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[e2e] Add label-gated event log race repro - #2159
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📊 Benchmark Results
workflow with no steps💻 Local Development
▲ Production (Vercel)
🔍 Observability: Express | Next.js (Turbopack) workflow with 1 step💻 Local Development
▲ Production (Vercel)
🔍 Observability: Express | Next.js (Turbopack) workflow with 10 sequential steps💻 Local Development
▲ Production (Vercel)
🔍 Observability: Express | Next.js (Turbopack) workflow with 25 sequential steps💻 Local Development
▲ Production (Vercel)
🔍 Observability: Express | Next.js (Turbopack) workflow with 50 sequential steps💻 Local Development
▲ Production (Vercel)
🔍 Observability: Express | Next.js (Turbopack) Promise.all with 10 concurrent steps💻 Local Development
▲ Production (Vercel)
🔍 Observability: Express | Next.js (Turbopack) Promise.all with 25 concurrent steps💻 Local Development
▲ Production (Vercel)
🔍 Observability: Express | Next.js (Turbopack) Promise.all with 50 concurrent steps💻 Local Development
▲ Production (Vercel)
🔍 Observability: Express | Next.js (Turbopack) Promise.race with 10 concurrent steps💻 Local Development
▲ Production (Vercel)
🔍 Observability: Express | Next.js (Turbopack) Promise.race with 25 concurrent steps💻 Local Development
▲ Production (Vercel)
🔍 Observability: Express | Next.js (Turbopack) Promise.race with 50 concurrent steps💻 Local Development
▲ Production (Vercel)
🔍 Observability: Express | Next.js (Turbopack) workflow with 10 sequential data payload steps (10KB)💻 Local Development
▲ Production (Vercel)
🔍 Observability: Express | Next.js (Turbopack) workflow with 25 sequential data payload steps (10KB)💻 Local Development
▲ Production (Vercel)
🔍 Observability: Express | Next.js (Turbopack) workflow with 50 sequential data payload steps (10KB)💻 Local Development
▲ Production (Vercel)
🔍 Observability: Express | Next.js (Turbopack) workflow with 10 concurrent data payload steps (10KB)💻 Local Development
▲ Production (Vercel)
🔍 Observability: Next.js (Turbopack) | Express workflow with 25 concurrent data payload steps (10KB)💻 Local Development
▲ Production (Vercel)
🔍 Observability: Express | Next.js (Turbopack) workflow with 50 concurrent data payload steps (10KB)💻 Local Development
▲ Production (Vercel)
🔍 Observability: Express | Next.js (Turbopack) Stream Benchmarks(includes TTFB metrics)workflow with stream💻 Local Development
▲ Production (Vercel)
🔍 Observability: Express | Next.js (Turbopack) stream pipeline with 5 transform steps (1MB)💻 Local Development
▲ Production (Vercel)
🔍 Observability: Express | Next.js (Turbopack) 10 parallel streams (1MB each)💻 Local Development
▲ Production (Vercel)
🔍 Observability: Express | Next.js (Turbopack) fan-out fan-in 10 streams (1MB each)💻 Local Development
▲ Production (Vercel)
🔍 Observability: Next.js (Turbopack) | Express SummaryFastest Framework by WorldWinner determined by most benchmark wins
Fastest World by FrameworkWinner determined by most benchmark wins
Column Definitions
Worlds:
❌ Some benchmark jobs failed:
Check the workflow run for details. |
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🧪 E2E Test Results✅ All tests passed Summary
Details by Category✅ ▲ Vercel Production
✅ 💻 Local Development
✅ 📦 Local Production
✅ 🐘 Local Postgres
✅ 🪟 Windows
✅ 📋 Other
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Event Log Race Repro1 of 2000 latest repro runs did not complete cleanly. Run History
Latest Scenario Breakdown
Latest Non-Completed Runs
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TooTallNate
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May 30, 2026
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Approve — well-built diagnostic harness, doing exactly what it claims
This is a real and useful piece of infrastructure. The harness has caught the ~0.2% baseline CORRUPTED_EVENT_LOG rate consistently across 4 separate CI runs (1, 2, 3, 1 races detected over 1500-2000 attempts), which validates both the hypothesis and the harness itself.
Architecture is clean
- Label-gated (
event-log-race-reprolabel OR manual dispatch) — won't run on every PR - All scenarios in one test with shared deployment, sequential execution per scenario, parallel within
- Three scenario classes stressing different replay races:
- hook-sleep
Promise.race([hook, sleep])— classic - step-fanout with parallel-step replays acting on stale logs
- step-sleep-race biased both ways (step wins / sleep wins) to exercise branch-decision determinism
- hook-sleep
- Sticky comment with history — last N runs visible at a glance, scenario breakdown for the latest run
- --check mode in the renderer cleanly separates "render markdown" from "fail the CI step", so the same script powers both paths
Verified
- All non-repro CI jobs pass (109/2 failures, only
Benchmark Vercel (nitro-v3)flake and the expectedEvent Log Race Repro"failure") - The repro job runs ~24 min as expected for 2000 attempts at concurrency 50, plus the step-heavy scenarios
- Sticky comment renders the history table correctly across 4 runs
- The
--checkexit code logic correctly fails whennonCompleted > 0
Things to keep in mind (non-blockers)
Drift risk: This is 881+372+405 lines of test + fixture + renderer scaffolding that depends on SDK surfaces (
createHook,start,getHookByToken,resumeHook). If those APIs change, this harness needs updating. Worth a comment block at the top of the test file (or aREADMEnext to it) calling it out as "diagnostic-only, update when SDK race shapes change."Single-adapter coverage: Only runs against
example-nextjs-workflow-turbopack. The races being targeted are SDK-level (event log replay), not adapter-specific, and the world-vercel backend is shared across adapters — so this is probably fine. But if races emerge that are adapter-specific (e.g. specific to webpack bundling), this won't catch them. Worth keeping in mind.Workflow file numbering:
101_hook_sleep_repro.tsfollows the1_,2_, ...,100_convention. Good.Defensive env parsing:
envNumber/envBooleancorrectly fall back on invalid input. ✓
Sticky-comment design observations
The comment structure is well thought out:
<!-- event-log-race-repro-history JSON event-log-race-repro-history -->— hidden JSON for next run to read and append. Standard "sticky comment with state" pattern, clean.- Truncated to most recent N runs implicitly (the table doesn't grow unboundedly because old runs eventually scroll off in the markdown).
One micro-suggestion: if the history grows past 10-ish runs, the table could get unwieldy in the GitHub UI. Worth capping history.length in the renderer (history.slice(-10)) so old data ages out naturally. Not a blocker — easy to add later if it ever matters.
Bottom line
This is the right shape of tool for the problem (random races at 0.2% require a high-iteration harness to surface reliably). The label gating keeps it cheap by default. The sticky-comment history makes it actionable for tracking fixes over time.
Approving.
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Backport PR opened against |
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(AI)
Adds a label-gated CI job for reproducing event-log race conditions.
The new
event-log-race-reprolabel runs a single Next.js Turbopack preview deployment through repeated race attempts, writes a JSON artifact, and posts one sticky PR comment with a running history table. Each CI run is a column with timestamped links to the workflow logs and tested deployment, plus the outcome distribution for completed, USER_ERROR, CORRUPTED_EVENT_LOG, RUNTIME_ERROR, stuck, and other runs.The default run keeps 1500 hook/sleep workflow runs at concurrency 50, then adds 250 parallel-step fanout runs and 250 step/sleep race runs. The step-heavy scenarios are meant to catch concurrent replays acting on stale event logs around
step_created,step_completed,wait_completed, and branch decisions, not just hook/sleep interactions. The sticky comment also includes a per-scenario breakdown for the latest run.This should still catch at least one failure on average for the current main/stable baseline, where
CORRUPTED_EVENT_LOGis expected around 0.2% of runs.This draft is expected to fail on the current unfixed baseline when the label is present; the failure output is the point of the harness. The sticky comment on this PR is the source of truth for the current run history and observed distribution.