Avoid timers in synchronous scheduler dispatch

[tim-smart]

Summary

• dispatch yielded sync-mode scheduler work with cancellable microtasks when no custom dispatcher is supplied
• run Standard Schema validation with a sync-mode scheduler
• cover Convex-like environments where timer APIs throw and add a patch changeset

Testing

• pnpm lint-fix
• pnpm check
• pnpm --filter effect test --run (232 files passed; 7,162 tests passed; 3 skipped)

Closes EFF-115
Closes EFF-113
Closes #6651

Summary by CodeRabbit

• Bug Fixes
  • Synchronous effect execution now dispatches yielded work through cancellable microtasks.
  • Synchronous schema validation uses the updated scheduling behavior.
  • Avoids unnecessary timer-based scheduling during synchronous runs.

[changeset-bot]

🦋 Changeset detected

Latest commit: afae057

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

This PR includes changesets to release 28 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/docgen	Patch
@effect/openapi-generator	Patch

Not sure what this means? Click here to learn what changesets are.

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[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro Plus

Run ID: a1e1c4b8-3e0c-4527-a56f-51224361adf0

📥 Commits

Reviewing files that changed from the base of the PR and between 3fccb56 and afae057.

📒 Files selected for processing (4)

• .changeset/eff-115-sync-scheduler-microtask.md
• packages/effect/src/Scheduler.ts
• packages/effect/src/Schema.ts
• packages/effect/test/Scheduler.test.ts

---

📝 Walkthrough

Walkthrough

Synchronous scheduler dispatch now uses cancellable microtasks instead of timer-based scheduling. Standard Schema validation opts into sync mode, and tests verify yielded synchronous effects complete without calling timer APIs.

Changes

Sync scheduler dispatch

Layer / File(s)	Summary
Cancellable synchronous dispatch packages/effect/src/Scheduler.ts	Adds cancellable queueMicrotask scheduling and makes MixedScheduler select it by default for "sync" execution while retaining the existing async scheduler fallback.
Schema integration and regression coverage packages/effect/src/Schema.ts, packages/effect/test/Scheduler.test.ts, .changeset/eff-115-sync-scheduler-microtask.md	Standard Schema validation constructs a sync scheduler; tests verify yielded synchronous effects avoid setImmediate and setTimeout, and a patch changeset documents the update.

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

Suggested labels: bug, 4.0

Suggested reviewers: gcanti

🚥 Pre-merge checks | ✅ 2

✅ Passed checks (2 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	The PR implements sync-mode microtask dispatch and switches Standard Schema validation to it, matching the issue’s requirement to avoid timer APIs in synchronous paths.
Out of Scope Changes check	✅ Passed	All changes are directly tied to the sync scheduler fix, validation path update, test coverage, and release note.

---

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[github-actions]

Bundle Size Analysis

File Name	Current Size	Previous Size	Difference
basic.ts	6.63 KB	6.60 KB	+0.03 KB (+0.50%)
batching.ts	9.37 KB	9.34 KB	+0.04 KB (+0.37%)
brand.ts	6.25 KB	6.25 KB	0.00 KB (0.00%)
cache.ts	10.11 KB	10.07 KB	+0.04 KB (+0.39%)
config.ts	19.21 KB	19.17 KB	+0.04 KB (+0.23%)
differ.ts	18.42 KB	18.39 KB	+0.03 KB (+0.14%)
http-client.ts	20.76 KB	20.73 KB	+0.03 KB (+0.15%)
logger.ts	10.28 KB	10.25 KB	+0.04 KB (+0.35%)
metric.ts	8.55 KB	8.51 KB	+0.04 KB (+0.47%)
optic.ts	7.41 KB	7.41 KB	0.00 KB (0.00%)
pubsub.ts	14.19 KB	14.16 KB	+0.04 KB (+0.25%)
queue.ts	11.08 KB	11.05 KB	+0.03 KB (+0.31%)
schedule.ts	10.27 KB	10.24 KB	+0.04 KB (+0.37%)
schema-class.ts	18.16 KB	18.12 KB	+0.04 KB (+0.22%)
schema-fromJsonSchemaDocument.ts	28.02 KB	27.97 KB	+0.05 KB (+0.17%)
schema-representation-roundtrip.ts	24.33 KB	24.30 KB	+0.03 KB (+0.13%)
schema-string-transformation.ts	12.69 KB	12.65 KB	+0.04 KB (+0.29%)
schema-string.ts	10.35 KB	10.31 KB	+0.04 KB (+0.37%)
schema-template-literal.ts	14.48 KB	14.45 KB	+0.04 KB (+0.24%)
schema-toArbitraryLazy.ts	20.93 KB	20.90 KB	+0.03 KB (+0.16%)
schema-toCodeDocument.ts	23.38 KB	23.33 KB	+0.05 KB (+0.20%)
schema-toCodecJson.ts	18.32 KB	18.29 KB	+0.03 KB (+0.15%)
schema-toEquivalence.ts	18.00 KB	17.96 KB	+0.04 KB (+0.21%)
schema-toFormatter.ts	17.88 KB	17.84 KB	+0.04 KB (+0.21%)
schema-toJsonSchemaDocument.ts	21.51 KB	21.48 KB	+0.03 KB (+0.15%)
schema-toRepresentation.ts	18.55 KB	18.52 KB	+0.03 KB (+0.15%)
schema.ts	17.43 KB	17.39 KB	+0.03 KB (+0.20%)
stm.ts	12.05 KB	12.02 KB	+0.03 KB (+0.28%)
stream.ts	9.36 KB	9.32 KB	+0.04 KB (+0.45%)