fix(offline-transactions): enforce strict FIFO when retries are pending

[KyleAMathews]

Summary

Enforce strict FIFO ordering in KeyScheduler.getNextBatch so that a transaction waiting for retry delay blocks all later transactions from executing. Previously, later transactions could jump the queue, causing dependent UPDATE-before-INSERT failures.

Root Cause

getNextBatch used .find() to locate any pending transaction that was ready to run. If the oldest transaction had failed and was in a retry backoff window (nextAttemptAt in the future), .find() would skip past it and return a later transaction that was ready. This violated the FIFO contract — a newer transaction could execute before an older one that it depended on.

Approach

Replace the .find() scan with a check on only this.pendingTransactions[0] (the oldest transaction). If it's not ready, return an empty batch. If it is ready, return it.

// Before: find ANY ready transaction (could skip the first)
const readyTransaction = this.pendingTransactions.find((tx) =>
  this.isReadyToRun(tx),
)

// After: only check the FIRST transaction (strict FIFO)
const firstTransaction = this.pendingTransactions[0]!
if (!this.isReadyToRun(firstTransaction)) {
  return []
}
return [firstTransaction]

The scheduleNextRetry mechanism in TransactionExecutor ensures that when the first transaction's retry delay elapses, execution resumes automatically.

Key Invariants

• The queue always processes in createdAt order — no transaction can execute before an older one
• When the head transaction is in retry backoff, the entire queue waits
• scheduleNextRetry provides the eventual recovery path after a break

Non-goals

• No changes to the retry/backoff timing logic itself
• No changes to TransactionExecutor or the execution loop
• Pre-existing concerns (e.g., markStarted/markFailed not validating transaction identity) are out of scope

Verification

pnpm --filter @tanstack/offline-transactions test -- KeyScheduler.test.ts

8 tests cover: FIFO blocking during retry, delay elapse, queue advancement after completion, isRunning guard, full retry-then-success lifecycle, out-of-order scheduling, updateTransaction sort preservation, and empty queue boundary.

Files Changed

• packages/offline-transactions/src/executor/KeyScheduler.ts — Replace .find() scan with strict first-element check; use non-null assertion after length guard
• packages/offline-transactions/tests/KeyScheduler.test.ts — New test file with 8 tests covering the FIFO ordering contract

---

🤖 Generated with Claude Code

[changeset-bot]

🦋 Changeset detected

Latest commit: 9dce679

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

This PR includes changesets to release 1 package

Name	Type
@tanstack/offline-transactions	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

[pkg-pr-new]

More templates

• todos
• tanstack-start-example-basic
• @tanstack/db-example-paced-mutations-demo
• tanstack-start-db-projects-example
• @tanstack/db-example-react-todo
• offline-transactions-react-native
• @tanstack/db-example-solid-todo

@tanstack/angular-db

npm i https://pkg.pr.new/@tanstack/angular-db@1300

@tanstack/db

npm i https://pkg.pr.new/@tanstack/db@1300

@tanstack/db-ivm

npm i https://pkg.pr.new/@tanstack/db-ivm@1300

@tanstack/electric-db-collection

npm i https://pkg.pr.new/@tanstack/electric-db-collection@1300

@tanstack/offline-transactions

npm i https://pkg.pr.new/@tanstack/offline-transactions@1300

@tanstack/powersync-db-collection

npm i https://pkg.pr.new/@tanstack/powersync-db-collection@1300

@tanstack/query-db-collection

npm i https://pkg.pr.new/@tanstack/query-db-collection@1300

@tanstack/react-db

npm i https://pkg.pr.new/@tanstack/react-db@1300

@tanstack/rxdb-db-collection

npm i https://pkg.pr.new/@tanstack/rxdb-db-collection@1300

@tanstack/solid-db

npm i https://pkg.pr.new/@tanstack/solid-db@1300

@tanstack/svelte-db

npm i https://pkg.pr.new/@tanstack/svelte-db@1300

@tanstack/trailbase-db-collection

npm i https://pkg.pr.new/@tanstack/trailbase-db-collection@1300

@tanstack/vue-db

npm i https://pkg.pr.new/@tanstack/vue-db@1300

commit: 9dce679

[github-actions]

Size Change: -2 B (0%)

Total Size: 92.6 kB

Filename	Size	Change
./packages/db/dist/esm/query/builder/index.js	4.09 kB	-2 B (-0.05%)

ℹ️ View Unchanged

Filename	Size
./packages/db/dist/esm/collection/change-events.js	1.39 kB
./packages/db/dist/esm/collection/changes.js	1.22 kB
./packages/db/dist/esm/collection/events.js	388 B
./packages/db/dist/esm/collection/index.js	3.32 kB
./packages/db/dist/esm/collection/indexes.js	1.1 kB
./packages/db/dist/esm/collection/lifecycle.js	1.75 kB
./packages/db/dist/esm/collection/mutations.js	2.34 kB
./packages/db/dist/esm/collection/state.js	3.49 kB
./packages/db/dist/esm/collection/subscription.js	3.71 kB
./packages/db/dist/esm/collection/sync.js	2.41 kB
./packages/db/dist/esm/deferred.js	207 B
./packages/db/dist/esm/errors.js	4.7 kB
./packages/db/dist/esm/event-emitter.js	748 B
./packages/db/dist/esm/index.js	2.69 kB
./packages/db/dist/esm/indexes/auto-index.js	742 B
./packages/db/dist/esm/indexes/base-index.js	766 B
./packages/db/dist/esm/indexes/btree-index.js	2.17 kB
./packages/db/dist/esm/indexes/lazy-index.js	1.1 kB
./packages/db/dist/esm/indexes/reverse-index.js	538 B
./packages/db/dist/esm/local-only.js	808 B
./packages/db/dist/esm/local-storage.js	2.1 kB
./packages/db/dist/esm/optimistic-action.js	359 B
./packages/db/dist/esm/paced-mutations.js	496 B
./packages/db/dist/esm/proxy.js	3.75 kB
./packages/db/dist/esm/query/builder/functions.js	733 B
./packages/db/dist/esm/query/builder/ref-proxy.js	1.05 kB
./packages/db/dist/esm/query/compiler/evaluators.js	1.43 kB
./packages/db/dist/esm/query/compiler/expressions.js	430 B
./packages/db/dist/esm/query/compiler/group-by.js	2.23 kB
./packages/db/dist/esm/query/compiler/index.js	2.04 kB
./packages/db/dist/esm/query/compiler/joins.js	2.11 kB
./packages/db/dist/esm/query/compiler/order-by.js	1.45 kB
./packages/db/dist/esm/query/compiler/select.js	1.09 kB
./packages/db/dist/esm/query/expression-helpers.js	1.43 kB
./packages/db/dist/esm/query/ir.js	673 B
./packages/db/dist/esm/query/live-query-collection.js	360 B
./packages/db/dist/esm/query/live/collection-config-builder.js	5.55 kB
./packages/db/dist/esm/query/live/collection-registry.js	264 B
./packages/db/dist/esm/query/live/collection-subscriber.js	2.42 kB
./packages/db/dist/esm/query/live/internal.js	145 B
./packages/db/dist/esm/query/optimizer.js	2.62 kB
./packages/db/dist/esm/query/predicate-utils.js	2.97 kB
./packages/db/dist/esm/query/subset-dedupe.js	921 B
./packages/db/dist/esm/scheduler.js	1.3 kB
./packages/db/dist/esm/SortedMap.js	1.3 kB
./packages/db/dist/esm/strategies/debounceStrategy.js	247 B
./packages/db/dist/esm/strategies/queueStrategy.js	428 B
./packages/db/dist/esm/strategies/throttleStrategy.js	246 B
./packages/db/dist/esm/transactions.js	2.9 kB
./packages/db/dist/esm/utils.js	924 B
./packages/db/dist/esm/utils/browser-polyfills.js	304 B
./packages/db/dist/esm/utils/btree.js	5.61 kB
./packages/db/dist/esm/utils/comparison.js	952 B
./packages/db/dist/esm/utils/cursor.js	457 B
./packages/db/dist/esm/utils/index-optimization.js	1.51 kB
./packages/db/dist/esm/utils/type-guards.js	157 B

_{compressed-size-action::db-package-size}

[github-actions]

Size Change: 0 B

Total Size: 3.7 kB

ℹ️ View Unchanged

Filename	Size
./packages/react-db/dist/esm/index.js	225 B
./packages/react-db/dist/esm/useLiveInfiniteQuery.js	1.17 kB
./packages/react-db/dist/esm/useLiveQuery.js	1.34 kB
./packages/react-db/dist/esm/useLiveSuspenseQuery.js	559 B
./packages/react-db/dist/esm/usePacedMutations.js	401 B

_{compressed-size-action::react-db-package-size}