Add idle-state classifier and Solo-parity timer tools

Classifies every running child as idle/working/thinking/permission/error using one of three pluggable strategies (output_activity, osc_title_stability, osc_title_status) plus optional regex promoters applied to the tail of recent output. State and last-match reason are exposed via MCP on ProcessInfo and get_process_status. Per-preset configuration lives on a new preset.IdleDetection block with bundled defaults for the first-party claude/codex/opencode presets. OSC title plumbing is exposed as Emulator.Title(), polled from the session pump after each emulator write so title-change activity feeds into the classifier without an extra cgo callback. The MCP timer surface expands to match Solo: timer_set, timer_fire_when_idle_any/all, timer_cancel, timer_pause, timer_resume, timer_list. timer_wait is now a thin wrapper that shares the same manager so it shows up in timer_list while pending. Timer bodies are delivered to the owner process through the existing InjectAsOrchestrator path. Top-level (non-agent) callers can attach timers to a specific process via owner_process_id; omitting it grants universal cancel/pause/resume/list privileges. The sidebar gains a state glyph per process row and appends a nearest-timer indicator when one is pending or paused. Tests: idle_test.go covers the classify() pure function across the three strategies and regex promotion; timers_test.go covers the manager. Harness scenarios cover output_activity, osc_title_stability, osc_title_status, and regex promotion, plus timer_set delivery, cancel, pause/resume, idle_any-on-transition, idle_all-pending, and idle_all-already-satisfied. A new wait_until_mcp harness step type polls an MCP method until an assertion holds.
2026-05-15 09:49:59 +01:00
parent 1af032472b
commit 2b9e1ed77c
31 changed files with 2318 additions and 38 deletions
--- a/internal/app/app.go
+++ b/internal/app/app.go
@@ -113,6 +113,11 @@ func Run(ctx context.Context, opts Options) error {
 	ctx, cancel := context.WithCancel(ctx)
 	defer cancel()

+	// Per-session idle-detection classifier. One goroutine ticks every
+	// 250ms over every live child and updates IdleState. It stops when
+	// ctx is cancelled.
+	go sess.runClassifier(ctx)
+
 	st := &uiState{
 		sess:       sess,
 		presets:    presets,
@@ -120,6 +125,7 @@ func Run(ctx context.Context, opts Options) error {
 		pads:       pads,
 		chromeWake: make(chan struct{}, 1),
 		trust:      trustStore,
+		timers:     host.timers,
 		hostCols:   cols,
 		hostRows:   rows,
 		stdinTTY:   term.IsTerminal(int(os.Stdin.Fd())),
@@ -296,6 +302,7 @@ type uiState struct {
 	launcher *Launcher
 	pads     *scratchpad.Store
 	trust    *trust.Store
+	timers   *timerManager

 	outMu sync.Mutex

@@ -610,6 +617,14 @@ func (st *uiState) OnChildSpawned(c *Child) {
 	st.drawStatusLine()
 }

+// OnChildStateChanged repaints the sidebar whenever a child's
+// idle-state badge flips. Cheap — the badge is the only chrome that
+// reflects state today, and drawSidebar bails when the cached frame
+// hasn't changed.
+func (st *uiState) OnChildStateChanged(string, IdleState) {
+	st.drawSidebar()
+}
+
 // OnChildExited drops focus and shows the empty state if it was the
 // focused child.
 func (st *uiState) OnChildExited(c *Child) {
--- a/internal/app/child.go
+++ b/internal/app/child.go
@@ -123,6 +123,19 @@ type Child struct {
 	portsMu sync.Mutex
 	ports   []PortSighting

+	// Idle-detection state. idleState carries the classifier's current
+	// opinion (StateIdle / StateWorking / …). lastTitleNS is the wall
+	// time of the most recent OSC title change — separate from
+	// lastWriteNS so the osc_title_* strategies can ignore plain output
+	// churn. idleDetection is the compiled per-preset config, resolved
+	// once at spawn and immutable thereafter.
+	idleState     atomic.Pointer[IdleState]
+	idleReason    atomic.Pointer[string]
+	titleMu       sync.RWMutex
+	title         string
+	lastTitleNS   atomic.Int64
+	idleDetection *resolvedIdleDetection
+
 	cleanupMu    sync.Mutex
 	cleanupPaths []string
 	restarting   atomic.Bool
@@ -330,6 +343,75 @@ func (c *Child) IdleMS() int64 {
 	return (time.Now().UnixNano() - last) / int64(time.Millisecond)
 }

+// TitleIdleMS returns how many milliseconds since the OSC window title
+// last changed. 0 means "no title set yet".
+func (c *Child) TitleIdleMS() int64 {
+	last := c.lastTitleNS.Load()
+	if last == 0 {
+		return 0
+	}
+	return (time.Now().UnixNano() - last) / int64(time.Millisecond)
+}
+
+// Title returns the most recent OSC 0/2 title.
+func (c *Child) Title() string {
+	c.titleMu.RLock()
+	defer c.titleMu.RUnlock()
+	return c.title
+}
+
+// recordTitle updates the cached title and bumps lastTitleNS when it
+// actually changes. Called from Session.pumpChild after each PTY chunk
+// — cheap because most chunks don't carry an OSC sequence.
+func (c *Child) recordTitle(newTitle string) {
+	c.titleMu.Lock()
+	if c.title == newTitle {
+		c.titleMu.Unlock()
+		return
+	}
+	c.title = newTitle
+	c.titleMu.Unlock()
+	c.lastTitleNS.Store(time.Now().UnixNano())
+}
+
+// IdleState returns the classifier's current opinion. Empty string
+// (StateUnknown) means the classifier hasn't run yet for this child.
+func (c *Child) IdleState() IdleState {
+	p := c.idleState.Load()
+	if p == nil {
+		return StateUnknown
+	}
+	return *p
+}
+
+// IdleReason returns the human-readable reason the classifier last
+// recorded. Empty when no classification has happened yet.
+func (c *Child) IdleReason() string {
+	p := c.idleReason.Load()
+	if p == nil {
+		return ""
+	}
+	return *p
+}
+
+// setIdleState updates idleState + idleReason. Returns true when the
+// state actually changed (so callers can fan out a notification).
+func (c *Child) setIdleState(s IdleState, reason string) bool {
+	prev := c.IdleState()
+	if prev == s {
+		return false
+	}
+	c.idleState.Store(&s)
+	c.idleReason.Store(&reason)
+	return true
+}
+
+// setIdleDetection installs the resolved per-preset idle-detection
+// config. Called once at spawn; not safe to swap at runtime.
+func (c *Child) setIdleDetection(r *resolvedIdleDetection) {
+	c.idleDetection = r
+}
+
 func (c *Child) recordWrite(chunk []byte) {
 	c.lastWriteNS.Store(time.Now().UnixNano())
 	c.screenVersion.Add(1)
--- a/internal/app/classifier.go
+++ b/internal/app/classifier.go
@@ -0,0 +1,96 @@
+package app
+
+import (
+	"context"
+	"time"
+)
+
+// classifierTickInterval is how often the per-session classifier wakes
+// up to re-evaluate every child's state. 250ms is fast enough that
+// the sidebar badge looks live, slow enough that the cost is invisible
+// even with dozens of children.
+const classifierTickInterval = 250 * time.Millisecond
+
+// classifierTailBytes is the size of the ring-buffer tail the
+// classifier scans for promoter regexes. Big enough to catch a multi-
+// line "Approve?" prompt, small enough that we don't pay for a full
+// 1 MiB regex scan every tick.
+const classifierTailBytes = 4096
+
+// runClassifier loops over every live child every classifierTickInterval
+// and updates IdleState when it changes. It runs until ctx is cancelled
+// (the host shutdown path cancels). One goroutine per Session is plenty
+// — the work is cheap (atomic loads + ~4 KiB regex scan per child).
+func (s *Session) runClassifier(ctx context.Context) {
+	ticker := time.NewTicker(classifierTickInterval)
+	defer ticker.Stop()
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case <-ticker.C:
+			s.classifyAll()
+		}
+	}
+}
+
+func (s *Session) classifyAll() {
+	for _, c := range s.Children() {
+		s.classifyOne(c)
+	}
+}
+
+func (s *Session) classifyOne(c *Child) {
+	st := c.Status()
+	exited := st == StatusExited || st == StatusErrored
+	exitNonZero := false
+	if exited {
+		exitNonZero = c.ExitCode() != 0
+	}
+	idleMS := c.IdleMS()
+	titleIdleMS := c.TitleIdleMS()
+	title := c.Title()
+	tail := c.tailBytes(classifierTailBytes)
+	state, reason := classify(c.idleDetection, exited, exitNonZero, idleMS, titleIdleMS, title, tail)
+	if c.setIdleState(state, reason) {
+		s.emitStateChanged(c.ID, state)
+	}
+}
+
+// tailBytes returns up to n bytes from the end of the ring buffer.
+// Safe to call from the classifier goroutine while pumpChild writes
+// from another goroutine — both serialise on ringMu.
+func (c *Child) tailBytes(n int) []byte {
+	c.ringMu.Lock()
+	defer c.ringMu.Unlock()
+	have := int64(ringCap)
+	if !c.ringFull {
+		have = c.ringWrites
+	}
+	if have == 0 {
+		return nil
+	}
+	want := int64(n)
+	if want > have {
+		want = have
+	}
+	out := make([]byte, want)
+	// The ring layout matches StreamRead: when not full, byte k lives
+	// at index k; when full, the oldest byte sits at ringPos and the
+	// newest at (ringPos-1) mod ringCap.
+	if !c.ringFull {
+		copy(out, c.ring[c.ringWrites-want:c.ringWrites])
+		return out
+	}
+	// Tail starts `want` bytes back from the write head.
+	start := (c.ringPos - int(want) + ringCap) % ringCap
+	first := ringCap - start
+	if first > int(want) {
+		first = int(want)
+	}
+	copy(out, c.ring[start:start+first])
+	if first < int(want) {
+		copy(out[first:], c.ring[:int(want)-first])
+	}
+	return out
+}
--- a/internal/app/host.go
+++ b/internal/app/host.go
@@ -61,12 +61,11 @@ type toolHost struct {
 	prompter  trustPrompter
 	scratch   scratchpadSink

-	timersMu  sync.Mutex
-	nextTimer int
+	timers *timerManager
 }

 func newToolHost(sess *Session, pads *scratchpad.Store, launcher *Launcher, presets preset.Set, tr *trust.Store, cols, rows uint16) *toolHost {
-	return &toolHost{
+	h := &toolHost{
 		sess:       sess,
 		pads:       pads,
 		launcher:   launcher,
@@ -76,6 +75,28 @@ func newToolHost(sess *Session, pads *scratchpad.Store, launcher *Launcher, pres
 		defaultRow: rows,
 		startedAt:  make(map[string]time.Time),
 	}
+	h.timers = newTimerManager(sess)
+	// Plug the timer manager into the session's state-change fan-out so
+	// idle-aware timers fire when watched children transition into idle.
+	// Tests can construct a host with a nil session for sizing checks —
+	// those never run timers, so the subscribe is skipped.
+	if sess != nil {
+		sess.Subscribe(timerListenerAdapter{m: h.timers})
+	}
+	return h
+}
+
+// timerListenerAdapter forwards OnChildStateChanged into the timer
+// manager and ignores the other ChildEventListener methods. The
+// session's listener API is by-interface, so we wrap the manager
+// rather than make it implement the full surface.
+type timerListenerAdapter struct{ m *timerManager }
+
+func (a timerListenerAdapter) OnChildSpawned(*Child)             {}
+func (a timerListenerAdapter) OnChildExited(*Child)              {}
+func (a timerListenerAdapter) OnPTYOut(string, []byte)           {}
+func (a timerListenerAdapter) OnChildStateChanged(id string, st IdleState) {
+	a.m.onChildStateChanged(id, st)
 }

 func (h *toolHost) SetSize(cols, rows uint16) {
@@ -531,6 +552,7 @@ func (n *chunkNotifier) OnPTYOut(id string, chunk []byte) {
 	default:
 	}
 }
+func (n *chunkNotifier) OnChildStateChanged(string, IdleState) {}

 func (h *toolHost) GetProcessPorts(callerID, processID string) ([]mcp.PortSighting, error) {
 	c := h.sess.FindChild(processID)
@@ -725,27 +747,59 @@ func (h *toolHost) RequestHumanAttention(callerID, processID, reason string) err
 	return nil
 }

+// TimerWait is the legacy fire-and-forget delay timer. It now wraps
+// TimerSet with an empty body — defaultFireFn substitutes the
+// "[system] Your timer […] has completed." line so behaviour matches
+// the original API. New callers should use timer_set with an explicit
+// body.
 func (h *toolHost) TimerWait(callerID string, seconds float64, label string) (string, error) {
-	caller := h.sess.FindChild(callerID)
-	if caller == nil {
-		return "", mcp.Errorf(mcp.ErrorKindNotFound, "caller %q not known to patterm", callerID)
+	return h.timers.TimerSet(callerID, "", label, seconds)
+}
+
+func (h *toolHost) TimerSet(callerID string, args mcp.TimerSetArgs) (mcp.TimerHandle, error) {
+	owner := resolveTimerOwner(callerID, args.OwnerProcessID)
+	id, err := h.timers.TimerSet(owner, args.Body, args.Label, args.Seconds)
+	if err != nil {
+		return mcp.TimerHandle{}, err
 	}
-	h.timersMu.Lock()
-	h.nextTimer++
-	id := fmt.Sprintf("t%d", h.nextTimer)
-	h.timersMu.Unlock()
-	if label == "" {
-		label = id
+	return mcp.TimerHandle{ID: id}, nil
+}
+
+func (h *toolHost) TimerFireWhenIdleAny(callerID string, args mcp.TimerFireWhenIdleArgs) (mcp.TimerFireWhenIdleResponse, error) {
+	owner := resolveTimerOwner(callerID, args.OwnerProcessID)
+	return h.timers.TimerFireWhenIdleAny(owner, args.Body, args.Label, args.Watched, args.MaxWaitSeconds)
+}
+
+func (h *toolHost) TimerFireWhenIdleAll(callerID string, args mcp.TimerFireWhenIdleArgs) (mcp.TimerFireWhenIdleResponse, error) {
+	owner := resolveTimerOwner(callerID, args.OwnerProcessID)
+	return h.timers.TimerFireWhenIdleAll(owner, args.Body, args.Label, args.Watched, args.MaxWaitSeconds)
+}
+
+// resolveTimerOwner picks the owner process for a timer. Explicit
+// owner_process_id wins; otherwise the caller's own id is used.
+// Top-level MCP clients (no callerID) must provide owner_process_id
+// explicitly.
+func resolveTimerOwner(callerID, explicit string) string {
+	if explicit != "" {
+		return explicit
 	}
-	go func() {
-		time.Sleep(time.Duration(seconds * float64(time.Second)))
-		if !caller.IsLive() {
-			return
-		}
-		line := fmt.Sprintf("[system] Your timer [%s] has completed.\r", label)
-		_ = caller.InjectAsOrchestrator([]byte(line))
-	}()
-	return id, nil
+	return callerID
+}
+
+func (h *toolHost) TimerCancel(callerID, id string) error {
+	return h.timers.TimerCancel(callerID, id)
+}
+
+func (h *toolHost) TimerPause(callerID, id string) error {
+	return h.timers.TimerPause(callerID, id)
+}
+
+func (h *toolHost) TimerResume(callerID, id string) error {
+	return h.timers.TimerResume(callerID, id)
+}
+
+func (h *toolHost) TimerList(callerID string) ([]mcp.TimerInfo, error) {
+	return h.timers.TimerList(callerID), nil
 }

 // ───────────────────────────────────────────────────────────────────
@@ -816,6 +870,10 @@ func (h *toolHost) processInfoOf(c *Child) mcp.ProcessInfo {
 		t := h.trust.IsTrusted(c.PresetRef)
 		info.Trusted = &t
 	}
+	if s := c.IdleState(); s != StateUnknown {
+		info.IdleState = string(s)
+		info.IdleReason = c.IdleReason()
+	}
 	return info
 }

--- a/internal/app/idle.go
+++ b/internal/app/idle.go
@@ -0,0 +1,225 @@
+package app
+
+import (
+	"regexp"
+
+	"github.com/hjbdev/patterm/internal/preset"
+)
+
+// IdleState is the classifier's opinion about what a child is doing.
+// Inspired by Solo's five-state model. ERROR is a terminal state — set
+// when a child exits non-zero or matches an error-promoter regex —
+// while the other four reflect transient runtime state.
+type IdleState string
+
+const (
+	StateUnknown    IdleState = ""
+	StateIdle       IdleState = "idle"
+	StateWorking    IdleState = "working"
+	StateThinking   IdleState = "thinking"
+	StatePermission IdleState = "permission"
+	StateError      IdleState = "error"
+)
+
+// IdleStrategy picks the primary signal used to decide idle vs working.
+// Promoter regexes can override this on top.
+type IdleStrategy string
+
+const (
+	StrategyOutputActivity    IdleStrategy = "output_activity"
+	StrategyOSCTitleStability IdleStrategy = "osc_title_stability"
+	StrategyOSCTitleStatus    IdleStrategy = "osc_title_status"
+)
+
+// defaultIdleThresholdMS is used when a preset doesn't override it.
+const defaultIdleThresholdMS = 2000
+
+// resolvedIdleDetection is the compiled, runtime-ready form of a
+// preset.IdleDetection block. Built once at child spawn and held
+// read-only by the classifier; regex patterns are compiled here so the
+// hot path doesn't pay for it.
+type resolvedIdleDetection struct {
+	strategy        IdleStrategy
+	idleThresholdMS int64
+
+	titleStatusMap map[string]IdleState
+
+	permissionRegexes []*regexp.Regexp
+	thinkingRegexes   []*regexp.Regexp
+	errorRegexes      []*regexp.Regexp
+}
+
+// resolveIdleDetection compiles a preset.IdleDetection (which may be
+// nil) into the runtime form. Unknown strategies fall back to
+// output_activity. Pattern compile errors are skipped silently — the
+// preset loader is responsible for surfacing them as warnings.
+func resolveIdleDetection(cfg *preset.IdleDetection) *resolvedIdleDetection {
+	r := &resolvedIdleDetection{
+		strategy:        StrategyOutputActivity,
+		idleThresholdMS: defaultIdleThresholdMS,
+	}
+	if cfg == nil {
+		return r
+	}
+	switch IdleStrategy(cfg.Strategy) {
+	case StrategyOSCTitleStability, StrategyOSCTitleStatus, StrategyOutputActivity:
+		r.strategy = IdleStrategy(cfg.Strategy)
+	}
+	if cfg.IdleThresholdMS > 0 {
+		r.idleThresholdMS = int64(cfg.IdleThresholdMS)
+	}
+	if len(cfg.TitleStatusMap) > 0 {
+		r.titleStatusMap = make(map[string]IdleState, len(cfg.TitleStatusMap))
+		for k, v := range cfg.TitleStatusMap {
+			switch IdleState(v) {
+			case StateIdle, StateWorking, StateThinking, StatePermission, StateError:
+				r.titleStatusMap[k] = IdleState(v)
+			}
+		}
+	}
+	r.permissionRegexes = compilePatterns(cfg.PermissionPatterns)
+	r.thinkingRegexes = compilePatterns(cfg.ThinkingPatterns)
+	r.errorRegexes = compilePatterns(cfg.ErrorPatterns)
+	return r
+}
+
+func compilePatterns(ps []string) []*regexp.Regexp {
+	if len(ps) == 0 {
+		return nil
+	}
+	out := make([]*regexp.Regexp, 0, len(ps))
+	for _, p := range ps {
+		if p == "" {
+			continue
+		}
+		re, err := regexp.Compile(p)
+		if err != nil {
+			continue
+		}
+		out = append(out, re)
+	}
+	return out
+}
+
+// classify computes the IdleState from the inputs the classifier loop
+// has already gathered. Pure function so it's easy to unit-test.
+//
+// Resolution order:
+//  1. terminal: process exited non-zero → error (latched)
+//  2. error-promoter regex match in recent output → error
+//  3. permission-promoter regex match → permission
+//  4. thinking-promoter regex match → thinking
+//  5. strategy-specific base classification (idle vs working).
+//
+// inputs:
+//   - exited: whether the child process has exited
+//   - exitNonZero: whether the exit was non-zero (only meaningful when exited)
+//   - idleMS: ms since the last PTY output
+//   - titleIdleMS: ms since the last OSC title change (0 if no title yet)
+//   - title: current OSC title
+//   - tail: recent output bytes for regex matching
+func classify(cfg *resolvedIdleDetection, exited, exitNonZero bool, idleMS, titleIdleMS int64, title string, tail []byte) (IdleState, string) {
+	if exited {
+		if exitNonZero {
+			return StateError, "process exited non-zero"
+		}
+		return StateIdle, "process exited cleanly"
+	}
+	if cfg == nil {
+		cfg = &resolvedIdleDetection{strategy: StrategyOutputActivity, idleThresholdMS: defaultIdleThresholdMS}
+	}
+	if len(tail) > 0 {
+		if matchAny(cfg.errorRegexes, tail) {
+			return StateError, "error regex matched"
+		}
+		if matchAny(cfg.permissionRegexes, tail) {
+			return StatePermission, "permission regex matched"
+		}
+		if matchAny(cfg.thinkingRegexes, tail) {
+			return StateThinking, "thinking regex matched"
+		}
+	}
+	threshold := cfg.idleThresholdMS
+	switch cfg.strategy {
+	case StrategyOSCTitleStatus:
+		// First try the title-status map; if no match, fall back to
+		// title-stability behaviour so we still produce idle/working.
+		if s, ok := matchTitleStatus(cfg.titleStatusMap, title); ok {
+			return s, "title status match"
+		}
+		fallthrough
+	case StrategyOSCTitleStability:
+		// If we've never seen a title, fall back to output activity so
+		// we don't latch in idle while the child is clearly running.
+		if titleIdleMS == 0 {
+			return baseStateFromIdleMS(idleMS, threshold)
+		}
+		return baseStateFromIdleMS(titleIdleMS, threshold)
+	default: // output_activity
+		return baseStateFromIdleMS(idleMS, threshold)
+	}
+}
+
+func baseStateFromIdleMS(idleMS, threshold int64) (IdleState, string) {
+	// idleMS == 0 means "no writes yet" (per Child.IdleMS) — treat as
+	// not-idle so we don't classify a freshly-spawned child as idle.
+	if idleMS == 0 {
+		return StateWorking, "no activity yet"
+	}
+	if idleMS < threshold {
+		return StateWorking, "recent activity"
+	}
+	return StateIdle, "quiet for threshold"
+}
+
+func matchAny(res []*regexp.Regexp, tail []byte) bool {
+	for _, re := range res {
+		if re.Match(tail) {
+			return true
+		}
+	}
+	return false
+}
+
+func matchTitleStatus(m map[string]IdleState, title string) (IdleState, bool) {
+	if len(m) == 0 || title == "" {
+		return StateUnknown, false
+	}
+	for k, v := range m {
+		if k == "" {
+			continue
+		}
+		if containsFold(title, k) {
+			return v, true
+		}
+	}
+	return StateUnknown, false
+}
+
+// containsFold reports whether s contains sub, case-insensitively.
+// Cheap implementation suitable for short titles.
+func containsFold(s, sub string) bool {
+	if len(sub) == 0 {
+		return true
+	}
+	if len(sub) > len(s) {
+		return false
+	}
+	ls, lsub := lower(s), lower(sub)
+	for i := 0; i+len(lsub) <= len(ls); i++ {
+		if ls[i:i+len(lsub)] == lsub {
+			return true
+		}
+	}
+	return false
+}
+
+func lower(s string) string {
+	b := []byte(s)
+	for i, c := range b {
+		if c >= 'A' && c <= 'Z' {
+			b[i] = c + 32
+		}
+	}
+	return string(b)
+}
--- a/internal/app/idle_test.go
+++ b/internal/app/idle_test.go
@@ -0,0 +1,112 @@
+package app
+
+import (
+	"regexp"
+	"testing"
+)
+
+func mustCompile(t *testing.T, p string) *regexp.Regexp {
+	t.Helper()
+	re, err := regexp.Compile(p)
+	if err != nil {
+		t.Fatalf("regex %q: %v", p, err)
+	}
+	return re
+}
+
+func TestClassifyOutputActivity(t *testing.T) {
+	cfg := &resolvedIdleDetection{strategy: StrategyOutputActivity, idleThresholdMS: 2000}
+
+	cases := []struct {
+		name   string
+		idleMS int64
+		want   IdleState
+	}{
+		{"fresh-spawn no writes", 0, StateWorking},
+		{"recent activity", 500, StateWorking},
+		{"under threshold", 1999, StateWorking},
+		{"at threshold", 2000, StateIdle},
+		{"over threshold", 5000, StateIdle},
+	}
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			got, _ := classify(cfg, false, false, tc.idleMS, 0, "", nil)
+			if got != tc.want {
+				t.Fatalf("got %q want %q", got, tc.want)
+			}
+		})
+	}
+}
+
+func TestClassifyTitleStability(t *testing.T) {
+	cfg := &resolvedIdleDetection{strategy: StrategyOSCTitleStability, idleThresholdMS: 2000}
+	// Title change recent → working.
+	if got, _ := classify(cfg, false, false, 9999, 500, "step 3", nil); got != StateWorking {
+		t.Fatalf("recent title change: got %q", got)
+	}
+	// Title stable past threshold → idle.
+	if got, _ := classify(cfg, false, false, 9999, 5000, "step 3", nil); got != StateIdle {
+		t.Fatalf("stable title: got %q", got)
+	}
+	// No title yet: fall back to output activity.
+	if got, _ := classify(cfg, false, false, 100, 0, "", nil); got != StateWorking {
+		t.Fatalf("no title yet, recent output: got %q", got)
+	}
+	if got, _ := classify(cfg, false, false, 5000, 0, "", nil); got != StateIdle {
+		t.Fatalf("no title yet, output idle: got %q", got)
+	}
+}
+
+func TestClassifyTitleStatus(t *testing.T) {
+	cfg := &resolvedIdleDetection{
+		strategy:        StrategyOSCTitleStatus,
+		idleThresholdMS: 2000,
+		titleStatusMap: map[string]IdleState{
+			"thinking":   StateThinking,
+			"permission": StatePermission,
+			"error":      StateError,
+		},
+	}
+	if got, _ := classify(cfg, false, false, 9999, 500, "Thinking…", nil); got != StateThinking {
+		t.Fatalf("thinking title: got %q", got)
+	}
+	if got, _ := classify(cfg, false, false, 9999, 500, "Waiting for permission", nil); got != StatePermission {
+		t.Fatalf("permission title: got %q", got)
+	}
+	// No match in map → fall back to stability.
+	if got, _ := classify(cfg, false, false, 9999, 5000, "ready", nil); got != StateIdle {
+		t.Fatalf("unmatched title, stable: got %q", got)
+	}
+}
+
+func TestClassifyPromoterRegex(t *testing.T) {
+	cfg := &resolvedIdleDetection{
+		strategy:           StrategyOutputActivity,
+		idleThresholdMS:    2000,
+		permissionRegexes:  []*regexp.Regexp{mustCompile(t, `Approve\?`)},
+		errorRegexes:       []*regexp.Regexp{mustCompile(t, `panic:`)},
+		thinkingRegexes:    []*regexp.Regexp{mustCompile(t, `Thinking`)},
+	}
+	// Permission promoter beats idle.
+	if got, _ := classify(cfg, false, false, 5000, 0, "", []byte("Approve? [y/n]")); got != StatePermission {
+		t.Fatalf("permission promoter: got %q", got)
+	}
+	// Error trumps permission.
+	if got, _ := classify(cfg, false, false, 5000, 0, "", []byte("panic: bad\nApprove?")); got != StateError {
+		t.Fatalf("error promoter beats permission: got %q", got)
+	}
+	// Thinking promoter on idle output.
+	if got, _ := classify(cfg, false, false, 5000, 0, "", []byte("Thinking…")); got != StateThinking {
+		t.Fatalf("thinking promoter: got %q", got)
+	}
+}
+
+func TestClassifyExitTerminal(t *testing.T) {
+	cfg := &resolvedIdleDetection{strategy: StrategyOutputActivity, idleThresholdMS: 2000}
+	if got, _ := classify(cfg, true, true, 0, 0, "", nil); got != StateError {
+		t.Fatalf("non-zero exit: got %q", got)
+	}
+	if got, _ := classify(cfg, true, false, 0, 0, "", nil); got != StateIdle {
+		t.Fatalf("clean exit: got %q", got)
+	}
+}
--- a/internal/app/launch.go
+++ b/internal/app/launch.go
@@ -140,6 +140,7 @@ func (l *Launcher) LaunchAgent(p *preset.Preset, displayName, initialPrompt, par
 		cleanup()
 		return nil, err
 	}
+	c.setIdleDetection(resolveIdleDetection(p.IdleDetection))

 	// Wait for the preset's ready signal, then type the initial prompt.
 	idle := time.Duration(1000) * time.Millisecond
@@ -171,7 +172,7 @@ func (l *Launcher) LaunchCommandPreset(p *preset.Preset, displayName, parentID s
 		env = append(env, k+"="+v)
 	}
 	cols, rows := l.size()
-	return l.sess.Spawn(SpawnSpec{
+	c, err := l.sess.Spawn(SpawnSpec{
 		Kind:      KindCommand,
 		Argv:      p.ResolvedArgv(),
 		Env:       env,
@@ -180,6 +181,11 @@ func (l *Launcher) LaunchCommandPreset(p *preset.Preset, displayName, parentID s
 		WorkDir:   p.WorkingDir,
 		PresetRef: p.Name,
 	}, cols, rows)
+	if err != nil {
+		return nil, err
+	}
+	c.setIdleDetection(resolveIdleDetection(p.IdleDetection))
+	return c, nil
 }

 // LaunchCommandArgv spawns a freeform-argv command entry. Trust gating
--- a/internal/app/session.go
+++ b/internal/app/session.go
@@ -70,6 +70,10 @@ type ChildEventListener interface {
 	// Only the focused-child chunk should reach the screen — the TUI
 	// filters by id.
 	OnPTYOut(childID string, chunk []byte)
+	// OnChildStateChanged fires when the idle-detection classifier
+	// updates a child's IdleState. Listeners use this to repaint the
+	// sidebar badge and to evaluate idle-aware timers.
+	OnChildStateChanged(childID string, state IdleState)
 }

 func NewSession(projectDir, projectKey string) *Session {
@@ -140,6 +144,12 @@ func (s *Session) emitPTYOut(id string, chunk []byte) {
 	}
 }

+func (s *Session) emitStateChanged(id string, state IdleState) {
+	for _, l := range s.listenersSnapshot() {
+		l.OnChildStateChanged(id, state)
+	}
+}
+
 func (s *Session) ChildEnv() []string {
 	env := os.Environ()
 	// Mark patterm-owned PTYs so a recursive `patterm` invocation can
@@ -374,6 +384,15 @@ func (s *Session) pumpChild(c *Child, runID uint64) {
 				if _, werr := em.Write(chunk); werr != nil {
 					logf("emulator.Write(child %s): %v", c.ID, werr)
 				}
+				// OSC 0/2 title updates ride on the same byte stream as
+				// the rest of the output. Polling the emulator after each
+				// Write is cheap (one cgo call returning a borrowed
+				// string) and lets the classifier treat title changes as
+				// an activity signal — even when the title isn't visible
+				// in the rendered grid.
+				if t, terr := em.Title(); terr == nil {
+					c.recordTitle(t)
+				}
 			}
 			c.recordWrite(chunk)
 			s.emitPTYOut(c.ID, chunk)
--- a/internal/app/sidebar.go
+++ b/internal/app/sidebar.go
@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"os"
 	"strings"
+	"time"
 )

 const (
@@ -11,6 +12,24 @@ const (
 	statusRows  = 1
 )

+// formatShortDuration renders a duration as a short, sidebar-friendly
+// suffix: ms under 1s, "12s" under 60s, "3m" otherwise.
+func formatShortDuration(d time.Duration) string {
+	if d <= 0 {
+		return "0s"
+	}
+	if d < time.Second {
+		return fmt.Sprintf("%dms", int(d/time.Millisecond))
+	}
+	if d < time.Minute {
+		return fmt.Sprintf("%ds", int(d/time.Second))
+	}
+	if d < time.Hour {
+		return fmt.Sprintf("%dm", int(d/time.Minute))
+	}
+	return fmt.Sprintf("%dh", int(d/time.Hour))
+}
+
 // drawSidebar paints the right-rail session tree + scratchpad list.
 // SPEC §4: the rail is the active session's child hierarchy on top and
 // the scratchpad list (with preview) on the bottom.
@@ -62,14 +81,56 @@ func (st *uiState) drawSidebar() {
 		write(" " + styleActive + text + styleReset)
 		write(" " + styleBorder + strings.Repeat("─", width-2) + styleReset)
 	}
+	// timerIndicator returns a short " ⏱ 12s" or " ⏸ paused" suffix
+	// when c has a pending or paused timer attached (owns or watches).
+	// Empty string when no timer is in play.
+	timerIndicator := func(c *Child) string {
+		if st.timers == nil {
+			return ""
+		}
+		info := st.timers.activeForChild(c.ID)
+		if info == nil {
+			return ""
+		}
+		if info.Status == timerStatusPaused {
+			return " " + styleDim + "⏸" + styleReset
+		}
+		remaining := ""
+		if info.FiresAtUnixMS > 0 {
+			d := time.Until(time.UnixMilli(info.FiresAtUnixMS))
+			if d < 0 {
+				d = 0
+			}
+			remaining = formatShortDuration(d)
+		}
+		return " " + styleDim + "⏱" + styleReset + " " + styleHint + remaining + styleReset
+	}
 	statusGlyph := func(c *Child, focused bool) string {
 		if c.Status() != StatusRunning {
 			return styleDim + "○" + styleReset
 		}
+		// Idle-detection states paint over the plain running glyph so
+		// the rail communicates "running but waiting on you" vs "running
+		// and busy" at a glance. Focused entries always use the accent
+		// colour so the user's selection stays visible.
+		style := styleHint
 		if focused {
-			return styleAccent + "●" + styleReset
+			style = styleAccent
+		}
+		switch c.IdleState() {
+		case StateError:
+			return styleError + "✕" + styleReset
+		case StatePermission:
+			return styleAccent + "?" + styleReset
+		case StateThinking:
+			return style + "◐" + styleReset
+		case StateIdle:
+			return style + "○" + styleReset
+		case StateWorking:
+			return style + "●" + styleReset
+		default:
+			return style + "●" + styleReset
 		}
-		return styleHint + "●" + styleReset
 	}

 	// Processes section — top-level command/terminal processes,
@@ -92,9 +153,9 @@ func (st *uiState) drawSidebar() {
 		var line string
 		if focused {
 			line = " " + styleAccent + "▎" + styleReset + " " + glyph + " " +
-				styleBold + c.DisplayName() + styleReset + marker
+				styleBold + c.DisplayName() + styleReset + marker + timerIndicator(c)
 		} else {
-			line = "   " + glyph + " " + styleHint + c.DisplayName() + styleReset + marker
+			line = "   " + glyph + " " + styleHint + c.DisplayName() + styleReset + marker + timerIndicator(c)
 		}
 		write(line)
 	}
@@ -124,9 +185,9 @@ func (st *uiState) drawSidebar() {
 		var line string
 		if focused {
 			line = " " + styleAccent + "▎" + styleReset + " " + indent + glyph + " " +
-				styleBold + c.DisplayName() + styleReset
+				styleBold + c.DisplayName() + styleReset + timerIndicator(c)
 		} else {
-			line = "   " + indent + glyph + " " + styleHint + c.DisplayName() + styleReset
+			line = "   " + indent + glyph + " " + styleHint + c.DisplayName() + styleReset + timerIndicator(c)
 		}
 		write(line)
 	}
--- a/internal/app/style.go
+++ b/internal/app/style.go
@@ -11,4 +11,5 @@ const (
 	styleAccent = "\x1b[38;5;75m"
 	styleHint   = "\x1b[38;5;244m"
 	styleActive = "\x1b[1;38;5;253m"
+	styleError  = "\x1b[38;5;203m"
 )
--- a/internal/app/timers.go
+++ b/internal/app/timers.go
@@ -0,0 +1,488 @@
+package app
+
+import (
+	"fmt"
+	"sync"
+	"time"
+
+	"github.com/hjbdev/patterm/internal/mcp"
+)
+
+// pendingTimerKind picks the firing rule.
+type pendingTimerKind string
+
+const (
+	timerKindDelay    pendingTimerKind = "delay"
+	timerKindIdleAny  pendingTimerKind = "idle_any"
+	timerKindIdleAll  pendingTimerKind = "idle_all"
+)
+
+const (
+	timerStatusPending  = "pending"
+	timerStatusPaused   = "paused"
+	timerStatusFired    = "fired"
+	timerStatusCanceled = "canceled"
+)
+
+// pendingTimer is one live timer tracked by the manager. The body is
+// delivered verbatim to the owning child's PTY as a fresh user turn
+// when the timer fires.
+//
+// Locking: every field is protected by timerManager.mu. The runtime
+// time.Timer (rt) is started outside the lock so the firing goroutine
+// can take the lock without deadlocking.
+type pendingTimer struct {
+	id      string
+	label   string
+	body    string
+	ownerID string
+	kind    pendingTimerKind
+	status  string
+
+	watched    []string
+	idleBaseline map[string]bool // for idle_any: ids already idle at registration (excluded from satisfaction)
+
+	firesAt          time.Time
+	pausedRemaining  time.Duration
+	pausedWasMaxWait bool // for idle_*: true if the active timer was max-wait, not delay
+
+	rt *time.Timer // delay timer or idle_* max-wait fallback
+}
+
+// timerManager owns the pending-timer registry. Mutating operations
+// (set, cancel, pause, resume) all serialise through mu; fire callbacks
+// from the runtime timer also take mu to safely transition state.
+type timerManager struct {
+	sess *Session
+
+	mu      sync.Mutex
+	nextID  int
+	timers  map[string]*pendingTimer
+
+	// fireFn is the callback used to deliver the body to the owning
+	// process. Decoupled so tests can substitute a recorder. Defaults
+	// to caller.InjectAsOrchestrator + "\r".
+	fireFn func(owner *Child, body, label string)
+}
+
+func newTimerManager(sess *Session) *timerManager {
+	m := &timerManager{
+		sess:   sess,
+		timers: make(map[string]*pendingTimer),
+	}
+	m.fireFn = defaultFireFn
+	return m
+}
+
+func defaultFireFn(owner *Child, body, label string) {
+	if owner == nil || !owner.IsLive() {
+		return
+	}
+	// Solo delivers body verbatim. patterm's PTY-injection path expects
+	// a trailing CR so the line submits in TUI agents (Claude/Codex/
+	// OpenCode all paste-detect). A bare body without CR sits in the
+	// input buffer; that's almost never what the caller wants.
+	if body == "" {
+		body = fmt.Sprintf("[system] Your timer [%s] has completed.", label)
+	}
+	_ = owner.InjectAsOrchestrator([]byte(body + "\r"))
+}
+
+func (m *timerManager) mintID() string {
+	m.nextID++
+	return fmt.Sprintf("t%d", m.nextID)
+}
+
+// TimerSet schedules a delay timer. Returns immediately; the body is
+// delivered to the owning child when the timer fires.
+func (m *timerManager) TimerSet(ownerID string, body, label string, seconds float64) (string, error) {
+	owner := m.sess.FindChild(ownerID)
+	if owner == nil {
+		return "", mcp.Errorf(mcp.ErrorKindNotFound, "caller %q not known to patterm", ownerID)
+	}
+	if seconds < 0 {
+		return "", mcp.Errorf(mcp.ErrorKindInvalidArgs, "timer_set: seconds must be ≥ 0")
+	}
+	d := time.Duration(seconds * float64(time.Second))
+	m.mu.Lock()
+	id := m.mintID()
+	if label == "" {
+		label = id
+	}
+	t := &pendingTimer{
+		id:      id,
+		label:   label,
+		body:    body,
+		ownerID: ownerID,
+		kind:    timerKindDelay,
+		status:  timerStatusPending,
+		firesAt: time.Now().Add(d),
+	}
+	m.timers[id] = t
+	m.mu.Unlock()
+	t.rt = time.AfterFunc(d, func() { m.fireDelay(id) })
+	return id, nil
+}
+
+func (m *timerManager) fireDelay(id string) {
+	m.mu.Lock()
+	t, ok := m.timers[id]
+	if !ok || t.status != timerStatusPending {
+		m.mu.Unlock()
+		return
+	}
+	t.status = timerStatusFired
+	owner := m.sess.FindChild(t.ownerID)
+	body, label := t.body, t.label
+	m.mu.Unlock()
+	m.fireFn(owner, body, label)
+}
+
+// TimerFireWhenIdleAny schedules an idle-any timer. Children already
+// idle at registration are excluded from satisfaction — only a
+// transition into idle by a still-active watched child fires the
+// timer. Max-wait, when positive, acts as a fallback fire deadline.
+func (m *timerManager) TimerFireWhenIdleAny(ownerID, body, label string, watched []string, maxWait float64) (mcp.TimerFireWhenIdleResponse, error) {
+	return m.registerIdleTimer(timerKindIdleAny, ownerID, body, label, watched, maxWait)
+}
+
+// TimerFireWhenIdleAll schedules an idle-all timer. Already-idle
+// children count as satisfied; if every watched child is already idle
+// at registration time the response is "already_satisfied" with no
+// timer created.
+func (m *timerManager) TimerFireWhenIdleAll(ownerID, body, label string, watched []string, maxWait float64) (mcp.TimerFireWhenIdleResponse, error) {
+	return m.registerIdleTimer(timerKindIdleAll, ownerID, body, label, watched, maxWait)
+}
+
+func (m *timerManager) registerIdleTimer(kind pendingTimerKind, ownerID, body, label string, watched []string, maxWait float64) (mcp.TimerFireWhenIdleResponse, error) {
+	if m.sess.FindChild(ownerID) == nil {
+		return mcp.TimerFireWhenIdleResponse{}, mcp.Errorf(mcp.ErrorKindNotFound, "caller %q not known to patterm", ownerID)
+	}
+	if len(watched) == 0 {
+		return mcp.TimerFireWhenIdleResponse{}, mcp.Errorf(mcp.ErrorKindInvalidArgs, "watched must contain at least one process_id")
+	}
+	if maxWait < 0 {
+		return mcp.TimerFireWhenIdleResponse{}, mcp.Errorf(mcp.ErrorKindInvalidArgs, "max_wait_seconds must be ≥ 0")
+	}
+	// Validate watched ids and compute the idle baseline up front.
+	already := make([]string, 0)
+	waiting := make([]string, 0)
+	baseline := make(map[string]bool, len(watched))
+	for _, id := range watched {
+		c := m.sess.FindChild(id)
+		if c == nil {
+			return mcp.TimerFireWhenIdleResponse{}, mcp.Errorf(mcp.ErrorKindNotFound, "no such process %q in watched", id)
+		}
+		if isIdleState(c.IdleState()) {
+			already = append(already, id)
+			baseline[id] = true
+		} else {
+			waiting = append(waiting, id)
+		}
+	}
+	resp := mcp.TimerFireWhenIdleResponse{AlreadyIdle: already, WaitingOn: waiting}
+
+	// idle_all: if all watched are already idle, satisfy synchronously
+	// — Solo semantics; no pending timer is created.
+	if kind == timerKindIdleAll && len(waiting) == 0 {
+		resp.Status = "already_satisfied"
+		owner := m.sess.FindChild(ownerID)
+		go m.fireFn(owner, body, label)
+		return resp, nil
+	}
+
+	m.mu.Lock()
+	id := m.mintID()
+	if label == "" {
+		label = id
+	}
+	t := &pendingTimer{
+		id:           id,
+		label:        label,
+		body:         body,
+		ownerID:      ownerID,
+		kind:         kind,
+		status:       timerStatusPending,
+		watched:      append([]string(nil), watched...),
+		idleBaseline: baseline,
+	}
+	if maxWait > 0 {
+		d := time.Duration(maxWait * float64(time.Second))
+		t.firesAt = time.Now().Add(d)
+		t.rt = time.AfterFunc(d, func() { m.fireIdleMaxWait(id) })
+	}
+	m.timers[id] = t
+	m.mu.Unlock()
+	resp.ID = id
+	resp.Status = "pending"
+	return resp, nil
+}
+
+func (m *timerManager) fireIdleMaxWait(id string) {
+	m.mu.Lock()
+	t, ok := m.timers[id]
+	if !ok || t.status != timerStatusPending {
+		m.mu.Unlock()
+		return
+	}
+	t.status = timerStatusFired
+	owner := m.sess.FindChild(t.ownerID)
+	body, label := t.body, t.label
+	m.mu.Unlock()
+	m.fireFn(owner, body, label)
+}
+
+// onChildStateChanged evaluates every pending idle_any / idle_all
+// timer whenever any child's IdleState flips. Cheap — there are few
+// pending timers and the per-tick check is just a map lookup + a slice
+// scan.
+func (m *timerManager) onChildStateChanged(childID string, state IdleState) {
+	if !isIdleState(state) {
+		return
+	}
+	m.mu.Lock()
+	type firing struct {
+		owner *Child
+		body  string
+		label string
+	}
+	var fires []firing
+	for _, t := range m.timers {
+		if t.status != timerStatusPending {
+			continue
+		}
+		if !contains(t.watched, childID) {
+			continue
+		}
+		switch t.kind {
+		case timerKindIdleAny:
+			if t.idleBaseline[childID] {
+				continue // already idle at registration; excluded
+			}
+			t.status = timerStatusFired
+			if t.rt != nil {
+				t.rt.Stop()
+			}
+			fires = append(fires, firing{
+				owner: m.sess.FindChild(t.ownerID),
+				body:  t.body,
+				label: t.label,
+			})
+		case timerKindIdleAll:
+			if m.allWatchedIdleLocked(t) {
+				t.status = timerStatusFired
+				if t.rt != nil {
+					t.rt.Stop()
+				}
+				fires = append(fires, firing{
+					owner: m.sess.FindChild(t.ownerID),
+					body:  t.body,
+					label: t.label,
+				})
+			}
+		}
+	}
+	m.mu.Unlock()
+	for _, f := range fires {
+		m.fireFn(f.owner, f.body, f.label)
+	}
+}
+
+// allWatchedIdleLocked reports whether every watched child is now
+// idle. Called with m.mu held — uses live Child.IdleState() under the
+// child's own atomic, not under m.mu.
+func (m *timerManager) allWatchedIdleLocked(t *pendingTimer) bool {
+	for _, id := range t.watched {
+		c := m.sess.FindChild(id)
+		if c == nil {
+			continue // disappeared; treat as satisfied so we don't hang
+		}
+		if !isIdleState(c.IdleState()) {
+			return false
+		}
+	}
+	return true
+}
+
+// TimerCancel removes a pending or paused timer owned by ownerID.
+func (m *timerManager) TimerCancel(ownerID, id string) error {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	t, ok := m.timers[id]
+	if !ok {
+		return mcp.Errorf(mcp.ErrorKindNotFound, "no such timer %q", id)
+	}
+	// Empty ownerID = top-level orchestrator caller (e.g. a non-agent
+	// MCP client); allow it to manage every timer in the session.
+	// Otherwise the caller's own id must match the timer's owner.
+	if ownerID != "" && t.ownerID != ownerID {
+		return mcp.Errorf(mcp.ErrorKindRoleForbidden, "timer %q is not owned by caller", id)
+	}
+	if t.status == timerStatusFired || t.status == timerStatusCanceled {
+		// Cancelling a fired/cancelled timer is idempotent.
+		return nil
+	}
+	if t.rt != nil {
+		t.rt.Stop()
+		t.rt = nil
+	}
+	t.status = timerStatusCanceled
+	return nil
+}
+
+// TimerPause stops the delay clock (or detaches the idle watch) but
+// keeps the timer in the registry.
+func (m *timerManager) TimerPause(ownerID, id string) error {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	t, ok := m.timers[id]
+	if !ok {
+		return mcp.Errorf(mcp.ErrorKindNotFound, "no such timer %q", id)
+	}
+	// Empty ownerID = top-level orchestrator caller (e.g. a non-agent
+	// MCP client); allow it to manage every timer in the session.
+	// Otherwise the caller's own id must match the timer's owner.
+	if ownerID != "" && t.ownerID != ownerID {
+		return mcp.Errorf(mcp.ErrorKindRoleForbidden, "timer %q is not owned by caller", id)
+	}
+	if t.status != timerStatusPending {
+		return mcp.Errorf(mcp.ErrorKindInvalidArgs, "timer %q is not pending", id)
+	}
+	if t.rt != nil {
+		t.pausedRemaining = time.Until(t.firesAt)
+		if t.pausedRemaining < 0 {
+			t.pausedRemaining = 0
+		}
+		t.rt.Stop()
+		t.rt = nil
+		// For idle_* timers, only the max-wait timer rides on rt — the
+		// idle-evaluation path lives in onChildStateChanged. Mark the
+		// pause so resume rearms the right thing.
+		t.pausedWasMaxWait = t.kind != timerKindDelay
+	}
+	t.status = timerStatusPaused
+	return nil
+}
+
+// TimerResume re-arms a paused timer. For delay timers the remaining
+// duration is restored; idle-* timers re-attach to the state-change
+// watch list, and any remaining max-wait clock resumes.
+func (m *timerManager) TimerResume(ownerID, id string) error {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	t, ok := m.timers[id]
+	if !ok {
+		return mcp.Errorf(mcp.ErrorKindNotFound, "no such timer %q", id)
+	}
+	// Empty ownerID = top-level orchestrator caller (e.g. a non-agent
+	// MCP client); allow it to manage every timer in the session.
+	// Otherwise the caller's own id must match the timer's owner.
+	if ownerID != "" && t.ownerID != ownerID {
+		return mcp.Errorf(mcp.ErrorKindRoleForbidden, "timer %q is not owned by caller", id)
+	}
+	if t.status != timerStatusPaused {
+		return mcp.Errorf(mcp.ErrorKindInvalidArgs, "timer %q is not paused", id)
+	}
+	t.status = timerStatusPending
+	if t.pausedRemaining > 0 {
+		t.firesAt = time.Now().Add(t.pausedRemaining)
+		switch t.kind {
+		case timerKindDelay:
+			localID := id
+			t.rt = time.AfterFunc(t.pausedRemaining, func() { m.fireDelay(localID) })
+		default:
+			localID := id
+			t.rt = time.AfterFunc(t.pausedRemaining, func() { m.fireIdleMaxWait(localID) })
+		}
+		t.pausedRemaining = 0
+		t.pausedWasMaxWait = false
+	}
+	return nil
+}
+
+// TimerList returns timers owned by ownerID, oldest-first. An empty
+// ownerID lists every active timer — the top-level orchestrator view.
+func (m *timerManager) TimerList(ownerID string) []mcp.TimerInfo {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	out := make([]mcp.TimerInfo, 0)
+	for _, t := range m.timers {
+		if ownerID != "" && t.ownerID != ownerID {
+			continue
+		}
+		if t.status != timerStatusPending && t.status != timerStatusPaused {
+			continue
+		}
+		info := mcp.TimerInfo{
+			ID:         t.id,
+			Label:      t.label,
+			Body:       t.body,
+			Kind:       string(t.kind),
+			Status:     t.status,
+			OwnerID:    t.ownerID,
+			WatchedIDs: append([]string(nil), t.watched...),
+		}
+		if t.status == timerStatusPending && !t.firesAt.IsZero() {
+			info.FiresAtUnixMS = t.firesAt.UnixMilli()
+		}
+		if t.status == timerStatusPaused && t.pausedRemaining > 0 {
+			info.PausedRemainingMS = t.pausedRemaining.Milliseconds()
+		}
+		out = append(out, info)
+	}
+	return out
+}
+
+// activeForChild returns the nearest pending or paused timer attached
+// to child id (either owned by it or watching it). Used by the sidebar
+// for the "⏱ 12s" indicator. nil when none.
+func (m *timerManager) activeForChild(id string) *mcp.TimerInfo {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	var best *pendingTimer
+	for _, t := range m.timers {
+		if t.status != timerStatusPending && t.status != timerStatusPaused {
+			continue
+		}
+		if t.ownerID != id && !contains(t.watched, id) {
+			continue
+		}
+		if best == nil {
+			best = t
+			continue
+		}
+		if t.firesAt.Before(best.firesAt) && !t.firesAt.IsZero() {
+			best = t
+		}
+	}
+	if best == nil {
+		return nil
+	}
+	info := mcp.TimerInfo{
+		ID:      best.id,
+		Label:   best.label,
+		Kind:    string(best.kind),
+		Status:  best.status,
+		OwnerID: best.ownerID,
+	}
+	if best.status == timerStatusPending && !best.firesAt.IsZero() {
+		info.FiresAtUnixMS = best.firesAt.UnixMilli()
+	}
+	if best.status == timerStatusPaused {
+		info.PausedRemainingMS = best.pausedRemaining.Milliseconds()
+	}
+	return &info
+}
+
+func isIdleState(s IdleState) bool {
+	return s == StateIdle
+}
+
+func contains(haystack []string, needle string) bool {
+	for _, h := range haystack {
+		if h == needle {
+			return true
+		}
+	}
+	return false
+}
--- a/internal/app/timers_test.go
+++ b/internal/app/timers_test.go
@@ -0,0 +1,223 @@
+package app
+
+import (
+	"sync"
+	"testing"
+	"time"
+)
+
+// recorderFire collects timer firings without touching a PTY. Lets the
+// timer manager run end-to-end logic in unit tests.
+type recorderFire struct {
+	mu    sync.Mutex
+	fires []recordedFire
+}
+
+type recordedFire struct {
+	OwnerID string
+	Body    string
+	Label   string
+}
+
+func (r *recorderFire) fn(owner *Child, body, label string) {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	id := ""
+	if owner != nil {
+		id = owner.ID
+	}
+	r.fires = append(r.fires, recordedFire{OwnerID: id, Body: body, Label: label})
+}
+
+func (r *recorderFire) snapshot() []recordedFire {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	out := make([]recordedFire, len(r.fires))
+	copy(out, r.fires)
+	return out
+}
+
+// fakeChild constructs a Child shell suitable for timer-manager tests.
+// Doesn't open a PTY — fireFn is overridden so InjectAsOrchestrator is
+// never reached.
+func fakeChild(id string) *Child {
+	c := newChildEntry(id, id, KindAgent, []string{"echo"}, nil, "", "", "")
+	running := StatusRunning
+	c.status.Store(&running)
+	return c
+}
+
+// addChild bypasses Spawn (no PTY needed) so the manager can find the
+// child by id and read its IdleState.
+func addChild(s *Session, c *Child) {
+	s.mu.Lock()
+	s.children[c.ID] = c
+	s.order = append(s.order, c.ID)
+	s.mu.Unlock()
+}
+
+func newTestManager(t *testing.T) (*Session, *timerManager, *recorderFire) {
+	t.Helper()
+	sess := NewSession(t.TempDir(), "test")
+	mgr := newTimerManager(sess)
+	rec := &recorderFire{}
+	mgr.fireFn = rec.fn
+	return sess, mgr, rec
+}
+
+func TestTimerSetDelivers(t *testing.T) {
+	sess, mgr, rec := newTestManager(t)
+	c := fakeChild("p_owner")
+	addChild(sess, c)
+	id, err := mgr.TimerSet("p_owner", "wake up", "test", 0.05)
+	if err != nil {
+		t.Fatalf("TimerSet: %v", err)
+	}
+	if id == "" {
+		t.Fatal("empty timer id")
+	}
+	deadline := time.Now().Add(time.Second)
+	for time.Now().Before(deadline) {
+		if len(rec.snapshot()) > 0 {
+			break
+		}
+		time.Sleep(10 * time.Millisecond)
+	}
+	got := rec.snapshot()
+	if len(got) != 1 {
+		t.Fatalf("got %d fires, want 1", len(got))
+	}
+	if got[0].Body != "wake up" || got[0].OwnerID != "p_owner" {
+		t.Fatalf("unexpected fire: %+v", got[0])
+	}
+}
+
+func TestTimerIdleAllAlreadySatisfied(t *testing.T) {
+	sess, mgr, rec := newTestManager(t)
+	owner := fakeChild("p_owner")
+	a := fakeChild("p_a")
+	b := fakeChild("p_b")
+	addChild(sess, owner)
+	addChild(sess, a)
+	addChild(sess, b)
+	idle := StateIdle
+	a.idleState.Store(&idle)
+	b.idleState.Store(&idle)
+	resp, err := mgr.TimerFireWhenIdleAll("p_owner", "all done", "", []string{"p_a", "p_b"}, 0)
+	if err != nil {
+		t.Fatalf("TimerFireWhenIdleAll: %v", err)
+	}
+	if resp.Status != "already_satisfied" {
+		t.Fatalf("status: got %q want already_satisfied", resp.Status)
+	}
+	// fire is dispatched on a goroutine; wait briefly.
+	time.Sleep(50 * time.Millisecond)
+	got := rec.snapshot()
+	if len(got) != 1 || got[0].Body != "all done" {
+		t.Fatalf("fires: %+v", got)
+	}
+}
+
+func TestTimerIdleAnyFiresOnTransition(t *testing.T) {
+	sess, mgr, rec := newTestManager(t)
+	owner := fakeChild("p_owner")
+	a := fakeChild("p_a")
+	addChild(sess, owner)
+	addChild(sess, a)
+	// p_a starts busy.
+	working := StateWorking
+	a.idleState.Store(&working)
+	resp, err := mgr.TimerFireWhenIdleAny("p_owner", "one done", "", []string{"p_a"}, 0)
+	if err != nil {
+		t.Fatalf("TimerFireWhenIdleAny: %v", err)
+	}
+	if resp.Status != "pending" {
+		t.Fatalf("status: got %q want pending", resp.Status)
+	}
+	// Flip a into idle and deliver the state-change event.
+	idle := StateIdle
+	a.idleState.Store(&idle)
+	mgr.onChildStateChanged("p_a", StateIdle)
+	got := rec.snapshot()
+	if len(got) != 1 || got[0].Body != "one done" {
+		t.Fatalf("fires: %+v", got)
+	}
+}
+
+func TestTimerIdleAnyExcludesBaseline(t *testing.T) {
+	sess, mgr, rec := newTestManager(t)
+	owner := fakeChild("p_owner")
+	a := fakeChild("p_a")
+	addChild(sess, owner)
+	addChild(sess, a)
+	idle := StateIdle
+	a.idleState.Store(&idle)
+	resp, err := mgr.TimerFireWhenIdleAny("p_owner", "one done", "", []string{"p_a"}, 0)
+	if err != nil {
+		t.Fatalf("TimerFireWhenIdleAny: %v", err)
+	}
+	if resp.Status != "pending" {
+		t.Fatalf("status: got %q want pending", resp.Status)
+	}
+	// Send a redundant idle transition for p_a; should NOT fire because
+	// p_a was idle at registration.
+	mgr.onChildStateChanged("p_a", StateIdle)
+	if got := rec.snapshot(); len(got) != 0 {
+		t.Fatalf("unexpected fires: %+v", got)
+	}
+}
+
+func TestTimerCancelPauseResume(t *testing.T) {
+	sess, mgr, rec := newTestManager(t)
+	owner := fakeChild("p_owner")
+	addChild(sess, owner)
+
+	// Cancel before fire.
+	id, _ := mgr.TimerSet("p_owner", "x", "", 0.2)
+	if err := mgr.TimerCancel("p_owner", id); err != nil {
+		t.Fatalf("Cancel: %v", err)
+	}
+	time.Sleep(300 * time.Millisecond)
+	if got := rec.snapshot(); len(got) != 0 {
+		t.Fatalf("cancel didn't stop fire: %+v", got)
+	}
+
+	// Pause then resume → fire after resume.
+	id2, _ := mgr.TimerSet("p_owner", "y", "", 0.2)
+	time.Sleep(50 * time.Millisecond)
+	if err := mgr.TimerPause("p_owner", id2); err != nil {
+		t.Fatalf("Pause: %v", err)
+	}
+	time.Sleep(300 * time.Millisecond) // would have fired by now if not paused
+	if got := rec.snapshot(); len(got) != 0 {
+		t.Fatalf("paused timer fired: %+v", got)
+	}
+	if err := mgr.TimerResume("p_owner", id2); err != nil {
+		t.Fatalf("Resume: %v", err)
+	}
+	deadline := time.Now().Add(time.Second)
+	for time.Now().Before(deadline) {
+		if len(rec.snapshot()) > 0 {
+			break
+		}
+		time.Sleep(20 * time.Millisecond)
+	}
+	if got := rec.snapshot(); len(got) != 1 || got[0].Body != "y" {
+		t.Fatalf("resume fire: %+v", got)
+	}
+}
+
+func TestTimerOwnershipEnforced(t *testing.T) {
+	sess, mgr, _ := newTestManager(t)
+	a := fakeChild("p_a")
+	b := fakeChild("p_b")
+	addChild(sess, a)
+	addChild(sess, b)
+	id, _ := mgr.TimerSet("p_a", "hi", "", 60)
+	if err := mgr.TimerCancel("p_b", id); err == nil {
+		t.Fatal("expected ownership error from foreign cancel")
+	}
+	if err := mgr.TimerPause("p_b", id); err == nil {
+		t.Fatal("expected ownership error from foreign pause")
+	}
+}