[JoaoMarcos44]

Closes #16100.

Cause and consequence

effect() changed the caller's scheduler and onStop options to undefined. Reusing the options could lose scheduling and cleanup callbacks, and frozen options could throw in ESM. Reading the remaining options before installing cleanup also let a debug-hook getter stop the effect's scope or throw before onStop was attached.

Solution

Read scheduler and onStop once and install their behavior first. Then copy the other own enumerable option properties to the effect, including symbol keys, without changing the caller's object. Property reads keep their original receiver.

Why this approach

It preserves the callback setup order while supporting shared, frozen, readonly and getter-based options. If an onTrack or onTrigger getter stops the scope, or throws before the caller stops it, cleanup is already installed. Inherited and non-enumerable debug-hook behavior follows the existing option-copying rules.

Pros and cons

• Pros: shared options retain callbacks; frozen options work; getters are read once; cleanup survives reentrant debug getters; own enumerable symbols are preserved.
• Cons: option creation enumerates own keys and checks enumerability. No performance benchmark was run. The existing repeated-stop callback behavior is outside this fix.

The PR targets minor because the original mutation regression is in the 3.6 line; stable 3.5.44 and main retain the non-mutating implementation.

Validation

• Four durable getter-cleanup tests failed before the initialization-order fix, then passed. Controls cover frozen single-read getters, inherited/non-enumerable hooks and own enumerable symbols with the original receiver.
• effect.spec.ts: 84/84. Reactivity tests including unit-gc and supplementary review cases: 500 passed, 2 existing todo tests.
• Coverage of effect.ts: 90.26% statements, 88.33% branches, 90.47% functions, 90.90% lines.
• Full project TypeScript, targeted Vite+ lint/format and reactivity esm-browser development/production builds passed.
• The original frozen/shared-options reproduction and the additional scope/getter cases were exercised in isolated snapshots.
• RED/GREEN evidence is preserved in the branch commits.

Original reproduction · PR preview

AI-generated conceptual illustration: reactive effects can reuse the caller-owned options while scheduling and cleanup callbacks are installed first. This is not execution or test evidence.

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[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-11-02T19:07:39.512091Z	d6b8219	New commits

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[edison1105]

Closing in favor of #16105