[BUG] There's an issue with the selected model (claude-sonnet-4-6).

[nibblesnbits]

Preflight Checklist

• I have searched existing issues and this hasn't been reported yet
• This is a single bug report (please file separate reports for different bugs)
• I am using the latest version of Claude Code

What's Wrong?

When trying to use the new Sonnet 4.6 model on the latest Claude Code CLI on both Windows and Ubuntu, I get this output:

juno@juno-thinkpad:~$ claude --model claude-sonnet-4-6

 ▐▛███▜▌   Claude Code v2.1.45
▝▜█████▛▘  Sonnet 4.6 · API Usage Billing
  ▘▘ ▝▝    /home/juno

  /model to try Opus 4.6

❯ this working yet?

● There's an issue with the selected model (claude-sonnet-4-6). It may not exist or you may not have
  access to it. Run /model to pick a different model.

What Should Happen?

Claude should respond without error.

Error Messages/Logs

● There's an issue with the selected model (claude-sonnet-4-6). It may not exist or you may not have
  access to it. Run /model to pick a different model.

Steps to Reproduce

1. Run the Claude Code CLI with claude --model claude-sonnet-4-6 or select the "Sonnet (1M context)" selection with the /model command.
2. Send any prompt.
3. Claude responds with "There's an issue with the selected model"

Claude Model

Sonnet (default)

Is this a regression?

Yes, this worked in a previous version

Last Working Version

No response

Claude Code Version

2.1.45 (Claude Code)

Platform

Anthropic API

Operating System

Ubuntu/Debian Linux

Terminal/Shell

Other

Additional Information

No response

[imindesign96]

me too~

[Kav91]

Had to roll back to 2.0.64 to avoid this problem.

 curl -fsSL https://claude.ai/install.sh | bash -s 2.0.64

[osc707]

same issue here, macOS 26.3.1, pro account, terminal and vscode extension.
Tried downgrading, but it auto upgrades

[TerminatedProcess]

Same here , cachyos linux. exact same message. I did just setup ollama to run claude and select and ollama model, but it started showing that message. Now that I've tried moving it back to opus, it still happens.

[wssiagt]

Same in v2.1.81, windows 11

[nullVallue]

Same here on MacOS Tahoe 26.3.1, ClaudeCode v2.1.81. When is this gonna be fixed, I just upgraded to Pro version and it's already not working, what a great start.

[AdminSam313]

Same thing. Downgrade not helping aswell. My system: 6.12.74+deb13+1-amd64 #1 SMP PREEMPT_DYNAMIC Debian 6.12.74-2 (2026-03-08) x86_64 GNU/Linux. That ai slop is going crazy. That fucking thing now can be even debugged or just emulated. Good job anthropic with you obfuscation and anti-emulation efforts, gg wp!

[ashtanko]

The same issue:

• Claude Code v2.1.81

• OS: Ubuntu

[jayanthmb14]

Guys found the fix it's because 2 diffrent model of Opus is installed. You need to uninstall all the previous model and then install all the model at once.

i have attached the complete instruction (.md File)

Claude_Code_Fix_Guide.md

[nianliunian]

The same issue:

Claude Code v2.1.87

OS: Windows

[ashtanko]

Guys found the fix it's because 2 diffrent model of Opus is installed. You need to uninstall all the previous model and then install all the model at once.

i have attached the complete instruction (.md File)

Claude_Code_Fix_Guide.md

Great job @jayanthmb14! Thanks for the guild, it helped!