PLUR

1. Executive Summary

PLUR is a local-first shared memory for coding agents — Apache-2.0, 927 commits between 19 March and 8 September 2026 by thirteen authors, 66,632 lines of TypeScript outside tests across ten packages, beside 82,289 lines of tests holding 4,893 cases. The screen found three auto-run surfaces — two plugin manifests and a hooks directory — one build-time execution point and twelve unpinned surfaces; nothing was installed or run, and the read was made from a full clone. The store is plain files under ~/.plur, with engrams.yaml as the source of truth and SQLite, PGLite or Postgres attachable as an index the code describes as a cache rather than truth.

Six of seven marks, and the one that decides the character of the system is trust_state. An engram carries a commitment — exploring, leaning, decided, locked or draft — and skipForApproval returns true for draft (packages/core/src/inject.ts:172-173), which the injection loop uses to skip that engram in both its selection pass and its spreading-activation pass (:657, :697). A draft is still retrievable and still searchable; it just never reaches the model's context. The producer is agent-reachable: plur_learn takes a commitment argument that flows into the persisted shape, and feedback cannot launder the value because the transition function returns an unrecognised state untouched.

The other five. bitemporal on a temporal block the schema calls bi-temporal anchoring, with valid_from and valid_until beside learned_at and ingested_at, filtered by the retrieval path and the injection gate independently of the record timestamps. scope_enforced on a scope with two read-side predicates, the stricter of which is exact membership carrying an explicit rule in the source that an empty permitted list must match nothing — "a principal with no permitted scopes must see nothing. NEVER treat an empty list as 'no filter'". audit_log on an append-only monthly JSONL of twenty-one mutation event types, fsynced, in the store's own directory. human_review on a tension queue where a person confirms, dismisses or resolves a detected contradiction and the loser is retired. negative_eval on three cases asserting a draft absent from a populated injection, one of them through spreading activation.

Four findings sit against the design. A retired engram cannot stop itself returning, on purpose. _hashDedup matches only active rows (packages/core/src/index.ts:1833), and the codebase frames that as a feature twice over — "its content hash cannot resurrect it" — with a committed test titled "retired engrams are excluded from dedup — new write creates new engram" asserting the new id differs (packages/core/test/reference-count.test.ts:149-155). That is a deliberate design choice and it is the reason tombstone is withheld. Nothing here can approve a draft. The schema comment points at a separate enterprise repository for the review-queue write sites, and the shipped dashboard is read-only, so draft is a one-way state in this tree. The direct correction path destroys what it replaces. _updateEngramReturning overwrites the row in place (:5923) with no history event and no version bump, while the two model-mediated paths both preserve the prior statement in a history event. The benchmark harness is not here. The README says the harness is published so every number can be reproduced, and names the separate repository that holds it six lines later; a commit in July removed 2,238 lines including the corpus importer from this tree.

2. Mental Model

A memory is a sentence the model wrote and a set of judgements about it. The statement is stored verbatim — the only rewriting on the main path strips tool-call envelope artifacts and derives an eighty-character summary. Everything else on the engram is metadata about that sentence: who asserted it, how it was arrived at, how sure the author is, when it holds, and who may see it.

Two independent gates decide what reaches the model. Status decides whether an engram is retrievable at all; retired ones are not. Commitment decides whether a retrievable engram may be injected; drafts are not. The separation is the design: a draft can be found, cited in a review and argued about without ever being presented to the model as something it knows.

Forgetting is a reference count. Each repeat of the same content increments a counter; forgetting decrements it, and only at zero does the engram retire — with its full text still in the file.

%% caption: the model authors a statement, a content hash absorbs a repeat against active engrams only, and the engram lands in engrams.yaml with an audit event appended; retrieval filters on status, scope and validity while injection additionally skips drafts, and forgetting decrements a reference count that retires at zero without removing the row or blocking the same text being written again
flowchart TB
    AG["the model writes a statement<br/>plur_learn"]
    HASH{"content hash matches<br/>an ACTIVE engram?"}
    BUMP["reference count incremented,<br/>duplicate recorded"]
    NEW["new engram: scope, commitment,<br/>validity window, attribution"]
    YAML[("engrams.yaml — the source of truth")]
    HIST[("history/YYYY-MM.jsonl<br/>append-only, fsynced,<br/>never synced to a team store")]
    IDX[("optional index:<br/>SQLite, PGLite or Postgres<br/>a cache, not truth")]
    READ["retrieval: BM25, optionally<br/>fused with a local embedder"]
    F1{"status active?<br/>scope visible?<br/>currently valid?"}
    OUT["returned to a search"]
    F2{"commitment is draft?"}
    INJ["injected into context"]
    HELD["retrievable, never injected —<br/>and nothing here can approve it"]
    FORGET["plur_forget: decrement"]
    RET["at zero: status retired,<br/>row and text remain"]
    AGAIN["the same text written again<br/>creates a NEW engram"]

    AG --> HASH
    HASH -- yes --> BUMP
    HASH -- no --> NEW
    NEW --> YAML
    NEW --> HIST
    YAML --> IDX
    YAML --> READ
    READ --> F1
    F1 --> OUT
    OUT --> F2
    F2 -- no --> INJ
    F2 -- yes --> HELD
    YAML --> FORGET
    FORGET --> RET
    RET --> AGAIN

3. Architecture

Ten packages. core (39,629 lines) holds the schema, the stores, retrieval, injection, feedback, tensions, packs and sync. cli (12,532) and mcp (5,625) are the two human and agent surfaces; dsh, claw, ui, migrate are smaller, and three Python packages adapt the store for Hermes and LangChain.

The storage layer is deliberately layered: YamlPrimaryStore reads and writes the whole engram array, and the indexed stores mirror it into a table whose data column holds the engram as JSON or JSONB with the queryable fields promoted into columns. The scope filter is pushed down into each of them rather than applied after loading.

Deployment and ergonomics

• What has to run: Node. Nothing else — BM25 needs no model, and the ONNX embedder is optional and local.
• Fully local and offline: yes on the default path; the batch-dedup and failure-report paths call a model.
• Hand-repairable: entirely. The store is YAML a person can read and edit, and the indexes rebuild from it.
• Install: npm packages per surface, plus plugin manifests for two agent runtimes.

4. Essential Implementation Paths

• Learn. packages/mcp/src/tools.ts:1125 sanitises the statement (:1245), checks the pin quota and calls into the core. Plur.learn (packages/core/src/index.ts:2850) asserts writability, resolves the validity window (:2858), takes the store lock, runs the content-hash dedup (:2901-2904), mints an id, builds the shape (:2948), appends (:3119), syncs the index (:3123), appends the history event (:3124-3129) and writes provenance.
• Dedup. _hashDedup (:1829-1838) matches on status === 'active' and the content hash; a hit increments the reference count instead of writing.
• Retrieve. packages/core/src/fts.ts:448-488 scores BM25 with k1 1.2 and b 0.75; packages/core/src/hybrid-search.ts:135-197 runs the lexical leg on a rewritten query and the embedding leg on the original, widening both limits, and merges by reciprocal rank at k=60 (:63-80).
• Filter. Plur._filterEngrams (:4777-4878) applies status (:4837), the scope allow-list (:4843-4844), a domain prefix, scope visibility (:4861), temporal validity (:4872) and a minimum strength.
• Inject. packages/core/src/inject.ts selects and spreads, skipping drafts at both stages (:657, :697) and expired engrams at :140-153.
• Correct. Three paths: _updateEngramReturning (:5905-5928) overwrites; plur_report_failure (:8020-8084) has a model rewrite a procedural statement and writes the old text into a procedure_evolved event with a version bump and a previous-version reference; the batch dedup (packages/core/src/learn-async.ts:237-300) records the old and new statement with the deciding model as the actor.
• Forget. Plur.forget (:6249) decrements the reference count and at zero sets status retired (:6427-6432), optionally rewriting the rationale, and appends a retirement event with the before and after counts.
• Adjudicate. packages/mcp/src/tools.ts:3880-3897 and packages/cli/src/commands/tensions.ts:113-129 confirm, dismiss or resolve a tension; a resolve retires the loser.

5. Memory Data Model

The engram schema is 553 lines of Zod (packages/core/src/schemas/engram.ts). Beyond the statement it carries: lineage (source, derivation count, pack, abstract, derived-from), classification (a knowledge type with a memory class and a cognitive level, a domain, tags), activation (retrieval and storage strength, frequency, last accessed), a relation block with broader, narrower, related, conflicts, supersedes and superseded-by, weighted associations, knowledge anchors, dual coding with an example and an analogy, provenance with an origin, a chain, a licence and a reserved signature whose algorithm the schema says is not yet specified, an attribution block naming the asserting runtime, model and tool, a claim class, feedback and usage counters, and optional temporal, episodic, exchange and insight blocks.

Temporal: learned_at, valid_from, valid_until and ingested_at beside created_at, updated_at and each source's stored_at. bitemporal earned.

Trust: commitment and status, both filtering. trust_state earned.

Scoping: a free-form scope with two predicates. scope_enforced earned.

Tombstone: withheld — see section 9.

A status value with no writer. The status enum admits candidate and dormant, and the schema says of them: "'dormant' and 'candidate' are NOT assigned by any code today" (:352-354), which a search confirms. The consequence is that plur_promote, a shipped MCP tool advertised as activating candidate engrams, has nothing this codebase can produce to act on. Separately candidates.yaml is allocated and synced with the sync module noting it has no in-core writer.

6. Retrieval Mechanics

BM25 with the standard constants over a rewritten lexical query, optionally fused with a local ONNX embedding search over the original query. Fusion is reciprocal rank at k=60, with the lexical leg fetching three times the limit and the embedding leg twice, widened to five and three times for queries the system classifies as aggregations.

There is no relevance threshold in either leg, and the code contains a comment that reasons as though there were one — treating an empty embedding result as meaning no neighbours cleared a threshold, when the embedding search returns the top N regardless of score and an empty result can only mean an empty corpus or an unavailable embedder. The fusion score is surfaced deliberately so that a caller can apply a cutoff.

Failure modes. The embedder being unavailable degrades to BM25 silently, which is the right default for a local-first tool. A draft is retrievable and uninjectable, so an agent that reads search results directly sees something the injector would have withheld. And the index stores are caches: a stale index is a stale answer, with the YAML still correct.

7. Write Mechanics

The model writes the sentence. No summariser stands between the agent's words and the file, which is the point of a store whose selling line is that memory is text you can read rather than weights you cannot. The regex-based ingest path captures verbatim groups; only the batch and failure-report paths put a model between input and storage, and both record what they replaced.

Repetition is a counter, not a duplicate. The same content within the same scope increments a reference count. Forgetting decrements it. That makes plur_forget a vote rather than a delete, which is defensible, and it means a single forget on a thrice-learned engram changes nothing visible.

What the correction story does not do. The path most likely to be used from a library — the direct update — replaces the statement with no record that it ever said anything else, while the two paths that need a model both preserve the prior text. The version and previous-version fields exist on the schema and only one of the three paths sets them.

Operational cost

• A write is a YAML rewrite of the array, an index upsert and a JSONL append.
• A read is BM25 in process, optionally an ONNX pass, no network.
• The audit history grows monthly and is never pruned or synced.

8. Agent Integration

43 MCP tools, of which about a dozen write. The model's path to memory is injection rather than a recall call — the injector selects, spreads activation over associations and assembles a block — with the draft gate and the validity gate applied inside that assembly.

The human surfaces are the CLI, the YAML file itself, and a dashboard that is read-only by design: one route renders and a single POST reveals a folder, documented as writing nothing and bound to loopback.

One naming issue is worth flagging for anyone reading the tool list: session end takes a parameter called engram suggestions and writes them straight through the learn path with no approval step.

9. Reliability, Safety, and Trust

Trust state — awarded. A discrete state that withholds from injection while leaving the engram retrievable, produced through an agent-facing argument, enforced inside the injector, and pinned by three tests. The caveat is substantial and belongs in the same paragraph: nothing in this repository lifts it. The schema points at a separate enterprise repository for the review-queue write sites, and the shipped dashboard cannot write. A draft written here stays a draft.

Bitemporal — awarded. Two axes with producers on each and independent filters on both the retrieval and the injection path, including an expiry that can be parsed from the statement text and is echoed back to the caller rather than applied silently.

Scope — awarded. Two predicates, one segment-aware so a project whose name shares a prefix with another is excluded rather than matched, and one exact membership whose empty case is documented in the source as a security rule and asserted by a test.

Audit log — awarded. Append-only, fsynced, twenty-one event types, in the store's own directory, with a reader tool. One property worth stating: the history directory is not in the sync path, so a store pushed to a team carries the engrams without the record of how they got there.

Human review — awarded. A person confirms, dismisses or resolves a contradiction and the resolution retires the loser. This is adjudication of memory content, and the dashboard is correctly not counted as it writes nothing.

Negative evaluation — awarded. Three draft-gate cases with positive controls in the same assertion, including one through spreading activation, plus scope and validity exclusions.

Tombstone — withheld, and it is a deliberate design decision rather than an omission. Retirement is soft: the row and the full statement stay in the file, which is the right choice for a store meant to be read by humans. But the content-hash dedup matches only active rows, so the retired text does not block its own re-assertion. The codebase states this twice as a benefit, and a committed test asserts that re-learning a forgotten statement produces a new engram with a new id. The mark asks for a record keyed on the value that a later write consults; here the record exists and the write path deliberately looks past it.

What the delete story promises and does not do. The tool table describes a retired memory as eventually pruned, and a comparison page describes erasure as a real file delete a user can watch happen. No pruning of retired engrams exists in the tree; the only deletion of an engram row is an outbox cleanup after a successful remote push. Erasure is a status flip, and a person who wants the text gone edits the YAML.

10. Tests, Evals, and Benchmarks

4,893 cases in 396 files and 82,289 lines against 66,632 lines of source, with dedicated adversarial, meta and fixture directories under the core package's tests. Exclusion assertions number 337, concentrated in named files for the draft gate, scope pushdown, read-side visibility, supersession, validity instants and the pinned quota.

The benchmark harness is in a different repository, and this one says so. The README's benchmark section opens by saying the harness is published so every number can be reproduced, and six lines later names plur-ai/plur-bench as the source of truth for every figure the project publishes. A commit on 8 July 2026 removed the in-repo harness — 2,238 lines across a runner, a per-question protocol, its tests and the LongMemEval corpus importer — and the benchmark/ directory now holds one file, a latency micro-benchmark for branch comparison. The data and result directories are gitignored, and the project's contributor notes say result JSONs are no longer committed here.

Two things follow, and both are the project's own words rather than an inference. The only measurement this tree can show is an n=30 fixture run reported at 80.0% R@5 in a dated benchmark document, against README headline figures of 92.2% to 97.6% at n=500. And a self-audit document in docs/reports/ states of an earlier figure: "The raw run artifact for the 86.7% / 93.3% measurement is not archived in this repository" and "the claim is widely propagated, the artifact is not." That document's own remediation instructions point at the runner and the result file the July commit deleted.

The honest summary for a reader: the harness is published, just not here, and nothing in this checkout reproduces a published number.

11. For Your Own Build

Steal

• Separate retrievable from injectable. A state that keeps an engram searchable while withholding it from the model's context is the cheapest review mechanism there is, and it is four lines in the injector.
• Enforce the gate in the injector, not in the caller. Every path that assembles context passes the same predicate, including the spreading-activation pass that is easy to forget.
• Make the empty grant match nothing, and write the reason in the source. The comment saying never to treat an empty permitted list as no filter is the kind that survives a refactor by someone who did not write it.
• Append the mutation history beside the store and fsync it. Twenty-one event types with an actor and a reason cost one append per write.
• Echo a parsed expiry back to the caller. Silently inferring a validity window from statement text would be a trap; saying what was inferred is not.
• Count references instead of deleting. A memory learned three times and forgotten once should not disappear.

Avoid

• A dedup that looks past what you retired. Whether that is right depends on whether forgetting means this was wrong or I do not need this now — the choice is defensible, but the two readings need different mechanisms and only one of them is built.
• A withholding state with no way to lift it in the same repository. A draft that nothing here can approve is a one-way door, and the pointer to another repository is not usable by a reader of this one.
• A correction path that overwrites without a record, beside two others that preserve it. The one most likely to be called from a library is the one that forgets.
• A status value nothing assigns, and a shipped tool whose whole purpose is to act on it.

Fit

Right if you want an agent's memory to be plain text you can read, diff and edit, shared across several MCP clients, with no service to run and no model required on the default path. The draft gate, the scope rules and the audit history are all well built. Wrong if you need a rejected statement to stay rejected, an in-repo way to approve what was drafted, or to reproduce the published retrieval numbers from this checkout.

12. Open Questions

• What approves a draft outside the enterprise repository? The gate is enforced here and the lift is not, which leaves the mark's most useful half elsewhere.
• Should retirement block re-assertion? The current answer is deliberate and tested; the alternative needs a second state meaning judged wrong rather than not needed.
• Will the direct update path gain a history event? The two model-mediated paths already write one, and the version fields exist on the schema.
• What removes a retired engram? The tool description promises pruning and nothing implements it.

Appendix: File Index

Searches recorded for the negative claims

rg -n "status\s*[:=]\s*'candidate'" --glob '*.ts' packages/*/src     # 0: declared and never assigned
rg -n "status\s*[:=]\s*'dormant'" --glob '*.ts' packages/*/src       # 1, a comment; no assignment
rg -i 'tombstone' --glob '*.ts' packages                             # 1, a test title about soft retirement
rg -i 'prune' --glob '*.ts' packages/*/src                           # no pruning of retired engrams
ls benchmark/                                                        # one file: micro.ts
ls benchmark/run.ts benchmark/results/baseline-main-hybrid.json      # both absent; the self-audit points at them
git show 19b74b5 --stat                                              # the harness removal: 2,238 lines

History

2026-09-08 — d005139e… — first reading, at the head of main, on a commit from the same day. Screened before anything was read: three auto-run surfaces (two plugin manifests and a hooks directory), one build-time execution point, twelve unpinned surfaces; nothing was installed or run, and the read was made from a full clone. Six marks. trust_state rests on a draft commitment enforced inside the injector at both its passes, with the caveat that nothing in this repository can approve one. bitemporal, scope_enforced, audit_log, human_review and negative_eval rest on the temporal block and its two independent filters, the segment-aware and exact-membership scope predicates, the fsynced monthly JSONL, the tension adjudication, and the three draft-gate exclusions with controls. tombstone is withheld on a decision rather than an omission: the dedup deliberately looks past retired rows and a committed test pins that. The benchmark position was verified rather than repeated — the harness was removed from this tree in 19b74b5 and lives in a separate repository the README names, so no published number is reproducible from this checkout, which the project's own self-audit document also states. The reading covers the engram schema, the write and dedup paths, retrieval and injection, the scope predicates, the history log and the tension queue; the packs and exchange subsystems, the sync outbox, the migration package and the Python adapters were treated as context.