# Engram Prior-Art Scan

*Dated 2026-08-12. This is an **engineering novelty read**, not legal advice. It is intended to feed a patent/whitepaper priority decision by identifying which claims sit in a clean lane and which are wholly or partly anticipated by existing work. A patent attorney and a formal search (USPTO/Google Patents/Espacenet) should confirm before filing. Where a claim is anticipated, this document says so plainly — the goal is honest scoping, not inflated novelty.*

## How to read this

Engram is an immutable, temporally-provenanced knowledge graph (tombstone-not-delete, supersede-not-overwrite; every node carries `created_at` + `superseded_at` + provenance). Over that graph it computes **geometry descriptors** `G = (centroid, covariance/ellipsoid, skeleton graph, membership weights)` in a joint embedding+graph space, and runs named operators (overlap, combine, distance, difference, analogy=Procrustes, traverse=geodesic) over them. A "self" is a reified geometry. Time-travel is a **query filter** (`created_at ≤ T < superseded_at`), not a transaction-log replay. "Self-occupation" reconstructs the self-geometry/knowledge-state as of `T`, locks it read-only, and converses with it with all post-`T` data masked.

The recurring pattern in the findings below: **every individual primitive is prior art.** Bitemporal reconstruction, memory streams, vector-symbolic composition, geometric KG operators, hindsight-leakage auditing, embedding drift detection — all exist and are well-published. Novelty, where it exists, lives in *specific integrated mechanisms*, and must be claimed narrowly against those primitives. Broad claims ("reasoning as geometry," "reconstruct what was known at T," "detect drift by distance") will be rejected on sight.

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## (a) Hindsight-free decision auditing via immutable temporal knowledge-state reconstruction + future-masked occupation

**Claim (restated narrowly).** A method for auditing a past decision by (1) *constructively reconstructing* the exact knowledge-state a decision-maker held at time `T` from an immutable, tombstone+supersede provenance graph (selecting nodes live-at-`T` via `created_at ≤ T < superseded_at`), (2) recomputing the derived concept/self geometry over only that live-at-`T` slice, and (3) presenting that reconstructed state read-only, with all post-`T` nodes masked, as the sole evidentiary basis for judging the decision — such that the reconstruction is tamper-evident *because* nothing is ever overwritten or deleted.

**Closest prior art.**
- **HindsightBench** (Aug 2026) — a *black-box behavioral audit protocol* that detects parametric hindsight in time-indexed LLM decision tasks by manipulating the *asserted date* in the prompt (Revealed/Date-only/Masked/Transplant arms) and measuring behavioral shift. It explicitly does **not** reconstruct a knowledge state from provenance; it does not require corpus access or logprobs. It also reports that *instructed forgetting fails* — a 52% performance gap vs. true ignorance. https://arxiv.org/abs/2607.18867
- **Agentic Time Machine** (Jun 2026) — wraps web tools with a *leakage filter* that blocks post-cutoff or answer-revealing content before it reaches the agent (for forecasting benchmarks). https://arxiv.org/pdf/2606.21013
- **Zep/Graphiti** — bitemporal KG memory that can answer "what was the user's plan in January?" via point-in-time recall over event-time + ingestion-time. https://arxiv.org/abs/2501.13956 , https://www.getzep.com/ai-agents/temporal-knowledge-graph/
- **Auditable clinical-AI provenance frameworks** — immutable, timestamped "source-to-decision" trails recording the exact evidence shown to a clinician, for FDA transparency/liability. https://pmc.ncbi.nlm.nih.gov/articles/PMC12913532/
- **Hindsight-bias clinical literature** — retrospective case-note review is critically distorted by outcome knowledge; reconstructing the decision-maker's past perspective is the known mitigation. https://www.researchgate.net/publication/330427526 , https://kevinmd.com/2026/03/how-hindsight-bias-distorts-clinical-medicine.html

**What is genuinely differentiated.** The primitives — bitemporal point-in-time recall (Zep), immutable evidence trails (clinical AI), hindsight-bias mitigation by perspective reconstruction (clinical psych), leakage filtering (Agentic Time Machine), hindsight auditing (HindsightBench) — are all taken. What appears *unclaimed* is the specific combination: **constructive knowledge-state reconstruction from an immutable tombstone+supersede graph, used as the affirmative evidentiary substrate for judging a decision**, where correctness of the future-mask is *guaranteed by the data model* (a node is either live-at-`T` or it is not) rather than by prompt instruction or a heuristic content filter. HindsightBench and Agentic Time Machine both operate on the *model's* contaminated parametric memory and fight leakage behaviorally/heuristically; Engram sidesteps parametric leakage by making the *evidence set itself* provably `T`-clean and then recomputing geometry over it. The tamper-evidence-by-construction angle (append-only provenance ⇒ the reconstruction cannot be silently backdated) is also not present in the behavioral-audit line.

**Scoped-claim recommendation.** Claim the *pipeline*, not the goal: "reconstructing a decision-maker's knowledge-state as of `T` by selecting live-at-`T` nodes from an append-only tombstone+supersede provenance graph and recomputing derived concept/self geometry over that slice, then serving it read-only with post-`T` nodes masked as the evidentiary basis for decision review." Anchor on (i) constructive reconstruction from immutable provenance (not prompt-based date assertion), (ii) mask-correctness guaranteed by the data model, (iii) recomputed *geometry* (not just fact recall) as the reconstructed state. Do **not** claim "hindsight-free auditing" broadly, "point-in-time recall," or "immutable audit log" — all taken.

**Verdict: PARTIALLY TAKEN** (the goal and every primitive are taken; the constructive-reconstruction-from-immutable-provenance-as-evidentiary-substrate integration looks clean if narrowly scoped).

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## (b) Drift detection via geodesic displacement of an anchored self-geometry

**Claim (restated narrowly).** A method that reifies an agent's "self" as a geometry descriptor with a *designated stable value-core anchor* and a mutable *periphery*, and classifies change by **decomposition**: extension of the periphery (core displacement ≈ 0) is scored as *growth*, whereas geodesic displacement of the *core* is scored as *corruption* — measured as geodesic distance between `self(now)` and the anchored `self(reference)` on the graph+embedding manifold.

**Closest prior art.**
- **Embedding / concept-drift detection** — mature field: distribution-distance of embeddings, per-label distributions (Drift Lens), K-core-distance from a dense "core" of baseline logic, growing average distance from baseline anchors as the drift signal. https://www.evidentlyai.com/blog/embedding-drift-detection , https://ieeexplore.ieee.org/iel7/9679833/9679835/09679880.pdf , https://www.sciencedirect.com/science/article/pii/S0925231225018624
- **Agent identity/goal-drift governance** — identity-hash functions over characteristic behavior for drift detection; "dominant" core persona preventing fragmentation; reflection-based long-term self-model evolution vs. short-term compensation. https://arxiv.org/pdf/2604.14717 (Layered Mutability) , https://www.researchgate.net/publication/397950116 (Agent Goal Drift in Stateful Systems)
- **Persistent Identity multi-anchor architecture** — explicit *anchors* for resilient agent identity/memory continuity. https://arxiv.org/pdf/2604.09588

**What is genuinely differentiated.** "Distance from an anchored baseline core = drift" is squarely prior art (K-core-distance, baseline-anchor distance growth). Agent-identity work already has *core-vs-drift* and *anchors*. What is not obviously present is the **core/periphery decomposition of drift into two distinct, oppositely-valenced outcomes on a reified self-*geometry*** — i.e., using a *geometric* self-model (centroid + covariance/ellipsoid + skeleton) where *growth* is formally "periphery ellipsoid expands while core centroid/anchor stays fixed" and *corruption* is "core centroid/anchor is geodesically displaced." Existing drift work treats all displacement as drift (bad); it does not carve legitimate growth from corruption via a *fixed value-core* on a self-geometry. The specific formalization — geodesic (graph-aware, non-Euclidean) displacement of a *pinned* value-core sub-geometry vs. free peripheral expansion — is the differentiator.

**Scoped-claim recommendation.** Claim "detecting agent value-corruption by measuring geodesic displacement of a *pinned value-core sub-geometry* of a reified self-geometry, while treating expansion of the peripheral geometry with a stationary core as non-corrupting growth." Emphasize (i) the self is a *geometry descriptor* with an explicitly designated immutable core anchor, (ii) growth vs. corruption is a *decomposition* (two signals), not a threshold on one distance, (iii) geodesic/graph-aware metric. Do **not** claim "drift detection by embedding distance" or "anchored baseline comparison" — taken.

**Verdict: PARTIALLY TAKEN** (distance-from-anchor drift is taken; the growth/corruption core-vs-periphery decomposition on a reified self-geometry is the narrow clean sliver — and it's the weakest/most crowded of the five).

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## (c) Reasoning as composable geometry operations over a persistent temporally-provenanced graph

**Claim (restated narrowly).** A reasoning method in which inference steps are *explicit, named, first-class operators* (overlap, combine, distance, difference, analogy=Procrustes alignment, traverse=geodesic) applied to geometry descriptors computed over a *persistent, immutable, temporally-provenanced* knowledge graph — such that each reasoning step is individually inspectable, logged with provenance, and *replayable* against a past graph state; as distinct from implicit, unnamed activation/attention transforms inside a neural net.

**Closest prior art.**
- **Vector Symbolic Architectures / HRR / SDM** (Plate, Kanerva) — the canonical "algebra over vectors": binding, bundling/superposition, permutation, similarity; explicitly compositional/symbolic reasoning via vector operations. This is the strongest prior art for "named composable operators over vectors." https://www.emergentmind.com/topics/holographic-reduced-representations-hrrs , https://arxiv.org/pdf/2512.14709 (Attention as Binding)
- **Geometric KG query embeddings (Query2Box-lineage)** — reasoning as *named geometric operators* (projection, intersection) over box/region embeddings; geometric multi-hop reasoning; geometry-interaction KG embeddings. https://arxiv.org/html/2505.12369v2 , https://ojs.aaai.org/index.php/AAAI/article/view/20491/20250
- **Geometry-of-reasoning / embedding-space reasoning** — CoT as trajectories/flows in representation space; vector algebra + manifold geometry for deduction/induction/analogy. https://arxiv.org/abs/2510.09782 , https://arxiv.org/pdf/2504.02018
- **Riemannian knowledge manifolds** — geodesics as shortest semantic paths with a convergent geodesic solver. https://arxiv.org/html/2606.05907v2
- **Neuro-symbolic propose-verify** — explicit symbolic operations + solver verification.

**What is genuinely differentiated.** "Reasoning as composable vector/geometry operations" is *thoroughly* prior art — VSA/HRR own the compositional-operator framing; Query2Box owns named geometric operators (projection/intersection) for KG query answering; geodesic traversal over semantic manifolds is published. The individual operators (overlap≈intersection, distance, geodesic-traverse, Procrustes-analogy) each exist. The candidate differentiator is *not* any operator and *not* "geometry as reasoning" — it is the **coupling of the operator calculus to the immutable temporal-provenance substrate**: every operator input is a live-at-`T` geometry, every step is provenance-stamped, and the whole derivation is *replayable against a reconstructed past graph state* (i.e., operator-level temporal reproducibility + auditability). VSA/Query2Box run over static/atemporal embedding stores with no provenance and no time-travel; geometry-of-reasoning work is about a neural net's *internal* trajectory, not an external audited calculus. So the calculus itself is taken; "an *auditable, replayable* geometry calculus whose operands are temporally-reconstructed geometries" is the narrow lane.

**Scoped-claim recommendation.** Do **not** claim a "calculus of thought," "reasoning as geometry," or any specific operator (overlap/difference/geodesic/Procrustes) — all taken. Claim only the integration: "an audit trail in which each named geometric reasoning operator is provenance-stamped and its operands are geometry descriptors reconstructed from an immutable temporal graph as-of a query time, enabling deterministic replay of a reasoning derivation against a past knowledge-state." The defensible novelty is *temporal reproducibility + provenance of the operator chain*, not the operators.

**Verdict: TAKEN** (as "reasoning as composable geometry ops" — VSA/HRR + Query2Box + geometry-of-reasoning fully occupy it). Only the *auditable/replayable-over-immutable-temporal-substrate* framing survives, and it survives as a thin sliver of (a)/(e), not as an independent claim.

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## (d) Self-occupation with engineered future-masking

**Claim (restated narrowly).** A method for reasoning *as* a past self: reconstruct the self-geometry and knowledge-state as of `T` from the immutable provenance graph, *rigorously enforce the `created_at ≤ T` cut at the data layer* (all post-`T` nodes structurally excluded, not instructed-away), lock the reconstruction read-only, and drive a conversational/reasoning session that is provably uncontaminated by hindsight — the mask being a property of the substrate, not of a prompt or the model's willingness to "forget."

**Closest prior art.**
- **HindsightBench** — establishes the *problem* rigorously and shows that prompt-level "pretend it's `T`" fails badly (instructed forgetting ≠ ignorance; 52% gap; date assertions obeyed but hindsight still leaks). This is the strongest adjacent art and, helpfully, *motivates* Engram's substrate-level approach rather than anticipating it. https://arxiv.org/abs/2607.18867
- **Agentic Time Machine** — closest *mechanism*: a leakage filter blocking post-cutoff content before it reaches the agent. But it filters *tool outputs* heuristically for a forecasting benchmark; it does not reconstruct and occupy a *reified past self/knowledge-state*. https://arxiv.org/pdf/2606.21013
- **Causal Agent Replay** — counterfactual replay/attribution of agent failures (replay, but not future-masked past-self occupation). https://arxiv.org/abs/2606.08275
- **Chronologically-consistent pretraining / counterfactual-anchored decoding / forget-retain logit adjustment** — model-internal mitigations of parametric leakage (named in HindsightBench). Different layer entirely.

**What is genuinely differentiated.** The field is actively fighting hindsight leakage at the *model* layer (pretraining, decoding, logit surgery) and at the *tool-output* layer (heuristic leakage filters). Engram's move is orthogonal and, per HindsightBench's own findings, addresses the failure mode the field just documented: **enforce the cut at the evidence/data layer via an immutable time-indexed graph, so the "past self" is a reconstructed read-only geometry whose accessible universe is exactly the live-at-`T` slice.** No source found reconstructs a *reified self-geometry* as of `T` and *converses with it* as a first-class object. The differentiators: (i) the masked entity is a *reconstructed self*, not just filtered context; (ii) mask correctness is structural (a node's `created_at` either satisfies the cut or the node is absent) rather than heuristic/instructed; (iii) it is tamper-evident via append-only provenance. Note the residual honesty caveat: if the *underlying LLM* used for the conversation has parametric hindsight, Engram's substrate-clean evidence does not fully neutralize it — the claim must be about the *evidence/state* being `T`-clean, which is the part Engram genuinely controls.

**Scoped-claim recommendation.** Claim "reconstructing a reified agent self-geometry and knowledge-state as-of `T` from an append-only temporal provenance graph and conducting a read-only reasoning/conversation session over it in which the accessible node universe is structurally restricted to the live-at-`T` slice (data-layer future-masking), yielding a `T`-clean evidentiary state." Lean on *structural* (data-model-guaranteed) masking vs. *instructed/heuristic* masking, and on the *reified-past-self* object. Explicitly scope to the evidence-state cleanliness (not a claim that the LLM has zero parametric leakage). Do **not** claim "prevent hindsight in LLMs" or "leakage filtering" broadly.

**Verdict: CLEAN LANE** (narrowly — data-layer/structural future-masking over a *reconstructed reified past self* is not occupied; adjacent art is behavioral-audit, tool-output filtering, or model-internal mitigation. This is the strongest of the five, precisely because HindsightBench shows the prompt-level approach fails and no one is doing substrate-level self-reconstruction).

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## (e) Query→geometry temporal reconstruction with NO transaction logs

**Claim (restated narrowly).** Reconstructing a past knowledge-state as a *query-time filter* over immutable, per-node timestamped provenance (`created_at ≤ T < superseded_at`) followed by *recomputation of the geometry descriptors* over that slice — with **no event/transaction log and no periodic snapshots**; the immutable per-node provenance *is* the temporal record, and derived geometry is recomputed rather than stored/replayed.

**Closest prior art.**
- **Bitemporal databases (XTDB, et al.) / event sourcing** — "as-of" point-in-time queries over valid-time + transaction-time; immutability as audit log. Critically, XTDB describes reading bitemporal data as a process *"similar to event sourcing… playing through the history… in reverse system-time order"* — i.e., the mainstream bitemporal model *is* replay/reconstruction-through-history. https://v1-docs.xtdb.com/concepts/bitemporality/ , https://www.juxt.pro/blog/value-of-bitemporality/
- **Zep/Graphiti** — bitemporal (event-time T + ingestion-time T′) fact validity + supersession chains; point-in-time recall. https://arxiv.org/abs/2501.13956
- **TKG reasoning frameworks / ElephantBroker-class runtimes** — "immutable fact store, all temporal weighting applied at query time; facts created after the query timestamp excluded, facts superseded after query timestamp treated as current; invalidate by writing `t_invalid` rather than delete." This is *very* close to Engram's filter and supersede/tombstone semantics. https://www.emergentmind.com/topics/temporal-knowledge-graph-reasoning-tkgr , https://arxiv.org/pdf/2603.25097
- **Numerous bitemporal/immutable-DB patents** (point-in-time reconstruction, retroactive/historical transactions). e.g. US 11,935,046; US 8,812,512 (via USPTO search) — a patent attorney must clear these.

**What is genuinely differentiated.** The *temporal filter* (created-before, superseded-after) and *tombstone-not-delete / supersede-not-overwrite* are **standard bitemporal KG practice** — Zep and the TKGR frameworks describe almost exactly this. So the reconstruction-by-filter primitive is TAKEN, and "immutable provenance instead of a mutable audit log" is TAKEN (that's the bitemporal value prop). The only thing that is *not* standard: what gets reconstructed is not just a set of *facts/edges* but a set of **derived geometry descriptors (centroid/covariance/skeleton/membership) recomputed over the live-at-`T` slice** — i.e., recompute-geometry-on-read rather than store-and-replay. Bitemporal DBs reconstruct *records*; Engram reconstructs *derived manifold structure*. The "no transaction log / no snapshot — provenance IS the temporal record, geometry is recomputed" framing is a design stance that is defensible only if paired with the *geometry recomputation*; on its own it is indistinguishable from XTDB/Zep.

**Scoped-claim recommendation.** Do **not** claim bitemporal reconstruction, "as-of" queries, tombstone/supersede, or "immutable provenance as audit record" — all squarely taken (Zep, XTDB, TKGR, patents). Claim only: "reconstructing a *derived geometry descriptor set* (centroid/covariance/skeleton/membership) for a past knowledge-state by recomputing it on-read over the live-at-`T` node slice, without storing per-`T` geometry snapshots or a geometry-mutation log." The novelty is *geometry-recompute-on-read over a bitemporal slice*, not the slice.

**Verdict: TAKEN** (as "query-filter temporal reconstruction over immutable provenance" — Zep + XTDB + TKGR own it outright). Only "recompute *derived geometry* on-read, snapshot-free" survives, and it is really a facet of (c)/(a) rather than an independent claim.

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## Summary

| Claim | Verdict | Narrowest defensible (clean-lane) framing |
|---|---|---|
| **(a)** Hindsight-free decision auditing via reconstructed knowledge-state + future-masked occupation | **PARTIALLY TAKEN** | Constructive knowledge-state reconstruction from an *append-only tombstone+supersede* graph, used as the *affirmative evidentiary substrate* for decision review, with mask-correctness guaranteed by the data model and tamper-evidence by construction — not prompt/date-assertion (cf. HindsightBench) and not tool-output filtering (cf. Agentic Time Machine). |
| **(b)** Drift as geodesic displacement of anchored self-geometry | **PARTIALLY TAKEN** | Growth-vs-corruption *decomposition* of change on a reified self-*geometry* via geodesic displacement of a *pinned value-core sub-geometry* vs. free peripheral-ellipsoid expansion. (Crowded; weakest lane.) |
| **(c)** Reasoning as composable geometry ops over a temporal graph | **TAKEN** | Only survivor: *provenance-stamped, replayable* operator chain whose operands are geometries reconstructed as-of a query time (temporal reproducibility of the derivation) — never the operators or "geometry as reasoning" themselves. |
| **(d)** Self-occupation with engineered future-masking | **CLEAN LANE** (narrow) | Reconstruct a *reified past self-geometry* and converse with it read-only, with the accessible node universe *structurally* restricted to the live-at-`T` slice (data-layer masking) — not instructed forgetting (which HindsightBench shows fails) and not heuristic content filtering. |
| **(e)** Query→geometry temporal reconstruction, no transaction logs | **TAKEN** | Only survivor: recompute *derived geometry descriptors* on-read over the live-at-`T` slice, snapshot-free — never the bitemporal filter, tombstone/supersede, or "immutable provenance as record," all of which Zep/XTDB/TKGR own. |

## Overall posture

**Broad claims over primitives will be rejected.** Each of the five candidate claims decomposes into (i) a primitive that is unambiguously prior art and (ii), in three of five cases, a thin integrated mechanism that appears unclaimed. The prior art is strong and specific: Zep/Graphiti and XTDB own bitemporal point-in-time reconstruction and supersession (kills the broad reads of (a) and (e)); VSA/HRR and Query2Box own composable geometric/symbolic operators (kills the broad read of (c)); embedding concept-drift and agent-identity-anchor work own distance-from-baseline drift (kills the broad read of (b)); and HindsightBench + Agentic Time Machine own hindsight *auditing* and *leakage filtering* (bound (a) and (d)).

**Novelty lives in the specific integrated mechanisms, narrowly scoped.** The two genuinely defensible ideas are: **(d) substrate-level future-masking of a reconstructed, reified *past self*** — which is the strongest, and is *strengthened* by HindsightBench's finding that the prompt-level approach everyone else uses fails by ~52%; and **(a) constructive knowledge-state reconstruction from immutable provenance as the affirmative evidentiary basis for decision auditing**, distinct from behavioral probing. The unifying, defensible thread across (a)/(d)/(c)/(e) is *structural guarantee by the immutable data model* — the future-mask, the tamper-evidence, and the operator-chain replayability are all properties of the append-only substrate rather than of prompts, heuristics, or model cooperation. That "guaranteed-by-construction" framing is the honest core of any priority filing. Claims (c) and (e) should be folded in as *facets* (auditable/replayable geometry over reconstructed slices) rather than filed as standalone claims, and (b) should be filed only if the core/periphery decomposition can be made rigorous, since the surrounding drift-detection art is dense.

*Caveats for the filing team: (1) this scan covered academic/product/blog prior art via web search, not a formal patent search — several bitemporal/immutable-DB patents surfaced (e.g. US 11,935,046; US 8,812,512) and must be cleared on Google Patents/Espacenet/USPTO. (2) Claim (d)'s guarantee is that the *evidence-state* is `T`-clean; it does not by itself neutralize parametric hindsight in whatever LLM reasons over that state — scope the language accordingly. (3) Dates on several 2606–2607 arXiv preprints are very recent; confirm publication precedence relative to Engram's earliest documented conception date.*