[BUG] Title: File modification system-reminders consume excessive context

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?

When editing files in Claude Code (VS Code extension), file modifications trigger large <system-reminder> blocks that include extensive excerpts of the modified files.

Even very small edits (a few lines) result in 50–200+ lines of code being injected into context per file. When multiple files are touched, these system-reminders accumulate rapidly and consume most of the available context.

In one recent session, context usage jumped from about 87% to 100% after only two small edits because diffs from several project files were included automatically.

This makes sessions become unusable much faster than expected and prevents completing multi-file tasks.

What Should Happen?

File modification notifications should use minimal context, for example:

only the file path and line range changed, or

a short summary of the change

There should be an option to:

disable file-modification system-reminders entirely, or

make them much more compact without including large code excerpts.

This would allow longer productive sessions and prevent context from being consumed by repeated file diffs instead of user interactions.

Error Messages/Logs

Steps to Reproduce

Open VS Code with the Claude Code extension enabled.

Open a project with multiple source files.

Start a new Claude chat session.

Edit a file (change only a few lines).

Save the file.

Observe that a <system-reminder> message is generated containing large excerpts of the modified file (often 50–200+ lines).

Repeat steps 4–5 on one or two additional files.

Observe that context usage increases rapidly (for example, jumping from ~87% to 100%) even though only small edits were made.

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

claude-opus-4-5-20251101

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

VS Code integrated terminal

Additional Information

_No response_