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[core] Turbo: skip the unused run_started event-log preload - #2569
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Turbo backgrounds run_started purely as a write barrier and synthesizes the run locally (preloadedEvents is forced to []), so it never reads the event-log preload the World returns on run_started. It now passes a new advisory `skipEventPreload` on that create; world-vercel forwards it as a `skipPreload` frame-meta flag so the backend can skip the wasted list+resolve. Because the first step_started is chained on the run_started barrier, trimming the run_started request directly shortens the wait before the first durable step_started — i.e. time-to-second-step. The flag is honored only for run_started and ignored by Worlds that don't preload; the runtime always falls back to events.list if it ever needs the log, so it is fully backward compatible. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
🦋 Changeset detectedLatest commit: f7a2b22 The changes in this PR will be included in the next version bump. This PR includes changesets to release 20 packages
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📊 Benchmark Results
workflow with no steps💻 Local Development
▲ Production (Vercel)
workflow with 1 step💻 Local Development
▲ Production (Vercel)
workflow with 10 sequential steps💻 Local Development
▲ Production (Vercel)
workflow with 25 sequential steps💻 Local Development
▲ Production (Vercel)
workflow with 50 sequential steps💻 Local Development
▲ Production (Vercel)
Promise.all with 10 concurrent steps💻 Local Development
▲ Production (Vercel)
Promise.all with 25 concurrent steps💻 Local Development
▲ Production (Vercel)
Promise.all with 50 concurrent steps💻 Local Development
▲ Production (Vercel)
Promise.race with 10 concurrent steps💻 Local Development
▲ Production (Vercel)
Promise.race with 25 concurrent steps💻 Local Development
▲ Production (Vercel)
Promise.race with 50 concurrent steps💻 Local Development
▲ Production (Vercel)
workflow with 10 sequential data payload steps (10KB)💻 Local Development
▲ Production (Vercel)
workflow with 25 sequential data payload steps (10KB)💻 Local Development
▲ Production (Vercel)
workflow with 50 sequential data payload steps (10KB)💻 Local Development
▲ Production (Vercel)
workflow with 10 concurrent data payload steps (10KB)💻 Local Development
▲ Production (Vercel)
workflow with 25 concurrent data payload steps (10KB)💻 Local Development
▲ Production (Vercel)
workflow with 50 concurrent data payload steps (10KB)💻 Local Development
▲ Production (Vercel)
Stream Benchmarks(includes TTFB metrics)workflow with stream💻 Local Development
▲ Production (Vercel)
stream pipeline with 5 transform steps (1MB)💻 Local Development
▲ Production (Vercel)
10 parallel streams (1MB each)💻 Local Development
▲ Production (Vercel)
fan-out fan-in 10 streams (1MB each)💻 Local Development
▲ Production (Vercel)
SummaryFastest Framework by WorldWinner determined by most benchmark wins
Fastest World by FrameworkWinner determined by most benchmark wins
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🧪 E2E Test Results✅ All tests passed Summary
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✅ 📋 Other
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| '@workflow/world-vercel': patch | ||
| --- | ||
| Turbo mode now tells world-vercel to skip the run_started event-log preload it never reads, trimming the run_started request the first step start waits behind. |
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| Turbo mode now tells world-vercel to skip the run_started event-log preload it never reads, trimming the run_started request the first step start waits behind. | |
| Turbo mode now tells world-vercel to skip the run_started event-log preload it never reads, reducing request time. |
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June 22, 2026 21:06
pranaygp
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Reviewed the full diff and traced the data path end-to-end (runtime.ts → world/CreateEventParams → world-vercel/events.ts → events-v4.ts frame meta). This is a clean, well-scoped optimization and I don't see any correctness issues.
Key things I verified:
- The backgrounded
run_startedresult is genuinely never read under turbo —runReadyBarrieris typedPromise<unknown>and only everawaited as an ordering barrier, andpreloadedEventsis hard-forced to[]. SoskipEventPreloadonly suppresses already-dead server work; it doesn't change SDK behavior. - Redelivery (attempt > 1) is correctly excluded (
turborequiresattempt === 1), so it still consumes the preload — covered by the new redeliver test. - Fully additive/back-compat: the flag is only forwarded when truthy, only acted on for
run_started, and the runtime always falls back toevents.list. Old server ignores the meta key; new server + old SDK never sends it. - Ran the affected suites locally after building deps:
packages/core(1320 passed, incl. the newskip the run_started preloadtest) andpackages/world-vercel(165 passed, incl. both new events-v4 tests).
One optional, non-blocking naming nit left inline. LGTM.
| // barrier only and never reads the preloaded log, so tell the server to | ||
| // skip the list+resolve. The server only acts on it for run_started; | ||
| // older servers ignore it and simply preload as before. | ||
| ...(params?.skipEventPreload ? { skipPreload: true } : {}), |
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Optional / non-blocking: the concept is named skipEventPreload at the World boundary (CreateEventParams) but skipPreload on the wire (CreateEventV4Input + frame meta). The analogous inline-delta feature (sinceCursor) keeps a single name all the way through, so the divergence here is a bit surprising and slightly hurts greppability — someone searching skipPreload won't find the runtime/World side and vice-versa.
If the wire name skipPreload is fixed by the server contract, this is fine as-is (the comments document the mapping well). Just flagging in case unifying on one name is cheap.
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(AI) Good call — unified on skipPreload end-to-end in f7a2b22: renamed the World-boundary CreateEventParams.skipEventPreload → skipPreload (runtime call site + tests updated), so it now greps across the SDK, the v4 frame meta, and the backend CreateEventOptions.skipPreload, matching the sinceCursor single-name precedent.
- Rename the World-boundary param `skipEventPreload` -> `skipPreload` so the single name greps across the SDK, the v4 frame meta, and the backend option (matching the `sinceCursor` precedent). Per @pranaygp review. - Apply @VaguelySerious changeset wording suggestion. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
pranaygp
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Jun 22, 2026
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No backport to This change is an optimization to turbo mode, which does not exist on To override, re-run the Backport to stable workflow manually via |
This was referenced Jun 22, 2026
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Jun 23, 2026
…testing * origin/main: Trace /flow route initialization (#2592) Version Packages (beta) (#2591) feat(web): add trace step shortcut helper (#2582) [web-shared] reskin json viewer (no duplicates, better colours and navigation) (#2434) Send occurredAt with workflow events (#2580) docs: use actual eve logo and tidy OSS nav dropdown (#2586) Display occurredAt in trace details (#2581) fix(next): discover root entrypoints (#2564) [core] Turbo: skip the unused run_started event-log preload (#2569) fix(next): prewarm SWC plugin cache (#2538) [world-vercel] Use v3 stream endpoint (supports transparent reconnect on timeout) (#2424) [core] Retry stream reopen against the reconnect budget (#2334) Add Platformatic World to worlds-manifest.json (#1450) docs: derive section landing-page cards from the page tree + lint drift (#2567)
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Turbo backgrounds
run_startedpurely as a write barrier and synthesizes the run locally (preloadedEventsis forced to[]), so it never reads the event-log preloadworld-vercelreturns onrun_started. This adds a new advisoryskipEventPreloadonCreateEventParams; the turbo path sets it on therun_startedcreate, andworld-vercelforwards it as askipPreloadv4 frame-meta flag so the backend can skip the wasted list + resolve.Why it matters
The first
step_startedis chained on therun_startedbarrier (step-executor.ts—runReadyBarrier.then(() => create(step_started))), sorun_started's request duration sits directly in front of the first durablestep_started, andstep_completedis ordered after that. Trimming the preload shortensrun_started, which advances the firststep_startedand therefore time-to-second-step.Safety / compatibility
run_started; ignored by Worlds that don't preload.events.listif it ever needs the log (e.g. on turbo exit), so omitting the preload never deprives it of data.run_started, and consumes the preload — so it does not send the flag.