Blender Errors Version

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

Blender 4.1 Breaking Errors

Blender 4.2 Breaking Errors

Blender 4.3 Breaking Errors

Blender 4.4 Breaking Errors

Blender 5.0 Breaking Errors

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.

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