Argus Decision MCP

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Argus carries a consequential decision across conversations: the user-adopted prediction, what reality should show, when to return, and what actually happened. The result becomes context for the next judgment. Argus never scores the person or invents a verdict.

Part of Argus · web app at argus.voyage · MIT licensed.

What using it looks like

You talk normally. Argus offers to keep one testable thing, then brings it back when reality can answer.

2026-08-19
you    We're going with Postgres over DynamoDB — the join patterns kill us otherwise.

       ┌ Save this as a prediction?          (your host renders the form)
       │ "Postgres handles our join patterns without a read-replica through Q4"
       │ check by 2026-10-01
       └ accept as written · edit the wording or the date · decline

… six weeks later, in a different conversation …

2026-10-01
argus  One check is due — you saved this on 2026-08-19:
       "Postgres handles our join patterns without a read-replica through Q4"
       What actually happened?

you    We added a read replica in September. Analytics queries, not joins.

       Recorded. The original sentence stays exactly as you wrote it, your
       answer is appended next to it, and nothing is scored.

Nothing is saved without you accepting it, and Argus never fills in the outcome for you.

Install

Requirements: Node.js 18 or newer — Node 20 LTS is the tested version (node --version; get it from nodejs.org). No API key and no account: records are local files from the first call.

Pick your host. Every path below installs the same server.

Claude Code

The plugin wires this server for you and adds the decision commands on top:

/plugin marketplace add commet/Argus
/plugin install argus@argus

Restart Claude Code, then /argus:settings doctor confirms the wiring.

Want the server alone, without the commands? Add it directly:

claude mcp add argus -- npx -y argus-decision-mcp          # this project only
claude mcp add -s user argus -- npx -y argus-decision-mcp  # every project

claude mcp add defaults to the current project — use -s user if you want Argus everywhere.

Claude Desktop

Settings → Developer → Edit Config opens the file directly. It lives at:

• macOS — ~/Library/Application Support/Claude/claude_desktop_config.json
• Windows — %APPDATA%\Claude\claude_desktop_config.json

Add Argus to it, then quit Claude Desktop completely and reopen it (a window close is not enough):

{
  "mcpServers": {
    "argus-decision": {
      "command": "npx",
      "args": ["-y", "argus-decision-mcp"],
      "env": {
        "ARGUS_DIR": "/absolute/path/to/where/records/should/live/.argus"
      }
    }
  }
}

ARGUS_DIR is optional here too — a desktop app has no "current project", so records go to your personal home ledger (~/.argus) by default rather than scattering. Set it when you want them somewhere specific. On Windows, escape the backslashes ("C:\\Users\\you\\decisions\\.argus").

Codex (CLI or app)

codex mcp add argus-decision -- npx -y argus-decision-mcp
codex mcp list        # argus-decision should be listed and enabled

Restart Codex afterwards. A conversation opened before mcp add does not gain newly registered tools — quit and reopen the app, or start a new CLI session.

Any other MCP host

{
  "mcpServers": {
    "argus-decision": {
      "command": "npx",
      "args": ["-y", "argus-decision-mcp"],
      "env": {
        "ARGUS_DIR": "/absolute/path/to/your/project/.argus"
      }
    }
  }
}

Install once; there is nothing to update by hand. Leave the version off, as above — npx re-resolves a bare package name on every launch, so each session starts the current build.

Where your records live

On your disk from the first call — nothing to set up.

ARGUS_DIR is optional. The default follows one rule — project evidence decides where the ledger lives:

• the working directory is inside a git repo, or already has an .argus folder → <that-project>/.argus (per-project isolation, unchanged)
• otherwise (a temp folder, or an app that creates a fresh folder per conversation — the Codex desktop app does this) → the personal home ledger (~/.argus), so records accumulate across conversations instead of fragmenting into per-conversation orphans

A per-call absolute argus_dir overrides everything; ARGUS_DIR overrides the rule.

Argus never scans other projects. Existing home-level ledgers are not migrated or merged silently; point ARGUS_DIR at one explicitly if you need to inspect it.

Optional: account sync

Off until you turn it on. Nothing leaves the machine before you approve it in a browser:

npx argus-decision-mcp connect       # one browser approval, credential stored locally
npx argus-decision-mcp disconnect    # revoke it here

Add --headless on a machine with no browser to get a device-code flow. For CI, set ARGUS_TOKEN to a sync token from the web app's settings page instead of running connect. With no credential, sync is a silent no-op — the local record is unaffected.

Your data

The records are plain append-only files under .argus/. They are yours: copy that folder to back it up, delete it to remove it. Uninstalling the server never touches it.

For the durable home that survives moves and worktrees, the CLI also has archive-export, archive-restore, and local-purge. Each one requires explicit arguments — --repository-id, an absolute --archive-dir, and a verbatim --confirm-repository before anything is deleted. That is deliberate: erasing judgment records should never be a one-word command. Run one without arguments and it names the argument it wants.

Tools

The complete callable surface is six tools:

Names from pre-2.0 releases are not callable aliases. A cached call to one of them returns UNKNOWN_TOOL, so hosts cannot accidentally keep using obsolete contracts.

Design boundaries

• Local-first, append-only records.
• Project isolation by default.
• User wording and AI-surfaced wording retain distinct provenance.
• Recorded text is treated as untrusted data.
• No verdict, grade, accuracy score, streak, or leaderboard.
• Network sync is explicit; anonymous telemetry is off unless ARGUS_TELEMETRY=1.
• Unexpected errors are logged server-side and returned as a generic message, avoiding path or stack disclosure to the model.

Development

npm install
npm run typecheck
npm test
npm run build
npm pack --dry-run

The published package contains one bundled runtime entrypoint. Internal implementation and experimental modules are not shipped as separate callable or importable files.

See SECURITY.md for reporting and trust-boundary details.