Write refuses to overwrite a file when only its start was read

What

When Claude reads a large file, it may see only the beginning. Claude Code now remembers this, and the Write tool, which writes whole files, refuses to overwrite a file it has seen only part of.

• Write now fails if the earlier read held only the start of the file. Before, Write only checked whether the file had changed since it was last read.
• Read of a large file adds the note "Only the start of this file is shown." and suggests continuing with offset, the setting that picks where reading starts.
• The record of which files were read gains markStartOnly, startOnlyPaths and holdsOnlyStartOf, which track the partly read files.
• A content-entry schema gains an optional startOnly field.

The same finding also notes that the start_rows_max_wait_ms field was removed from a remote-config schema.

Why

Overwriting a file after seeing only its first part could wipe out everything Claude never saw. Claude now has to read the rest of the file first, so expect an extra read or a refused Write on large files.