Memory System

CortexPrism features a sophisticated 5-tier memory architecture with hybrid retrieval combining FTS5 keyword search and cosine vector similarity, scored with exponential time decay.

Memory Architecture

retrieve(query, embedder)
  │
  ├── keywordSearch(query)   → FTS5 BM25 over episodic_memory + semantic_memory
  │
  ├── vectorSearch(embed)    → cosine similarity over stored embeddings
  │       embedding = embedder.embed(query) if embedder available
  │
  └── merge + decay-score
        score = raw_score × 2^(-age_days / half_life_days)
        sorted descending → top-K

Memory Tiers

Tier	Database Table	Retention	Content
Episodic	`episodic_memory`	Auto-decay based on half-life	Turn summaries — user+agent exchanges
Semantic	`semantic_memory`	Indefinite unless pruned	Injected facts / knowledge / entities
Reflection	`reflection_memory`	Consolidated weekly	LLM-extracted behavior patterns
Graph	`entity_graph`	Built from semantic extraction	Knowledge graph nodes and edges
Skills	`skills` table	Persisted indefinitely	Procedural knowledge from sessions

Storage

Table	Type	Contents
`episodic_memory`	Row	Turn summaries — user+agent exchanges
`semantic_memory`	Row	Injected facts / knowledge
`reflection_memory`	Row	LLM-extracted behaviour patterns
`entity_graph`	Row	Knowledge graph nodes and edges
`skills`	Row	Procedural knowledge from sessions
`episodic_memory_fts`	FTS5	Virtual table for keyword search on episodic
`semantic_memory_fts`	FTS5	Virtual table for keyword search on semantic

Retrieval Algorithm

1. FTS5 keyword search across episodic_memory and semantic_memory
   → BM25 ranking scores

2. Cosine vector similarity (if embedder available)
   → embedding = embedder.embed(query)
   → cosine similarity against stored embeddings

3. Merge + decay scoring
   → score = raw_score × 2^(-age_days / half_life_days)
   → half_life_days: configurable per tier (default: 7 days)

4. Sort descending → return top-K results

Embedding Providers

Provider	Backend	Model	Use Case
`OllamaEmbedder`	Ollama `/api/embeddings`	Configurable	Local embedding generation
`OpenAIEmbedder`	OpenAI API	`text-embedding-3-small`	Cloud embedding generation
`StubEmbedder`	Deterministic hash	—	No external service needed (default)

Memory Injection

injectMemory(systemPrompt, hits) prepends retrieved content to the system prompt:

--- Relevant Memory ---
[episodic] 2026-06-14: User: ... Assistant: ...
[semantic] CortexPrism uses SQLite WAL mode
---

This ensures the agent has relevant context from past interactions without exceeding token limits.

Operations

store: Save information to a memory tier (episodic or semantic)
search: Query memories across tiers with hybrid retrieval
retrieve: Get specific memories by ID
forget: Remove memories
compress: Summarize and archive older memories