Remote file staging can compare with the store and skip matching downloads

What

In remote sessions, Claude Code can stage a file, which means downloading a copy from a remote file store so it is available locally. New code can first ask the store for the file's details and compare them with the local copy:

• Store lookup: it calls /v1/filestore/fs/readFileMetadata to get the file's size and md5 (a fingerprint of its contents) and compares them with the local file.
• Local hashing: it computes the local file's fingerprint only when the local file is read-only (mode 0444), has a single hard link and has the same size as the stored file.
• Verdict: the result is one of same_contents, md5_differs, size_differs, local_file_changed and others.
• Skipping: in mode on, a matching file is not downloaded again and the step is recorded as already_present. Before, the file was always fetched.
• Pausing: if the check fails, it pauses for a set time or for the rest of the process (stage_file_store_check_paused).
• Modes: the mode comes from the tengu_quiet_ledger gate, which accepts only count, on or off and falls back to off in the code. The staging step passes the gate value only when e.force === !0, and passes off otherwise. What count does differently from on was not traced.
• Real path check: on Linux, the existing already-present check now confirms the file's real location through /proc/self/fd.

Nothing has been read about the tengu_quiet_ledger or tengu_stage_file_completed gates, so whether this is active is not known.

Why

When the active mode is on, files that are already present and unchanged would not be downloaded again in remote sessions. The extra Linux path check makes the already-present decision rely on where the file really is.