fix(insights): align activity summary window to request timezone

The activity insight attached its range summary by resolving DateFrom
and DateTo as UTC midnights, but the dashboard derives those dates from
the report's local-time range. A non-UTC user got a summary covering a
different window than the dashboard being summarized.

Carry the caller's IANA timezone through the insight request and resolve
the summary's range in that zone, so the summary spans the same local-day
window as the activity report. The frontend forwards the dashboard
timezone; an empty value falls back to UTC.

Author: wesm

frontend/src/lib/api/types/insights.ts

@@ -33,4 +33,7 @@ export interface GenerateInsightRequest {
   project?: string;
   prompt?: string;
   agent?: AgentName;
+  // IANA timezone the date range is expressed in, so the server's activity
+  // summary covers the same local-day window as the dashboard. Omit for UTC.
+  timezone?: string;
 }

frontend/src/lib/components/activity/ActivityInsight.svelte

@@ -13,7 +13,11 @@
   import type { Insight, InsightsResponse } from "../../api/types.js";
   import { LightbulbIcon, PlusIcon } from "../../icons.js";
 
-  let { dateFrom, dateTo }: { dateFrom: string; dateTo: string } = $props();
+  let {
+    dateFrom,
+    dateTo,
+    timezone = "",
+  }: { dateFrom: string; dateTo: string; timezone?: string } = $props();
 
   let insight: Insight | null = $state(null);
   let loading = $state(false);
@@ -110,6 +114,7 @@
         type: "daily_activity",
         date_from: dateFrom,
         date_to: dateTo,
+        timezone,
         agent: "claude",
       },
       (p) => {

frontend/src/lib/components/activity/ActivityPage.svelte

@@ -146,7 +146,11 @@
          otherwise fetch an insight for the wrong span while the report loads). -->
     {#if activity.report}
       <div class="chart-panel">
-        <ActivityInsight dateFrom={insightFrom} dateTo={insightTo} />
+        <ActivityInsight
+          dateFrom={insightFrom}
+          dateTo={insightTo}
+          timezone={activity.timezone}
+        />
       </div>
     {/if}
   </div>

internal/server/huma_routes_insights.go

@@ -335,33 +335,50 @@ func (s *Server) humaGenerateInsight(
 }
 
 // activityRangeSummary resolves the requested range into an activity report and
-// condenses it into a RangeSummary for the insight prompt. The range is the
-// half-open span [DateFrom 00:00 UTC, DateTo+1day 00:00 UTC). It excludes
-// automated sessions so the summary reflects the same interactive-only work
-// BuildPrompt's prompt focuses on; the two otherwise select sessions
-// differently (this uses the activity report's half-open UTC window with an
-// ended_at fallback, BuildPrompt uses ListSessions' calendar-date match on the
-// start date), so the summary is a range-level overview, not a row-for-row
-// mirror of BuildPrompt's session list.
+// condenses it into a RangeSummary for the insight prompt. The range spans the
+// local days [DateFrom, DateTo] in req.Timezone (empty means UTC): the bounds
+// are that zone's midnights, matching the activity dashboard the dates were
+// derived from, so a non-UTC viewer's summary covers the window the dashboard
+// shows rather than a UTC-shifted one. It excludes automated sessions so the
+// summary reflects the same interactive-only work BuildPrompt's prompt focuses
+// on; the two otherwise select sessions differently (this uses the activity
+// report's half-open window with an ended_at fallback, BuildPrompt uses
+// ListSessions' calendar-date match on the start date), so the summary is a
+// range-level overview, not a row-for-row mirror of BuildPrompt's session list.
 func (s *Server) activityRangeSummary(
 	ctx context.Context, req generateInsightRequest,
 ) (*insight.RangeSummary, error) {
-	dateTo, err := time.Parse("2006-01-02", req.DateTo)
+	tz := req.Timezone
+	if tz == "" {
+		tz = "UTC"
+	}
+	loc, err := time.LoadLocation(tz)
+	if err != nil {
+		return nil, fmt.Errorf("loading timezone %q: %w", tz, err)
+	}
+	// Local midnights of DateFrom and the day after DateTo bound the half-open
+	// window, expressed as absolute instants so ResolveQuery's custom-range
+	// parse keeps them exact; Timezone drives only the bucket calendar.
+	from, err := time.ParseInLocation("2006-01-02", req.DateFrom, loc)
+	if err != nil {
+		return nil, fmt.Errorf("parsing date_from %q: %w", req.DateFrom, err)
+	}
+	toDay, err := time.ParseInLocation("2006-01-02", req.DateTo, loc)
 	if err != nil {
 		return nil, fmt.Errorf("parsing date_to %q: %w", req.DateTo, err)
 	}
-	to := dateTo.AddDate(0, 0, 1).Format("2006-01-02")
+	to := toDay.AddDate(0, 0, 1)
 	q, err := activity.ResolveQuery(activity.QueryInput{
 		Preset:   "custom",
-		From:     req.DateFrom + "T00:00:00Z",
-		To:       to + "T00:00:00Z",
-		Timezone: "UTC",
+		From:     from.UTC().Format(time.RFC3339),
+		To:       to.UTC().Format(time.RFC3339),
+		Timezone: tz,
 	}, time.Now())
 	if err != nil {
 		return nil, fmt.Errorf("resolving activity range: %w", err)
 	}
 	r, err := s.db.GetActivityReport(ctx, db.AnalyticsFilter{
-		Timezone:         "UTC",
+		Timezone:         tz,
 		Project:          req.Project,
 		ExcludeAutomated: true,
 	}, q)

internal/server/insights.go

@@ -17,6 +17,10 @@ type generateInsightRequest struct {
 	Project  string `json:"project,omitempty"`
 	Prompt   string `json:"prompt,omitempty"`
 	Agent    string `json:"agent,omitempty"`
+	// Timezone is the IANA zone the caller's date range is expressed in, so
+	// the attached activity summary covers the same local-day window as the
+	// activity dashboard the dates were derived from. Empty means UTC.
+	Timezone string `json:"timezone,omitempty"`
 }
 
 func insightGenerateClientMessage(

internal/server/insights_internal_test.go

@@ -0,0 +1,52 @@
+package server
+
+import (
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"go.kenn.io/agentsview/internal/db"
+)
+
+// TestActivityRangeSummaryUsesRequestTimezone confirms the insight activity
+// summary resolves its window in the request timezone, so a non-UTC viewer's
+// summary covers the same local-day window as the activity dashboard the dates
+// were derived from. A session whose only instant is 2026-06-16T02:00:00Z is
+// the local day 2026-06-15 in America/New_York (UTC-4 in June) but the UTC day
+// 2026-06-16, so the June-15 summary must include it under New York and
+// exclude it under UTC. Before the fix the window was always UTC, so the New
+// York request would have wrongly excluded the session.
+func TestActivityRangeSummaryUsesRequestTimezone(t *testing.T) {
+	srv := testServer(t, 0)
+	ctx := context.Background()
+	ts := "2026-06-16T02:00:00Z"
+	require.NoError(t, srv.db.UpsertSession(db.Session{
+		ID: "x", Project: "proj", Machine: "test", Agent: "claude",
+		StartedAt: &ts, EndedAt: &ts, MessageCount: 1,
+		RelationshipType: "root", DataVersion: 1,
+	}))
+	require.NoError(t, srv.db.ReplaceSessionMessages("x", []db.Message{{
+		SessionID: "x", Ordinal: 0, Role: "assistant", Content: "x",
+		Timestamp: ts, Model: "m1",
+	}}))
+
+	ny, err := srv.activityRangeSummary(ctx, generateInsightRequest{
+		Type: "daily_activity", DateFrom: "2026-06-15", DateTo: "2026-06-15",
+		Timezone: "America/New_York",
+	})
+	require.NoError(t, err)
+	require.NotNil(t, ny)
+	assert.Equal(t, 1, ny.Sessions,
+		"New York June-15 window covers the 02:00Z instant (22:00 local)")
+
+	utc, err := srv.activityRangeSummary(ctx, generateInsightRequest{
+		Type: "daily_activity", DateFrom: "2026-06-15", DateTo: "2026-06-15",
+		Timezone: "UTC",
+	})
+	require.NoError(t, err)
+	require.NotNil(t, utc)
+	assert.Equal(t, 0, utc.Sessions,
+		"UTC June-15 window ends at June 16 00:00Z, before the instant")
+}