Perseus Vault Codex

Persistent, encrypted, local-first memory for OpenAI Codex agents.

Codex never forgets. Perseus Vault gives your Codex agent persistent encrypted memory — so it remembers your project conventions, past decisions, and debugging context across every session.

License: MIT | Built for OpenAI Build Week — Developer Tools track

The problem

Every Codex session starts from zero. The agent re-learns your build commands, re-discovers your conventions, and re-derives the same architectural context you explained yesterday. Memory is the missing primitive for coding agents.

Existing memory stores don't fit a developer's machine: mem0 is cloud-dependent, cognee is Python-only with no encryption at rest, Letta manages memory but doesn't encrypt local storage, Chroma is a vector DB, not structured agent memory. None are single-binary, zero-infra, and encrypted.

Related MCP server: mcp-project-context-server

The answer

perseus-vault-codex is a tiny MCP server that wraps Perseus Vault — a single 12 MB binary, fully local, AES-256-GCM encrypted at rest, with FTS5 keyword + hybrid recall and no API keys, no cloud, no telemetry. Install it and any Codex session gains five memory tools:

Install

# 1. Install the wrapper (zero Python dependencies)
pip install perseus-vault-codex            # from PyPI, or from source (below)

# 2. Install the Perseus Vault binary (single static binary, no deps) and put it on PATH
#    https://github.com/Perseus-Computing-LLC/perseus-vault/releases

# 3. Register it with Codex (non-destructive; backs up your config)
perseus-vault-codex-setup

Install from source (works today, before the PyPI release):

git clone https://github.com/Perseus-Computing-LLC/perseus-vault-codex
cd perseus-vault-codex
pip install -e .
perseus-vault-codex-setup

That's it. On first run the server auto-creates an encrypted vault at ~/.perseus-vault/codex/memory.db — no config required.

Configure in Codex

perseus-vault-codex-setup writes this into ~/.codex/config.toml:

[mcp_servers.perseus-vault]
command = "perseus-vault-codex"
args = []

Restart Codex (or start a new session) and the five perseus_* tools are available. To enable perseus_reflect synthesis, expose your OpenAI key:

[mcp_servers.perseus-vault.env]
OPENAI_API_KEY = "sk-..."
OPENAI_MODEL = "gpt-5.6"

See examples/codex_config.toml for every option.

Example usage

Inside a Codex session:

you> Set up the project. First, check what you already know.

codex> [calls perseus_recall {"query": "project build and test conventions"}]
       I recall from a previous session:
       - This project formats with `ruff format` and lints with `ruff check`.
       - We chose SQLite + FTS5 over Postgres for the local dev store.
       Running `ruff check` before I start...

you> We just decided to switch auth to short-lived JWTs with refresh tokens in Redis.

codex> [calls perseus_remember {"category": "decision", "key": "auth",
        "text": "Auth uses short-lived JWTs; refresh tokens live in Redis."}]
       Remembered. I'll apply that convention going forward — including in
       future sessions.

Tomorrow, in a brand-new session, perseus_recall "auth" returns that decision. The context survived.

Try the demo

PERSEUS_VAULT_BIN=/path/to/perseus-vault python scripts/demo.py

It simulates two separate Codex sessions: session 1 learns three project facts and tears the vault process down completely; session 2 — a fresh process — recalls them, reflects on them, and reports encrypted status. Sample output is in docs/.

Architecture

Codex (GPT-5.6)  ──MCP stdio──▶  perseus-vault-codex  ──MCP stdio──▶  perseus-vault binary
                    5 tools        (this package)        55+ tools      SQLite+FTS5, AES-256-GCM

Two hops on purpose: Perseus Vault exposes 55+ low-level memory tools; this package collapses them into five verbs a coding agent can reason about, and the binary does the encrypted storage and retrieval. Full write-up: docs/architecture.md.

Benchmarks

Measured against the real perseus-vault binary (v2.17.0), encrypted at rest — full methodology and reproducible harness in benchmarks/:

• Recall is fast and accurate at scale. Seeding 10,000 developer memories, recall runs at p50 7 ms (p95 27 ms) with 5/5 recall@10 on distinctive needle memories (1,000-memory corpus: p50 1.3 ms). The recall hot path — what a Codex agent hits every task — stays in single/low-double-digit milliseconds.

• The engine scales to 1,000,000 memories. A separate 2× H100 validation (run #619, results/scale_1m_2xh100.json) embedded ~1M memories (995,562 persisted, 0 errors) and hit hybrid recall@5 = recall@10 = 1.00 over 2,000 semantic queries, at sub-second latency (p50 479 ms). This is an engine-scale result on GPU, not the laptop path — reported separately and honestly (keyword-only recall is near-zero on that semantic workload; hybrid carries it).

• Persistent memory cuts context tokens ~72%. Over a 30-session horizon, recalling the top-k relevant memories per task uses 110,493 fewer tokens (72.5% reduction) than re-priming each new session with the full project knowledge base — per-unit token costs measured with tiktoken against real vault recalls.

Every number is measured or explicitly labeled as a stated assumption; nothing is hardcoded. Reproduce with python benchmarks/bench_recall.py and python benchmarks/bench_token_savings.py.

How Codex was used

Codex was used during Build Week as an implementation and verification partner. In the final review session, it read the complete wrapper and its tests, ran the suite against the real perseus-vault 2.17.0 binary, exercised the two-session demo, and checked a unique marker was absent from the raw default database file. It also hardened stdout-EOF recovery in the subprocess client and added a regression test. Those are review-session contributions; this README does not attribute all pre-existing code to that session.

See SUBMISSION.md for the precise verification record and benchmark caveats.

Development

git clone https://github.com/Perseus-Computing-LLC/perseus-vault-codex
cd perseus-vault-codex
pip install -e ".[dev]"
pytest -q                                   # unit tests (no binary needed)
PERSEUS_VAULT_BIN=/path/to/perseus-vault pytest -q   # + integration tests

About

Built by Perseus Computing LLC. Perseus Vault is the only fully-local, encrypted memory store for AI agents, with existing integrations for Haystack, LangChain, LlamaIndex, CrewAI, Pydantic AI, and Google ADK. MIT licensed.