Constraint Deviation Engine (CDE) — Gateway Demo

Runnable reference implementation of Constraint Deviation Engine (CDE) as governance middleware for tool-using agents.

This repo includes:

• Python CDE core: computes deviation events from constraint-accessible turn packets (layered extractors, stratified baselines, EMA persistence + hysteresis, auditable rationale artifacts).
• Warm CDE service (FastAPI): stateful /turn endpoint with per-session_id engine instances.
• Node/Express gateway: enforces hard outcomes for simulated tool calls using explicit gate math:
  • Gate 0 — pass-through
  • Gate 1 — evidence required (dry-run + diff)
  • Gate 2 — destructive blocked unless a time-limited capability lease is provided

Quickstart

Run the full gateway demo (starts FastAPI + Node, prints a transcript, then shuts both down):

cd gateway_node
npm install
npm run demo

Demo details and transcript:

• gateway_node/README.md

Python core (optional)

Run the standalone Python engine demo:

python3 -m venv .venv && source .venv/bin/activate
python3 -m pip install -r requirements.txt
python3 run_demo.py

Outputs:

• logs/cde_audit.jsonl
• logs/last_run_summary.json

Key files

• src/engine.py — CDE core engine
• manifests/*.json — baselines + thresholds
• cde_service.py — warm FastAPI CDE service (session-aware)
• gateway_node/server.js — gateway enforcement (floors, leases, evidence gates)
• gateway_node/demo.js — scripted transcript runner

License

CC BY-NC 4.0 — see LICENSE.

Contact

Stephen A. Putman — putmanmodel@pm.me