ChatGPT and the ERR_HTTP2_PROTOCOL_ERROR drama, fixed.

ChatGPT was almost unusable on my Windows 11 laptop for around 30 days.

The web version barely worked. The Windows desktop app was unstable. Codex was affected too.

Sometimes ChatGPT would sit there thinking for five or six minutes. Sometimes the sidebar loaded but conversations would not open. Sometimes it looked like a reply was coming, only to end with:

net::ERR_HTTP2_PROTOCOL_ERROR

I also saw:

primaryapi_server_error
HTTP 500
HTTP 503

And this cheerful little message:

biscuit_baker_service_me_circuit_open

Meanwhile, ChatGPT worked on my phone.

Naturally, this made the problem look like an OpenAI account issue, a browser problem, a broken Windows app, an internet problem, or all of them at once.

It was none of those.

The actual cause was:

Killer Network Service

Yes. Software called Killer Network Service was killing my network connection. At least the naming was honest.

My symptoms

These were the main problems:

• ChatGPT took several minutes to reply.
• Replies frequently failed instead of completing.
• Conversations and projects would not open.
• The sidebar loaded very slowly.
• The Windows ChatGPT app kept freezing.
• Codex inside the new desktop app was affected.
• Edge showed ERR_HTTP2_PROTOCOL_ERROR.
• Firefox also failed.
• ChatGPT worked much better from my phone.
• OpenAI’s status page often showed everything working normally.

OpenAI recommends trying another browser, using private mode, disabling VPNs and proxies, clearing browser data, checking security software, and testing another network. I tested all of that. OpenAI Help Center

Nothing fixed it.

Everything I tested

Before finding the cause, I went through the usual troubleshooting marathon.

I tested:

• Microsoft Edge
• Edge InPrivate
• Brave
• Firefox
• The ChatGPT Windows app
• The new combined ChatGPT and Codex app
• Google login
• Email login
• My home internet connection
• A mobile hotspot
• A second OpenAI account
• Browser extensions disabled
• Secure DNS disabled
• No VPN
• No proxy
• ChatGPT app Repair
• Windows DNS flush
• Winsock reset
• TCP/IP reset

The second OpenAI account worked at first, which made me think my main account was broken.

Then the second account also failed.

That ruled out the account.

Firefox failed too, which ruled out this being only a Chromium or Edge problem.

The same errors happened through another internet connection, which made the router and ISP less likely.

At this point, something inside Windows was clearly messing with the connection.

The first real clue: HTTP/1.1 worked

I launched Edge with HTTP/2 and QUIC disabled.

Run this in PowerShell:

$edge="${env:ProgramFiles(x86)}\Microsoft\Edge\Application\msedge.exe"

if (!(Test-Path $edge)) {
    $edge="$env:ProgramFiles\Microsoft\Edge\Application\msedge.exe"
}

Stop-Process -Name msedge -Force -ErrorAction SilentlyContinue

Start-Process $edge -ArgumentList `
    '--disable-http2', `
    '--disable-quic', `
    "--user-data-dir=$env:TEMP\ChatGPT-HTTP1-Test", `
    '--disable-extensions', `
    'https://chatgpt.com'

ChatGPT suddenly worked.

Not “slightly better.”

It worked quickly and normally.

Inside Edge Developer Tools, the requests were using:

http/1.1

When I repeated the same test with HTTP/2 enabled, ChatGPT froze again.

The comparison was clear:

That was the turning point.

ChatGPT itself was not the main problem.

Something on my computer was breaking HTTP/2 traffic.

Temporary ChatGPT workaround

Before finding the proper fix, I created a separate ChatGPT shortcut that forced Edge to use HTTP/1.1.

Run this once in PowerShell:

$edge="${env:ProgramFiles(x86)}\Microsoft\Edge\Application\msedge.exe"

if (!(Test-Path $edge)) {
    $edge="$env:ProgramFiles\Microsoft\Edge\Application\msedge.exe"
}

$profile="$env:LOCALAPPDATA\ChatGPT-HTTP1"
$desktop=[Environment]::GetFolderPath("Desktop")
$shell=New-Object -ComObject WScript.Shell

$shortcut=$shell.CreateShortcut(
    "$desktop\ChatGPT HTTP1.lnk"
)

$shortcut.TargetPath=$edge
$shortcut.Arguments="--disable-http2 --disable-quic --disable-extensions --user-data-dir=`"$profile`" --app=https://chatgpt.com"
$shortcut.WorkingDirectory=Split-Path $edge
$shortcut.IconLocation="$edge,0"
$shortcut.Save()

This creates a desktop shortcut called:

ChatGPT HTTP1

It opens ChatGPT in its own Edge window with HTTP/2 disabled.

The connection is still encrypted through HTTPS. This only changes the HTTP version.

It was a useful temporary fix, but I still wanted the normal website, desktop app, and Codex to work properly.

The same workaround fixed the real desktop app

The new combined ChatGPT and Codex Windows app uses its own Chromium network process.

I launched the actual app with HTTP/2 and QUIC disabled:

$pkg = Get-AppxPackage OpenAI.Codex
$exe = Join-Path $pkg.InstallLocation 'app\ChatGPT.exe'

Get-Process -Name ChatGPT,codex -ErrorAction SilentlyContinue |
    Stop-Process -Force

Start-Sleep 2

Start-Process -FilePath $exe `
    -ArgumentList '--disable-http2','--disable-quic'

The app started working.

Chat worked. Codex responded too.

That proved the desktop application was not completely broken. Its HTTP/2 connection was being damaged by something else on the computer.

Finding the actual cause

I checked which networking and filtering services were installed.

Run:

Get-NetAdapter |
    Format-Table Name,InterfaceDescription,Status,LinkSpeed -AutoSize

My laptop had:

Killer Wi-Fi 6E AX1675i
Killer E3100G 2.5 Gigabit Ethernet Controller

Then I checked for Killer services:

Get-CimInstance Win32_Service |
    Where-Object {
        $_.Name -match 'Killer|Rivet|KAPS|DBWM' -or
        $_.DisplayName -match 'Killer|Rivet|Prioritization|Dynamic Bandwidth'
    } |
    Format-Table State,StartMode,Name,DisplayName -AutoSize

The result included:

KAPSService
Killer Analytics Service
Killer Network Service
KNDBWM

I also had McAfee WebAdvisor installed, so I tested that first.

Stopping McAfee WebAdvisor did not fix the problem.

Then I stopped the Killer services.

$killer = @(
    'KAPSService',
    'Killer Analytics Service',
    'Killer Network Service',
    'KNDBWM'
)

$killer | ForEach-Object {
    Stop-Service -Name $_ -Force -ErrorAction Continue
}

ChatGPT immediately started working over normal HTTP/2.

No special Edge shortcut.

No HTTP/1.1 workaround.

Normal Edge, normal Firefox, and normal ChatGPT.

We then restarted the Killer services one at a time.

The problem returned when this service started:

Killer Network Service

Stopping that one service fixed ChatGPT again.

The final test was simple:

Killer Network Service running:
ChatGPT freezes and HTTP/2 fails.

Killer Network Service stopped:
ChatGPT works normally.

Other people have reported Killer Network Service preventing websites from loading on both Wi-Fi and Ethernet, with stopping or disabling the service fixing the issue. Intel Community

Intel also documents disabling the Killer Prioritization Engine and managing Killer Network Service when the software causes problems. Intel

The permanent fix

Open PowerShell as Administrator.

Stop the service:

Stop-Service -Name 'Killer Network Service' -Force

Disable it so it does not start again after rebooting:

Set-Service -Name 'Killer Network Service' `
    -StartupType Disabled

Run the stop command once more:

Stop-Service -Name 'Killer Network Service' -Force

Check the result:

Get-Service -Name 'Killer Network Service' |
    Format-Table Name,Status,StartType

You want to see:

Name                     Status   StartType
----                     ------   ---------
Killer Network Service   Stopped  Disabled

Then restart the computer.

Use Restart, not only Shut down and turn it back on later.

What happened after restarting

After disabling Killer Network Service and restarting:

• ChatGPT worked normally in Edge.
• ChatGPT worked normally in Firefox.
• HTTP/2 worked again.
• Conversations and projects opened normally.
• Replies streamed normally.
• The Windows ChatGPT app worked.
• Codex worked inside the combined desktop app.
• The five-minute delays disappeared.
• ERR_HTTP2_PROTOCOL_ERROR disappeared.
• My Ethernet and Wi-Fi adapters continued working.

I disabled the traffic-management service, not the actual network adapters.

Keep the other Killer services running

On my computer, only this service caused the problem:

Killer Network Service

The others remained enabled:

KAPSService
Killer Analytics Service
KNDBWM

You can check them with:

Get-Service -Name `
    'Killer Network Service', `
    'KNDBWM', `
    'KAPSService', `
    'Killer Analytics Service' |
    Format-Table Name,Status,StartType -AutoSize

My final configuration was:

KAPSService               Running
Killer Analytics Service  Running
Killer Network Service    Stopped / Disabled
KNDBWM                     Running

Do not disable every Killer service immediately.

Stop Killer Network Service first, restart your browser, and test.

One change at a time. Otherwise, you may fix the problem without learning what actually caused it.

How to undo the change

To turn Killer Network Service back on, open PowerShell as Administrator and run:

Set-Service -Name 'Killer Network Service' `
    -StartupType Automatic

Start-Service -Name 'Killer Network Service'

Then restart Windows.

Does this fix apply to you?

This is worth testing when:

• ChatGPT works on your phone but not your PC.
• ChatGPT web and the Windows app both freeze.
• Replies take several minutes.
• You see ERR_HTTP2_PROTOCOL_ERROR.
• Edge and Firefox both have the same issue.
• Changing browsers does not help.
• Changing OpenAI accounts does not help.
• Changing internet connections does not help.
• ChatGPT works when HTTP/2 is disabled.
• Your computer has Killer Ethernet or Wi-Fi hardware.
• Killer Network Service is installed and running.

Check whether you have Killer hardware:

Get-NetAdapter |
    Format-Table Name,InterfaceDescription,Status,LinkSpeed -AutoSize

Then check the service:

Get-Service -Name 'Killer Network Service'

If it exists, stop it temporarily:

Stop-Service -Name 'Killer Network Service' -Force

Close every browser window, reopen the browser, and test ChatGPT again.

If ChatGPT suddenly works normally, you have probably found the same issue.

Final result

For 30 days, the problem looked like OpenAI was broken.

To be fair, OpenAI support did not exactly cover itself in glory. I went through login errors, generic troubleshooting replies, duplicated support tickets, and one support response that somehow thought I wanted to cancel my subscription.

But the actual problem was local:

Killer Network Service

Disabling that single service fixed:

• ChatGPT web
• Firefox
• Edge
• ChatGPT desktop
• Codex
• HTTP/2 traffic

So before you reinstall Windows, delete your account, cancel Plus, or throw your monitor out of the window, check whether Intel Killer Network Service is running.

It may save you several days of bullshit.