fff watcher pegs CPU on repos with nested worktrees: post-rescan directory queue runs a libgit2 status per directory #50719

OpenCode 1.18.32 on macOS 26.5.1 (arm64), bundled @ff-labs/fff-bun 0.9.4.

Related, different trigger: #42557 (per-event status on gitignored build output), #32511 (home-directory scanning), #43356 (crash in the same resubscribe-after-scan path).

What happens

Repo: ~7k tracked files, plus 27 untracked nested git worktrees under wt/ (~240k files). fff at the repo root indexed 245,895 files and 25,847 directories.

Two TUI sessions started at the repo root ran 5-7 h with two fff-watcher-own threads each at 100% CPU (machine load average 31, 10 GB swap). sample <pid> shows the owner thread in Repository::open → Repository::statuses / status_file → git_index_read, one call per queued directory, 10-350 ms each. A third session started inside one worktree (7,874 files) had the same threads idle.

Trigger

Reproduced with @ff-labs/fff-node 0.9.4 watching the root: creating one new worktree under wt/ produced ~8k file-create and ~1k folder-create events, 2 full rescans, and 2,375 owner-thread git_status_for_paths calls (19 s CPU) in ~40 s.

After a full rescan, rescubscribe_watcher_post_scan queues every indexed directory for the owner thread. The queue is unbounded and not deduplicated (scan.rs, background_watcher.rs in fff v0.9.4), so each rescan costs minutes of CPU per fff instance, and the queue never drains while worktrees keep being created.

A read-only experiment (fresh index, one requested rescan, then one minute of measurement):

fff 0.11.0 separates Subscribe from IndexNewDir, so a rescan's subscription no longer indexes every directory on macOS.

Config gaps

• watcher.ignore reaches only the Parcel watcher, not fff.
• fff InitOptions has no ignore/exclude option; only gitignore rules shrink the index.
• disableWatch exists in fff-bun, but OpenCode does not pass it.
• OPENCODE_DISABLE_FFF=1 is the only switch. With it, search falls back to ripgrep (one file query on a 7.9k-file tree: 25 ms, 0.11 s CPU).

Workaround

Gitignore the nested-worktree folder (or add it to .git/info/exclude): the root scan drops from 245,895 files to 7,140. Or set OPENCODE_DISABLE_FFF=1.

Asks

1. Bump the bundled fff to ≥ 0.11, or backport a bounded, deduplicated post-rescan directory queue.
2. Honour watcher.ignore when creating the fff picker.
3. Expose fff's disableWatch behind a config key.