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frontendcritical PriorityID: vite6-environment-api-runtime-isolation-standard-vite-6-environme-794

Vite 6 Environment API Runtime Isolation and Module Graph Segregation

Mandates strict runtime module graph isolation between heterogeneous client, edge, and server environments using the Vite 6 Environment API. Enforces separate resolution conditions and environment-scoped plugin hooks to prevent cross-runtime global pollution, token leakage, and SSR hydration corruption.

Prohibited Anti-Pattern: Monolithic Legacy SSR Configuration and Cross-Environment Module Graph Bleed

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---
description: Vite 6 Environment API Runtime Isolation and Module Graph Segregation - Mandates strict runtime module graph isolation between heterogeneous client, edge, and server environments using the Vite 6 Environment API. Enforces separate resolution conditions and environment-scoped plugin hooks to prevent cross-runtime global pollution, token leakage, and SSR hydration corruption.
globs: vite.config.{ts,js,mjs}, src/**/*.{ts,tsx}, server/**/*.{ts,tsx}
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-794"
---

# Vite 6 Environment API Runtime Isolation and Module Graph Segregation

> **Severity**: CRITICAL | **Category**: frontend
> **Anti-Pattern Warning**: Monolithic Legacy SSR Configuration and Cross-Environment Module Graph Bleed

## System Constraints
You are a Principal Software Architect enforcing the Vite 6 Environment API Runtime Isolation Standard. You must ensure that applications operating heterogeneous runtimes (browser DOM, Node.js SSR, Edge/Workerd workers) strictly partition their compilation and execution contexts. Reject monolithic SSR flags, legacy server.moduleGraph mutations, unscoped plugin transforms, and shared global state across environment boundaries.

## Strict Guidelines
- Engineers MUST ALWAYS configure distinct execution targets via top-level `environments` in `vite.config.ts`, specifying separate `resolve.conditions` (e.g., `browser`, `node`, `workerd`) for each runtime.
- Engineers MUST NOT access `server.moduleGraph` directly inside Vite plugins; all module resolution, invalidation, and inspection MUST be scoped via `this.environment.moduleGraph` or `server.environments[name].moduleGraph`.
- Code SHOULD utilize Vite 6 `ModuleRunner` or environment-specific dev runtimes instead of deprecated legacy `server.ssrLoadModule` when evaluating non-Node or heterogeneous code graphs.
- Services MUST NEVER mutate `globalThis` or rely on cross-request module singletons during SSR or edge execution, ensuring deterministic hydration data serialization without runtime cross-talk.
- Components NEVER import environment-specific entry points directly across runtime boundaries; all conditional imports MUST be resolved via environment-scoped subpath imports or dedicated virtual module contracts.

## Bad vs Good Implementations
### Configuring Environment API vs Legacy Monolithic SSR Hook

#### Bad Antipattern (AI Common Hallucination)
> **Why it fails**: Legacy Vite SSR configurations treat the build as a binary client/ssr dichotomy. Mutating `server.moduleGraph` indiscriminately flushes both client and server graphs, and binary `options.ssr` checks cannot safely isolate distinct environments (such as Node vs. Workerd edge runtimes), leading to environment pollution and hydration state corruption.
```typescript
import { defineConfig } from 'vite';

export default defineConfig({
  // Anti-pattern: Legacy dual-mode config mixing edge and server invariants
  ssr: {
    target: 'webworker',
    noExternal: true,
  },
  plugins: [{
    name: 'leaky-ssr-plugin',
    handleHotUpdate({ server, modules }) {
      // Flaw: Mutates the global dev server root module graph directly,
      // causing invalidation cascade collisions between client and SSR.
      server.moduleGraph.invalidateAll();
    },
    transform(code, id, options) {
      // Flaw: Binary boolean fails to differentiate between Node, Edge, and Worklets
      if (options?.ssr) {
        return code.replace('__TARGET__', JSON.stringify(process.env.RUNTIME_TARGET));
      }
      return code;
    },
  }],
});
```

#### Production Standard (Correct)
> **Standard**: The Vite 6 Environment API explicitly delineates runtime boundaries (`client`, `ssr`, `edge`) with dedicated resolution conditions. Plugins leverage `this.environment` to isolate module graph mutations and transformations to the execution target currently being processed, preventing cross-environment pollution.
```typescript
import { defineConfig } from 'vite';

export default defineConfig({
  // Invariant: Declare explicit runtime isolation via Vite 6 Environment API
  environments: {
    client: {
      build: { outDir: 'dist/client' },
      resolve: { conditions: ['browser'] },
    },
    ssr: {
      build: { outDir: 'dist/server' },
      resolve: { conditions: ['node', 'import'] },
    },
    edge: {
      resolve: {
        conditions: ['workerd', 'worker'],
        noExternal: true,
      },
    },
  },
  plugins: [{
    name: 'isolated-environment-plugin',
    hotUpdate({ modules }) {
      // Invariant: Scope invalidation strictly to the active DevEnvironment module graph
      for (const mod of modules) {
        this.environment.moduleGraph.invalidateModule(mod);
      }
    },
    transform(code, id) {
      // Invariant: Explicitly condition behaviors based on environment name
      if (this.environment.name === 'edge') {
        return code.replace('__TARGET__', '"workerd"');
      }
      if (this.environment.name === 'client') {
        return code.replace('__TARGET__', '"browser"');
      }
      return code;
    },
  }],
});
```
Recommended MCP Servers (mcp-serverlist.com)

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

Vite Environment Inspector MCP
Inspects Vite 6 runtime environment graphs, active module runners, and resolve conditions across client and server environments.
Recommended Agent Skills (askills.dev)

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

Vite Environment Verification CLI
CLI utility to lint Vite 6 configuration files for unpartitioned SSR graphs and deprecated ssrLoadModule invocations.
Architectural Specification & Invariant Rationale

Architectural Invariant Design: Vite 6 Environment API Runtime Isolation and Module Graph Segregation

Vite 6 Environment API Runtime Isolation and Module Graph Segregation defines an industrial-grade behavioral standard for frontend engineering. Mandates strict runtime module graph isolation between heterogeneous client, edge, and server environments using the Vite 6 Environment API. Enforces separate resolution conditions and environment-scoped plugin hooks to prevent cross-runtime global pollution, token leakage, and SSR hydration corruption. 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 Legacy SSR Configuration and Cross-Environment Module Graph Bleed 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 Legacy SSR Configuration and Cross-Environment Module Graph BleedCritical
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 configure distinct execution targets via top-level `environments` in `vite.config.ts`, specifying separate `resolve.conditions` (e.g., `browser`, `node`, `workerd`) for each runtime.

Engineers MUST ALWAYS configure distinct execution targets via top-level `environments` in `vite.config.ts`, specifying separate `resolve.conditions` (e.g., `browser`, `node`, `workerd`) for each runtime.

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 `server.moduleGraph` directly inside Vite plugins

Engineers MUST NOT access `server.moduleGraph` directly inside Vite plugins; all module resolution, invalidation, and inspection MUST be scoped via `this.environment.moduleGraph` or `server.environments[name].moduleGraph`.

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 SHOULD utilize Vite 6 `ModuleRunner` or environment-specific dev runtimes instead of deprecated legacy `server.ssrLoadModule` when evaluating non-Node or heterogeneous code graphs.

Code SHOULD utilize Vite 6 `ModuleRunner` or environment-specific dev runtimes instead of deprecated legacy `server.ssrLoadModule` when evaluating non-Node or heterogeneous code graphs.

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 NEVER mutate `globalThis` or rely on cross-request module singletons during SSR or edge execution, ensuring deterministic hydration data serialization without runtime cross-talk.

Services MUST NEVER mutate `globalThis` or rely on cross-request module singletons during SSR or edge execution, ensuring deterministic hydration data serialization without runtime cross-talk.

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 import environment-specific entry points directly across runtime boundaries

Components NEVER import environment-specific entry points directly across runtime boundaries; all conditional imports MUST be resolved via environment-scoped subpath imports or dedicated virtual module contracts.

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 Isolation and Module Graph Segregation critical for AI coding assistants?

Mandates strict runtime module graph isolation between heterogeneous client, edge, and server environments using the Vite 6 Environment API. Enforces separate resolution conditions and environment-scoped plugin hooks to prevent cross-runtime global pollution, token leakage, and SSR hydration corruption. 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 Legacy SSR Configuration and Cross-Environment Module Graph Bleed) 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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Vite