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What is Aegis

Every AI agent framework reinvents the same governance primitives — and each one does it slightly differently. Aegis is the abstraction layer that unifies them.

Layer

What it does

Examples

1. Primitives

A universal contract for every tool call

Action, ActionClaim, Policy, Result, DelegationChain, AuditEvent

2. Adapters

Auto-instrument any framework through its own hooks

LangChain callbacks, CrewAI BeforeToolCallHook, OpenAI Agents tracing, Google ADK BasePlugin, MCP transport, DSPy modules, httpx middleware, Playwright context

3. Governance

Declarative primitives you compose into policy

Prompt injection / PII / leak / toxicity guardrails, RBAC, rate limit, cost budget, drift detection, anomaly scoring, trust delegation, justification gap, selection audit, Merkle audit chain

4. Lifecycle

One runtime, every stage of agent ops

Scan → Instrument → Policy CI/CD → Runtime → Proxy → Audit

import aegis
aegis.auto_instrument()    # 12 frameworks governed. No other code changes.

Redis is to in-memory data structures what Aegis is to agent governance: one library, every primitive, every framework, one API. You don't write a LangChain guardrail and a CrewAI guardrail and an OpenAI guardrail — you write one Policy and every framework inherits it.


Primitives

The contract every adapter maps into. Framework-agnostic by design.

Primitive

Purpose

Module

Action

Unified representation of any tool / LLM / HTTP / MCP call across all frameworks

aegis.core.action

ActionClaim

Tripartite structure — Declared (agent-authored) / Assessed (Aegis-computed) / Chain (delegation)

aegis.core.action_claim

Policy

Declarative YAML rules: match → risk → approval (auto / approve / block)

aegis.core.policy

ClaimPolicy

Policy layer that evaluates 6-dimensional impact vectors, not just tool names

aegis.core.claim_policy

Guardrails

Deterministic regex checks for injection, PII, prompt leak, toxicity — 2.65ms cold / <1µs warm

aegis.guardrails

DelegationChain

Multi-agent hand-off tracking with monotone trust constraint (non-increasing)

aegis.core.agent_identity

AuditEvent

Tamper-evident append-only log, Merkle-chained, SQLite + JSONL + webhook sinks

aegis.core.merkle_audit

SelectionAudit

Audits what an agent excludes, not just what it picks — detects cosmetic alignment

aegis.core.selection_audit

JustificationGap

6D asymmetric scoring: agents declare impact, Aegis independently assesses, gap triggers escalation

aegis.core.justification_gap

CryptoAuditChain

Ed25519-signed chain for long-term compliance evidence

aegis.core.crypto_audit

Every governance feature in Aegis — anomaly detection, cost budgets, drift, cascade guards, kill switches — is a composition of these primitives. Read the Concepts guide to see how they fit together.


Frameworks

One API. 12 agent frameworks + 3 protocol-level adapters.

Framework

Hook

Status

LangChain

BaseChatModel.invoke/ainvoke, BaseTool.invoke/ainvoke

Stable

CrewAI

Crew.kickoff/kickoff_async, global BeforeToolCallHook

Stable

OpenAI Agents SDK

Runner.run, Runner.run_sync

Stable

OpenAI API

Completions.create (chat & completions)

Stable

Anthropic API

Messages.create

Stable

LiteLLM

completion, acompletion

Stable

Google GenAI

Models.generate_content (new + legacy)

Stable

Google ADK

BasePlugin lifecycle (tool calls, agent routing, sessions)

Stable

Pydantic AI

Agent.run, Agent.run_sync

Stable

LlamaIndex

LLM.chat/achat/complete/acomplete, BaseQueryEngine.query/aquery

Stable

Instructor

Instructor.create, AsyncInstructor.create

Stable

DSPy

Module.__call__, LM.forward/aforward

Stable

MCP

Transport-layer proxy for any MCP server (stdio / HTTP)

Stable

httpx

Middleware for raw HTTP egress (REST agents, webhooks)

Stable

Playwright

Browser context instrumentation for browsing agents

Stable

auto_instrument() detects what's installed and patches only those — no hard dependencies. Custom adapters use the same BaseAdapter interface.

Default Guardrails

Guardrail

Default

What it catches

Prompt injection

Block

10 attack categories, 85+ patterns, multi-language (EN/KO/ZH/JA)

PII detection

Warn

13 categories (email, credit card, SSN, IBAN, API keys, etc.)

Prompt leak

Warn

System prompt extraction attempts

Toxicity

Warn

Harmful, violent, or abusive content

MCP STDIO injection

Block

JSON-RPC injection, frame concatenation, unicode escape bypass (OX Security advisory)

Deterministic regex — no LLM calls, no network. 2.65ms cold / <1µs warm per check.


Use Cases

The same primitives, five different entry points. Pick whichever matches your workflow.

1. Runtime protection (most common)

One line. Any framework.

import aegis
aegis.auto_instrument()

Or zero code changes — AEGIS_INSTRUMENT=1 python my_agent.py. Injection blocking, PII masking, prompt-leak warnings, audit trail, and policy enforcement become active for every LangChain / CrewAI / OpenAI / Anthropic / LiteLLM / ADK / DSPy / LlamaIndex / Pydantic AI call.

Pydantic AI native capability — no monkey-patching, explicit per-agent control:

from pydantic_ai import Agent
from aegis.contrib.pydantic_ai import AegisCapability

agent = Agent(
    "openai:gpt-4o-mini",
    capabilities=[AegisCapability.default()],  # injection, PII, toxicity, prompt-leak, hallucination
)
result = await agent.run("What is AI governance?")

Full Pydantic AI integration guide →

2. Pre-production scanning

Find ungoverned AI calls before they ship.

pip install agent-aegis
aegis scan .
Aegis Governance Scan
=====================
Scanned: 47 files in ./src

Found 5 ungoverned tool call(s):
  agent.py:12   OpenAI        function call with tools= — no governance wrapper  [ASI02]
  tools.py:8    LangChain     @tool "search_db" — no policy check  [ASI02]
  llm.py:21     LiteLLM       litellm.completion() — no governance wrapper  [ASI02]
  run.py:5      subprocess    subprocess.run — direct shell execution  [ASI08]
  api.py:14     HTTP          requests.post — raw HTTP in agent code  [ASI07]

Governance Score: D (5 ungoverned call(s))

Supports --format json|sarif|suggest, --threshold A-F, .aegisscanignore, and inline # aegis: ignore pragmas. Auto-fix with aegis scan --fix.

3. Policy CI/CD

Security tools protect at runtime. Aegis also manages the policy lifecycle — the same way you test and ship code.

aegis plan current.yaml proposed.yaml --audit-db aegis_audit.db

# Policy Impact Analysis
#   Rules: 2 added, 1 removed, 3 modified
#   Impact (replayed 1,247 actions):
#     23 actions would change from AUTO → BLOCK
aegis test policy.yaml tests.yaml                      # Run in CI
aegis test policy.yaml --generate                      # Auto-generate test suite
aegis test new.yaml tests.yaml --regression old.yaml   # Regression check
# .github/workflows/policy-check.yml
- uses: Acacian/aegis@main
  with:
    policy: aegis.yaml
    tests: tests.yaml
    fail-on-regression: true

Or block ungoverned calls at PR time:

- uses: Acacian/aegis@v0.9.5
  with:
    command: scan
    fail-on-ungoverned: true

4. Audit & compliance

Every call is logged to a tamper-evident Merkle chain, with mappings to EU AI Act / NIST AI RMF / SOC2 built in.

aegis audit
  ID  Session       Action        Target   Risk      Decision    Result
  1   a1b2c3d4...   read          crm      LOW       auto        success
  2   a1b2c3d4...   bulk_update   crm      HIGH      approved    success
  3   a1b2c3d4...   delete        crm      CRITICAL  block       blocked

SQLite + JSONL + webhook sinks. Ed25519 signing for long-term evidence. See the Compliance guide.

5. Governance server (multi-agent)

Centralized governance for multiple agents. Each agent connects via SDK, server handles policy, guardrails, audit, and compliance.

pip install 'agent-aegis[server]'
aegis-server

37 REST endpoints + WebSocket audit streaming + web dashboard. Agents auto-register, send heartbeats, and query policy over HTTP. See Governance Framework Server.


30-Second Start

pip install agent-aegis
import aegis
aegis.auto_instrument()
# All 12 frameworks now governed with default guardrails.

Or use a YAML policy for full control:

aegis init  # Creates aegis.yaml
# aegis.yaml
guardrails:
  pii: { enabled: true, action: mask }
  injection: { enabled: true, action: block, sensitivity: medium }

policy:
  version: "1"
  defaults:
    risk_level: medium
    approval: approve
  rules:
    - name: read_safe
      match: { type: "read*" }
      risk_level: low
      approval: auto
    - name: no_deletes
      match: { type: "delete*" }
      risk_level: critical
      approval: block

Install Options

pip install agent-aegis                   # Core (includes auto_instrument for all frameworks)
pip install langchain-aegis               # LangChain standalone integration
pip install 'agent-aegis[mcp]'            # MCP server + proxy
pip install 'agent-aegis[server]'         # REST API + dashboard
pip install 'agent-aegis[all]'            # Everything

MCP Proxy — govern any MCP server with zero code changes

{
  "mcpServers": {
    "filesystem": {
      "command": "uvx",
      "args": ["--from", "agent-aegis[mcp]", "aegis-mcp-proxy",
               "--wrap", "npx", "-y",
               "@modelcontextprotocol/server-filesystem", "/home"]
    }
  }
}

Works with Claude Desktop, Cursor, VS Code, Windsurf. STDIO injection protection, tool poisoning detection, rug-pull detection, argument sanitization, policy evaluation, full audit trail.

Governance Framework Server

Run Aegis as a dedicated governance server with REST API, WebSocket streaming, and web dashboard.

pip install 'agent-aegis[server]'
aegis-server --init          # Generate aegis-server.yaml
aegis-server                 # Start server on :8000

37 REST endpoints covering the full governance lifecycle:

API Group

Endpoints

Purpose

Core

evaluate, execute, audit, policy

Policy evaluation + execution pipeline

Agents

register, heartbeat, list, status

Agent lifecycle management

Guardrails

check, list

Content safety checks

Policy Versioning

commit, diff, rollback, tag

Git-like policy change management

Crypto Audit

verify, entries, evidence

Tamper-proof audit chain verification

Trust & Drift

trust score, drift detection

Per-agent behavioral analysis

Cost

budget check, reports

LLM cost governance

Compliance

reports, regulatory gaps

SOC2 / GDPR / EU AI Act reports

Sessions

list, replay

Session recording + forensic replay

Connect with the Python SDK (sync or async):

from aegis import AegisClient

with AegisClient("http://localhost:8000", agent_id="my-agent") as client:
    result = client.evaluate("delete", "user_data")
    # result["risk_level"] == "CRITICAL", result["is_allowed"] == False
from aegis import AsyncAegisClient

async with AsyncAegisClient("http://localhost:8000", agent_id="my-agent") as client:
    result = await client.evaluate("read", "reports")

Config-driven via aegis-server.yaml — guardrails, webhooks (Slack/PagerDuty), rate limiting, cost budgets, and auth all declarative. See aegis-server.example.yaml.


Why Aegis?

Writing your own

Platform guardrails

Enterprise platforms

Aegis

Abstraction level

Per-framework if/else

Single-vendor SDK

Proprietary gateway

Universal primitives across 12 frameworks

Setup

Days of if/else

Vendor-specific config

Kubernetes + procurement

Code changes

Wrap every call

SDK-specific

Months of integration

Zero — auto-instruments

Policy portability

Rewrite per framework

Locked to ecosystem

Usually single-vendor

One YAML policy, every framework

Governance primitives

Build from scratch

Subset, vendor-defined

Proprietary

10+ composable primitives

Policy CI/CD

None

None

None

Audit trail

printf debugging

Platform logs only

Cloud dashboard

SQLite + JSONL + webhooks + Merkle chain

Compliance

Manual docs

None

Enterprise sales cycle

EU AI Act, NIST, SOC2 built-in

Cost

Engineering time

Free-to-$$$

$$$$ + infra

Free (MIT). Forever.

What Only Aegis Does

Other tools check inputs and outputs. Aegis governs the decision itself — with primitives no other governance runtime exposes.

Capability

What it means

Based on

Tripartite ActionClaim

Every tool call splits into Declared (agent-authored, untrusted), Assessed (Aegis-computed), and Chain (delegation) fields. The structural separation is what makes cosmetic alignment detectable.

Justification Gap measurement on 14,285 tau-bench calls

Justification Gap

6-dimensional asymmetric scoring: agents declare impact, Aegis independently assesses it, and per_dim = max(0, assessed − declared). Under-reporting triggers escalate (>0.15) or block (>0.40).

Name "ActionClaim" from COA-MAS (Carvalho); 6D metric + runtime form original

Selection Governance

Audits what agents exclude, not just what they choose. A model that "helpfully" omits risky options is exerting selection power — Aegis detects this.

Santander et al., arXiv:2602.14606

Monotone Trust Constraint

Delegated agents cannot escalate their own authority. Trust levels must be non-increasing along the chain — violations auto-block.

Lattice-based access control

Full Lifecycle

Scan (detect) → Instrument (protect) → Policy CI/CD (test) → Runtime (govern) → Proxy (gateway) → Audit (trace). One library, one pip install.


CLI

aegis scan ./src/                       # Detect ungoverned AI calls
aegis score ./src/ --policy policy.yaml # Governance score (0-100)
aegis init                              # Generate starter policy
aegis validate policy.yaml              # Validate syntax
aegis plan current.yaml proposed.yaml   # Preview policy changes
aegis test policy.yaml tests.yaml       # Policy regression testing
aegis audit                             # View audit log
aegis serve policy.yaml                 # REST API + dashboard
aegis probe policy.yaml                 # Adversarial policy testing
aegis autopolicy "block deletes"        # Natural language → YAML

Research

Original measurements on public agent trace datasets. Stdlib-only, reproducible in 30 seconds.

  • The Justification Gap in 14,285 Tau-Bench Tool Calls — Formal definition of the Tripartite ActionClaim with a silent-baseline empirical study. 90.3% approve / 9.7% escalate / 0% block across four model:domain groups. Airline domain exposes ~2× the mean gap of retail. Includes soundness sketches for the three structural invariants and an honest note on the max-only override limitation discovered during the study.

  • Tool Distribution Drift in 1,960 Tau-Bench Trajectories — Shannon entropy on tool name sequences across GPT-4o and Sonnet 3.5 New. 39.8% of scored trajectories collapse onto one or two tools by the end. Bimodal distribution, 1.7× cross-model gap. All scripts and raw data included.

Run the same signal on your own trace:

aegis check drift --trace path/to/trace.jsonl

The CLI reads only the tool_name field — never args, CoT, or prompts — so enterprise users can score prod traces without exfiltrating PII.

Documentation

Full documentation at acacian.github.io/aegis:

Contributing

git clone https://github.com/Acacian/aegis.git && cd aegis
make dev      # Install deps + hooks
make test     # Run tests
make lint     # Lint + format check

Contributing GuideGood First IssuesOpen in GitHub Codespaces

License

MIT -- see LICENSE for details.

Copyright (c) 2026 구동하 (Dongha Koo, @Acacian). Created March 21, 2026.


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