On the Linux per-directory watch path, hitting fs.inotify.max_user_watches
surfaces as ENOSPC — which the degrade logic added for #876 (EMFILE/ENFILE
only) did not catch, so it fell through to the silent "skip this directory"
branch: a large repo got a partial watch set with no hint why edits in
unwatched directories stopped auto-syncing.
ENOSPC is non-fatal — raise the limit and partial watching keeps working — so
it now warns ONCE, naming the exact knob (fs.inotify.max_user_watches, with the
sysctl to set it), instead of degrading. It also stops attempting further doomed
watches for the session (every inotify_add_watch would fail too). Installed
watches keep firing; `codegraph sync` / git sync hooks cover the remainder.
Validated on macOS (forced per-directory path) and real Linux (Docker) — the
new test asserts a single warning naming fs.inotify.max_user_watches, no
degrade, and a live partial watch.
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
ab107b325a