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+# Ambient Drift Coach — Design
+
+**Date:** 2026-06-05
+**Status:** Approved, ready for implementation planning
+**Scope:** Give Keel an always-on presence. Today Keel only coaches *inside* a
+declared focus session; the moment you are just working, the harness goes idle,
+drops every window snapshot, and the status bar reads `idle`. This slice adds an
+**ambient drift coach**: a sentinel that watches the window stream continuously
+(even when no mode is active), judges your recent activity against the broad
+`~/owc` frame (goals, values, life-domains) plus today's Marvin tasks, and —
+when you have clearly slid off what matters — surfaces a single coaching line to
+the status bar, a `notify-send` toast, and a web-UI banner you can act on.
+
+This builds the **Control loop / scheduler** component from
+`docs/keel-architecture.md` §3, which today has zero implementation, and is the
+first thing that makes Keel *show up unprompted* (SOUL: "when my partner drifts,
+I name it").
+
+## Problem
+
+The focus mode is already a capable proactive coach — local on-task matching, an
+LLM drift judge, a semantic "nudge" over recent window titles, surfaced to the
+status bar and web UI, all sensibly debounced. But every bit of it hangs off a
+**declared `Commitment`**. You must open the UI and start a session first. With
+no session:
+
+- `harness.RecordWindow` finds no active mode and silently drops the snapshot.
+- `statusfile.Render` of an empty envelope returns `idle`.
+- No brain call ever happens; Keel is blind and mute.
+
+So the common case — Felix working without ceremonially declaring a task — gets
+nothing. The fix is an observer that runs regardless of the active mode and is
+grounded in the standing frame instead of a per-session commitment.
+
+## Approach (and the one real fork)
+
+The ambient coach is **not a mode**. It is an always-on **sentinel** that runs
+*beside* the one-mode harness. Two harness invariants make "ambient as a mode"
+the wrong shape:
+
+1. The harness hosts exactly one mode and drops evidence when idle — an ambient
+ watcher must run continuously, including when idle.
+2. `harness.Start` returns `ErrBusy` if a different mode is active — an ambient
+ mode would either block you from starting focus, or need a special
+ auto-yield carve-out that erodes the single-mode contract.
+
+A sentinel sidesteps both and matches §3, where the control loop is a distinct
+component beside the harness. **Coexistence rule:** when any harness mode is
+active (`h.State().ActiveMode != ""`), the sentinel stays silent — focus mode
+already owns coaching during a declared session, so there is never double
+coaching.
+
+## Components
+
+Each unit has one responsibility, a defined interface, and is testable alone.
+
+### 1. `internal/notify` — notification effector (new)
+
+The OS-level "interrupt me" primitive, mirroring `enforce.Guard`.
+
+- **Interface:** `Notifier interface { Notify(ctx context.Context, title, body string) error }`
+- **Linux adapter:** shells `notify-send
`. Best-effort: returns
+ an error for diagnostics; callers never block on it.
+- **Constructor:** `NewNotifier() Notifier` returns the real adapter when the
+ `notify-send` binary is found on `PATH` (via `exec.LookPath`), else a nop. On
+ non-Linux it is a nop. This means a missing binary degrades to "no toast,"
+ never a failure.
+- **Nop:** `Notify` returns nil, does nothing.
+- **Depends on:** `os/exec` only. Leaf package.
+
+### 2. `internal/frame` — shared frame assembler (new; DRY extraction)
+
+The "what matters to Felix" brief, today duplicated inside off-screen's
+`collect.go`. Extracting it removes the duplication and gives the sentinel the
+same grounding off-screen uses.
+
+- **Interface:** `Assemble(ctx context.Context, know knowledge.Source, tasks tasks.Provider) string`
+ returns a bounded markdown brief with three sections: **Today's tasks**
+ (from `tasks.Today`), **Goals** (`~/owc/goals-2026.md` via `knowledge.Load`),
+ and **Life domains** (every `~/owc/resources/bug-*.md` via `knowledge.Load`).
+- **Best-effort:** never panics, never errors; tolerates nil ports and missing
+ files, degrading to a short, mostly-empty brief. Same truncation cap
+ (`maxBriefBytes`) and rune-safe clipping off-screen uses today.
+- **Refactor:** off-screen's `briefTasks` / `briefGoals` / `briefLifeDomains`
+ are replaced by a call to `frame.Assemble`; off-screen keeps its own
+ proposal-history section (`briefHistory`) prepended around it. Off-screen's
+ existing tests must stay green.
+- **Depends on:** `knowledge`, `tasks`. Imports nothing from `ai`/`mode`.
+
+### 3. `internal/ai` — `AmbientDrift` method (new; mirrors `Nudge`)
+
+The brain call grounded in the frame, not a commitment.
+
+- **Method:** `func (s *Service) AmbientDrift(ctx context.Context, frame string, recentTitles []string) (string, error)`
+ returns `""` when the activity plausibly serves the frame (on-track), and a
+ one-sentence coaching line when it is a slide.
+- **Prompt:** an "ambient coach" prompt stating the user has **not** declared a
+ task; it is handed the frame and the recent window-title sequence and asked
+ whether the activity serves **any** of what matters, **forgivingly** —
+ legitimate breaks, rest, and unplanned-but-useful work are on-track. Output is
+ `ONLY` JSON: `{"drifting": , "message": ""}`.
+- **Parse (`parseAmbientDrift`):** reuses `extractJSON` and the shared
+ `ErrEmptyResponse` / `ErrNoJSON` sentinels. `drifting:false` → `""`.
+ `drifting:true` with a message → the message. `drifting:true` with no message →
+ `""` (silence) — the ambient signal is advisory, so the safe degenerate is to
+ say nothing, exactly like `parseNudge`.
+- **Depends on:** the existing `Backend`. `ai` stays a leaf (primitives only).
+
+### 4. `internal/ambient` — the Sentinel (new; the meat)
+
+Always-on observer: consume evidence → tick on cadence → judge → surface.
+
+**Construction:** `New(deps)` where deps carry `*ai.Service`, `knowledge.Source`,
+`tasks.Provider`, `notify.Notifier`, `memory.Store`, `clock func() time.Time`,
+and `activeMode func() string` (reads `h.State().ActiveMode` for the coexistence
+rule). Config: `cadence time.Duration` and `mode` (`off` | `status` | `notify`).
+
+**State (under one mutex):** `recentTitles []string` (consecutive-dedup ring,
+capped like focus's `recentTitlesMax`), `lastWindow evidence.WindowSnapshot`,
+`line string` (current drift line; `""` when on-track), `lastEvalTitles`
+(snapshot of the ring at the last brain call), `wasDrifting bool`,
+`episodeNotified bool`, `snoozeUntil time.Time`, `gen int`, and `onChange []func()`.
+
+**Methods:**
+
+- `OnWindow(snap evidence.WindowSnapshot)` — called from the evidence fan-out.
+ Updates `lastWindow`, appends the title to the ring (skip consecutive dup,
+ cap). Cheap and lock-bounded; fires no brain call.
+- `Run(ctx context.Context)` — cadence loop: a ticker every `cadence` calls
+ `evaluate()`; returns on ctx cancel.
+- `evaluate()` — the decision (see Trigger discipline below).
+- `Line() string` — current ambient line for the surfaces (`""` when on-track,
+ quiet, or snoozed).
+- `Snooze(d time.Duration)` — sets `snoozeUntil = clock()+d`; clears the line and
+ episode flags; fires `onChange`. While snoozed, `evaluate()` returns early.
+- `SetConfig(cadence time.Duration, mode string)` — live settings update.
+- `AddOnChange(f func())` — register a surface refresh (status wake, web
+ broadcast). Fired whenever the line changes.
+
+**Depends on:** `ai`, `frame`, `notify`, `memory`, `evidence`, and a
+`activeMode` closure. It does **not** import `harness` (closure injection keeps
+it decoupled and testable).
+
+### 5. Wiring — `cmd/keeld/main.go`
+
+- **Build** the notifier (`notify.NewNotifier()`) and the sentinel from settings
+ (cadence, mode) and the shared ports (the same `ai.Service`, `knowledge`,
+ `tasks`, `memory`, clock used to build `harness.Services`), with
+ `activeMode: func() string { return h.State().ActiveMode }`.
+- **Fan the evidence stream to both** the harness and the sentinel:
+ ```go
+ go src.Watch(ctx, func(w evidence.WindowSnapshot) {
+ h.RecordWindow(w)
+ sentinel.OnWindow(w)
+ })
+ ```
+- **Run** the sentinel: `go sentinel.Run(ctx)`.
+- **Surface refresh:** register both the status writer's `Wake` and the web
+ broadcast with `sentinel.AddOnChange(...)`, so a new ambient line re-renders
+ the bar and pushes over SSE promptly.
+- **Live settings:** `applyFn` (the existing POST `/settings` re-wire) also calls
+ `sentinel.SetConfig(...)` from the new settings, so the dial takes effect
+ without a restart.
+
+## Trigger discipline (aggressive, but not trigger-happy)
+
+A `notify-send` toast on a false positive is far more irritating than a stale
+status line, so `evaluate()` is conservative and brain-call-thrifty:
+
+1. If `mode == off` → return.
+2. If snoozed (`clock() < snoozeUntil`) → return.
+3. If `activeMode() != ""` → a mode is coaching; clear the line (if set), fire
+ `onChange`, return. (Coexistence rule.)
+4. **Cheap gate:** if the ring is unchanged since `lastEvalTitles` **and** we are
+ currently on-track (`line == ""`) → skip the brain call. This naturally
+ pauses calls during steady deep work *and* while AFK (no new titles arrive in
+ either case), while still re-checking an unresolved drift.
+5. Assemble the frame (`frame.Assemble`) and call
+ `ai.AmbientDrift(ctx, frame, recentTitles)` under a timeout.
+6. Apply the result:
+ - **On-track (`""`):** if a line was set, clear it and reset
+ `wasDrifting=false`, `episodeNotified=false`; fire `onChange`. Otherwise no-op.
+ - **Drifting (`msg`):**
+ - **New episode** (`!wasDrifting`): set `line=msg`, `wasDrifting=true`,
+ `episodeNotified=false`; fire `onChange`. The **status bar / banner show
+ immediately**, but **no toast yet**.
+ - **Sustained** (already `wasDrifting` on this consecutive eval): record an
+ `ambient_nudge` event to `memory` (`{ "message": msg, "title":
+ lastWindow.Title, "class": lastWindow.Class }`), and — if `mode == notify`
+ and `!episodeNotified` — fire exactly one `notify-send` toast and set
+ `episodeNotified=true`. Further sustained ticks do not re-toast.
+ - On a brain **error**, leave the prior line intact and log — never fabricate
+ drift (same discipline as `Nudge`).
+7. Update `lastEvalTitles` to the current ring.
+
+Net effect with the default ~5-minute cadence: a 40-second glance at Twitter
+never pops a toast (it resolves before the second tick); a sustained ~10-minute
+slide shows on the bar at the first tick and pops one toast at the second.
+Memory records only *sustained* drifts, independent of the surface mode.
+
+## Surfaces
+
+- **Status bar (`internal/statusfile`):** `Render` gains the current ambient line
+ (passed in by the `Writer`, which reads `sentinel.Line`). When the envelope is
+ idle (`ActiveMode == ""`): a non-empty line renders `⚠ `; an empty line
+ renders `idle` as today. Non-idle envelopes are unchanged. The `Writer` adds an
+ `ambientLine func() string` source and `sentinel.AddOnChange(writer.Wake)`
+ drives prompt re-render; the existing minute ticker still applies.
+- **Web UI (`internal/web` + `static/app.js`):** the served state gains an
+ `"ambient": ""` field (read from `sentinel.Line`), pushed over the
+ existing SSE channel via `sentinel.AddOnChange(broadcast)`. `app.js` renders a
+ **banner** when the field is non-empty: the coaching line plus two controls —
+ **Snooze 1h** (`POST /ambient/snooze`) and **Start focus** (reuses the existing
+ start-session affordance so a nudge converts into a declared session). The
+ banner clears automatically when the line goes empty.
+- **New endpoint:** `POST /ambient/snooze` → `sentinel.Snooze(1 * time.Hour)`.
+ Returns 204. No body needed in v1.
+
+## Config (the agency-vs-cage dial, §8)
+
+`settings.Settings` gains two fields (env-seedable, mirroring the existing ones):
+
+- `ambient_mode` (`KEEL_AMBIENT_MODE`): `off` | `status` | `notify`. Default
+ `notify`. Validated in the settings applier (like `ai_backend`); an unknown
+ value is rejected with a wrapped sentinel so POST `/settings` can map it to 400.
+- `ambient_cadence_secs` (`KEEL_AMBIENT_CADENCE_SECS`): integer seconds between
+ evaluations. Default `300`. A non-positive value falls back to the default.
+
+The web settings form gains a select (`ambient_mode`) and a number input
+(`ambient_cadence_secs`); `applyFn` pushes both into `sentinel.SetConfig`.
+
+## Error handling & graceful degradation
+
+- **No `notify-send` binary / non-Linux:** nop notifier; status line and banner
+ still work.
+- **Brain error / timeout:** `AmbientDrift` returns an error; the sentinel logs
+ and leaves the prior line intact. Never fabricates drift.
+- **AW down:** `memory` is already the nop store; `ambient_nudge` writes are
+ dropped silently.
+- **`knowledge` / `tasks` errors:** `frame.Assemble` degrades to a partial brief
+ (best-effort), never errors.
+- **Headless / no X11:** the evidence source is a no-op, so `OnWindow` is never
+ called, the ring stays empty, the cheap gate skips every brain call, and the
+ sentinel is silent. No new X11 requirement.
+- **Nothing in the sentinel can crash the daemon** — every external call is
+ best-effort and lock-bounded.
+
+## Testing
+
+- **`internal/ambient`** (fake clock, fake `ai` with scriptable `AmbientDrift`
+ returns and a call counter, fake `notify.Notifier` recording calls, fake
+ `tasks`/`knowledge`, `activeMode` stub, `memory.Fake`):
+ - on-track → no line, no toast, no memory.
+ - single drift tick → line set, **no** toast, no memory yet.
+ - two consecutive drift ticks → line set, **exactly one** toast, one
+ `ambient_nudge` event.
+ - third consecutive drift tick → still one toast (once per episode).
+ - back on-track → line cleared, flags reset.
+ - `activeMode() != ""` → no eval, line cleared.
+ - `mode == status` → drift sets the line but never toasts (memory still records
+ the sustained drift).
+ - `mode == off` → nothing happens, no brain call.
+ - snooze → no eval / no line during the window.
+ - cheap gate → unchanged ring + on-track → assert the fake `ai` call count does
+ **not** increase.
+- **`internal/notify`:** `NewNotifier` with `notify-send` absent → nop; `Notify`
+ returns nil, no panic. (The real shell path is not unit-tested.)
+- **`internal/ai`:** `parseAmbientDrift` — on-track→`""`, drift+msg→msg, drift
+ with no msg→`""`, empty→`ErrEmptyResponse`, no-JSON→`ErrNoJSON`.
+- **`internal/frame`:** `Assemble` with fake ports — sections present; nil ports
+ and missing files degrade without error; truncation honored. Off-screen's
+ existing tests stay green after the refactor.
+- **`internal/statusfile`:** idle + ambient line → `⚠ …`; idle + empty line →
+ `idle`; non-idle envelopes unaffected.
+- **`internal/web`:** served state includes `ambient`; `POST /ambient/snooze`
+ routes to `Snooze` and returns 204.
+- **`internal/settings`:** `ambient_mode` validation (good values accepted,
+ unknown rejected with the sentinel); cadence default on non-positive.
+
+## Out of scope (deliberate, for a later slice)
+
+- **AFK precision via the AW afk bucket.** v1 uses the cheap-gate heuristic
+ (no new titles ⇒ no call), which covers both AFK and deep-focus well enough.
+ Reading AW's input-derived afk bucket to *prove* presence is a future collector.
+- **Ambient enforcement** (window-minimize). The sentinel is advisory only;
+ minimizing windows with no declared session would be far too cagey. Enforcement
+ stays a focus-session decision.
+- **Trend / spiral detection** over the accumulating `ambient_nudge` history
+ (§7). This slice *produces* that history; reading it for cross-time patterns is
+ the next increment.
+- **Richer banner actions** beyond snooze + start-focus (e.g. "I'm on it",
+ per-domain mute).
+
+## Open questions
+
+- **Default cadence.** 300 s is a starting guess; may want tuning after living
+ with it. Configurable, so cheap to change.
+- **Snooze duration.** Fixed 1 h in v1; a picker is a later refinement.