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frontendcritical PriorityID: vite6-environment-api-boundary-isolation

Vite 6 Environment API Runtime Graph Boundary Isolation

Enforces strict runtime boundary isolation across heterogenous target environments (Client, Node SSR, Edge/Workerd, and RSC) using the Vite 6 Environment API. Prevents module graph pollution, illegal global polyfill sharing, and non-deterministic state leaks during multi-target evaluation.

Prohibited Anti-Pattern: Cross-Environment Global State Leakage via Legacy ssrLoadModule and Shared Lexical Plugin Caches

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---
description: Vite 6 Environment API Runtime Graph Boundary Isolation - Enforces strict runtime boundary isolation across heterogenous target environments (Client, Node SSR, Edge/Workerd, and RSC) using the Vite 6 Environment API. Prevents module graph pollution, illegal global polyfill sharing, and non-deterministic state leaks during multi-target evaluation.
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-boundary-isolation"
---

# Vite 6 Environment API Runtime Graph Boundary Isolation

> **Severity**: CRITICAL | **Category**: frontend
> **Anti-Pattern Warning**: Cross-Environment Global State Leakage via Legacy ssrLoadModule and Shared Lexical Plugin Caches

## System Constraints
You are a Principal Software Architect enforcing Vite 6 Environment API Runtime Boundary Isolation. You must ensure that code executing across different runtime targets (browser, Node.js, Edge/workerd) maintains isolated module execution graphs, independent resolve conditions, and discrete runtime runners without cross-boundary state leakage.

## Strict Guidelines
- Engineers MUST ALWAYS configure distinct runtime execution graphs via Vite 6 'environments' (e.g., 'client', 'ssr', 'edge') instead of relying on legacy top-level 'ssr' boolean flags.
- Engineers MUST NOT invoke deprecated 'server.ssrLoadModule' or 'server.ssrFixStacktrace'; use 'server.environments[name].runner.import' or dedicated ViteRuntime instances instead.
- Code SHOULD enforce target-specific export condition resolution per environment (e.g., ['workerd', 'worker'] for edge vs ['node', 'import'] for ssr) in 'vite.config.ts'.
- Services MUST NOT share transform caches across environments; Vite plugins must scope cached compilation artifacts to 'this.environment.name' or 'this.environment.moduleGraph'.
- Components NEVER import edge-only or server-only globals directly into shared modules without explicit runtime-scoped environment boundary gates.

## Bad vs Good Implementations
### Vite 6 Multi-Environment Target Configuration

#### Bad Antipattern (AI Common Hallucination)
> **Why it fails**: Legacy Vite config uses a single 'ssr' target, blending Node.js and Edge resolution. It lacks execution graph isolation, causing cross-contamination of globals and conflicting export condition resolutions.
```typescript
import { defineConfig } from 'vite';

// ANTI-PATTERN: Monolithic SSR configuration sharing conditions across Node and Edge
export default defineConfig({
  ssr: {
    target: 'node',
    noExternal: true,
  },
  define: {
    // Pollutes all targets, causing browser hydration to receive node definitions
    'process.env.RUNTIME': JSON.stringify(process.env.RUNTIME),
  },
});
```

#### Production Standard (Correct)
> **Standard**: Declares separate environment runners with distinct resolution conditions and output graphs, guaranteeing that Edge bundle evaluation does not inherit Node SSR dependencies or global mutations.
```typescript
import { defineConfig } from 'vite';

// PRODUCTION INVARIANT: Vite 6 Environment API with isolated runtime graphs
export default defineConfig({
  environments: {
    client: {
      build: {
        outDir: 'dist/client',
      },
    },
    ssr: {
      consumer: 'server',
      resolve: {
        conditions: ['node', 'import'],
        externalConditions: ['node', 'import'],
      },
      build: {
        outDir: 'dist/server',
      },
    },
    edge: {
      consumer: 'server',
      resolve: {
        conditions: ['edge-light', 'workerd', 'worker'],
        noExternal: true,
      },
      build: {
        outDir: 'dist/edge',
      },
    },
  },
});
```

### Plugin Transform Isolation via this.environment

#### Bad Antipattern (AI Common Hallucination)
> **Why it fails**: Using a shared module-level Map keyed only by module ID contaminates SSR output with client transforms and vice versa during concurrent multi-environment evaluation in Vite 6.
```typescript
import type { Plugin } from 'vite';

// ANTI-PATTERN: Global plugin cache leaks transforms across client and ssr
const transformCache = new Map<string, string>();

export function brokenPlugin(): Plugin {
  return {
    name: 'broken-shared-cache',
    transform(code, id, options) {
      // options.ssr is deprecated and imprecise
      if (transformCache.has(id)) {
        return transformCache.get(id);
      }
      const result = code.replace(/__TARGET__/g, options?.ssr ? 'node' : 'client');
      transformCache.set(id, result);
      return result;
    },
  };
}
```

#### Production Standard (Correct)
> **Standard**: Accesses the current environment context via 'this.environment', ensuring transformations and cache buckets are hermetically sealed per runtime execution graph.
```typescript
import type { Plugin } from 'vite';

// PRODUCTION INVARIANT: Isolated environment cache using this.environment.name
export function robustPlugin(): Plugin {
  const environmentCaches = new Map<string, Map<string, string>>();

  return {
    name: 'robust-isolated-cache',
    transform(code, id) {
      const envName = this.environment.name;
      let cache = environmentCaches.get(envName);
      if (!cache) {
        cache = new Map<string, string>();
        environmentCaches.set(envName, cache);
      }

      if (cache.has(id)) {
        return cache.get(id);
      }

      const target = this.environment.config.consumer === 'server' ? envName : 'client';
      const result = code.replace(/__TARGET__/g, target);
      cache.set(id, result);
      return result;
    },
  };
}
```
Recommended MCP Servers (mcp-serverlist.com)

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

Filesystem Guard
Verifies file boundaries and output directories for multi-environment compilation targets.
Recommended Agent Skills (askills.dev)

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

Vite Environment Verifier
CLI diagnostics to validate distinct Environment API graphs and detect deprecated ssrLoadModule call-sites.
Architectural Specification & Invariant Rationale

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

Vite 6 Environment API Runtime Graph Boundary Isolation defines an industrial-grade behavioral standard for frontend engineering. Enforces strict runtime boundary isolation across heterogenous target environments (Client, Node SSR, Edge/Workerd, and RSC) using the Vite 6 Environment API. Prevents module graph pollution, illegal global polyfill sharing, and non-deterministic state leaks during multi-target evaluation. 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: Cross-Environment Global State Leakage via Legacy ssrLoadModule and Shared Lexical Plugin Caches 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 DriftCross-Environment Global State Leakage via Legacy ssrLoadModule and Shared Lexical Plugin CachesCritical
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 runtime execution graphs via Vite 6 'environments' (e.g., 'client', 'ssr', 'edge') instead of relying on legacy top-level 'ssr' boolean flags.

Engineers MUST ALWAYS configure distinct runtime execution graphs via Vite 6 'environments' (e.g., 'client', 'ssr', 'edge') instead of relying on legacy top-level 'ssr' boolean 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 NOT invoke deprecated 'server.ssrLoadModule' or 'server.ssrFixStacktrace'

Engineers MUST NOT invoke deprecated 'server.ssrLoadModule' or 'server.ssrFixStacktrace'; use 'server.environments[name].runner.import' or dedicated ViteRuntime instances instead.

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 enforce target-specific export condition resolution per environment (e.g., ['workerd', 'worker'] for edge vs ['node', 'import'] for ssr) in 'vite.config.ts'.

Code SHOULD enforce target-specific export condition resolution per environment (e.g., ['workerd', 'worker'] for edge vs ['node', 'import'] for ssr) in 'vite.config.ts'.

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 NOT share transform caches across environments

Services MUST NOT share transform caches across environments; Vite plugins must scope cached compilation artifacts to 'this.environment.name' or 'this.environment.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.
5

Components NEVER import edge-only or server-only globals directly into shared modules without explicit runtime-scoped environment boundary gates.

Components NEVER import edge-only or server-only globals directly into shared modules without explicit runtime-scoped environment boundary gates.

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 Graph Boundary Isolation critical for AI coding assistants?

Enforces strict runtime boundary isolation across heterogenous target environments (Client, Node SSR, Edge/Workerd, and RSC) using the Vite 6 Environment API. Prevents module graph pollution, illegal global polyfill sharing, and non-deterministic state leaks during multi-target evaluation. 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 (Cross-Environment Global State Leakage via Legacy ssrLoadModule and Shared Lexical Plugin Caches) 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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