AI Constraint Engine that enforces project rule file constraints as immutable locks, preventing AI coding assistants from violating developer-defined constraints.
SpecLock is an AI Constraint Engine (v5.5.4) developed by Sandeep Roy (@sgroy10). It intercepts rule violations before AI coding assistants execute them, featuring a semantic conflict detection engine and an MCP server with 51 tools.
Core Capabilities#
Semantic Conflict Detection Engine: Dual architecture — pure JavaScript local heuristic engine (zero runtime LLM dependency, ~250ms/check, 95%+ accuracy) and Gemini Flash hybrid mode (cross-domain fallback, ~2s/check, $0.01/1000 checks). Covers 10+ attack patterns: direct violation, euphemism/beautification attacks, temporal evasion, dilution attacks, compound sentence splitting, synonym substitution, payment gateway brand identification (11 Indian gateways), salary/compensation cross-vocabulary, security system bypass, and unknown domains. Built-in 65+ synonym groups, 80+ euphemism mappings, 9 domain concept graphs (fintech, e-commerce, IoT, healthcare, SaaS, payments, gaming, telecom, government). Claude adversarial test: 100/100 score, zero false positives, 15.7ms/check.
Enforcement Modes: Advisory (default, AI receives warning and decides) and Hard mode (MCP returns isError, AI cannot proceed, configurable 70% confidence threshold).
Patch Security Review: Patch Gateway (v5.1) outputs ALLOW/WARN/BLOCK judgment, blast radius, and risk score (0-100) from description + file list; AI Patch Firewall (v5.2) reviews actual diffs, detecting interface breakage, protected symbol editing, dependency drift, schema changes across 10 signals, with unified review weights: intent 35% + diff 65%.
Spec Compiler & Code Graph: NL→constraint auto-extraction (supports PRD/README/architecture docs as input); dependency graph with JS/TS/Python import resolution, blast radius analysis, lock-to-file mapping.
Typed Constraints: Numeric, range, state transition, and time interval constraints for autonomous systems, IoT, and robotics.
Project Health Metrics: Drift Score (0-100) measuring deviation from original intent; Lock Coverage scanning unprotected high-risk areas; Lock Strengthener evaluating and suggesting improvements for each lock.
Cross-Tool Sync: speclock sync --all syncs constraints to Cursor, Claude Code, GitHub Copilot, Windsurf, Gemini, Aider, AGENTS.md (7 formats).
Security Templates: Built-in safe-defaults (Vibe Coding seatbelt), hipaa, api-stability, solo-founder, nextjs, security-hardened, etc.
Auto-Guard: Automatically discovers related files after locking rules and injects SPECLOCK-GUARD comments so AI sees warnings when opening files.
Event Replay: Flight recorder for AI coding sessions, replaying each operation and SpecLock judgment.
Enterprise Security#
RBAC + API Key authentication (4 roles: viewer/developer/architect/admin); AES-256-GCM encrypted storage with PBKDF2 key derivation (100K iterations); HMAC-SHA256 audit chain with each event hash-linked to the previous one for tamper detection; compliance export for SOC 2 Type II, HIPAA PHI protection reports, CSV; Policy-as-Code via YAML declarative rules (.speclock/policy.yml).
Architecture Overview#
AI tools connect to SpecLock Core Engine via MCP Protocol (51 tools) or npm file-based approach (SPECLOCK.md + CLI). Core engine contains semantic engine, HMAC audit chain, enforcer, auth & RBAC, AES-256-GCM encryption, Policy DSL, and compliance export modules. All state stored in local .speclock/ directory (brain.json, events.log, policy.yml, auth.json, context/). Only 3 npm runtime dependencies, semantic engine has zero external dependencies. 991 tests, 19 test suites, 100% pass rate.
Distribution & Adaptation#
- Node.js: npm package
speclock - Python: pip package
speclock-sdk, sharing the same.speclock/brain.jsonwith Node.js CLI - ROS2 Guardian Node: subscribes to
/joint_states,/cmd_vel, publishes violations to/speclock/violations, triggers emergency stop - AI tool compatibility: Claude Code, Cursor, Windsurf, Cline, Codex, Bolt.new, Lovable, GitHub Copilot, Gemini, Aider
- Listed on Smithery MCP Registry
Quick Start#
npx speclock protect
speclock mcp install claude-code
speclock doctor
Python SDK: pip install speclock-sdk
Strict mode: speclock protect --strict or env var SPECLOCK_STRICT=1
Unconfirmed Items#
- Actual npm package version (page blocked by Cloudflare, cannot verify alignment with README's v5.5.4)
- Actual availability of pricing tiers (Free/Pro $19/mo/Enterprise $99/mo) — no billing implementation evidence found
- SSO integration (Okta/Azure AD/Auth0) mentioned only in architecture diagram, no config docs or implementation code
- ROS2 node completeness and availability not deeply verified
- VS Code extension (
vscode-extension/directory exists) — not verified if published to Marketplace - Test count discrepancy: README states 991 tests, website shows 1073, possibly website not updated
- No associated academic papers found