Datacron

Datacron

Local MCP server to query and maintain a Markdown vault from Claude, Codex, Gemini, or

another stdio MCP client, without sending the whole vault into the context.

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What can you do with Datacron?

Recover project context, prepare for a conversation, and keep track of commitments. Datacron gives your assistant durable memory in readable, editable Markdown. Your notes remain usable independently of the client you choose.

Offline library: build a browsable Markdown library for Obsidian or another local reader, with a home page and topic indexes. Review proposed rewrites, splits and archives before changing the source vault. See the offline library guide and the 2026.0913.02 release notes.

The assistant orchestrates these requests using the available tools and granted permissions. A shared protocol guides reading, people updates, and write verification. Ambiguous identities require clarification; storing a deadline does not schedule a reminder. Explore daily follow-up.

Start here: install · first session · user guide · MCP reference · privacy.

Installation

Windows: one double-click installer

The easiest way on Windows: download Datacron-Setup.exe from the latest Release, double-click it, and pick your vault. No Python, no terminal, no administrator rights; Datacron registers itself with your AI clients automatically. Full guide: Windows installation.

Python: from PyPI

python -m pip install datacron

datacron setup

From source

From a clone of the repository:

python -m pip install -e ".[dev]"

Or, to install only the application:

python -m pip install -e .

Runtime prerequisites:

• Python 3.11+
• ripgrep available on the PATH for search_regex; without it that tool falls back to a slower scan of indexed chunk bodies
• a folder of Markdown notes
• a supported stdio MCP client, such as Claude Desktop, Codex CLI, or Gemini CLI

First session

1. Choose your notes folder with the installer or datacron setup.
2. Reconnect Datacron in your MCP client to load the tools and instructions. The Claude Desktop chat does not present the server instructions: paste the session start line printed by setup into your Claude preferences (see setup).
3. Ask: "Find the notes for my project and summarize its status with sources."

For memory sessions, session_context returns bounded context and the shared protocol. prepare_follow_up prepares sourced updates; existing writers apply them according to permissions. get_follow_up retrieves the latest structured revisions. Existing prose notes remain readable and are not automatically converted.

The server operates locally. Your client may send returned excerpts to its model provider; see privacy and security.

For cached session contracts, archive ranking, resumable write tracking and conversation evaluation, see daily workflow improvements.

Quick start

The easy path - one command detects your AI clients, initializes the vault, indexes it, and registers Datacron everywhere:

datacron setup            # interactive; add --yes for all defaults

See the installation guide for options (--client, --scope, writing, durability). Or step by step:

datacron init /path/to/vault

datacron index --vault /path/to/vault datacron status --vault /path/to/vault datacron mcp install --client claude-desktop --vault /path/to/vault

The mcp install subcommand above is dedicated to Claude Desktop. For Codex CLI, Gemini CLI, Antigravity, LM Studio, Cursor, and the other clients, use multi-client setup with datacron setup --client or auto-detection with --client all.

Add to LM Studio

LM Studio 0.3.17+ has one user configuration and no project scope. The preferred command is:

datacron setup --yes --vault "VAULT_PATH" --client lmstudio --scope user

For a Python installation where datacron-mcp is on PATH, the equivalent read-only configuration can also be imported with this official deeplink:

Add to LM Studio

The link imports this example. Open LM Studio's MCP editor and replace both placeholders before starting the server:

{

"mcpServers": { "datacron": { "command": "datacron-mcp", "args": [], "env": { "DATACRON_VAULT_ROOT": " ", "DATACRON_READ_PATHS": " ", "DATACRON_DURABILITY": "best-effort" } } } }

The example does not enable write tools. CLI setup is safer for packaged installations because it writes the actual executable path automatically.

Restart the configured client or clients after installation.

To run the server manually:

datacron mcp serve --vault /path/to/vault

The direct script entry used by the installer is also available:

datacron-mcp

datacron-mcp reads the vault from DATACRON_VAULT_ROOT.

Configuration

datacron init creates .datacron/VAULT.yaml. That file can carry vault-local configuration, notably query expansion:

query_expansion:

supervision: [monitoring] sauvegarde: [backup] restauration: [restore] chiffrement: [encryption] sécurité: [security] validité: [validity] certificat: [certificate]

Useful environment variables:

Path lists use the OS separator (: on Unix, ; on Windows).

Writing

Writes are deliberately OFF by default. Without DATACRON_WRITE_PATHS, write tools return a clear error and create no file.

To enable writing to a specific subfolder:

$env:DATACRON_VAULT_ROOT = "C:\Notes"

$env:DATACRON_READ_PATHS = "C:\Notes" $env:DATACRON_WRITE_PATHS = "C:\Notes\_memory" datacron mcp serve --vault C:\Notes

datacron setup can also apply the allowlist machine-wide (user environment variable, opt-in) so every MCP client inherits it; default: _memory, _drafts, _journal. See the setup guide.

Available write tools:

• create_note_ai: creates a typed Markdown note, without overwrite.
• append_journal: adds an entry under a heading of an existing note.
• set_frontmatter: updates lifecycle fields, the rejected options list, and the monotone last_id counter without modifying the Markdown body.
• patch_note_preamble: replaces or removes the Markdown preamble before the first recognized Markdown heading (ATX or Setext), with mandatory CAS control.
• patch_note_section: replaces the content under an existing heading with CAS control.
• delete_note_section: explicitly deletes an H2-H6 section (ATX or Setext) and its subtree.
• rename_note_section: renames only the title of an H2-H6 section (ATX or Setext).
• move_note_section: previews or commits an exact H2-H6 subtree move within a note, with mandatory CAS.
• revert_note: restores the exact bytes of a version kept in history.
• apply_organization_manifest: validates and then applies a local content-addressed bundle after confirmation bound to the exact admitted organization pre-state.

Guarantees:

• strict note confinement within DATACRON_WRITE_PATHS; organization-batch note sources and targets must also stay inside the unchanged live organization.scope and pass the live note-admission policy, including exclusions
• two internal exact-CAS targets for an organization batch: .datacron/VAULT.yaml, only to change the top-level organization mapping without changing organization.scope, and .datacron/ulids.json, only when Datacron derives the key migration required by a move_replace_exact
• atomic overwrite via temporary file + os.replace
• content-addressed history before modifying an existing note
• synchronous reconcile() after a normal write; immediate searchability is guaranteed only when reconciliation succeeds
• local audit log
• for an organization manifest: crash-consistent recovery and atomic replacement of each file; simultaneous visibility across several paths is not guaranteed

Concurrent multi-machine mode is not supported for writes: keep a single-writer rule on the vault.

For apply_organization_manifest, also stop every other Datacron client and server during the maintenance window. Before applying, keep a verified byte-exact backup outside the vault of the affected notes and t