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frontendcritical PriorityID: vite6-environment-runtime-isolation

Vite 6 Environment API Deterministic Runtime Boundary Isolation

Enforces deterministic module resolution boundaries and isolated module graphs across distinct Vite 6 execution contexts (browser, Node.js SSR, and edge/workerd runtimes). Prevents runtime leakage, cross-environment cache contamination, and invalid export condition resolution in multi-target architectures.

Prohibited Anti-Pattern: Global Resolution Bleed and Cross-Runtime Module Graph Contamination

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---
description: Vite 6 Environment API Deterministic Runtime Boundary Isolation - Enforces deterministic module resolution boundaries and isolated module graphs across distinct Vite 6 execution contexts (browser, Node.js SSR, and edge/workerd runtimes). Prevents runtime leakage, cross-environment cache contamination, and invalid export condition resolution in multi-target architectures.
globs: vite.config.ts, vite.config.*.ts, src/**/*.{ts,tsx}
alwaysApply: true
verified_by: "agentrules.org"
license: "CC-BY-4.0"
source: "https://agentrules.org/rules/vite6-environment-runtime-isolation"
---

# Vite 6 Environment API Deterministic Runtime Boundary Isolation

> **Severity**: CRITICAL | **Category**: frontend
> **Anti-Pattern Warning**: Global Resolution Bleed and Cross-Runtime Module Graph Contamination

## System Constraints
You are a Principal Software Architect enforcing strict module resolution boundaries and runtime isolation via the Vite 6 Environment API. You must reject legacy top-level SSR hacks, enforce discrete module graph partitions, isolate runtime resolve conditions across worker/node/browser contexts, and ensure plugins bind strictly to their intended environment lifecycle.

## Strict Guidelines
- Engineers MUST ALWAYS configure distinct execution targets using Vite 6 `environments` definitions (e.g., `client`, `ssr`, `edge`) instead of legacy top-level `ssr` and global `resolve.conditions`.
- Engineers MUST NOT leak Node.js built-ins, browser globals, or edge runtime APIs across distinct environment boundaries via shared top-level plugin transforms or global aliasing.
- Vite plugins MUST implement `applyToEnvironment(env)` or check `env.name` to ensure transformation passes and resolve hooks only execute within their intended runtime context.
- Edge and worker environments MUST declare target-specific `resolve.conditions` (e.g., `['worker', 'workerd', 'edge-light']`) and explicitly set `noExternal: true` to prevent Node.js module resolution leakage.
- Server runners and middleware MUST access environment-specific module graphs via `server.environments[name].moduleGraph` rather than relying on the legacy shared `server.moduleGraph`.

## Bad vs Good Implementations
### Legacy Shared SSR Config vs Vite 6 Isolated Environments Configuration

#### Bad Antipattern (AI Common Hallucination)
> **Why it fails**: Global resolution conditions cause browser and node bundles to resolve export conditions intended solely for edge workers. Top-level plugins execute globally across all execution contexts, polluting module caches and leaking invalid runtime primitives.
```typescript
import { defineConfig } from 'vite';

// ANTI-PATTERN: Vite 5 legacy config mixing Node SSR and Edge contexts globally
export default defineConfig({
  resolve: {
    // Leaks worker conditions into the browser and Node bundles
    conditions: ['worker', 'browser'],
  },
  ssr: {
    // Ambiguous target: fails when deploying edge worker along with node SSR
    target: 'node',
    noExternal: ['shared-ui'],
  },
  plugins: [
    {
      name: 'platform-transform',
      // Runs indiscriminately across all bundles causing runtime cross-contamination
      transform(code, id) {
        if (id.includes('runtime-entry')) {
          return code.replace('__RUNTIME__', JSON.stringify(process.env.RUNTIME));
        }
      },
    },
  ],
});
```

#### Production Standard (Correct)
> **Standard**: Defines isolated environment configurations using the Vite 6 Environment API. Module resolution conditions (`browser`, `node`, `worker`) are segregated per target, and plugin transformations are strictly restricted to their designated execution environment using `applyToEnvironment`.
```typescript
import { defineConfig } from 'vite';

// PRODUCTION STANDARD: Vite 6 Environment API with deterministic isolation
export default defineConfig({
  environments: {
    client: {
      consumer: 'client',
      resolve: {
        conditions: ['browser'],
      },
    },
    ssr: {
      consumer: 'server',
      resolve: {
        conditions: ['node'],
        external: true,
      },
    },
    edge: {
      consumer: 'server',
      resolve: {
        conditions: ['worker', 'workerd', 'edge-light'],
        noExternal: true,
      },
    },
  },
  plugins: [
    {
      name: 'platform-transform',
      // Explicitly scoped to the edge environment module graph
      applyToEnvironment(environment) {
        return environment.name === 'edge';
      },
      transform(code, id) {
        if (id.includes('runtime-entry')) {
          return code.replace('__RUNTIME__', JSON.stringify('workerd'));
        }
      },
    },
  ],
});
```
Recommended MCP Servers (mcp-serverlist.com)

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

Filesystem MCP Server
Inspects Vite configuration files and multi-environment entry files across client, SSR, and edge subtrees.
Recommended Agent Skills (askills.dev)

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

Vite Environment Build Validator
Validates that all configured Vite 6 environment module graphs pass dry-run resolution without cross-runtime leaks.
Architectural Specification & Invariant Rationale

Architectural Invariant Design: Vite 6 Environment API Deterministic Runtime Boundary Isolation

Vite 6 Environment API Deterministic Runtime Boundary Isolation defines an industrial-grade behavioral standard for frontend engineering. Enforces deterministic module resolution boundaries and isolated module graphs across distinct Vite 6 execution contexts (browser, Node.js SSR, and edge/workerd runtimes). Prevents runtime leakage, cross-environment cache contamination, and invalid export condition resolution in multi-target 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: Global Resolution Bleed and Cross-Runtime Module Graph Contamination 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 DriftGlobal Resolution Bleed and Cross-Runtime Module Graph ContaminationCritical
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 using Vite 6 `environments` definitions (e.g., `client`, `ssr`, `edge`) instead of legacy top-level `ssr` and global `resolve.conditions`.

Engineers MUST ALWAYS configure distinct execution targets using Vite 6 `environments` definitions (e.g., `client`, `ssr`, `edge`) instead of legacy top-level `ssr` and global `resolve.conditions`.

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 leak Node.js built-ins, browser globals, or edge runtime APIs across distinct environment boundaries via shared top-level plugin transforms or global aliasing.

Engineers MUST NOT leak Node.js built-ins, browser globals, or edge runtime APIs across distinct environment boundaries via shared top-level plugin transforms or global aliasing.

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

Vite plugins MUST implement `applyToEnvironment(env)` or check `env.name` to ensure transformation passes and resolve hooks only execute within their intended runtime context.

Vite plugins MUST implement `applyToEnvironment(env)` or check `env.name` to ensure transformation passes and resolve hooks only execute within their intended runtime 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

Edge and worker environments MUST declare target-specific `resolve.conditions` (e.g., `['worker', 'workerd', 'edge-light']`) and explicitly set `noExternal

Edge and worker environments MUST declare target-specific `resolve.conditions` (e.g., `['worker', 'workerd', 'edge-light']`) and explicitly set `noExternal: true` to prevent Node.js module resolution 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

Server runners and middleware MUST access environment-specific module graphs via `server.environments[name].moduleGraph` rather than relying on the legacy shared `server.moduleGraph`.

Server runners and middleware MUST access environment-specific module graphs via `server.environments[name].moduleGraph` rather than relying on the legacy shared `server.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.
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 Deterministic Runtime Boundary Isolation critical for AI coding assistants?

Enforces deterministic module resolution boundaries and isolated module graphs across distinct Vite 6 execution contexts (browser, Node.js SSR, and edge/workerd runtimes). Prevents runtime leakage, cross-environment cache contamination, and invalid export condition resolution in multi-target 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 (Global Resolution Bleed and Cross-Runtime Module Graph Contamination) 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

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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