Copilot Agent inline apply highlight colors changed and inconsistent across IDEA versions

[fengziadmin]

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Description

After upgrading IntelliJ IDEA, the inline highlight colors used by GitHub Copilot Agent when applying code changes have changed significantly.

Previously, the applied changes were highlighted using a dark green / dark red diff-style background, which was subtle and consistent with IntelliJ's native diff and replace preview.

Now, Copilot Agent uses a much lighter / grayish background, which looks like an overlay and is visually distracting. The Accept UI has also changed (Accept All / Discard All).

What’s confusing is that this behavior is inconsistent across IntelliJ IDEA versions, even when using:

• The same GitHub account
• The same Copilot plugin version
• The same OS

One IDEA version shows the old (dark, diff-style) highlight, while another shows the new (light overlay-style) highlight.

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Expected behavior

Copilot Agent should use the same diff-based highlight style as before (dark green / dark red), or at least provide:

• A setting to choose the highlight style
• Or a way to disable the new overlay-style background

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Actual behavior

• Inline applied changes are shown with a light gray / pale green background
• The highlight feels like an overlay instead of a diff
• No configuration option exists to control this behavior

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Environment

• IntelliJ IDEA version: 2025.1.x (different minor builds show different behavior)
• GitHub Copilot plugin version: (same version across machines)
• OS: Windows
• GitHub account: same account on all machines
• UI mode: Tested with both New UI and Classic UI

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Notes

This appears to be related to IntelliJ internal rendering / inline diff pipeline differences rather than Copilot account or plugin version.

It would be great if this behavior could be:

• Made consistent across IDEA versions, or
• Exposed as a user-configurable option

Thanks!
The figure below is normal.

The colors in this image are abnormal.

[fengziadmin]

Thanks for the clear explanation, that aligns with what I’ve been observing.

It’s helpful to know this is likely driven by changes in IntelliJ’s internal inline diff and rendering pipeline rather than Copilot itself. I understand that Copilot is relying on the native APIs here.

I’ll report this to JetBrains as well. Hopefully, with more reports, there can be either a configuration option exposed or a way to preserve the older diff-style rendering, which was more readable.

Thanks again for the thoughtful response and for taking the time to review the details.