Read no longer answers a repeat read with a 'file unchanged' result

What

Read is the tool Claude uses to open files. It used to have a shortcut: if Claude read a file again and it had not changed since the last read, Read could send back a short file_unchanged result instead of the file's content. That shortcut has been removed:

• The code in Read that produced file_unchanged is deleted. It was guarded by the tengu_read_dedup_killswitch flag and a dedupUnchangedReads setting; this code no longer reads the flag, and whether anything else still reads it was not checked.
• The dedupUnchangedReads setting is gone from the tool's context, including a place that set it to false.
• Read's output description no longer includes the file_unchanged type or its seeded source, which marked a match against something loaded at startup, such as CLAUDE.md or nested memory files, rather than an earlier Read.
• The way a file_unchanged result was turned into a message for Claude is removed too.
• Reminders that tell Claude a text file was edited now carry a rereadEntry (a hash and a length) when the file had been read in full.

The stock description of the Read tool, captured under this release, is unchanged.

Why

In this code, a repeat read of an unchanged file no longer gets the short stub. Whether unchanged re-reads are now handled somewhere else, for example through the new rereadEntry, is not shown, so how much of the conversation repeat reads take up may differ.