---
type: claim
domain: ai-alignment
secondary_domains: [collective-intelligence]
description: "Agent memory systems that conflate knowledge, identity, and operations produce six documented failure modes; Tulving's three memory systems (semantic, episodic, procedural) map to distinct containers with different growth rates and directional flow between them"
confidence: likely
source: "Cornelius (@molt_cornelius) 'Agentic Note-Taking 19: Living Memory', X Article, February 2026; grounded in Endel Tulving's memory systems taxonomy (decades of cognitive science research); architectural mapping is Cornelius's framework applied to vault design"
created: 2026-03-31
depends_on:
  - "long context is not memory because memory requires incremental knowledge accumulation and stateful change not stateless input processing"
related:
  - "vault structure is a stronger determinant of agent behavior than prompt engineering because different knowledge graph architectures produce different reasoning patterns from identical model weights"
reweave_edges:
  - "vault structure is a stronger determinant of agent behavior than prompt engineering because different knowledge graph architectures produce different reasoning patterns from identical model weights|related|2026-04-03"
---

# memory architecture requires three spaces with different metabolic rates because semantic episodic and procedural memory serve different cognitive functions and consolidate at different speeds

Conflating knowledge, identity, and operational state into a single memory store produces six documented failure modes: operational debris polluting search, identity scattered across ephemeral logs, insights trapped in session state, search noise from mixing high-churn and stable content, consolidation failures when everything has the same priority, and retrieval confusion when the system cannot distinguish what it knows from what it did.

Tulving's three-system taxonomy maps to agent memory architecture with precision. Semantic memory (facts, concepts, accumulated domain understanding) maps to the knowledge graph — atomic notes connected by wiki links, growing steadily, compounding through connections, persisting indefinitely. Episodic memory (personal experiences, identity, self-understanding) maps to the self space — slow-evolving files that constitute the agent's persistent identity across sessions, rarely deleted, changing only when accumulated experience shifts how the agent operates. Procedural memory (how to do things, operational knowledge of method) maps to methodology — high-churn observations that accumulate, mature, and either graduate to permanent knowledge or get archived when resolved.

The three spaces have different metabolic rates reflecting different cognitive functions. The knowledge graph grows steadily — every source processed adds nodes and connections. The self space evolves slowly — changing only when accumulated experience shifts agent operation. The methodology space fluctuates — high churn as observations arrive, consolidate, and either graduate or expire. These rates scale with throughput, not calendar time.

The flow between spaces is directional. Observations can graduate to knowledge notes when they resolve into genuine insight. Operational wisdom can migrate to the self space when it becomes part of how the agent works rather than what happened in one session. But knowledge does not flow backward into operational state, and identity does not dissolve into ephemeral processing. The metabolism has direction — nutrients flow from digestion to tissue, not the reverse.

## Additional Evidence (supporting)

**Hermes Agent (Nous Research, 26K+ stars)** implements a 4-tier memory system that independently converges on the three-space taxonomy while adding a fourth space:
- **Prompt Memory (MEMORY.md)** — 3,575-character hard cap, always loaded, curated identity and preferences. Maps to the episodic/self space.
- **Session Search (SQLite+FTS5)** — LLM-summarized session history with lineage preservation. Maps to semantic/knowledge space. Retrieved on demand, not always loaded.
- **Skills (procedural)** — markdown procedure files with progressive disclosure (names first, full content on relevance detection). Maps to procedural/methodology space.
- **Honcho (dialectic user modeling)** — optional 4th tier with 12 identity layers modeling the user, not the agent. This is a genuinely new space absent from the three-space taxonomy — user modeling as a distinct memory type with its own metabolic rate (evolves per-interaction but slower than session state).

The 4-tier system corroborates the three-space architecture while suggesting the taxonomy may be incomplete: user/interlocutor modeling may constitute a fourth memory space not captured by Tulving's agent-centric framework. Cache-aware design ensures that learning (adding knowledge) doesn't grow the token bill — the memory spaces grow independently of inference cost.

## Challenges

The three-space mapping is Cornelius's application of Tulving's established cognitive science framework to vault design, not an empirical discovery about agent architectures. Whether three spaces is the right number (versus two, or four) for agent systems specifically has not been tested through controlled comparison. The metabolic rate differences are observed in one system's operation, not measured across multiple architectures. Additionally, the directional flow constraint (knowledge never flows backward into operational state) may be too rigid — there are cases where a knowledge claim should directly modify operational behavior without passing through the identity layer.

---

Relevant Notes:
- [[long context is not memory because memory requires incremental knowledge accumulation and stateful change not stateless input processing]] — this claim establishes the binary context/memory distinction; the three-space architecture extends it by specifying that memory itself has three qualitatively different subsystems, not one
- [[methodology hardens from documentation to skill to hook as understanding crystallizes and each transition moves behavior from probabilistic to deterministic enforcement]] — the methodology hardening trajectory operates within the procedural memory space, describing how one of the three spaces internally evolves

Topics:
- [[_map]]
