Fix conflict scanning indexes the wrong history array by fubhy · Pull Request #7029 · Effect-TS/effect

fubhy · 2026-08-05T15:01:37Z

Summary

The unencrypted server identifies the correct newer suffix of stored entries but scans an equally sized prefix when building conflicts. It can report entries older than the incoming event while omitting newer same-key entries from the end of storage.

Important

This PR starts with focused failing reproduction tests. Add the implementation fix to this same branch; CI is expected to fail until that fix is included.

Conflict scanning indexes the wrong history array

Module: effect/unstable/eventlog/EventLogServerUnencrypted
Audit ID: effect-64c8be87a9a44e92
Severity / confidence: high / high

What happens

The unencrypted server identifies the correct newer suffix of stored entries but scans an equally sized prefix when building conflicts. It can report entries older than the incoming event while omitting newer same-key entries from the end of storage.

Why it happens

At insertion index i, toConflicts assigns newHistory = history.slice(i). The loop is bounded by newHistory.length but reads history[j] instead of newHistory[j], so whenever i > 0 it examines prefix indices 0..newHistory.length - 1 rather than suffix indices i..history.length - 1.

Expected behavior

For each incoming entry, conflicts must contain all and only non-duplicate stored entries at or after its chronological insertion point whose event tag and primary key match the incoming entry.

Relevant implementation

These links and excerpts are pinned to audit base 17f0b91a243ccfe4a38d27debdc983adf434e738.

packages/effect/src/unstable/eventlog/EventLogServerUnencrypted.ts:396-423

View problematic code at packages/effect/src/unstable/eventlog/EventLogServerUnencrypted.ts:396-423

const toConflicts = (
  history: ReadonlyArray<Entry>,
  originEntry: Entry
): [duplicate: boolean, conflicts: Array<Entry>, newHistory: Array<Entry>] => {
  let duplicate = false

  for (let i = 0; i < history.length; i++) {
    const entry = history[i]
    if (entry.createdAtMillis < originEntry.createdAtMillis) {
      continue
    } else if (entry.idString === originEntry.idString) {
      duplicate = true
      continue
    }

    const newHistory = history.slice(i)
    let conflicts: Array<Entry> = []
    for (let j = 0; j < newHistory.length; j++) {
      const scannedEntry = history[j]!
      if (scannedEntry.event === originEntry.event && scannedEntry.primaryKey === originEntry.primaryKey) {
        conflicts.push(scannedEntry)
      }
    }
    return [duplicate, conflicts, newHistory]
  }

  return [duplicate, [], []]
}

View exact lines on GitHub

Reproduction

pnpm test --run packages/effect/test/unstable/eventlog/UnencryptedEventLogConflictIndex.test.ts

Observed failure: Focused contract assertion failed against 17f0b91, demonstrating: Conflict scanning indexes the wrong history array.

Implementation handoff

The initial reproduction tests on this branch are the regression specification for the implementation fix that should follow in this PR.

Start with the pinned implementation excerpts and the Why it happens analysis above.
Change the implementation so it satisfies the stated Expected behavior; do not weaken or remove the reproduction assertions.
Run the focused reproduction command(s) and confirm the observed failures become passing tests:

pnpm test --run packages/effect/test/unstable/eventlog/UnencryptedEventLogConflictIndex.test.ts

Run the affected package's existing tests, then the repository lint and type checks before requesting review.

Audit provenance

Audit base: 17f0b91a243ccfe4a38d27debdc983adf434e738
Reproduction base: 17f0b91a243ccfe4a38d27debdc983adf434e738
Findings: effect-64c8be87a9a44e92
Initial patch: focused reproduction tests; implementation fix pending

Closes EFF-469

changeset-bot · 2026-08-05T15:01:48Z

🦋 Changeset detected

Latest commit: 43e6c61

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

This PR includes changesets to release 30 packages

Name	Type
effect	Patch
@effect/ai-anthropic	Patch
@effect/ai-openai	Patch
@effect/ai-openai-compat	Patch
@effect/ai-openrouter	Patch
@effect/atom-react	Patch
@effect/atom-solid	Patch
@effect/atom-vue	Patch
@effect/docgen	Patch
@effect/doctest	Patch
@effect/openapi-generator	Patch
@effect/opentelemetry	Patch
@effect/platform-browser	Patch
@effect/platform-bun	Patch
@effect/platform-deno	Patch
@effect/platform-node	Patch
@effect/platform-node-shared	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/vitest	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

pullfrog

Important

This PR currently contains only the reproduction test; the implementation fix it documents is not yet present. CI is expected to fail until toConflicts is fixed, so treat this review as feedback on the regression test and the path to the fix.

Reviewed changes

Added packages/effect/test/unstable/eventlog/UnencryptedEventLogConflictIndex.test.ts, a focused regression test that exercises EventLogServerUnencrypted.processEntries through the EventLog.WriteSingle RPC path.

^{｜ ⚠️ this action is pinned to a commit SHA, which freezes the cleanup step — switch to @v0 or keep the SHA fresh with Dependabot ｜ Fix all ➔ ｜ Fix 👍s ➔ ｜ View workflow run ｜ Using Kimi K2 (free via Pullfrog for OSS) ｜ 𝕏}

pullfrog

Important

The incremental change moves and adapts the regression test, but the toConflicts source fix is still absent on this branch and the new test file is not formatted.

Reviewed changes

Moved the reproduction from UnencryptedEventLogConflictIndex.test.ts into EventLogServerUnencrypted.test.ts and adapted registerHandlerUnsafe to the current { event, handler } API shape.
Verified the test still fails against the unfixed implementation with the expected [oldSameKey] vs [newerSameKey] mismatch.

⚠️ Source fix still missing and test file unformatted

The implementation fix for toConflicts is not present: packages/effect/src/unstable/eventlog/EventLogServerUnencrypted.ts:414 still reads history[j] instead of newHistory[j]. The new test file also fails pnpm dprint check — run pnpm dprint fmt on it before the next push.

The existing review thread on the line-106 assertion about also capturing originA's conflicts remains open and would make the regression test strictly stronger.

^{｜ ⚠️ this action is pinned to a commit SHA, which freezes the cleanup step — switch to @v0 or keep the SHA fresh with Dependabot ｜ Fix it ➔ ｜ View workflow run ｜ Using Kimi K2 (free via Pullfrog for OSS) ｜ 𝕏}

pullfrog

✅ No new issues found.

Reviewed changes

Applied the one-line source fix in packages/effect/src/unstable/eventlog/EventLogServerUnencrypted.ts so toConflicts scans newHistory[j] instead of history[j], matching the suffix it intended to examine.
Strengthened the regression test in packages/effect/test/unstable/eventlog/EventLogServerUnencrypted.test.ts to assert conflicts for both originA (expected []) and originB (expected [newerSameKey.idString]), covering both the false-positive and false-negative sides of the bug.

^{｜ ⚠️ this action is pinned to a commit SHA, which freezes the cleanup step — switch to @v0 or keep the SHA fresh with Dependabot ｜ View workflow run ｜ Using Kimi K2 (free via Pullfrog for OSS) ｜ 𝕏}

github-actions · 2026-08-05T20:41:17Z

Bundle Size Analysis

Generated from PR build output; treat the content below as untrusted.

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`schema.ts`	18.52 KB	18.52 KB	0.00 KB (0.00%)
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`stream.ts`	9.80 KB	9.80 KB	0.00 KB (0.00%)

pullfrog

✅ No new issues found.

Reviewed changes

Added .changeset/tidy-cats-smile.md with a patch-level changeset describing the unencrypted event log conflict-scanning fix.
Removed the redundant Effect.scoped wrapper from the regression test in packages/effect/test/unstable/eventlog/EventLogServerUnencrypted.test.ts; it.effect already applies Effect.scoped internally, so the wrapper only created an unnecessary child scope.

^{｜ ⚠️ this action is pinned to a commit SHA, which freezes the cleanup step — switch to @v0 or keep the SHA fresh with Dependabot ｜ View workflow run ｜ Using Kimi K2 (free via Pullfrog for OSS) ｜ 𝕏}

Fix conflict scanning indexes the wrong history array

3637eea

fubhy added the audit Findings originating from the Effect runtime correctness audit label Aug 5, 2026

pullfrog Bot reviewed Aug 5, 2026

View reviewed changes

Comment thread packages/effect/test/unstable/eventlog/EventLogServerUnencrypted.test.ts Outdated

Move reproduction into EventLogServerUnencrypted tests

0962109

pullfrog Bot requested changes Aug 5, 2026

View reviewed changes

fubhy and others added 2 commits August 5, 2026 15:45

Format EventLogServerUnencrypted reproduction

101216f

Fix unencrypted eventlog conflict scanning

b13f509

pullfrog Bot approved these changes Aug 5, 2026

View reviewed changes

tim-smart reviewed Aug 5, 2026

View reviewed changes

Comment thread packages/effect/test/unstable/eventlog/EventLogServerUnencrypted.test.ts Outdated

Address eventlog review feedback

43e6c61

pullfrog Bot approved these changes Aug 5, 2026

View reviewed changes

tim-smart merged commit eaa7e71 into main Aug 5, 2026
20 checks passed

tim-smart deleted the audit/repro-17f0b91a-unencrypted-eventlog-conflict-index branch August 5, 2026 21:30

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Fix conflict scanning indexes the wrong history array - #7029

Fix conflict scanning indexes the wrong history array#7029
tim-smart merged 5 commits into
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audit/repro-17f0b91a-unencrypted-eventlog-conflict-index

fubhy commented Aug 5, 2026 •

edited by tim-smart

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fubhy commented Aug 5, 2026 • edited by tim-smart Loading Uh oh! There was an error while loading. Please reload this page.

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Summary

Conflict scanning indexes the wrong history array

What happens

Why it happens

Expected behavior

Relevant implementation

Reproduction

Implementation handoff

Audit provenance

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changeset-bot Bot commented Aug 5, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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⚠️ Source fix still missing and test file unformatted

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github-actions Bot commented Aug 5, 2026

Bundle Size Analysis

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fubhy commented Aug 5, 2026 •

edited by tim-smart

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