kmscon: true colour support is not detected

[thomasmey]

What happened?

Hi,

Fedora is about to switch to https://GitHub.com/kmscon/kmscon instead of Linux native virtual console support.
Kmscon sets the environment variables TERM to linux and COLORTERM to kmscon.
Gemini cli warns that the console does not support 256 colours which is not correct. Kmscon does support true color mode.

What did you expect to happen?

Gemini cli to detect true color mode correctly

Client information

Client Information

Run gemini to enter the interactive CLI, then run the /about command.

> /about
# paste output here

Login information

No response

Anything else we need to know?

No response

[Devnil434]

/assign

[gemini-cli]

👋 @Devnil434, thanks for your interest in this issue! We're reserving self-assignment for issues that have been marked with the help wanted label. Feel free to check out our list of issues that need attention.

[jasonmatthewsuhari]

Hi, I looked into this and was able to reproduce the reported behavior.

With

• TERM=linux
• COLORTERM=kmscon

The current compatibility detection reports

• supports256Colors() === false
• supportsTrueColor() === false

and getCompatibilityWarnings() emits:

• Warning: 256-color support not detected...

That matches the issue report. I found that the logic is in packages/core/src/utils/compatibility.ts:

• supports256Colors() currently only returns true if: process.stdout.getColorDepth() >= 8 or TERM contains 256color
• supportsTrueColor() currently only returns true if: COLORTERM === 'truecolor' or COLORTERM === '24bit' or process.stdout.getColorDepth() >= 24

Because kmscon presents as TERM=linux and COLORTERM=kmscon, it falls through all of those checks.

A good fix for this is probably just a small update to packages/core/src/utils/compatibility.ts accepting TERM=linux & COLORTERM=kmscon with a regression test.