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frontendcritical PriorityID: vite6-environment-api-runtime-isolation-standard-vite-6-environme-917

Vite 6 Environment API Multi-Runtime Module Graph Isolation

Enforces strict physical separation of client, Node.js SSR, and edge worker module graphs using the Vite 6 Environment API. Prevents cross-runtime prototype pollution, execution context bleeding, and critical server secret exfiltration caused by shared module caches during universal bundling.

Prohibited Anti-Pattern: Monolithic SSR Module Graph Collapsing Client, Node, and Edge Execution Contexts

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---
description: Vite 6 Environment API Multi-Runtime Module Graph Isolation - Enforces strict physical separation of client, Node.js SSR, and edge worker module graphs using the Vite 6 Environment API. Prevents cross-runtime prototype pollution, execution context bleeding, and critical server secret exfiltration caused by shared module caches during universal bundling.
globs: vite.config.{ts,js,mjs}, src/**/*.{ts,tsx,js,jsx}, server/**/*.{ts,js}
alwaysApply: true
verified_by: "agentrules.org"
license: "CC-BY-4.0"
source: "https://agentrules.org/rules/vite6-environment-api-runtime-isolation-standard-vite-6-environme-917"
---

# Vite 6 Environment API Multi-Runtime Module Graph Isolation

> **Severity**: CRITICAL | **Category**: frontend
> **Anti-Pattern Warning**: Monolithic SSR Module Graph Collapsing Client, Node, and Edge Execution Contexts

## System Constraints
You are a Principal Software Architect enforcing the Vite 6 Environment API Multi-Runtime Module Graph Isolation Standard. Universal applications must never share a monolithic module graph or runtime evaluation context across client, Node.js, and Edge environments. Enforce distinct runtime definitions, isolated resolve conditions, per-environment plugin execution, and strict boundaries to prevent leakage of server secrets and runtime-specific globals into client or edge manifests.

## Strict Guidelines
- Configurations MUST define dedicated environments within `builder.environments` (e.g., `client`, `ssr`, and `edge`) rather than relying on legacy single-target SSR flags.
- Engineers MUST specify distinct `resolve.conditions` per runtime environment (e.g., `['browser']` for client, `['node', 'import']` for ssr, and `['workerd', 'worker']` for edge) to guarantee proper package export map selection.
- Engineers MUST NOT allow plugins with environment-specific side-effects to execute indiscriminately; plugins MUST utilize the `applyToEnvironment` hook or check `this.environment.name`.
- Client bundle entries MUST NEVER transitively resolve or import modules containing server-only identifiers or credentials; sensitive server keys MUST be isolated to the `ssr` or `edge` environment configurations.
- Code executed inside Edge worker environments MUST NOT import Node.js native built-ins (`node:fs`, `node:child_process`) or rely on Node-specific global singletons without polyfilled environment constraints.
- Shared utilities MUST remain pure and stateless; modules MUST NOT attach state to runtime globals (`globalThis`, `window`, or module-level mutable caches) that cross environment evaluation contexts during SSR compilation.

## Bad vs Good Implementations
### Legacy Vite SSR Monolithic Config vs Vite 6 Multi-Environment API

#### Bad Antipattern (AI Common Hallucination)
> **Why it fails**: Using a single build configuration with a dynamic SSR flag forces Vite to evaluate modules in a shared context. This easily exposes private server secrets through unified define replacements and fails to isolate edge/browser/node export conditions.
```typescript
// vite.config.ts (Vite 5 / Legacy pattern collapsing client and SSR into one module graph)
import { defineConfig } from 'vite';
import react from '@vitejs/plugin-react';

export default defineConfig({
  plugins: [react()],
  build: {
    // Single build target toggle causes module graph pollution and cross-runtime leaks
    ssr: process.env.IS_SSR ? 'src/entry-server.tsx' : false,
    outDir: process.env.IS_SSR ? 'dist/server' : 'dist/client'
  },
  define: {
    // Leaks private server configuration into shared define scope
    'process.env.INTERNAL_API_SECRET': JSON.stringify(process.env.INTERNAL_API_SECRET)
  }
});
```

#### Production Standard (Correct)
> **Standard**: Configures Vite 6 first-class runtime environments (`client`, `ssr`, `edge`) with independent resolution conditions, separate module graph compilation passes, and explicit per-environment plugin validations that block secret leakage.
```typescript
// vite.config.ts (Vite 6 Multi-Runtime Environment API Isolation)
import { defineConfig } from 'vite';
import react from '@vitejs/plugin-react';

export default defineConfig({
  environments: {
    client: {
      build: {
        outDir: 'dist/client',
        rollupOptions: {
          input: 'src/entry-client.tsx'
        }
      },
      resolve: {
        conditions: ['browser']
      }
    },
    ssr: {
      build: {
        outDir: 'dist/server',
        target: 'node20',
        rollupOptions: {
          input: 'src/entry-server.tsx'
        }
      },
      resolve: {
        conditions: ['node', 'import'],
        external: ['node:*']
      }
    },
    edge: {
      build: {
        outDir: 'dist/edge',
        target: 'esnext',
        rollupOptions: {
          input: 'src/entry-edge.ts'
        }
      },
      resolve: {
        conditions: ['workerd', 'worker']
      }
    }
  },
  plugins: [
    react(),
    {
      name: 'isolate-server-secrets',
      perEnvironmentStartEndDuringDev: true,
      transform(code, id) {
        if (this.environment.name === 'client' && code.includes('INTERNAL_API_SECRET')) {
          this.error(`Server secret referenced inside client module graph: ${id}`);
        }
      }
    }
  ]
});
```
Recommended MCP Servers (mcp-serverlist.com)

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

AST Inspection Engine
Parses Vite build outputs and bundle manifests to trace import trees and detect cross-runtime leakage.
Recommended Agent Skills (askills.dev)

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

Vite Bundle Environment Linter
CLI tool to verify that server and node built-in modules are completely absent from client build outputs.
Architectural Specification & Invariant Rationale

Architectural Invariant Design: Vite 6 Environment API Multi-Runtime Module Graph Isolation

Vite 6 Environment API Multi-Runtime Module Graph Isolation defines an industrial-grade behavioral standard for frontend engineering. Enforces strict physical separation of client, Node.js SSR, and edge worker module graphs using the Vite 6 Environment API. Prevents cross-runtime prototype pollution, execution context bleeding, and critical server secret exfiltration caused by shared module caches during universal bundling. 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: Monolithic SSR Module Graph Collapsing Client, Node, and Edge Execution Contexts 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 DriftMonolithic SSR Module Graph Collapsing Client, Node, and Edge Execution ContextsCritical
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

Configurations MUST define dedicated environments within `builder.environments` (e.g., `client`, `ssr`, and `edge`) rather than relying on legacy single-target SSR flags.

Configurations MUST define dedicated environments within `builder.environments` (e.g., `client`, `ssr`, and `edge`) rather than relying on legacy single-target SSR flags.

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 specify distinct `resolve.conditions` per runtime environment (e.g., `['browser']` for client, `['node', 'import']` for ssr, and `['workerd', 'worker']` for edge) to guarantee proper package export map selection.

Engineers MUST specify distinct `resolve.conditions` per runtime environment (e.g., `['browser']` for client, `['node', 'import']` for ssr, and `['workerd', 'worker']` for edge) to guarantee proper package export map selection.

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 NOT allow plugins with environment-specific side-effects to execute indiscriminately

Engineers MUST NOT allow plugins with environment-specific side-effects to execute indiscriminately; plugins MUST utilize the `applyToEnvironment` hook or check `this.environment.name`.

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

Client bundle entries MUST NEVER transitively resolve or import modules containing server-only identifiers or credentials

Client bundle entries MUST NEVER transitively resolve or import modules containing server-only identifiers or credentials; sensitive server keys MUST be isolated to the `ssr` or `edge` environment configurations.

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

Code executed inside Edge worker environments MUST NOT import Node.js native built-ins (`node

Code executed inside Edge worker environments MUST NOT import Node.js native built-ins (`node:fs`, `node:child_process`) or rely on Node-specific global singletons without polyfilled environment constraints.

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

Shared utilities MUST remain pure and stateless

Shared utilities MUST remain pure and stateless; modules MUST NOT attach state to runtime globals (`globalThis`, `window`, or module-level mutable caches) that cross environment evaluation contexts during SSR compilation.

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 Isolation critical for AI coding assistants?

Enforces strict physical separation of client, Node.js SSR, and edge worker module graphs using the Vite 6 Environment API. Prevents cross-runtime prototype pollution, execution context bleeding, and critical server secret exfiltration caused by shared module caches during universal bundling. 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 (Monolithic SSR Module Graph Collapsing Client, Node, and Edge Execution Contexts) 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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Citation & Open Source Attribution Guidelines

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