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frontendcritical PriorityID: vite6-environment-api-multi-runtime-isolation-vite-6-environme-241

Vite 6 Environment API Multi-Runtime Module Graph & HMR Boundary Enforcement

Enforces strict isolation between heterogeneous runtime environments (client, node SSR, edge/workerd, and RSC) using the Vite 6 Environment API. Guarantees that module graphs, transform pipelines, and hot-module replacement (HMR) boundaries do not leak state or trigger invalid cross-runtime graph mutations across isolated execution contexts.

Prohibited Anti-Pattern: Cross-Runtime Module Graph Contamination and Unscoped Legacy SSR Invalidation

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---
description: Vite 6 Environment API Multi-Runtime Module Graph & HMR Boundary Enforcement - Enforces strict isolation between heterogeneous runtime environments (client, node SSR, edge/workerd, and RSC) using the Vite 6 Environment API. Guarantees that module graphs, transform pipelines, and hot-module replacement (HMR) boundaries do not leak state or trigger invalid cross-runtime graph mutations across isolated execution contexts.
globs: vite.config.{ts,js,mjs}, plugins/**/*.ts, src/entry-*.ts, server/**/*.ts
alwaysApply: true
verified_by: "agentrules.org"
license: "CC-BY-4.0"
source: "https://agentrules.org/rules/vite6-environment-api-multi-runtime-isolation-vite-6-environme-241"
---

# Vite 6 Environment API Multi-Runtime Module Graph & HMR Boundary Enforcement

> **Severity**: CRITICAL | **Category**: frontend
> **Anti-Pattern Warning**: Cross-Runtime Module Graph Contamination and Unscoped Legacy SSR Invalidation

## System Constraints
You are a Principal Software Architect enforcing the Vite 6 Environment API Multi-Runtime Module Execution Standard. You must mandate strict runtime boundary isolation across all Vite plugins, dev server middleware, and SSR/Edge runtimes. Never allow legacy Vite 5 SSR patterns (e.g., server.moduleGraph, server.ssrLoadModule, or server.ws) to mediate cross-environment dependencies or trigger global HMR invalidations.

## Strict Guidelines
- Plugins MUST access environment state exclusively through `this.environment` within plugin hooks rather than relying on global server references.
- Engineers MUST NOT access or mutate `server.moduleGraph` directly when multi-environment execution is configured; target `server.environments[envName].moduleGraph` instead.
- Code interacting with HMR MUST scope invalidations and event dispatching to `this.environment.hot` or `server.environments[name].hot` rather than broadcasting via `server.ws.send`.
- Environment definitions inside `vite.config.ts` MUST declare explicit runtime capabilities (e.g., Node vs. Workerd vs. Browser) using modern `environments` options instead of combining polyfills into a single global resolve alias.
- Custom execution runtimes MUST implement a dedicated `DevEnvironment` or `FetchableDevEnvironment` to maintain isolated evaluation contexts and prevent memory-space collision between client and server modules.
- Engineers MUST NOT use deprecated `server.ssrTransform` or `server.ssrLoadModule`; they MUST use `environment.transformRequest` and the environment's configured module runner.

## Bad vs Good Implementations
### Configuring Isolated Multi-Runtime Environments and Environment-Scoped Plugins

#### Bad Antipattern (AI Common Hallucination)
> **Why it fails**: Accessing server.moduleGraph and server.ws pollutes the dev server state across runtimes, failing when multiple server-side runtimes (like Workerd and Node) coexist. Relying on options.ssr fails to delineate complex execution contexts such as React Server Components (RSC client vs. RSC server vs. SSR).
```typescript
import { defineConfig, type Plugin } from 'vite';

// ANTI-PATTERN: Vite 5 legacy multi-runtime handling leaking server module graph
export function legacyCrossRuntimePlugin(): Plugin {
  return {
    name: 'legacy-cross-runtime',
    handleHotUpdate({ server, file, modules }) {
      // Leaks SSR and client nodes into a single global invalidation
      const mod = server.moduleGraph.getModuleById(file);
      if (mod) {
        server.moduleGraph.invalidateModule(mod);
      }
      // Indiscriminately broadcasts HMR payload across all heterogeneous client/server targets
      server.ws.send({ type: 'full-reload' });
      return modules;
    },
    transform(code, id, options) {
      // Legacy boolean flag prevents granular multi-runtime distinction (e.g. edge vs node)
      const isSSR = options?.ssr;
      if (isSSR) {
        return code.replace('__RUNTIME__', '"node"');
      }
      return code.replace('__RUNTIME__', '"client"');
    }
  };
}

export default defineConfig({
  plugins: [legacyCrossRuntimePlugin()]
});
```

#### Production Standard (Correct)
> **Standard**: Adheres to Vite 6 Environment API by using this.environment inside plugin hooks. Module invalidation and HMR communications are strictly bound to the originating environment (client, ssr, edge) without contaminating adjacent runtimes or broadcasting invalid payloads across boundaries.
```typescript
import { defineConfig, type Plugin, DevEnvironment } from 'vite';

// PRODUCTION STANDARD: Vite 6 Environment API with isolated module graphs & HMR scopes
export function modernMultiRuntimePlugin(): Plugin {
  return {
    name: 'modern-multi-runtime',
    // Use the per-environment hook context
    hotUpdate({ modules, file }) {
      // this.environment guarantees isolation to the target runtime (client, ssr, or edge)
      const envModule = this.environment.moduleGraph.getModuleById(file);
      if (envModule) {
        this.environment.moduleGraph.invalidateModule(envModule);
      }
      // Scope HMR dispatch exclusively to the environment's transport boundary
      this.environment.hot.send({
        type: 'custom',
        event: 'env:runtime-invalidated',
        data: { env: this.environment.name, file }
      });
      return modules;
    },
    transform(code, id) {
      // Distinct runtime determination via environment name
      const runtimeName = this.environment.name;
      return code.replace('__RUNTIME__', JSON.stringify(runtimeName));
    }
  };
}

export default defineConfig({
  environments: {
    client: {
      build: { outDir: 'dist/client' }
    },
    ssr: {
      build: { outDir: 'dist/server' },
      resolve: { noExternal: true }
    },
    edge: {
      build: { outDir: 'dist/edge' },
      resolve: { conditions: ['worker', 'webworker'] }
    }
  },
  plugins: [modernMultiRuntimePlugin()]
});
```
Recommended MCP Servers (mcp-serverlist.com)

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

Vite Inspect Protocol Server
Exposes module graph resolution and environment-specific transform pipelines to LLMs for debugging HMR boundaries.
Recommended Agent Skills (askills.dev)

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

Vite Runtime Verification Tool
CLI utility to inspect and validate isolated environment configurations, runner compatibility, and graph boundaries.
Architectural Specification & Invariant Rationale

Architectural Invariant Design: Vite 6 Environment API Multi-Runtime Module Graph & HMR Boundary Enforcement

Vite 6 Environment API Multi-Runtime Module Graph & HMR Boundary Enforcement defines an industrial-grade behavioral standard for frontend engineering. Enforces strict isolation between heterogeneous runtime environments (client, node SSR, edge/workerd, and RSC) using the Vite 6 Environment API. Guarantees that module graphs, transform pipelines, and hot-module replacement (HMR) boundaries do not leak state or trigger invalid cross-runtime graph mutations across isolated execution contexts. 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: Cross-Runtime Module Graph Contamination and Unscoped Legacy SSR Invalidation 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 DriftCross-Runtime Module Graph Contamination and Unscoped Legacy SSR InvalidationCritical
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

Plugins MUST access environment state exclusively through `this.environment` within plugin hooks rather than relying on global server references.

Plugins MUST access environment state exclusively through `this.environment` within plugin hooks rather than relying on global server references.

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 access or mutate `server.moduleGraph` directly when multi-environment execution is configured

Engineers MUST NOT access or mutate `server.moduleGraph` directly when multi-environment execution is configured; target `server.environments[envName].moduleGraph` instead.

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

Code interacting with HMR MUST scope invalidations and event dispatching to `this.environment.hot` or `server.environments[name].hot` rather than broadcasting via `server.ws.send`.

Code interacting with HMR MUST scope invalidations and event dispatching to `this.environment.hot` or `server.environments[name].hot` rather than broadcasting via `server.ws.send`.

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

Environment definitions inside `vite.config.ts` MUST declare explicit runtime capabilities (e.g., Node vs. Workerd vs. Browser) using modern `environments` options instead of combining polyfills into a single global resolve alias.

Environment definitions inside `vite.config.ts` MUST declare explicit runtime capabilities (e.g., Node vs. Workerd vs. Browser) using modern `environments` options instead of combining polyfills into a single global resolve alias.

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

Custom execution runtimes MUST implement a dedicated `DevEnvironment` or `FetchableDevEnvironment` to maintain isolated evaluation contexts and prevent memory-space collision between client and server modules.

Custom execution runtimes MUST implement a dedicated `DevEnvironment` or `FetchableDevEnvironment` to maintain isolated evaluation contexts and prevent memory-space collision between client and server modules.

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

Engineers MUST NOT use deprecated `server.ssrTransform` or `server.ssrLoadModule`

Engineers MUST NOT use deprecated `server.ssrTransform` or `server.ssrLoadModule`; they MUST use `environment.transformRequest` and the environment's configured module runner.

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 Vite 6 Environment API Multi-Runtime Module Graph & HMR Boundary Enforcement critical for AI coding assistants?

Enforces strict isolation between heterogeneous runtime environments (client, node SSR, edge/workerd, and RSC) using the Vite 6 Environment API. Guarantees that module graphs, transform pipelines, and hot-module replacement (HMR) boundaries do not leak state or trigger invalid cross-runtime graph mutations across isolated execution contexts. 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 (Cross-Runtime Module Graph Contamination and Unscoped Legacy SSR Invalidation) 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.

Open Specification · CC BY 4.0·Free for Personal, Team & Commercial In-Repo Use

Citation & Open Source Attribution Guidelines

This specification is licensed under Creative Commons Attribution 4.0 International (CC BY 4.0). You are completely free to adapt and share this rule in your workspace. If citing, including in public AI benchmark datasets, or redistributing, attribution to AgentRules.org is required.

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