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.brain — the portable decision log

The portable decision log your AI tools all read. One MCP server. Any AI tool. Plain files.

PyPI version License: MIT MCP Compatible NPM nucleus-mcp MCP server

Every AI coding session starts by re-explaining context the last session already knew. .brain is a folder in your repo that Claude Code, Cursor, and Codex all read via one MCP server. Decisions, policies, plans — written once, remembered across every session and every tool.

MIT licensed. File-based (plain JSON + markdown). No embeddings. No vendor lock-in.


Three Frontiers

The core loop that makes AI reliability compound over time:

  GROUND              ALIGN               COMPOUND
  ──────              ─────               ────────
  Machine verifies    Human corrects      System learns

  AI writes code  →  You fix a mistake →  Delta recorded
  GROUND checks   →  Verdict stored    →  DPO pair created
  Receipt logged  →  Event emitted     →  Training data grows
       │                   │                    │
       ā””ā”€ā”€ā”€ā”€ā”€ā”€ā”€ā”€ā”€ā”€ā”€ā”€ā”€ā”€ā”€ā”€ā”€ā”€ā”€ā”“ā”€ā”€ā”€ā”€ā”€ā”€ā”€ā”€ā”€ā”€ā”€ā”€ā”€ā”€ā”€ā”€ā”€ā”€ā”€ā”€ā”˜
                    Reliability improves

GROUND — 5-tier execution verification. Syntax, imports, tests, runtime. Goes outside the formal system to check the AI's work.

ALIGN — One-call corrections. nucleus_align(action="correct", params={context, correction}). Each correction automatically records a verdict, creates a training pair, and emits an event.

COMPOUND — Deltas measure the gap between intent and reality. Recurring patterns become strategy. Negative deltas become training signal.

Every tool response shows frontier health:

[frontiers: GROUND 42 | ALIGN 12 | COMPOUND 28]

Quick Start

pip install nucleus-mcp
nucleus init --recipe founder

Two commands. Nucleus is running. AI outputs are now verified.


What It Does

114 MCP tools across 13 facades:

  • GROUND — Execution verification (5 tiers: diff, syntax, imports, tests, runtime)

  • ALIGN — Human corrections (verdict + delta + DPO + event in one call)

  • Memory — Engrams that persist across sessions. Write once, recall forever.

  • Sessions — Save context, resume later. Session arc shows your last 3 sessions.

  • Tasks — Priority queue with escalation, HITL gates, and heartbeat monitoring.

  • Governance — Kill switch, compliance configs (EU DORA, MAS TRM, SOC2), audit trails.

  • Orchestration — Agent slots, multi-brain sync, task dispatch.

  • Archive — Training pipeline (SFT + DPO), delta tracking, frontier health dashboard.

Benchmark: decision-retention-evals — does your AI agent remember why the code is the way it is?


Nucleus Pro

Everything above is free (MIT). Nucleus Pro adds verifiable governance:

nucleus trial                              # 14-day free trial
nucleus compliance-check                   # Score your AI governance
nucleus audit-report --signed -o report.html  # Cryptographically signed report

$19/month or $149/year — nucleusos.dev/pricing

Free

Pro

13 tools, 10 resources, 3 prompts

Yes

Yes

Persistent memory

Yes

Yes

Governance & HITL

Yes

Yes

Audit trails (DSoR)

Yes

Yes

Signed audit reports

-

Ed25519

Compliance exports

Score only

Full PDF/HTML

Priority issues

-

Yes


Install

One-Click

IDE

Install

Cursor

Add to Cursor

Claude Code

npx -y nucleus-mcp

Any IDE

pip install nucleus-mcp

pip / npx

pip install nucleus-mcp

Or use npx (zero Python setup required):

npx -y nucleus-mcp

Configure Your MCP Client

Claude Desktop / Cursor / Windsurf

Add to your MCP config (claude_desktop_config.json or equivalent):

{
  "mcpServers": {
    "nucleus": {
      "command": "npx",
      "args": ["-y", "nucleus-mcp"]
    }
  }
}
{
  "mcpServers": {
    "nucleus": {
      "command": "python3",
      "args": ["-m", "mcp_server_nucleus"],
      "env": {
        "NUCLEUS_BRAIN_PATH": "/path/to/your/project/.brain"
      }
    }
  }
}

Claude Code

Add to .mcp.json in your project root:

{
  "mcpServers": {
    "nucleus": {
      "command": "npx",
      "args": ["-y", "nucleus-mcp"]
    }
  }
}

Path Discovery

Nucleus finds your .brain automatically:

  1. NUCLEUS_BRAIN_PATH environment variable (explicit)

  2. Walk up from CWD looking for .brain/ directory

  3. Fall back to $HOME/.nucleus/brain


CLI

Nucleus has a full CLI alongside the MCP tools. Auto-detects TTY (table output) vs pipe (JSON).

# Memory
nucleus engram write my_key "insight here" --context Decision --intensity 7
nucleus engram search "compliance"
nucleus engram query --context Strategy --limit 10

# Tasks
nucleus task list --status READY
nucleus task add "Ship the feature" --priority 1

# Sessions
nucleus session save "Working on auth refactor"
nucleus session resume

# Health
nucleus status --health
nucleus sovereign

# Compliance
nucleus comply --jurisdiction eu-dora
nucleus audit-report --format html -o report.html

# Chat (multi-provider: Gemini, Anthropic, Groq)
nucleus chat

Pipe-friendly:

nucleus engram search "test" | jq '.key'
nucleus task list --format tsv | cut -f1,3

Compliance

One-command configuration for regulatory frameworks:

nucleus comply --jurisdiction eu-dora       # EU DORA
nucleus comply --jurisdiction sg-mas-trm    # Singapore MAS TRM
nucleus comply --jurisdiction us-soc2       # US SOC2

Jurisdiction

Retention

HITL Ops

Kill Switch

eu-dora

7 years

5 types

Required

sg-mas-trm

5 years

5 types

Required

us-soc2

1 year

3 types

Optional

global-default

90 days

2 types

Optional


Telemetry

Nucleus collects anonymous, aggregate usage statistics (command name, duration, error type, versions, OS). No engram content, no file paths, no prompts, no API keys, no PII — ever.

nucleus config --no-telemetry
# or: NUCLEUS_ANON_TELEMETRY=false

See TELEMETRY.md for details.


Contributing

License

MIT Ā© 2026 | hello@nucleusos.dev

Install Server
A
license - permissive license
A
quality
C
maintenance

Maintenance

–Maintainers
–Response time
5wRelease cycle
2Releases (12mo)

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