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frontendcritical PriorityID: vite6-environment-api-runtime-decoupling

Vite 6 Environment API: Multi-Runtime Module Decoupling and Graph Isolation

Enforces strict boundary isolation and dedicated compilation graphs across client, Node.js, and workerd/edge runtimes using the Vite 6 Environment API. Prevents runtime-specific polyfill bleeding, Node.js built-in leakage into edge/browser bundles, and illegal cross-environment module graph invalidations in hybrid SSR architectures.

Prohibited Anti-Pattern: Monolithic ModuleGraph Sharing and Legacy SSR Flag Branching Leaking Runtime Globals

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---
description: Vite 6 Environment API: Multi-Runtime Module Decoupling and Graph Isolation - Enforces strict boundary isolation and dedicated compilation graphs across client, Node.js, and workerd/edge runtimes using the Vite 6 Environment API. Prevents runtime-specific polyfill bleeding, Node.js built-in leakage into edge/browser bundles, and illegal cross-environment module graph invalidations in hybrid SSR architectures.
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-decoupling"
---

# Vite 6 Environment API: Multi-Runtime Module Decoupling and Graph Isolation

> **Severity**: CRITICAL | **Category**: frontend
> **Anti-Pattern Warning**: Monolithic ModuleGraph Sharing and Legacy SSR Flag Branching Leaking Runtime Globals

## System Constraints
You are a Principal Software Architect enforcing runtime-isolated compilation graphs via the Vite 6 Environment API. You must reject any legacy `ssr: boolean` pattern, enforce per-environment resolution conditions, and ensure that Cloudflare Workerd, Node.js SSR, and Client bundles maintain fully partitioned module graphs to prevent polyfill contamination.

## Strict Guidelines
- Engineers MUST ALWAYS declare isolated execution targets via `environments.<name>` in Vite 6, explicitly specifying `resolve.conditions` and `consumer` types (e.g., 'server' vs 'client').
- Engineers MUST NOT rely on deprecated `ssr` boolean options in plugins or configuration (`config.ssr`, `transform(code, id, { ssr })`); they MUST use `this.environment.name` to scope plugin logic.
- Code executing in Edge/Workerd environments MUST NOT import Node.js native built-ins (`node:fs`, `node:child_process`) or rely on Node.js global polyfills that contaminate the shared execution context.
- Vite plugins MUST scope transform hooks, module resolutions, and invalidations directly to `this.environment.moduleGraph` instead of mutating the root dev server graph.
- Hybrid architectures MUST configure distinct dev runtimes per environment, utilizing `RunnableDevEnvironment` or `FetchableDevEnvironment` to match targeted production primitives.

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

#### Bad Antipattern (AI Common Hallucination)
> **Why it fails**: Legacy configurations collapse all server targets into a single SSR context. This causes browser and workerd environments to inherit Node.js conditions, resulting in Node polyfills leaking into edge targets or edge-specific web standards crashing Node SSR.
```typescript
import { defineConfig } from 'vite';

// ANTI-PATTERN: Monolithic configuration with shared resolve conditions and legacy SSR boolean
export default defineConfig({
  ssr: {
    noExternal: true,
    target: 'webworker', // Forces the entire SSR build into a single flawed runtime paradigm
  },
  plugins: [{
    name: 'runtime-logger',
    transform(code, id, options) {
      // Flawed legacy detection prone to cross-compilation leakage
      if (options?.ssr) {
        return code.replace('__ENV__', JSON.stringify('server'));
      }
      return code.replace('__ENV__', JSON.stringify('client'));
    }
  }]
});
```

#### Production Standard (Correct)
> **Standard**: Uses the Vite 6 Environment API to separate 'client', 'ssr' (Node.js), and 'edge' (Workerd) into isolated module graphs with dedicated resolution conditions, halting cross-environment polyfill pollution at compilation time.
```typescript
import { defineConfig } from 'vite';

// PRODUCTION STANDARD: Vite 6 isolated Environment API with strict boundary control
export default defineConfig({
  environments: {
    client: {
      build: { outDir: 'dist/client' },
      resolve: { conditions: ['browser'] },
    },
    ssr: {
      build: { outDir: 'dist/ssr' },
      resolve: { conditions: ['node'] },
      consumer: 'server',
    },
    edge: {
      build: { outDir: 'dist/edge' },
      resolve: { conditions: ['workerd', 'worker'] },
      consumer: 'server',
    },
  },
  plugins: [{
    name: 'environment-aware-resolver',
    transform(code, id) {
      // Strictly isolate behavior by inspecting the explicit active environment
      const currentRuntime = this.environment.name;
      if (currentRuntime === 'edge') {
        if (id.includes('node:fs') || id.includes('node:child_process')) {
          this.error(`Forbidden Node.js native import '${id}' in Edge environment.`);
        }
      }
      return code.replace('__RUNTIME_NAME__', JSON.stringify(currentRuntime));
    }
  }]
});
```
Recommended MCP Servers (mcp-serverlist.com)

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

Vite Environment Inspector MCP
Validates active module graphs and environment runtimes in Vite dev servers.
Recommended Agent Skills (askills.dev)

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

Vite AST Module Graph Analyzer
CLI skill to audit Vite 6 build chunks and assert runtime isolation between Workerd, Node, and Client output.
Architectural Specification & Invariant Rationale

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

Vite 6 Environment API: Multi-Runtime Module Decoupling and Graph Isolation defines an industrial-grade behavioral standard for frontend engineering. Enforces strict boundary isolation and dedicated compilation graphs across client, Node.js, and workerd/edge runtimes using the Vite 6 Environment API. Prevents runtime-specific polyfill bleeding, Node.js built-in leakage into edge/browser bundles, and illegal cross-environment module graph invalidations in hybrid SSR architectures. 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 ModuleGraph Sharing and Legacy SSR Flag Branching Leaking Runtime Globals 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 ModuleGraph Sharing and Legacy SSR Flag Branching Leaking Runtime GlobalsCritical
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 execution targets via `environments.<name>` in Vite 6, explicitly specifying `resolve.conditions` and `consumer` types (e.g., 'server' vs 'client').

Engineers MUST ALWAYS declare isolated execution targets via `environments.<name>` in Vite 6, explicitly specifying `resolve.conditions` and `consumer` types (e.g., 'server' vs 'client').

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 rely on deprecated `ssr` boolean options in plugins or configuration (`config.ssr`, `transform(code, id, { ssr })`)

Engineers MUST NOT rely on deprecated `ssr` boolean options in plugins or configuration (`config.ssr`, `transform(code, id, { ssr })`); they MUST use `this.environment.name` to scope plugin logic.

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 executing in Edge/Workerd environments MUST NOT import Node.js native built-ins (`node

Code executing in Edge/Workerd environments MUST NOT import Node.js native built-ins (`node:fs`, `node:child_process`) or rely on Node.js global polyfills that contaminate the shared execution context.

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

Vite plugins MUST scope transform hooks, module resolutions, and invalidations directly to `this.environment.moduleGraph` instead of mutating the root dev server graph.

Vite plugins MUST scope transform hooks, module resolutions, and invalidations directly to `this.environment.moduleGraph` instead of mutating the root dev server graph.

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

Hybrid architectures MUST configure distinct dev runtimes per environment, utilizing `RunnableDevEnvironment` or `FetchableDevEnvironment` to match targeted production primitives.

Hybrid architectures MUST configure distinct dev runtimes per environment, utilizing `RunnableDevEnvironment` or `FetchableDevEnvironment` to match targeted production primitives.

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 Decoupling and Graph Isolation critical for AI coding assistants?

Enforces strict boundary isolation and dedicated compilation graphs across client, Node.js, and workerd/edge runtimes using the Vite 6 Environment API. Prevents runtime-specific polyfill bleeding, Node.js built-in leakage into edge/browser bundles, and illegal cross-environment module graph invalidations in hybrid SSR architectures. 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 ModuleGraph Sharing and Legacy SSR Flag Branching Leaking Runtime Globals) 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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