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securitycritical PriorityID: post-quantum-hybrid-tls13-mlkem-enforcement

Mandatory Post-Quantum Hybrid TLS 1.3 (ML-KEM) Key Exchange Standard

Enforces post-quantum hybrid key encapsulation (FIPS 203 ML-KEM-768 combined with classical ECDH curves like X25519) across all service-to-service transport configurations. Prevents Harvest-Now-Decrypt-Later (HNDL) attacks by mandating TLS 1.3 minimum versions, restricting curve preferences to hybrid groups, and rejecting classical-only key exchanges in zero-trust mesh traffic.

Prohibited Anti-Pattern: Configuring classical-only key exchange or permissive TLS downgrades vulnerable to Harvest-Now-Decrypt-Later threats.

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---
description: Mandatory Post-Quantum Hybrid TLS 1.3 (ML-KEM) Key Exchange Standard - Enforces post-quantum hybrid key encapsulation (FIPS 203 ML-KEM-768 combined with classical ECDH curves like X25519) across all service-to-service transport configurations. Prevents Harvest-Now-Decrypt-Later (HNDL) attacks by mandating TLS 1.3 minimum versions, restricting curve preferences to hybrid groups, and rejecting classical-only key exchanges in zero-trust mesh traffic.
globs: src/network/**/*.ts, src/infra/**/*.ts, src/clients/**/*.ts, src/mesh/**/*.ts
alwaysApply: true
verified_by: "agentrules.org"
license: "CC-BY-4.0"
source: "https://agentrules.org/rules/post-quantum-hybrid-tls13-mlkem-enforcement"
---

# Mandatory Post-Quantum Hybrid TLS 1.3 (ML-KEM) Key Exchange Standard

> **Severity**: CRITICAL | **Category**: security
> **Anti-Pattern Warning**: Configuring classical-only key exchange or permissive TLS downgrades vulnerable to Harvest-Now-Decrypt-Later threats.

## System Constraints
You are a Principal Security Architect enforcing Post-Quantum Hybrid TLS 1.3 (ML-KEM) standards across internal service meshes and egress network clients. You must strictly enforce FIPS 203 ML-KEM hybrid key exchange groups (specifically X25519MLKEM768 or SecP256r1MLKEM768), mandate TLSv1.3 as the minimum protocol version, disable classical-only fallback curves, and prevent Harvest-Now-Decrypt-Later vulnerabilities.

## Strict Guidelines
- Services MUST ALWAYS enforce TLS 1.3 as the strict minimum protocol version (`minVersion: 'TLSv1.3'`).
- Services MUST explicitly specify hybrid Post-Quantum Key Encapsulation Mechanism (PQ-KEM) curves in TLS curve preferences, prioritizing `X25519MLKEM768` (or transitional identifier `x25519_kyber768`).
- Engineers MUST NOT allow silent fallback to classical-only curves (e.g., pure `X25519`, `prime256v1`, or legacy ECDHE groups) without throwing cryptographic policy violation errors.
- Services MUST NEVER configure TLS 1.2 or earlier versions for zero-trust service-to-service traffic.
- Network clients SHOULD monitor and emit telemetry whenever an upstream connection fails to negotiate a hybrid post-quantum key agreement group.
- Code MUST strictly validate peer TLS session states post-handshake to verify the negotiated ephemeral key exchange group matches an approved ML-KEM hybrid suite.

## Bad vs Good Implementations
### Post-Quantum Hybrid TLS 1.3 Agent Configuration

#### Bad Antipattern (AI Common Hallucination)
> **Why it fails**: Configuring minVersion as TLSv1.2 and relying on default system curves fails to mandate post-quantum hybrid key exchange. Adversaries intercepting and recording traffic can decrypt it once cryptanalytically relevant quantum computers (CRQCs) become operational.
```typescript
import https from 'node:https';
import tls from 'node:tls';

// Flaw: Permissive TLS configuration defaults to classical ECDHE and allows TLS 1.2
export function createMeshAgent(): https.Agent {
  return new https.Agent({
    minVersion: 'TLSv1.2',
    // Implicit default curves (X25519, P-256) vulnerable to Harvest-Now-Decrypt-Later
    secureOptions: tls.constants.SSL_OP_NO_SSLv2 | tls.constants.SSL_OP_NO_SSLv3,
  });
}
```

#### Production Standard (Correct)
> **Standard**: Enforces TLS 1.3 exclusively, restricts ECDH curve negotiation to hybrid ML-KEM-768 groups (mitigating HNDL attacks), and performs an explicit post-handshake key exchange group verification check.
```typescript
import https from 'node:https';
import tls from 'node:tls';

// Mandatory FIPS 203 / IETF ML-KEM hybrid curve identifiers
const APPROVED_PQ_HYBRID_CURVES = 'X25519MLKEM768:x25519_kyber768';

export function createMeshAgent(): https.Agent {
  return new https.Agent({
    minVersion: 'TLSv1.3',
    maxVersion: 'TLSv1.3',
    ecdhCurve: APPROVED_PQ_HYBRID_CURVES,
    honorCipherOrder: true,
    checkServerIdentity: (hostname, cert) => {
      const defaultError = tls.checkServerIdentity(hostname, cert);
      if (defaultError) return defaultError;
      return undefined;
    },
  });
}

export function verifyQuantumResistantNegotiation(socket: tls.TLSSocket): void {
  const keyExchange = socket.getEphemeralKeyInfo();
  // Verify that an approved ML-KEM hybrid group was successfully negotiated
  if (!keyExchange || !('name' in keyExchange) || !keyExchange.name.includes('MLKEM768')) {
    socket.destroy(new Error('CRITICAL_SECURITY_VIOLATION: Non-PQ hybrid key exchange negotiated'));
  }
}
```
Recommended MCP Servers (mcp-serverlist.com)

Equip agent with system tools to verify code for this stack.

TLS Cipher & Curve Audit Server
Inspects active TLS client and server configurations to detect missing ML-KEM hybrid key exchange groups and insecure protocol versions.
Recommended Agent Skills (askills.dev)

Ready-to-use executable skill functions tailored to this stack.

Post-Quantum Cryptography Linter
Scans infrastructure-as-code and microservice networking clients for classical-only TLS cipher configurations and missing FIPS 203 ML-KEM preferences.
Architectural Specification & Invariant Rationale

Architectural Invariant Design: Mandatory Post-Quantum Hybrid TLS 1.3 (ML-KEM) Key Exchange Standard

Mandatory Post-Quantum Hybrid TLS 1.3 (ML-KEM) Key Exchange Standard defines an industrial-grade behavioral standard for security engineering. Enforces post-quantum hybrid key encapsulation (FIPS 203 ML-KEM-768 combined with classical ECDH curves like X25519) across all service-to-service transport configurations. Prevents Harvest-Now-Decrypt-Later (HNDL) attacks by mandating TLS 1.3 minimum versions, restricting curve preferences to hybrid groups, and rejecting classical-only key exchanges in zero-trust mesh traffic. Modern software architectures require strict adherence to deterministic patterns to guarantee high availability, maintainability, and zero security vulnerabilities.

Framework Paradigm Shift & Drift MechanicsLLMs are trained on millions of open-source repositories containing outdated code, legacy idioms, and unpatched antipatterns. When coding assistants generate implementations for this stack, they default to common statistical tokens: Configuring classical-only key exchange or permissive TLS downgrades vulnerable to Harvest-Now-Decrypt-Later threats. Without an explicit system instruction file, developers spend hours debugging silent failures.
Failure Modes & Production Blast Radius

Hazard Analysis: What Breaks Without This Rule

The following failure modes have been cataloged from hundreds of hours of production code reviews where AI assistants produced non-compliant implementations:

Failure ModeAI Symptom (The Anti-Pattern)SeverityProduction Impact & Remedy
AI Hallucination & Deprecation DriftConfiguring classical-only key exchange or permissive TLS downgrades vulnerable to Harvest-Now-Decrypt-Later threats.Critical
Violating this industrial standard introduces regression bugs, security risks, and unexpected runtime failures in production.
Enforce explicit behavioral system directives across all AI coding assistants in your repository.
Silent Architecture InconsistencyAI assistants produce mixed paradigms across files, creating fragmented codebase conventions.Medium
Increases cognitive load during code reviews and leads to maintenance debt across engineering teams.
Pin project conventions in .cursor/rules, CLAUDE.md, and AGENTS.md so all team agents follow identical guardrails.
Architectural Directives in Detail

Step-by-Step Production Directives

Each rule constraint below is injected into the AI agent's system prompt to establish deterministic boundaries:

1

Services MUST ALWAYS enforce TLS 1.3 as the strict minimum protocol version (`minVersion

Services MUST ALWAYS enforce TLS 1.3 as the strict minimum protocol version (`minVersion: 'TLSv1.3'`).

Rationale:AI models frequently generate unconstrained code here because statistical language distributions lack project-specific architectural context. Mandating this directive ensures that generated code adheres to verified industrial production requirements.
Enforcement:Integrated into the Agent Pack rule file. When Cursor, Claude Code, or Codex processes this prompt, it applies this constraint before emitting syntax.
2

Services MUST explicitly specify hybrid Post-Quantum Key Encapsulation Mechanism (PQ-KEM) curves in TLS curve preferences, prioritizing `X25519MLKEM768` (or transitional identifier `x25519_kyber768`).

Services MUST explicitly specify hybrid Post-Quantum Key Encapsulation Mechanism (PQ-KEM) curves in TLS curve preferences, prioritizing `X25519MLKEM768` (or transitional identifier `x25519_kyber768`).

Rationale:AI models frequently generate unconstrained code here because statistical language distributions lack project-specific architectural context. Mandating this directive ensures that generated code adheres to verified industrial production requirements.
Enforcement:Integrated into the Agent Pack rule file. When Cursor, Claude Code, or Codex processes this prompt, it applies this constraint before emitting syntax.
3

Engineers MUST NOT allow silent fallback to classical-only curves (e.g., pure `X25519`, `prime256v1`, or legacy ECDHE groups) without throwing cryptographic policy violation errors.

Engineers MUST NOT allow silent fallback to classical-only curves (e.g., pure `X25519`, `prime256v1`, or legacy ECDHE groups) without throwing cryptographic policy violation errors.

Rationale:AI models frequently generate unconstrained code here because statistical language distributions lack project-specific architectural context. Mandating this directive ensures that generated code adheres to verified industrial production requirements.
Enforcement:Integrated into the Agent Pack rule file. When Cursor, Claude Code, or Codex processes this prompt, it applies this constraint before emitting syntax.
4

Services MUST NEVER configure TLS 1.2 or earlier versions for zero-trust service-to-service traffic.

Services MUST NEVER configure TLS 1.2 or earlier versions for zero-trust service-to-service traffic.

Rationale:AI models frequently generate unconstrained code here because statistical language distributions lack project-specific architectural context. Mandating this directive ensures that generated code adheres to verified industrial production requirements.
Enforcement:Integrated into the Agent Pack rule file. When Cursor, Claude Code, or Codex processes this prompt, it applies this constraint before emitting syntax.
5

Network clients SHOULD monitor and emit telemetry whenever an upstream connection fails to negotiate a hybrid post-quantum key agreement group.

Network clients SHOULD monitor and emit telemetry whenever an upstream connection fails to negotiate a hybrid post-quantum key agreement group.

Rationale:AI models frequently generate unconstrained code here because statistical language distributions lack project-specific architectural context. Mandating this directive ensures that generated code adheres to verified industrial production requirements.
Enforcement:Integrated into the Agent Pack rule file. When Cursor, Claude Code, or Codex processes this prompt, it applies this constraint before emitting syntax.
6

Code MUST strictly validate peer TLS session states post-handshake to verify the negotiated ephemeral key exchange group matches an approved ML-KEM hybrid suite.

Code MUST strictly validate peer TLS session states post-handshake to verify the negotiated ephemeral key exchange group matches an approved ML-KEM hybrid suite.

Rationale:AI models frequently generate unconstrained code here because statistical language distributions lack project-specific architectural context. Mandating this directive ensures that generated code adheres to verified industrial production requirements.
Enforcement:Integrated into the Agent Pack rule file. When Cursor, Claude Code, or Codex processes this prompt, it applies this constraint before emitting syntax.
Technical Questions & Answers

Frequently Asked Technical Questions

Common questions developers face when configuring AI coding assistants for this stack:

Q:Why is Mandatory Post-Quantum Hybrid TLS 1.3 (ML-KEM) Key Exchange Standard critical for AI coding assistants?

Enforces post-quantum hybrid key encapsulation (FIPS 203 ML-KEM-768 combined with classical ECDH curves like X25519) across all service-to-service transport configurations. Prevents Harvest-Now-Decrypt-Later (HNDL) attacks by mandating TLS 1.3 minimum versions, restricting curve preferences to hybrid groups, and rejecting classical-only key exchanges in zero-trust mesh traffic. Without explicit behavioral boundaries, AI coding assistants (Cursor, Claude Code, Windsurf, Codex) rely on training data averages, which frequently produce deprecated, inefficient, or vulnerable code patterns.

Q:How does adopting this rule prevent AI hallucinations?

This rule explicitly declares what the AI must avoid (Configuring classical-only key exchange or permissive TLS downgrades vulnerable to Harvest-Now-Decrypt-Later threats.) and prescribes verified positive examples. Grounding the LLM with negative and positive pairs eliminates guesswork.

Q:Which AI coding environments are supported?

This specification is multi-platform compatible: Cursor (.cursor/rules/*.mdc & .cursorrules), Anthropic Claude Code (CLAUDE.md), Windsurf (.windsurfrules), Codex / Cline (AGENTS.md), and GitHub Copilot (.github/copilot-instructions.md).

Q:Can I combine this rule with other technology stacks?

Yes. Use the Interactive Stack Builder or download an Agent Pack to merge this rule with other frontend, backend, database, security, and DevOps rules without syntax collision.

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