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devopscritical PriorityID: envoy-gateway-extauthz-fail-closed-circuit-breaker

Envoy Gateway 1.2 ExtAuthz Fail-Closed & Dynamic Circuit Breaker Guardrail

Enforces deterministic fail-closed states and granular upstream circuit breakers for External Authorization (ExtAuthz) policy decision points in Envoy Gateway 1.2. Eliminates authorization bypass and thread pool exhaustion during PDP latency spikes by instantly severing degraded auth uplinks and returning explicit HTTP 403/500 responses.

Prohibited Anti-Pattern: Configuring Permissive ExtAuthz Fail-Open or Omitting Dynamic Circuit Breakers on Policy Decision Points

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---
description: Envoy Gateway 1.2 ExtAuthz Fail-Closed & Dynamic Circuit Breaker Guardrail - Enforces deterministic fail-closed states and granular upstream circuit breakers for External Authorization (ExtAuthz) policy decision points in Envoy Gateway 1.2. Eliminates authorization bypass and thread pool exhaustion during PDP latency spikes by instantly severing degraded auth uplinks and returning explicit HTTP 403/500 responses.
globs: k8s/**/*.yaml, k8s/**/*.yml, gateway/**/*.yaml, gateway/**/*.yml, manifests/**/*.yaml, manifests/**/*.yml, helm/**/*.yaml
alwaysApply: true
verified_by: "agentrules.org"
license: "CC-BY-4.0"
source: "https://agentrules.org/rules/envoy-gateway-extauthz-fail-closed-circuit-breaker"
---

# Envoy Gateway 1.2 ExtAuthz Fail-Closed & Dynamic Circuit Breaker Guardrail

> **Severity**: CRITICAL | **Category**: devops
> **Anti-Pattern Warning**: Configuring Permissive ExtAuthz Fail-Open or Omitting Dynamic Circuit Breakers on Policy Decision Points

## System Constraints
You are a Principal Infrastructure Architect enforcing strict Envoy Gateway 1.2 security invariants. You must prevent any ExtAuthz configuration that allows fail-open behavior, missing timeouts, or unconstrained concurrency to external policy decision points (PDPs). Any configuration lacking explicit circuit breakers or fail-closed invariants must be immediately rejected.

## Strict Guidelines
- Engineers MUST ALWAYS configure `failOpen: false` on every Envoy Gateway `SecurityPolicy` defining an `extAuth` provider.
- Engineers MUST ALWAYS pair external authorization services with a `BackendTrafficPolicy` specifying strict `circuitBreakers` (maxConnections, maxPendingRequests, maxRequests).
- Services MUST configure aggressive sub-second request timeouts (`<= 250ms`) on ExtAuthz gRPC/HTTP uplinks to prevent ingress worker thread starvation.
- Engineers MUST NOT omit `outlierDetection` on authorization backends; eject deteriorating PDP instances using consecutive 5xx or local origin error thresholds.
- Components NEVER allow unauthenticated traffic bleeding through gateway routes when the authorization PDP is degraded or unreachable.

## Bad vs Good Implementations
### Envoy Gateway 1.2 ExtAuthz SecurityPolicy & BackendTrafficPolicy Invariant

#### Bad Antipattern (AI Common Hallucination)
> **Why it fails**: Enabling `failOpen: true` allows unauthorized requests through to internal microservices whenever the authorization PDP experiences network partitions or high latency. Furthermore, omitting circuit breaking and timeout policies risks cascading thread pool exhaustion across Envoy gateway workers.
```yaml
apiVersion: gateway.envoyproxy.io/v1alpha1
kind: SecurityPolicy
metadata:
  name: edge-security-policy
  namespace: gateway-system
spec:
  targetRef:
    group: gateway.networking.k8s.io
    kind: Gateway
    name: edge-gateway
  extAuth:
    failOpen: true # FATAL: Degraded PDP allows unauthenticated edge bleed
    grpc:
      backendRefs:
        - name: auth-pdp-service
          port: 9001
      # FATAL: Missing explicit timeouts and circuit breaker constraints
```

#### Production Standard (Correct)
> **Standard**: Enforces `failOpen: false` ensuring zero unauthenticated bleed if the PDP degrades. Enforces an explicit `BackendTrafficPolicy` targeting the auth PDP service with a 200ms strict timeout and tight circuit breaker limits to prevent Envoy worker connection starvation.
```yaml
apiVersion: gateway.envoyproxy.io/v1alpha1
kind: SecurityPolicy
metadata:
  name: edge-security-policy
  namespace: gateway-system
spec:
  targetRef:
    group: gateway.networking.k8s.io
    kind: Gateway
    name: edge-gateway
  extAuth:
    failOpen: false # INVARIANT: Deterministic fail-closed security posture
    headersToExtAuth:
      - authorization
      - x-request-id
    grpc:
      backendRefs:
        - name: auth-pdp-service
          port: 9001
---
apiVersion: gateway.envoyproxy.io/v1alpha1
kind: BackendTrafficPolicy
metadata:
  name: auth-pdp-traffic-policy
  namespace: gateway-system
spec:
  targetRef:
    group: ""
    kind: Service
    name: auth-pdp-service
  timeout:
    request: 200ms
  circuitBreakers:
    maxConnections: 1024
    maxPendingRequests: 128
    maxRequests: 2048
  faultInjection: null
  retry:
    numRetries: 1
    retryOn:
      triggers:
        - reset
        - connect-failure
```
Recommended MCP Servers (mcp-serverlist.com)

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

Kubernetes Resource Validator MCP
Inspects and validates live cluster Envoy Gateway CRDs, SecurityPolicies, and BackendTrafficPolicies for compliance.
Recommended Agent Skills (askills.dev)

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

Kubeconform Validation CLI
Validates Kubernetes manifests and custom CRD schemas for Envoy Gateway 1.2 to detect policy misconfigurations.
Architectural Specification & Invariant Rationale

Architectural Invariant Design: Envoy Gateway 1.2 ExtAuthz Fail-Closed & Dynamic Circuit Breaker Guardrail

Envoy Gateway 1.2 ExtAuthz Fail-Closed & Dynamic Circuit Breaker Guardrail defines an industrial-grade behavioral standard for devops engineering. Enforces deterministic fail-closed states and granular upstream circuit breakers for External Authorization (ExtAuthz) policy decision points in Envoy Gateway 1.2. Eliminates authorization bypass and thread pool exhaustion during PDP latency spikes by instantly severing degraded auth uplinks and returning explicit HTTP 403/500 responses. 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 Permissive ExtAuthz Fail-Open or Omitting Dynamic Circuit Breakers on Policy Decision Points 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 Permissive ExtAuthz Fail-Open or Omitting Dynamic Circuit Breakers on Policy Decision PointsCritical
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 `failOpen

Engineers MUST ALWAYS configure `failOpen: false` on every Envoy Gateway `SecurityPolicy` defining an `extAuth` provider.

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

Engineers MUST ALWAYS pair external authorization services with a `BackendTrafficPolicy` specifying strict `circuitBreakers` (maxConnections, maxPendingRequests, maxRequests).

Engineers MUST ALWAYS pair external authorization services with a `BackendTrafficPolicy` specifying strict `circuitBreakers` (maxConnections, maxPendingRequests, maxRequests).

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

Services MUST configure aggressive sub-second request timeouts (`<= 250ms`) on ExtAuthz gRPC/HTTP uplinks to prevent ingress worker thread starvation.

Services MUST configure aggressive sub-second request timeouts (`<= 250ms`) on ExtAuthz gRPC/HTTP uplinks to prevent ingress worker thread starvation.

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

Engineers MUST NOT omit `outlierDetection` on authorization backends

Engineers MUST NOT omit `outlierDetection` on authorization backends; eject deteriorating PDP instances using consecutive 5xx or local origin error thresholds.

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 allow unauthenticated traffic bleeding through gateway routes when the authorization PDP is degraded or unreachable.

Components NEVER allow unauthenticated traffic bleeding through gateway routes when the authorization PDP is degraded or unreachable.

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 Envoy Gateway 1.2 ExtAuthz Fail-Closed & Dynamic Circuit Breaker Guardrail critical for AI coding assistants?

Enforces deterministic fail-closed states and granular upstream circuit breakers for External Authorization (ExtAuthz) policy decision points in Envoy Gateway 1.2. Eliminates authorization bypass and thread pool exhaustion during PDP latency spikes by instantly severing degraded auth uplinks and returning explicit HTTP 403/500 responses. 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 Permissive ExtAuthz Fail-Open or Omitting Dynamic Circuit Breakers on Policy Decision Points) 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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