Continual learning (also called lifelong learning or incremental learning) is the ability of AI models to learn from new data and tasks sequentially without forgetting previously acquired knowledge.¹⁾ Continual learning frameworks provide the methods, architectures, and software tools that enable this capability, addressing the fundamental challenge of catastrophic forgetting that has historically limited the deployment of adaptive AI systems in production environments.

Catastrophic forgetting occurs when neural networks trained on new tasks or data substantially degrade their performance on previously learned tasks. Standard deep learning follows a train-freeze-deploy cycle, producing fixed models unable to adapt to changing data distributions, new task requirements, or evolving user needs.²⁾ Retraining from scratch is prohibitively expensive — costing millions in compute for large models — and impractical for systems that must adapt in real time.

• Elastic Weight Consolidation (EWC) — constrains important weights from changing when learning new tasks by adding a penalty based on the Fisher information matrix, which estimates parameter importance for previously learned tasks
• Synaptic Intelligence (SI) — online estimation of parameter importance based on training trajectory

• Progressive Neural Networks — allocate new capacity (columns) for each new task while freezing previous columns, preventing forgetting but increasing model size
• PackNet — uses network pruning to free up capacity for new tasks, iteratively compressing previous task knowledge into fewer parameters

• Experience Replay — stores a buffer of examples from previous tasks and interleaves them during training on new tasks
• Generative Replay — uses a generative model to produce synthetic examples of previous tasks instead of storing real data

Models that learn during inference itself, blurring the boundary between training and deployment. TTT operates through two mechanisms: TTT for Context (solving memory bottlenecks) and TTT for Discovery (solving search bottlenecks), enabling real-time adaptation without traditional retraining.³⁾

Research demonstrates that reinforcement learning naturally mitigates catastrophic forgetting more effectively than supervised fine-tuning. RL maintains or enhances general model capabilities when learning new tasks sequentially because it naturally scales policy updates according to reward signal variance, leading to more conservative updates for important parameters.⁴⁾

Introduced at NeurIPS 2025, this architecture treats a single model as interconnected optimization problems operating at different speeds:⁵⁾

• Fast-updating modules — handle immediate context
• Medium-speed modules — consolidate intermediate knowledge
• Slow-updating modules — preserve fundamental capabilities

The Continuum Memory System creates a spectrum of memory updating at different frequencies, preventing catastrophic forgetting by isolating knowledge updates across temporal scales. The HOPE implementation demonstrated unbounded in-context learning — models that continuously learn without forgetting.

• Avalanche (ContinualAI) — an end-to-end library for continual learning research built on PyTorch, providing benchmarks, strategies, and evaluation tools
• Sequoia — a research framework for continual and lifelong learning with standardized settings
• CLIB — Continual Learning In the Browser, enabling on-device continual learning

The shift from frozen to adaptive models enables:

• Domain adaptation without forgetting — single models handling medical, legal, and technical queries simultaneously
• Real-time personalization — models adapting to individual user preferences across sessions
• Reduced retraining costs — eliminating expensive full-retraining cycles
• Persistent agent memory — AI agents that accumulate knowledge over their operational lifetime

• Catastrophic Forgetting
• Transfer Learning
• Liquid Neural Networks