Fix duplicate chunk handling in ChunkedMessage.join

[tim-smart]

Summary

• ignore duplicate chunk indexes before updating join bookkeeping
• add a regression test for duplicate delivery followed by successful assembly
• add a patch changeset for effect

Testing

• pnpm lint-fix
• pnpm test packages/effect/test/unstable/eventlog/EventLogMessage.test.ts --run
• pnpm check

Closes EFF-42
Closes #6612

Summary by CodeRabbit

• Bug Fixes

  • Prevented duplicate event log chunks from being counted or overwriting existing data.
  • Improved reliability when assembling event log messages from multiple chunks.

• Tests

  • Added coverage for duplicate chunks and successful message assembly.

[changeset-bot]

🦋 Changeset detected

Latest commit: f52d245

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.

Click here if you're a maintainer who wants to add another changeset to this PR

[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: 8d975c7b-cb04-4b07-9c1f-70721099ead5

📥 Commits

Reviewing files that changed from the base of the PR and between 0e50ec7 and f52d245.

📒 Files selected for processing (3)

• .changeset/fix-eventlog-duplicate-chunks.md
• packages/effect/src/unstable/eventlog/EventLogMessage.ts
• packages/effect/test/unstable/eventlog/EventLogMessage.test.ts

---

📝 Walkthrough

Walkthrough

ChunkedMessage.join now ignores duplicate chunk indexes without updating assembly counts or byte totals. Tests cover duplicate handling and successful combination of distinct parts, and a patch changeset documents the fix.

Changes

Event log chunk assembly

Layer / File(s)	Summary
Duplicate chunk handling packages/effect/src/unstable/eventlog/EventLogMessage.ts, packages/effect/test/unstable/eventlog/EventLogMessage.test.ts, .changeset/fix-eventlog-duplicate-chunks.md	ChunkedMessage.join returns early for already-populated indexes, tests duplicate and distinct chunk joins, and adds a patch release note.

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

Suggested labels: bug

🚥 Pre-merge checks | ✅ 2

✅ Passed checks (2 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	The fix matches #6612 by ignoring duplicate chunk indexes before count/byte updates, preventing premature assembly and the reported crash.
Out of Scope Changes check	✅ Passed	The changes are scoped to the duplicate-chunk fix, its regression test, and the release changeset.

---

_{Comment @coderabbitai help to get the list of available commands.}

[github-actions]

Bundle Size Analysis

File Name	Current Size	Previous Size	Difference
basic.ts	6.64 KB	6.64 KB	0.00 KB (0.00%)
batching.ts	9.42 KB	9.42 KB	0.00 KB (0.00%)
brand.ts	6.20 KB	6.20 KB	0.00 KB (0.00%)
cache.ts	10.13 KB	10.13 KB	0.00 KB (0.00%)
config.ts	19.08 KB	19.08 KB	0.00 KB (0.00%)
differ.ts	18.41 KB	18.41 KB	0.00 KB (0.00%)
http-client.ts	20.73 KB	20.73 KB	0.00 KB (0.00%)
logger.ts	10.30 KB	10.30 KB	0.00 KB (0.00%)
metric.ts	8.56 KB	8.56 KB	0.00 KB (0.00%)
optic.ts	7.41 KB	7.41 KB	0.00 KB (0.00%)
pubsub.ts	14.17 KB	14.17 KB	0.00 KB (0.00%)
queue.ts	11.10 KB	11.10 KB	0.00 KB (0.00%)
schedule.ts	10.28 KB	10.28 KB	0.00 KB (0.00%)
schema-class.ts	18.16 KB	18.16 KB	0.00 KB (0.00%)
schema-fromJsonSchemaDocument.ts	27.31 KB	27.31 KB	0.00 KB (0.00%)
schema-representation-roundtrip.ts	24.16 KB	24.16 KB	0.00 KB (0.00%)
schema-string-transformation.ts	12.68 KB	12.68 KB	0.00 KB (0.00%)
schema-string.ts	10.36 KB	10.36 KB	0.00 KB (0.00%)
schema-template-literal.ts	14.38 KB	14.38 KB	0.00 KB (0.00%)
schema-toArbitraryLazy.ts	20.94 KB	20.94 KB	0.00 KB (0.00%)
schema-toCodeDocument.ts	23.42 KB	23.42 KB	0.00 KB (0.00%)
schema-toCodecJson.ts	18.30 KB	18.30 KB	0.00 KB (0.00%)
schema-toEquivalence.ts	18.01 KB	18.01 KB	0.00 KB (0.00%)
schema-toFormatter.ts	17.86 KB	17.86 KB	0.00 KB (0.00%)
schema-toJsonSchemaDocument.ts	21.49 KB	21.49 KB	0.00 KB (0.00%)
schema-toRepresentation.ts	18.55 KB	18.55 KB	0.00 KB (0.00%)
schema.ts	17.43 KB	17.43 KB	0.00 KB (0.00%)
stm.ts	12.07 KB	12.07 KB	0.00 KB (0.00%)
stream.ts	9.36 KB	9.36 KB	0.00 KB (0.00%)