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frontendcritical PriorityID: solidstart-server-rpc-reactive-boundaries

SolidStart 1.0 Server RPC Serialization and Reactive Tracking Boundaries

Mandate strict separation between client-side fine-grained reactivity and SolidStart 1.0 server$ and query RPC execution contexts. Signals and reactive accessors cannot cross RPC boundaries via closure capture or direct parameter binding; parameters must be passed as serializable values inside createAsync accessors to maintain reactive invalidation without breaking serialization or losing tracking.

Prohibited Anti-Pattern: Capturing Client Signals in Server Function Closures or Passing Signal Accessors Directly to RPCs

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---
description: SolidStart 1.0 Server RPC Serialization and Reactive Tracking Boundaries - Mandate strict separation between client-side fine-grained reactivity and SolidStart 1.0 server$ and query RPC execution contexts. Signals and reactive accessors cannot cross RPC boundaries via closure capture or direct parameter binding; parameters must be passed as serializable values inside createAsync accessors to maintain reactive invalidation without breaking serialization or losing tracking.
globs: src/**/*.{ts,tsx}
alwaysApply: true
verified_by: "agentrules.org"
license: "CC-BY-4.0"
source: "https://agentrules.org/rules/solidstart-server-rpc-reactive-boundaries"
---

# SolidStart 1.0 Server RPC Serialization and Reactive Tracking Boundaries

> **Severity**: CRITICAL | **Category**: frontend
> **Anti-Pattern Warning**: Capturing Client Signals in Server Function Closures or Passing Signal Accessors Directly to RPCs

## System Constraints
You are a Principal Engineer enforcing SolidStart 1.0 Server Functions & Async Boundaries. Mandate invariants regarding reactive tracking, RPC parameter serialization, and async data-fetching patterns across client/server boundaries.

## Strict Guidelines
- Engineers MUST ALWAYS isolate server functions using top-level `query` or `action` definitions with explicit, Seroval-serializable primitive parameters.
- Engineers MUST NOT close over client-side reactive state (signals, memos, stores) inside `server$` closures or functions marked with 'use server'.
- Code SHOULD always invoke parameterized query RPCs inside a `createAsync` accessor (`createAsync(() => getResource(id()))`) so fine-grained dependencies are tracked on the client.
- Services MUST validate and sanitize all incoming arguments inside server functions at the boundary, treating RPC inputs as untrusted network payloads.
- Components NEVER pass uninvoked signal accessors or non-serializable objects (functions, class instances, DOM references) as arguments to server functions.
- Engineers MUST wrap all async component reads relying on `createAsync` within `<Suspense>` and `<ErrorBoundary>` to avoid unhandled promise rejections during SSR streaming.

## Bad vs Good Implementations
### Capturing Signal in Server Function vs. Parameterized Query

#### Bad Antipattern (AI Common Hallucination)
> **Why it fails**: Accessing a client-side signal inside `server$` captures a local reference across an RPC boundary that compiles to a separate network endpoint. At runtime, the client signal does not exist on the server, leading to serialization failure, stale closure bugs, and broken reactivity tracking.
```typescript
import { createSignal } from "solid-js";
import { createAsync } from "@solidjs/router";
import { server$ } from "@solidjs/start/server";
import { db } from "~/server/db";

export default function BadProfile() {
  const [userId, setUserId] = createSignal(123);

  // ANTI-PATTERN: Capturing client-side signal inside server$ closure
  // This breaks serialization, captures stale values, or causes runtime compilation errors
  const fetchUser = server$(async () => {
    return await db.user.findUnique({ where: { id: userId() } });
  });

  const user = createAsync(() => fetchUser());

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

#### Production Standard (Correct)
> **Standard**: The server function `getUser` is defined at the module level as a pure RPC that receives validated serializable primitives. The client component tracks `userId()` within the `createAsync` accessor, cleanly separating client reactivity from the network RPC boundary.
```typescript
import { createSignal, Suspense } from "solid-js";
import { query, createAsync } from "@solidjs/router";
import { db } from "~/server/db";

// PRODUCTION FIX: Pure server function accepting explicit serializable inputs
const getUser = query(async (id: number) => {
  "use server";
  if (!id || typeof id !== "number") {
    throw new Error("Invalid or missing user ID");
  }
  return await db.user.findUnique({ where: { id } });
}, "users.getById");

export default function GoodProfile() {
  const [userId, setUserId] = createSignal(123);

  // Tracks userId() on client; re-triggers RPC when the signal value changes
  const user = createAsync(() => getUser(userId()));

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

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

Seroval Serialization Inspector
Validates payload serializability across SolidStart Vinxi/Nitro client-server boundaries.
Recommended Agent Skills (askills.dev)

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

SolidStart RPC Linter
Static analysis CLI tool that detects signal closures and non-serializable arguments in server$ and query calls.
Architectural Specification & Invariant Rationale

Architectural Invariant Design: SolidStart 1.0 Server RPC Serialization and Reactive Tracking Boundaries

SolidStart 1.0 Server RPC Serialization and Reactive Tracking Boundaries defines an industrial-grade behavioral standard for frontend engineering. Mandate strict separation between client-side fine-grained reactivity and SolidStart 1.0 server$ and query RPC execution contexts. Signals and reactive accessors cannot cross RPC boundaries via closure capture or direct parameter binding; parameters must be passed as serializable values inside createAsync accessors to maintain reactive invalidation without breaking serialization or losing tracking. 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: Capturing Client Signals in Server Function Closures or Passing Signal Accessors Directly to RPCs 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 DriftCapturing Client Signals in Server Function Closures or Passing Signal Accessors Directly to RPCsCritical
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 functions using top-level `query` or `action` definitions with explicit, Seroval-serializable primitive parameters.

Engineers MUST ALWAYS isolate server functions using top-level `query` or `action` definitions with explicit, Seroval-serializable primitive 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 close over client-side reactive state (signals, memos, stores) inside `server$` closures or functions marked with 'use server'.

Engineers MUST NOT close over client-side reactive state (signals, memos, stores) inside `server$` closures or functions marked with 'use server'.

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 always invoke parameterized query RPCs inside a `createAsync` accessor (`createAsync(() => getResource(id()))`) so fine-grained dependencies are tracked on the client.

Code SHOULD always invoke parameterized query RPCs inside a `createAsync` accessor (`createAsync(() => getResource(id()))`) so fine-grained dependencies are tracked on the client.

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 validate and sanitize all incoming arguments inside server functions at the boundary, treating RPC inputs as untrusted network payloads.

Services MUST validate and sanitize all incoming arguments inside server functions at the boundary, treating RPC inputs as untrusted network payloads.

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 pass uninvoked signal accessors or non-serializable objects (functions, class instances, DOM references) as arguments to server functions.

Components NEVER pass uninvoked signal accessors or non-serializable objects (functions, class instances, DOM references) as arguments to server functions.

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

Engineers MUST wrap all async component reads relying on `createAsync` within `<Suspense>` and `<ErrorBoundary>` to avoid unhandled promise rejections during SSR streaming.

Engineers MUST wrap all async component reads relying on `createAsync` within `<Suspense>` and `<ErrorBoundary>` to avoid unhandled promise rejections during SSR streaming.

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 and Reactive Tracking Boundaries critical for AI coding assistants?

Mandate strict separation between client-side fine-grained reactivity and SolidStart 1.0 server$ and query RPC execution contexts. Signals and reactive accessors cannot cross RPC boundaries via closure capture or direct parameter binding; parameters must be passed as serializable values inside createAsync accessors to maintain reactive invalidation without breaking serialization or losing tracking. 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 (Capturing Client Signals in Server Function Closures or Passing Signal Accessors Directly to RPCs) 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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