[core] Fix setAttributes() resolution bypassing delivery barriers by pranaygp · Pull Request #4861 · vercel/workflow

pranaygp · 2026-10-13T20:46:01Z

Closes #4770.

Problem

When setAttributes() resolves, its attr_set acknowledgement settled straight off promiseQueue without registering a delivery barrier. Every other delivery that resumes a branch (step results, waits, hook payloads and, since #4215, hook registration outcomes) registers one and waits for earlier deliveries. A branch awaiting setAttributes() could therefore resume ahead of a sibling's step result that comes earlier in the log, and draw that sibling's next correlation ID. Depending on what the sibling draws next, the run either fails with REPLAY_DIVERGENCE, or both branches call the same step and silently receive each other's results.

Fix

Add an attribute DeliveryKind. It defers behind every earlier kind, and every kind defers behind an earlier attribute. Like a step, it skips unclaimed buffered hook payloads, because resolving it never depends on a hook read.
attribute-dispatcher.ts registers the barrier and captures awaitEarlierDeliveries when it consumes the event, then resolves from a continuation that is detached from the queue tail, following the same pattern as sleep.ts.
setAttributes() resolution still does not move the workflow clock. registerDeliveryBarrier now accepts deliveredAt: null to opt out explicitly.
The QuickJS runtime needs no change. It delivers events strictly in log order and drains jobs after each one.

Tests

set-attributes-delivery-order.test.ts drives the two shapes from the issue against an in-memory event log and replays the committed log in fresh VMs with cold and warm caches. It covers both WORKFLOW_LOG_ORDER_DRAWS modes and several hop counts. On main all 16 cases fail (CI confirmed this on the first commit). With the fix they all pass.
Full core suite passes locally: 3073 passed, 6 expected failures.
I ran the reporter's standalone reproduction (published workflow@5.2.1 / @workflow/vitest@5.0.4, 32 runs per workflow). Stock 5.2.1 fails attrSwap in 25–32 of 32 runs and attrVsHook in 4–24 of 32 runs. With this build of @workflow/core swapped in, all four tests pass in both draw modes.

Note on in-flight runs

Unlike #4848, this does not pin the old ordering for runs started before the upgrade. The old ordering was not a deterministic function of the log for the reported shapes. Even so, a history that recorded setAttributes() winning a Promise.race against an earlier-in-log delivery could replay differently once these runs continue on the new SDK. #4848 handles that case with a per-run marker. Maintainers should decide whether that gating is worth the extra surface.

🤖 Generated with Claude Code

…ing (#4770) Co-Authored-By: Claude <noreply@anthropic.com> Signed-off-by: Pranay Prakash <1797812+pranaygp@users.noreply.github.com> Co-Authored-By: Pranay Prakash <1797812+pranaygp@users.noreply.github.com>

changeset-bot · 2026-10-13T20:46:06Z

🦋 Changeset detected

Latest commit: c005102

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

This PR includes changesets to release 17 packages

Name	Type
@workflow/core	Patch
@workflow/builders	Patch
@workflow/cli	Patch
@workflow/next	Patch
@workflow/nitro	Patch
@workflow/vitest	Patch
@workflow/web-shared	Patch
@workflow/web	Patch
workflow	Patch
@workflow/world-testing	Patch
@workflow/astro	Patch
@workflow/nest	Patch
@workflow/rollup	Patch
@workflow/sveltekit	Patch
@workflow/vite	Patch
@workflow/nuxt	Patch
@workflow/world-vercel	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

vercel · 2026-10-13T20:46:10Z

The latest updates on your projects. Learn more about Vercel for GitHub.

Project	Deployment	Actions	Updated
example-nextjs-workflow-turbopack	Ready	Preview, v0	Oct 13, 2026 8:57pm UTC
example-nextjs-workflow-webpack	Ready	Preview, v0	Oct 13, 2026 8:57pm UTC
example-workflow	Ready	Preview, v0	Oct 13, 2026 8:57pm UTC
workbench-astro-workflow	Ready	Preview, v0	Oct 13, 2026 8:57pm UTC
workbench-express-workflow	Ready	Preview, v0	Oct 13, 2026 8:57pm UTC
workbench-fastify-workflow	Ready	Preview, v0	Oct 13, 2026 8:57pm UTC
workbench-hono-workflow	Ready	Preview, v0	Oct 13, 2026 8:57pm UTC
workbench-nestjs-workflow	Ready	Preview, v0	Oct 13, 2026 8:57pm UTC
workbench-nitro-workflow	Ready	Preview, v0	Oct 13, 2026 8:57pm UTC
workbench-nuxt-workflow	Ready	Preview, v0	Oct 13, 2026 8:57pm UTC
workbench-python-workflow	Ready	Preview, v0	Oct 13, 2026 8:57pm UTC
workbench-sveltekit-workflow	Ready	Preview, v0	Oct 13, 2026 8:57pm UTC
workbench-tanstack-start-workflow	Ready	Preview, v0	Oct 13, 2026 8:57pm UTC
workbench-vite-workflow	Ready	Preview, v0	Oct 13, 2026 8:57pm UTC
workflow-docs	Ready	Preview, v0	Oct 13, 2026 8:57pm UTC
workflow-swc-playground	Ready	Preview, v0	Oct 13, 2026 8:57pm UTC
workflow-tarballs	Ready	Preview, v0	Oct 13, 2026 8:57pm UTC
workflow-web	Ready	Preview, v0	Oct 13, 2026 8:57pm UTC

github-actions · 2026-10-13T20:46:45Z

📊 Workflow Benchmarks

commit c005102 · Tue, 13 Oct 2026 21:13:41 GMT · run logs

Backend: vercel · app: nextjs-turbopack

Metric	Scenario	Best (ms)	P75 (ms)	P90 (ms)	P99 (ms)	Samples
TTFS	step	1621 (+41%) 🔻	1927 🔴 (+9.4%)	1955 🔴 (+8.3%)	1982 🔴 (+8.1%)	30
TTFS	stream	1819 (+24%) 🔻	1903 🔴 (+14%)	1933 🔴 (+9.4%)	2079 🔴 (+16%) 🔻	30
TTFS	hook + stream	1800 (+3.9%)	2247 🔴 (+15%) 🔻	2289 🔴 (+14%)	5330 🔴 (+146%) 🔻	30
Fan-out TTFS	Promise.all(100 steps)	524 (-5.9%)	2274 (+205%) 🔻	2367 (+182%) 🔻	2671 (+44%) 🔻	10
Fan-out TTLS	Promise.all(100 steps)	2660 (+46%) 🔻	5875 (+28%) 🔻	6355 (+31%) 🔻	6828 (+0.9%)	10
STSO	1020 steps (inline)	87 (±0%)	102 (-11%)	119 (-12%)	148 (-18%) 💚	1019
WO	1020 steps	103592 (-8.6%)	103592 (-8.6%)	103592 (-8.6%)	103592 (-8.6%)	1

📈 STSO distribution vs main (inline / queue-hop histograms)

1020 steps (inline)

Cumulative STSO time: main 113014ms → this run 103375ms (Δ -9639ms, -9%)

 50-100 ms  █████████░░░░░░░░░░░░┃    main 275  this 649  +374
100-150 ms  ███████████┃████████████  main 703  this 360  -343
150-200 ms  ┃                         main  35  this   8   -27
200-250 ms  ┃                         main   4  this   2    -2
250-300 ms  ┃                         main   2  this   0    -2

ℹ️ Metric definitions & methodology

_{The collapsed STSO distribution section above buckets every step gap, split inline (same warm process — pure framework overhead) vs queue-hop (fresh process — dispatch, reinit, replay). █ = main, ┃ = this run, ░ = fill.}

_{Best/P75/P90/P99 deltas compare against the most recent benchmark run on main at the time of this run. 🔻 flags a delta worse than +15%, 💚 one better than −15%.}

_{Metrics — TTFS: time to first step body (in-deployment start() → first step body) · Fan-out TTFS: fan-out time to first step (in-deployment start() → first of the parallel step bodies to complete) · Fan-out TTLS: fan-out time to last step (in-deployment start() → last of the parallel step bodies to complete, i.e. when the Promise.all resolves) · STSO: step-to-step overhead (gap between consecutive step bodies) · WO: workflow overhead (whole-run time outside step bodies, in-deployment anchored)}

_{Scenarios — step: one trivial no-op step, no stream; no hooks, so the run stays in turbo mode (in-process fast path) · stream: one streaming step; no hooks, so the run stays in turbo mode (in-process fast path) · hook + stream: registers a hook before one step, which exits turbo mode (dispatch path) · 1020 steps: 1020 trivial sequential steps; STSO is measured between consecutive steps in the given step ranges, and WO is the whole-run overhead outside step bodies · Promise.all(100 steps): 100 trivial no-op steps started together in a single Promise.all; Fan-out TTFS is the first of them to complete and Fan-out TTLS the last, both from the in-deployment clientStart, so their gap is the spread the runtime adds across the fan-out}

_{🔴 marks a percentile over its target (within target is left unmarked). Targets (p75/p90/p99, ms) — TTFS 200/300/600}

_{All timestamps are deployment-side; runs are triggered in-deployment, so the CI runner and api.vercel.com sit outside every measured window. TTFS = start() → first step body (includes dispatch + any cold start); Fan-out TTFS/TTLS = first/last step completion of one Promise.all from the same anchor (the gap is the runtime’s fan-out spread); STSO/WO between step bodies. Streaming delivery performance is measured in durabench.}

_{Cold starts stay in the numbers (real bursty-workload latency, inflates P75+); Best is the warm floor.}

github-actions · 2026-10-13T20:46:45Z

🧪 E2E Test Results

✅ All tests passed

⚠️ Flaky E2E Tests (passed on retry)

These tests failed at least once and passed on a retry. A recurring entry here is a real race worth investigating.

abortHookOrderingWorkflow [hook-first-abort-first]: hook.then → addEventListener → abort() → resumeHook (nextjs-webpack · local-dev / local / node / canary)
abortHookOrderingWorkflow [hook-first-hook-first]: hook.then → addEventListener → resumeHook → abort() (nextjs-webpack · local-dev / local / node / canary)
abortHookOrderingWorkflow [listener-first-abort-first]: addEventListener → hook.then → abort() → resumeHook (nextjs-webpack · local-dev / local / node / canary)
abortHookOrderingWorkflow [listener-first-hook-first]: addEventListener → hook.then → resumeHook → abort() (nextjs-webpack · local-dev / local / node / canary)
hookGetConflictThenStepParallelWorkflow - hook.getConflict() continuation step runs alongside other steps (nextjs-webpack · local-dev / local / node / stable)
resumes in flight during the takeover are never lost: each lands in exactly one log (nuxt · local-prod / local / quickjs / stable)

🛠 Infra Events (absorbed by the harness)

Platform anomalies the e2e harness detected and worked around (e.g. a run the queue never picked up, replaced by a fresh run). Clustered timestamps indicate a backend blip; a steady drip indicates a platform issue worth escalating.

run-pickup-stall · runs app-generated source against a registered step (tanstack-start) · at 21:11:05Z · abandoned wrun_01M4VHN4EHWNNDJ9W4B96SA3ZT
cold-start-warmup · suite warmup (tanstack-start) · at 21:11:09Z · abandoned wrun_01M4VHN4ENA2DQW57G0MHM7MFK
run-pickup-stall · hookCleanupTestWorkflow - hook token reuse after workflow completion (nextjs-webpack) · at 21:17:36Z · abandoned wrun_01M4VJ121A30DWFH56AN09XF1K

E2E Test Summary

Summary

	Passed	Skipped	Total
✅ ▲ Vercel Production	3982	878	4860
✅ 💻 Local Development	4669	551	5220
✅ 📦 Local Production	4669	551	5220
✅ 🐘 Local Postgres	4669	551	5220
✅ 🪟 Windows	348	12	360
✅ 🌐 Cross-language Conformance	68	87	155
✅ dynamic-runs	0	0	0
✅ vercel-http-transport	897	183	1080
✅ vercel-multi-region	27	0	27
✅ vercel-ws-transport	607	113	720
Total	19936	2926	22862

Details by Category

✅ ▲ Vercel Production

App	Passed	Skipped
✅ astro-node	145	35
✅ astro-quickjs	145	35
✅ example-node	145	35
✅ example-quickjs	145	35
✅ express-node	145	35
✅ express-quickjs	145	35
✅ fastify-node	145	35
✅ fastify-quickjs	145	35
✅ hono-node	145	35
✅ hono-quickjs	145	35
✅ nest-node	145	35
✅ nest-quickjs	145	35
✅ nextjs-turbopack-node	172	8
✅ nextjs-turbopack-quickjs	172	8
✅ nextjs-webpack-node	172	8
✅ nextjs-webpack-quickjs	172	8
✅ nitro-node	145	35
✅ nitro-quickjs	145	35
✅ nuxt-node	145	35
✅ nuxt-quickjs	145	35
✅ python-node	66	114
✅ sveltekit-node	164	16
✅ sveltekit-quickjs	164	16
✅ tanstack-start-node	145	35
✅ tanstack-start-quickjs	145	35
✅ vite-node	145	35
✅ vite-quickjs	145	35

✅ 💻 Local Development

App	Passed	Skipped
✅ astro-stable-node	151	29
✅ astro-stable-quickjs	151	29
✅ express-stable-node	151	29
✅ express-stable-quickjs	151	29
✅ fastify-stable-node	151	29
✅ fastify-stable-quickjs	151	29
✅ hono-stable-node	151	29
✅ hono-stable-quickjs	151	29
✅ nest-stable-node	151	29
✅ nest-stable-quickjs	151	29
✅ nextjs-turbopack-canary-node	179	1
✅ nextjs-turbopack-canary-quickjs	179	1
✅ nextjs-turbopack-quickjs-snapshot	179	1
✅ nextjs-turbopack-stable-node	179	1
✅ nextjs-turbopack-stable-quickjs	179	1
✅ nextjs-webpack-canary-node	179	1
✅ nextjs-webpack-canary-quickjs	179	1
✅ nextjs-webpack-stable-node	179	1
✅ nextjs-webpack-stable-quickjs	179	1
✅ nitro-stable-node	151	29
✅ nitro-stable-quickjs	151	29
✅ nuxt-stable-node	151	29
✅ nuxt-stable-quickjs	151	29
✅ sveltekit-stable-node	170	10
✅ sveltekit-stable-quickjs	170	10
✅ tanstack-start-node	151	29
✅ tanstack-start-quickjs	151	29
✅ vite-stable-node	151	29
✅ vite-stable-quickjs	151	29

✅ 📦 Local Production

App	Passed	Skipped
✅ astro-stable-node	151	29
✅ astro-stable-quickjs	151	29
✅ express-stable-node	151	29
✅ express-stable-quickjs	151	29
✅ fastify-stable-node	151	29
✅ fastify-stable-quickjs	151	29
✅ hono-stable-node	151	29
✅ hono-stable-quickjs	151	29
✅ nest-stable-node	151	29
✅ nest-stable-quickjs	151	29
✅ nextjs-turbopack-canary-node	179	1
✅ nextjs-turbopack-canary-quickjs	179	1
✅ nextjs-turbopack-quickjs-snapshot	179	1
✅ nextjs-turbopack-stable-node	179	1
✅ nextjs-turbopack-stable-quickjs	179	1
✅ nextjs-webpack-canary-node	179	1
✅ nextjs-webpack-canary-quickjs	179	1
✅ nextjs-webpack-stable-node	179	1
✅ nextjs-webpack-stable-quickjs	179	1
✅ nitro-stable-node	151	29
✅ nitro-stable-quickjs	151	29
✅ nuxt-stable-node	151	29
✅ nuxt-stable-quickjs	151	29
✅ sveltekit-stable-node	170	10
✅ sveltekit-stable-quickjs	170	10
✅ tanstack-start-node	151	29
✅ tanstack-start-quickjs	151	29
✅ vite-stable-node	151	29
✅ vite-stable-quickjs	151	29

✅ 🐘 Local Postgres

App	Passed	Skipped
✅ astro-stable-node	151	29
✅ astro-stable-quickjs	151	29
✅ express-stable-node	151	29
✅ express-stable-quickjs	151	29
✅ fastify-stable-node	151	29
✅ fastify-stable-quickjs	151	29
✅ hono-stable-node	151	29
✅ hono-stable-quickjs	151	29
✅ nest-stable-node	151	29
✅ nest-stable-quickjs	151	29
✅ nextjs-turbopack-canary-node	179	1
✅ nextjs-turbopack-canary-quickjs	179	1
✅ nextjs-turbopack-quickjs-snapshot	179	1
✅ nextjs-turbopack-stable-node	179	1
✅ nextjs-turbopack-stable-quickjs	179	1
✅ nextjs-webpack-canary-node	179	1
✅ nextjs-webpack-canary-quickjs	179	1
✅ nextjs-webpack-stable-node	179	1
✅ nextjs-webpack-stable-quickjs	179	1
✅ nitro-stable-node	151	29
✅ nitro-stable-quickjs	151	29
✅ nuxt-stable-node	151	29
✅ nuxt-stable-quickjs	151	29
✅ sveltekit-stable-node	170	10
✅ sveltekit-stable-quickjs	170	10
✅ tanstack-start-node	151	29
✅ tanstack-start-quickjs	151	29
✅ vite-stable-node	151	29
✅ vite-stable-quickjs	151	29

✅ 🪟 Windows

App	Passed	Failed	Skipped
✅ nextjs-turbopack-node	174	0	6
✅ nextjs-turbopack-quickjs	174	0	6

✅ 🌐 Cross-language Conformance

App	Passed	Failed	Skipped
✅ python	68	0	87

✅ dynamic-runs

App	Passed	Failed	Skipped
✅ astro-vercel	0	0	0
✅ example-vercel	0	0	0
✅ express-vercel	0	0	0
✅ fastify-vercel	0	0	0
✅ hono-vercel	0	0	0
✅ nest-vercel	0	0	0
✅ nextjs-turbopack-vercel	0	0	0
✅ nextjs-webpack-vercel	0	0	0
✅ nitro-vercel	0	0	0
✅ nuxt-vercel	0	0	0
✅ sveltekit-vercel	0	0	0
✅ tanstack-start-vercel	0	0	0
✅ vite-vercel	0	0	0

✅ vercel-http-transport

App	Passed	Skipped
✅ example	145	35
✅ express	145	35
✅ hono	145	35
✅ nextjs-turbopack	172	8
✅ nitro	145	35
✅ vite	145	35

✅ vercel-multi-region

App	Passed	Failed	Skipped
✅ nextjs-turbopack	27	0	0

✅ vercel-ws-transport

App	Passed	Skipped
✅ example	145	35
✅ express	145	35
✅ nextjs-turbopack	172	8
✅ vite	145	35

📋 View full workflow run

github-actions · 2026-10-13T20:49:32Z

Sim World

Simulated world deterministic testing for races. Traces

🟢 world-sim scenario book — 0 fail of 42 total

fence=per-spec

scenario	outcome	events	virt	replay
✅ `smoke-no-steps`	completed	3	0ms	ok
✅ `smoke-one-step`	completed	6	0ms	ok
✅ `hook-at-step-started`	completed	12	0ms	ok
✅ `hook-at-step-completed`	completed	12	0ms	ok
✅ `hook-at-hook-created`	completed	12	0ms	ok
✅ `deadline-hook-wins`	completed	7	1.0h	ok
✅ `deadline-expires`	completed	7	1.0h	ok
✅ `step-vs-timer-early-settlement`	completed	8	1.0h	ok
✅ `long-sleep`	completed	11	30.0d	ok
✅ `hook-never-arrives`	stalled	3	0ms	skipped
✅ `step-retries-twice`	completed	10	2.0s	ok
✅ `parallel-steps`	completed	9	0ms	ok
✅ `hook-on-execution-state`	completed	12	0ms	ok
✅ `peek-hook-before-branch`	completed	12	0ms	ok
✅ `peek-hook-after-branch`	completed	12	0ms	ok
✅ `peek-hook-at-registration`	completed	12	0ms	ok
✅ `race-hook-before-probe`	completed	12	0ms	ok
✅ `race-hook-after-probe`	completed	12	0ms	ok
✅ `race-duplicate-delivery`	completed	13	0ms	ok
✅ `attr-hook-before-step`	completed	11	0ms	ok
✅ `attr-hook-after-step`	completed	11	0ms	ok
✅ `attr-from-step-body`	completed	13	0ms	ok
✅ `fork-hook-after-timeout`	completed	14	1.0m	ok
✅ `fork-hook-before-timeout`	completed	14	1.0m	ok
✅ `count-hook-after-timeout`	completed	17	1.0m	ok
✅ `count-hook-before-timeout`	completed	20	1.0m	ok
✅ `stale-read-step-count-fork`	completed	20	1.0m	ok
✅ `stale-read-equal-step-counts`	completed	14	1.0m	ok
✅ `step-vs-step-fork`	completed	12	0ms	ok
✅ `step-vs-step-fork-fenced`	completed	12	0ms	ok
✅ `fence-catches-benign-direction`	completed	12	5ms	ok
✅ `in-flight-before-decision`	completed	17	1.0m	ok
✅ `in-flight-before-decision-counted`	completed	17	1.0m	ok
✅ `in-flight-after-decision`	completed	19	2.0m	ok
✅ `stale-read-step-count-fork-fenced`	completed	20	1.0m	ok
✅ `fork-hook-wins`	completed	13	1.0m	ok
✅ `fork-timeout-wins`	completed	13	1.0m	ok
✅ `unclaimed-payload-under-fork`	completed	17	1.0m	ok
✅ `claimed-payload-under-fork`	completed	17	1.0m	ok
✅ `writers-independent-step-bodies`	completed	12	0ms	ok
✅ `writers-scripted-tempo`	completed	12	0ms	ok
✅ `cancel-mid-step`	cancelled	7	0ms	skipped

Full trace: world-sim.txt

github-actions · 2026-10-13T20:53:51Z

Framework	Flow route	Step reg.	Framework output
hono	267.4 KiB (±0)	95.5 KiB (±0)	1.99 MiB (+246 B)
nextjs-turbopack	274.8 KiB (±0)	426 B (±0)	970.8 KiB (+34 B)

About these numbers

Sizes are gzip; parentheses show the change against main.
Flow route and Step reg. gate this job, on raw bytes rather than the gzip shown, at max(2%, 50.0 KiB). Framework output is informational.

c005102 · run

…4770) Register the attr_set acknowledgement as an 'attribute' delivery barrier at its log index and resolve setAttributes() only after every earlier delivery it defers behind has been handed to the workflow. Every other kind defers behind an earlier attribute too. The clock is left untouched, as before. Co-Authored-By: Claude <noreply@anthropic.com> Signed-off-by: Pranay Prakash <1797812+pranaygp@users.noreply.github.com> Co-Authored-By: Pranay Prakash <1797812+pranaygp@users.noreply.github.com>

VaguelySerious

AI review: no blocking issues

VaguelySerious · 2026-10-13T21:37:03Z

+      // The ordering is captured here, at consumption time, for the same
+      // reason as in step.ts and sleep.ts.
+      const eventIndex = ctx.eventsConsumer.eventIndex;
+      const barrier = registerDeliveryBarrier(ctx, eventIndex, 'attribute', {


AI Review: Note

This overlaps with #4848, which also closes #4770 and adds a per-run marker so runs started before the upgrade keep the old ordering. This PR follows the #4215 precedent (hook registration outcomes were moved onto the barriers without gating), which I think is reasonable here: I could not build a history where the old ordering was deterministic and the new one picks a different winner. Re-recording three extra shapes on the base commit and on this branch (unawaited setAttributes() alongside a pending step, setAttributes() in a Promise.all with a sleep and an earlier step, and setAttributes() while a hook payload sits buffered and unclaimed) gave identical outputs and resolution order in both draw modes, with cold and warm cache replays stable. One of the two PRs should be closed before merge.

VaguelySerious · 2026-10-13T21:37:03Z

+        // Attribute writes have never moved the workflow clock.
+        deliveredAt: null,
      });
+      const earlierDelivered = awaitEarlierDeliveries(


AI Review: Note

With log-order draws on (the default), every setAttributes() resolution now pays the quiesce turn in awaitEarlierDeliveries, even when nothing earlier is in flight. I measured a 30-iteration sequential setAttributes() loop: replay went from ~37ms to ~40ms, so about 0.1ms per write. Fine for progress-style attribute updates; noting it in case someone writes attributes in a tight loop.

github-actions · 2026-10-13T21:42:06Z

No backport to stable for afdc68b (AI decision).

This is a genuine correctness fix (REPLAY_DIVERGENCE / branches receiving each other's step results), but it targets functionality that does not exist on stable: git ls-tree origin/stable -- packages/core/src/workflow/attribute-dispatcher.ts shows the file is absent, and the only setAttributes references on stable are OpenTelemetry span.setAttributes() calls — the workflow-level setAttributes() primitive and its attribute queue item are main-only. The delivery-barrier machinery in private.ts does exist on stable, but the attribute DeliveryKind it adds would gate nothing there, so there is no defect to fix on the maintenance line.

To override, re-run the Backport to stable workflow manually via workflow_dispatch and paste this commit SHA into the ref input:

afdc68b8714036a01d8dcd5a023633ea544dc7fa

Catches the docs up with SDK changes that shipped in the last day without (complete) docs updates. | Change | Source PR | Docs edit | | --- | --- | --- | | QuickJS runs with snapshotting are exempt from the default per-run event limit on the Local and Vercel Worlds, and `MAX_EVENTS_EXCEEDED` / `REPLAY_TIMEOUT` now have their own error pages | #4870 | The error-code table in Errors and retries, the log-growth note in Event sourcing, and the event-limit row in What's new now mention the QuickJS exemption and link to the new error pages. #4870 updated the errors index, Runtime tuning, Worlds, and Vercel World pages but not these | I reviewed the other PRs from the last day and they need no further docs: removing the experimental resilient step dispatch (#4818) updated its own docs and the variable no longer appears outside changelogs, the `setAttributes()` delivery-order fix (#4861) and terminal-inert replay (#4819) are bug fixes, reading step creation from `step_started` (#4866) is reader-side forward compatibility with no user-facing change yet, and the devalue upgrade (#4856), dependency bumps, and Version Packages PRs aren't documented behavior. The Workflows pricing and limits page in `vercel/front` gets the matching event-limit note in vercel/front#91076. ## Docs Preview | Page | Preview | | --- | --- | | Errors and retries | [Error codes](https://workflow-docs-git-workflow-docs-cleanup-wed-14-oct.vercel.sh/docs/foundations/errors-and-retries) | | Event sourcing | [How fast a log grows](https://workflow-docs-git-workflow-docs-cleanup-wed-14-oct.vercel.sh/docs/how-it-works/event-sourcing#how-fast-a-log-grows) | | What's new | [Breaking changes: Application code](https://workflow-docs-git-workflow-docs-cleanup-wed-14-oct.vercel.sh/docs/whats-new#application-code) | 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-authored-by: vercel[bot] <35613825+vercel[bot]@users.noreply.github.com> Co-authored-by: Pranay Prakash <1797812+pranaygp@users.noreply.github.com>

Allow operators to select older runs whose saved decisions depend on the attribute delivery behavior before vercel#4861. Keep that choice for each replay session and retain ordered delivery for other runs. Cover old and newer histories with both draw-order settings, checking the inputs sent to a new step after replay. Signed-off-by: Muhammadjon Marufov <marufov254@gmail.com>

[core] Add failing regression test for setAttributes() delivery order…

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…ing (#4770) Co-Authored-By: Claude <noreply@anthropic.com> Signed-off-by: Pranay Prakash <1797812+pranaygp@users.noreply.github.com> Co-Authored-By: Pranay Prakash <1797812+pranaygp@users.noreply.github.com>

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pranaygp mentioned this pull request Oct 13, 2026

[core] setAttributes() resolution bypasses the delivery barriers, so a branch awaiting it can resume out of log order and draw another branch's correlation id (replay divergence, or step results delivered to the wrong branch) #4770

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VaguelySerious marked this pull request as ready for review October 13, 2026 21:32

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VaguelySerious merged commit afdc68b into main Oct 13, 2026
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VaguelySerious deleted the triage-4770-setattributes-barrier branch October 13, 2026 21:40

github-actions Bot mentioned this pull request Oct 13, 2026

Version Packages #4847

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mmarufov mentioned this pull request Oct 14, 2026

[core] Preserve legacy attribute ordering for selected runs #4848

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pranaygp mentioned this pull request Oct 14, 2026

[docs] Catch up docs with recently shipped SDK changes #4880

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[core] Fix setAttributes() resolution bypassing delivery barriers - #4861

[core] Fix setAttributes() resolution bypassing delivery barriers#4861
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