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feat(world-vercel): allow a custom dispatcher - #2235
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🦋 Changeset detectedLatest commit: 9949659 The changes in this PR will be included in the next version bump. This PR includes changesets to release 17 packages
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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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📊 Benchmark Results
workflow with no steps💻 Local Development
workflow with 1 step💻 Local Development
workflow with 10 sequential steps💻 Local Development
workflow with 25 sequential steps💻 Local Development
workflow with 50 sequential steps💻 Local Development
Promise.all with 10 concurrent steps💻 Local Development
Promise.all with 25 concurrent steps💻 Local Development
Promise.all with 50 concurrent steps💻 Local Development
Promise.race with 10 concurrent steps💻 Local Development
Promise.race with 25 concurrent steps💻 Local Development
Promise.race with 50 concurrent steps💻 Local Development
workflow with 10 sequential data payload steps (10KB)💻 Local Development
workflow with 25 sequential data payload steps (10KB)💻 Local Development
workflow with 50 sequential data payload steps (10KB)💻 Local Development
workflow with 10 concurrent data payload steps (10KB)💻 Local Development
workflow with 25 concurrent data payload steps (10KB)💻 Local Development
workflow with 50 concurrent data payload steps (10KB)💻 Local Development
Stream Benchmarks(includes TTFB metrics)workflow with stream💻 Local Development
stream pipeline with 5 transform steps (1MB)💻 Local Development
10 parallel streams (1MB each)💻 Local Development
fan-out fan-in 10 streams (1MB each)💻 Local Development
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:
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AndrewBarba
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June 3, 2026 19:29
karthikscale3
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Reviewed for correctness and regression risk — backward-compatible and safe to merge, defaults are unchanged and every request path threads config consistently. A few non-blocking notes inline.
| import { createVercelWorld } from '@workflow/world-vercel'; | ||
| import { setWorld } from '@workflow/core/runtime'; | ||
| setWorld(createVercelWorld({ dispatcher: new Agent({ connections: 16 }) })); |
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Injection timing caveat worth documenting here: at Vercel runtime createWorld() calls createVercelWorld() with no config, so setWorld(...) is the only injection path. If the runtime has already created/cached the world before this setWorld call runs, the custom dispatcher silently won't take effect. Worth a one-line note that setWorld must run before the world is first used (i.e. before the first workflow request).
| * dispatcher from a different undici version. Callers may pass any undici | ||
| * version's dispatcher, or any object implementing the dispatcher contract. | ||
| */ | ||
| dispatcher?: unknown; |
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unknown is the right call given undici's version-specific Dispatcher type (the doc comment explains it well). Just flagging the trade-off: callers get zero type safety, so a malformed/incompatible dispatcher fails only at runtime inside fetch/@vercel/queue rather than at compile time. Acceptable here, but worth keeping in mind for the error story.
| * shared default agent. | ||
| */ | ||
| export function getDispatcher(config?: APIConfig): unknown { | ||
| return config?.dispatcher ?? getDefaultDispatcher(); |
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Nullish coalescing means an explicit dispatcher: null (or undefined) falls back to the shared default — sensible and probably the desired behavior. Only note: a caller who passes a falsy-but-intentional value expecting it to be used would be surprised, but for a dispatcher that's the correct semantics. No change needed; documenting the intent.
karthikscale3
approved these changes
Jun 4, 2026
AndrewBarba
enabled auto-merge (squash)
June 4, 2026 01:15
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Backport PR opened against |
This was referenced Jun 4, 2026
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What
Adds a
dispatcheroption toAPIConfig(consumed bycreateVercelWorld) so callers can supply a custom undici dispatcher. It is threaded through every request path — HTTP API calls, refs, encryption key fetch, deployment resolution, and the@vercel/queueclient — and defaults to the shared undiciRetryAgent.Why
The Vercel world relies on Node's built-in fetch being undici-backed and pins a specific undici version. Both the HTTP and queue paths already issue requests via global
fetchwith an undicidispatcher, so exposing the dispatcher gives callers a single, uniform knob to bring their own undiciAgent/RetryAgent(e.g. to tune pooling/retries on newer Node runtimes) without us changing defaults.How
APIConfig.dispatcher?: unknown(mirrors@vercel/queue's owndispatcher?: unknown).getDispatcher(config?)now returns the caller's dispatcher when set, else the shared default agent (the previous singleton, renamed togetDefaultDispatcher).configthrough; default behavior is unchanged.Usage
At Vercel runtime
createWorld()callscreateVercelWorld()with no config, so injection is via the existingsetWorldescape hatch (documented in the README):Tests
http-client.test.tscoveringgetDispatcherdefault vs. override.No public API removed;
dispatcheris purely additive and defaults to current undici behavior.