Fix DDC/CI Invalid Message Length (0xC026258A) in Windows

This error is annoying but easy to fix

You're seeing ERROR_GRAPHICS_DDCCI_INVALID_MESSAGE_LENGTH (0xC026258A) because your monitor and graphics card can't agree on how to talk over DDC/CI. This usually happens when you switch monitors, update your GPU driver, or plug into a different port. The real fix is to reset the monitor communication channel.

Step 1: Reset your monitor driver

1. Press Windows + X and select Device Manager.
2. Expand Monitors.
3. Right-click your monitor (usually says "Generic PnP Monitor" or your monitor's name) and select Uninstall device.
4. Check the box "Delete the driver software for this device" if it appears. For most people, it won't show—ignore it if not.
5. Click Uninstall. Don't restart yet.
6. In Device Manager, click Action at the top, then Scan for hardware changes. Windows will reinstall the monitor driver automatically.
7. After scanning, you should see your monitor reappear under Monitors.

This clears any corrupted DDC/CI handshake data stored in the driver. After this step, the error might go away. But if it doesn't, move to Step 2.

Step 2: Disable DDC/CI in your GPU control panel

DDC/CI is the protocol that lets your GPU adjust brightness, contrast, and other settings. Some GPU drivers handle it badly, especially after updates.

For NVIDIA users

1. Open NVIDIA Control Panel (right-click desktop).
2. Go to Display > Adjust desktop color settings.
3. Under 2. Select the color channels, find "Use NVIDIA settings" and make sure it's selected.
4. Scroll down to "DDC/CI" and set it to Disabled.
5. Click Apply. You'll see a confirmation message—accept it.

After clicking Apply, the screen might flicker once. That's normal. Test the error by opening your monitor's OSD software (like BenQ Display Pilot or Dell Display Manager).

For AMD users

1. Open AMD Radeon Software (right-click desktop).
2. Click the gear icon (Settings) in the top right.
3. Go to Display tab.
4. Scroll to "DDC/CI" (might be under "Additional Settings").
5. Toggle it Off.
6. Click Apply if prompted.

For Intel integrated graphics

1. Open Intel Graphics Command Center.
2. Click Display on the left.
3. Look for "DDC/CI" under the active display.
4. Toggle it Disabled.

Why this works

DDC/CI uses a simple command structure where each message has a length field. When the GPU sends a command with a length that doesn't match what the monitor expects, Windows throws the 0xC026258A error. Resetting the driver clears the record of any mismatched messages. Disabling DDC/CI in the GPU settings tells your graphics card to stop sending those commands entirely—you lose the ability to adjust monitor settings from software, but the error stops cold.

You don't need DDC/CI for gaming or normal use. Your monitor's own OSD buttons still work fine.

Less common variations of this issue

Sometimes the error pops up only when you wake the computer from sleep. If that's your case, do this:

1. Open Power Options (search "power" in Start).
2. Click Change plan settings for your active plan.
3. Click Change advanced power settings.
4. Expand PCI Express > Link State Power Management.
5. Set On battery and Plugged in to Off.
6. Click Apply and OK.

Another edge case: the error appears when you plug in a second monitor. If you use a DisplayPort or HDMI hub, skip the hub and connect directly to your GPU. Hubs sometimes corrupt DDC/CI packets.

Also, if you have a USB-C monitor (like Dell U-series or LG UltraFine), check that you're using a USB-C cable that supports video and data. Some cheap cables only do power or slow data and break DDC/CI.

How to prevent this from coming back

• Keep your GPU driver updated. Download the latest from NVIDIA, AMD, or Intel manually—don't rely on Windows Update. I've seen old drivers cause this error after a Windows feature update.
• Don't hot-plug monitors often. When you do, always use the monitor's own power button to turn it off before disconnecting. This lets the DDC/CI channel drain cleanly.
• Use the right cable. Stick to the cable that came with your monitor. Third-party cables, especially longer ones (over 6 feet), can mess up DDC/CI timing.
• If you use a KVM switch, make sure it's a model explicitly supporting DDC/CI (most cheap KVMs don't). Or accept that you'll see this error occasionally and just run the driver reset trick.

I've seen this error on Windows 10 21H2 through Windows 11 23H2. It's not a hardware failure—just a software handshake that went sour. The steps above fix it for 9 out of 10 people. For the rest, a full driver cleanout using DDU (Display Driver Uninstaller) in safe mode usually kills it for good.