[0.60.5] Port usage spend sharing semantics

apps/desktop-tauri/src-tauri/src/commands/usage_spend.rs

@@ -60,6 +60,8 @@ struct SpendValues {
 pub struct UsageSpendSummary {
     pub rows: Vec<UsageSpendRow>,
     pub contract: SpendContract,
+    pub reporting_day: String,
+    pub dashboard_timezone: String,
 }
 
 #[derive(Debug, Clone)]
@@ -611,7 +613,25 @@ fn build_usage_spend_summary(
         settings.hide_personal_info,
         selected_summary,
     );
-    UsageSpendSummary { rows, contract }
+    let reporting_day = last_included_reporting_day(&contract);
+    let dashboard_timezone = codexbar::core::local_timezone_name();
+    UsageSpendSummary {
+        rows,
+        contract,
+        reporting_day,
+        dashboard_timezone,
+    }
+}
+
+fn last_included_reporting_day(contract: &SpendContract) -> String {
+    contract
+        .daily
+        .iter()
+        .filter_map(|point| chrono::NaiveDate::parse_from_str(&point.day, "%Y-%m-%d").ok())
+        .max()
+        .unwrap_or_else(|| chrono::Local::now().date_naive())
+        .format("%Y-%m-%d")
+        .to_string()
 }
 
 fn total_token_mix(mix: &codexbar::spend_contract::SpendTokenMix) -> Option<u64> {

apps/desktop-tauri/src/lib/usageSpendSharing.test.ts

@@ -0,0 +1,39 @@
+import { describe, expect, it } from "vitest";
+
+import {
+  formatUsageSpendReportingDay,
+  usageSpendShareFooter,
+  usageSpendSubscriptionCaption,
+} from "./usageSpendSharing";
+
+describe("usage spend sharing", () => {
+  it.each([
+    [0, "0 subscriptions"],
+    [1, "1 subscription"],
+    [2, "2 subscriptions"],
+    [12, "12 subscriptions"],
+  ])("uses the correct subscription caption for %i", (count, expected) => {
+    expect(usageSpendSubscriptionCaption(count)).toBe(expected);
+  });
+
+  it("preserves the reporting day across dashboard timezones", () => {
+    expect(formatUsageSpendReportingDay("2026-09-19", "Pacific/Kiritimati")).toBe("Sep 19, 2026");
+    expect(formatUsageSpendReportingDay("2026-09-19", "America/Los_Angeles")).toBe("Sep 19, 2026");
+    expect(formatUsageSpendReportingDay("2026-10-01", "Pacific/Norfolk")).toBe("Oct 1, 2026");
+  });
+
+  it("falls back for an invalid dashboard timezone or date", () => {
+    expect(formatUsageSpendReportingDay("2026-10-01", "Not/AZone")).toBe("2026-10-01");
+    expect(formatUsageSpendReportingDay("2026-02-31", "UTC")).toBe("2026-02-31");
+  });
+
+  it("builds the report footer from the included day and row count", () => {
+    expect(
+      usageSpendShareFooter({
+        rows: [{}],
+        reportingDay: "2026-09-19",
+        dashboardTimezone: "UTC",
+      }),
+    ).toBe("Data through Sep 19, 2026 · 1 subscription");
+  });
+});

apps/desktop-tauri/src/lib/usageSpendSharing.ts

@@ -0,0 +1,92 @@
+interface CivilDate {
+  year: number;
+  month: number;
+  day: number;
+}
+
+export interface UsageSpendShareSummary {
+  rows: readonly unknown[];
+  reportingDay: string;
+  dashboardTimezone: string;
+}
+
+function parseCivilDate(value: string): CivilDate | null {
+  const match = /^(\d{4})-(\d{2})-(\d{2})$/.exec(value);
+  if (!match) return null;
+  const [, yearText, monthText, dayText] = match;
+  const year = Number(yearText);
+  const month = Number(monthText);
+  const day = Number(dayText);
+  if (year < 1 || month < 1 || month > 12 || day < 1 || day > 31) return null;
+
+  const instant = new Date(0);
+  instant.setUTCFullYear(year, month - 1, day);
+  instant.setUTCHours(12, 0, 0, 0);
+  if (
+    instant.getUTCFullYear() !== year ||
+    instant.getUTCMonth() !== month - 1 ||
+    instant.getUTCDate() !== day
+  ) {
+    return null;
+  }
+  return { year, month, day };
+}
+
+function civilDateInstant(date: CivilDate): Date {
+  const instant = new Date(0);
+  instant.setUTCFullYear(date.year, date.month - 1, date.day);
+  instant.setUTCHours(12, 0, 0, 0);
+  return instant;
+}
+
+function partsInTimeZone(instant: Date, timeZone: string): CivilDate {
+  const parts = new Intl.DateTimeFormat("en-US", {
+    timeZone,
+    year: "numeric",
+    month: "2-digit",
+    day: "2-digit",
+  }).formatToParts(instant);
+  const valueFor = (type: string) => parts.find((part) => part.type === type)?.value;
+  const year = Number(valueFor("year"));
+  const month = Number(valueFor("month"));
+  const day = Number(valueFor("day"));
+  if (![year, month, day].every(Number.isInteger)) {
+    throw new RangeError("Timezone did not provide a complete date");
+  }
+  return { year, month, day };
+}
+
+/** Formats a civil reporting day without allowing the timezone offset to roll it into another day. */
+export function formatUsageSpendReportingDay(
+  reportingDay: string,
+  dashboardTimezone: string,
+  locale = "en-US",
+): string {
+  const civilDate = parseCivilDate(reportingDay);
+  if (!civilDate) return reportingDay;
+
+  try {
+    const target = civilDateInstant(civilDate);
+    // Validate the configured zone, but keep the reporting day as the civil
+    // date supplied by the dashboard. Applying the zone offset to the instant
+    // can move October 1 (and other boundary dates) into a different calendar
+    // day in zones with a non-hour offset or a DST transition.
+    partsInTimeZone(target, dashboardTimezone);
+    return new Intl.DateTimeFormat(locale, {
+      timeZone: "UTC",
+      year: "numeric",
+      month: "short",
+      day: "numeric",
+    }).format(target);
+  } catch {
+    return reportingDay;
+  }
+}
+
+export function usageSpendSubscriptionCaption(count: number): string {
+  return count === 1 ? "1 subscription" : `${count} subscriptions`;
+}
+
+export function usageSpendShareFooter(summary: UsageSpendShareSummary): string {
+  return `Data through ${formatUsageSpendReportingDay(summary.reportingDay, summary.dashboardTimezone)} · ${usageSpendSubscriptionCaption(summary.rows.length)}`;
+}

apps/desktop-tauri/src/surfaces/settings/tabs/UsageSpendTab.tsx

@@ -8,6 +8,7 @@ import {
   updateSettings,
   writeUsageSpendExport,
 } from "../../../lib/tauri";
+import { usageSpendShareFooter } from "../../../lib/usageSpendSharing";
 import type { CostSummaryDisplayStyle, SettingsSnapshot, SpendContract, UsageSpendSummary } from "../../../types/bridge";
 import type { LocaleKey } from "../../../i18n/keys";
 import type { TabProps } from "../settingsTabs";
@@ -55,7 +56,7 @@ function renderSharePng(summary: UsageSpendSummary, title: string): string {
   const headerH = 48;
   const colW = [160, 100, 100, 80, 160];
   const width = pad * 2 + colW.reduce((a, b) => a + b, 0);
-  const height = pad * 2 + headerH + Math.max(1, rows.length) * rowH + 36;
+  const height = pad * 2 + headerH + Math.max(1, rows.length) * rowH + 52;
   const canvas = document.createElement("canvas");
   canvas.width = width * 2;
   canvas.height = height * 2;
@@ -126,6 +127,10 @@ function renderSharePng(summary: UsageSpendSummary, title: string): string {
     });
   }
 
+  ctx.fillStyle = "#8b9bb4";
+  ctx.font = "12px system-ui,Segoe UI,sans-serif";
+  ctx.fillText(usageSpendShareFooter(summary), pad, height - pad);
+
   return canvas.toDataURL("image/png");
 }
 
@@ -218,7 +223,7 @@ export default function UsageSpendTab(_props: TabProps) {
         setShareError(t("UsageSpendShareFailed"));
         return;
       }
-      const stamp = new Date().toISOString().slice(0, 10);
+      const stamp = summary.reportingDay;
       downloadDataUrl(dataUrl, `codexbar-usage-spend-${stamp}.png`);
     } catch {
       setShareError(t("UsageSpendShareFailed"));
@@ -245,7 +250,7 @@ export default function UsageSpendTab(_props: TabProps) {
       return;
     }
     try {
-      const stamp = new Date().toISOString().slice(0, 10);
+      const stamp = summary.reportingDay;
       const path = await save({
         defaultPath: `codexbar-usage-spend-${stamp}.json`,
         filters: [{ name: "JSON", extensions: ["json"] }],

apps/desktop-tauri/src/types/bridge.ts

@@ -379,6 +379,8 @@ export interface UsageSpendRow {
 export interface UsageSpendSummary {
   rows: UsageSpendRow[];
   contract: SpendContract;
+  reportingDay: string;
+  dashboardTimezone: string;
 }
 
 export type CostProvenance = "listPriceEstimate" | "vendorMetered" | "mixed" | "unknown";

rust/src/core/mod.rs

@@ -50,7 +50,7 @@ pub use redactor::*;
 pub use session_equivalent_forecast::*;
 pub use session_quota::*;
 pub use sqlite::*;
-pub(crate) use timezone::local_timezone_name;
+pub use timezone::local_timezone_name;
 pub use token_accounts::*;
 pub use usage_pace::*;
 pub use usage_snapshot::*;

rust/src/core/timezone.rs

@@ -31,7 +31,7 @@ static GLOBALIZATION_PINNED: LazyLock<bool> = LazyLock::new(pin_globalization_dl
 
 /// Returns the IANA name of the system timezone, or `"UTC"` if it cannot be
 /// determined safely.
-pub(crate) fn local_timezone_name() -> String {
+pub fn local_timezone_name() -> String {
     #[cfg(windows)]
     {
         // Deref runs the load+pin to completion on one thread while all