Idle filter: suppress when watched process (claude) is running in distro

Probes wsl.exe -d <distro> -- pgrep -x claude before flagging a WSL pane
idle, with a 3s per-distro cache on the Rust side. If claude is running
anywhere in the distro, all panes in that distro stay out of the idle set
(per-pane granularity is out of scope — PIDs aren't observable from
Windows). PowerShell + SSH panes skip the probe and keep the legacy
always-notify behaviour.

memory.md

@@ -29,7 +29,8 @@ Durable memory for this project. Read at session start, update before session en
 - [x] ~~**M4 — orchestration.** Broadcast input, idle notifications, Ctrl+K palette.~~ Done 2026-05-22.
 - [x] ~~**Auto-save debouncing.**~~ 500ms timer in `App.svelte` `$effect`.
 - [x] ~~**HMR distro picker reset.**~~ No longer an issue — per-pane distro selection.
-- [ ] **Idle detection: filter by "claude is foreground."** Currently every pane notifies after 5s silence, which fires too eagerly when the user is reading a `claude` response. Want to detect that `claude` (or any user-specified process) is actually running in the pane's shell before notifying. Needs a Rust-side probe over WSL: `wsl.exe -d <distro> ps --ppid <shell_pid> -o comm=`. Defer to a future polish pass.
+- [x] ~~**Idle detection: filter by "claude is foreground."** Currently every pane notifies after 5s silence, which fires too eagerly when the user is reading a `claude` response. Want to detect that `claude` (or any user-specified process) is actually running in the pane's shell before notifying.~~ Done 2026-05-26 — per-distro probe via `wsl.exe -d <distro> -- pgrep -x claude`, cached 3s on the Rust side. WSL panes only; PS + SSH fall back to legacy always-notify. Watched list hardcoded to `["claude"]` — `[[user-watch-list]]` follow-up below.
+- [ ] **`[[user-watch-list]]` — user-configurable idle-suppress process list.** v1 hardcodes `DEFAULT_WATCH_PROCESSES = ["claude"]` in `src-tauri/src/probe.rs`. Move to a workspace-config field (or dedicated `watch.json`) so users can add `cargo`, `npm test`, `pytest`, etc. without a recompile. Two design notes: (1) the values are passed straight to `pgrep -x`, so user-supplied strings must be validated (no shell metachars / leading `-`) before reaching `probe_one`; (2) the cache key is currently just the distro name — if the watched-list becomes per-pane / per-workspace, key the cache by `(distro, sorted_watch_list)` to prevent stale answers.
 - [ ] **Native OS notifications.** Right now toasts only show while the app is focused. `tauri-plugin-notification` would push to Windows Action Center; useful for "claude finished" when the app is minimized. Worth adding if/when the user actually backgrounds the app while waiting for sessions.
 - [ ] **Configurable idle threshold.** Hardcoded 5000ms in `LeafPane.svelte`. Should move into a settings panel; M5 territory.
 - [x] ~~**Logic tests for `tree.ts`.**~~ Vitest, 43 cases, runs via `pnpm test`. Done 2026-05-22.
@@ -52,6 +53,44 @@ Durable memory for this project. Read at session start, update before session en
 
 ## Session log
 
+### 2026-05-26 — Idle filter: suppress when `claude` is running in the distro
+
+The idle indicator used to fire 5s after any silence, regardless of what the pane was doing. While the user reads a long `claude` response the pane is silent (claude is processing or the human is reading) and the red border + titlebar "N idle" count is just noise. Fixed: WSL panes now probe the backend before flagging idle, and stay quiet if `claude` is running anywhere in the distro.
+
+**Granularity is per-distro, not per-pane.** Identifying which Windows pane corresponds to which Linux-side shell inside WSL is too complex (PIDs aren't visible from Windows; ProcMon-style probes are fragile). Agreed trade-off: if claude is running in distro X, ALL panes in distro X suppress. Over-suppression for multi-pane-same-distro users is fine — the previous always-notify bug was worse, and that user pattern is the minority.
+
+**Architecture:**
+
+1. New `src-tauri/src/probe.rs` module with `ProbeCache` — `parking_lot::Mutex<HashMap<String, (Instant, bool)>>` keyed by distro name, 3s TTL. Sized against the frontend's 1s idle-tick: ~one `wsl.exe` call per distro per 3 ticks even with many panes polling, while reacting to "claude finished" within a few seconds.
+2. Probe command runs `wsl.exe -d <distro> -- pgrep -x claude` via `quiet_command_pub` (new public alias of the existing `quiet_command` in pty.rs so cross-module callers don't re-implement the `CREATE_NO_WINDOW` dance). Exit 0 = match, exit 1 = no match, anything else = probe failure.
+3. **Fail-safe is suppression.** Any probe error (wsl.exe missing, distro stopped, pgrep not installed) resolves to `true` → frontend suppresses the idle indicator. Matches the agreed trade-off: over-suppression beats false-positive notifications.
+4. New Tauri command `is_watch_process_running(distro)`. Wrapped in `tokio::task::spawn_blocking` because the shell-out can take 100-300ms — keep it off the async runtime's thread pool.
+5. `LeafPane.tsx` idle-detection effect rewritten: when the tick says "now idle", branch by `shellKind`. WSL → probe backend, suppress if true. PowerShell + SSH → skip the probe and fall back to legacy behaviour (PS has no portable `ps`; SSH processes live on a remote box; out of scope for v1). Includes `inFlight` guard so a slow probe doesn't stack with subsequent ticks, and a `cancelled` flag for the React-18-StrictMode cleanup pattern we always use here.
+
+**Watched list is currently hardcoded.** `DEFAULT_WATCH_PROCESSES: &[&str] = &["claude"]` in probe.rs. Comment marks the v2 follow-up: surface as a workspace-config field, key the cache by `(distro, sorted_list)` if it becomes per-pane, and validate user-supplied strings against `pgrep` shell-injection (no `-` prefix, no shell metachars).
+
+**Files touched:**
+
+- `src-tauri/src/probe.rs` — new module (~150 lines).
+- `src-tauri/src/pty.rs` — `quiet_command_pub` exposed for cross-module use.
+- `src-tauri/src/lib.rs` — register the module, the `ProbeCache` state, and the command in `invoke_handler`.
+- `src-tauri/src/commands.rs` — `is_watch_process_running` Tauri command.
+- `src/ipc.ts` — `isWatchProcessRunning` TS wrapper.
+- `src/lib/layout/LeafPane.tsx` — idle-detection effect now branches on shellKind and gates WSL transitions through the probe.
+
+**Validated:**
+
+- `pnpm check` clean (0 errors).
+- `pnpm test` clean (72 tree.ts tests pass — no UI tests yet, so the React-side change isn't covered automatically).
+- Rust side authored in WSL; user to run `cargo build / cargo check -p tiletopia_lib` from Windows before merging.
+
+Open follow-ups specific to this session:
+
+- **`[[user-watch-list]]` config surface.** See open-questions section above. Probably 30 min of work: add `watchProcesses?: string[]` to workspace.json, validate per-name (no `-`, no shell metachars, length cap), thread through to a new `is_watch_process_running_for` command that takes the list, key the cache by `(distro, sorted_list_hash)`.
+- **Probe latency-as-jitter.** First idle tick after 5s silence triggers a 100-300ms `wsl.exe` shell-out. The user sees the red border flicker on for ~one tick before the probe resolves and clears it. Not visually obvious in practice (the red is already a transient signal), but could pre-warm the cache on a slower interval if it bites.
+- **PowerShell idle filter.** PS has no `ps` equivalent we can probe cheaply; closest is `Get-Process` + a watched-list mapping (`claude` doesn't exist on Windows, but `cargo`, `npm`, `python` do). Defer until someone actually runs a long-running CLI in PS and complains.
+- **Workspace-edit migration of the `LeafPane.svelte` mention** in the open-question section about the 5000ms threshold — file says `.svelte` but we're React now. Drive-by, not done here ("don't refactor unrelated code").
+
 ### 2026-05-26 — Hard-deny: PowerShell patterns + label list de-duplicated
 
 Mirrors the POSIX hard-deny rules with their Windows/PowerShell equivalents. Four new patterns: