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devopscritical PriorityID: envoy-wasm-fail-closed-circuit-breaker-production-standard

Envoy Gateway Wasm Filter Fail-Closed Policy & Panic Isolation Invariant

Enforces strict fail-closed (deny-by-default) semantics on Envoy Gateway dynamic WebAssembly (Wasm) authorization extensions. Mandates explicit filter failure mode configurations and circuit breakers to guarantee zero-trust compliance by preventing unauthenticated traffic bypass when Wasm runtime panics or VM out-of-memory traps occur.

Prohibited Anti-Pattern: Configuring Wasm authorization filters with fail-open policies (fail_open: true or omitted fail-closed directives), permitting unauthorized ingress traffic during runtime VM panics.

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---
description: Envoy Gateway Wasm Filter Fail-Closed Policy & Panic Isolation Invariant - Enforces strict fail-closed (deny-by-default) semantics on Envoy Gateway dynamic WebAssembly (Wasm) authorization extensions. Mandates explicit filter failure mode configurations and circuit breakers to guarantee zero-trust compliance by preventing unauthenticated traffic bypass when Wasm runtime panics or VM out-of-memory traps occur.
globs: k8s/**/*.yaml, deploy/**/*.yaml, envoy/**/*.yaml, gateway/**/*.yaml, **/*wasmplugin*.yaml, **/*envoyextensionpolicy*.yaml, **/*envoyfilter*.yaml
alwaysApply: true
verified_by: "agentrules.org"
license: "CC-BY-4.0"
source: "https://agentrules.org/rules/envoy-wasm-fail-closed-circuit-breaker-production-standard"
---

# Envoy Gateway Wasm Filter Fail-Closed Policy & Panic Isolation Invariant

> **Severity**: CRITICAL | **Category**: devops
> **Anti-Pattern Warning**: Configuring Wasm authorization filters with fail-open policies (fail_open: true or omitted fail-closed directives), permitting unauthorized ingress traffic during runtime VM panics.

## System Constraints
You are a Principal Software Architect enforcing zero-trust ingress security. Mandate invariant fail-closed behaviors across all Envoy Gateway WebAssembly (Wasm) filters. Reject any EnvoyExtensionPolicy, EnvoyFilter, or WasmPlugin definition that enables fail-open behavior, omits strict timeout controls, or lacks deterministic panic-handling circuit breakers.

## Strict Guidelines
- Engineers MUST ALWAYS explicitly declare `failOpen: false` on all EnvoyExtensionPolicy or WasmPlugin resources executing security, authentication, or authorization logic.
- Engineers MUST NOT omit the `failOpen` or failure mode attributes, relying on default behavior which may silently default to fail-open across different runtime implementations.
- Services MUST configure explicit execution timeouts (e.g., maximum 100ms) on Wasm filter invocations to prevent upstream thread pool exhaustion and denial-of-service conditions.
- Code MUST integrate Envoy local reply configurations or circuit-breaking status mappers to emit structured 403 Forbidden or 503 Service Unavailable responses upon Wasm VM crashes.
- Components NEVER route unauthenticated traffic directly to protected downstreams when a proxy-wasm ABI panic or memory limit violation occurs.

## Bad vs Good Implementations
### Envoy Gateway EnvoyExtensionPolicy Fail-Closed Configuration

#### Bad Antipattern (AI Common Hallucination)
> **Why it fails**: Setting failOpen: true on an authorization Wasm extension creates a catastrophic zero-trust security bypass: any runtime panic or unhandled exception immediately forwards the request unauthenticated to upstream workloads.
```yaml
apiVersion: gateway.envoyproxy.io/v1alpha1
kind: EnvoyExtensionPolicy
metadata:
  name: auth-wasm-policy
  namespace: ingress-gateway
spec:
  targetRef:
    group: gateway.networking.k8s.io
    kind: HTTPRoute
    name: secured-api-route
  wasm:
    - name: ztna-authenticator
      code:
        type: Image
        image: oci-registry.internal/security/wasm-auth:v1.4.0
      # VIOLATION: Explicitly setting failOpen to true or omitting it permits
      # unauthenticated traffic bypass when the Wasm plugin encounters a panic.
      failOpen: true
```

#### Production Standard (Correct)
> **Standard**: Explicitly declaring `failOpen: false` with bounded execution timeout (`100ms`) ensures that if the Wasm runtime encounters a fatal trap, panic, or latency spike, Envoy immediately rejects the request with an error, preserving zero-trust integrity.
```yaml
apiVersion: gateway.envoyproxy.io/v1alpha1
kind: EnvoyExtensionPolicy
metadata:
  name: auth-wasm-policy
  namespace: ingress-gateway
spec:
  targetRef:
    group: gateway.networking.k8s.io
    kind: HTTPRoute
    name: secured-api-route
  wasm:
    - name: ztna-authenticator
      code:
        type: Image
        image: oci-registry.internal/security/wasm-auth:v1.4.0
      # INVARIANT: Strict fail-closed policy guarantees traffic is terminated on filter crash
      failOpen: false
      timeout: 100ms
```
Recommended MCP Servers (mcp-serverlist.com)

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

Kubernetes Resource Validator MCP
Validates Kubernetes manifests against live clusters and OpenAPI schema constraints prior to deployment.
Recommended Agent Skills (askills.dev)

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

Kubeconform Policy Checker
Fast schema validation CLI for Kubernetes manifests and Envoy Custom Resource Definitions.
Architectural Specification & Invariant Rationale

Architectural Invariant Design: Envoy Gateway Wasm Filter Fail-Closed Policy & Panic Isolation Invariant

Envoy Gateway Wasm Filter Fail-Closed Policy & Panic Isolation Invariant defines an industrial-grade behavioral standard for devops engineering. Enforces strict fail-closed (deny-by-default) semantics on Envoy Gateway dynamic WebAssembly (Wasm) authorization extensions. Mandates explicit filter failure mode configurations and circuit breakers to guarantee zero-trust compliance by preventing unauthenticated traffic bypass when Wasm runtime panics or VM out-of-memory traps occur. 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 Wasm authorization filters with fail-open policies (fail_open: true or omitted fail-closed directives), permitting unauthorized ingress traffic during runtime VM panics. 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 Wasm authorization filters with fail-open policies (fail_open: true or omitted fail-closed directives), permitting unauthorized ingress traffic during runtime VM panics.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

Engineers MUST ALWAYS explicitly declare `failOpen

Engineers MUST ALWAYS explicitly declare `failOpen: false` on all EnvoyExtensionPolicy or WasmPlugin resources executing security, authentication, or authorization logic.

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 NOT omit the `failOpen` or failure mode attributes, relying on default behavior which may silently default to fail-open across different runtime implementations.

Engineers MUST NOT omit the `failOpen` or failure mode attributes, relying on default behavior which may silently default to fail-open across different runtime implementations.

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 explicit execution timeouts (e.g., maximum 100ms) on Wasm filter invocations to prevent upstream thread pool exhaustion and denial-of-service conditions.

Services MUST configure explicit execution timeouts (e.g., maximum 100ms) on Wasm filter invocations to prevent upstream thread pool exhaustion and denial-of-service conditions.

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 MUST integrate Envoy local reply configurations or circuit-breaking status mappers to emit structured 403 Forbidden or 503 Service Unavailable responses upon Wasm VM crashes.

Code MUST integrate Envoy local reply configurations or circuit-breaking status mappers to emit structured 403 Forbidden or 503 Service Unavailable responses upon Wasm VM crashes.

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 route unauthenticated traffic directly to protected downstreams when a proxy-wasm ABI panic or memory limit violation occurs.

Components NEVER route unauthenticated traffic directly to protected downstreams when a proxy-wasm ABI panic or memory limit violation occurs.

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 Wasm Filter Fail-Closed Policy & Panic Isolation Invariant critical for AI coding assistants?

Enforces strict fail-closed (deny-by-default) semantics on Envoy Gateway dynamic WebAssembly (Wasm) authorization extensions. Mandates explicit filter failure mode configurations and circuit breakers to guarantee zero-trust compliance by preventing unauthenticated traffic bypass when Wasm runtime panics or VM out-of-memory traps occur. 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 Wasm authorization filters with fail-open policies (fail_open: true or omitted fail-closed directives), permitting unauthorized ingress traffic during runtime VM panics.) 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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