view tool rejects a normal 8.6 KB file as too large to read at once

Describe the bug

The built-in view tool (shown as Read in the VS Code UI) reports File too large to read at once (8.6 KB) when asked to read a small, ordinary multiline Markdown file. This appears to be a false-positive size warning and makes normal full-file inspection unnecessarily cumbersome.

This is not the large single-line JSON or custom-tool-output case. The file is a regular Markdown document and is approximately 8.6 KB.

Affected version

Unknown - encountered in the Copilot CLI runtime integrated with VS Code.

Steps to reproduce the behavior

1. Use the Copilot CLI runtime in VS Code on Windows.
2. Ask the agent to read a normal multiline Markdown file of approximately 8.6 KB.
3. Allow the built-in view/Read tool to read the file without specifying a range.
4. Observe the File too large to read at once (8.6 KB) warning instead of the file contents.

Expected behavior

A normal file of this size should be read successfully in full. If a size threshold is required, the threshold should be consistent, documented, and should not report ordinary small files as too large without a clear reason.

Additional context

• OS: Windows 11
• Host: Visual Studio Code
• Tool: built-in view/Read
• File type: regular Markdown, approximately 8.6 KB
• The warning recommends using view_range, even though the file is small enough that a full read would normally be expected.
• This report is about the view tool's full-file size handling, not Azure DevOps or the repository being inspected.

組み込みの view/Read 実装とファイル全体のサイズチェックを特定し、説明されている Windows と VS Code のセットアップで、約 8.6 KB の複数行 Markdown ファイルを使って再現します。この正常なファイルが拒否される理由を追跡します。完了条件は、誤検知の警告なしにファイル全体を読み取れることと、実際にサイズが大きすぎる入力や単一行の入力については適切な処理が引き続き行われることです。