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devopscritical PriorityID: envoy-gateway-wasmplugin-sandboxed-invariant

Envoy Gateway 1.2 WasmPlugin Isolation and Thread-Safety Invariant

Enforces strict runtime isolation, resource limits, and failure domain boundaries for WebAssembly plugins executed within Envoy Gateway 1.2. Preempts control plane crashes, main proxy event-loop blocking, and data plane thread starvation by mandating fail-open fallbacks, strict memory limits, and isolated runtime configurations.

Prohibited Anti-Pattern: Attaching unconstrained WasmPlugins without fail-open policies, dedicated VM runtimes, or strict resource boundaries

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---
description: Envoy Gateway 1.2 WasmPlugin Isolation and Thread-Safety Invariant - Enforces strict runtime isolation, resource limits, and failure domain boundaries for WebAssembly plugins executed within Envoy Gateway 1.2. Preempts control plane crashes, main proxy event-loop blocking, and data plane thread starvation by mandating fail-open fallbacks, strict memory limits, and isolated runtime configurations.
globs: **/*.yaml, **/*.yml, k8s/**/*.yaml, deploy/**/*.yaml
alwaysApply: true
verified_by: "agentrules.org"
license: "CC-BY-4.0"
source: "https://agentrules.org/rules/envoy-gateway-wasmplugin-sandboxed-invariant"
---

# Envoy Gateway 1.2 WasmPlugin Isolation and Thread-Safety Invariant

> **Severity**: CRITICAL | **Category**: devops
> **Anti-Pattern Warning**: Attaching unconstrained WasmPlugins without fail-open policies, dedicated VM runtimes, or strict resource boundaries

## System Constraints
You are a Principal Cloud-Native Infrastructure Engineer enforcing strict Envoy Gateway 1.2 WasmPlugin runtime safety. Custom Wasm extensions execute within Envoy's worker threads; any memory corruption, blocking operation, or panic within a non-sandboxed or misconfigured WasmPlugin can destabilize the edge proxy and cause widespread cascading outages. Mandate fail-open behavior, distinct VM configurations, and strict pull/digest policies.

## Strict Guidelines
- Engineers MUST ALWAYS set `failStrategy: FailOpen` on high-throughput ingress routes unless the Wasm module is strictly an authentication/authorization enforcement gate.
- Engineers MUST ALWAYS reference Wasm container images using immutable SHA-256 digests (`image@sha256:...`) instead of floating or mutable tags like `latest`.
- Engineers MUST configure isolated VM runtime configurations using unique `vmConfig` environments to prevent memory collisions across multiple plugins.
- Engineers MUST NOT execute synchronous blocking operations, unbounded memory allocations, or infinite loops within the Wasm plugin code that can block Envoy worker event loops.
- Platform manifests MUST pair WasmPlugin attachments with explicit EnvoyProxy resource quotas (`resources.limits.memory` and `resources.limits.cpu`) to prevent unmanaged OOM-killer proxy termination.

## Bad vs Good Implementations
### Unconstrained WasmPlugin with Floating Tag and Missing Fail Strategy vs Sandboxed WasmPlugin Guardrail

#### Bad Antipattern (AI Common Hallucination)
> **Why it fails**: Using a mutable image tag (`:latest`) introduces non-deterministic builds and runtime risks. Omitting `failStrategy` risks `FailClose` behavior, taking down edge routing if the Wasm module panics or fails initialization. No explicit pull policy or digest verification is provided.
```yaml
apiVersion: gateway.envoyproxy.io/v1alpha1
kind: EnvoyExtensionPolicy
metadata:
  name: custom-header-filter
  namespace: default
spec:
  targetRef:
    group: gateway.networking.k8s.io
    kind: HTTPRoute
    name: edge-traffic-route
  wasm:
    - code:
        type: Image
        image:
          url: docker.io/myorg/custom-header-wasm:latest
      # ANTI-PATTERN: Default/missing failStrategy defaults to FailClose in strict contexts,
      # mutable image tag can break data-plane at pull time, and missing VM sandbox settings.
```

#### Production Standard (Correct)
> **Standard**: Pinning by cryptographic SHA-256 digest guarantees immutability across rollout nodes. Explicitly setting `failStrategy: FailOpen` prevents proxy downtime on unhandled exceptions or panic states. Selecting an explicit, hardened runtime sandbox (`envoy.wasm.runtime.v8`) maintains predictable execution isolation.
```yaml
apiVersion: gateway.envoyproxy.io/v1alpha1
kind: EnvoyExtensionPolicy
metadata:
  name: custom-header-filter
  namespace: default
spec:
  targetRef:
    group: gateway.networking.k8s.io
    kind: HTTPRoute
    name: edge-traffic-route
  wasm:
    - failStrategy: FailOpen
      code:
        type: Image
        image:
          url: docker.io/myorg/custom-header-wasm@sha256:4f5a3e1f0e4b859942a9876a3e5e19f7f4d2f8084a4f89d3a010d8a9e2d3b4c5
          pullPolicy: IfNotPresent
      vmConfig:
        runtime: envoy.wasm.runtime.v8
        environmentVariables:
          hostEnvKeys:
            - TRUSTED_HEADER_SALT
```
Recommended MCP Servers (mcp-serverlist.com)

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

Kubernetes Resource Validator MCP
Validates Kubernetes custom resource schemas and Envoy Gateway CRDs against cluster API versions and OpenAPI specifications.
Recommended Agent Skills (askills.dev)

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

Envoy Gateway CLI Validator
Translates and validates Envoy Gateway API objects and provides diagnostic output for Wasm extension configuration errors.
Architectural Specification & Invariant Rationale

Architectural Invariant Design: Envoy Gateway 1.2 WasmPlugin Isolation and Thread-Safety Invariant

Envoy Gateway 1.2 WasmPlugin Isolation and Thread-Safety Invariant defines an industrial-grade behavioral standard for devops engineering. Enforces strict runtime isolation, resource limits, and failure domain boundaries for WebAssembly plugins executed within Envoy Gateway 1.2. Preempts control plane crashes, main proxy event-loop blocking, and data plane thread starvation by mandating fail-open fallbacks, strict memory limits, and isolated runtime 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: Attaching unconstrained WasmPlugins without fail-open policies, dedicated VM runtimes, or strict resource boundaries 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 DriftAttaching unconstrained WasmPlugins without fail-open policies, dedicated VM runtimes, or strict resource boundariesCritical
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 set `failStrategy

Engineers MUST ALWAYS set `failStrategy: FailOpen` on high-throughput ingress routes unless the Wasm module is strictly an authentication/authorization enforcement gate.

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 reference Wasm container images using immutable SHA-256 digests (`image@sha256

Engineers MUST ALWAYS reference Wasm container images using immutable SHA-256 digests (`image@sha256:...`) instead of floating or mutable tags like `latest`.

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 configure isolated VM runtime configurations using unique `vmConfig` environments to prevent memory collisions across multiple plugins.

Engineers MUST configure isolated VM runtime configurations using unique `vmConfig` environments to prevent memory collisions across multiple plugins.

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 execute synchronous blocking operations, unbounded memory allocations, or infinite loops within the Wasm plugin code that can block Envoy worker event loops.

Engineers MUST NOT execute synchronous blocking operations, unbounded memory allocations, or infinite loops within the Wasm plugin code that can block Envoy worker event loops.

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

Platform manifests MUST pair WasmPlugin attachments with explicit EnvoyProxy resource quotas (`resources.limits.memory` and `resources.limits.cpu`) to prevent unmanaged OOM-killer proxy termination.

Platform manifests MUST pair WasmPlugin attachments with explicit EnvoyProxy resource quotas (`resources.limits.memory` and `resources.limits.cpu`) to prevent unmanaged OOM-killer proxy termination.

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 WasmPlugin Isolation and Thread-Safety Invariant critical for AI coding assistants?

Enforces strict runtime isolation, resource limits, and failure domain boundaries for WebAssembly plugins executed within Envoy Gateway 1.2. Preempts control plane crashes, main proxy event-loop blocking, and data plane thread starvation by mandating fail-open fallbacks, strict memory limits, and isolated runtime 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 (Attaching unconstrained WasmPlugins without fail-open policies, dedicated VM runtimes, or strict resource boundaries) 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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