Cited by 4AI-based Problem Solving and PlanningNatural Language Processing TechniquesSpeech and dialogue systems

Hindsight: Structured Agent Memory that Retains, Recalls, and Reflects

Open access
Latimer, Christopher, Boschi, Nicolò, Neeser, Andrew, Bartholomew, Chris, Srivastava, Gaurav, Wang, Xuan, Ramakrishnan, Naren·2026·Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 3: System Demonstrations)

Abstract

Christopher Latimer, Nicolò Boschi, Andrew Neeser, Chris Bartholomew, Gaurav Srivastava, Xuan Wang, Naren Ramakrishnan. Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 3: System Demonstrations). 2026.

AI snapshot

Written from the paper’s full text.

TL;DR

HINDSIGHT is a memory system for AI agents that organizes long-term memory into four networks (world, experience, observation, opinion) and exposes retain, recall, and reflect operations. It reports strong benchmark accuracy, including 83.6% on LongMemEval and 83.2% on LoCoMo with a 20B open-source backbone, and 91.4% on LongMemEval with Gemini-3 Pro.

Key findings

  • HINDSIGHT with a 20B open-source backbone reaches 83.6% on LongMemEval and 83.2% on LoCoMo, outperforming full-context GPT-4o (60.2% LongMemEval) and prior memory systems such as Zep (71.2% LongMemEval, 75.1% LoCoMo) and Memobase (75.8% LoCoMo).
  • Scaling the backbone improves results: OSS-120B reaches 89.0% on LongMemEval and 85.7% on LoCoMo; Gemini-3 Pro reaches 91.4% on LongMemEval and 89.6% on LoCoMo, with the LongMemEval 91.4% described as the best result across all systems including frontier-backed ones.
  • Per-category LongMemEval gains over full-context GPT-4o are largest on long-horizon categories: temporal reasoning rises from 45.1% to 79.7% (20B) and 91.0% (Gemini-3); preference from 20.0% to 66.7% (20B) and 80.0% (Gemini-3); multi-session from 44.3% to 79.7% (20B) and 87.2% (Gemini-3) per Table 4.
  • The system is open-source under MIT, available via `pip install hindsight-all` and Docker, with 13.3K GitHub stars and 763 forks to date, and in production use at Fortune 500 enterprises as stated in the abstract.

Methods

  • System/demo paper: HINDSIGHT is a compound AI system with TEMPR for temporal entity memory priming retrieval (retain and recall) and CARA for coherent adaptive reasoning agents (reflect), backed by PostgreSQL with pgvector.
  • Evaluation uses LongMemEval (500 questions, conversations up to 1.5M tokens) and LoCoMo (multi-session human conversations up to 35 sessions), reporting overall accuracy and per-category breakdowns against full-context GPT-4o, Zep, Mem0, A-Mem, Memobase, Supermemory, and Backboard.
  • Recall runs four parallel retrieval channels—HNSW vector search, BM25 keyword matching, graph traversal, and temporal filtering—merged with Reciprocal Rank Fusion and refined by a cross-encoder reranker, with a token budget controlling retrieved context.

Limitations

  • The paper states: HINDSIGHT relies on LLM calls for fact extraction, entity resolution, and opinion formation, so extraction errors can propagate; all evaluation was on English-language benchmarks; opinion evolution has not been validated through formal user studies; the system requires PostgreSQL with pgvector (though the embedded Python package bundles its own instance); and temporal parsing uses rules plus a lightweight T5 model that may miss highly ambiguous or culturally specific temporal references.
  • Evident from the text: this demo paper summarizes key results from a fuller evaluation in Latimer et al. (2025), so full architecture and evaluation details are not contained here.
  • Evident from Table 2: benchmark comparisons include systems with different backbones and some missing entries (e.g., full-context GPT-4o has no LoCoMo score), so cross-system comparisons are not uniformly controlled.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.18653/v1/2026.acl-demo.27

Cites

30 of 30 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

2 of 3 cited sources checked · 2 supported · 0 flagged

  • Premisecitation
    § 2

    The four-network design is inspired by cognitive science models of human memory.

    “Our four-network design is inspired by cognitive science models of human memory (Sumers et al., 2024; Shan et al., 2025).”
    Quote in the paperNot a substantial claim1 of 2 sources checked
    • cites Sumers et al., 2024

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites Shan et al., 2025 source
  • Findingown data
    § Table 2

    HINDSIGHT with a 20B open-source model achieves 83.2% accuracy on LoCoMo.

    “HINDSIGHT (OSS-20B) 83.6 83.2”
    Quote in the paperNot a substantial claim
    • Rests on an assumption: The benchmark results for HINDSIGHT and the compared systems on LongMemEval and LoCoMo are directly comparable and not confounded by differences in evaluation protocols, prompt engineering, or backbone model capabilities.
  • Findingreasoning
    § 4.2

    For a bank with 10,000 memory units, recall completes in under 200ms excluding the backbone LLM call.

    “For a bank with 10,000 memory units, recall completes in under 200ms excluding the backbone LLM call”
    Quote in the paperSubstantial claim
  • Findingown data
    § 6.1 Overall Results

    HINDSIGHT's 91.4% accuracy on LongMemEval is the best result across all systems including those backed by frontier models.

    “Scaling the backbone to 120B reaches 89.0%, and using Gemini-3 Pro for answer generation pushes accuracy to 91.4%, the best result across all systems including those backed by frontier models.”
    Quote in the paperSubstantial claim
  • Findingown data
    § Abstract

    HINDSIGHT with Gemini-3 Pro achieves 91.4% accuracy on LongMemEval.

    “with Gemini-3 Pro, LongMemEval accuracy reaches 91.4%.”
    • Also stated in: § Table 2 · plain
      “HINDSIGHT (Gemini-3) 91.4 89.6”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The benchmark results for HINDSIGHT and the compared systems on LongMemEval and LoCoMo are directly comparable and not confounded by differences in evaluation protocols, prompt engineering, or backbone model capabilities.
  • Classified as probably not a substantial claim. 22
  • May combine two claims. 15
  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation
    § 3.2

    This is conceptually related to verbal reinforcement in Reflexion, but applied to persistent opinion state rather than episodic task feedback.

    “This is conceptually related to verbal reinforcement in Reflexion (Shinn et al., 2023), but applied to persistent opinion state rather than episodic task feedback.”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites Shinn et al., 2023 source
  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Findingnone given
    § Abstract

    HINDSIGHT has 13.3K GitHub stars and 763 forks to date.

    “with 13.3K GitHub stars and 763 forks to date”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Findingnone given
    § Abstract

    HINDSIGHT is open-source under the MIT license, available as a Python package (pip install hindsight-all) and Docker image.

    “The system is open-source under the MIT license, available as a Python package (pip install hindsight-all) and Docker image”
    • Also stated in: § 5 · plain
      “HINDSIGHT is available as an installable package via pip install hindsight-all and as a Docker image”
    Quote in the paperNot a substantial claim
  • May combine two claims.

    Findingown data
    § Table 2

    HINDSIGHT with Gemini-3 achieves 91.4% on LongMemEval and 89.6% on LoCoMo.

    “HINDSIGHT (Gemini-3) 91.4 89.6”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The benchmark results for HINDSIGHT and the compared systems on LongMemEval and LoCoMo are directly comparable and not confounded by differences in evaluation protocols, prompt engineering, or backbone model capabilities.
  • May combine two claims.

    Findingown data
    § Table 2

    HINDSIGHT with a 20B open-source model outperforms full-context GPT-4o and all prior memory systems on LongMemEval and LoCoMo.

    “HINDSIGHT with a 20B open backbone beats full-context GPT-4o and prior systems.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The benchmark results for HINDSIGHT and the compared systems on LongMemEval and LoCoMo are directly comparable and not confounded by differences in evaluation protocols, prompt engineering, or backbone model capabilities.
  • Probably not a substantial claim: may not pass S4 (based). May combine two claims.

    Findingnone given
    § 1

    CARA produces preference-conditioned responses and maintains opinions that evolve as new evidence arrives.

    “CARA (Coherent Adaptive Reasoning Agents) produces preference-conditioned responses and maintains opinions that evolve as new evidence arrives.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Findingnone given
    § 4.4

    Facts are extracted in the original language, entities are stored in their native script, and reflect responses match the query language.

    “Facts are extracted in the original language, entities are stored in their native script, and reflect responses match the query language.”
    Quote in the paperNot a substantial claim
  • May combine two claims.

    Findingown data
    § Table 2

    HINDSIGHT with OSS-120B achieves 89.0% on LongMemEval and 85.7% on LoCoMo.

    “HINDSIGHT (OSS-120B) 89.0 85.7”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The benchmark results for HINDSIGHT and the compared systems on LongMemEval and LoCoMo are directly comparable and not confounded by differences in evaluation protocols, prompt engineering, or backbone model capabilities.
  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingnone given
    § 4.4

    HINDSIGHT detects the input language at retain time and preserves it through the pipeline.

    “HINDSIGHT detects the input language at retain time and preserves it through the pipeline.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Study design and conductnone given
    § Limitations

    HINDSIGHT's temporal parsing uses a combination of rules and a lightweight T5 model, which handles common date expressions well but may miss highly ambiguous or culturally specific temporal references.

    “Temporal parsing uses a combination of rules and a lightweight T5 model, which handles common date expressions well but may miss highly ambiguous or culturally specific temporal references.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given
    § Limitations

    All evaluation was conducted on English-language benchmarks (LongMemEval and LoCoMo).

    “All evaluation was conducted on English-language benchmarks (LongMemEval and LoCoMo).”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisenone given
    § Computed: evidence_span , evidence_count

    Directives are user-defined hard rules that are injected into prompts at reflect time, with a priority order and an active flag.

    “Directives are user-defined hard rules that are injected into prompts at reflect time, with a priority order and an active flag:”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisereasoning
    § 6.4 Qualitative Case Study

    After session 3, the consolidation engine refines the existing observation: the new evidence weakens the earlier belief and the freshness trend flips from stable to weakening, while the world fact is unchanged.

    “After session 3, the consolidation engine refines the existing observation: the new evidence weakens the earlier belief and the freshness trend flips from stable to weakening, while the world fact is unchanged.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Study design and conductnone given
    § Ethics Statement

    All evaluation was conducted on publicly available benchmarks, and no personal data was collected.

    “All evaluation was conducted on publicly available benchmarks, and no personal data was collected.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premiseown data
    § 6.4 Qualitative Case Study

    In a three-session interaction, Retain in session 1 creates a world fact, an experience fact, and updates the observation for the user-entity.

    “Retain in session 1 creates a world fact (team rewrite in Rust), an experience fact (user began learning Rust), and updates the observation for the user-entity.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationnone given
    § Broader Impact Statement

    The open-source release allows the community to audit, extend, and improve safety mechanisms.

    “The open-source release allows the community to audit, extend, and improve safety mechanisms.”
    Quote in the paperNot a substantial claim
  • Classified as probably not a substantial claim.

    Premisenone given
    § Ethics Statement

    HINDSIGHT stores and organizes information from user conversations in persistent memory banks.

    “HINDSIGHT stores and organizes information from user conversations in persistent memory banks.”
    Quote in the paperSubstantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Interpretationnone given
    § 4.3

    Avoiding a separate vector store removes a class of consistency bugs and keeps deployment to a single connection string, backup, and monitoring target.

    “Avoiding a separate vector store removes a class of consistency bugs and keeps deployment to a single connection string, backup, and monitoring target.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Interpretationnone given
    § Ethics Statement

    HINDSIGHT's opinion formation mechanism reflects patterns in the data it processes and may amplify biases present in the input.

    “The opinion formation mechanism reflects patterns in the data it processes and may amplify biases present in the input.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationreasoning
    § 5

    This shows the epistemic separation that the four-network design provides.

    “This shows the epistemic separation that the four-network design provides.”
    Quote in the paperNot a substantial claim
  • May combine two claims.

    Interpretationreasoning
    § 4.2

    Reflect adds one LLM generation call on top of recall, so end-to-end query latency is driven primarily by the backbone model's inference speed.

    “Reflect adds one LLM generation call on top of recall, so end-to-end query latency is driven primarily by the backbone model's inference speed.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationnone given
    § 5

    The interface shows which retrieval channels contributed to each result, along with RRF fusion scores and reranker outputs, making the multi-strategy recall pipeline transparent.

    “The interface shows which retrieval channels contributed to each result, along with RRF fusion scores and reranker outputs, making the multi-strategy recall pipeline transparent.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationreasoning
    § Ethics Statement

    HINDSIGHT's persistent memory raises privacy considerations, as the system retains personal details, preferences, and opinions over time.

    “This raises privacy considerations, as the system retains personal details, preferences, and opinions over time.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Interpretationnone given
    § 4.5

    Each memory bank is isolated with its own four-network structure and behavioral profile, so the system serves multiple agents concurrently without cross-contamination.

    “Each memory bank is isolated with its own four-network structure and behavioral profile, so the system serves multiple agents concurrently without cross-contamination.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premiseown data
    § Computed: evidence_span , evidence_count

    HINDSIGHT provides drop-in wrappers for existing LLM clients, so developers can add memory to an agent without changing their application code.

    “HINDSIGHT provides drop-in wrappers for existing LLM clients, so developers can add memory to an agent without changing their application code.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductown data
    § Limitations

    Performance on other languages has not been tested.

    “Performance on other languages has not been tested.”
    Quote in the paperNot a substantial claim
26 of 26
  • The paper relies on this without support.

    The benchmark results for HINDSIGHT and the compared systems on LongMemEval and LoCoMo are directly comparable and not confounded by differences in evaluation protocols, prompt engineering, or backbone model capabilities.

    “HINDSIGHT with a 20B open backbone beats full-context GPT-4o and prior systems.”
1 of 1

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • 20B model ties rather than outperforms GPT-4o in one category

    Minor

    The single-session assistant category is 94.6% for both the 20B model and full-context GPT-4o, contradicting the claim that the 20B model outperforms it on every category.

  • User action is classified as an agent experience

    Minor

    The experience network is defined as recording the agent's own actions, but the case study calls the user's beginning to learn Rust an experience fact.

  • PostgreSQL requirement conflicts with Oracle backend support

    Minor

    A supported Oracle backend with full feature parity contradicts the limitation's statement that the system requires PostgreSQL with pgvector.

3 of 3

Cites

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Authors
Latimer, C., Boschi, N., Neeser, A., Bartholomew, C., Srivastava, G., Wang, X., & Ramakrishnan, N.
Affiliations
Virginia Tech (US)
Venue
Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 3: System Demonstrations)
Published
2026
Pages
275-285
OpenAlex
W7166866500
Cited by
0
References
28
FWCI
0.00
Type
conference paper
Open access
Licence
cc-by
Locations
Annual Meeting of the Association for Computational Linguistics (ACL) (publishedVersion, cc-by)
Topics
  • Physical Sciences › Computer Science › Artificial Intelligence › AI-based Problem Solving and Planning
  • Physical Sciences › Computer Science › Artificial Intelligence › Natural Language Processing Techniques
  • Physical Sciences › Computer Science › Artificial Intelligence › Speech and dialogue systems
Keywords
memory retention, memory retrieval, reflection, large language models

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