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securitycritical PriorityID: tls13-hybrid-pq-ml-kem-guardrail

Enforce TLS 1.3 Hybrid Post-Quantum ML-KEM Key Encapsulation

Enforces hybrid classical and post-quantum key encapsulation (X25519MLKEM768 / SecP256r1MLKEM768) across all TLS 1.3 edge terminators, reverse proxies, and microservice clients. Defends ingress and egress channels against 'Harvest Now, Decrypt Later' (HNDL) adversarial vectors by disallowing pure classical elliptic curve key exchanges and mandating modern cryptographic library configurations.

Prohibited Anti-Pattern: Defaulting to Classical-Only ECDHE Key Exchanges in Modern TLS 1.3 Endpoints

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---
description: Enforce TLS 1.3 Hybrid Post-Quantum ML-KEM Key Encapsulation - Enforces hybrid classical and post-quantum key encapsulation (X25519MLKEM768 / SecP256r1MLKEM768) across all TLS 1.3 edge terminators, reverse proxies, and microservice clients. Defends ingress and egress channels against 'Harvest Now, Decrypt Later' (HNDL) adversarial vectors by disallowing pure classical elliptic curve key exchanges and mandating modern cryptographic library configurations.
globs: src/**/tls*.ts, src/**/crypto*.ts, src/**/network*.ts, src/**/server*.ts, src/**/proxy*.ts, k8s/**/*.yaml, terraform/**/*.tf
alwaysApply: true
verified_by: "agentrules.org"
license: "CC-BY-4.0"
source: "https://agentrules.org/rules/tls13-hybrid-pq-ml-kem-guardrail"
---

# Enforce TLS 1.3 Hybrid Post-Quantum ML-KEM Key Encapsulation

> **Severity**: CRITICAL | **Category**: security
> **Anti-Pattern Warning**: Defaulting to Classical-Only ECDHE Key Exchanges in Modern TLS 1.3 Endpoints

## System Constraints
You are a Principal Security Architect enforcing mandatory Post-Quantum Cryptography (PQC) transition rules. All incoming and outgoing secure communications must leverage TLS 1.3 with hybrid ML-KEM (FIPS 203) key encapsulation mechanisms combined with classical algorithms (X25519 or P-256). Reject pure ECDHE groups, TLS versions prior to 1.3, and unvalidated cipher suites.

## Strict Guidelines
- Engineers MUST ALWAYS configure TLS 1.3 as the strict minimum protocol version (`minVersion: 'TLSv1.3'`).
- Services MUST prioritize hybrid PQC key exchange groups (e.g., `X25519MLKEM768`, `SecP256r1MLKEM768`, or OpenSSL/BoringSSL equivalents `X25519Kyber768Draft00`) at all edge endpoints.
- Engineers MUST NOT negotiate pure classical groups (like standalone `P-256` or `X25519`) when communicating with post-quantum capable internal infrastructure or edge terminations.
- Code SHOULD dynamically assert peer-negotiated key exchange groups in secure TLS sockets and emit critical telemetry or terminate connections if a hybrid PQC group was dropped or downgraded.
- Components NEVER permit insecure fallback renegotiation or legacy cipher suites vulnerable to store-now-decrypt-later quantum attacks.

## Bad vs Good Implementations
### Node.js TLS Server Configuration with Hybrid ML-KEM Group Enforcement

#### Bad Antipattern (AI Common Hallucination)
> **Why it fails**: Configuring TLS 1.2 and pure classical curves (`prime256v1:X25519`) leaves mission-critical payloads exposed to quantum cryptanalysis via Harvest Now, Decrypt Later threats.
```typescript
import * as tls from 'node:tls';
import * as fs from 'node:fs';

// Flaw: Allows legacy TLS versions and classical-only ECDHE key exchange
export function createSecureEdgeServer() {
  return tls.createServer({
    key: fs.readFileSync('/etc/ssl/certs/server.key'),
    cert: fs.readFileSync('/etc/ssl/certs/server.crt'),
    minVersion: 'TLSv1.2',
    // Vulnerable to Harvest Now, Decrypt Later (HNDL)
    ecdhCurve: 'prime256v1:X25519'
  });
}
```

#### Production Standard (Correct)
> **Standard**: Restricts TLS protocol strictly to TLS 1.3, prioritizes hybrid ML-KEM key exchange curves conforming to NIST FIPS 203, and inspects the negotiated ephemeral key exchange algorithm to abort unapproved classical-only handshakes.
```typescript
import * as tls from 'node:tls';
import * as fs from 'node:fs';
import { TLSSocket } from 'node:tls';

const PQ_HYBRID_CURVES = 'X25519MLKEM768:SecP256r1MLKEM768';

export function createSecureEdgeServer() {
  const server = tls.createServer({
    key: fs.readFileSync('/etc/ssl/certs/server.key'),
    cert: fs.readFileSync('/etc/ssl/certs/server.crt'),
    minVersion: 'TLSv1.3',
    maxVersion: 'TLSv1.3',
    // Enforce FIPS 203 Hybrid Post-Quantum Key Encapsulation Mechanism
    ecdhCurve: PQ_HYBRID_CURVES,
    ciphers: 'TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256'
  });

  server.on('secureConnection', (socket: TLSSocket) => {
    const negotiated = socket.getEphemeralKeyInfo();
    // Validate that hybrid key exchange occurred
    if (negotiated && !['X25519MLKEM768', 'SecP256r1MLKEM768'].includes(negotiated.name)) {
      socket.destroy(new Error(`PQC Violation: Insecure key exchange negotiated: ${negotiated.name}`));
    }
  });

  return server;
}
```
Recommended MCP Servers (mcp-serverlist.com)

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

TLS Cryptography Inspector MCP
Inspects SSL/TLS endpoints, verifying supported key exchange groups, ML-KEM negotiation, and TLS 1.3 cipher suite configurations.
Recommended Agent Skills (askills.dev)

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

OQS OpenSSL Hybrid Validator
CLI test skill executing OpenSSL s_client tests with liboqs to audit ML-KEM-768 hybrid key exchanges.
Architectural Specification & Invariant Rationale

Architectural Invariant Design: Enforce TLS 1.3 Hybrid Post-Quantum ML-KEM Key Encapsulation

Enforce TLS 1.3 Hybrid Post-Quantum ML-KEM Key Encapsulation defines an industrial-grade behavioral standard for security engineering. Enforces hybrid classical and post-quantum key encapsulation (X25519MLKEM768 / SecP256r1MLKEM768) across all TLS 1.3 edge terminators, reverse proxies, and microservice clients. Defends ingress and egress channels against 'Harvest Now, Decrypt Later' (HNDL) adversarial vectors by disallowing pure classical elliptic curve key exchanges and mandating modern cryptographic library configurations. 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: Defaulting to Classical-Only ECDHE Key Exchanges in Modern TLS 1.3 Endpoints 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 DriftDefaulting to Classical-Only ECDHE Key Exchanges in Modern TLS 1.3 EndpointsCritical
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

Engineers MUST ALWAYS configure TLS 1.3 as the strict minimum protocol version (`minVersion

Engineers MUST ALWAYS configure 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 prioritize hybrid PQC key exchange groups (e.g., `X25519MLKEM768`, `SecP256r1MLKEM768`, or OpenSSL/BoringSSL equivalents `X25519Kyber768Draft00`) at all edge endpoints.

Services MUST prioritize hybrid PQC key exchange groups (e.g., `X25519MLKEM768`, `SecP256r1MLKEM768`, or OpenSSL/BoringSSL equivalents `X25519Kyber768Draft00`) at all edge endpoints.

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 negotiate pure classical groups (like standalone `P-256` or `X25519`) when communicating with post-quantum capable internal infrastructure or edge terminations.

Engineers MUST NOT negotiate pure classical groups (like standalone `P-256` or `X25519`) when communicating with post-quantum capable internal infrastructure or edge terminations.

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

Code SHOULD dynamically assert peer-negotiated key exchange groups in secure TLS sockets and emit critical telemetry or terminate connections if a hybrid PQC group was dropped or downgraded.

Code SHOULD dynamically assert peer-negotiated key exchange groups in secure TLS sockets and emit critical telemetry or terminate connections if a hybrid PQC group was dropped or downgraded.

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

Components NEVER permit insecure fallback renegotiation or legacy cipher suites vulnerable to store-now-decrypt-later quantum attacks.

Components NEVER permit insecure fallback renegotiation or legacy cipher suites vulnerable to store-now-decrypt-later quantum attacks.

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 Enforce TLS 1.3 Hybrid Post-Quantum ML-KEM Key Encapsulation critical for AI coding assistants?

Enforces hybrid classical and post-quantum key encapsulation (X25519MLKEM768 / SecP256r1MLKEM768) across all TLS 1.3 edge terminators, reverse proxies, and microservice clients. Defends ingress and egress channels against 'Harvest Now, Decrypt Later' (HNDL) adversarial vectors by disallowing pure classical elliptic curve key exchanges and mandating modern cryptographic library configurations. 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 (Defaulting to Classical-Only ECDHE Key Exchanges in Modern TLS 1.3 Endpoints) 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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