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frontendhigh PriorityID: micro-frontend-module-federation

Module Federation 2.0 & Micro-Frontend Discipline

Guardrails for Micro-Frontends: Module Federation 2.0 shared dependency singletons, isolated CSS scoping, and resilient runtime error boundaries.

Prohibited Anti-Pattern: AI duplicates React runtime instances causing dual-hook crashes, or leaks global CSS across micro-apps.

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---
description: Module Federation 2.0 & Micro-Frontend Discipline - Guardrails for Micro-Frontends: Module Federation 2.0 shared dependency singletons, isolated CSS scoping, and resilient runtime error boundaries.
globs: **/federation.config.js, **/vite.config.ts
alwaysApply: false
verified_by: "agentrules.org"
license: "CC-BY-4.0"
source: "https://agentrules.org/rules/micro-frontend-module-federation"
---

# Module Federation 2.0 & Micro-Frontend Discipline

> **Severity**: HIGH | **Category**: frontend
> **Anti-Pattern Warning**: AI duplicates React runtime instances causing dual-hook crashes, or leaks global CSS across micro-apps.

## System Constraints
You are a Micro-Frontend architect using Module Federation 2.0. Enforce singleton rules for core libraries (react, react-dom). Ensure federated remotes fail gracefully behind Error Boundaries.

## Strict Guidelines
- Declare core dependencies (react, react-dom) as shared singletons with strictVersion checks.
- Wrap remote federated components in React Error Boundaries and Suspense fallbacks.
- Scope component styles via CSS Modules, Tailwind prefixes, or shadow DOM to prevent global style bleed.

## Bad vs Good Implementations
### Shared Singletons in Module Federation

#### Bad Antipattern (AI Common Hallucination)
> **Why it fails**: Without singleton: true, the host and remote load duplicate React runtimes, causing fatal hook dispatch errors.
```javascript
// Anti-pattern: Missing singleton declaration
new ModuleFederationPlugin({
  name: "remote_app",
  shared: ["react", "react-dom"] // Can load two copies of React runtime simultaneously!
})
```

#### Production Standard (Correct)
> **Standard**: Guarantees a single shared React instance across host and remote micro-frontend boundaries.
```javascript
// Production Standard: Enforced Singletons
new ModuleFederationPlugin({
  name: "remote_app",
  shared: {
    react: { singleton: true, requiredVersion: "^19.0.0" },
    "react-dom": { singleton: true, requiredVersion: "^19.0.0" },
  },
})
```
Recommended MCP Servers (mcp-serverlist.com)

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

Filesystem MCP
Inspect host and remote build configs.
Recommended Agent Skills (askills.dev)

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

Module Federation Doctor
Audit shared dependency versions and singleton consistency.
Architectural Specification & Invariant Rationale

Architectural Invariant Design: Module Federation 2.0 & Micro-Frontend Discipline

Module Federation 2.0 & Micro-Frontend Discipline defines an industrial-grade behavioral standard for frontend engineering. Guardrails for Micro-Frontends: Module Federation 2.0 shared dependency singletons, isolated CSS scoping, and resilient runtime error 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: AI duplicates React runtime instances causing dual-hook crashes, or leaks global CSS across micro-apps. 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 DriftAI duplicates React runtime instances causing dual-hook crashes, or leaks global CSS across micro-apps.High
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

Declare core dependencies (react, react-dom) as shared singletons with strictVersion checks.

Declare core dependencies (react, react-dom) as shared singletons with strictVersion checks.

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

Wrap remote federated components in React Error Boundaries and Suspense fallbacks.

Wrap remote federated components in React Error Boundaries and Suspense fallbacks.

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

Scope component styles via CSS Modules, Tailwind prefixes, or shadow DOM to prevent global style bleed.

Scope component styles via CSS Modules, Tailwind prefixes, or shadow DOM to prevent global style bleed.

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 Module Federation 2.0 & Micro-Frontend Discipline critical for AI coding assistants?

Guardrails for Micro-Frontends: Module Federation 2.0 shared dependency singletons, isolated CSS scoping, and resilient runtime error 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 (AI duplicates React runtime instances causing dual-hook crashes, or leaks global CSS across micro-apps.) 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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