fix(rpc,openapi): prevent lazy router races under concurrent requests

[dinwwwh]

Problem

When multiple requests hit the server at the same time while a lazy router was still loading, the matchers (StandardRPCMatcher and StandardOpenAPIMatcher) could:

• Invoke the same lazy loader multiple times, once per concurrent request.
• Lose routes entirely when a lazy router contained another lazy router — the nested route could then 404 permanently, even for later requests.

Fix

Concurrent requests now share a single load per lazy router: each loader runs exactly once, requests arriving mid-load wait for it instead of reloading or missing the route, and nested lazy routers always resolve correctly. If a loader fails, the request rejects and the next request retries as before.

Tests

New tests in both matchers cover concurrent requests to lazy routers, lazy routers nested inside lazy routers (up to three levels), multiple lazy branches matched in parallel, and retry after loader failure. All of them fail on the previous implementation. Full server and openapi suites pass (808 tests).

[vercel]

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

Project	Deployment	Actions	Updated (UTC)
orpc	Ready	Preview, Comment	Jul 27, 2026 10:04am

[pkg-pr-new]

More templates

• @orpc/astro-playground
• @orpc/browser-extension-playground
• @orpc/bun-websocket-otel-playground
• @orpc/cloudflare-worker-playground
• @orpc/contract-first-playground
• @orpc/electron-playground
• @orpc/nest-playground
• @orpc/next-playground
• @orpc/nuxt-playground
• @orpc/solid-start-playground
• @orpc/svelte-kit-playground
• @orpc/tanstack-start-playground

@orpc/ai-sdk

npm i https://pkg.pr.new/@orpc/ai-sdk@1734

@orpc/arktype

npm i https://pkg.pr.new/@orpc/arktype@1734

@orpc/client

npm i https://pkg.pr.new/@orpc/client@1734

@orpc/contract

npm i https://pkg.pr.new/@orpc/contract@1734

@orpc/experimental-durable-iterator

npm i https://pkg.pr.new/@orpc/experimental-durable-iterator@1734

@orpc/hey-api

npm i https://pkg.pr.new/@orpc/hey-api@1734

@orpc/interop

npm i https://pkg.pr.new/@orpc/interop@1734

@orpc/json-schema

npm i https://pkg.pr.new/@orpc/json-schema@1734

@orpc/nest

npm i https://pkg.pr.new/@orpc/nest@1734

@orpc/openapi

npm i https://pkg.pr.new/@orpc/openapi@1734

@orpc/openapi-client

npm i https://pkg.pr.new/@orpc/openapi-client@1734

@orpc/otel

npm i https://pkg.pr.new/@orpc/otel@1734

@orpc/experimental-pino

npm i https://pkg.pr.new/@orpc/experimental-pino@1734

@orpc/experimental-publisher

npm i https://pkg.pr.new/@orpc/experimental-publisher@1734

@orpc/experimental-publisher-durable-object

npm i https://pkg.pr.new/@orpc/experimental-publisher-durable-object@1734

@orpc/experimental-ratelimit

npm i https://pkg.pr.new/@orpc/experimental-ratelimit@1734

@orpc/react

npm i https://pkg.pr.new/@orpc/react@1734

@orpc/react-query

npm i https://pkg.pr.new/@orpc/react-query@1734

@orpc/experimental-react-swr

npm i https://pkg.pr.new/@orpc/experimental-react-swr@1734

@orpc/server

npm i https://pkg.pr.new/@orpc/server@1734

@orpc/shared

npm i https://pkg.pr.new/@orpc/shared@1734

@orpc/solid-query

npm i https://pkg.pr.new/@orpc/solid-query@1734

@orpc/standard-server

npm i https://pkg.pr.new/@orpc/standard-server@1734

@orpc/standard-server-aws-lambda

npm i https://pkg.pr.new/@orpc/standard-server-aws-lambda@1734

@orpc/standard-server-fastify

npm i https://pkg.pr.new/@orpc/standard-server-fastify@1734

@orpc/standard-server-fetch

npm i https://pkg.pr.new/@orpc/standard-server-fetch@1734

@orpc/standard-server-node

npm i https://pkg.pr.new/@orpc/standard-server-node@1734

@orpc/standard-server-peer

npm i https://pkg.pr.new/@orpc/standard-server-peer@1734

@orpc/svelte-query

npm i https://pkg.pr.new/@orpc/svelte-query@1734

@orpc/tanstack-query

npm i https://pkg.pr.new/@orpc/tanstack-query@1734

@orpc/trpc

npm i https://pkg.pr.new/@orpc/trpc@1734

@orpc/valibot

npm i https://pkg.pr.new/@orpc/valibot@1734

@orpc/vue-colada

npm i https://pkg.pr.new/@orpc/vue-colada@1734

@orpc/vue-query

npm i https://pkg.pr.new/@orpc/vue-query@1734

@orpc/zod

npm i https://pkg.pr.new/@orpc/zod@1734

commit: d78d4b5

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!

[pullfrog]

✅ No new issues found.

Reviewed changes — fixes a race condition in lazy router resolution under concurrent requests by replacing the for...of + wholesale array reassignment with a one-at-a-time resolution + promise-memoization pattern.

• Replace for...of + array rebuild with while + find + await-one — resolves pending routers one at a time and re-scans after each, so nested lazy routers pushed during init() are picked up by the same request instead of being dropped.
• Memoize init via initPromise on the pending entry — concurrent requests share a single unlazy() + init() invocation via ??=; duplicate loader calls and double route registrations are eliminated.
• Splice in place after init completes — pending routers are removed from the array only after resolution, so arriving requests wait on the shared promise rather than missing the route.
• Clear initPromise on failure for retry — sets pendingRouter.initPromise = undefined in the .catch() handler, preserving the previous retry-on-next-request behavior.
• Add readonly to pendingRouters — prevents the old wholesale-reassignment pattern at the type level.
• Add 3 new concurrency + retry tests to each matcher — covers nested lazy + concurrent requests, multi-branch concurrent matching with 3 nesting levels, and retry after loader failure. All fail against the old implementation and pass with the fix.

  ^{｜ View workflow run ｜ Using DeepSeek Pro (free via Pullfrog for OSS) ｜ 𝕏}