[BUG] VSCode extension displays "prompt truncated" message but continues anyway

Preflight Checklist

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

What's Wrong?

I frequeently paste large prompts to ensure content is in context in the first model completion call rather than relying on follow-on tool calls to read the content in its entirety.

In the claude code CLI that works fine. In the VSCode extension I get

[Message truncated - exceeded 50,000 character limit]

1. But it does not clarify whether this is merely a visual display limitation or whether it has truncated the payload sent to the completion API.

1. It just carries on anyway, which would be very bad behavior if it had in fact truncated the prompt sent to the completion API.

This makes the vscode extension unusable for such large prompts and I switch to CLI. But since I cannot predict when I will exceed this prompt size, it is pushing me away from the extension entirely, despite the fact that I otherwise want to use the extension.

What Should Happen?

It should either accept and display the prompt in its entirety or display a message making it much clearer what has gone wrong, and what the consequences are.

If it has truncated the payload sent to the completion API then this is a bug: this should instead be a hard error without submitting the prompt.

Error Messages/Logs

[Message truncated - exceeded 50,000 character limit]

Steps to Reproduce

Paste a prompt exceeding 50,000 characters.

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

VSCode extension 2.1.90

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Other

Additional Information

Complaint is against vscode extension 2.1.90, not claude code or claude.