🧠 Brains complement: IF an unreal-engine-skills-manager tool (external MCP) exists in this session, call it with {action: "load", skill: "animation-system"} for UE domain knowledge on this topic — correct APIs, architecture, best practices — and treat it as the rubric for any review / "best practices" question. If no such tool is available (e.g. running under Claude Code or Codex without that MCP), skip this line entirely and proceed with this skill alone — do NOT attempt the call.

Animation Sequence & Editing Skill

This skill covers the inspect → profile → preview → validate → bake workflow for safe animation bone edits with correct bone-space handling and constraint validation.

Loading skills: skills load via the engine's AgentSkillToolset (ListSkills / GetSkills) — there is no vibeue-skills-manager tool. Run the VibeUE services below with execute_python_code (unreal.AnimSequenceService.<method>() / unreal.SkeletonService.<method>()).

Related Skills:

• skeleton - For modifying skeleton bone transforms/hierarchy and retargeting modes
• animation-blueprint - For state machines and AnimGraph navigation

Workflow: Create skeleton profile → Learn constraints → Preview bone rotations → Validate pose → Bake to keyframes

🛡️ SAFE DISCOVERY: Always use VibeUE service methods

DO NOT use unreal.load_asset() in loops - causes memory crashes!

USE THESE SAFE METHODS:

• unreal.SkeletonService.list_skeletons(search_path) - Find skeletons
• unreal.AnimSequenceService.find_animations_for_skeleton(skeleton_path) - Find animations
• unreal.AnimSequenceService.list_anim_sequences(search_path, skeleton_filter) - List all animations

These methods query asset metadata WITHOUT loading assets into memory.

• animation-blueprint - For state machines and AnimGraph navigation

Workflow: Create skeleton profile → Learn constraints → Preview bone rotations → Validate pose → Bake to keyframes

⚠️ Critical Rules

1. Always Specify Bone Space

All bone rotations must specify the coordinate space. Default to "local" for user intent.

Space	Description	Use For
"local"	Relative to parent bone	Most edits (default)
"component"	Relative to skeletal mesh root	Cross-bone coordination
"world"	World coordinates	Rarely used for animations

# WRONG: Assuming space or not specifying
unreal.AnimSequenceService.apply_bone_rotation(path, "arm", rot, ...)

# CORRECT: Always specify space explicitly
unreal.AnimSequenceService.preview_bone_rotation(
    path, "upperarm_r", unreal.Rotator(0, 30, 0), "local", 0
)

2. Use Preview → Validate → Bake Workflow

Never apply edits directly without validation. Use the preview workflow:

import unreal

anim_path = "/Game/Anims/AS_Idle"

# Step 1: PREVIEW the edit
result = unreal.AnimSequenceService.preview_bone_rotation(
    anim_path, "upperarm_r", unreal.Rotator(0, 45, 0), "local", 0
)

# Step 2: VALIDATE against constraints
validation = unreal.AnimSequenceService.validate_pose(anim_path, True)  # Use learned constraints
if not validation.is_valid:
    for msg in validation.violation_messages:
        print(f"⚠️ {msg}")
    # Option A: Cancel and adjust
    unreal.AnimSequenceService.cancel_preview(anim_path)
    # Option B: Accept clamped values and continue

# Step 3: BAKE if valid
if validation.is_valid:
    result = unreal.AnimSequenceService.bake_preview_to_keyframes(
        anim_path, 0, -1, "cubic"
    )
    print(f"✓ Baked frames {result.start_frame} to {result.end_frame}")

3. Build Skeleton Profile Before Editing

Create a skeleton profile to get hierarchy, constraints, and learned ranges:

# WRONG: Editing without understanding the skeleton
unreal.AnimSequenceService.apply_bone_rotation(...)

# CORRECT: Build profile first
profile = unreal.SkeletonService.create_skeleton_profile("/Game/SK_Mannequin")
print(f"Skeleton has {profile.bone_count} bones")

# Check if constraints are available
if not profile.has_learned_constraints:
    # Learn from existing animations
    constraints = unreal.SkeletonService.learn_from_animations("/Game/SK_Mannequin", 50, 10)
    print(f"Learned from {constraints.animation_count} animations")

4. Use Quaternions Internally, Euler for Intent

User intent is expressed in Euler angles (degrees), but always use quaternions internally to avoid gimbal lock:

# User intent: "rotate forearm 30 degrees"
rotation_delta = unreal.Rotator(0, 30, 0)  # Euler (Roll, Pitch, Yaw)

# The service converts to quaternion internally
result = unreal.AnimSequenceService.preview_bone_rotation(
    anim_path, "lowerarm_r", rotation_delta, "local", 0
)

# To inspect quaternion values:
euler = unreal.AnimSequenceService.quat_to_euler(some_quat)

---

COMMON_MISTAKES

Wrong: Applying rotations without space

# WRONG - space is ambiguous
transform = unreal.Transform(rotation=some_rotation)
# This may be interpreted incorrectly

# CORRECT - always specify space
result = unreal.AnimSequenceService.preview_bone_rotation(
    anim_path, bone, rotation, "local", frame
)

Wrong: Editing without validation

# WRONG - direct edit without checking constraints
unreal.AnimSequenceService.apply_bone_rotation(
    path, "lowerarm_r", unreal.Rotator(0, 180, 0),  # Impossible elbow bend!
    "local", 0, -1, True
)

# CORRECT - preview → validate → bake
result = unreal.AnimSequenceService.preview_bone_rotation(...)
validation = unreal.AnimSequenceService.validate_pose(path, True)
if validation.is_valid:
    unreal.AnimSequenceService.bake_preview_to_keyframes(...)

Wrong: Guessing bone axis orientations

# WRONG - assuming pitch raises arm
rotation = unreal.Rotator(0, 90, 0)  # May not do what you expect!

# CORRECT - analyze reference pose first
ref_pose = unreal.AnimSequenceService.get_reference_pose(skeleton_path)
for bp in ref_pose:
    if bp.bone_name == "upperarm_r":
        euler = unreal.AnimSequenceService.quat_to_euler(bp.transform.rotation)
        print(f"Reference: Roll={euler.roll}, Pitch={euler.pitch}, Yaw={euler.yaw}")
        # Now you know the baseline to add deltas to

Wrong: Not building skeleton profile

# WRONG - editing without profile
unreal.AnimSequenceService.preview_bone_rotation(...)  # No constraints!

# CORRECT - build profile first
unreal.SkeletonService.create_skeleton_profile(skeleton_path)
# Now constraints are available for validation

⚠️ CRITICAL: Loading assets in loops causes crashes

# WRONG - Loading assets causes memory access violations (0xC0000005)
asset_subsystem = unreal.get_editor_subsystem(unreal.EditorAssetSubsystem)
assets = asset_subsystem.list_assets("/Game", recursive=True)
for asset_path in assets:
    anim = unreal.load_asset(asset_path)  # ❌ CRASHES!
    if anim and hasattr(anim, 'get_skeleton'):
        skeleton = anim.get_skeleton()  # Memory violation

# CORRECT - Use Asset Registry API (no loading required)
asset_registry = unreal.AssetRegistryHelpers.get_asset_registry()
filter = unreal.ARFilter(
    class_paths=[unreal.TopLevelAssetPath("/Script/Engine", "AnimSequence")],
    recursive_paths=True,
    package_paths=["/Game"]
)
anim_assets = asset_registry.get_assets(filter)
for asset_data in anim_assets:
    # Access metadata without loading
    anim_name = asset_data.asset_name
    anim_path = asset_data.object_path
    # Get skeleton path from asset registry tags
    skeleton_tag = asset_data.get_tag_value("Skeleton")

Why this crashes:

• unreal.load_asset() loads full asset into memory
• Loading hundreds of animations in a loop exhausts memory
• Unreal's garbage collection can't keep up
• Results in exception code 0xC0000005 (access violation)

Safe alternatives:

1. USE VibeUE's FindAnimationsForSkeleton() - BEST OPTION
2. Use Asset Registry API to query metadata without loading
3. Load one asset at a time with explicit unload
4. Filter by path before loading (limit scope)

BEST: Use VibeUE AnimSequenceService methods

# CORRECT - VibeUE safe discovery (no loading)
import unreal

skeleton_path = "/Game/Characters/SK_Mannequin"

# Get all animations for a skeleton - no loading!
anims = unreal.AnimSequenceService.find_animations_for_skeleton(skeleton_path)

for anim_info in anims[:10]:
    print(f"{anim_info.anim_name}")
    print(f"  Duration: {anim_info.duration:.2f}s")
    print(f"  Frames: {anim_info.frame_count}")
    print(f"  Path: {anim_info.anim_path}")

Other safe VibeUE methods:

• list_anim_sequences(search_path, skeleton_filter) - List all in path
• get_anim_sequence_info(anim_path) - Get single anim info
• search_animations(name_pattern, search_path) - Find by name pattern

---

IMPORTANT: Asset Path Format

All anim_path parameters require the FULL asset path (package_name), NOT the folder path (package_path).

When using AssetDiscoveryService.search_assets(), use package_name NOT package_path:

import unreal

# Search for an animation
results = unreal.AssetDiscoveryService.search_assets("Run", "AnimSequence")
if results:
    asset = results[0]
    
    # CORRECT: Use package_name (full asset path)
    anim_path = str(asset.package_name)  # e.g., "/Game/Animations/Run/AS_Run_Forward"
    
    # WRONG: Do NOT use package_path (folder only)
    # folder = asset.package_path  # e.g., "/Game/Animations/Run" - This will FAIL!
    
    # Now you can use the anim_path with AnimSequenceService
    info = unreal.AnimSequenceService.get_anim_sequence_info(anim_path)

---

Sub-docs available

Load these sibling docs for deeper coverage of specific topics:

• api-reference.md - Full Python API reference (SkeletonService profile/constraint methods, AnimSequenceService preview/edit/pose/visual capture, creation/helper/query methods, key structs). Also contains the secondary skill manifest for the merged "Animation Sequence Skill" content set.
• data-structures.md - Key data structures (FSkeletonProfile, FBoneConstraint, FLearnedBoneRange, FAnimationEditResult, FAnimationPoseCaptureResult, FBoneDelta) and full DTO reference (AnimSequenceInfo, BoneTrackData, AnimKeyframe, BonePose, AnimCurveInfo, CurveKeyframe, AnimNotifyInfo, SyncMarkerInfo).
• workflows.md - Editing workflows (inspect, preview/validate single bone, multi-bone atomic, manual constraints, learn from animations, copy/mirror pose, retarget preview) and creation workflows (from reference pose, from keyframe data, simple keyframes, rotation keyframes, wave animation example).
• patterns.md - Common patterns (listing animations, getting pose at time, adding curves, managing/configuring notifies) and the CRITICAL RULES checklist for creation/notify operations and asset paths.
• method-categories.md - Categorised table of every AnimSequenceService method by domain (Discovery, Creation, Helpers, Properties, Bone Tracks, Poses, Curves, Notifies, Notify Tracks, Sync Markers, Root Motion, Additive, Compression, Export, Editor).
• bone-rotation.md - Bone Rotation Axis Discovery: why bone local coordinate systems are non-intuitive and the required discovery workflow (reference pose values → analyze existing animations → incremental axis testing) before writing rotation animation code.

Sample scripts (run via execute_python_code)

• scripts/inspect_sequence.txt — safely inspect AnimSequences for a skeleton (metadata, no asset loading).