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CPersona Documentation

CPersona is an MCP server. It gives Claude — or any MCP-capable agent — memory that survives across sessions.

Memories are kept in one local SQLite file. Recall searches them three ways (vector, FTS5, keyword) and fuses the results by rank or by relative score.

The server has zero LLM dependency: it never calls a generative model. Two things that does not mean:

  • It is not always free. EMBEDDING_MODE=api bills every embedding request against an endpoint that defaults to OpenAI's. http mode, pointed at an embedding server you run, does not.
  • It is not identical everywhere. Recall is deterministic once the quality gate is calibrated. Calibration samples your corpus at random, so two installs holding the same data can settle on different gates.

Applies to: CPersona 2.5.x. This site is the canonical documentation. If the README or the bundled skill disagrees with a page here, this site wins, and the disagreement is a bug worth reporting.

Moving to 2.6? 2.6.0 is the current release. Upgrading from 2.5 to 2.6 takes a 2.5.x store there in one pass.

Where to go

  • Getting Started

    Install it, register it with an MCP client, and verify the connection.

    Getting Started

  • Architecture

    Where memories are stored, how the three retrievers search them, and what the fusion → gate → reverse pipeline does. With diagrams.

    Architecture

  • Tools

    Every tool, grouped by purpose. Tools that do not behave the way their name suggests link to the contract that explains them.

    Tools

  • Behavior Contracts

    Behaviours you can rely on. We treat a change to any of them as a bug.

    Behavior Contracts

  • Configuration

    Every environment variable and its default, and what the HTTP transport requires before it will answer.

    Configuration

  • Operations Runbook

    Backup, degradation detection, the order to tune recall in, Japanese corpora, maintenance cadence.

    Operations Runbook

  • FAQ

    Short answers to the questions operators ask most, each linking to the page with the full detail.

    FAQ

  • Quality Assurance

    How a release is gated: audit rounds, the bug ledger, structural CI gates, mutation proof.

    Quality Assurance

Design notes and standards

Two kinds of page sit below the guides. They answer different questions.

Project standards define what a release, an audit report, or a generated policy block must look like. Other projects can adopt them.

  • Release lifecycle standard — tier definitions (Stable / Current), the risk-triggered pre-release ladder, and support windows. What this repository actually runs is in SUPPORT.md.
  • SuperAuditor standard — how a client pulls findings from a server: the severity vocabulary, and what a cap means. It deliberately says nothing about which problems a server should detect.
  • Policy block standard — how a project's skill writes a marker-wrapped policy block into the file an agent loads every session (CLAUDE.md, AGENTS.md, …), and why a skill alone cannot guarantee the block is there.

Where it is going. The roadmap records what each release line is for, what it may break, and which measured problem each planned feature answers. It covers three axes: release lines, runtime and scale, support tiers. It describes intent, not delivery dates. What has shipped is in the release notes and SUPPORT.md.

The 2.6 line has its own page, Reliable Recall: the recall loop that iterates inside a single call, the cue contract, the prior function, the reconstruction exit and its count window, the failure taxonomy, and what counts as done.

Design notes record how one behaviour was decided, including the routes that were rejected. They are point-in-time records. Where a note and the guides disagree, the guides win.

  • Per-client capabilities (ACL) — named bearer tokens, per-agent read/write grants, deny-by-default.
  • OAuth support — resource-server metadata, token verification, the three routes that were weighed, and where the per-subject boundary falls.
  • Server-served operating context — distributing operator instructions to every connected MCP client.
  • Declared session identity — why one process is not one session under streamable HTTP, and which process-global state session_key splits apart.
  • Recorded access origin — recording the observed caller on each stored row, for the paths where agent_id names nobody.
  • Recall preview tier — preview truncation and the get_contents expansion path.
  • Contiguous embedding index — moving the vector scan off SQLite rows and onto a contiguous sidecar file. The answers do not change.
  • Reach and recency in the scan window — why a wider vector scan window loses recent answers, and the second ranked list that widens it without giving up the recency preference.
  • Reach, recency and the far vote — three measurements in one account, what each establishes, and the plan for pricing the far vote in the 2.6 line.
  • Adaptive fusion — for the 2.6 line: reserving each retriever a share of the pool, removing the rank cut from the pool-size gate, and the pre-registered comparison between a measured lexical weight now and a conditional-evidence fusion mode later.
  • Embedding degradation advisory — how recall reports a dead embedding layer instead of quietly getting worse.

Research notes

What the 2.6 design pages rest on: derivations, measurements, and refutations, written to be checked rather than trusted. The notes are published with the 2.6 documentation, and its overview explains the status vocabulary.

  • Adaptive fusion, a derivation — combines the retrieval arms through the probability that each score would be exceeded by chance. The rule has a closed form for each row's influence, and today's reciprocal rank fusion is its limiting case.
  • Calibration and the admission floor — three calibration methods on seven tasks where recall was losing. The floor is not the cause. The null distribution came from the wrong population of pairs. Small corpora starve the dense arm.
  • Where the loss is, a frozen-stage replay — every stage of the Track B path scored on frozen embeddings, three models, pinned to the live pipeline. The pure-ranking tasks lose at fusion, Gorilla at admission, EPBench at the gate. QASPER's gain comes from replenishment.
  • Two arms, one decision — what a fusion rule must know to avoid those losses. Not per-arm calibration: how much the lexical arm adds given the dense score. A joint density ratio supplies that without a fitted weight, and the note derives closed forms for starvation, gate extinction, and reservation.

The three memory types

  • Declarative — individual facts, decisions, rules (store / recall).
  • Episodic — session summaries (archive_episode), which also drive the episode boundary penalty.
  • Profile — accumulated user/project attributes (update_profile), with a scoring caveat worth knowing.

For AI agents reading this site

A machine-readable index of these pages is published at llms.txt. The bundled cpersona-memory skill teaches an agent the day-to-day store / recall / archive workflow and links back here for the canonical detail.

Sponsorship

CPersona is MIT-licensed and will stay that way. If it has become useful and you want the work to continue, the sponsorship page explains what sponsoring does and does not buy. It also lists the ways to help that cost nothing.