ACL 2026 · Agent Memory · Daily Literature Review

NEMORI: Replacing Designer Intuition About What to Remember
with the System's Own Prediction Error

What Deserves Memory: Adaptive Memory Distillation for LLM Agents — In-depth analysis of the core paper and five predecessors

ACL 2026 Main · Long 2026-08-04 acl-long.1607 · pp. 34789–34812 arXiv:2508.03341 v4 Subfield: Memory distillation / compression 26 candidate papers

The value of memory is no longer decided by designer heuristics—importance scores, emotion tags, or fact templates—but by the interaction sequence's own prediction error. What to store becomes an endogenous signal recoverable from data, rather than a manually encoded prior.

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WorkOfficial publication pagearXivCodeDataset
NEMORI
(core paper)
ACL 2026 acl-long.1607 · PDF arXiv:2508.03341
v1 2025-08-05 → v4 2026-04-16
nemori-ai/nemori
Existence confirmed through site search; direct retrieval blocked by permissions, so individual files were not verified
LoCoMo / LongMemEval-S
Generative Agents UIST 2023 (DOI Pending verification) arXiv:2304.03442 joonspk-research/generative_agents (Pending verification) No public benchmark
MemoryBank AAAI 2024 (Official proceedings page not found) arXiv:2305.10250 No reachable repository verified SiliconFriend scenarios (not publicly hosted)
A-MEM No main-conference publication record found arXiv:2502.12110 (v9) agiresearch/A-mem LoCoMo
MemoryOS EMNLP 2025 Main, Oral arXiv:2506.06326 BAI-LAB/MemoryOS LoCoMo
Zep / Graphiti No conference publication record arXiv:2501.13956 (2025-01-20) Graphiti open source (link unverified) DMR / LongMemEval
LoCoMo (benchmark) ACL 2024 acl-long.747 arXiv:2402.17753 snap-research/locomo Project page
LongMemEval (benchmark) ICLR 2025 — xiaowu0162/LongMemEval Same as left
Verification standard. Entries marked pending, not found, or unverified reflect WebFetch permission errors or searches that did not locate official pages. Leaving a field blank is preferable to inventing a URL, a strict rule for this report series.

2 · In-Depth Analysis of the Core Paper

2.1 Abstract Summary and Positioning

NEMORI's problem fits in one sentence: How should a memory system decide which information is worth retaining? The authors diagnose existing answers as encoded designer intuition: importance scores in Generative Agents, emotion tags in emotional memory, fact templates in Mem0, and heat scores in MemoryOS. The paper describes these methods as “encoding designer intuition rather than learning from the data itself”, with two consequences: subjective bias causes irreversible information distortion, while systemic bloat causes excessive storage and amplifies retrieval noise.

NEMORI draws on predictive coding (Rao & Ballard 1999; Friston's 2010 free-energy principle): information predictable from existing knowledge is redundant; the unpredictable portion is the candidate for memory. The system first uses existing semantic knowledge to generate an anticipatory schema for an upcoming interaction segment, then distills the difference between actual content and expectation into semantic knowledge.

The innovation in one sentence: Replace a manually specified scoring function for what to remember with a measure of the system's own prediction failures.

2.2 Motivation and Problem Evidence

The argument develops through three levels.

Level 1: Capacity Constraints Are Hard Limits. Stateless LLMs rely on growing interaction histories despite limited context windows and the Lost in the Middle phenomenon. This is field-wide consensus rather than NEMORI's distinctive claim.

Level 2: Heuristic Distillation Introduces Irreversible Loss. This is the paper's real target. Table 1 reorganizes memory systems around Distillation / Management / Retrieval three stages (see Table A), revealing a structural fact: only five of 13 baselines have a distillation entry, and all use manually imposed priors; another seven leave that column blank, storing raw interactions wholesale and shifting the burden to management and retrieval.

Level 3: The Problem Is Quantified.

This cost evidence is stronger than the performance gain alone. Cheaper and better suggests that the discarded material is redundancy rather than useful information—exactly the evidence needed for the claim that heuristics cause systemic bloat.

2.3 The Paper's Argument

The argument is not simply a list of modules. It is a deductive chain linked by three priors that form the paper's backbone and distinguish it from another generic memory framework.

Observation ① Interaction sequences have natural group boundaries; messages within a group contextualize one another. ⇒ [Structure Prior · Integrity of Episode] ⇒ Memory's atomic unit is an episode, not a message or fixed-size chunk. ⇒ Design: LLM-driven Local Message Partitioning rather than fixed-length splitting. Observation ② Memory serves recall; recall is reasoning and allocentric reconstruction, whereas raw episodes are egocentric and noisy. ⇒ [Representation Prior · Asymmetry of Perspective] ⇒ Stored representations must differ from raw representations through a perspective shift. ⇒ Design: Narrative Episode Generation with narrative rewriting and episodic cues. Observation ③ Interaction sequences are highly redundant; predictive coding makes surprise a consolidation candidate. ⇒ [Distillation Prior · Predictability Implies Redundancy] ⇒ Distillation criterion = difference between prediction and reality. ⇒ Design: Anticipatory Schema → Prediction Error Distillation.
The critical leap is from observation ③ to the design. It requires a nontrivial assumption: the current semantic knowledge base can generate a meaningful expectation. With an empty knowledge base at cold start, the expectation is empty and everything becomes prediction error, degenerating into full distillation. With a saturated knowledge base, expectations cover most content and distilled output approaches zero. The paper does not experimentally characterize these cold-start-to-saturation dynamics, the clearest gap in its argument.

2.4 Methodology and Mechanisms

Table A · Paper Table 1: Memory Systems Reorganized by Distillation / Management / Retrieval (Transcribed)

CategoryMethodDistillationManagementRetrieval
Retrieval-timeLewis et al. (2020) RAG——Similarity search
Management-timePacker et al. (2023) MemGPT—Tiered storageFunction calls
Management-timeZhong et al. (2024) MemoryBank—Summary + forgetting—
Management-timeKang et al. (2025) MemoryOS—Heat scoringTwo-step search
Management-timeLi et al. (2025b)—Hierarchical summaryMulti-step search
Management-timeAnokhin et al. (2025)—Graph updateGraph spreading
Management-timeXu et al. (2025) A-MEM—Adaptive note linking—
Management-timeRasmussen et al. (2025) Zep—Validity managementReranking
Distillation-timePark et al. (2023) Generative AgentsImportance scoringReflection treesWeighted scoring
Distillation-timeHuang et al. (2024)Emotion tagging—Emotion matching
Distillation-timeChhikara et al. (2025) Mem0Facts extraction——
Distillation-timeLi et al. (2025a)Summary + persona—Noun overlap
Distillation-timePan et al. (2025)TopicToken compression—
Distillation-timeNEMORI (this paper)Prediction errorAgnostic—
This table is itself a powerful positioning tool. NEMORI's Management entry is Agnostic(agnostic/neutral), deliberately avoiding competition at the management layer and claiming only the distillation layer. This scope restriction is candid, but also becomes a weakness examined in §2.8.

Formal Definition · Module 1: Episodic Memory Integration

(1a) Local message partitioning B_t = {m_1,…,m_z}, m_i = (r_i, c_i, τ_i), window w ∈ Z⁺ O ← f_LLM(P_par ‖ B_t), O = {O_1,…,O_n}, a partition of indices {1,…,w} P = {P_1,…,P_n} Map indices back to messages to obtain raw episodes (1b) Narrative generation (N_j, c_j) ← f_LLM(P_nar ‖ P_j) # N_j: narrative; c_j: retrieval cue v_j ← f_emb(c_j ‖ N_j) M_j = (c_j, N_j, P_j, v_j) (1c) Associative integration (supersede semantics) C = {U_1,…,U_{K_e}} ← Search(D_e, v_j, K_e) idx ← f_LLM(P_sel ‖ (c_j,N_j) ‖ {(c_k,N_k)}) idx = k ⇒ (c_ν,N_ν) ← f_LLM(P_int ‖ c_k ‖ N_k ‖ c_j ‖ N_j) M_ν = (c_ν, N_ν, P_k ‖ P_j, f_emb(c_ν ‖ N_ν)) # M_ν replaces U_k idx = -1 ⇒ No continuity; insert M_j as an independent entry

Formal Definition · Module 2: Semantic Knowledge Distillation (Core Contribution)

(2a) Anticipatory schema synthesis S_in ← Evoke(M_in, M) Native implementation: S_in ← Top-K_s { S_r ∈ D_s | sim(v_in, u_r) > τ }, τ = 0.70 P̂_in ← f_LLM(P_ant ‖ c_in ‖ S_in) # Predict the episode from existing knowledge (2b) Prediction-error distillation K_in = {k_1,…,k_d} ← f_LLM(P_dis ‖ P_in ‖ P̂_in) ↑ ground truth ↑ prediction (2c) Semantic consolidation (three-way decision) S̃_q ← Search(D_s, u_q, K_m), K_m = 5 (δ, idxs, k_μ) ← f_LLM(P_con ‖ k_q ‖ {k_h}) δ ∈ { new : Insert (k_q, u_q) merge : Replace entries at idxs with (k_μ, f_emb(k_μ)) conflict : Remove outdated entries and replace with (k_q, u_q) } Response generation R̃_e ← Search(D_e, v_Q, k) # k = 10 narrative episodes R̃_s ← Search(D_s, v_Q, m) # m = 2k = 20 semantic entries a ← f_LLM(P_ans ‖ Q ‖ R_e ‖ R_p ‖ R_s) # R_p: r = 2 original episodes

Table B · Hyperparameters and Sensitivity Coverage

HyperparameterValueRoleSensitivity analysis?
τ Similarity threshold0.70Context-evocation threshold for anticipatory schemasNo — key gap
K_e Episodic candidates5Retrieval count during integrationNo
K_m Semantic candidates5Retrieval count during consolidationNo
K_s Evoked entries10Anticipatory-schema context sizeNo
w Observation window20Messages triggering partitioningYes — Figure 2 / Table 11, w ∈ {5,10,20,30,40}
k Episodic retrieval10Response generationYes — Figure 3 / Table 12, k ∈ {2…30}
m Semantic retrieval20Response generation (= 2k)Varies with k
r Original episodes2Full text included in the response contextNo

Pipeline and Cost Breakdown

Raw dialogue stream B_t │ ├─[① Partition]──▶ LLM identifies episode boundaries P = {P_1..P_n} Cost 15.3% │ ├─[② Narrate]────▶ (N_j, c_j) narrative + cue, index v_j Cost 38.3% ← largest │ │ │ └─[③ Integrate]─▶ supersede / insert Cost 16.2% │ ↓ D_e (episodic store) │ └─[④ Distill]────▶ Evoke(τ=0.70) ─▶ anticipatory schema P̂ │ ├─ Actual P vs expected P̂ ⇒ prediction error K Cost 30.3% ← core │ └─[⑤ Consolidate]─▶ new / merge / conflict ↓ D_s (semantic store)

Figure 1 · Mean LoCoMo LLM-Judge Scores: Eight Methods × Two Generation Models

Source: Average column of NEMORI Table 2. Dashed lines mark each model's Full Context oracle level. Hover for exact values.

gpt-4o-mini gpt-4.1-mini Full Context baseline

2.5 Experimental Design and Quantitative Results

Evaluation Setup

ItemLoCoMoLongMemEval-S
Size10 conversations, averaging 24K tokens; 1,540 questions500 conversations, averaging 105K tokens
Question typesTemporal / Open Domain / Multi-Hop / Single-HopSix categories: preference, assistant, temporal, cross-session, knowledge update, and user
MetricLLM-judge (0–100) / F1 / BLEU-1LLM-judge
Generation modelsgpt-4.1-mini and gpt-4o-mini; embeddings: text-embedding-3-small; judge: gpt-4o-mini
Number of runsSingle run; no variance reported

Table C · Main LoCoMo Results (Paper Table 2; LLM-Judge / F1 / BLEU-1)

gpt-4.1-mini

MethodTemporalOpen DomainMulti-HopSingle-HopAverage
Full Context (oracle)74.2 / 47.5 / 40.056.6 / 28.4 / 22.277.2 / 44.2 / 33.786.9 / 61.4 / 53.480.6 / 53.3 / 45.0
RAG-409627.4 / 22.3 / 19.128.8 / 17.9 / 13.931.7 / 20.1 / 12.835.9 / 25.8 / 22.032.9 / 23.5 / 19.2
LangMem50.8 / 48.5 / 40.959.0 / 32.8 / 26.471.0 / 41.5 / 32.584.5 / 51.0 / 43.673.4 / 47.6 / 40.0
Zep60.2 / 23.9 / 20.043.8 / 24.2 / 19.353.7 / 30.5 / 20.466.9 / 45.5 / 40.061.6 / 36.9 / 30.9
Mem056.9 / 39.2 / 33.247.9 / 23.7 / 17.768.2 / 40.1 / 30.371.4 / 48.6 / 42.066.3 / 43.5 / 36.5
A-MEM66.7 / 40.3 / 33.737.5 / 13.4 / 12.755.7 / 30.4 / 20.064.0 / 45.0 / 39.861.4 / 39.4 / 33.2
MemoryOS37.7 / 36.5 / 27.460.4 / 30.2 / 25.662.4 / 34.0 / 25.868.9 / 44.2 / 37.560.6 / 39.9 / 32.5
NEMORI77.3 / 58.7 / 50.756.3 / 31.7 / 25.174.8 / 40.8 / 31.787.0 / 55.7 / 49.580.8 / 52.1 / 45.0
Relative improvement reported by the paper+15.9 / +21.0 / +24.0%—+5.4% / — / —+3.0 / +9.2 / +13.5%+10.1 / +9.5 / +12.5%

gpt-4o-mini

MethodTemporalOpen DomainMulti-HopSingle-HopAverage
Full Context (oracle)56.2 / 44.1 / 36.148.6 / 24.5 / 17.266.8 / 35.4 / 26.183.0 / 53.1 / 44.772.3 / 46.2 / 37.8
RAG-409623.7 / 19.5 / 15.732.6 / 19.0 / 13.531.3 / 18.6 / 11.732.0 / 22.2 / 18.630.2 / 20.8 / 16.4
LangMem24.9 / 31.9 / 26.247.6 / 29.4 / 23.552.4 / 33.5 / 23.961.4 / 38.8 / 33.151.3 / 35.8 / 29.4
Zep58.9 / 44.8 / 38.139.6 / 22.9 / 15.750.5 / 27.5 / 19.363.2 / 39.7 / 33.758.5 / 37.5 / 30.9
Mem050.4 / 44.4 / 37.640.6 / 27.1 / 19.460.3 / 34.3 / 25.268.1 / 44.4 / 37.761.3 / 41.5 / 34.2
A-MEM54.2 / 38.1 / 33.822.9 / 9.0 / 8.643.6 / 24.0 / 18.858.2 / 35.6 / 29.252.5 / 32.4 / 27.0
MemoryOS38.0 / 38.5 / 27.545.8 / 26.0 / 19.252.5 / 35.2 / 24.162.5 / 43.7 / 37.754.5 / 39.9 / 31.9
NEMORI67.6 / 57.3 / 47.645.8 / 23.9 / 18.561.7 / 38.1 / 26.081.9 / 54.8 / 43.873.0 / 50.3 / 39.7
Relative improvement reported by the paper+14.8 / +27.9 / +24.9%—+2.3 / +8.2 / +3.2%+20.3 / +23.4 / +16.2%+19.1 / +21.2 / +16.1%

Table D · Independently calculated: NEMORI vs Full Context category-level results (LLM-judge)

Categorygpt-4.1-mini ΔRelative togpt-4o-mini ΔRelative to
Temporal Reasoning+3.1 pp+4.18%+11.4 pp+20.28%
Open Domain−0.3 pp−0.53%−2.8 pp−5.76%
Multi-Hop−2.4 pp−3.11%−5.1 pp−7.63%
Single-Hop+0.1 pp+0.12%−1.1 pp−1.33%
Average (paper's definition)+0.2 pp+0.25%+0.7 pp+0.97%
Average (F1)−1.2 pp−2.25%+4.1 pp+8.87%
This is the report's most important recalculation. The paper's +10.1% / +19.1% compares against the strongest memory-system baseline(LangMem 73.4 for gpt-4.1-mini; Mem0 61.3 for gpt-4o-mini), not Full Context. Against Full Context, NEMORI with gpt-4.1-mini records two wins and two losses, a +0.25% mean advantage, and F1 2.25% lower; with gpt-4o-mini, one win and three losses, with a +0.97% mean advantage. In other words, nearly all of NEMORI's mean advantage over full context comes from Temporal Reasoning alone.

Table E · Memory-Construction Cost (Paper Table 3; LoCoMo / gpt-4o-mini)

MethodLLM-judgeAPI callsInput (k)Output (k)Total tokens (k)Cost per point*
LangMem51.3920.6898.3112.01010.219.7
Mem061.31602.21483.4210.01693.427.6
A-MEM52.51175.5912.6236.81149.421.9
MemoryOS54.51016.1404.5122.0526.59.7
NEMORI73.0373.2277.245.7322.94.4
Improvement reported by the paper+19.1%↓59.5%↓31.5%↓59.2%↓38.7%—

* Cost per point is calculated here as total tokens divided by the LLM-judge score, comparing efficiency after accounting for performance differences. NEMORI's cost per score point is 1/6.3 of Mem0's and 1/2.2 of MemoryOS's. The paper's ↓38.7% compares against the cheapest baseline, MemoryOS; relative to Mem0, the reduction is ↓80.9%.

Table F · Ablations (Paper Table 5) + Relative Declines Calculated Here

ConfigurationNative managementgpt-4o-miniΔgpt-4.1-miniΔ
w/o NEMORI (no memory)–0.6 / 0.5 / 0.9−99.2%1.2 / 1.6 / 1.5−98.5%
Nemori-s (direct distillation replaces prediction error)✓51.7 / 36.4 / 28.9−29.2%66.0 / 41.4 / 34.9−18.3%
Nemori-s (without native management)✗52.0 / 36.6 / 29.1−28.8%65.5 / 41.1 / 34.1−18.9%
w/o e (without episodic retrieval)✓64.6 / 46.2 / 37.1−11.5%74.7 / 48.2 / 40.9−7.5%
w/o e (replaced by naive RAG)✗65.0 / 46.2 / 36.9−11.0%74.9 / 48.1 / 40.7−7.3%
w/o s (without semantic retrieval)✓54.7 / 39.6 / 31.7−25.1%76.9 / 50.0 / 42.9−4.8%
w/o p (fixed partitions of 20 messages)✓68.0 / 47.4 / 36.8−6.8%75.7 / 48.1 / 40.9−6.3%
Full NEMORI✓73.0 / 50.3 / 39.7—80.8 / 52.1 / 45.0—

Table G · Construction-Cost Breakdown (Paper Table 9, gpt-4o-mini)

ComponentInput (k)Output (k)Total (k)Share
Partition (§3.2.1)44.74.649.315.3%
Narration (§3.2.2)99.823.9123.638.3%
Integration (§3.2.3)43.88.452.216.2%
Distillation (§3.3)88.98.897.730.3%
Narration (38.3%), rather than prediction-error distillation (30.3%), is the largest cost component, yet no clean ablation removes narration while retaining raw episodes. Table 6's Partitioned→Partitioned scores only 75.3 (−6.8%), but simultaneously changes both indexing and retrieval representations. The most expensive component lacks a clean ablation.

Table H · Retrieval-Strategy Ablation (Paper Table 6, LoCoMo / gpt-4.1-mini)

Index representationRetrieved representationLLM-judgeF1BLEU-1
NarrativeNarrative (default)76.950.042.9
PartitionedNarrative76.450.743.7
NarrativePartitioned77.050.242.6
PartitionedPartitioned75.350.142.7

Across four combinations, the LLM-judge range is only 1.7 pp(75.3–77.0), and the F1 range is 0.7 pp. This ablation actually suggests that indexing/retrieval representation barely matters, in tension with the strong Representation Prior in §2.3. N→N is the default, yet N→P achieves a slightly higher LLM-judge score of 77.0.

Table I · Third-Party Integration (Paper Table 7): NEMORI as a Front-End Distiller

Host systemModelInputLLM-judgeCore ScoreMemTokens
A-MEMgpt-4o-miniRaw (P)52.552.6397K
A-MEMgpt-4o-miniNEMORI (K)50.9 (↓3.0%)55.8 (↑6.1%)142K (↓64.3%)
A-MEMgpt-4.1-miniRaw (P)61.460.4498K
A-MEMgpt-4.1-miniNEMORI (K)59.0 (↓3.9%)64.1 (↑6.1%)243K (↓51.3%)
MemoryOSgpt-4o-miniRaw (P)54.659.2405K
MemoryOSgpt-4o-miniNEMORI (K)54.0 (↓1.1%)60.3 (↑1.9%)190K (↓53.1%)
MemoryOSgpt-4.1-miniRaw (P)60.766.9354K
MemoryOSgpt-4.1-miniNEMORI (K)61.4 (↑1.2%)69.2 (↑3.4%)194K (↓45.3%)

Table J · Scalability (Paper Table 8, LongMemEval-S, 105K Average Tokens)

Question types4o-mini Full Ctx4o-mini NEMORIRelative to4.1-mini Full Ctx4.1-mini NEMORIRelative to
Single-session Preference6.746.7+597%16.786.7+419%
Single-session Assistant89.383.9−6.0%98.292.9−5.4%
Temporal Reasoning42.161.7+46.6%60.272.2+19.9%
Multi-session38.351.1+33.4%51.155.6+8.8%
Knowledge Update78.261.5−21.4%76.979.5+3.4%
Single-session User78.688.6+12.7%85.790.0+5.0%
Average55.064.2+16.7%65.674.6+13.7%

Full Context uses 101K tokens; NEMORI uses 3.7–4.8K (↓95–96%). Relative changes are calculated in this report.

Table K · Hyperparameter Sensitivity

Observation window w (Table 11, gpt-4.1-mini)

wTemporalOpen DomainMulti-HopSingle-HopOverall
577.059.473.886.380.4
1077.657.377.085.780.7
20 (default)77.356.374.887.080.8
3076.660.479.486.081.2
4076.354.277.386.480.7

Retrieval count k (Figure 3 / Table 12)

kgpt-4o-minigpt-4.1-mini
265.0 / 66.6*73.4
570.079.3
10 (default)73.080.8
1572.582.7
2072.583.4
3073.0 / 74.4*83.3

* Extracted Figure 3 and Table 12 values differ slightly at k=2 and k=30 (65.0 vs 66.6; 73.0 vs 74.4). This report could not determine which values reflect the main-text convention and presents both transparently.

2.6 A Phase Transition: The Most Convincing Qualitative Evidence

On LongMemEval-S Single-session Preference, gpt-4o-mini scores only 6.7 with the full 101K-token context, but 46.7 with NEMORI's 3.7–4.8K distilled tokens (+597%). For gpt-4.1-mini, the change is 16.7 → 86.7 (+419%, 5.19×).

This goes beyond a marginal compression gain; it is a sign reversal: Reducing context to 1/25 improves performance by 5–7×. For preference questions, raw context is actively harmful rather than merely insufficient—preferences are scattered across long conversations and buried in irrelevant content, preventing localization within 101K tokens. Prediction-error distillation isolates new preferences inconsistent with the existing profile as semantic knowledge.

This is the paper's only evidence of a change in kind rather than degree : Elsewhere, differences from Full Context remain within ±20% (Table J); Preference alone approaches an order-of-magnitude change. If the paper were to center one claim, it should be that memory combats context dilution rather than context length, but it does not develop this transition as a standalone core argument.

The Counterevidence Also Deserves Attention: Knowledge Update sees gpt-4o-mini fall from 78.2 to 61.5 (−21.4%). Yet conflict is one of NEMORI's three semantic-consolidation states, specifically designed for knowledge updates. The dedicated mechanism fails most severely on its intended question type—an internal contradiction the paper does not discuss.

Figure 2 · Six LongMemEval-S Categories: Full Context vs NEMORI

Source: NEMORI Table 8 (gpt-4o-mini). Full Context uses 101K tokens; NEMORI uses 3.7–4.8K. Note the phase-transition-like gain on Preference and regression on Knowledge Update. Hover for exact values.

Full Context (101K tokens) NEMORI (3.7–4.8K tokens)

2.7 Assessment of Value

The substantive contribution consists of three things beyond better performance:

  1. Redefining what to store as a measurable quantity. Before NEMORI, importance, heat, emotion were all exogenous, requiring a prompt, threshold, or decay coefficient. Prediction error is endogenous, jointly determined by current knowledge and input, without an additional configuration interface. The shift resembles moving from handcrafted features to a self-supervised objective.
  2. An existence proof of 80.9% lower cost and 19.1% better performance(Table E, relative to Mem0). It challenges the assumption that memory-system cost is unavoidable: much of it comes from storing unnecessary material.
  3. A Detachable, Modular Contribution. Table I shows prediction-error distillation can serve as a front-end filter for other systems: A-MEM's storage falls 51–64% while Core Score rises 6.1%. The mechanism therefore does not depend on the rest of NEMORI and can be adopted directly by A-MEM, MemoryOS, or Mem0.

Independently Reusable Design Principles

DesignReusable formTransfer destination
Predictability Implies RedundancyA write gate that first predicts the input and stores only the differenceKV-cache compression, RAG indexing, and agent-trajectory logs
LLM-driven episode-boundary partitioningTable F attributes a −6.3–6.8% ablation drop to it at only 15.3% of cost, indicating good valueLong-document chunking and multiround tool-trajectory segmentation
Three-way consolidation new / merge / conflictExplicitly distinguish new / merge / conflict instead of a uniform upsertIncremental knowledge-graph updates and user-profile maintenance
Narrative rewriting (allocentric transformation)Decouple stored and raw representationsTable H shows ≤1.7pp gains, leaving cost-effectiveness uncertain

2.8 Limitations

(A) Author-Acknowledged Limitations — Quoted from the Formal ACL Version

  1. Distillation-centered scope: “NEMORI focuses on distillation and adopts naive strategies for management and retrieval. This simplicity suffices for the benchmarks studied here, but may become a bottleneck for tasks that demand more sophisticated reasoning over memory. The performance we report should be understood as reflecting this design scope rather than the ceiling of what a complete memory system could achieve.”
  2. Interfaces are not yet standardized: “The interfaces we define are currently conceptual, and due to the lack of standardized protocols in the area, concrete integration still requires case-by-case implementation.”
A verifiable version difference: The arXiv v4 HTML moves from Section 5 directly to References and Appendices A–D, without a Limitations section. The two points above come from the official ACL Anthology PDF; cite that version.

(B) Nine Additional Criticisms, Each with Evidence

① The Near-Zero Advantage Over Full Context Is Obscured by the Reporting Baseline(Argument gap). All relative gains use the strongest memory-system baseline as denominator. Against Full Context (Table D), gpt-4.1-mini gains only 0.2pp in Average (+0.25%), while F1 is 1.2pp lower (52.1 vs 53.3, −2.25%) and Multi-Hop is 2.4pp lower. This differs from the abstract's impression of improved performance alongside reduced storage: when the full context fits, NEMORI's performance gains are within the noise scale, leaving cost as the real selling point. A narrower claim of equal performance at one-fifth the cost would be stronger.

② The Core Mechanism's Contribution Declines Sharply with Model Capability(Metric validity + extrapolation risk). In Table F, w/o s(removing the semantic layer distilled from prediction errors) reduces gpt-4o-mini by −25.1% but gpt-4.1-mini by only −4.8%. Across just one model generation, the marginal contribution shrinks 5.2×. Linear extrapolation to frontier models could imply a near-zero semantic-layer contribution: prediction-error distillation may compensate for weaker models' retrieval and integration abilities rather than supply irreplaceable information. No stronger model tests whether this trend levels off; this is the most needed experiment.

③ The Knowledge-Update conflict Mechanism Fails Most on Knowledge-Update Questions(Internal contradiction). Table J: Knowledge Update gpt-4o-mini 78.2 → 61.5 (−21.4%), the only double-digit negative change among six categories, while Preference improves 597% on the same model. If conflict really removes outdated entries, this should be its strongest category. A plausible hypothesis is that conflict depends on Search(D_s, u_q, K_m=5) retrieving the old entry. If old and new expressions fall below the similarity threshold, the conflict is never detected—pointing directly to the untested sensitivity of τ = 0.70. The paper offers no discussion.

④ The Critical Hyperparameter τ = 0.70 Has No Sensitivity Analysis(Experimental gap). Table B shows sweeps of w(5→40) and k(2→30), but none for τ. Yet τ Yes is the context-evocation threshold for anticipatory schemas, directly controlling how much the system believes it knows and thus prediction-error magnitude—the central knob of the Distillation Prior. Skipping τ while sweeping w examines secondary parameters while leaving the central mechanism unchecked. Additionally, K_e = K_m = 5, K_s = 10, r = 2 also lack ablations.

⑤ Native Management Has a Negative Contribution in Both Comparisons(Argument gap). Table F: Nemori-s 51.7 with management versus 52.0 without (−0.3); w/o e 64.6 with management versus 65.0 with naive RAG (−0.4). Management slightly hurts performance in both comparisons. The paper calls this negligible management overhead. More rigorously, single-run differences of ±0.3–0.4pp without variance cannot establish either harmlessness or harm, but the two differences have the same sign. Thus “Agnostic” in Table 1's Management column is more than a scope restriction: it reflects an unvalidated default.

⑥ No Head-to-Head Comparison with Learned Memory Policies(Missing key baselines). Another major 2025–2026 line delegates memory operations to RL-trained policies—Memory-R1, MemAct, and AgeMem—using exogenous rewards, whereas NEMORI uses endogenous prediction error. These directly compete on what should drive memory writes, yet among seven baselines, none comes from the RL branch. The implicit claim that endogenous signals outperform external rewards remains entirely untested. This is the most valuable next comparison.

⑦ Table I's Metrics Move in Opposite Directions, Raising Validity Questions(Metric issue). When NEMORI precedes A-MEM, LLM-judge falls 3.0%/3.9%, while Core Score rises 6.1%/6.1%. The paper uses the latter to claim maintained or improved performance. When two metrics disagree within one experiment, favoring the positive one requires justification. The paper does not explain Core Score's definition, its divergence from LLM-judge, or why the main table does not use it.

⑧ Narrow Evaluation Overpromises “LLM Agents” in the Title(Experimental design). LoCoMo and LongMemEval-S are both conversational question-answering benchmarks, with no tool use, web or embodied environments, or planning tasks such as ALFWorld, WebArena, or PDDL. Agent memory must retain behavioral experience—failed tool calls or unworkable paths—whose redundancy differs from conversational facts. LoCoMo also has only 10 conversations, 1,540 questions, one run, and no confidence intervals, while several key Table D differences are only 0.1–1.2pp, indistinguishable at this sample size.

⑨ Limitations of This Report (Disclosure). This analysis uses extracted text from the official ACL PDF and arXiv v4 HTML; the code was not run; github.com/nemori-ai/nemori was located through search only, without verifying whether it fully implements the paper. Its public description calls it “a minimalist MVP,” potentially differing from the paper's “a production-grade implementation”; reproduction efforts should note this. The discrepancy between Figure 3 and Table 12 also remains unresolved.

3 · Related Work: A Chain of Increasingly Endogenous Priors

Selection criterion: All five works address the same question—what to remember or forget—and are explicitly classified in NEMORI's Table 1. They represent five ways to turn the same knob; NEMORI attempts to remove that knob.

3.1 Generative Agents — Park et al., UIST 2023

Problem addressed. The first operational long-term agent-memory loop: a memory stream records every observation, retrieval weights importance × recency × relevance three factors, and reflection synthesizes low-level observations into high-level insights. It is the first entry in NEMORI Table 1 with a populated Distillation column.

Unresolved problem.importance is rated 1–10 by a prompted LLM, without supervision linking that score to downstream utility. It proxies the designer's intuition about importance. Overrating creates systemic bloat; underrating causes irreversible loss. More fundamentally, importance is an absolute quantity that does not vary with existing knowledge: a sentence scores the same on its first and tenth occurrence.

How the core paper responds. NEMORI replaces an absolute quantity with a relative quantity: information value equals surprise relative to current knowledge. The tenth repetition is matched by Evoke , covered by the anticipatory schema, and yields no distilled output. Table F's Nemori-s drops 18.3–29.2%, quantifying the cost of replacing this criterion.

Transfer of key designs. Generative Agents' reflection tree evolves in NEMORI into the merge consolidation state, triggered only when semantically adjacent entries are retrieved rather than when accumulated importance crosses a fixed threshold. A counter becomes an associative match.

3.2 MemoryBank — Zhong et al., AAAI 2024

Problem addressed. Forgetting becomes a first-class operation: the Ebbinghaus forgetting curve makes memory strength decay exponentially with time and increase with repeated recall, providing an early computable answer to what to forget.

Unresolved problem. The forgetting curve is a prior about time rather than a content criterion. An unvisited week-old fact about a drug allergy decays at the same rate as unvisited week-old small talk. Importance is outsourced to access frequency, which depends on what questions are asked and provides little information during cold starts or infrequent use.

How the core paper responds. NEMORI avoids temporal decay. Forgetting happens before writing: predictable information never enters semantic storage, and stored entries are removed only during conflict when new information contradicts them. Time decay becomes predictability filtering plus contradiction-based removal—forgetting shifts from postprocessing to write gating.

The lineage's most interesting sign reversal: MemoryBank's Hebbian intuition that repeated recall strengthens memory is reversed in NEMORI—repeated content is discarded rather than strengthened because it is predictable. Repetition means “retain more strongly” under memory strength, but “already known, no need to store again” under predictive coding.

3.3 A-MEM — Xu et al., 2025 (Brief by agreement; discussed in detail in earlier reports)

Problem addressed. Inspired by Zettelkasten, memory entries generate keywords and tags, link to existing entries, and trigger neighboring entries'memory evolution when new memories arrive. Without a predefined schema, it exemplifies self-organizing structure.

Unresolved problem. A-MEM optimizes organization among stored items but is silent on whether to store them: its Distillation column is empty. Links therefore form over unfiltered material; noisy entries also generate tags and links, propagating redundancy from storage into graph structure.

How the core paper responds. Table I answers directly: feeding NEMORI's distilled K rather than raw episodes P to A-MEM reduces MemTokens from 397K to 142K (↓64.3%), while Core Score rises from 52.6 to 55.8 (↑6.1%). A-MEM's organizational ability is unchanged; the material it organizes is cleaner.

Transfer of key designs. A-MEM's new-entry-driven updates become NEMORI's Supersede: M_ν direct replacement U_k, with P_k ‖ P_j preserving raw provenance. A-MEM uses append-style evolution(old entries are rewritten but remain), whereas NEMORI uses replacement-style evolution(old entries are displaced)—cheaper, but more irreversible.

3.4 MemoryOS — Kang et al., EMNLP 2025 Main (Oral)

Problem addressed. Operating-system paging becomes short-/mid-/long-term memory storage, using heat score to govern movement between tiers alongside two-stage retrieval. This is highly engineered heuristics; the paper reports a LoCoMo gain over its baseline of F1 +48.36%, BLEU-1 +46.18% (gpt-4o-mini).

Unresolved problem. Heat scores remain exogenous: migration thresholds, decay coefficients, and capacities are manually configured. More importantly, the system decides which tier to use, not whether to store an item—everything enters short-term storage. Hierarchy shifts the cost of bloat from retrieval latency to tier management.

A Cross-Paper Quantitative Comparison (This Report's Observation). Under NEMORI's common evaluation setup (Table C, gpt-4o-mini), MemoryOS's mean LoCoMo LLM-judge score is 54.5, F1 39.9——below Mem0 in the same table (61.3 / 41.5). This contrasts sharply with MemoryOS's self-reported +48.36% F1. The figures need not contradict because baselines, prompts, and judges differ, but together show: self-reported memory-system gains depend heavily on the evaluation harness; independent, standardized reproduction is essential. Zep shows the same pattern: it reports +18.5% and −90% latency on LongMemEval, yet averages only 58.5 on LoCoMo in Table C (gpt-4o-mini), also below Mem0. This is itself an underappreciated methodological problem in the field.

Transfer of key designs. MemoryOS's hierarchy becomes two orthogonal stores in NEMORI (D_e episodic / D_s semantic), and migration shifts from heat thresholds to nonempty prediction errors. The hierarchy changes from time-based tiers to division by representation type, aligning with McClelland et al.'s Complementary Learning Systems theory, which the paper explicitly cites.

3.5 Zep / Graphiti — Rasmussen et al., 2025

Problem addressed. Use a temporal knowledge graph handles expiring memory: edges carry validity intervals, new facts invalidate rather than delete old edges, enabling point-in-time queries and conflict resolution.

Unresolved problem. Validity management first requires information to be structured as triples, itself a lossy distillation guided by manually chosen entity/relation schemas. Graph extraction is also expensive, while Zep averages only 58.5 / 61.6 on LoCoMo in the common evaluation; its Temporal Reasoning score of 60.2 (gpt-4.1-mini) trails NEMORI's 77.3—a system explicitly designed for temporal semantics loses by 17.1pp on temporal questions.

How the core paper responds. NEMORI uses conflict for the same problem at much lower cost: no graph maintenance, only deciding whether new evidence contradicts an old semantic entry. The price is losing point-in-time queries: NEMORI cannot answer what a user's preference was three months ago after purging that entry. Table J's Knowledge Update −21.4% may be the bill for this inexpensive conflict resolution.

Transfer of key designs. Zep's conservative invalidate-rather-than-delete strategy becomes purge-and-replace in NEMORI. This is the lineage's sole regression rather than advance: NEMORI is weaker on this dimension. Future work could restore temporal validity within the prediction-error framework (see §5 ⑤).

4 · Technical Evolution

Core question: What is worth remembering, and where does the criterion come from? │ ┌───────────────────────────────┴────────────────────────────────┐ │ │ [Exogenous, manually encoded priors] [Self-organizing structure, no schema] │ │ 2023 Generative Agents — importance × recency × relevance 2025 A-MEM — Zettelkasten links │ [Absolute importance; reflection tree] │ [Generated tags; neighbor evolution] │ │ ✗ No distillation 2023 MemGPT — virtual memory paging │ │ [Tiered storage; function calls] │ │ │ 2024 MemoryBank — Ebbinghaus forgetting curve │ │ [Temporal prior; recall reinforcement] │ │ │ 2025 MemoryOS — heat-score three-tier paging ← engineered heuristics ──┤ │ [EMNLP 2025 Oral; self-reported F1 +48.4%] │ │ │ 2025 Zep/Graphiti — temporal-validity graph │ │ [Validity intervals; invalidate rather than delete] │ │ │ └──────────────┬─────────────────────────────────────────────────┘ │ Shared gap: Exogenous criteria. Thresholds, coefficients, and schemas require manual configuration without supervision linking them to utility. │ ├──────────────────────┬──────────────────────────┐ ▼ ▼ ▼ [Internalize external rewards] [Replace priors with endogenous signals] [Evaluation/governance] 2025–26 Memory-R1 / MemAct 2026 NEMORI (ACL Long) 2026 Forgetting benchmarks / AgeMem unified policy ═══════════════════ memory poisoning / RL rewards learn operations Prediction error distills security/governance surveys ✗ Requires task rewards ✓ No extra supervision ✗ High training cost ✓ Cost ↓80.9% vs Mem0 ╲ ╱ ╲ ╱ ✗ No head-to-head comparison (§2.8, criticism ⑥) — The clearest current gap —

Underlying Logic: Criteria Become Increasingly Internal

StageSource of criterionRepresentativeWhat must be configured manually
I. Encoded intuitionThe designer's semantic intuitionGenerative AgentsImportance prompt and threshold
II. Cognitive priorEmpirical regularities of human memoryMemoryBankForgetting-curve half-life
III. Structural priorLet entries organize themselvesA-MEMLinking policy (schema no longer needed)
IV. Engineering priorCombine multiple intuitions in a heat functionMemoryOS / ZepHeat coefficients, tier capacities, graph schema
V. Exogenous rewardFeedback from downstream tasksMemory-R1 / MemAct / AgeMemReward design and RL training budget
VI. Endogenous signalThe system's own prediction failuresNEMORIOne similarity threshold τ (without sensitivity analysis)

Two Key Turning Points: IV→V delegates the criterion to optimization: if manual design fails, learn it from rewards, at the cost of task rewards and training. IV→VI delegates it to system state: let the system measure surprise, at the cost that criterion quality depends entirely on anticipatory-schema quality.

This Report's Central Judgment on the Evolution: NEMORI claims to eliminate designer intuition, but actually compresses it from a semantic prior(what matters) into a geometric prior(how similar is sufficiently known). This is genuine dimensionality reduction: fewer geometric priors are more transferable and easier to tune automatically, but they are not eliminated. The paper conducts no experiment on precisely this residual prior (τ).

5 · Open Challenges and Research Opportunities

5.1 Theory

① Formalizing Cold-Start-to-Saturation Dynamics (High Value, Low Barrier). Prediction-error distillation output |K_in| is a function of existing knowledge |D_s| : |D_s| = 0 degenerates into full distillation, while |D_s| → ∞ approaches zero. The curve determines steady-state memory size, yet the paper never measures it. An actionable experiment: across LoCoMo's ten conversations, plot the joint trajectory of |K_in| with |D_s| by session index, testing whether saturation exists and depends on τ. This requires only logging the current pipeline, with no new training.

② τ and Prediction-Error Quality: Quantifying the Trade-Off.τ High ⇒ fewer evoked entries ⇒ weaker expectation ⇒ more false surprise (redundant storage); τ low ⇒ more evoked entries ⇒ stronger expectation ⇒ false negatives (missed new information). This is a standard precision–recall trade-off, but no empirical curve has been provided. Sweep τ ∈ [0.5, 0.9] and record (a) semantic-store size, (b) per-category LoCoMo scores, and (c) conflict trigger counts. The third directly tests the hypothesis in §2.8, criticism ③.

③ Comparing Attainable Limits of Endogenous Signals and External Rewards. Prediction error is an unsupervised criterion, whereas RL reward is a supervised criterion. In principle, the latter has no lower ceiling because it can learn any criterion, including prediction error. The question becomes: At what training budget does an RL memory policy surpass the training-free prediction-error criterion? This experiment could identify a crossover point and adjudicate the two branches in §4.

5.2 Engineering and Applications

④ Evaluate Agent Settings (Most Urgent). NEMORI's title says “for LLM Agents,” but both benchmarks are dialogue QA. On ALFWorld, WebArena, or τ-bench, define an episode as a tool-call sequence and prediction error as the difference between expected and actual tool outputs. The transfer is almost literal: Predictive coding naturally fits expected-versus-actual outcomes, precisely the structure of agent trajectories. Success here would be more persuasive than dialogue results.

⑤ Restore Zep's Temporal Validity Within Predictive Coding. NEMORI's conflict purges entries for efficiency, losing historical queries. Change conflict from purge-and-replace to marking invalid_at and appending, filtering by query time only during retrieval. Storage growth should be limited because old distilled entries are short, while temporal information is restored. Test directly on LongMemEval-S Knowledge Update and Temporal Reasoning to see whether this repairs the −21.4% regression.

⑥ Memory Stability in Online, Dynamic Settings. Current evaluation constructs memory offline and asks questions afterward; real agents read and write continuously. An unaddressed online risk is that early distillation errors contaminate anticipatory schemas, systematically distorting later prediction errors in a positive feedback loop. This closely resembles the How Memory Management Impacts LLM Agents(acl-long.27) finding of error propagation at ACL 2026—its use of future task outcomes as a memory-quality signal offers a ready-made way to clean NEMORI's semantic store retrospectively.

5.3 Emerging Directions

⑦ Reversible Distillation or Controllable Loss. NEMORI's distillation is irreversible: although M_j retains P_j the original text, the semantic layer K_in cannot be inverted. Could prediction-error distillation have an adjustable lossiness control, switching one memory system between expensive high fidelity and cheap low fidelity? This naturally connects to rate–distortion memory compression (arXiv:2607.08032): prediction error corresponds to residual coding in rate–distortion theory; NEMORI effectively implements a residual encoder without an explicit rate constraint. Making that constraint explicit is the shortest path to unifying the two lines.

⑧ Multiple Perspectives for Anticipatory Schemas. Currently, Evoke uses one similarity retrieval to generate one expectation. Generate K expectations from factual, preference, and causal perspectives; use the intersection of their errors as high-confidence new information and the union as a candidate pool. This may reduce the missed conflicts in §2.8, criticism ③. It parallels MAGMA's four orthogonal graphs (acl-long.1709), but at distillation rather than retrieval.

⑨ Prediction Error as a Memory-Poisoning Attack Surface. A concrete, as-yet-unproposed risk: an attacker who infers the semantic store could craft high-error but worthless inputs, forcing garbage into memory, because NEMORI's write gate depends entirely on manipulable surprise. This may be easier than attacking heuristics: the input need only look surprising, not important. Combined with arXiv:2607.06595's poisoning framework, this is an immediately testable attack.

⑩ The Missing Decisive Comparison Is the Largest Opportunity. The opportunity is more specific than exploring predictive coding: no study evaluates heuristic distillation, structural self-organization, RL policies, and prediction error under the same harness, model, and retrieval budget. MemoryOS's self-reported +48.4% versus below-Mem0 performance in a third-party harness (§3.4) shows that this gap already causes substantive confusion. A rigorous four-way reproduction study could be more valuable than another incremental advance along any one branch.

6 · Related-Work Comparison

WorkPublicationVenue / publicationCore contributionMain metric (source)Relationship to the core paper
NEMORI2026-07
(arXiv 2025-08)
ACL 2026 Main, Long Prediction error as the memory-distillation criterion LoCoMo avg 73.0 / 80.8(Table 2); construction 322.9k tokens (Table 3) Core paper
Generative Agents2023-04UIST 2023memory stream + importance×recency×relevance + reflectionNo public benchmark scoreOrigin of the problem: Absolute importance → relative surprise
MemoryBank2023-05AAAI 2024Ebbinghaus-curve-driven memory decaySelf-reported scenario evaluation; absent from NEMORI baselinesTemporal prior: Forgetting moves from postprocessing to write gating
A-MEM2025-02No main-conference publication found (arXiv v9)Zettelkasten self-organizing links + neighbor evolutionLoCoMo avg 52.5 / 61.4 (NEMORI Table 2)Orthogonal layer: Table 7 shows front-end distillation cuts MemTokens 64.3% and raises Core 6.1%
MemoryOS2025-06EMNLP 2025 Main, OralHeat-score-driven three-tier pagingSelf-reported LoCoMo F1 +48.36%; third-party harness average 54.5 / 60.6Highly engineered heuristics: Hierarchical management → two orthogonal stores
Zep / Graphiti2025-01No conference publication recordTemporal knowledge graph + validity intervalsSelf-reported DMR 94.8%, LongMemEval +18.5%; third-party LoCoMo average 58.5 / 61.6Temporal dimension: Invalidate → purge (the sole regression)
LoCoMo2024-02ACL 2024 LongVery-long-conversation memory benchmark10 conversations / 1,540 questions / 24K tokensEvaluation foundation: Small sample size prevents distinguishing Table D's 0.1–1.2pp differences
LongMemEval2024-10ICLR 2025Six-category long-term interaction memory evaluation500 conversations / 105K tokensWhere the phase transition appears: The +597% Preference result comes from this benchmark

Three Trends in This Table

  1. Performance is saturating; cost is not. From Generative Agents to NEMORI, LoCoMo means rise to 73–81, but NEMORI exceeds Full Context by only 0.2–0.7pp (Table D). The next order-of-magnitude advance will not come from LoCoMo scores.
  2. Self-reported gains and independent reproduction systematically diverge. MemoryOS (+48.4% → below Mem0 independently) and Zep (+18.5% → below Mem0 independently) are two separate examples.
  3. Publication venues are moving upward. Many representative 2023–2025 works were arXiv papers or workshops (A-MEM still lacks a main-conference record; Zep lacks a publication record). By 2025–2026, the area regularly reaches EMNLP/ACL long papers and oral presentations, with tightening review standards.

7 · Other Recent Work Worth Following

How Memory Management Impacts LLM Agents: An Empirical Study of Experience-Following Behavior (2026-07, ACL 2026 Main Long)

EverMemOS: A Self-Organizing Memory Operating System for Structured Long-Horizon Reasoning (2026-07, ACL 2026 Main Long)

MAGMA: A Multi-Graph based Agentic Memory Architecture for AI Agents (2026-07, ACL 2026 Main Long)

Dynamic Long Context Reasoning over Compressed Memory via End-to-End RL (LycheeMemory) (2026-07, ACL 2026 Main Long)

FOREVER: Forgetting Curve-Inspired Memory Replay for Language Model Continual Learning (2026-07, ACL 2026 Main Long)

Scaling Self-Evolving Agents via Parametric Memory (TMEM) (2026-06, arXiv)

When Agents Remember Too Much: Memory Poisoning Attacks on LLM Agents (2026-07, arXiv)

From Recall to Forgetting: Benchmarking Long-Term Memory for Personalized Agents (2026-04, arXiv)

8 · One-Sentence Summary

NEMORI's key contribution is not its LoCoMo score (+0.25% over Full Context), but evidence that 80% of memory-system cost goes toward information the system already knows—alongside the LongMemEval Preference transition from 6.7 to 46.7 when 101K tokens are reduced to 4K: the enemy of long context is dilution, not length.