mavweb: add rule trace page at /trace

New template showing the most recent tick's rule evaluation results
with color-coded table, expandable gate detail panels, nav links
to dash and history. Uses the TickTrace IPC method from #15.

SESSION-05-07-2026.md

@@ -63,7 +63,7 @@ Notes:
 | 12 | **Recurring reminders** — cron+next_fire_ts cols, RescheduleReminder, dispatcher logic | 1eca17f | done |
 | 13 | **Capability model** — `scope` column on tools table, migration, UI, tests | 6b80fd0 | done |
 | 14 | **Notification batching/digest mode** — in-memory queue, configurable window/max_items/severity_ceiling | 354990f | done |
-| 15 | **Rule trace / explanation engine** — `why` query: "why did/didn't you nudge me?" Reads predicate eval log. New `/trace` page or CLI query | — | pending |
+| 15 | **Rule trace/explanation engine** — ExplainTick/ExplainGate, TickTrace IPC, daemon cache | 2689db1 | done |
 | 16 | **Backup/restore automation** — scripts/maven-backup.sh with backup/restore/verify/list | 3f09cdb | done |
 
 Notes:
@@ -79,7 +79,7 @@ Notes:
 |---|------|--------|--------|
 | 17 | **In-process auth gate for /tools** — local PasskeySession check on POST, returns 403 if unasserted | 5afff00 | done |
 | 18 | **Digest / notification history UI** — section on `/dash` showing batched notifications | — | pending |
-| 19 | **Rule trace page** — new `/trace` route showing predicate eval results per rule per tick | — | pending |
+| 19 | **Rule trace page** — new /trace route showing predicate eval results per rule per tick | — | pending (depends on #15 backend, can now build)
 | 20 | **Command history page** — new `/history` route showing recent facts/commands | f8ba396 | done |
 | 21 | **PWA icons** — SVG icon + manifest.json icons array | 00a3bba | done |
 | 22 | **Language unification** — bilingual cheatsheet with RU/EN toggle in nav + ?lang= param | c225ba3 | done |

cmd/mavweb/dash.html

@@ -10,7 +10,7 @@
  .updated{color:#666;font-size:.85rem;margin-top:-.5rem;margin-bottom:1rem}
  nav a{color:#8cf;margin-right:1rem;font-size:.85rem}
 </style>
-<nav><a href=/history>history</a></nav>
+<nav><a href=/history>history</a> <a href=/trace>trace</a></nav>
 <h2>presence</h2>
 <p><span class={{.Presence.Bucket}}>{{.Presence.Bucket}}</span> — score {{printf "%.2f" .Presence.Score}} ({{ago .Presence.Updated}})</p>
 <div class=updated>обновляется каждые 10с</div>

cmd/mavweb/handlers_test.go

@@ -55,6 +55,10 @@ type fakeCore struct {
 	// for handleHistory tests
 	historyFacts []ipc.Fact
 	historyErr   error
+
+	// for handleTrace tests
+	tickTrace ipc.TickTrace
+	traceErr  error
 }
 
 func (f *fakeCore) EnableTool(_ context.Context, name string, cmd []string, destructive bool, scope string, _ time.Time) error {
@@ -131,6 +135,13 @@ func (f *fakeCore) RevertFact(_ context.Context, _ string) (int64, error) {
 	return f.revertNewID, nil
 }
 
+func (f *fakeCore) TickTrace(_ context.Context) (ipc.TickTrace, error) {
+	if f.traceErr != nil {
+		return ipc.TickTrace{}, f.traceErr
+	}
+	return f.tickTrace, nil
+}
+
 // --- GET ---
 
 func TestHandleTools_GET_RendersAndEscapes(t *testing.T) {
@@ -578,6 +589,88 @@ func TestHandleHistory(t *testing.T) {
 	})
 }
 
+// --- handleTrace ---
+
+func TestHandleTrace(t *testing.T) {
+	t.Parallel()
+
+	t.Run("nil core returns 503", func(t *testing.T) {
+		rr := httptest.NewRecorder()
+		handleTrace(rr, httptest.NewRequest(http.MethodGet, "/trace", nil), nil)
+		if rr.Code != http.StatusServiceUnavailable {
+			t.Errorf("status = %d, want 503", rr.Code)
+		}
+	})
+
+	t.Run("core TickTrace error returns 502", func(t *testing.T) {
+		core := &fakeCore{traceErr: ipc.ErrNoFact}
+		rr := httptest.NewRecorder()
+		handleTrace(rr, httptest.NewRequest(http.MethodGet, "/trace", nil), core)
+		if rr.Code != http.StatusBadGateway {
+			t.Errorf("status = %d, want 502", rr.Code)
+		}
+	})
+
+	t.Run("renders template with trace data", func(t *testing.T) {
+		now := time.Date(2025, 6, 1, 12, 0, 0, 0, time.UTC)
+		snooze := time.Date(2025, 6, 1, 13, 0, 0, 0, time.UTC)
+		core := &fakeCore{
+			tickTrace: ipc.TickTrace{
+				Now:    now,
+				Winner: "win-rule",
+				Rules: []ipc.RuleTrace{
+					{
+						RuleName:        "win-rule",
+						Severity:        5,
+						PredicateResult: true,
+						GateResult:      true,
+						GateDetail:      ipc.GateDetail{Presence: "present"},
+						WasSelected:     true,
+					},
+					{
+						RuleName:        "lose-rule",
+						Severity:        3,
+						PredicateResult: true,
+						GateResult:      false,
+						GateBlockedBy:   "quiet_hours",
+						GateDetail: ipc.GateDetail{
+							QuietHours: true,
+							Presence:   "away",
+							SnoozeUntil: &snooze,
+						},
+						WasSelected: false,
+						LostTo:      "win-rule",
+					},
+				},
+			},
+		}
+		rr := httptest.NewRecorder()
+		handleTrace(rr, httptest.NewRequest(http.MethodGet, "/trace", nil), core)
+		if rr.Code != http.StatusOK {
+			t.Fatalf("status = %d, want 200; body=%s", rr.Code, rr.Body.String())
+		}
+		body := rr.Body.String()
+		if !strings.Contains(body, "win-rule") {
+			t.Error("rendered output missing winning rule name")
+		}
+		if !strings.Contains(body, "lose-rule") {
+			t.Error("rendered output missing losing rule name")
+		}
+		if !strings.Contains(body, "quiet_hours") {
+			t.Error("rendered output missing gate blocked by")
+		}
+		if !strings.Contains(body, "5") {
+			t.Error("rendered output missing severity")
+		}
+		if !strings.Contains(body, "3") {
+			t.Error("rendered output missing severity for second rule")
+		}
+		if strings.Contains(body, "nothing fired") {
+			t.Error("rendered 'nothing fired' but a winner was set")
+		}
+	})
+}
+
 // --- handleRevert ---
 
 func TestHandleRevert(t *testing.T) {

cmd/mavweb/main.go

@@ -48,6 +48,9 @@ var dashHTML string
 //go:embed history.html
 var historyHTML string
 
+//go:embed trace.html
+var traceHTML string
+
 // dashTmpl — the monitoring read surface, server-rendered from dash.html (no JS,
 // no client fetch); meta-refresh keeps it live. html/template escapes the user
 // text in facts/nudges. Read-only: browses the append-only store via CoreAPI,
@@ -133,6 +136,9 @@ func main() {
 	mux.HandleFunc("/history", func(w http.ResponseWriter, r *http.Request) {
 		handleHistory(w, r, core)
 	})
+	mux.HandleFunc("/trace", func(w http.ResponseWriter, r *http.Request) {
+		handleTrace(w, r, core)
+	})
 	mux.HandleFunc("/api/revert", func(w http.ResponseWriter, r *http.Request) {
 		handleRevert(w, r, core)
 	})
@@ -372,6 +378,22 @@ input[type=text]{width:22rem}code{background:#f4f4f4;padding:.1rem .3rem}
 
 var historyTmpl = template.Must(template.New("history").Parse(historyHTML))
 
+var traceTmpl = template.Must(template.New("trace").Funcs(template.FuncMap{
+	"ago": func(t time.Time) string {
+		if t.IsZero() {
+			return "never"
+		}
+		return time.Since(t).Round(time.Second).String() + " ago"
+	},
+	"fmtTime": func(t *time.Time) string {
+		if t == nil || t.IsZero() {
+			return "—"
+		}
+		return t.Format("15:04:05")
+	},
+	"join": strings.Join,
+}).Parse(traceHTML))
+
 func handleHistory(w http.ResponseWriter, r *http.Request, core ipc.CoreAPI) {
 	if core == nil {
 		http.Error(w, "history disabled (no -core)", http.StatusServiceUnavailable)
@@ -392,6 +414,24 @@ func handleHistory(w http.ResponseWriter, r *http.Request, core ipc.CoreAPI) {
 	}
 }
 
+func handleTrace(w http.ResponseWriter, r *http.Request, core ipc.CoreAPI) {
+	if core == nil {
+		http.Error(w, "trace disabled (no -core)", http.StatusServiceUnavailable)
+		return
+	}
+	ctx := r.Context()
+	trace, err := core.TickTrace(ctx)
+	if err != nil {
+		log.Printf("trace: %v", err)
+		http.Error(w, "core read failed", http.StatusBadGateway)
+		return
+	}
+	w.Header().Set("Content-Type", "text/html; charset=utf-8")
+	if err := traceTmpl.Execute(w, trace); err != nil {
+		log.Printf("trace render: %v", err)
+	}
+}
+
 func handleRevert(w http.ResponseWriter, r *http.Request, core ipc.CoreAPI) {
 	if r.Method != http.MethodPost {
 		http.Error(w, "POST only", http.StatusMethodNotAllowed)

cmd/mavweb/trace.html

@@ -0,0 +1,37 @@
+<!doctype html><meta charset=utf-8>
+<title>maven · rule trace</title>
+<style>
+ body{font:14px monospace;background:#111;color:#ddd;margin:1rem}
+ h2{color:#8cf;margin:1.2rem 0 .3rem}
+ table{border-collapse:collapse;width:100%}
+ td,th{border-bottom:1px solid #333;padding:.2rem .5rem;text-align:left;vertical-align:top}
+ .green{color:#6c6}.red{color:#f66}.gray{color:#888}
+ .updated{color:#666;font-size:.85rem}
+ nav a{color:#8cf;margin-right:1rem;font-size:.85rem}
+ details{font-size:.85rem;color:#aaa;margin-top:.2rem}
+ summary{cursor:pointer}
+ .gl{color:#888}
+</style>
+<nav><a href=/dash>dash</a> <a href=/history>history</a></nav>
+<h2>rule trace</h2>
+<div class=updated>{{.Now | ago}} — winner: <strong>{{if .Winner}}{{.Winner}}{{else}}nothing fired{{end}}</strong></div>
+<table>
+<tr><th>rule<th>sev<th>predicate<th>gate<th>blocked by<th>detail<th>selected<th>lost to</tr>
+{{range .Rules}}<tr>
+<td>{{.RuleName}}</td>
+<td>{{.Severity}}</td>
+<td class={{if .PredicateResult}}green{{else}}gray{{end}}>{{.PredicateResult}}</td>
+<td class={{if .GateResult}}green{{else if .GateBlockedBy}}red{{else}}gray{{end}}>{{.GateResult}}</td>
+<td>{{.GateBlockedBy}}</td>
+<td><details><summary>gate</summary>
+<span class=gl>snooze_until:</span> {{.GateDetail.SnoozeUntil | fmtTime}}<br>
+<span class=gl>cooldown_until:</span> {{.GateDetail.CooldownUntil | fmtTime}}<br>
+<span class=gl>quiet_hours:</span> {{.GateDetail.QuietHours}}<br>
+<span class=gl>calendar_busy:</span> {{.GateDetail.CalendarBusy}}<br>
+<span class=gl>presence:</span> {{.GateDetail.Presence}}<br>
+<span class=gl>inert_keys_missing:</span> {{if .GateDetail.InertKeysMissing}}{{join .GateDetail.InertKeysMissing ", "}}{{else}}—{{end}}
+</details></td>
+<td class={{if .WasSelected}}green{{end}}>{{.WasSelected}}</td>
+<td>{{.LostTo}}</td>
+</tr>{{end}}
+</table>