blender-core-versions

name	blender-core-versions
description	Use when writing Blender Python code that must work across multiple versions (3.x/4.x/5.x), or when migrating scripts between Blender versions. Prevents breakage from renamed APIs, removed modules (bgl in 5.0), and changed function signatures. Provides the complete breaking changes matrix, deprecation timeline, and version-safe coding patterns. Keywords: Blender version, migration, deprecated, breaking change, bgl removal, bpy.app.version, version compatibility, 3.x, 4.x, 5.x, API changes, which Blender version, what changed in Blender 4.
license	MIT
compatibility	Designed for Claude Code. Requires Blender 3.x/4.x/5.x with Python.
metadata	{"author":"OpenAEC-Foundation","version":"1.0"}

Blender Core Versions: Python API Version Matrix

1. Quick Reference

Version Detection

# Blender 3.x / 4.x / 5.x: ALWAYS use tuple comparison for version checks
import bpy
major, minor, patch = bpy.app.version  # e.g., (4, 2, 0)

# Version-safe conditional
if bpy.app.version >= (4, 0, 0):
    # Blender 4.0+ code path
    pass
else:
    # Blender 3.x fallback
    pass

See references/methods.md for complete version detection API.

Python Version Matrix

Blender	Python	VFX Platform
3.x	3.10	2023
4.0	3.10	2023
4.1	3.11	2024
4.2 LTS	3.11	2024
4.3	3.11	2024
4.4	3.11	2024
4.5 LTS	3.11	2024
5.0	3.11	2025
5.1	3.13	2026

Critical Breaking Changes Summary

Change	Removed In	Migration
Context override dicts on bpy.ops	4.0	context.temp_override()
MeshEdge.bevel_weight / .crease	4.0	mesh.attributes.get("bevel_weight_edge")
obj.face_maps	4.0	Integer face attributes
bone.layers[i] / pose.bone_groups	4.0	bone.collections
NodeTree.inputs/outputs.new()	4.0	NodeTree.interface.new_socket()
Principled BSDF socket names	4.0	Renamed: Subsurface Weight, Specular IOR Level, etc.
3D_UNIFORM_COLOR shader name	4.0	POLYLINE_UNIFORM_COLOR
Python OBJ/PLY importers	4.0	bpy.ops.wm.obj_import/export
Mesh.use_auto_smooth	4.1	Mesh.corner_normals + Smooth by Angle modifier
Light probe CUBEMAP/PLANAR/GRID	4.1	SPHERE / PLANE / VOLUME
mat.cycles.displacement_method	4.1	mat.displacement_method
blender_manifest.toml required	4.2	Replace bl_info dict with TOML manifest
EEVEE → BLENDER_EEVEE_NEXT	4.2	Check identifier string
bpy.types.AttributeGroup	4.3	AttributeGroupMesh, AttributeGroupPointCloud, etc.
Grease Pencil API rewrite	4.3	Complete API rewrite; see migration guide
EEVEE legacy properties	4.3	40+ properties removed
Subclass __init__ must call super()	4.4	Forward *args, **kwargs to parent
bpy.types.Sequence → bpy.types.Strip	4.4	Rename all Sequence references
Slotted Actions system	4.4	action.layers[0].strips[0].channelbag()
bgl module	5.0	gpu module (MANDATORY)
scene['cycles'] dict access	5.0	Attribute access on RNA properties
scene.node_tree (compositor)	5.0	scene.compositing_node_group
brush.sculpt_tool	5.0	brush.sculpt_brush_type
action.fcurves legacy API	5.0	Slotted Actions channelbag API
VSE end_frame	5.0	length property
VSE strip time property renames	5.1	frame_final_duration → duration, etc. (removal in 6.0)
Python 3.13	5.1	Check stdlib changes

---

2. Essential Patterns

Version-Safe Conditionals

ALWAYS use bpy.app.version tuple comparison. NEVER parse bpy.app.version_string.

# Blender 3.x / 4.x / 5.x: Version-safe conditional pattern
import bpy

if bpy.app.version >= (5, 0, 0):
    # Blender 5.0+ code
    comp_tree = scene.compositing_node_group
elif bpy.app.version >= (4, 0, 0):
    # Blender 4.0–4.x code
    comp_tree = scene.node_tree
else:
    # Blender 3.x code
    comp_tree = scene.node_tree

Feature Detection Pattern

ALWAYS prefer hasattr() checks over version comparisons when testing for a specific API.

# Blender 3.x / 4.x / 5.x: Feature detection pattern
import bpy

# Prefer feature detection over version check
if hasattr(bpy.types, "AttributeGroupMesh"):
    # Blender 4.3+ — type-specific attribute groups
    pass
else:
    # Blender < 4.3 — generic AttributeGroup
    pass

# For method existence
mesh = bpy.context.active_object.data
if hasattr(mesh, "corner_normals"):
    # Blender 4.1+ — use corner_normals
    normals = mesh.corner_normals
else:
    # Blender < 4.1 — use legacy auto_smooth
    mesh.use_auto_smooth = True

Context Override Pattern

# Blender 3.x: LEGACY context override (BROKEN in 4.0+)
override = {"object": obj, "active_object": obj}
bpy.ops.object.modifier_apply(override, modifier="Boolean")

# Blender 4.0+: temp_override (REQUIRED)
with bpy.context.temp_override(object=obj, active_object=obj):
    bpy.ops.object.modifier_apply(modifier="Boolean")

# Version-safe wrapper
def apply_modifier(obj, modifier_name):
    if bpy.app.version >= (4, 0, 0):
        with bpy.context.temp_override(object=obj, active_object=obj):
            bpy.ops.object.modifier_apply(modifier=modifier_name)
    else:
        override = {"object": obj, "active_object": obj}
        bpy.ops.object.modifier_apply(override, modifier=modifier_name)

Node Group Interface Pattern

# Blender 3.x: LEGACY (BROKEN in 4.0+)
node_group.inputs.new("NodeSocketFloat", "Width")
node_group.outputs.new("NodeSocketGeometry", "Geometry")

# Blender 4.0+: interface API (REQUIRED)
node_group.interface.new_socket(
    name="Width", in_out='INPUT', socket_type='NodeSocketFloat'
)
node_group.interface.new_socket(
    name="Geometry", in_out='OUTPUT', socket_type='NodeSocketGeometry'
)

EEVEE Identifier Pattern

# Blender 3.x: 'BLENDER_EEVEE'
# Blender 4.2–4.x: 'BLENDER_EEVEE_NEXT'
# Blender 5.0+: 'BLENDER_EEVEE' (changed back)
import bpy

def get_eevee_identifier():
    if bpy.app.version >= (5, 0, 0):
        return 'BLENDER_EEVEE'
    elif bpy.app.version >= (4, 2, 0):
        return 'BLENDER_EEVEE_NEXT'
    else:
        return 'BLENDER_EEVEE'

scene = bpy.context.scene
scene.render.engine = get_eevee_identifier()

Extension Manifest Pattern

# Blender 3.x / 4.0 / 4.1: bl_info dict in __init__.py
bl_info = {
    "name": "My Addon",
    "blender": (4, 0, 0),
    "category": "Object",
    "version": (1, 0, 0),
    "description": "My addon description",
}

# Blender 4.2+: blender_manifest.toml (REQUIRED for extensions)
# File: blender_manifest.toml
# schema_version = "1.0.0"
# id = "my_addon"
# version = "1.0.0"
# name = "My Addon"
# tagline = "Short description up to 64 chars"
# maintainer = "Dev Name <[e-mail]>"
# type = "add-on"
# blender_version_min = "4.2.0"

GPU Drawing Pattern (BGL → gpu Migration)

# Blender 3.x: bgl module (BROKEN in 5.0)
import bgl
bgl.glEnable(bgl.GL_BLEND)
bgl.glLineWidth(2)
shader = gpu.shader.from_builtin('3D_UNIFORM_COLOR')

# Blender 4.0+: gpu module (REQUIRED for 5.0+)
import gpu
gpu.state.blend_set('ALPHA')
gpu.state.line_width_set(2.0)
shader = gpu.shader.from_builtin('POLYLINE_UNIFORM_COLOR')

# ALWAYS restore gpu state at end of draw callbacks
gpu.state.blend_set('NONE')
gpu.state.line_width_set(1.0)

Compositor Access Pattern

# Blender 3.x / 4.x: scene.node_tree
scene = bpy.context.scene
scene.use_nodes = True
comp_tree = scene.node_tree

# Blender 5.0+: compositing_node_group
scene = bpy.context.scene
comp_tree = bpy.data.node_groups.new("MyComp", 'CompositorNodeTree')
scene.compositing_node_group = comp_tree

Slotted Actions Pattern (4.4+)

# Blender 3.x / 4.0–4.3: Legacy action.fcurves
action = bpy.data.actions.new("MyAction")
fcurve = action.fcurves.new(data_path="location", index=0)

# Blender 4.4+: Slotted Actions (legacy removed in 5.0)
action = bpy.data.actions.new("MyAction")
slot = action.slots.new()
layer = action.layers.new(name="Layer")
strip = layer.strips.new(type='KEYFRAME')
channelbag = strip.channelbags.new(slot=slot)
fcurve = channelbag.fcurves.new(data_path="location", index=0)

---

3. Common Operations: Migration Checklists

3.x → 4.0 Migration Checklist

• Replace ALL context override dicts with context.temp_override()
• Replace mesh.edges[i].bevel_weight with mesh.attributes.get("bevel_weight_edge")
• Replace mesh.edges[i].crease with mesh.attributes.get("crease_edge")
• Replace obj.face_maps with integer face attributes
• Replace bone.layers[i] with bone.collections
• Replace pose.bone_groups with bone collections + colors
• Replace NodeTree.inputs/outputs.new() with NodeTree.interface.new_socket()
• Update Principled BSDF socket names (Subsurface → Subsurface Weight, etc.)
• Replace 3D_UNIFORM_COLOR with POLYLINE_UNIFORM_COLOR
• Replace Mesh.calc_normals() (removed, now auto-calculated)
• Replace Python OBJ/PLY IO with bpy.ops.wm.obj_import/export
• Remove filename params, use filepath instead
• Update anim_utils.bake_action() to use BakeOptions dataclass

4.0 → 4.1 Migration Checklist

• Remove mesh.use_auto_smooth and mesh.auto_smooth_angle
• Use mesh.corner_normals for normal access
• Use "Smooth by Angle" modifier for angle-based smoothing
• Rename light probe types: CUBEMAP→SPHERE, PLANAR→PLANE, GRID→VOLUME
• Move mat.cycles.displacement_method to mat.displacement_method
• Add type checking for foreach_set() calls (now raises TypeError)
• Rename sequencer filter SUBSAMPLING_3x3 → BOX
• Use socket identifiers instead of indices for dynamic sockets

4.1 → 4.2 Migration Checklist

• Create blender_manifest.toml for extension system
• Handle statically typed IDProperties (no implicit type changes)
• Update EEVEE identifier: BLENDER_EEVEE → BLENDER_EEVEE_NEXT
• Move scene.cycles.motion_blur_position to scene.render.motion_blur_position
• Move scene.eevee.use_motion_blur to scene.render.use_motion_blur
• Replace blend_method with surface_render_method
• Replace object.load_reference_image with object.empty_image_add
• Update compositor mask node properties: width→mask_width, height→mask_height

4.2 → 4.3 Migration Checklist

• Replace bpy.types.AttributeGroup usage with type-specific classes
• Migrate ALL Grease Pencil code to new API
• Remove references to EEVEE legacy properties (contact shadows, SSR, bloom, etc.)
• Update reroute node handling to use socket_idname property
• Do NOT assign embedded IDs to PointerProperty

4.3 → 4.4 Migration Checklist

• Add super().__init__(*args, **kwargs) to ALL Blender type subclasses
• Rename bpy.types.Sequence references to bpy.types.Strip
• Adopt Slotted Actions API for new animation code
• Update paint.brush usage (now read-only property)
• Ensure pos attribute uses F32 FLOAT for GPU polyline drawing

4.x → 5.0 Migration Checklist

• Remove ALL import bgl — replace with gpu module
• Replace scene['cycles'] dict access with attribute access
• Replace scene.node_tree with scene.compositing_node_group
• Replace brush.sculpt_tool with brush.sculpt_brush_type
• Replace legacy action.fcurves with Slotted Actions channelbag API
• Replace VSE end_frame with length
• Update EEVEE identifier from BLENDER_EEVEE_NEXT back to BLENDER_EEVEE
• Remove usage of bundled private modules (animsys_refactor, etc.)
• Replace Image.bindcode with gpu.texture.from_image()
• Replace gpu.types.GPUShader() constructor with gpu.shader.create_from_info()

5.0 → 5.1 Migration Checklist

• Replace sculpt.sample_color with paint.sample_color
• Update to Python 3.13 — check stdlib compatibility
• Prepare for VSE time property renames (deprecated, removed in 6.0): frame_final_duration → duration, frame_final_start → left_handle, etc.

---

4. Reference Links

• references/methods.md — Complete version detection API: bpy.app.version, bpy.app.version_string, bpy.app.version_cycle
• references/examples.md — Migration code examples for EACH version transition (3.x→4.0, 4.0→4.1, 4.1→4.2, 4.2→4.3, 4.3→4.4, 4.4→5.0, 5.0→5.1)
• references/anti-patterns.md — Common version migration mistakes 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 4.5 Python API Changes
• Blender 5.0 Python API Changes
• Blender 5.1 Python API Changes
• Blender API Compatibility Notes
• Blender API Change Log