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Graph/contextvars-propagation-middleware-boundary

Pattern

Contextvars Lost Across Middleware

contextvars-propagation-middleware-boundary

A recurring concurrency-shaped bug where Starlette middleware (often BaseHTTPMiddleware or thread offloading) fails to propagate contextvars across async boundaries, leading to hung endpoints or missing logging context until custom middleware/executor patterns are used.

Node Details

Public graph metadata

Updated5/1/2026

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30 linked nodes

Zustand persist middleware does not write during the test setup

I'm building a Next.js 14 app that uses Zustand with the persist middleware to store authentication tokens and user info. Tension: authenticated pages redirect me to /error/unauthorized. Outcome: React has detected a change in the order of Hooks...

After adding the Zustand `persist` middleware to a store slice, specific store functions in `GlobalStoreSlice` (e.g., `setColor` and `todoColor`) appear to no longer exist, especially after browser reloads. Other state not wrapped by `persist` continues to work.

TanStack Start/Router does not accept provider placement that breaks SSR

TanStack Router remounted the entire component tree on route changes, causing the Tabs component to lose its tab-change animation when navigating between routes like /user/$userId/profile and /history.

Values from a custom React context are not available/updated inside TanStack Router `beforeLoad` for a route when the context changes.

"x-forwarded-host`header with value`foobar-3000.app.github.dev`does not match`origin`header with value`localhost:3000` from a forwarded Server Actions request. Aborting the action.". Tension: the problem is occurring elsewhere in the application. Outcome: Aborting the action.

[GET] [middleware: "middleware"] / status=401 — I deployed the site on vercel and it shows a status 401 on my middleware file. Tension: The message attempts show that it fails whenever I create a new user, update a user's name, or delete them. Outcome: you have to change your webhook public route from `/app/api/webhooks/clerk/route.ts` -> `/api/webhooks/clerk` or `/api/webhooks(.*)`.

Next.js middleware throws "Cannot read properties of undefined (reading 'custom')" when connecting to MongoDB

Sentry Logger [warn]: Discarded session because of missing or non-string release — Sentry.init({. Tension: but still keep getting.

the cache doesn't work across processes — workers might be pre-forked. Tension: is using lru caching doing what I am expecting, that is - will it only initialize sentry once even though i attempt to do it multiple times? Outcome: provided it's called within the same process.

Zone mismatch. — during runApp. Tension: The Flutter bindings were initialized in a different zone than is now being used. Outcome: This will likely cause confusion and bugs as any zone-specific configurat.

CrashLoopBackOff — one pod: sentry-ingest-replay-recordings-xxx-yyy is crash loop. Tension: Broker: Unknown topic or partition. Outcome: After last upgrade to chart sentry-18.0.0, app version 23.3.1.

Sentry reports frequent "Non-Error promise rejection captured with value: Object Not Found Matching Id" events in a MERN app, but the error details are sparse and can’t be reliably reproduced locally.

the context variables get propagated correctly to the uvicorn access logger — if I use a custom middleware class without inheriting from `BaseHTTPMiddleware`. Tension: known starlette `BaseHTTPMiddleware` limitation of not propagating contextvars "upwards".

none of customized request headers could be obtained in `UserIdValidationMiddleware` — If the order is reversed, then. Tension: It is not on the axios side. Outcome: Finally, this issue is fixed after reading CORSMiddleware not work and it is related to CORS.

Yes, it will be reset as soon as the current HTTP view is done. — in a FastAPI app, that is done by the framework + application server (asgi or uvicorn). Tension: what will happen to SqlAlchemy session that is set in ContextVar if not to reset it? Outcome: the co-routine `main` returns.

SessionMiddleware in a FastAPI backend fails to set the session cookie when the React frontend and backend are hosted on different domains/subdomains (e.g., XXX-ui.fly.dev vs XXX-api.fly.dev). The browser rejects the cookie with an 'invalid domain' error and no session is maintained.

WebSocket progress messages sent from a FastAPI backend during file processing are not received in the Next.js frontend until processing finishes, when all messages arrive at once. Backend logs show progress updates are generated successfully.

request.scope has no attribute "route" — in the middleware. Tension: I am unsure of what a scope really is and why it changes in the middleware, but how can i work around this ? Outcome: Consider using custom APIRoute instead.

the contextvars setted on the main thread does not propagate to "_monitor" thread of the QueueListener — parallelize logs with Queuehandler and Queuelistener in a fastapi application. Tension: And use in it in a Formatter on a logger file. Outcome: Can anyone help me to understand how can I resolve this?

Middleware registered on the main FastAPI app is also triggered for requests routed to a mounted sub-application, including subapi docs/openapi endpoints. This prevents isolating middleware behavior per sub-application.

ResourceInitializationError: failed to download env files — ECS service where tasks are consistently failing during deployment. Tension: request context canceled caused by: context deadline exceeded. Outcome: After creating a NAT Gateway and adding a new route to the existing routing table for the NAT Gateway, the issue was resolved.

Next.js middleware placed as middleware.ts is not being detected or executed: the matcher never matches and no console logs appear.

Clerk middleware auth() returns userId but orgId and orgRole are undefined

after implementing middleware I get this error every time I make a call — after implementing middleware. Tension: The project works without any issues. But after implementing middleware I get this error every time I make a call. Outcome: MAY I KNOW WHAT THE REAL ISSUE IS. HOW TO FIX THAT.

A combined middleware setup in Redux Toolkit causes `toastMiddleware` to effectively run twice, resulting in two toast messages being added for a single action, even though the logging only occurs once. This issue does not occur when the middleware are concatenated separately.

createListenerMiddleware does not fire when the async thunk finishes and extraReducers run

cause a deadlock and fail when attempted in production — only to cause a deadlock and fail when attempted in production (much larger table sizes). Tension: we had an expensive migration that ran fine locally, got committed, and ran succesfully on a sandbox environment. Outcome: we decided we'd revert the commit that introduced the migration, rewrite it, and attempt again.

Tension: Did he leave by himself? Has its session ended and the system kicked it out? Outcome: Create a new middleware for session activity tracking.

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