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frontendcritical PriorityID: vite-rolldown-federation-singleton-boundary

Vite 6 Rolldown Module Federation Singleton & Symbol Isolation Invariant

Enforces deterministic runtime singleton boundaries and strict AST tree-shaking across Vite 6 and Rolldown federated micro-frontends. Prevents dual-package hazards, duplicate React/state-store runtime instantiation, and catastrophic symbol leaks across asynchronous federated boundaries.

Prohibited Anti-Pattern: Dual-Instance Leaks and Tree-Shaking Bailout via Unconstrained Federated Shared Dependencies

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---
description: Vite 6 Rolldown Module Federation Singleton & Symbol Isolation Invariant - Enforces deterministic runtime singleton boundaries and strict AST tree-shaking across Vite 6 and Rolldown federated micro-frontends. Prevents dual-package hazards, duplicate React/state-store runtime instantiation, and catastrophic symbol leaks across asynchronous federated boundaries.
globs: vite.config.ts, vite.config.mts, src/**/*.{ts,tsx}
alwaysApply: true
verified_by: "agentrules.org"
license: "CC-BY-4.0"
source: "https://agentrules.org/rules/vite-rolldown-federation-singleton-boundary"
---

# Vite 6 Rolldown Module Federation Singleton & Symbol Isolation Invariant

> **Severity**: CRITICAL | **Category**: frontend
> **Anti-Pattern Warning**: Dual-Instance Leaks and Tree-Shaking Bailout via Unconstrained Federated Shared Dependencies

## System Constraints
You are a Principal Software Architect enforcing strict Module Federation and AST boundary invariants under Vite 6 and Rolldown. You must mandate exact singleton deduplication, strict version matching, tree-shaking guarantees, and symbol boundary isolation across micro-frontends sharing a unified host runtime.

## Strict Guidelines
- Engineers MUST ALWAYS declare stateful runtime dependencies (`react`, `react-dom`, `@tanstack/react-query`, state stores) with `singleton: true`, `strictVersion: true`, and explicit `requiredVersion` in Vite Module Federation configurations.
- Engineers MUST NOT allow barrel export re-exports of federated remotes that compromise Rolldown's AST tree-shaking and trigger eager loading of isolated remote chunks.
- Code SHOULD import isolated design system tokens or sub-path components directly rather than importing monolithic root entry points across federated boundaries.
- Services MUST ensure that cross-boundary runtime contexts (e.g., QueryClient, ThemeContext) evaluate to a single memory address across host and remote scopes.
- Components NEVER instantiate isolated local fallbacks for shared singletons without checking the global federated runtime scope.

## Bad vs Good Implementations
### Federation Shared Config & Async Boundary Invariant

#### Bad Antipattern (AI Common Hallucination)
> **Why it fails**: Passing plain string arrays in `shared` disables strict version negotiation and singleton verification. Rolldown will bundle duplicate vendor chunks if minor versions diverge, causing 'Invalid Hook Call' and broken Context identities.
```typescript
import { defineConfig } from 'vite';
import { federation } from '@module-federation/vite';

export default defineConfig({
  plugins: [
    federation({
      name: 'remote_app',
      filename: 'remoteEntry.js',
      exposes: {
        './Widget': './src/Widget.tsx'
      },
      // ANTI-PATTERN: Loose shared configuration causes duplicate React runtimes,
      // breaking Context, Hooks state, and TanStack Query cache under Rolldown.
      shared: ['react', 'react-dom']
    })
  ]
});
```

#### Production Standard (Correct)
> **Standard**: Declaring dependencies with `singleton: true`, `strictVersion: true`, and explicit version bounds guarantees that Rolldown and the Module Federation runtime isolate and deduplicate singletons to a single runtime instance.
```typescript
import { defineConfig } from 'vite';
import { federation } from '@module-federation/vite';
import packageJson from './package.json' with { type: 'json' };

export default defineConfig({
  plugins: [
    federation({
      name: 'remote_app',
      filename: 'remoteEntry.js',
      exposes: {
        './Widget': './src/Widget.tsx'
      },
      shared: {
        react: {
          singleton: true,
          strictVersion: true,
          requiredVersion: packageJson.dependencies.react
        },
        'react-dom': {
          singleton: true,
          strictVersion: true,
          requiredVersion: packageJson.dependencies['react-dom']
        },
        '@tanstack/react-query': {
          singleton: true,
          strictVersion: true,
          requiredVersion: packageJson.dependencies['@tanstack/react-query']
        }
      }
    })
  ],
  build: {
    target: 'esnext',
    modulePreload: false
  }
});
```
Recommended MCP Servers (mcp-serverlist.com)

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

Rolldown Chunk Inspector MCP
Analyzes Rolldown bundle graphs and Module Federation shared scopes to detect duplicate symbols.
Recommended Agent Skills (askills.dev)

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

Module Federation Runtime Auditor
CLI utility to inspect and validate shared singleton boundary constraints in production build manifests.
Architectural Specification & Invariant Rationale

Architectural Invariant Design: Vite 6 Rolldown Module Federation Singleton & Symbol Isolation Invariant

Vite 6 Rolldown Module Federation Singleton & Symbol Isolation Invariant defines an industrial-grade behavioral standard for frontend engineering. Enforces deterministic runtime singleton boundaries and strict AST tree-shaking across Vite 6 and Rolldown federated micro-frontends. Prevents dual-package hazards, duplicate React/state-store runtime instantiation, and catastrophic symbol leaks across asynchronous federated boundaries. 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: Dual-Instance Leaks and Tree-Shaking Bailout via Unconstrained Federated Shared Dependencies 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 DriftDual-Instance Leaks and Tree-Shaking Bailout via Unconstrained Federated Shared DependenciesCritical
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 stateful runtime dependencies (`react`, `react-dom`, `@tanstack/react-query`, state stores) with `singleton

Engineers MUST ALWAYS declare stateful runtime dependencies (`react`, `react-dom`, `@tanstack/react-query`, state stores) with `singleton: true`, `strictVersion: true`, and explicit `requiredVersion` in Vite Module Federation 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.
2

Engineers MUST NOT allow barrel export re-exports of federated remotes that compromise Rolldown's AST tree-shaking and trigger eager loading of isolated remote chunks.

Engineers MUST NOT allow barrel export re-exports of federated remotes that compromise Rolldown's AST tree-shaking and trigger eager loading of isolated remote chunks.

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 import isolated design system tokens or sub-path components directly rather than importing monolithic root entry points across federated boundaries.

Code SHOULD import isolated design system tokens or sub-path components directly rather than importing monolithic root entry points across federated boundaries.

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 ensure that cross-boundary runtime contexts (e.g., QueryClient, ThemeContext) evaluate to a single memory address across host and remote scopes.

Services MUST ensure that cross-boundary runtime contexts (e.g., QueryClient, ThemeContext) evaluate to a single memory address across host and remote scopes.

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 instantiate isolated local fallbacks for shared singletons without checking the global federated runtime scope.

Components NEVER instantiate isolated local fallbacks for shared singletons without checking the global federated runtime scope.

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 Rolldown Module Federation Singleton & Symbol Isolation Invariant critical for AI coding assistants?

Enforces deterministic runtime singleton boundaries and strict AST tree-shaking across Vite 6 and Rolldown federated micro-frontends. Prevents dual-package hazards, duplicate React/state-store runtime instantiation, and catastrophic symbol leaks across asynchronous federated boundaries. 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 (Dual-Instance Leaks and Tree-Shaking Bailout via Unconstrained Federated Shared Dependencies) 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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