[Qgis-user] GRASS Tools give error message using the GRASS GIS Processing Provider

[Jochem Kail]

Dear all,

I can run GRASS tools using the GRASS 8 (deprecated plugin) using data 
stored in a GRASS mapset (e.g. v.buffer). So GRASS seems to be correctly 
installed and linked to QGIS.

However, I get an error message when using the same GRASS data or 
shaepfile data using the same GRASS tool from the processing toolbar, 
available after ticking the GRASS GIS Processing Provider in Plugins - 
Manage and Install Plugins. For more details on the log information 
trying to run v.buffer on a shapefile see the text below.

I am using QGIS 3.40.15 with GRASS 8.4 installed using the OSGeo4W 
installer.

Any help is highly welcome

Jochem

QGIS version: 3.40.15-Bratislava

QGIS code revision: f68f1bf573

Qt version: 5.15.13

Python version: 3.12.12

GDAL version: 3.12.1

GEOS version: 3.14.1-CAPI-1.20.5

PROJ version: Rel. 9.7.1, December 1st, 2025

PDAL version: 2.9.3 (git-version: 31d0d2)

GRASS version: 8.4.2

Algorithm started at: 2026-02-17T11:29:43

Algorithm 'v.buffer' starting…

Input parameters:

{ '-c' : False, '-s' : False, '-t' : False, 'GRASS_MIN_AREA_PARAMETER' : 
0.0001, 'GRASS_OUTPUT_TYPE_PARAMETER' : 0, 'GRASS_REGION_PARAMETER' : 
None, 'GRASS_SNAP_TOLERANCE_PARAMETER' : -1, 'GRASS_VECTOR_DSCO' : '', 
'GRASS_VECTOR_EXPORT_NOCAT' : False, 'GRASS_VECTOR_LCO' : '', 'angle' : 
1, 'cats' : '', 'column' : '', 'distance' : 100, 'input' : 
'D:/A_Uni_DUE/GISQGISTest/Z_TestDataJK/Probestellen_GIS_aktuell_UTM32.shp', 
'layer' : '-1', 'minordistance' : 100, 'output' : 
'D:/A_Uni_DUE/GISQGISTest/Z_TestDataJK/ZBufferTestGRASSProcessingProvider.shp', 
'scale' : 1, 'tolerance' : 0.01, 'type' : [0], 'where' : '' }


Attempting to use v.external for direct layer read

g.proj -c wkt="C:/Users/Jochem 
Kail/AppData/Local/Temp/processing_AztPDF/57ecaacfeef04441827b0e03e1a7b55b/crs.prj"

v.external 
input="D:\A_Uni_DUE\GISQGISTest\Z_TestDataJK\Probestellen_GIS_aktuell_UTM32.shp" 
output="vector_69944317348ff3" --overwrite -o

g.region n=5737750.405692774 s=5716318.80064247 e=407087.804598595 
w=351579.33806329395

v.buffer input=vector_69944317348ff3 type="point" distance=100 
minordistance=100 angle=1 layer="-1" scale=1 tolerance=0.01 
output=output203a53f6aacb430c88385ee70ad52a1e --overwrite

v.out.ogr type="auto" input="output203a53f6aacb430c88385ee70ad52a1e" 
output="D:\A_Uni_DUE\GISQGISTest\Z_TestDataJK\ZBufferTestGRASSProcessingProvider.shp" 
format="ESRI_Shapefile" --overwrite

WARNUNG: Sperren gleichzeitiger Zugriffe auf ein Mapset ist unter 
Windows nicht möglich.

C:\Users\Jochem Kail\Documents>chcp 1252 1>NUL

C:\Users\Jochem Kail\Documents>g.proj -c wkt="C:/Users/Jochem 
Kail/AppData/Local/Temp/processing_AztPDF/57ecaacfeef04441827b0e03e1a7b55b/crs.prj"

Die Standard Region wurde auf die neue Projektion aktualisiert. Wenn Sie 
aber mehrere Mapsets haben, sollten Sie `g.region -d` in jedem 
ausführen, um die Einstellungen von der Standardregion zu übernehmen.

Projektionsinformationen aktualisiert

C:\Users\Jochem Kail\Documents>v.external 
input="D:\A_Uni_DUE\GISQGISTest\Z_TestDataJK\Probestellen_GIS_aktuell_UTM32.shp" 
output="vector_69944317348ff3" --overwrite -o

C:\Users\Jochem Kail\Documents>g.region n=5737750.405692774 
s=5716318.80064247 e=407087.804598595 w=351579.33806329395

C:\Users\Jochem Kail\Documents>v.buffer input=vector_69944317348ff3 
type="point" distance=100 minordistance=100 angle=1 layer="-1" scale=1 
tolerance=0.01 output=output203a53f6aacb430c88385ee70ad52a1e --overwrite

FEHLER: Vektorkarte <vector_69944317348ff3> nicht gefunden.

C:\Users\Jochem Kail\Documents>v.out.ogr type="auto" 
input="output203a53f6aacb430c88385ee70ad52a1e" 
output="D:\A_Uni_DUE\GISQGISTest\Z_TestDataJK\ZBufferTestGRASSProcessingProvider.shp" 
format="ESRI_Shapefile" --overwrite

C:\Users\Jochem Kail\Documents>exit

Execution completed in 7.57 seconds

Results:

   output: 
D:\A_Uni_DUE\GISQGISTest\Z_TestDataJK\ZBufferTestGRASSProcessingProvider.shp


Loading resulting layers

The following layers were not correctly generated.
• 
D:/A_Uni_DUE/GISQGISTest/Z_TestDataJK/ZBufferTestGRASSProcessingProvider.shp
You can check the 'Log Messages Panel' in QGIS main window to find more 
information about the execution of the algorithm.

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