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frontendcritical PriorityID: solidstart-server-rpc-async-boundary-invariants

SolidStart 1.0 server$ RPC Serialization & Async Boundary Invariants

Enforces rigid separation between SolidJS client reactive tracking scopes and SolidStart 1.0 server$ RPC functions. Mandates wrapping server RPC calls within createAsync or action primitives, preventing lexical closure over client signals inside server-bound functions and requiring explicit Suspense boundaries for all asynchronous resource states.

Prohibited Anti-Pattern: Closing Over Reactive Signals in server$ Lexical Scopes or Executing Naked RPCs in Tracking Contexts

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---
description: SolidStart 1.0 server$ RPC Serialization & Async Boundary Invariants - Enforces rigid separation between SolidJS client reactive tracking scopes and SolidStart 1.0 server$ RPC functions. Mandates wrapping server RPC calls within createAsync or action primitives, preventing lexical closure over client signals inside server-bound functions and requiring explicit Suspense boundaries for all asynchronous resource states.
globs: src/**/*.{ts,tsx}
alwaysApply: true
verified_by: "agentrules.org"
license: "CC-BY-4.0"
source: "https://agentrules.org/rules/solidstart-server-rpc-async-boundary-invariants"
---

# SolidStart 1.0 server$ RPC Serialization & Async Boundary Invariants

> **Severity**: CRITICAL | **Category**: frontend
> **Anti-Pattern Warning**: Closing Over Reactive Signals in server$ Lexical Scopes or Executing Naked RPCs in Tracking Contexts

## System Constraints
You are a Principal Software Architect enforcing SolidStart 1.0 architectural integrity. Mandate strict boundary isolation between Vinxi/Nitro server$ RPC endpoints and SolidJS reactive graphs. Prohibit client signal closures inside server$ bodies, require createAsync/cache/action wrappers for RPC execution, and enforce Suspense/ErrorBoundary wrapping around all async primitives.

## Strict Guidelines
- Engineers MUST ALWAYS isolate server$ closures from client reactive scopes; server$ functions MUST accept all dynamic data strictly via serializable, explicit input parameters.
- Engineers MUST NOT reference, read, or close over client signals, stores, or browser APIs (window, document) from inside a server$ definition body.
- Code MUST wrap read-oriented server$ RPC calls inside createAsync() from @solidjs/router or createResource() from solid-js, paired with query/cache wrappers for deduplication.
- Code MUST wrap write-oriented server$ RPC calls inside action() from @solidjs/router or useSubmission() primitives to handle transitions and validation safely.
- Components NEVER execute raw server$ RPC calls directly inside tracking scopes (createEffect, createMemo, render root) without an async primitive wrapper, as this causes infinite tracking loops or hydration mismatch errors.
- Services MUST ensure every route reading from createAsync is wrapped in both a <Suspense> boundary and an <ErrorBoundary> to prevent uncaught SSR stream rejections.

## Bad vs Good Implementations
### server$ Signal Closure & Naked Invocation vs. Cached createAsync Parameterization

#### Bad Antipattern (AI Common Hallucination)
> **Why it fails**: Closing over `userId()` inside `server$` breaks AST extraction; Vinxi isolates `server$` into an RPC endpoint where client scope does not exist. Calling the RPC inside `createEffect` to set manual signal state breaks SSR streaming, hydration, and fine-grained reactivity.
```typescript
import { createSignal, createEffect } from "solid-js";
import { server$ } from "@solidjs/start/server";

export default function UserProfile() {
  const [userId, setUserId] = createSignal("usr_123");
  const [user, setUser] = createSignal<any>(null);

  // BAD: server$ closes over client signal `userId` lexically
  // BAD: Executing raw server RPC directly inside createEffect without createAsync
  const fetchUserBad = server$(async () => {
    // RUNTIME CRASH: `userId` is undefined or leaks client state across RPC wire
    const id = userId(); 
    return await db.user.findUnique({ where: { id } });
  });

  createEffect(async () => {
    const data = await fetchUserBad();
    setUser(data);
  });

  return <div>{user()?.name}</div>;
}
```

#### Production Standard (Correct)
> **Standard**: The RPC function uses explicit parameterization and the `query` cache helper. `createAsync` correctly coordinates with the `userId` accessor and integrates into Solid's SSR Suspense pipeline without hydration drops or broken closures.
```typescript
import { createSignal, Suspense } from "solid-js";
import { query, createAsync } from "@solidjs/router";

// GOOD: Define cached server RPC with explicit serializable arguments
const getUser = query(async (id: string) => {
  "use server";
  if (!id) throw new Error("User ID is required");
  return await db.user.findUnique({ where: { id } });
}, "getUser");

export default function UserProfile() {
  const [userId, setUserId] = createSignal("usr_123");

  // GOOD: Pass accessor function to createAsync; tracks signal changes correctly
  const user = createAsync(() => getUser(userId()));

  return (
    <Suspense fallback={<div>Loading profile...</div>}>
      <div>{user()?.name}</div>
    </Suspense>
  );
}
```
Recommended MCP Servers (mcp-serverlist.com)

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

Fetch MCP Server
Inspect SolidStart 1.0 RPC network requests and verify serializable payloads across the client-server boundary.
Recommended Agent Skills (askills.dev)

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

SolidStart CLI Auditor
Validates Vinxi bundler build outputs and ensures no client symbols leak into server RPC chunks.
Architectural Specification & Invariant Rationale

Architectural Invariant Design: SolidStart 1.0 server$ RPC Serialization & Async Boundary Invariants

SolidStart 1.0 server$ RPC Serialization & Async Boundary Invariants defines an industrial-grade behavioral standard for frontend engineering. Enforces rigid separation between SolidJS client reactive tracking scopes and SolidStart 1.0 server$ RPC functions. Mandates wrapping server RPC calls within createAsync or action primitives, preventing lexical closure over client signals inside server-bound functions and requiring explicit Suspense boundaries for all asynchronous resource states. 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: Closing Over Reactive Signals in server$ Lexical Scopes or Executing Naked RPCs in Tracking Contexts 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 DriftClosing Over Reactive Signals in server$ Lexical Scopes or Executing Naked RPCs in Tracking ContextsCritical
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 isolate server$ closures from client reactive scopes

Engineers MUST ALWAYS isolate server$ closures from client reactive scopes; server$ functions MUST accept all dynamic data strictly via serializable, explicit input parameters.

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 reference, read, or close over client signals, stores, or browser APIs (window, document) from inside a server$ definition body.

Engineers MUST NOT reference, read, or close over client signals, stores, or browser APIs (window, document) from inside a server$ definition body.

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 MUST wrap read-oriented server$ RPC calls inside createAsync() from @solidjs/router or createResource() from solid-js, paired with query/cache wrappers for deduplication.

Code MUST wrap read-oriented server$ RPC calls inside createAsync() from @solidjs/router or createResource() from solid-js, paired with query/cache wrappers for deduplication.

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

Code MUST wrap write-oriented server$ RPC calls inside action() from @solidjs/router or useSubmission() primitives to handle transitions and validation safely.

Code MUST wrap write-oriented server$ RPC calls inside action() from @solidjs/router or useSubmission() primitives to handle transitions and validation safely.

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 execute raw server$ RPC calls directly inside tracking scopes (createEffect, createMemo, render root) without an async primitive wrapper, as this causes infinite tracking loops or hydration mismatch errors.

Components NEVER execute raw server$ RPC calls directly inside tracking scopes (createEffect, createMemo, render root) without an async primitive wrapper, as this causes infinite tracking loops or hydration mismatch errors.

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.
6

Services MUST ensure every route reading from createAsync is wrapped in both a <Suspense> boundary and an <ErrorBoundary> to prevent uncaught SSR stream rejections.

Services MUST ensure every route reading from createAsync is wrapped in both a <Suspense> boundary and an <ErrorBoundary> to prevent uncaught SSR stream rejections.

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 SolidStart 1.0 server$ RPC Serialization & Async Boundary Invariants critical for AI coding assistants?

Enforces rigid separation between SolidJS client reactive tracking scopes and SolidStart 1.0 server$ RPC functions. Mandates wrapping server RPC calls within createAsync or action primitives, preventing lexical closure over client signals inside server-bound functions and requiring explicit Suspense boundaries for all asynchronous resource states. 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 (Closing Over Reactive Signals in server$ Lexical Scopes or Executing Naked RPCs in Tracking Contexts) 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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