[world-sim] Start Hook crash scenario book by alangenfeld · Pull Request #5013 · vercel/workflow

alangenfeld · 2026-10-22T17:43:16Z

Summary & Motivation

Follow-up to #2376. The atomic start Hook design was model-checked only for the server's storage logic. Nothing crash-tested the SDK runtime end to end: real start(), /flow deliveries, turbo, step retries, replay and user code, with the start() caller, a flow delivery or a writer dying mid-admission. This PR is based on #4996, so the diff contains only the sim work.

Store: keeps the start Hook contract in its cross-region shape, where the decision commits first and the run row commits after a checkpoint. It also adds force claims and Hook retention, and it passes @workflow/world's atomic start Hook conformance suite.
Faults: a scenario can kill a delivery or a script caller at any call point or checkpoint, lose a response, or drop or delay a queued message. A delivery that dies is redelivered as the next attempt with the same message.
Script clients: with startedBy: 'script', a scenario starts as many clients as it likes against one token, and every run the World created is replayed and checked.
Start Hook checks: six starthook.* rules read every run's log, the store's decisions, the script's start requests and the effects that step bodies recorded.
Coupling to @workflow/core: a delivery that dies shares a Node process with its redelivery, so the sim clears the dead run's entries from core's step single-flight registry (the globalSingleton named @workflow/core//stepSingleFlight, shape version 1; see forgetProcessMemory in packages/world-sim/src/drive.ts). Renaming that singleton or changing its shape makes start-hook-in-step-start-step-dies hang until its deadline, so update the sim alongside it.
Book: 23 start-hook-* scenarios kill or stall a client, a delivery or the store at each point between start()'s enqueue and the token's release. start-hook-lost-start-message covers the refused start's wake of a holder stuck pending: a duplicate inside a minute wakes nothing, and two past it re-publish one message between them.

Test Plan

Tests run: the world-sim vitest suite (108 tests, including the conformance suite's orphan cases) and the full scenario book (65 scenarios). Everything is green, and the book's output was byte-identical across two runs. The 42 existing scenarios are unchanged apart from the size of one serialized error.
Mutation-checked against the runtime build:
- Allowing turbo on a start Hook candidate's first delivery turns 16 scenarios red on starthook.no-loser-execution.
- Removing the ack of a refused queued copy turns 16 red on starthook.refusal-not-acked.
- Breaking the orphan bound or the force claim's reservation transfer turns the orphan and handoff scenarios red.

Adds the start({ hook }) wire contract: StartHookSchema on run_created, resilient run_started and the queued runInput; the atomicStartHook capability; the run.startHook echo; WorkflowStartError and START_HOOK_ADMISSION_REJECTED; and world-vercel's startHook frame meta, 409 start-hook-conflict / 400 start-hook-* error mapping, and the WORKFLOW_VERCEL_EXPERIMENTAL_START_HOOK opt-in. Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>

…es TBD Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>

Adds a shared atomic-start-hook conformance suite and implements it in world-local (reservation on the token claim file, run created under its lock, refusals recorded per candidate) and world-postgres (decision and run in one transaction, serialized per token with an advisory lock shared with createHook; migration 0028). Both let the owner's createHook adopt the reservation and move it with a force-claimed Hook. The run detail panel shows the start Hook token. Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>

start() publishes the candidate first and then decides it with run_created; the queued copy's run_started carries the same startHook, skips turbo, and acks a refusal (HookConflictError or START_HOOK_ADMISSION_REJECTED) without running code. Unconfirmed queue or admission throws WorkflowStartError. Stream arguments pipe only once the candidate is admitted. Cross-deployment starts check the target's probed capabilities (health checks now carry them, parsed tolerantly), keeping the no-probe-channel guard. run_started now forwards encryptionPublicKey. WorkflowStartError round-trips through the host, VM and QuickJS serdes; re-runs never forward a source run's start Hook. Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>

Replaces the idempotency callout promising native atomic start with the start({ hook }) API, a start-or-route-to-owner pattern, WorkflowStartError, the World contract, and WORKFLOW_VERCEL_EXPERIMENTAL_START_HOOK. Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>

…ntion Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>

Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>

…nsitions and re-adoption An adopted Hook's retention now extends the reservation itself, so disposing it and adopting again with a shorter one cannot shorten the promise. world-local also carried run.startHook through none of its field-by-field run rewrites, so a run_created retry after run_started found the run 'without this start Hook'. Both are now conformance cases. Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>

… reviver fixture Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>

A by-token lookup that lands on a start reservation its run has not adopted answers HookReservedError (425 hook-reserved on the wire), retryable and never a HookNotFoundError. startHook carries optional serialized metadata the adopting Hook inherits when it brings none. WorkflowStartError is documented and marked retryable. Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>

…n and carry start Hook metadata Lookups of an unadopted reservation of a live run throw HookReservedError, and not found once the run ends without adopting it. Adoption inherits the reservation's metadata unless the Hook brings its own. Postgres tracks adoption on the admission row (migration 0028), and its timezone test counts the new table. Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>

…retry rules hook.metadata is serialized like createHook metadata. Without an explicit experimental_minRetention a start Hook keeps its token for 24 hours from start() where the World supports Hook retention (0 opts out). Inside a workflow a refusal, permanent rejection or contract error is final for the start() step, while WorkflowStartError stays retryable. HookReservedError round-trips through every serde. Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>

…t retention Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>

…ugh an interrupted adoption A lookup between the adopting createHook's claim write and its hook_created publish answered not found, so callers retrying on HookReservedError gave up; it now stays HookReservedError while the owner runs. A retried adoption whose first attempt died before publishing now still inherits the reservation's metadata. The e2e routing test now actually passes metadata to start(). Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>

…s lost A lookup that finds the claim naming the adopting Hook but no entity now rebuilds the Hook from its published hook_created before answering HookReservedError, so a crash between the publish and the entity write does not leave the token reserved forever. Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>

Points world-vercel at the server branch alias and advertises atomicStartHook unconditionally, so the Vercel e2e lanes run the start({ hook }) tests against the server's admission. Reverted after pairing. Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>

…created lands Holds the direct run_created back so the queued copy's run_started admits the candidate through the resilient start against the real backend, then checks a duplicate is refused naming it, the late direct write replays the decision, and the log has one run_created. Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>

Pairing passed: the start({ hook }) e2e tests ran and passed on the node and quickjs Vercel lanes against the server preview. Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>

The conformance suite takes an injectable clock and an optional orphan stager: past the 24h bound a candidate with no run is refused with START_HOOK_ADMISSION_REJECTED through either copy (run_created now uses that code instead of the bare timestamp error), and a staged orphan stops holding its token. world-local stages the orphan its claim-then-write leaves, and a fault-injected crash between the two recovers; world-postgres shows a failure mid-transaction leaves no reservation. Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>

…lease plus margin A writer stalled past the 30s token lock lease could still write its run beside a contender that took the token, so a reservation whose run was never written now holds for START_HOOK_ORPHAN_GRACE_MS (twice the lock's stale timeout, from the same constant) before a contender may release it, and lookups answer HookReservedError meanwhile. Claims record reservedAt. The conformance suite takes a per-World orphan hold and checks the token is held just inside it and released just past it; the crash test covers a contender on both sides of the grace. Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>

…ause Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>

vercel · 2026-10-22T17:43:31Z

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

Project	Deployment	Actions	Updated
example-nextjs-workflow-turbopack	Ready	Preview, v0	Oct 22, 2026 6:26pm UTC
example-nextjs-workflow-webpack	Ready	Preview, v0	Oct 22, 2026 6:26pm UTC
example-workflow	Ready	Preview, v0	Oct 22, 2026 6:26pm UTC
workbench-astro-workflow	Ready	Preview, v0	Oct 22, 2026 6:26pm UTC
workbench-express-workflow	Ready	Preview, v0	Oct 22, 2026 6:26pm UTC
workbench-fastify-workflow	Ready	Preview, v0	Oct 22, 2026 6:26pm UTC
workbench-hono-workflow	Ready	Preview, v0	Oct 22, 2026 6:26pm UTC
workbench-nestjs-workflow	Ready	Preview, v0	Oct 22, 2026 6:26pm UTC
workbench-nitro-workflow	Ready	Preview, v0	Oct 22, 2026 6:26pm UTC
workbench-nuxt-workflow	Ready	Preview, v0	Oct 22, 2026 6:26pm UTC
workbench-python-workflow	Ready	Preview, v0	Oct 22, 2026 6:26pm UTC
workbench-sveltekit-workflow	Ready	Preview, v0	Oct 22, 2026 6:26pm UTC
workbench-tanstack-start-workflow	Ready	Preview, v0	Oct 22, 2026 6:26pm UTC
workbench-vite-workflow	Ready	Preview, v0	Oct 22, 2026 6:26pm UTC
workflow-swc-playground	Ready	Preview, v0	Oct 22, 2026 6:26pm UTC
workflow-tarballs	Ready	Preview, v0	Oct 22, 2026 6:26pm UTC
workflow-web	Ready	Preview, v0	Oct 22, 2026 6:26pm UTC

1 Skipped Deployment

Project	Deployment	Actions	Updated
workflow-docs	Skipped	v0	Oct 22, 2026 6:26pm UTC

github-actions · 2026-10-22T17:43:35Z

🧪 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.

a run can take over its own earlier hook (nextjs-webpack · local-dev / local / node / stable)
health check (CLI) - workflow health command reports healthy endpoints (nitro · local-dev / local / node / 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 18:27:54Z · abandoned wrun_01M5JDWSSVKD902KFX6V1AAJB9
cold-start-warmup · suite warmup (tanstack-start) · at 18:27:57Z · abandoned wrun_01M5JDWST1EC05DZHTB1K4AV8S
run-pickup-stall · ChainableService.processWithThis - static step methods using this to reference the class (nuxt) · at 18:29:31Z · abandoned wrun_01M5JDZRRDYJK31MS3MNED6TYF
run-pickup-stall · thisSerializationWorkflow - step function invoked with .call() and .apply() (nuxt) · at 18:29:31Z · abandoned wrun_01M5JDZRRZRDXRK0PSC6EHYJ4Y
run-pickup-stall · hookCleanupTestWorkflow - hook token reuse after workflow completion (nextjs-webpack) · at 18:35:59Z · abandoned wrun_01M5JEBKGKD2NNM1BVCMQR4BAY

E2E Test Summary

Summary

	Passed	Skipped	Total
✅ ▲ Vercel Production	3982	986	4968
✅ 💻 Local Development	4785	551	5336
✅ 📦 Local Production	4785	551	5336
✅ 🐘 Local Postgres	4785	551	5336
✅ 🪟 Windows	356	12	368
✅ 🌐 Cross-language Conformance	68	91	159
✅ dynamic-runs	0	0	0
✅ vercel-http-transport	897	207	1104
✅ vercel-multi-region	27	0	27
✅ vercel-ws-transport	607	129	736
Total	20292	3078	23370

Details by Category

✅ ▲ Vercel Production

App	Passed	Skipped
✅ astro-node	145	39
✅ astro-quickjs	145	39
✅ example-node	145	39
✅ example-quickjs	145	39
✅ express-node	145	39
✅ express-quickjs	145	39
✅ fastify-node	145	39
✅ fastify-quickjs	145	39
✅ hono-node	145	39
✅ hono-quickjs	145	39
✅ nest-node	145	39
✅ nest-quickjs	145	39
✅ nextjs-turbopack-node	172	12
✅ nextjs-turbopack-quickjs	172	12
✅ nextjs-webpack-node	172	12
✅ nextjs-webpack-quickjs	172	12
✅ nitro-node	145	39
✅ nitro-quickjs	145	39
✅ nuxt-node	145	39
✅ nuxt-quickjs	145	39
✅ python-node	66	118
✅ sveltekit-node	164	20
✅ sveltekit-quickjs	164	20
✅ tanstack-start-node	145	39
✅ tanstack-start-quickjs	145	39
✅ vite-node	145	39
✅ vite-quickjs	145	39

✅ 💻 Local Development

App	Passed	Skipped
✅ astro-stable-node	155	29
✅ astro-stable-quickjs	155	29
✅ express-stable-node	155	29
✅ express-stable-quickjs	155	29
✅ fastify-stable-node	155	29
✅ fastify-stable-quickjs	155	29
✅ hono-stable-node	155	29
✅ hono-stable-quickjs	155	29
✅ nest-stable-node	155	29
✅ nest-stable-quickjs	155	29
✅ nextjs-turbopack-canary-node	183	1
✅ nextjs-turbopack-canary-quickjs	183	1
✅ nextjs-turbopack-quickjs-snapshot	183	1
✅ nextjs-turbopack-stable-node	183	1
✅ nextjs-turbopack-stable-quickjs	183	1
✅ nextjs-webpack-canary-node	183	1
✅ nextjs-webpack-canary-quickjs	183	1
✅ nextjs-webpack-stable-node	183	1
✅ nextjs-webpack-stable-quickjs	183	1
✅ nitro-stable-node	155	29
✅ nitro-stable-quickjs	155	29
✅ nuxt-stable-node	155	29
✅ nuxt-stable-quickjs	155	29
✅ sveltekit-stable-node	174	10
✅ sveltekit-stable-quickjs	174	10
✅ tanstack-start-node	155	29
✅ tanstack-start-quickjs	155	29
✅ vite-stable-node	155	29
✅ vite-stable-quickjs	155	29

✅ 📦 Local Production

App	Passed	Skipped
✅ astro-stable-node	155	29
✅ astro-stable-quickjs	155	29
✅ express-stable-node	155	29
✅ express-stable-quickjs	155	29
✅ fastify-stable-node	155	29
✅ fastify-stable-quickjs	155	29
✅ hono-stable-node	155	29
✅ hono-stable-quickjs	155	29
✅ nest-stable-node	155	29
✅ nest-stable-quickjs	155	29
✅ nextjs-turbopack-canary-node	183	1
✅ nextjs-turbopack-canary-quickjs	183	1
✅ nextjs-turbopack-quickjs-snapshot	183	1
✅ nextjs-turbopack-stable-node	183	1
✅ nextjs-turbopack-stable-quickjs	183	1
✅ nextjs-webpack-canary-node	183	1
✅ nextjs-webpack-canary-quickjs	183	1
✅ nextjs-webpack-stable-node	183	1
✅ nextjs-webpack-stable-quickjs	183	1
✅ nitro-stable-node	155	29
✅ nitro-stable-quickjs	155	29
✅ nuxt-stable-node	155	29
✅ nuxt-stable-quickjs	155	29
✅ sveltekit-stable-node	174	10
✅ sveltekit-stable-quickjs	174	10
✅ tanstack-start-node	155	29
✅ tanstack-start-quickjs	155	29
✅ vite-stable-node	155	29
✅ vite-stable-quickjs	155	29

✅ 🐘 Local Postgres

App	Passed	Skipped
✅ astro-stable-node	155	29
✅ astro-stable-quickjs	155	29
✅ express-stable-node	155	29
✅ express-stable-quickjs	155	29
✅ fastify-stable-node	155	29
✅ fastify-stable-quickjs	155	29
✅ hono-stable-node	155	29
✅ hono-stable-quickjs	155	29
✅ nest-stable-node	155	29
✅ nest-stable-quickjs	155	29
✅ nextjs-turbopack-canary-node	183	1
✅ nextjs-turbopack-canary-quickjs	183	1
✅ nextjs-turbopack-quickjs-snapshot	183	1
✅ nextjs-turbopack-stable-node	183	1
✅ nextjs-turbopack-stable-quickjs	183	1
✅ nextjs-webpack-canary-node	183	1
✅ nextjs-webpack-canary-quickjs	183	1
✅ nextjs-webpack-stable-node	183	1
✅ nextjs-webpack-stable-quickjs	183	1
✅ nitro-stable-node	155	29
✅ nitro-stable-quickjs	155	29
✅ nuxt-stable-node	155	29
✅ nuxt-stable-quickjs	155	29
✅ sveltekit-stable-node	174	10
✅ sveltekit-stable-quickjs	174	10
✅ tanstack-start-node	155	29
✅ tanstack-start-quickjs	155	29
✅ vite-stable-node	155	29
✅ vite-stable-quickjs	155	29

✅ 🪟 Windows

App	Passed	Failed	Skipped
✅ nextjs-turbopack-node	178	0	6
✅ nextjs-turbopack-quickjs	178	0	6

✅ 🌐 Cross-language Conformance

App	Passed	Failed	Skipped
✅ python	68	0	91

✅ 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	39
✅ express	145	39
✅ hono	145	39
✅ nextjs-turbopack	172	12
✅ nitro	145	39
✅ vite	145	39

✅ vercel-multi-region

App	Passed	Failed	Skipped
✅ nextjs-turbopack	27	0	0

✅ vercel-ws-transport

App	Passed	Skipped
✅ example	145	39
✅ express	145	39
✅ nextjs-turbopack	172	12
✅ vite	145	39

📋 View full workflow run

changeset-bot · 2026-10-22T17:43:39Z

⚠️ No Changeset found

Latest commit: a691cab

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github-actions · 2026-10-22T17:44:17Z

Sim World

Simulated world deterministic testing for races. Traces

🟢 world-sim scenario book — 0 fail of 65 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
✅ `start-hook-queued-copy-first-admits`	completed	12	0ms	ok
✅ `start-hook-queued-copy-first-admits-fenced`	completed	12	0ms	ok
✅ `start-hook-queued-copy-first-refused`	completed	12	0ms	ok
✅ `start-hook-queued-copy-first-refused-fenced`	completed	12	0ms	ok
✅ `start-hook-start-dies-after-enqueue-retry-wins`	completed	12	0ms	ok
✅ `start-hook-start-dies-after-enqueue-queued-wins`	completed	12	0ms	ok
✅ `start-hook-lost-run-created-response`	completed	12	0ms	ok
✅ `start-hook-lost-start-message`	completed	6	1.0d	ok
✅ `start-hook-concurrent-candidates`	completed	12	0ms	ok
✅ `start-hook-refused-under-turbo`	completed	12	0ms	ok
✅ `start-hook-refused-redelivered`	completed	12	5.0s	ok
✅ `start-hook-refused-redelivered-fenced`	completed	12	5.0s	ok
✅ `start-hook-in-step-start-lost-response`	completed	8	1.0s	ok
✅ `start-hook-in-step-start-step-dies`	completed	7	5.0s	ok
✅ `start-hook-owner-dies-before-adopting`	completed	12	5.0s	ok
✅ `start-hook-owner-ends-unadopted`	completed	6	0ms	ok
✅ `start-hook-adoption-crash`	completed	12	5.0s	ok
✅ `start-hook-adoption-crash-before-commit`	completed	12	5.0s	ok
✅ `start-hook-force-claim-handoff`	completed	8	1.0d	ok
✅ `start-hook-force-claim-handoff-crash`	completed	8	1.0d	ok
✅ `start-hook-orphan-late`	completed	6	1.0d	ok
✅ `start-hook-orphan-in-flight`	completed	6	1.0d	ok
✅ `start-hook-retention`	completed	6	1.0d	ok

Full trace: world-sim.txt

A refused start({ hook }) looks up the run its HookConflictError names. If that run is still pending more than a minute after its creation (its first message most likely lost, so nothing would ever start it), it re-publishes the run's plain orchestrator message to the run's own deployment, namespace and spec version, under an idempotency key bucketed per minute so concurrent refusals coalesce. Best effort: the conflict is still thrown, and a holder that is not a run (an orphaned candidate) publishes nothing. Documents both states. Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>

…k the start Hook properties The store keeps the atomic start Hook contract in its cross-region shape (decision, then run, with a checkpoint between them), passes @workflow/world's conformance suite, and adds force claims and Hook retention. Faults kill a delivery or a script caller at any call point, lose a response, or stop a write between its halves. Scenarios can start their own clients, and every run is replayed and checked. Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>

Twenty-two scenarios kill or stall a client, a delivery, or the store at each point between start()'s enqueue and the token's release: queued copy first, start() dying after its enqueue, a lost run_created response, concurrent candidates, refused candidates under turbo and redelivery, in-step starts, adoption crashes, Eve's force-claim handoff, orphans, and retention. Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>

The holder is admitted and its message dropped. A duplicate refused inside a minute wakes nothing; two refused past it re-publish one message between them, the holder runs, and the token is free once its retention passes. Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>

Two attempts for one accepted candidate could both pass the post-checkpoint check before either created the run, so the run is now re-confirmed in the turn that creates it. A call held while its delivery died no longer resumes. The owner check reads a run's end in commit order rather than by timestamp, and a retryable World error no longer counts as a start's final answer. Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>

alangenfeld added 21 commits October 21, 2026 16:36

[world] Mark the start Hook force-claim and pre-adoption delivery rul…

9924e07

…es TBD Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>

[e2e] Cover start({ hook }) admission, routing to the owner, and rete…

6255698

…ntion Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>

[changeset] Add start({ hook }) changesets

a725bb6

Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>

[test] Fix the CLI startRun test types and add the WorkflowStartError…

ac15aca

… reviver fixture Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>

[docs] Document HookReservedError, start Hook metadata and the defaul…

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…t retention Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>

Revert "DO NOT MERGE: pair e2e with the workflow-server#1292 preview"

e253dc3

Pairing passed: the start({ hook }) e2e tests ran and passed on the node and quickjs Vercel lanes against the server preview. Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>

[world-postgres] Match the injected failure through drizzle's error c…

03e872a

…ause Signed-off-by: Alex Langenfeld <alex.langenfeld@vercel.com>

alangenfeld added 3 commits October 22, 2026 12:53

vercel Bot reviewed Oct 22, 2026

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Comment thread packages/world-sim/src/store.ts Resolved

Comment thread packages/world-sim/src/world.ts Resolved

Comment thread packages/world-sim/src/start-hook-invariants.ts Resolved

Comment thread packages/world-sim/src/scenario.ts Resolved

alangenfeld force-pushed the alangenfeld/2026-10-22-run-idempotency-sim-book branch from ccd00aa to 63a0514 Compare October 22, 2026 18:21

vercel Bot temporarily deployed to Preview – workflow-docs October 22, 2026 18:23 Inactive

alangenfeld force-pushed the alangenfeld/2026-10-21-run-idempotency-sdk-prototype branch from c59fc83 to cc849a0 Compare October 22, 2026 22:22

alangenfeld closed this Oct 22, 2026

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[world-sim] Start Hook crash scenario book - #5013

[world-sim] Start Hook crash scenario book#5013
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Summary & Motivation

Test Plan

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🧪 E2E Test Results

⚠️ Flaky E2E Tests (passed on retry)

🛠 Infra Events (absorbed by the harness)

E2E Test Summary

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Sim World

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