blender-errors-version

name	blender-errors-version
description	Use when debugging Blender AttributeError from removed APIs, ImportError from deprecated modules (bgl in 5.0), or breaking changes in operator signatures between versions. Prevents silent failures from using APIs that were renamed or removed in newer Blender versions. Provides migration patterns from 3.x to 4.x to 5.x with complete replacement mappings. Keywords: AttributeError, ImportError, deprecated, version error, bgl, migration, breaking change, removed API, 3.x to 4.x, 4.x to 5.x, Blender upgrade, module has no attribute, addon not compatible.
license	MIT
compatibility	Designed for Claude Code. Requires Python 3.x.
metadata	{"author":"OpenAEC-Foundation","version":"1.0"}

Blender Errors: Version Compatibility

Diagnose and resolve Python API errors caused by Blender version differences. This skill activates when encountering AttributeError, ImportError, TypeError, KeyError, or RuntimeError in Blender scripts that result from using removed, renamed, or restructured APIs.

Dependency: blender-core-versions — version matrix and detection API.

---

1. Error Diagnosis Decision Tree

When a Blender Python script raises an error, follow this decision tree:

ERROR RECEIVED
│
├── AttributeError?
│   ├── "has no attribute 'bevel_weight'" → Blender 4.0+ mesh attribute migration [E-01]
│   ├── "has no attribute 'crease'" → Blender 4.0+ mesh attribute migration [E-01]
│   ├── "has no attribute 'use_auto_smooth'" → Blender 4.1+ auto-smooth removal [E-02]
│   ├── "has no attribute 'auto_smooth_angle'" → Blender 4.1+ auto-smooth removal [E-02]
│   ├── "has no attribute 'face_maps'" → Blender 4.0+ face maps removal [E-03]
│   ├── "has no attribute 'layers'" (on Bone) → Blender 4.0+ bone collections [E-04]
│   ├── "has no attribute 'bone_groups'" → Blender 4.0+ bone collections [E-04]
│   ├── "has no attribute 'inputs'" (on NodeTree) → Blender 4.0+ interface API [E-05]
│   ├── "has no attribute 'outputs'" (on NodeTree) → Blender 4.0+ interface API [E-05]
│   ├── "has no attribute 'sculpt_tool'" → Blender 5.0+ brush rename [E-06]
│   ├── "has no attribute 'node_tree'" (on Scene) → Blender 5.0+ compositor [E-07]
│   ├── "has no attribute 'use_nodes'" (on Scene) → Blender 5.0+ compositor [E-07]
│   ├── "has no attribute 'end_frame'" (on Strip) → Blender 5.0+ VSE [E-08]
│   ├── "has no attribute 'fcurves'" (on Action) → Blender 5.0+ slotted actions [E-09]
│   ├── "has no attribute 'displacement_method'" (on CyclesMaterial) → Blender 4.1+ [E-10]
│   ├── "has no attribute 'active_color_name'" → Blender 4.3+ AttributeGroup split [E-11]
│   ├── "has no attribute 'use_ssr'" → Blender 4.3+ EEVEE property removal [E-12]
│   ├── "has no attribute 'use_bloom'" → Blender 4.3+ EEVEE property removal [E-12]
│   └── "has no attribute 'calc_normals'" → Blender 4.0+ auto normals [E-13]
│
├── ImportError / ModuleNotFoundError?
│   ├── "No module named 'bgl'" → Blender 5.0+ BGL removal [E-14]
│   ├── "No module named 'io_scene_obj'" → Blender 4.0+ C++ IO [E-15]
│   └── "No module named 'io_mesh_ply'" → Blender 4.0+ C++ IO [E-15]
│
├── TypeError?
│   ├── On bpy.ops call with dict first arg → Blender 4.0+ context override [E-16]
│   ├── "foreach_set() invalid data type" → Blender 4.1+ validation [E-17]
│   ├── On IDProperty type mismatch → Blender 4.2+ static typing [E-18]
│   └── On __init__() argument mismatch → Blender 4.4+ super() required [E-19]
│
├── KeyError?
│   ├── "Subsurface" (on Principled BSDF) → Blender 4.0+ socket renames [E-20]
│   ├── "Specular" (on Principled BSDF) → Blender 4.0+ socket renames [E-20]
│   ├── "cycles" (on scene[]) → Blender 5.0+ dict access removal [E-21]
│   └── Node socket name not found → Version-dependent socket names [E-20]
│
├── RuntimeError?
│   ├── "Embedded ID assignment" → Blender 4.3+ PointerProperty [E-22]
│   └── "BLENDER_EEVEE" engine not found → EEVEE identifier change [E-23]
│
└── ValueError?
    ├── "'CUBEMAP' not in enum" → Blender 4.1+ light probe renames [E-24]
    ├── "'PLANAR' not in enum" → Blender 4.1+ light probe renames [E-24]
    ├── "'3D_UNIFORM_COLOR' not found" → Blender 4.0+ shader renames [E-25]
    └── "'BLENDER_EEVEE_NEXT' not in enum" → Blender 5.0+ EEVEE revert [E-23]

---

2. Error Patterns: Quick Resolution Table

Blender 4.0 Breaking Errors

Error Code	Error Message Pattern	Removed API	Replacement	Since
E-01	AttributeError: 'MeshEdge' has no attribute 'bevel_weight'	mesh.edges[i].bevel_weight	mesh.attributes.get("bevel_weight_edge")	4.0
E-01	AttributeError: 'MeshEdge' has no attribute 'crease'	mesh.edges[i].crease	mesh.attributes.get("crease_edge")	4.0
E-03	AttributeError: 'Object' has no attribute 'face_maps'	obj.face_maps	Integer face attributes	4.0
E-04	AttributeError: 'Bone' has no attribute 'layers'	bone.layers[i]	bone.collections	4.0
E-04	AttributeError: 'Pose' has no attribute 'bone_groups'	pose.bone_groups	Bone collections + colors	4.0
E-05	AttributeError: 'NodeTree' has no attribute 'inputs'	NodeTree.inputs.new()	NodeTree.interface.new_socket()	4.0
E-13	AttributeError: 'Mesh' has no attribute 'calc_normals'	mesh.calc_normals()	Removed (auto-calculated)	4.0
E-15	ModuleNotFoundError: No module named 'io_scene_obj'	Python OBJ/PLY IO	bpy.ops.wm.obj_import/export	4.0
E-16	TypeError: bpy.ops expects keyword arguments	Dict context override	context.temp_override()	4.0
E-20	KeyError: 'Subsurface' on Principled BSDF	Old socket names	Subsurface Weight, etc.	4.0
E-25

Blender 4.1 Breaking Errors

Error Code	Error Message Pattern	Removed API	Replacement	Since
E-02	AttributeError: 'Mesh' has no attribute 'use_auto_smooth'	mesh.use_auto_smooth	mesh.corner_normals + Smooth by Angle modifier	4.1
E-02	AttributeError: 'Mesh' has no attribute 'auto_smooth_angle'	mesh.auto_smooth_angle	Smooth by Angle modifier	4.1
E-10	AttributeError: 'CyclesMaterialSettings' has no attribute 'displacement_method'	mat.cycles.displacement_method	mat.displacement_method	4.1
E-17	TypeError: foreach_set() invalid data type	Silent failure on bad types	Add type validation	4.1
E-24	ValueError: 'CUBEMAP' not in enum	CUBEMAP/PLANAR/GRID	SPHERE/PLANE/VOLUME	4.1

Blender 4.2 Breaking Errors

Error Code	Error Message Pattern	Removed API	Replacement	Since
E-18	TypeError: IDProperty type mismatch	Dynamic IDProperty types	Static typing enforced	4.2
E-23	RuntimeError: 'BLENDER_EEVEE' not found (in 4.2-4.x)	BLENDER_EEVEE	BLENDER_EEVEE_NEXT	4.2

Blender 4.3 Breaking Errors

Error Code	Error Message Pattern	Removed API	Replacement	Since
E-11	AttributeError: 'AttributeGroup*' has no attribute 'active_color_name'	Generic AttributeGroup	AttributeGroupMesh (type-specific)	4.3
E-12	AttributeError: 'EEVEE' has no attribute 'use_ssr'	40+ EEVEE legacy props	Properties removed (engine-internal)	4.3
E-22	RuntimeError: Embedded ID assignment	Embedded ID to PointerProperty	Do not assign embedded IDs	4.3

Blender 4.4 Breaking Errors

Error Code	Error Message Pattern	Removed API	Replacement	Since
E-19	TypeError: __init__() argument mismatch	No super().__init__()	super().__init__(*args, **kwargs)	4.4

Blender 5.0 Breaking Errors

Error Code	Error Message Pattern	Removed API	Replacement	Since
E-14	ModuleNotFoundError: No module named 'bgl'	import bgl	import gpu + gpu.state.*	5.0
E-06	AttributeError: 'Brush' has no attribute 'sculpt_tool'	brush.sculpt_tool	brush.sculpt_brush_type	5.0
E-07	AttributeError: 'Scene' has no attribute 'node_tree'	scene.node_tree (compositor)	scene.compositing_node_group	5.0
E-08	AttributeError: 'Strip' has no attribute 'end_frame'	strip.end_frame	strip.length	5.0
E-09	AttributeError: 'Action' has no attribute 'fcurves'	action.fcurves (legacy)	Slotted Actions channelbag API	5.0
E-21	KeyError: 'cycles' on scene['cycles']	Dict access to RNA props	scene.cycles.samples (attribute)	5.0

---

3. Deprecation Timeline

ALWAYS check this timeline before using any API. If the current Blender version is past the removal date, the API WILL raise an error.

API	Deprecated	Removed	Warning Period
Context override dicts	3.2	4.0	3.2 → 3.6 (4 releases)
mesh.calc_normals()	3.4	4.0	3.4 → 3.6 (2 releases)
MeshEdge.bevel_weight / .crease	3.4	4.0	3.4 → 3.6 (2 releases)
NodeTree.inputs/outputs	3.4	4.0	3.4 → 3.6 (2 releases)
3D_UNIFORM_COLOR shader	3.4	4.0	3.4 → 3.6 (2 releases)
bgl module	3.5	5.0	3.5 → 4.x (long, 9+ releases)
mesh.use_auto_smooth	4.0	4.1	4.0 only (1 release)
Light probe CUBEMAP/PLANAR/GRID	4.0	4.1	4.0 only (1 release)
bl_info dict (for extensions)	4.2	Ongoing	Still works as legacy addon
BLENDER_EEVEE identifier	4.2	4.2 (temp)	Renamed to _NEXT, reverted in 5.0
EEVEE legacy properties (40+)	4.2	4.3	4.2 only (1 release)
bpy.types.AttributeGroup (generic)	4.2	4.3	4.2 only (1 release)
bpy.types.Sequence (VSE)	4.3	4.4	4.3 only (1 release)
action.fcurves (legacy)	4.4	5.0	4.4 → 4.5 (2 releases)
/

---

4. Diagnostic Patterns

Pattern 1: Identify Version from Error

When a user reports an error without specifying their Blender version, ALWAYS determine the version first:

# Blender 3.x / 4.x / 5.x: Print diagnostic info
import bpy
print(f"Blender: {bpy.app.version}")
print(f"Python: {bpy.app.version_string}")
print(f"Cycle: {bpy.app.version_cycle}")

Pattern 2: Version-Safe Error Recovery

ALWAYS use hasattr() for graceful degradation. NEVER catch AttributeError silently.

# Blender 3.x / 4.x / 5.x: Version-safe accessor with explicit fallback
import bpy

def get_bevel_weight(mesh, edge_index):
    """Get edge bevel weight with version-safe fallback."""
    if bpy.app.version >= (4, 0, 0):
        attr = mesh.attributes.get("bevel_weight_edge")
        if attr:
            return attr.data[edge_index].value
        return 0.0
    else:
        return mesh.edges[edge_index].bevel_weight

Pattern 3: Multi-Version Compatibility Wrapper

For addons targeting multiple Blender versions, use a compatibility module:

# Blender 3.x / 4.x / 5.x: compat.py module pattern
import bpy

BLENDER_4 = bpy.app.version >= (4, 0, 0)
BLENDER_41 = bpy.app.version >= (4, 1, 0)
BLENDER_42 = bpy.app.version >= (4, 2, 0)
BLENDER_43 = bpy.app.version >= (4, 3, 0)
BLENDER_44 = bpy.app.version >= (4, 4, 0)
BLENDER_5 = bpy.app.version >= (5, 0, 0)
BLENDER_51 = bpy.app.version >= (5, 1, 0)

---

5. Critical Rules

1. NEVER suppress DeprecationWarning in Blender scripts — it hides migration signals.
2. NEVER use try/except AttributeError as a version check — use bpy.app.version or hasattr().
3. ALWAYS check the deprecation timeline BEFORE using any Blender API.
4. ALWAYS test addons on the OLDEST supported version, not just the newest.
5. NEVER assume backward compatibility of .blend files across major API rewrites (Grease Pencil 4.3, Slotted Actions 4.4, Compositor 5.0).
6. ALWAYS restore gpu.state to defaults at the end of draw callbacks.
7. NEVER use bgl in any new code — it is REMOVED in Blender 5.0.
8. ALWAYS use context.temp_override() instead of dict overrides in Blender 4.0+.

---

6. Reference Links

• references/methods.md — Error diagnosis functions, version detection API, compatibility checking utilities
• references/examples.md — Error-to-fix migration code for each error pattern (E-01 through E-25)
• references/anti-patterns.md — Version compatibility mistakes that cause errors, with explanations

Official Documentation

• Blender 4.0 Python API Changes
• Blender 4.1 Python API Changes
• Blender 4.2 Python API Changes
• Blender 4.3 Python API Changes
• Blender 4.4 Python API Changes
• Blender 5.0 Python API Changes
• Blender 5.1 Python API Changes
• Blender API Compatibility Notes
• Grease Pencil 4.3 Migration Guide