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frontendcritical PriorityID: vite-6-environment-api-boundary-enforcement

Vite 6 Environment API Multi-Runtime Module Boundary Guardrails

Enforces strict module separation across client DOM, Node.js SSR, and Edge Worker compilation environments using the Vite 6 Environment API. Prevents runtime-specific symbol leaks, illegal module graph bridging, and non-deterministic tree-shaking failures across disparate execution targets.

Prohibited Anti-Pattern: Cross-Runtime Symbol Contamination via Shared Module Graphs and Permissive Conditional Resolvers

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---
description: Vite 6 Environment API Multi-Runtime Module Boundary Guardrails - Enforces strict module separation across client DOM, Node.js SSR, and Edge Worker compilation environments using the Vite 6 Environment API. Prevents runtime-specific symbol leaks, illegal module graph bridging, and non-deterministic tree-shaking failures across disparate execution targets.
globs: vite.config.ts, vite.config.*.ts, src/**/*.{ts,tsx,js,jsx}, server/**/*.{ts,js}, worker/**/*.{ts,js}
alwaysApply: true
verified_by: "agentrules.org"
license: "CC-BY-4.0"
source: "https://agentrules.org/rules/vite-6-environment-api-boundary-enforcement"
---

# Vite 6 Environment API Multi-Runtime Module Boundary Guardrails

> **Severity**: CRITICAL | **Category**: frontend
> **Anti-Pattern Warning**: Cross-Runtime Symbol Contamination via Shared Module Graphs and Permissive Conditional Resolvers

## System Constraints
You are a Principal Software Architect enforcing runtime separation invariants under Vite 6's Environment API. You must mandate strict isolation among 'client', 'ssr' (Node.js), and 'edge' (Worker) environments, preventing runtime pollution, invalid globals, and cross-boundary re-exports.

## Strict Guidelines
- Engineers MUST ALWAYS declare isolated runtime environments explicitly under `environments` in `vite.config.ts` using `createRunnableDevEnvironment` or custom `EnvironmentOptions`.
- Engineers MUST NOT import Node.js built-ins (`fs`, `path`, `crypto`, `buffer`) or Node-only NPM modules into shared or client/edge environment subgraphs.
- Code MUST isolate environment-specific code via package subpath exports with designated conditions (e.g., 'worker', 'node', 'browser') rather than relying on dynamic runtime inspection (`typeof window !== 'undefined'`).
- Services MUST route environment plugins via the `applyToEnvironment(environment)` hook or environment-scoped plugin configuration to prevent cross-graph transform leakage.
- Components NEVER directly bind Edge Worker globals (`KVNamespace`, `DurableObjectState`) or Node.js primitives (`AsyncLocalStorage`) inside isomorphic or client-rendered templates.

## Bad vs Good Implementations
### Vite 6 Multi-Environment Configuration Boundary

#### Bad Antipattern (AI Common Hallucination)
> **Why it fails**: Configuring SSR globally via legacy `ssr` block collapses the compilation graph. Client, Node.js SSR, and Edge Worker runtimes share condition resolution, allowing Node-specific shims or Edge globals to leak into unrelated bundles.
```typescript
import { defineConfig } from 'vite';

// ANTI-PATTERN: Vite 5 legacy single-target SSR configuration
// Leaks Node.js SSR plugins and resolution settings into edge/client paths
export default defineConfig({
  ssr: {
    noExternal: ['shared-lib'],
    target: 'node',
  },
  define: {
    'process.env.IS_EDGE': JSON.stringify(false),
  },
  resolve: {
    conditions: ['node', 'browser'],
  },
});
```

#### Production Standard (Correct)
> **Standard**: Defines discrete compilation environments with specialized condition sets and consumer roles. Each target compiles via its own module graph pipeline, preventing shared dependency contamination.
```typescript
import { defineConfig } from 'vite';

// PRODUCTION INVARIANT: Vite 6 isolated Environment API definitions
export default defineConfig({
  environments: {
    client: {
      consumer: 'client',
      build: { outDir: 'dist/client' },
      resolve: { conditions: ['browser'] },
    },
    ssr: {
      consumer: 'server',
      build: { outDir: 'dist/server', target: 'node20' },
      resolve: { conditions: ['node', 'import'] },
    },
    edge: {
      consumer: 'server',
      build: { outDir: 'dist/edge', target: 'esnext' },
      resolve: { conditions: ['worker', 'edge-light', 'import'] },
    },
  },
  builder: {
    buildApp: async (builder) => {
      await builder.build(builder.environments.client);
      await builder.build(builder.environments.ssr);
      await builder.build(builder.environments.edge);
    },
  },
});
```

### Runtime-Safe Capability Access vs Global Leaks

#### Bad Antipattern (AI Common Hallucination)
> **Why it fails**: Static imports of runtime-specific modules (`node:fs`) fail during build steps in client and edge graphs, even when gated by conditional runtime checks.
```typescript
import fs from 'node:fs';

// ANTI-PATTERN: Node API directly referenced in shared entrypoint
export function readPlatformAsset(path: string): string | ArrayBuffer {
  if (typeof window !== 'undefined') {
    throw new Error('Cannot run in browser');
  }
  // Breaks compilation on Edge runtime and leaks Node types into DOM compilation
  return fs.readFileSync(path, 'utf-8');
}
```

#### Production Standard (Correct)
> **Standard**: Decouples implementations through module boundaries mapped to export conditions. Each target resolves its distinct implementation without static runtime symbol leakage.
```typescript
// File: src/platform/storage.ts (isomorphic contract)
export interface PlatformStorage {
  readAsset(path: string): Promise<Uint8Array>;
}

// File: src/platform/storage.node.ts (Node SSR target)
import { readFile } from 'node:fs/promises';
import type { PlatformStorage } from './storage';

export const storage: PlatformStorage = {
  readAsset: async (path: string) => {
    const buf = await readFile(path);
    return new Uint8Array(buf.buffer, buf.byteOffset, buf.byteLength);
  },
};

// File: src/platform/storage.edge.ts (Edge Worker target)
import type { PlatformStorage } from './storage';

declare const ASSETS_BINDING: { get: (k: string, t: 'arrayBuffer') => Promise<ArrayBuffer | null> };

export const storage: PlatformStorage = {
  readAsset: async (path: string) => {
    const buf = await ASSETS_BINDING.get(path, 'arrayBuffer');
    if (!buf) throw new Error(`Not found: ${path}`);
    return new Uint8Array(buf);
  },
};
```
Recommended MCP Servers (mcp-serverlist.com)

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

Vite Environment Inspector MCP
Analyzes active Vite 6 environments, module graphs, and export condition resolution pathways across targets.
Recommended Agent Skills (askills.dev)

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

Vite Environment Boundary Checker
Validates package.json exports conditions and flags runtime-specific imports in cross-environment modules.
Architectural Specification & Invariant Rationale

Architectural Invariant Design: Vite 6 Environment API Multi-Runtime Module Boundary Guardrails

Vite 6 Environment API Multi-Runtime Module Boundary Guardrails defines an industrial-grade behavioral standard for frontend engineering. Enforces strict module separation across client DOM, Node.js SSR, and Edge Worker compilation environments using the Vite 6 Environment API. Prevents runtime-specific symbol leaks, illegal module graph bridging, and non-deterministic tree-shaking failures across disparate execution targets. 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 Symbol Contamination via Shared Module Graphs and Permissive Conditional Resolvers 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 Symbol Contamination via Shared Module Graphs and Permissive Conditional ResolversCritical
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 declare isolated runtime environments explicitly under `environments` in `vite.config.ts` using `createRunnableDevEnvironment` or custom `EnvironmentOptions`.

Engineers MUST ALWAYS declare isolated runtime environments explicitly under `environments` in `vite.config.ts` using `createRunnableDevEnvironment` or custom `EnvironmentOptions`.

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 import Node.js built-ins (`fs`, `path`, `crypto`, `buffer`) or Node-only NPM modules into shared or client/edge environment subgraphs.

Engineers MUST NOT import Node.js built-ins (`fs`, `path`, `crypto`, `buffer`) or Node-only NPM modules into shared or client/edge environment subgraphs.

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 MUST isolate environment-specific code via package subpath exports with designated conditions (e.g., 'worker', 'node', 'browser') rather than relying on dynamic runtime inspection (`typeof window !== 'undefined'`).

Code MUST isolate environment-specific code via package subpath exports with designated conditions (e.g., 'worker', 'node', 'browser') rather than relying on dynamic runtime inspection (`typeof window !== 'undefined'`).

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

Services MUST route environment plugins via the `applyToEnvironment(environment)` hook or environment-scoped plugin configuration to prevent cross-graph transform leakage.

Services MUST route environment plugins via the `applyToEnvironment(environment)` hook or environment-scoped plugin configuration to prevent cross-graph transform leakage.

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 directly bind Edge Worker globals (`KVNamespace`, `DurableObjectState`) or Node.js primitives (`AsyncLocalStorage`) inside isomorphic or client-rendered templates.

Components NEVER directly bind Edge Worker globals (`KVNamespace`, `DurableObjectState`) or Node.js primitives (`AsyncLocalStorage`) inside isomorphic or client-rendered templates.

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 Boundary Guardrails critical for AI coding assistants?

Enforces strict module separation across client DOM, Node.js SSR, and Edge Worker compilation environments using the Vite 6 Environment API. Prevents runtime-specific symbol leaks, illegal module graph bridging, and non-deterministic tree-shaking failures across disparate execution targets. 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 Symbol Contamination via Shared Module Graphs and Permissive Conditional Resolvers) 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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