextFile` format `-1` is UTF-16, not UTF-8	Read the file as ANSI
Rule file corrupted	`sed -i` broke UTF-8	Edit with a tool that keeps the encoding
File left at zero bytes	`UnicodeEncodeError` halfway through a write	Write to a temporary file, then rename
Python crashes on `Ø`	Console encoding	`PYTHONIOENCODING=utf-8`

The rule behind all of this

No result counts until it has been checked in the file. A run that ends without errors has proved only that it ended. Read the values back, count the entities, render the drawing and look at it.

Questions people ask

Where are the enum values documented? In the Interop DLL. Read them by reflection rather than writing them from memory: values we wrote from memory were wrong.

Which Inventor version is this? Inventor 2025. Other versions may behave differently; test before relying on any row of these tables.