watcher.ignore never reaches the embedded fff engine — per-dir inotify watches on every indexed dir (192K watches / 4.5GB RSS on a large root); root .ignore file is the only effective channel #37740

Summary

watcher.ignore in opencode.json(c) never reaches the embedded fff engine. fff's scanner honors only gitignore-family channels (.gitignore, .git/info/exclude, .ignore), and on Linux its watcher then registers one non-recursive inotify watch for every directory the picker indexed. On a large multi-repo workspace root this produced 192,033 inotify watches and 2.5–4.5 GB RSS in opencode serve, no matter what watcher.ignore contained.

Placing a ripgrep-style .ignore file at the project root is a complete cure: watches dropped 192,033 → 778 and steady-state RSS ~4.5 GB → 448 MB, with file search still working correctly. This is the root cause behind the class of reports like #23190 (closed stale, never root-caused: "only an actual .gitignore inside a real .git repo avoids it" — that observation was correct, and this is why), and it's the Linux/memory sibling of #32511 (fff content-indexing $HOME on macOS). Likely also relevant to #32930 / #16610 (inotify exhaustion) and the memory megathread #20695.

Environment

Checked release notes through 1.18.3 — no watcher/picker/memory fix in the range, so this should still reproduce on current.

Evidence chain

1. The watches belong to fff, and watcher.ignore does not affect them.

Resolving every watched inode (/proc/<pid>/fdinfo/<inotify-fd> → inode → path) accounted for 100% of the watches. The top watched subtrees were exactly the directories listed in watcher.ignore:

14036  /data/state/...        ← listed in watcher.ignore
 5893  /data/runner/...       ← listed in watcher.ignore
 ...   (16 more runner/CI trees, all listed)

2. Config-glob matrix (converged watch counts, each state held stable ≥3 min before reading; the scan takes ~5 min to converge after start):

The halving is the tell: there are two watcher instances — opencode's own (which does honor watcher.ignore, with relative globs) and fff's (which never sees it). Config changes can only ever fix the first one.

3. Mechanism, from fff-core source (fff.nvim's Rust engine, embedded in the opencode binary — the fff-scan / fff-watcher-own / notify-rs threads):

• crates/fff-core/src/walk/ripgrep.rs — the walk is built with .git_ignore(true) .git_exclude(true) .git_global(true) .ignore(true); custom overrides exist only for non-git roots and only from a hardcoded IGNORED_DIRS const (node_modules, __pycache__, …). There is no channel for embedder-supplied patterns like watcher.ignore.
• crates/fff-core/src/watcher/background_watcher.rs — on Linux (no kernel recursion in inotify) it iterates picker.for_each_dir(...) and registers RecursiveMode::NonRecursive per directory. Watch set = indexed set. Whatever the scan doesn't prune, the watcher pays for at ~1 KB kernel memory per watch, plus the picker's own index memory.

4. The .ignore cure, verified end-to-end:

.ignore at the project root with anchored top-level patterns:

/repos/
/runner/
/state/
/logs/
...

Result, reproduced exactly across restarts: 778 watches, 650 MB anon / 448 MB RSS (from ~2.5 GB anon), /find/file returns correct results, excluded trees still directly readable via /file/content (only search indexing is affected).

5. fff rescans dynamically — deleting the .ignore file at runtime ballooned watches back to ~192K within minutes, without a restart. (Good news: the reverse means the file can also be added without restarting, though we restarted to reclaim the watches.)

Why this matters beyond memory

In server mode this compounds: on our host the growth ended in the process wedged in mem_cgroup_handle_over_high (uninterruptible sleep, port listening but never accepting — connections queue in the backlog forever) while systemd still reported it healthy. Any deployment that caps the service with MemoryHigh converts this leak into a silent hang rather than a crash-restart.

Suggested fixes (any subset helps)

1. Wire watcher.ignore (or a dedicated files.ignore) into fff's walk as ignore overrides — the ignore crate's OverrideBuilder already supports this; fff-core would need to accept embedder patterns (currently only the hardcoded IGNORED_DIRS const, and only for non-git roots).
2. Until then, document that watcher.ignore does not apply to fff and that a root .ignore file is the effective channel. What is the point of watcher.ignore #6740 ("What is the point of watcher.ignore") and watcher.ignore in opencode.json does not prevent hang in non-git dirs with large subtrees #23190 both died on this gap.
3. Consider a watch budget with graceful degradation (stop adding watches past N, keep serving) — related: fix(core): prevent hang when inotify watches are exhausted #32930, Opencode hangs at startup if a .git repo is present and inotify user instances run out #16610.

Happy to provide the full measurement methodology (inode→path resolution scripts, per-fd watch accounting) if useful.