Fix hydrated atom reactivity initial values

[xianjianlf2]

Summary

• route hydrated serializable atom values through the same initial-value target path used by AtomRegistry initialValues
• keep hydrated nodes stale until first read so withReactivity can register its finalizer before mutations
• add a regression test for hydrated serializable atoms with reactivity

Fixes #6360.

Tests

• pnpm lint-fix
• pnpm test packages/effect/test/reactivity/Atom.test.ts
• pnpm check

Summary by CodeRabbit

• Bug Fixes

  • Fixed reactivity for hydrated serializable atoms.
  • Hydrated atoms now respond correctly to subsequent updates and trigger expected rebuilds.
  • Improved initialization behavior when atoms derive their values from other atoms.

• Tests

  • Added coverage for hydration and reactive updates of serializable atoms.

[changeset-bot]

🦋 Changeset detected

Latest commit: 48d6b5e

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 27 packages

Name	Type
effect	Patch
@effect/opentelemetry	Patch
@effect/platform-browser	Patch
@effect/platform-bun	Patch
@effect/platform-node-shared	Patch
@effect/platform-node	Patch
@effect/vitest	Patch
@effect/ai-anthropic	Patch
@effect/ai-openai-compat	Patch
@effect/ai-openai	Patch
@effect/ai-openrouter	Patch
@effect/atom-react	Patch
@effect/atom-solid	Patch
@effect/atom-vue	Patch
@effect/sql-clickhouse	Patch
@effect/sql-d1	Patch
@effect/sql-libsql	Patch
@effect/sql-mssql	Patch
@effect/sql-mysql2	Patch
@effect/sql-pg	Patch
@effect/sql-pglite	Patch
@effect/sql-sqlite-bun	Patch
@effect/sql-sqlite-do	Patch
@effect/sql-sqlite-node	Patch
@effect/sql-sqlite-react-native	Patch
@effect/sql-sqlite-wasm	Patch
@effect/openapi-generator	Patch

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ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

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Run ID: 92d11bc6-a9c1-42ca-ba51-5a6a49f284cd

📥 Commits

Reviewing files that changed from the base of the PR and between 4e0be58 and 48d6b5e.

📒 Files selected for processing (3)

• .changeset/fix-hydrated-atom-reactivity.md
• packages/effect/src/unstable/reactivity/AtomRegistry.ts
• packages/effect/test/reactivity/Atom.test.ts

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📝 Walkthrough

Walkthrough

Hydrated serializable atoms now resolve their initial-value target and use setInitialValue, allowing reactivity callbacks to register during the initial read. A regression test verifies updates after hydration, and the changeset declares a patch release.

Changes

Hydrated atom reactivity

Layer / File(s)	Summary
Route hydrated values through initial-value targets packages/effect/src/unstable/reactivity/AtomRegistry.ts	Centralizes initialValueTarget traversal and applies decoded hydrated values through setInitialValue on the resolved node.
Validate hydrated reactivity behavior packages/effect/test/reactivity/Atom.test.ts, .changeset/fix-hydrated-atom-reactivity.md	Adds hydration and rebuild assertions for serializable atoms and records a patch release.

Estimated code review effort: 2 (Simple) | ~10 minutes

Sequence Diagram(s)

sequenceDiagram
  participant Hydration
  participant AtomRegistry
  participant Atom
  participant Reactivity
  Hydration->>AtomRegistry: hydrate dehydrated atom state
  AtomRegistry->>AtomRegistry: resolve initialValueTarget
  AtomRegistry->>Atom: setInitialValue(decoded value)
  Atom->>Reactivity: register invalidation callback during read
  Reactivity->>AtomRegistry: trigger rebuild after mutation

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Possibly related PRs

• Effect-TS/effect#6563: Both changes modify AtomRegistry.ts reactivity and rebuild behavior.

Suggested reviewers: tim-smart, gcanti

🚥 Pre-merge checks | ✅ 2

✅ Passed checks (2 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	The hydration path now mirrors initialValues by resolving initialValueTarget and using setInitialValue, which matches #6360's requirement.
Out of Scope Changes check	✅ Passed	The changes are scoped to the hydration reactivity fix, its regression test, and release metadata; no unrelated code changes appear.

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