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[e2e] Expand Python conformance coverage - #3495

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[e2e] Expand Python conformance coverage#3495
fantix merged 1 commit into
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fantix/python-conformance-more

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@fantix

@fantix fantix commented Aug 12, 2026 •
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Summary

Expands the Python workbench from a protocol smoke test into a cross-language conformance target driven by the existing TypeScript e2e suite.

  • Ports 48 Python fixtures covering concurrency, sleeps, retries, errors, streams, hooks, child runs, metadata, and run attributes.
  • Adds language-aware fixture and capability gating while keeping the shared test driver and assertions as the source of truth.
  • Uses vercel-workflow directly, with the resolved vercel-py revision recorded in uv.lock.
  • Simplifies the ASGI entrypoint and relies on the Vercel Python framework integration without a legacy builds override or the umbrella vercel package.
  • Makes a small set of otherwise portable assertions language-neutral.

Why

Running the same driver against TypeScript and Python tests the actual cross-language contract: serialized inputs and outputs, durable event ordering, queue delivery, retries, hooks, streams, and CLI hydration. The conformance manifest also acts as a ratchet: once a Python fixture is enabled, removing it or regressing it fails the suite instead of silently skipping coverage.

Coverage

The enabled fixtures exercise:

  • positional arguments, parallel steps, races, durable sleeps, cancellation, and resilient start;
  • binary and structured streams, including writable handles forwarded to child runs;
  • retry policy and serialized error identity and cause chains across step and workflow boundaries;
  • hook metadata, repeated payloads, disposal, token reuse, conflicts, owner discovery, mutex, adoption, and forwarding patterns;
  • child workflow creation and result retrieval;
  • caught and uncaught unregistered-step failures;
  • workflow and step attributes, including persistence when a run fails.

Known limitations

Two enabled tests have explicit capability exemptions in e2e-conformance.json:

  • the final fire-and-forget attribute write does not begin before the Python workflow coroutine returns;
  • reserved-attribute validation rejects the input correctly, but its message does not name the opt-in escape hatch expected by the shared assertion.

Fixtures that require Python APIs or failure semantics not implemented yet remain outside the enabled fixture list.

Validation

  • Local Python conformance: 64 passed | 77 skipped (141)
  • Vercel Python conformance: 62 passed | 98 skipped (160)
  • pnpm build
  • uv lock --check
  • Preview deployment using only vercel-workflow

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fantix requested a review from a team as a code owner August 12, 2026 18:09
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⚠️ No Changeset found

Latest commit: 7881413

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

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

Project Deployment Actions Updated
example-nextjs-workflow-turbopack Ready Ready Preview, v0 Sep 1, 2026 3:12pm UTC
example-nextjs-workflow-webpack Ready Ready Preview, v0 Sep 1, 2026 3:12pm UTC
example-workflow Ready Ready Preview, v0 Sep 1, 2026 3:12pm UTC
workbench-astro-workflow Ready Ready Preview, v0 Sep 1, 2026 3:12pm UTC
workbench-express-workflow Ready Ready Preview, v0 Sep 1, 2026 3:12pm UTC
workbench-fastify-workflow Ready Ready Preview, v0 Sep 1, 2026 3:12pm UTC
workbench-hono-workflow Ready Ready Preview, v0 Sep 1, 2026 3:12pm UTC
workbench-nestjs-workflow Ready Ready Preview, v0 Sep 1, 2026 3:12pm UTC
workbench-nitro-workflow Ready Ready Preview, v0 Sep 1, 2026 3:12pm UTC
workbench-nuxt-workflow Ready Ready Preview, v0 Sep 1, 2026 3:12pm UTC
workbench-python-workflow Ready Ready Preview, v0 Sep 1, 2026 3:12pm UTC
workbench-sveltekit-workflow Ready Ready Preview, v0 Sep 1, 2026 3:12pm UTC
workbench-tanstack-start-workflow Ready Ready Preview, v0 Sep 1, 2026 3:12pm UTC
workbench-vite-workflow Ready Ready Preview, v0 Sep 1, 2026 3:12pm UTC
workflow-swc-playground Ready Ready Preview, v0 Sep 1, 2026 3:12pm UTC
workflow-tarballs Ready Ready Preview, v0 Sep 1, 2026 3:12pm UTC
workflow-web Ready Ready Preview, v0 Sep 1, 2026 3:12pm UTC
1 Skipped Deployment
Project Deployment Actions Updated
workflow-docs Skipped Skipped v0 Sep 1, 2026 3:12pm UTC

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🧪 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.

10 flaky tests
  • an sfo1 reader sees chunks of an IN-PROGRESS iad1 stream (nextjs-turbopack)
  • cancelRun via CLI - cancelling a running workflow (express)
  • cancelRun via CLI - cancelling a running workflow (hono)
  • FatalError fails immediately without retries (astro)
  • outputStreamInsideStepWorkflow - getWritable() called inside step functions (vite)
  • positive startIndex (skips first chunk) (vite)
  • promiseAllWorkflow (nitro)
  • sleepWinsRaceWorkflow (vite)
  • workflow throw of a non-Error value round-trips verbatim as cause (nitro)
  • workflow throw of a non-Error value round-trips verbatim as cause (tanstack-start)

🛠 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.

  • cold-start-warmup · suite warmup (tanstack-start) · at 15:12:49Z · abandoned wrun_01M1EREPCY6PXC0YWAYEJHYAEK
  • run-pickup-stall · hookCleanupTestWorkflow - hook token reuse after workflow completion (nextjs-webpack) · at 15:17:31Z · abandoned wrun_01M1ERQH9T1B99QVKH246FRZ61
  • run-pickup-stall · concurrent hook token conflict - two workflows cannot use the same hook token simultaneously (nextjs-webpack) · at 15:17:32Z · abandoned wrun_01M1ERQJGYJ9QETDS5BMXB39DE

E2E Test Summary

Summary
Passed Failed Skipped Total
✅ ▲ Vercel Production 3632 0 688 4320
✅ 💻 Local Development 3922 0 558 4480
✅ 📦 Local Production 3922 0 558 4480
✅ 🐘 Local Postgres 3922 0 558 4480
✅ 🪟 Windows 320 0 0 320
✅ 🌐 Cross-language Conformance 64 0 77 141
✅ vercel-http-transport 817 0 143 960
✅ vercel-multi-region 27 0 0 27
✅ vercel-ws-transport 553 0 87 640
Total 17179 0 2669 19848
Details by Category

✅ ▲ Vercel Production

App Passed Failed Skipped
✅ astro-node 132 0 28
✅ astro-quickjs 132 0 28
✅ example-node 132 0 28
✅ example-quickjs 132 0 28
✅ express-node 132 0 28
✅ express-quickjs 132 0 28
✅ fastify-node 132 0 28
✅ fastify-quickjs 132 0 28
✅ hono-node 132 0 28
✅ hono-quickjs 132 0 28
✅ nest-node 132 0 28
✅ nest-quickjs 132 0 28
✅ nextjs-turbopack-node 157 0 3
✅ nextjs-turbopack-quickjs 157 0 3
✅ nextjs-webpack-node 157 0 3
✅ nextjs-webpack-quickjs 157 0 3
✅ nitro-node 132 0 28
✅ nitro-quickjs 132 0 28
✅ nuxt-node 132 0 28
✅ nuxt-quickjs 132 0 28
✅ python-node 62 0 98
✅ sveltekit-node 151 0 9
✅ sveltekit-quickjs 151 0 9
✅ tanstack-start-node 132 0 28
✅ tanstack-start-quickjs 132 0 28
✅ vite-node 132 0 28
✅ vite-quickjs 132 0 28

✅ 💻 Local Development

App Passed Failed Skipped
✅ astro-stable-node 134 0 26
✅ astro-stable-quickjs 134 0 26
✅ express-stable-node 134 0 26
✅ express-stable-quickjs 134 0 26
✅ fastify-stable-node 134 0 26
✅ fastify-stable-quickjs 134 0 26
✅ hono-stable-node 134 0 26
✅ hono-stable-quickjs 134 0 26
✅ nest-stable-node 134 0 26
✅ nest-stable-quickjs 134 0 26
✅ nextjs-turbopack-canary-node 141 0 19
✅ nextjs-turbopack-canary-quickjs 141 0 19
✅ nextjs-turbopack-stable-node 160 0 0
✅ nextjs-turbopack-stable-quickjs 160 0 0
✅ nextjs-webpack-canary-node 141 0 19
✅ nextjs-webpack-canary-quickjs 141 0 19
✅ nextjs-webpack-stable-node 160 0 0
✅ nextjs-webpack-stable-quickjs 160 0 0
✅ nitro-stable-node 134 0 26
✅ nitro-stable-quickjs 134 0 26
✅ nuxt-stable-node 134 0 26
✅ nuxt-stable-quickjs 134 0 26
✅ sveltekit-stable-node 153 0 7
✅ sveltekit-stable-quickjs 153 0 7
✅ tanstack-start-node 134 0 26
✅ tanstack-start-quickjs 134 0 26
✅ vite-stable-node 134 0 26
✅ vite-stable-quickjs 134 0 26

✅ 📦 Local Production

App Passed Failed Skipped
✅ astro-stable-node 134 0 26
✅ astro-stable-quickjs 134 0 26
✅ express-stable-node 134 0 26
✅ express-stable-quickjs 134 0 26
✅ fastify-stable-node 134 0 26
✅ fastify-stable-quickjs 134 0 26
✅ hono-stable-node 134 0 26
✅ hono-stable-quickjs 134 0 26
✅ nest-stable-node 134 0 26
✅ nest-stable-quickjs 134 0 26
✅ nextjs-turbopack-canary-node 141 0 19
✅ nextjs-turbopack-canary-quickjs 141 0 19
✅ nextjs-turbopack-stable-node 160 0 0
✅ nextjs-turbopack-stable-quickjs 160 0 0
✅ nextjs-webpack-canary-node 141 0 19
✅ nextjs-webpack-canary-quickjs 141 0 19
✅ nextjs-webpack-stable-node 160 0 0
✅ nextjs-webpack-stable-quickjs 160 0 0
✅ nitro-stable-node 134 0 26
✅ nitro-stable-quickjs 134 0 26
✅ nuxt-stable-node 134 0 26
✅ nuxt-stable-quickjs 134 0 26
✅ sveltekit-stable-node 153 0 7
✅ sveltekit-stable-quickjs 153 0 7
✅ tanstack-start-node 134 0 26
✅ tanstack-start-quickjs 134 0 26
✅ vite-stable-node 134 0 26
✅ vite-stable-quickjs 134 0 26

✅ 🐘 Local Postgres

App Passed Failed Skipped
✅ astro-stable-node 134 0 26
✅ astro-stable-quickjs 134 0 26
✅ express-stable-node 134 0 26
✅ express-stable-quickjs 134 0 26
✅ fastify-stable-node 134 0 26
✅ fastify-stable-quickjs 134 0 26
✅ hono-stable-node 134 0 26
✅ hono-stable-quickjs 134 0 26
✅ nest-stable-node 134 0 26
✅ nest-stable-quickjs 134 0 26
✅ nextjs-turbopack-canary-node 141 0 19
✅ nextjs-turbopack-canary-quickjs 141 0 19
✅ nextjs-turbopack-stable-node 160 0 0
✅ nextjs-turbopack-stable-quickjs 160 0 0
✅ nextjs-webpack-canary-node 141 0 19
✅ nextjs-webpack-canary-quickjs 141 0 19
✅ nextjs-webpack-stable-node 160 0 0
✅ nextjs-webpack-stable-quickjs 160 0 0
✅ nitro-stable-node 134 0 26
✅ nitro-stable-quickjs 134 0 26
✅ nuxt-stable-node 134 0 26
✅ nuxt-stable-quickjs 134 0 26
✅ sveltekit-stable-node 153 0 7
✅ sveltekit-stable-quickjs 153 0 7
✅ tanstack-start-node 134 0 26
✅ tanstack-start-quickjs 134 0 26
✅ vite-stable-node 134 0 26
✅ vite-stable-quickjs 134 0 26

✅ 🪟 Windows

App Passed Failed Skipped
✅ nextjs-turbopack-node 160 0 0
✅ nextjs-turbopack-quickjs 160 0 0

✅ 🌐 Cross-language Conformance

App Passed Failed Skipped
✅ python 64 0 77

✅ vercel-http-transport

App Passed Failed Skipped
✅ example 132 0 28
✅ express 132 0 28
✅ hono 132 0 28
✅ nextjs-turbopack 157 0 3
✅ nitro 132 0 28
✅ vite 132 0 28

✅ vercel-multi-region

App Passed Failed Skipped
✅ nextjs-turbopack 27 0 0

✅ vercel-ws-transport

App Passed Failed Skipped
✅ example 132 0 28
✅ express 132 0 28
✅ nextjs-turbopack 157 0 3
✅ vite 132 0 28

📋 View full workflow run

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Sim World

Simulated world deterministic testing for races. Traces

🟠 world-sim scenario book — 1 fail of 41 total

fence=per-spec

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

Full trace: world-sim.txt

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fantix marked this pull request as draft August 12, 2026 18:10
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📊 Workflow Benchmarks

commit 7881413 · Tue, 01 Sep 2026 15:32:38 GMT · run logs

Backend: vercel · app: nextjs-turbopack

Metric Scenario Best (ms) P75 (ms) P90 (ms) P99 (ms) Samples
TTFS step 220 (+20%) 🔻 1370 🔴 (+29%) 🔻 1428 🔴 (+28%) 🔻 1768 🔴 (+24%) 🔻 30
TTFS stream 228 (+6.0%) 1296 🔴 (+19%) 🔻 1406 🔴 (+28%) 🔻 1471 🔴 (+26%) 🔻 30
TTFS hook + stream 1469 (+20%) 🔻 1565 🔴 (+17%) 🔻 1621 🔴 (+17%) 🔻 1798 🔴 (+15%) 🔻 30
Fan-out TTFS Promise.all(100 steps) 599 (±0%) 2023 (+27%) 🔻 2105 (+20%) 🔻 2486 (+32%) 🔻 10
Fan-out TTLS Promise.all(100 steps) 1862 (+12%) 3730 (+12%) 3805 (+7.2%) 8061 (+21%) 🔻 10
STSO 1020 steps (inline) 125 (+13%) 160 (+8.1%) 185 (+6.3%) 257 (-27%) 💚 1019
WO 1020 steps 160029 (+7.4%) 160029 (+7.4%) 160029 (+7.4%) 160029 (+7.4%) 1
CRTT first chunk (pooled) 98 (+1.0%) 133 (-11%) 172 (±0%) 285 (+11%) 28

Streams

Scenario CRTT 1st p75 p90 p99 CDV max iters
paced control (100/s, 60B) 119 (-18%) 154 (-14%) 344 (-12%) 566 (-24%) 137 (-29%) 10
size sweep (100/s, 160B-12KB) 108 (-16%) 154 (-17%) 219 (-35%) 382 (-19%) 158 (+3%) 10
replay gateway-gpt-5.4-nano-2000t (1x) 111 (-16%) 129 (-19%) 181 (-28%) 358 (-40%) 271 (-18%) 3
replay eve-gpt-5.6-sol-2000t (1x) 138 (-18%) 134 (-21%) 180 (-24%) 318 (-63%) 244 (-60%) 2
replay eve-gpt-5.6-sol-2000t (2x) 146 (+15%) 184 (-23%) 255 (-28%) 416 (-35%) 275 (-3%) 3
📈 STSO distribution vs main (inline / queue-hop histograms)

1020 steps (inline)

Cumulative STSO time: main 148790ms → this run 158789ms (Δ +9999ms, +7%)

100-150 ms  ████████████████┃███████  main 779  this 556  -223
150-200 ms  ██████░░░░░░┃             main 181  this 416  +235
200-250 ms  ┃                         main  31  this  35    +4
250-300 ms  ┃                         main  11  this   8    -3
300-350 ms  ┃                         main   6  this   2    -4
350-400 ms  ┃                         main   6  this   1    -5
400-450 ms  ┃                         main   1  this   1    +0
450-500 ms  ┃                         main   1  this   0    -1
500-550 ms  ┃                         main   1  this   0    -1
600-650 ms  ┃                         main   1  this   0    -1
650-700 ms  ┃                         main   1  this   0    -1
📈 CRTT drill-down vs main (RTT distributions & profiles) 
variant  RTT 1ms→5s+             avg         p50         p90         p99     n
control  ······▄█▁▁···    129 (-15%)   115 (-9%)  344 (-12%)  566 (-24%)  3000
sweep    ······▄█▁····  126.7 (-16%)   117 (-7%)  219 (-35%)  382 (-19%)  3000
gw 1x    ·····▁▆█▁····  115.6 (-16%)  106 (-12%)  181 (-28%)  358 (-40%)  5295
eve 1x   ·····▁▆█▁····  116.5 (-27%)  106 (-17%)  180 (-24%)  318 (-63%)  5186
eve 2x   ·····▁▂█▃····  154.7 (-18%)  138 (-16%)  255 (-28%)  416 (-35%)  7779

RTT over stream progress (avg per tenth of stream, bars scaled min→max):

control  ▄▄▄▃▁▂██▄▂  111–154ms
sweep    ██▄▂▂▃▂▁▄▄  109–157ms
gw 1x    █▃▅▅▆▃▁▃▂█  98–133ms
eve 1x   ▅▁▂▂▃▄▅█▄▁  101–141ms
eve 2x   ▁▁▂▂▁▂▄█▃▃  134–220ms

RTT by chunk size (avg per log size bin, ~160B → ~12KB serialized, bars scaled min→max):

sweep  ▆██▅▃▂▁  124–129ms

Delivery jitter over stream progress (avg positive CDV per tenth of stream, bars scaled min→max):

control  ▁▄▅▄▂█▄▄▂▅  27–46ms
sweep    ▁▅▅▁▅█▇▂▆▃  45–54ms
gw 1x    ▅▄▆▃▆▃▂▄▁█  29–39ms
eve 1x   █▃▄▂▇▆▇█▇▁  21–26ms
eve 2x   ▄▄▁▅▃▃▃▁▁█  23–29ms
ℹ️ Metric definitions & methodology

Streams: first-chunk RTT (the stream-open path, before any buffering/backpressure), CRTT percentiles, and worst delivery stall (CDV max). Cells are medians across iterations; per-run values in the artifacts. No 🔴/🟢 marks until targets attach.

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.

The collapsed CRTT drill-down: per-variant RTT histograms (fixed log bins, · = empty) and mean RTT/positive-CDV profile lines over stream progress and chunk size. Histograms, avgs, and profiles merge exactly across runs; p50–p99 are percentile-of-percentiles. Per-index rows live in the artifacts.

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) · CRTT: chunk round-trip time (per-chunk write → read latency, one clock domain: deployment → stream backend → same deployment) · CDV: chunk delay variation / delivery jitter (inter-arrival gap minus inter-write gap per seq-adjacent pair; skew-free; the row is each run's MAX positive value, so one stall moves it)

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 · paced control (100/s, 60B): the control: 300 tiny (~60B) deltas metronome-paced at 100/s — zero workload structure, so it reads the transport floor and flush cadence, and disambiguates transport-wide vs workload-specific when a replay row moves · size sweep (100/s, 160B-12KB): same pacing as the control with deltas padded in rotation across seven log-spaced sizes (~160B–12KB) — rotation decouples size from stream position, so it isolates whether chunk size causes latency · replay gateway-gpt-5.4-nano-2000t (1x): raw provider SSE cadence captured at the AI gateway boundary (gpt-5.4-nano, the most popular gateway model; per-token deltas p50 208B = the modal production chunk size), replayed exactly as measured — the typical customer's workload; its CDV is the typical customer's real delivery jitter · replay eve-gpt-5.6-sol-2000t (1x): a captured eve turn (gpt-5.6-sol, the most-used demanding eve model; ~2000 output tokens = production p50 turn length) replayed exactly as measured — eve's envelope protocol re-ships the cumulative message so sizes ramp 142B→13KB; the demanding outlier tenant's reality · replay eve-gpt-5.6-sol-2000t (2x): the same eve capture at 2x — the headroom/stress row; real fast-tier models emit the same chunk sizes at proportionally higher rate, so time compression is a faithful speed model · first chunk (pooled): every run's seq-0 RTT pooled across all stream scenarios — the first chunk precedes any workload differentiation, so pooling samples one shared stream-open path with exact percentiles

Replay cadences (semantic sha256) — eve-gpt-5.6-sol-2000t eaf22f5946e7c61f3c65c7006d550df180cfabd4e706254a09f22aec0cfb420d · gateway-gpt-5.4-nano-2000t 6f24ac518b6b83ff1d0e85a5fe78230db192716d66a7fc6b2fe022752001d041

🔴 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; CRTT inside the workflow (excludes the api.vercel.com read path).

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

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Review the following changes in direct dependencies. Learn more about Socket for GitHub.

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Updatedpypi/​uvicorn@​0.52.3 ⏵ 0.52.498 +1100100100100

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github-actions Bot commented Aug 27, 2026 •
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Framework Flow route Step reg. Framework output
hono 200.9 KiB (±0) 40.6 KiB (±0) 1.77 MiB (±0)
nextjs-turbopack 206.3 KiB (±0) 439 B (±0) 765.6 KiB (±0)
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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.

7881413 · run

@fantix

fantix commented Sep 1, 2026

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@vercel/workflow this PR is ready

@fantix fantix mentioned this pull request Sep 2, 2026
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No backport to stable for 144b6d7 (AI decision).

This is test-coverage expansion, not a stability fix: it ports 48 new Python fixtures, adds language-aware capability gating, and switches the Python workbench's dependency to track vercel-py's main branch. Almost all of it lands in workbench/python, which I verified does not exist on origin/stable (git ls-tree origin/stable -- workbench/python returns nothing), and the packages/core/e2e/e2e.test.ts edits only exist to make shared assertions language-neutral for that absent app. The commit message notes it also fixes specVersion 7 breaking the Python e2e lane, but that fix lives in the vercel-py revision bump for an app stable does not have, so there is nothing to repair there.

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

144b6d760188866958bbd32bc06f0b5ac5e80b85

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@alangenfeld alangenfeld alangenfeld approved these changes

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@fantix @alangenfeld