[2.0] Effects re-run (and run cleanup) when the compute returns an equal value; there's no equals option #4184

Describe the bug

createEffect(compute, effectFn) and createRenderEffect re-run the effect function, and the previous cleanup, every time a tracked read changes, even when compute returns the same value as before. EffectOptions (packages/signals/src/signals.ts) has no equals, and passing one is silently ignored.

Your Example Website or App

Minimal repro inline below (signals-only). Real-world occurrence: https://github.com/openclaw/openclaw/blob/1989e3dc436/.agents/skills/solid/references/lessons.md#L8

Steps to Reproduce the Bug or Issue

import { createSignal, createRoot, createEffect, createMemo, flush } from "@solidjs/signals";

let applies = 0, cleanups = 0;
const [n, setN] = createSignal(1);
createRoot(() => createEffect(() => n() > 0, () => { applies++; return () => { cleanups++; }; }));
flush(); setN(2); flush(); setN(3); flush();
// compute returned true three times

createRenderEffect gives the same numbers.

Expected behavior

Either:

• the effect skips its apply and cleanup when the compute result is equal (using the same default equals as memos, or an equals option on effects); or
• the reactivity docs and cheatsheet state the current behavior clearly and recommend a memo in front. An unknown equals option could also warn in dev instead of being silently ignored.

Screenshots or Videos

No response

Platform

• OS: macOS (Darwin 25.5)
• Browser: n/a (reproduced in Node v24.18.0 with vitest, importing source)
• Version: solid next @ b0ad1df (2026-10-20, after 2.0.0-rc.16)

Additional context

• React developers assume the opposite: useEffect skips when its dependencies are unchanged.
• Cleanups churn: because cleanups re-run, subscriptions and timers are torn down and restarted on unrelated changes.
• Seen in production: OpenClaw hit this in production. A props refresh re-ran an effect with an unchanged status, which cancelled a timer and never restarted it (https://github.com/openclaw/openclaw/blob/1989e3dc436/.agents/skills/solid/references/lessons.md#L8).
• Documented as a pitfall: the From React additions (docs(migration): name React hooks and fill gaps in From React solid-docs#1664) describe this.

— Claude, on behalf of @devagrawal09