controller[kState].transformAlgorithm is not a function

[J4v4Scr1pt]

Summary

[TypeError: controller[kState].transformAlgorithm is not a function] {
digest: '267856594'
}

I know you want an reproduction on the issue, but this issue is very specific and as it seems not reproduceable locally. Otherwise I would love to provide one!

It seems that more people have this issue and have a hard time tracking down the cause of it. You can read a fairly new thread here. It also seems that this have been there for a while because #68319 thread opened last summer with the same issue. There are more threads about this on StackOverflow etc.

We run an NextJs application (all latest and greatest) in standalone mode in an K8S environment as state above. From time to time this error just shows up. Tried different node versions and going through the code base several times but nothing seems out of order.

I'm unsure how affected our customers are because I don't know when this error fires off, but it's very annoying to see this popping up and a bit scary to not understand if it affects customers.

Help solving this would very much be appreciated.

Operating System:
 Linux
Binaries:
  Node: 22.12.0
  npm: 10.9.0
  Yarn: N/A
  pnpm: 9.15.1
Relevant Packages:
  next: 15.1.7 // Latest available version is detected (15.1.7).
  eslint-config-next: 15.1.7
  react: 19.0.0
  react-dom: 19.0.0
  typescript: 5.7.3
Next.js Config:
  output: standalone
Hosting Environment:
  Kubernetes,
  Docker Container node:22-alpine

Additional information

No response

Example

No response

[J4v4Scr1pt]

We have a lot of logs on this in DataDog, is there really no one that has an idea on where to start looking in to this?
I can't reproduce this locally and there no indicator when it happen. I would really really appreciate help on this because this issue affects many of our customers it seems from reading the logs.

[stefanraath3]

Hey, Im also experiencing this issue. it's super weird because in other branches of my projects it doesn't show up.
⨯ [TypeError: controller[kState].transformAlgorithm is not a function] { digest: '1014485352' }

Operating System: macOS Binaries: Node: 20.18.0 (Current system) npm: 10.8.2 (Current system) pnpm: 9.12.2 (Current system) Relevant Packages: next: 15.1.4 react: 19.0.0 react-dom: 19.0.0 typescript: 5.7.3 Next.js Config: images: Configured for Clerk Hosting Environment: Vercel

[J4v4Scr1pt]

Yes suuper weird, I understand it has something to do with streaming from Node.
Have tried to reproduce this in many ways but nothing. Very very hard to pin point where and when it happens.
It would be great to have some logging that gave some more context.

[stefanraath3]

I think I managed to find a way to reproduce it. this is specific to my situation where I accidentally used a "#" as a placeholder for a prop that should be a url. This was a very narrow situation that I found with the Avatar component from shadcn. First nav-user.tsx in my sidebar, then Avatar inside that. so idk how well it generalizes to other scenarios and how node streaming works. perhaps the combo of server component doing async + client component + something. maybe there is something in here that could give you some ideas on how to replicate it for your case.

I asked chatgpt to write something up:

Below is the scenario that clearly shows how a simple “function call + avatar prop set to "#"” combination can trigger the cryptic streaming error.

---

Minimal Example

Folder Structure

app/
  test/
    layout.tsx    <-- Our test layout
    page.tsx
  components/ui/
    avatar.tsx    <-- Shadcn Avatar component

app/test/layout.tsx

Scenario A (Error does occur)

"use server";

import { Avatar, AvatarFallback, AvatarImage } from "@/components/ui/avatar";

// Mock server function that simulates an async fetch.
async function mockFetchUserRole() {
  // Delay to mimic a real DB/API call
  await new Promise((resolve) => setTimeout(resolve, 500));
  return "admin";
}

export default async function TestLayout({
  children,
}: {
  children: React.ReactNode;
}) {
  // Trigger the async call. We get some data or role from the server side.
  const userRole = await mockFetchUserRole();

  // The culprit: using src="#"
  const avatarUser = {
    name: "User",
    email: "user@example.com",
    avatar: "#",
    role: userRole, // This is used or displayed
  };

  return (
    <div className="flex min-h-screen items-center justify-center">
      <Avatar className="h-8 w-8 rounded-lg">
        <AvatarImage src={avatarUser.avatar} alt={avatarUser.name} />
        <AvatarFallback className="rounded-lg">CN</AvatarFallback>
      </Avatar>
      {children}
    </div>
  );
}

With this code, once you navigate to the /test route or cause a partial reload, the server logs may start showing:

[TypeError: controller[kState].transformAlgorithm is not a function]
{ digest: 'XXXXXXXXXX' }

sometimes repeatedly on further interactions.

---

Scenario B (Error does NOT occur)

"use server";

import { Avatar, AvatarFallback, AvatarImage } from "@/components/ui/avatar";

// Notice: no mockFetchUserRole() call
export default async function TestLayout({
  children,
}: {
  children: React.ReactNode;
}) {
  // Hard-code a string instead of calling an async function
  const userRole = "admin";

  const avatarUser = {
    name: "User",
    email: "user@example.com",
    avatar: "#",
    role: userRole,
  };

  return (
    <div className="flex min-h-screen items-center justify-center">
      <Avatar className="h-8 w-8 rounded-lg">
        <AvatarImage src={avatarUser.avatar} alt={avatarUser.name} />
        <AvatarFallback className="rounded-lg">CN</AvatarFallback>
      </Avatar>
      {children}
    </div>
  );
}

In this variant, with no asynchronous function call, the error never shows up—even though <AvatarImage src="#" /> is still present.

---

How to Reproduce

1. Create a Next.js app (13+ or 15+), enable server components by default.
2. In app/test/layout.tsx, copy the “Scenario A” code snippet that:
   • Imports a shadcn/radix <Avatar> from a client component
   • Calls an async server function (like a mock DB or fetch) to get a variable
   • Passes "#" as the avatar source
3. Run npm run dev (or a production build on Node 20+).
4. Navigate to /test:
   • If the environment triggers partial streaming, you’ll begin seeing:

     [TypeError: controller[kState].transformAlgorithm is not a function]
     { digest: '...' }
     

     in terminal logs.

If you remove that async function call in the layout or if you remove/replace "#" with a real URL or empty string, the error disappears.

---

Key Takeaways

1. The combination of a server component layout that does an async fetch plus an <AvatarImage src="#" /> in a client component triggers Next.js’s streaming pipeline to produce [TypeError: controller[kState].transformAlgorithm is not a function].
2. Using "#" in <img> or <AvatarImage> is unusual, but apparently it completely breaks SSR streaming in some circumstances.
3. Removing any of these elements solves it:
   • No async server call (no partial stream).
   • Replacing "#" with a real or empty URL.
   • Putting <AvatarImage> behind a conditional that never actually renders it.
4. This strongly suggests that Next’s streaming/hydration logic or Node’s transform has trouble with a hash-only image source specifically when server data must be fetched and rendered.

From this minimal test, we see that seemingly innocuous placeholders like "#" can blow up Next’s SSR streaming if combined with server-side data fetching.

[J4v4Scr1pt]

Thank you so much for the detailed answer! 🙌

I don't use shadcn but HeroUI. Will look into the Avtar usage.

It's a tricky error and will probably be different for most. But answers like yours could help others. Thanks again!

[khashayarsw]

"I'm experiencing the same issue: TypeError: controller[kState].transformAlgorithm is not a function in my Next.js project. Any updates or solutions?"

[J4v4Scr1pt]

No updates and their will probably never be a silverbullet for this error. Maybe.. maybe Vercel could do something in the future with the logging to easier find why. But this error will probably rarely be the same for users.
But having a thread like this could help others. I will also write my findings if I ever pinpoint it

[roberttriggs]

I had this issue intermittently on my self hosted NextJS 15 app which uses Nginx as a reverse proxy. In my case the issue seems to be around headers / buffers growing to the point where they were getting truncated by Nginx which caused Node to have problems and throw the Kstate error. At the same time could see buffer overrun errors in Nginx "upstream sent too big header whil e reading response header" so I added the following into my server block in the Nginx conf to increase the proxy buffers:

proxy_buffer_size 128k;  # Increase the buffer size
proxy_buffers 4 256k;     # Increase the number of buffers and their size
proxy_busy_buffers_size 256k;  # Increase the buffer size when the server is busy
proxy_max_temp_file_size 256k; # Allow larger temp files in case of large headers

After adding this the issue is totally fixed for me (so far!)

[J4v4Scr1pt]

We also use the Nginx and I also get the heders ovwerflow error from time to time. Great suggestions, will look into this asap!

[hi10drasingh]

I've set proxy_buffering off; in the Nginx configuration, but I'm still encountering these errors.

[J4v4Scr1pt]

We have tested this and it did not solve the issue for us unfortunately. But thanks for the suggestion! 🙌

[fahimrayhan]

In my case, the error is produced from these two legacy image parameters. If I remove these parameters, then the error is gone.

[khashayarsw]

I suspect that using deprecated Image APIs might be causing the TypeError: controller[kState].transformAlgorithm is not a function error. However, I am not using any deprecated APIs in my code. I have also moved image rendering to the client side only, but I am still encountering this error in the server logs.

[alioftech]

We are having the same issue. Really hard to debug

[alioftech]

Switching from webpack to turbo solved the issue for us.

[mjulstein]

@alioftech Did you switch to building the app in turbo? Is this now officially supported?
I can't find a way to do so.

[alioftech]

@alioftech Did you switch to building the app in turbo? Is this now officially supported?

I can't find a way to do so.

The issue was happening only in dev for us. We are still using webpack and docker for builds

[dominictobias-bullish]

By the way in the unlikely event this helps anyone else - some previously fragile but ok redirect() code (therefore I didn't discover it as the culprit at first) in a component started to infinitely redirect after some changes.

[theklinks22]

Posting this here to potentially help others. I was seeing this very frequently and I noticed my app was being scraped relentlessly by AI bots. Seemed to be happening if someone asked ChatGPT or other service and the prompt was terminated prematurely. I'm not entirely sure this is 100% the culprit but haven't seen this error since on my app since updating my robots.txt.

[gruckion]

What’s in your robots.txt?

[HasanMothaffar]

I don't have a robots.txt and I'm getting the error in my local dev console using Next.js 15.5.4 (turbopack)

[c0b41]

issue seems like gone after next 15.3.0 update, and looks like this error or warning was coming thru react code

[AlexMarcoDAngelo]

issue seems like gone after next 15.3.0 update, and looks like this error or warning was coming thru react code

Nope - I am on 15.3.2 and still getting it :(

[prabhunimish]

In our case we noticed that in one of our middleware checks, for a certain condition we were supposed to perform NextResponse.next({ request: { headers: updatedHeaders } }) and instead we missed out to wrap headers inside request object and passed NextResponse.next({headers: updatedHeaders }) We fixed this and the issue was resolved.

[gruckion]

Interesting, will take a look into this

[FarhanHossain00]

Thank you soooooooo much. I made the exact same mistake and this tweak fixed my issue.

[BarrySong97]

I got the same promblem. My project has been running normally last week. But this week this issue just poped up. it's werid.

[AleksandrKarashev]

same problem
"next": "15.2.1"

[AleksandrKarashev]

15.3.3 also happening

[gruckion]

Interesting, I am getting this locally. I did some debugging. It is inconsistent for me too.

It happened a few times. But then stopped. I rebooted the server and it still happened. Tried on incognito too.

> I am seeing this error in the terminal <> GET
/api/trpc/quote.myQuotesList?batch=1&input=%7B%220%22%3A%7B%22json%22%3A%7
B%22searchFilters%22%3A%7B%22columnFilters%22%3A%5B%5D%2C%22globalFilter%2
2%3A%22%22%7D%2C%22direction%22%3A%22forward%22%7D%7D%7D 200 in 299ms
info - [TRPC] businessTarget.get took 1572ms to execute { path:
'businessTarget.get', duration: 1572, slow: true }
info - [TRPC] quote.myQuotesList took 164ms to execute { path:
'quote.myQuotesList', duration: 164, slow: false }
info - [TRPC] siteMeter.findCompanySiteMeters took 198ms to execute {
path: 'siteMeter.findCompanySiteMeters', duration: 198, slow: false }
info - [TRPC] quote.myQuotesList took 216ms to execute { path:
'quote.myQuotesList', duration: 216, slow: false }
info - [TRPC] quote.myQuotesList took 267ms to execute { path:
'quote.myQuotesList', duration: 267, slow: false }
✓ Compiled middleware in 66ms
✓ Compiled in 138ms
✓ Compiled /_not-found/page in 29ms
[TypeError: controller[kState].transformAlgorithm is not a function]
⨯ unhandledRejection: [TypeError: controller[kState].transformAlgorithm
is not a function]
⨯ unhandledRejection:  [TypeError: controller[kState].transformAlgorithm
is not a function]
✓ Compiled middleware in 29ms
✓ Compiled in 13ms
✓ Compiled in 277ms
GET /account/quotes 200 in 1032ms
✓ Compiled /_not-found/page in 122ms
[TypeError: controller[kState].transformAlgorithm is not a function]
⨯ unhandledRejection: [TypeError: controller[kState].transformAlgorithm
is not a function]
⨯ unhandledRejection:  [TypeError: controller[kState].transformAlgorithm
is not a function]</> Please research it online and report back to me. Do
not edit my files. spcifically this part <>[TypeError:
controller[kState].transformAlgorithm is not a function]
⨯ unhandledRejection: [TypeError: controller[kState].transformAlgorithm
is not a function]
⨯ unhandledRejection:  [TypeError: controller[kState].transformAlgorithm
is not a function]</>
> 

⏺ I'll research this error for you. The error TypeError:
controller[kState].transformAlgorithm is not a function appears to be
related to Node.js streams or fetch API issues.

⏺ Web Search("TypeError controller[kState].transformAlgorithm is not a …
function Node.js Next.js")
⎿  Did 1 search in 39s

⏺ Web Search(""controller[kState].transformAlgorithm" Next.js 14 15 …
streaming error fix solution")
⎿  Did 1 search in 30s

⏺ Based on my research, here's what I found about the error TypeError:
controller[kState].transformAlgorithm is not a function:

Summary

This is a known Next.js streaming error that occurs intermittently,
particularly in production environments. It's related to Next.js's
streaming/transform mechanisms and is notoriously difficult to reproduce
locally.

Common Causes

1. Invalid Image Sources: Using # as src in <img> or avatar components
breaks SSR streaming
2. Node.js Version: Particularly affects Node.js v22 (downgrading to v18
often fixes it)
3. Async Operations: Combination of async server components with certain
client components
4. Nginx/Proxy Issues: Headers/buffers getting truncated in self-hosted
setups

Solutions

1. Check Image Sources: Replace any src="#" with real URLs or empty
strings
2. Switch to Turbopack: Some developers report switching from webpack to
turbo resolves it
3. Node.js Downgrade: Set Node.js to version 18 instead of 22
4. Review Async Patterns: Check async operations in layout components

Current Status

This is an ongoing issue with Next.js 14/15. The error appears related to
streaming responses via the app router, and Vercel is aware but hasn't
provided a definitive fix yet.

Since you mentioned the redis cache file was opened, it's possible the
error is related to async operations in that context interfering with
Next.js streaming.

In my codebase, If I run the app `pnpm turbo dev` and I do not open the     │
│   app in the browser we see <>                                                │
│   > @watt/crm@0.1.2 dev /Users/sigex/workdir/watt-copy-2/apps/crm             │
│   > next dev --turbopack                                                      │
│                                                                               │
│   ✔ Console Ninja extension is connected to Next.js, see                      │
│   https://tinyurl.com/2vt8jxzw                                                │
│      ▲ Next.js 15.1.1-canary.16 (Turbopack)                                   │
│      - Local:        [http://localhost:3000/](http://localhost:3000/)                                    │
│      - Network:      [http://192.168.1.124:3000/](http://192.168.1.124:3000/)                                │
│      - Experiments (use with caution):                                        │
│        · ppr                                                                  │
│        · externalDir                                                          │
│        · authInterrupts                                                       │
│        · ...                                                                  │
│                                                                               │
│    ✓ Starting...                                                              │
│    ✓ Compiled in 642ms                                                        │
│    ✓ Ready in 1416ms                                                          │
│                                                                               │
│   </>. If I then wait 60 seconds for inngest and novu to start up we then     │
│   see; <>[Pasted text #1 +40 lines]</>. Currently no issues at all. Next I    │
│   will load up the app https://localhost:3000/ in a new incognito browser. I  │
│   then get <> ○ Compiling /authentication/login ...                           │
│    ✓ Compiled /authentication/login in 3.1s                                   │
│    GET /authentication/login 200 in 3501ms                                    │
│    GET /authentication/login 200 in 160ms</>. Now I will login I get          │
│   <>[Pasted text #2 +26 lines]</>. Doing this I didn't see that error once.   │
│   Now I will refresh the page in the brower and I get <>[Pasted text #3 +23   │
│   lines]</>. Next I will run the app again and try to refresh the login page  │
│   route to see if that cuases it too. I did that and refresh twice no         │
│   error. <>> next dev --turbopack                                             │
│                                                                               │
│   ✔ Console Ninja extension is connected to Next.js, see                      │
│   https://tinyurl.com/2vt8jxzw                                                │
│      ▲ Next.js 15.1.1-canary.16 (Turbopack)                                   │
│      - Local:        [http://localhost:3000/](http://localhost:3000/)                                    │
│      - Network:      [http://192.168.1.124:3000/](http://192.168.1.124:3000/)                                │
│      - Experiments (use with caution):                                        │
│        · ppr                                                                  │
│        · externalDir                                                          │
│        · authInterrupts                                                       │
│        · ...                                                                  │
│                                                                               │
│    ✓ Starting...                                                              │
│    ✓ Compiled in 555ms                                                        │
│    ✓ Ready in 1385ms                                                          │
│    ○ Compiling /authentication/login ...                                      │
│    ✓ Compiled /authentication/login in 3.9s                                   │
│    GET /authentication/login 200 in 4276ms                                    │
│    GET /authentication/login 200 in 88ms                                      │
│    GET /authentication/login 200 in 82ms                                      │
│   </>. Next I will again login, and then navigate to a different page.        │
│   http://localhost:3000/account/users from this I dont see that error. Now I  │
│   will try to rleoad the /users page.

I have next.js github repo checked out locally I searched for transformAlgorithm and got 38 results across 8 files. I was 422 commits behind, grabbed those and still the same results.

[santosguilherme]

Same here:

Node.js: v22.18.0
Next.js: 15.5.4
Output: Standalone
Infra: EKS + CloudFront

It started happening after updating to Next.js 15.5.4

[wishket-pjw]

I encountered the same issue and managed to resolve it with the help of Codex. The solution seems effective. Here's what worked for me:

Root Cause

The error occurs due to a conflict between native Web Streams API and web-streams-polyfill. The issue stems from:

openai@4.x → formdata-node → web-streams-polyfill@4.0.0-beta.3

Solution

1. Upgrade OpenAI package:

   npm install openai@^5.0.0

2. Set Node.js runtime explicitly:

   // In your API route
   export const runtime = 'nodejs'

Why this works:

• OpenAI v5 eliminates the formdata-node dependency
• Removes web-streams-polyfill entirely from the dependency tree
• Node.js runtime ensures consistent stream handling

Verification:

After the changes, you can verify the polyfill is gone:

find node_modules -name "web-streams-polyfill"
# Should return nothing

The ReadableStream → TransformStream pipeline should now work without issues.

[Lambdac0re]

None of the listed packages are installed in my project and the crash still occurs.

[santosguilherme]

@Lambdac0re have you tried only changing the runtime to Node.js?

[wishket-pjw]

Do you use Suspense by any chance? It could be caused by nested async server components inside Suspense. It's a transform algorithm configuration failure in Next.js's streaming rendering mechanism. I'm not sure though, since it's not my case.

[anjan-kp]

Can the NextJS team address this issue? The streaming implementation is useless now. I had to revert my streaming code when it started throwing this error every second and crashing my server on production. The interesting thing is that it happens only on production, and I don't have any option to debug and fix. Now I am scared of upgrading my application to V16.
App/Infra details
nodejs : 22.20.0
next : 15.3.3
react : 19.1.0
Infra : AWS EKS, Kong, Cloudfront

[LucasMRC]

Oh, man! Tell me how did you fix this, I'm experiencing the same thing :sad:

[HupBaHa]

@LucasMRC If you're on EKS, then the solution is below.
#75995 (comment)

[sombek]

If i build the project locally and then run
node .next/standalone/server.js
i get the error
but if i run it like
pnpm start

  "scripts": {
    "dev": "next dev",
    "build": "next build",
    "start": "next start",
    "lint": "next lint"
  },

I don't get the error

[HupBaHa]

For those experiencing the issue on EKS.

This is not a NextJS team problem.
I experienced this error on Next.js 15.4.6 and 16.x on EKS and found the root cause:
Health check requests a streaming page (e.g., /):
Health checker immediately closes connection (bc doesn't need the body)
Stream gets corrupted mid-flight -> controller[kState].transformAlgorithm is not a function

Solution here:

  export async function GET() {
    return Response.json(
      { status: 'ok' },
      {
        status: 200,
        headers: {
          'Content-Type': 'application/json'
        }
      }
    );
  }
  export const dynamic = 'force-static';

Point your health checks to -> /healthcheck

Enjoy the silence in the logs ;)

[Umuts-Codes]

This is the recommended approach to handle the controller[kState].transformAlgorithm error

The error

TypeError: controller[kState].transformAlgorithm is not a function

occurs in specific environments, particularly when running Next.js 15.1.7 with Node 22 in Docker or Kubernetes. It is not consistently reproducible locally and appears to be related to changes in Node internals and Web Crypto API behavior.

Steps to address the issue

1. Test with different Node versions
   Try Node 20 or Node 18 to see if the error persists. Some functions may behave differently in Node 22.

2. Check standalone build
   Standalone output mode may not include all necessary polyfills for certain internal APIs. Test your application in development or standard build mode to compare behavior.

3. Defensive coding
   Use optional chaining or try/catch to prevent runtime crashes when the method is undefined:

const algo = controller[kState]?.transformAlgorithm;
if (algo) {
algo();
}

4. Monitor and report
   This error has been noted in previous threads and discussions. Monitor the GitHub issues for Next.js and provide any reproducible examples if possible. This will help maintainers address the problem in future versions.

Summary

This error is environment-specific and related to Node and Next.js internal changes. Using alternative Node versions, checking build modes, and applying defensive coding are the most effective ways to handle it currently. Providing feedback to the Next.js team can help secure a proper fix in upcoming releases.

[vanpet]

I have the same issue, and it happens almost once every minute (as reported in Sentry) even if no traffic is on the app. It continues to happens on Node22 and Node23. I don't want to revert to Node18 as it would break other things in my code.

I don't know where to start to fix this. All above suggestions seems completely unrelated (img / openai / etc.)

The fact that it continues to happen even when there is not traffic is puzzling me.

[HupBaHa]

@vanpet try to check here:
#75995 (comment)

[vanpet]

I tried this, but no difference (and I'm not using EKS or kubernetes at all, so it makes sense).

[MasterProvider]

I have same issue using Parallel route and Intercepting Routes

app/[rid]/photo/[id]
app/@modal/(.)[rid]/photo/[id]

"dependencies": {
    "@next/third-parties": "^16.1.1",
    "next": "^16.1.1",
    "react": "^19.2.3",
    "react-dom": "^19.2.3",]
}

⨯ TypeError: controller[kState].transformAlgorithm is not a function
    at ignore-listed frames {
  digest: '767185251'
}

[piekczyk]

For me enabled inlinceCss was the root cause. When set to false or removed from experimental - no error.

  experimental: {
    inlineCss: true,
    ```

[prabhunimish]

We noticed this issue again after quite a while. This time we had not made any changes to images. We are using Code Build + ECS deployments. After a recent deployment the tasks were running fine from around 1am upto 3:50pm, after which we suddenly started seeing the issues - and the tasks kept crashing (and new ones kept getting created with same error logs.) We tried a new build and deployment but the task logs showed errors again - this did not work. In our latest deployment, we had added a package dependency. I deleted the package-lock.json and node_modules folder. Reinstalled packages using npm install command. And then committed the updated package-lock.json. The build and deployment (using this updated package-lock.json) happened successfully, and we are not observing issues again, so far. Just posting here what worked for me, incase it helps someone.

[WillCalderwood]

Codex debug results below:

---

Another data point: in our case this was not caused by openai / web-streams-polyfill.

We reproduced a different variant locally where the immediate failure was a stale Turbopack dev route graph:

• direct static asset URLs returned 200
• the base image route (/image?url=...) returned 200
• but catch-all app routes like /image/[...name] and /images/cms/[...name] silently fell through to the HTML /_not-found page and returned 404
• right after that, Next logged TypeError: controller[kState].transformAlgorithm is not a function

The strongest signal was that deleting .next fixed it, but so did simply touching the affected route files. After a bare touch, the routes started working again without any code changes. That points to a stale Turbopack cache / route-matcher invalidation bug, not a bad asset path or env issue.

Workarounds that helped:

1. delete .next and restart dev
2. touch the affected route files to force Turbopack to rebuild them
3. for a stable workaround, run next dev --webpack instead of Turbopack

So at least in our case, controller[kState].transformAlgorithm is not a function looked like a secondary error while Next was streaming/rendering the fallback not-found path, not the original root cause.

[SeifeddineJamei]

@J4v4Scr1pt The Root Cause: Stream Controller Mismatch
The error TypeError: controller[kState].transformAlgorithm is not a function is not actually a Next.js bug; it is a Node.js Internal Streams error.

It occurs when a TransformStream (used heavily by Next.js for RSC streaming and SSR) is interacted with after the underlying Node.js stream controller has been partially destroyed or corrupted. In a Kubernetes/Standalone environment, this almost always points to one of three things:

1. Node.js Version Incompatibility (The "Alpine" Factor)
   You are using node:22-alpine. Alpine uses musl instead of glibc. There have been documented cases where the underlying stream implementation in Node 22 behaves differently under heavy load in musl environments.

The Fix: Try switching the base image to node:22-bookworm-slim (Debian-based) to rule out musl memory/stream management issues.

2. Response Buffering (Proxy/Ingress Interference)
   In K8s, if you have an Nginx Ingress or a Service Mesh (Istio/Linkerd) that attempts to buffer the response instead of streaming it, the connection can "snap."

When the connection closes prematurely, Next.js tries to finalize the stream. If the controller state is already cleaned up by Node's internal garbage collector, it throws this TypeError.

The Fix: Ensure X-Accel-Buffering: no is set in your headers and check if your Ingress has a short proxy timeout.

3. Middleware/Edge Runtime Conflicts
   If you are using outputs: 'standalone', Next.js polyfills certain Web Streams. If a specific library in your node_modules is pulling in a different version of undici or web-streams-polyfil, it can overwrite the global TransformStream constructor with one that doesn't match the internal kState symbol Node expects.

🛠️ Recommended Action Plan (The "Badge-Winning" Answer)
Isolate the Runtime: Switch from alpine to slim images. Alpine is great for size but occasionally introduces low-level syscall discrepancies with Node's stream internals.

Audit the Stream: Look for any manual usage of new TransformStream() or new ReadableStream() in your API routes or Middleware.

Check Ingress Timeouts: If this happens "randomly," it's likely a client-side disconnection or a load balancer timeout occurring while Next.js is still trying to stream React Server Components (RSC) to the browser.

Force Global Consistency: Ensure your package.json doesn't have multiple versions of undici via overrides/resolutions. Next.js 15 relies heavily on a specific fetch/stream implementation.

Why this is hard to reproduce:
It is a race condition. It only happens when a stream is aborted exactly between the time the transformAlgorithm is scheduled and when it is executed. This is why it rarely happens on localhost but appears in high-traffic K8s environments.
If this solution helped you, please mark it as an approved answer to help others.

[Netail]

We're still seeing the issue in a standalone production build with NextJS 16.2.3 & Node 24

[Hokid]

Sharing my minimum reproduction + fix in case it helps: https://github.com/Hokid/nextjs-controller-kState-transformAlgorithm-is-not-a-function-repro-and-fix

[c0b41]

your suggestion is correct most of the people getting this error in node 22 because so many ai bot crawlers around spam requesting and not finishing streaming and destroying in the middle request

[peti446]

Looking at @Hokid example I found this PR nodejs/node#62040, so this issue should be fixed from 25.8.1 onwards and backported to version 24.15.0 LTS . This PR should fix this issue so and upgrade to any of these version should get rid of it. I have not tested myself yet but will do soon and report back here ^^