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frontendcritical PriorityID: vite-6-environment-api-runtime-module-isolation

Vite 6 Environment API Runtime Module Isolation and Cross-Graph Leakage Prevention

Mandates strict environment boundary isolation in Vite 6 multi-runtime module graphs (Browser, Node.js, and workerd). Enforces environment-scoped plugin hooks, explicit resolution conditions, and runtime boundary guards to eliminate cross-environment module pollution and hydration failures.

Prohibited Anti-Pattern: Leaking runtime-specific singletons, un-scoped plugin transforms, and incompatible native APIs across shared Vite 6 Environment graphs.

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---
description: Vite 6 Environment API Runtime Module Isolation and Cross-Graph Leakage Prevention - Mandates strict environment boundary isolation in Vite 6 multi-runtime module graphs (Browser, Node.js, and workerd). Enforces environment-scoped plugin hooks, explicit resolution conditions, and runtime boundary guards to eliminate cross-environment module pollution and hydration failures.
globs: vite.config.{ts,js,mjs}, plugins/**/*.{ts,js}, src/**/*.{ts,tsx,js,jsx}
alwaysApply: true
verified_by: "agentrules.org"
license: "CC-BY-4.0"
source: "https://agentrules.org/rules/vite-6-environment-api-runtime-module-isolation"
---

# Vite 6 Environment API Runtime Module Isolation and Cross-Graph Leakage Prevention

> **Severity**: CRITICAL | **Category**: frontend
> **Anti-Pattern Warning**: Leaking runtime-specific singletons, un-scoped plugin transforms, and incompatible native APIs across shared Vite 6 Environment graphs.

## System Constraints
You are a Principal Engineer enforcing Vite 6 Environment API Runtime Module Isolation. Mandate invariants that prevent cross-environment pollution between browser, workerd, and Node.js runtimes. Ensure plugins, resolver pipelines, and module transforms access environment-scoped metadata via `this.environment` rather than deprecated global flags or assumptions.

## Strict Guidelines
- Vite plugins MUST access `this.environment` within lifecycle hooks (`resolveId`, `load`, `transform`) instead of relying on legacy boolean flags like `options.ssr`.
- Engineers MUST configure distinct runtime boundaries under `environments` in `vite.config.ts` (e.g., `client`, `ssr`, `workerd`) with explicit `resolve.conditions` and `resolve.noExternal` rules.
- Custom plugins MUST NOT emit or resolve Node.js built-ins (`node:fs`, `node:path`) into environments targeting `client` or `workerd` runtimes.
- Shared isomorphic packages MUST declare runtime-specific export conditions in `package.json` matching the Vite 6 environment condition mapping (e.g., `workerd`, `browser`, `node`).
- Module-level singletons MUST NEVER be shared directly across Vite 6 DevEnvironments via global variables or shared Node `require` caches during development.
- Plugins extending module transforms MUST check `this.environment.name` before injecting runtime-specific shims or polyfills.

## Bad vs Good Implementations
### Vite 6 Plugin Environment Scoping vs. Legacy SSR Flag

#### Bad Antipattern (AI Common Hallucination)
> **Why it fails**: Using `options.ssr` collapses all non-browser environments into a single target, injecting Node.js APIs (like `process.pid`) into edge workers (like Cloudflare workerd), causing runtime crashes.
```typescript
import type { Plugin } from 'vite';

export function brokenRuntimePlugin(): Plugin {
  return {
    name: 'broken-runtime-plugin',
    resolveId(id, importer, options) {
      // VIOLATION: Using legacy options.ssr treats Node.js and workerd as identical runtimes
      if (options?.ssr && id === 'virtual:runtime-config') {
        return '\0node-runtime-config';
      }
      return null;
    },
    load(id) {
      if (id === '\0node-runtime-config') {
        // VIOLATION: Leaks Node.js specific process global into workerd/edge environments
        return `export const config = { pid: process.pid, cwd: process.cwd() };`;
      }
      return null;
    }
  };
}
```

#### Production Standard (Correct)
> **Standard**: Leverages `this.environment.name` in Vite 6 to uniquely identify the execution graph, generating strictly isolated modules for client, Node SSR, and workerd runtimes.
```typescript
import type { Plugin } from 'vite';

export function isolatedRuntimePlugin(): Plugin {
  return {
    name: 'isolated-runtime-plugin',
    resolveId(id) {
      if (id === 'virtual:runtime-config') {
        // GUARDS: Differentiate module graph resolution per Vite 6 Environment
        return `\0${this.environment.name}-runtime-config`;
      }
      return null;
    },
    load(id) {
      if (this.environment.name === 'ssr' && id === '\0ssr-runtime-config') {
        return `export const config = { runtime: 'node', pid: process.pid };`;
      }
      if (this.environment.name === 'workerd' && id === '\0workerd-runtime-config') {
        return `export const config = { runtime: 'workerd', edge: true };`;
      }
      if (this.environment.name === 'client' && id === '\0client-runtime-config') {
        return `export const config = { runtime: 'browser', edge: false };`;
      }
      return null;
    }
  };
}
```

### Vite 6 Multi-Environment Configuration

#### Bad Antipattern (AI Common Hallucination)
> **Why it fails**: Defining a global `ssr` config and top-level `resolve.conditions` poisons non-Node environments (like workerd or browser) with Node-first exports, triggering missing native dependency errors.
```typescript
import { defineConfig } from 'vite';

// VIOLATION: Single monolithic SSR configuration causing Workerd to inherit Node resolution
export default defineConfig({
  ssr: {
    target: 'node',
    noExternal: true,
  },
  resolve: {
    conditions: ['node', 'import']
  }
});
```

#### Production Standard (Correct)
> **Standard**: Defines explicit `environments` blocks in Vite 6, guaranteeing isolated resolve conditions and packaging constraints for client, Node SSR, and workerd runtime module graphs.
```typescript
import { defineConfig } from 'vite';

// ENFORCED: Explicit Vite 6 Environment API runtime definitions
export default defineConfig({
  environments: {
    client: {
      build: { outDir: 'dist/client' },
      resolve: { conditions: ['browser', 'import'] }
    },
    ssr: {
      build: { outDir: 'dist/server' },
      resolve: {
        conditions: ['node', 'import'],
        externalConditions: ['node']
      }
    },
    workerd: {
      build: { outDir: 'dist/edge' },
      resolve: {
        conditions: ['workerd', 'worker', 'browser'],
        noExternal: true
      }
    }
  }
});
```
Recommended MCP Servers (mcp-serverlist.com)

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

Filesystem MCP Server
Inspect and validate project directory structures, package.json export conditions, and Vite 6 config definitions.
Recommended Agent Skills (askills.dev)

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

Vite Environment Graph Auditor
CLI verification tool to audit cross-environment imports and validate resolution pipelines across Vite 6 environments.
Architectural Specification & Invariant Rationale

Architectural Invariant Design: Vite 6 Environment API Runtime Module Isolation and Cross-Graph Leakage Prevention

Vite 6 Environment API Runtime Module Isolation and Cross-Graph Leakage Prevention defines an industrial-grade behavioral standard for frontend engineering. Mandates strict environment boundary isolation in Vite 6 multi-runtime module graphs (Browser, Node.js, and workerd). Enforces environment-scoped plugin hooks, explicit resolution conditions, and runtime boundary guards to eliminate cross-environment module pollution and hydration failures. 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: Leaking runtime-specific singletons, un-scoped plugin transforms, and incompatible native APIs across shared Vite 6 Environment graphs. 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 DriftLeaking runtime-specific singletons, un-scoped plugin transforms, and incompatible native APIs across shared Vite 6 Environment graphs.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

Vite plugins MUST access `this.environment` within lifecycle hooks (`resolveId`, `load`, `transform`) instead of relying on legacy boolean flags like `options.ssr`.

Vite plugins MUST access `this.environment` within lifecycle hooks (`resolveId`, `load`, `transform`) instead of relying on legacy boolean flags like `options.ssr`.

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 configure distinct runtime boundaries under `environments` in `vite.config.ts` (e.g., `client`, `ssr`, `workerd`) with explicit `resolve.conditions` and `resolve.noExternal` rules.

Engineers MUST configure distinct runtime boundaries under `environments` in `vite.config.ts` (e.g., `client`, `ssr`, `workerd`) with explicit `resolve.conditions` and `resolve.noExternal` rules.

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

Custom plugins MUST NOT emit or resolve Node.js built-ins (`node

Custom plugins MUST NOT emit or resolve Node.js built-ins (`node:fs`, `node:path`) into environments targeting `client` or `workerd` runtimes.

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

Shared isomorphic packages MUST declare runtime-specific export conditions in `package.json` matching the Vite 6 environment condition mapping (e.g., `workerd`, `browser`, `node`).

Shared isomorphic packages MUST declare runtime-specific export conditions in `package.json` matching the Vite 6 environment condition mapping (e.g., `workerd`, `browser`, `node`).

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

Module-level singletons MUST NEVER be shared directly across Vite 6 DevEnvironments via global variables or shared Node `require` caches during development.

Module-level singletons MUST NEVER be shared directly across Vite 6 DevEnvironments via global variables or shared Node `require` caches during development.

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

Plugins extending module transforms MUST check `this.environment.name` before injecting runtime-specific shims or polyfills.

Plugins extending module transforms MUST check `this.environment.name` before injecting runtime-specific shims or polyfills.

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 Runtime Module Isolation and Cross-Graph Leakage Prevention critical for AI coding assistants?

Mandates strict environment boundary isolation in Vite 6 multi-runtime module graphs (Browser, Node.js, and workerd). Enforces environment-scoped plugin hooks, explicit resolution conditions, and runtime boundary guards to eliminate cross-environment module pollution and hydration failures. 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 (Leaking runtime-specific singletons, un-scoped plugin transforms, and incompatible native APIs across shared Vite 6 Environment graphs.) 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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