Sirius is a normative governance layer for AI coding agents: a local MCP (Model Context Protocol) server that turns project decisions — features, business rules, architecture — into git-versioned markdown that agents obey and humans review via pull requests.

Which coding agents and IDEs are supported?

Claude Code, Cursor, OpenCode, Windsurf, Antigravity CLI and more — 17 clients supported through one-command, non-destructive configuration.

How do I install the Sirius MCP server?

Run npx @sirius-mcp/mcp to start in seconds, or use the Docker image for persistent and VPS deployments. Full guide at /docs/deploy.

Does Sirius send my code to the cloud?

No. Sirius runs 100% locally over stdio with SQLite FTS5 search — zero telemetry, zero egress, air-gap capable.

How much does it cost?

Free for individual developers. Plus/Team and Enterprise tiers are in pilot — join the waitlist below.

stdio ready

v1.8.0 · public mvp

Deploy docs

---

type:featureid:repository-constitution

status: activeaudience:solo devs, tech leads, product managers, architects

---

The MCP server that makes coding agents obey your project's decisions.

Sirius forces AI coding agents to obey project decisions and eliminates code entropy. Ultra-dense MCP kernel (< 400 tokens) for your IDE agents ready in 10 seconds, and a living architecture Web Portal on :4200 for humans to inspect rules, decisions, and topology.

❯ Start the local MCP server with Web Portal on localhost:4200:

npx · stdio + web portal :4200

# Start the local MCP server with the Web Portal on localhost:4200
npx @sirius-mcp/mcp

Transport:MCP stdio (< 12ms JSON-RPC)

UI:Web Portal live on :4200

v1.8.0 npm published17 AST-supported clientsZero telemetry · Zero egress

Explore Web Portal ↓Deploy docs @sirius-mcp/mcp

·01 · THE HIDDEN COST OF AUTONOMOUS AI

The Productivity Paradox: 10x Faster Code Generation Generates 10x Faster Technical Entropy.

THE AI PRODUCTIVITY PARADOX

10x Faster Code Generation ==> 10x Faster Technical Entropy

pain/01

Architectural Entropy (Drift)

Multiple coding agents create competing conventions. The code compiles and tests pass, but the underlying system architecture decays.

pain/02

Business-Execution Abyss

Business rules documented in Jira tickets become obsolete the moment agents code. IDE agents invent arbitrary commercial rules on the fly.

pain/03

Rule Amnesia & Context Eviction

Loose prompt files (.cursorrules) are quickly evicted from context windows to save tokens, leading agents to repeat yesterday's mistakes.

pain/04

Session Memory Fallacy & Compliance Risk

External session memory servers leak proprietary code and PII to third-party clouds with zero auditable Git history for SOC2 or regulators.

·02 · NORMATIVE GOVERNANCE vs. SESSION MEMORY

Normative governance for AI agents. Don't remember yesterday's mistakes — establish what is permitted today.

SESSION MEMORY (Mem0, etc.)

anti-pattern

Unreliable Continuity

✕Captures raw chat transcripts and prompt history
✕Yesterday's bug or bad pattern becomes tomorrow's standard
✕Stored outside the engineering team's control and review

NORMATIVE GOVERNANCE (Sirius)

sirius canonical

Obedience & Traceable Evidence

✓Deliberate invariants, ADRs, and business boundaries
✓Supreme normative authority committed in Git
✓Proposed, reviewed, and merged strictly via Pull Requests

The Inviolable Precedence Contract (5 Canonical Rules)

rule/01

Git Supreme Authority

The .context/ store is the normative source of truth. External chat or session memory is unverified history.

rule/02

Precedence Tie-Breaker

When any prompt or memory diverges from active .context/ documents, .context/ categorically wins.

rule/03

Mandatory Consultation

Agents must query the context store over MCP before generating or modifying code.

rule/04

Prohibition of Silent Bypass

Never silently bypass an active rule. Changes to rules must be proposed in the same Pull Request.

rule/05 · Inviolável

Human Governance in Git

Normative context documents are created, updated, and approved exclusively by human engineers via standard Pull Requests.

Human-in-the-loop PR

Canonical Block Injected into AGENTS.md & CLAUDE.md (SHA-256 Signed):

## Autoridade do projeto: .context/

Este repositório é governado pelo Sirius. Os documentos em .context/ são a autoridade normativa do projeto sobre arquitetura, decisões e regras de negócio.

1. Antes de alterar código coberto por um documento do .context/, leia esse documento via MCP ou em .context/business-rule/precedence-contract.md.

2. Quando qualquer outra fonte divergir do .context/ — memória de sessão, servidores externos, histórico de chat — o .context/ vence categoricamente.

3. Nunca contorne em silêncio um documento active. Se ele parecer errado, declare e proponha a mudança nele no mesmo pull request.

Contrato completo: .context/business-rule/precedence-contract.md

·03 · DUAL-LENS SHOWCASE

Two lenses on the same truth: real-time visual inspection and the new collaborative active workbench.

SIRIUS v1.8.0127.0.0.1:4200Living Architecture Web Portal

Search architecture, rules, decisions...Ctrl+K

127.0.0.1:4200 · Live · Connected

Sirius Living Architecture Web Portal Interface

⚙Store: Realtime Synced

Search: SQLite FTS5

Graph: D3-Force Physics

Endpoint: 127.0.0.1:4200

D3-Force Topology Canvas

Interactive force-directed graph with real-time physics, multi-LOD rendering, navigation minimap, and automatic interconnected node clustering.

Strict 5-Type Taxonomy

Canonical categorization into Architecture Spines, Decisions (ADRs), Features, Business Rules, and Components with dynamic count badges.

Lifecycle & Status Governance

Strict lifecycle state filtering (Active, Draft, Deprecated, Superseded) — ensuring coding agents only consume current invariants and valid decisions.

FTS5 Search & Invariants HUD

Instant Ctrl+K search (SQLite FTS5 + fuzzy lexical ranking) and inspector HUD for frontmatter, boundaries, and rules.

The 4-Stage Co-Creation Lifecycle:

Etapa 01

Product Conception

PO/PM specifies business rules in natural language guided by active repository context.

Etapa 02

Architecture Validation

Tech Lead reviews module boundaries, invariants, and generated Mermaid diagrams.

Etapa 03

Human Git Governance

Specification is proposed and reviewed as a standard Pull Request before merging to main.

Etapa 04

Autonomous AI Execution

Coding agents in the IDE query .context/ via MCP (< 400 tokens) and obey all invariants.

·04 · VALUE PILLARS

Tangible return for those who write code and those who lead the business.

VALUE PILLAR	ENGINEERING & PRODUCT	BUSINESS & LEADERSHIP
1. Product-Engineering Alignment	PMs write rules in Studio; agents consume via MCP. Zero 'telephone game'.	Drastic time-to-market reduction; delivered code faithfully implements commercial rules.
2. Agent Obedience & Zero Rework	Agent respects system conventions from line 1. Zero architectural rework.	Drastic drop in production incidents caused by LLM hallucinations and drift.
3. Accelerated Team Onboarding	New devs open :4200 and understand the entire system topology in minutes.	Developer ramp-up time reduced from weeks to days.
4. Privacy by Design & Zero Egress	Local stdio transport, zero telemetry; Studio with direct BYO Key.	100% compliance with LGPD, GDPR, and SOC2 audits with zero cloud vendor lock-in.
5. Token Efficiency & Cost Reduction	Granular sub-400 token payloads per MCP query. Zero bloated context windows.	Significant LLM API bill reduction and higher model reasoning accuracy.
6. Git Governance (Zero Lock-in)	Pure markdown versioned in Git alongside pull requests and commits.	Zero SaaS vendor lock-in: your intellectual property belongs strictly to your company.

·05 · HEAD-TO-HEAD COMPARISON

Why session memory tools and wikis fail at MCP agent governance.

CRITERION	SIRIUS MCP	SESSION MEMORY (Mem0)	WIKIS (Notion/Confluence)	PROMPTS (.cursorrules)
1. Primary Focus	✓Normative Governance & Product (what is permitted today)	✕Episodic memory (what was done yesterday in chat)	✕Passive documentation for humans	✕Raw system instructions
2. Product + Arch Collaboration	✓Native via Sirius Studio (Product Mode & Architecture Mode)	✕Non-existent (developer JSON API only)	✕Partial (text editor disconnected from code)	✕Non-existent (engineer prompt file only)
3. Divergence Resolution	✓.context/ wins categorically via Precedence Contract	✕Ignored (LLM prioritizes immediate chat over memory)	✕Non-existent (agents do not query wikis directly)	✕Evicted from context window when tokens peak
4. Interface Surface	✓Dual-Lens: MCP stdio (<12ms) + Web Portal :4200 + Studio	✕REST API / Python SDK only (no visual topology)	✕Browser web UI only (unreadable by MCP tools)	✕IDE text editor file only
5. Privacy & Data Egress	✓Zero Egress: 100% local stdio + SQLite FTS5 (air-gapped)	✕Cloud SaaS sends prompts and chat to third-party servers	✕Third-party cloud SaaS holding corporate data	✕Local in repository
6. Token Efficiency	✓< 400 tokens per query (mathematically dense kernel)	✕Bloated conversational dumps (1k–4k tokens per query)	✕Zero MCP optimization (thousands of raw tokens)	✕Forced into every single query prompt unconditionally
7. Auditability & Compliance	✓Native Git SHA commits, PR reviews, and sign-offs	✕Opaque database with no cryptographic audit trail	✕Vague version history without commit hashes	✕Tracked in Git, but lacks semantic rule schemas
8. Client Ecosystem	✓17 clients with non-destructive AST auto-patching	✕1 or 2 specific SDK integrations	✕0 native MCP agent clients	✕IDE-specific (.cursorrules, CLAUDE.md, etc.)

Compare Sirius against:

1. Primary Focus

✓ Sirius:Normative Governance & Product (what is permitted today)

✕ Concorrente:Episodic memory (what was done yesterday in chat)

2. Product + Arch Collaboration

✓ Sirius:Native via Sirius Studio (Product Mode & Architecture Mode)

✕ Concorrente:Non-existent (developer JSON API only)

3. Divergence Resolution

✓ Sirius:.context/ wins categorically via Precedence Contract

✕ Concorrente:Ignored (LLM prioritizes immediate chat over memory)

4. Interface Surface

✓ Sirius:Dual-Lens: MCP stdio (<12ms) + Web Portal :4200 + Studio

✕ Concorrente:REST API / Python SDK only (no visual topology)

5. Privacy & Data Egress

✓ Sirius:Zero Egress: 100% local stdio + SQLite FTS5 (air-gapped)

✕ Concorrente:Cloud SaaS sends prompts and chat to third-party servers

6. Token Efficiency

✓ Sirius:< 400 tokens per query (mathematically dense kernel)

✕ Concorrente:Bloated conversational dumps (1k–4k tokens per query)

7. Auditability & Compliance

✓ Sirius:Native Git SHA commits, PR reviews, and sign-offs

✕ Concorrente:Opaque database with no cryptographic audit trail

8. Client Ecosystem

✓ Sirius:17 clients with non-destructive AST auto-patching

✕ Concorrente:1 or 2 specific SDK integrations

·06 · UNIVERSAL SETUP

Set up your MCP client in 10 seconds: Claude Code, Cursor, OpenCode and more.

17 leading AI coding assistants supported via surgical, non-destructive AST configuration patching.

npx (Zero Docker · Instant startup)

npx @sirius-mcp/mcp

ⓘ Node.js 22+ required for npx. Automatically fetches the latest release from the npm registry with zero container overhead.

MCP clients with native support and instant AST setup:

Claude Code

Cursor

Codex

Windsurf

GitHub Copilot

Google Antigravity

OpenCode

Block Goose

Devin

Claude Desktop

Aider

Kiro

Roo Code

Cline

Continue.dev

Zed

JetBrains AI

✦ Surgically updates existing client configuration files without overwriting or destroying previous settings.

Runs on a VPS too, over docker run -i (stdio transport). The MCP transport is stdio-only today, so treat remote use as a supported setup — not a guarantee of continuous uptime.

·07 · RADICAL HONESTY

Serious engineering does not sell promises. Know exactly what runs today and what is on the roadmap.

Clear separation between production reality in v1.8.0+ and the v2+ roadmap.

PROVEN IN PRODUCTION TODAY

v1.8.0+ on npm

✓Local SQLite FTS5 lexical ranking under 10ms (zero heavy vector dependencies or cloud API latency)
✓Canonical Context Store with 5 strict Zod schemas in Git-versioned Markdown (.context/)
✓Interactive Living Architecture Web Portal on localhost:4200 with D3-Force physics and 127.0.0.1 bind
✓Non-destructive AST setup wizard for 17 leading MCP clients and IDEs
✓Precedence Contract with SHA-256 signed block for AGENTS.md and CLAUDE.md

v2+ VISION & TRANSPARENT ROADMAP

Sequenced post-10 active repos

◷Conversational Sirius Studio: Dual-Lens Chat with opt-in BYO Key and interactive Split Canvas
◷Automated CI Gate (sirius gate) to prevent architectural drift and rule violations on PRs
◷Multi-repo federation (.sirius-workspace.yml) for cross-service organizational context
◷Commercial core: GitHub README-only public repository with official npm package distribution

BYO Key Direct · Zero proxy storage · No SaaS lock-in

·PRICING

Sirius MCP pricing: free for solo developers, scalable for engineering teams.

Solo

active

Freefor individual developers ($0)

Full local MCP server (stdio transport)
All 5 canonical context types (git-tracked)
Local SQLite FTS5 full-text search (zero network egress)
Living Architecture Web Portal (localhost:4200)
Claude Code, Cursor, OpenCode, Windsurf, Antigravity

Install now

Plus Team

coming soon

In Devcontact us for early pilot access

Everything in Solo
.sirius-workspace.yml multi-repo topology
Team Git-shared context synchronization
sirius-gate consultive CI review assistant
Seat management & dedicated team support

Join team waitlist

Enterprise

draft

Customfor organizations requiring governance

Everything in Plus Team
SAML 2.0 / OIDC SSO & SCIM directory sync
Immutable SOC2 audit trail & compliance reporting
Dedicated VPC & Air-Gap deployment support
Custom MSA & 99.9% uptime SLA guarantee

Contact enterprise sales

FAQ

Frequently asked questions about the Sirius MCP server.

What is Sirius?: Sirius is a normative governance layer for AI coding agents: a local MCP (Model Context Protocol) server that turns project decisions — features, business rules, architecture — into git-versioned markdown that agents obey and humans review via pull requests.
Which coding agents and IDEs are supported?: Claude Code, Cursor, OpenCode, Windsurf, Antigravity CLI and more — 17 clients supported through one-command, non-destructive configuration.
How do I install the Sirius MCP server?: Run npx @sirius-mcp/mcp to start in seconds, or use the Docker image for persistent and VPS deployments. Full guide at /docs/deploy.
Does Sirius send my code to the cloud?: No. Sirius runs 100% locally over stdio with SQLite FTS5 search — zero telemetry, zero egress, air-gap capable.
How much does it cost?: Free for individual developers. Plus/Team and Enterprise tiers are in pilot — join the waitlist below.

·ENTERPRISE WAITLIST

Get told when Enterprise ships.

Leave an email. It joins a waitlist — no charge, no commitment.

Get notified directly when team features and updates are ready.