diff --git a/build.ts b/build.ts
index 28e1633..808a90a 100644
--- a/build.ts
+++ b/build.ts
@@ -10,8 +10,9 @@ const result = await Bun.build({
   outdir,
   plugins: [tailwind],
   minify: true,
+  splitting: true,
   target: "bun",
-  external: ["@napi-rs/canvas"],
+  external: ["@napi-rs/canvas", "/fonts/browser/*"],
   sourcemap: "linked",
   define: {
     "process.env.NODE_ENV": JSON.stringify("production"),
@@ -30,3 +31,8 @@ await mkdir(path.join(outdir, "fonts"), { recursive: true });
 for (const file of ["InstrumentSerif-Regular.ttf", "NotoSans-Regular.ttf", "NotoSans-Medium.ttf", "NotoSans-SemiBold.ttf"]) {
   await copyFile(`src/assets/fonts/${file}`, path.join(outdir, "fonts", file));
 }
+
+await mkdir(path.join(outdir, "fonts/browser"), { recursive: true });
+for (const file of ["InstrumentSerif-Regular", "InstrumentSerif-Italic", "NotoSans-Regular", "NotoSans-Medium", "NotoSans-SemiBold"]) {
+  await copyFile(`src/assets/fonts/${file}.woff2`, path.join(outdir, `fonts/browser/${file}.woff2`));
+}
diff --git a/bunfig.toml b/bunfig.toml
index 0d0612c..fa3b71d 100644
--- a/bunfig.toml
+++ b/bunfig.toml
@@ -3,5 +3,5 @@
 env = false
 
 [serve.static]
-plugins = ["bun-plugin-tailwind"]
+plugins = ["bun-plugin-tailwind", "./scripts/browser-fonts-plugin.ts"]
 env = "BUN_PUBLIC_*"
diff --git a/scripts/browser-fonts-plugin.ts b/scripts/browser-fonts-plugin.ts
new file mode 100644
index 0000000..e142fcc
--- /dev/null
+++ b/scripts/browser-fonts-plugin.ts
@@ -0,0 +1,9 @@
+import type { BunPlugin } from "bun";
+
+/** Match the production bundler's external font URLs in the HTML dev server. */
+export default {
+  name: "external-browser-fonts",
+  setup(build) {
+    build.onResolve({ filter: /^\/fonts\/browser\// }, args => ({ path: args.path, external: true }));
+  },
+} satisfies BunPlugin;
diff --git a/scripts/dashboard-preview.ts b/scripts/dashboard-preview.ts
index 770aefb..a47a8e0 100644
--- a/scripts/dashboard-preview.ts
+++ b/scripts/dashboard-preview.ts
@@ -1,3 +1,4 @@
+import { browserFont } from "../src/browser-fonts";
 // Isolated browser QA server. Never opens or changes the user's database.
 import { sendDueReminders } from "../src/reminders/worker";
 import type { DiscordFetch } from "../src/sharing/routes";
@@ -55,6 +56,7 @@ const server = Bun.serve({
   hostname: "127.0.0.1",
   port,
   routes: {
+    "/fonts/browser/*": browserFont,
     "/__preview/reminder": () => new Response(reminderMessage ?? "No reminder sent"),
     "/__preview/shared-image": () => sharingPreview && sharedImage ? new Response(sharedImage) : new Response(null, { status: 404 }),
     "/__preview/login": () =>
diff --git a/src/App.test.tsx b/src/App.test.tsx
index 7680f54..971ac6e 100644
--- a/src/App.test.tsx
+++ b/src/App.test.tsx
@@ -91,6 +91,12 @@ function LocationProbe() {
   </>;
 }
 
+async function settleDeferred() {
+  for (let attempt = 0; attempt < 100 && [...container.querySelectorAll('[role="status"]')].some(node => node.textContent === "Loading…"); attempt++) {
+    await act(async () => { await new Promise(resolve => setTimeout(resolve, 1)); });
+  }
+}
+
 async function render(path = "/design-system") {
   await act(async () =>
     root.render(
@@ -100,6 +106,7 @@ async function render(path = "/design-system") {
       </MemoryRouter>,
     ),
   );
+  await settleDeferred();
 }
 
 function connectAccount() {
@@ -131,6 +138,7 @@ describe("homepage", () => {
     const opener = buttonNamed("Settings");
     opener.focus();
     await act(async () => opener.click());
+    await settleDeferred();
     const dialog = container.querySelector<HTMLDialogElement>("dialog#account-settings")!;
     expect(dialog.open).toBe(true);
     expect(dialog.contains(document.activeElement)).toBe(true);
@@ -158,6 +166,7 @@ describe("homepage", () => {
     expect(inner.open).toBe(true);
     expect(inner.querySelector<HTMLButtonElement>('[aria-label="Close dialog"]')?.disabled).toBe(true);
     await act(async () => buttonNamed("Finish save").click());
+    await settleDeferred();
     await act(async () => inner.dispatchEvent(new dom.Event("cancel", { cancelable: true }) as unknown as Event));
     expect(container.querySelector("#inner")).toBeNull();
     expect(container.querySelector<HTMLDialogElement>("#outer")?.open).toBe(true);
@@ -175,10 +184,13 @@ describe("homepage", () => {
     await f.request(`/habits/${h.id}`, "DELETE");
     await render("/");
     await act(async () => buttonNamed("Archived habits").click());
+    await settleDeferred();
     expect(buttonNamed("Restore Reading")).toBeDefined();
     await act(async () => buttonNamed("View history").click());
+    await settleDeferred();
     expect(container.querySelector('[aria-label="2026-09-03: 1 of 1 completion · Complete"]')).not.toBeNull();
     await act(async () => buttonNamed("Restore Reading").click());
+    await settleDeferred();
     expect(container.textContent).toContain("No archived habits.");
     expect((await f.json("/today")).habits[0].name).toBe("Reading");
     expect((await f.json(`/habits/${h.id}/days/2026-09-03`)).complete).toBe(true);
@@ -190,12 +202,16 @@ describe("homepage", () => {
     await f.request(`/habits/${habit.id}`, "DELETE");
     await render("/");
     await act(async () => buttonNamed("Archived habits").click());
+    await settleDeferred();
     await act(async () => buttonNamed("Delete permanently Discard me").click());
+    await settleDeferred();
     expect(container.querySelector("#delete-archived-habit")?.textContent).toContain("This cannot be undone.");
     expect(document.activeElement).toBe(buttonNamed("Keep habit"));
     await act(async () => buttonNamed("Keep habit").click());
+    await settleDeferred();
     expect((await f.request(`/habits/${habit.id}`)).status).toBe(200);
     await act(async () => buttonNamed("Delete permanently Discard me").click());
+    await settleDeferred();
     const confirm = () => container.querySelector<HTMLButtonElement>("#delete-archived-habit .ds-action-row button:last-child")!;
     fetchMock.mockResolvedValueOnce(Response.json({ error: "Temporary failure" }, { status: 500 }));
     await act(async () => confirm().click());
@@ -210,7 +226,7 @@ describe("homepage", () => {
 
   test("historical check-ins use the selected date's tracking method and preserve today", async () => {
     const f = connectAccount();
-    f.setTime("2026-09-03T12:00:00Z");
+    f.setTime("2026-01-03T12:00:00Z");
     const habit = await f.json("/habits", "POST", { name: "Reading", method: "manual" }, 201);
     f.setTime("2026-09-04T12:00:00Z");
     await f.json(`/habits/${habit.id}`, "PATCH", { method: "count", target: 10, unit: "pages" });
@@ -220,12 +236,21 @@ describe("homepage", () => {
     await act(async () => container.querySelector<HTMLButtonElement>('[aria-label^="2026-09-03:"]')!.click());
     expect(buttonNamed("Edit selected check-in").closest(".ds-date-inspector")?.textContent).toContain("September 3, 2026");
     await act(async () => buttonNamed("Edit selected check-in").click());
+    await settleDeferred();
     const past = [...container.querySelectorAll<HTMLInputElement>('input[type="checkbox"]')].find(input => input.closest("label")?.textContent === "Completed on this date")!;
     expect(past).toBeDefined();
     await act(async () => past.click());
     expect((await f.json(`/habits/${habit.id}/days/2026-09-03`)).complete).toBe(true);
     expect((await f.json(`/habits/${habit.id}/days/2026-09-04`)).value).toBe(0);
     expect(container.textContent).toContain("Saved check-in for 2026-09-03");
+    fetchMock.mockClear();
+    await act(async () => {
+      const input = container.querySelector<HTMLInputElement>('input[type="date"]')!;
+      Object.getOwnPropertyDescriptor(dom.HTMLInputElement.prototype, "value")!.set!.call(input, "2026-01-03");
+      input.dispatchEvent(new dom.Event("change", { bubbles: true }) as unknown as Event);
+    });
+    expect(container.querySelector('[aria-label^="2026-01-03:"]')).not.toBeNull();
+    expect(fetchMock.mock.calls.some(([url]) => String(url).includes("from=2025-11-01") && String(url).includes("compact=true"))).toBe(true);
   });
 
   test("signed-out visitors can try progress without calling private habit APIs", async () => {
@@ -233,6 +258,7 @@ describe("homepage", () => {
     expect(container.querySelector("h1")?.textContent).toBe("Small steps.Lasting rhythm.");
     expect(fetchMock.mock.calls.map(call => call[0])).toEqual(["/api/me"]);
     await act(async () => buttonNamed("Increase glasses of water").click());
+    await settleDeferred();
     expect(container.querySelector<HTMLInputElement>('[aria-label="Total glasses of water"]')?.value).toBe("4");
     expect(fetchMock).toHaveBeenCalledTimes(1);
   });
@@ -264,6 +290,7 @@ describe("homepage", () => {
     expect(container.textContent).toContain("Account unavailable");
     expect(container.querySelector("#welcome-title")).toBeNull();
     await act(async () => buttonNamed("Try again").click());
+    await settleDeferred();
     expect(container.querySelector("#welcome-title")).not.toBeNull();
   });
 
@@ -273,6 +300,7 @@ describe("homepage", () => {
     expect(container.textContent).toContain("Welcome back, alice.");
     expect(container.textContent).toContain("Start with one habit.");
     await act(async () => buttonNamed("Add a habit +").click());
+    await settleDeferred();
     const input = container.querySelector<HTMLInputElement>("form input")!;
     expect(document.activeElement).toBe(input);
     await act(async () => {
@@ -285,6 +313,7 @@ describe("homepage", () => {
     expect(container.textContent).not.toContain("Read a little created.");
     expect(container.querySelector(".ds-habit-chart")).not.toBeNull();
     await act(async () => buttonNamed("Sign out").click());
+    await settleDeferred();
     expect(container.querySelector("#welcome-title")).not.toBeNull();
     expect((await f.request("/me")).status).toBe(401);
   });
@@ -310,12 +339,14 @@ describe("homepage", () => {
     expect(container.querySelectorAll('.ds-goal--tasks .ds-routine-items > li')).toHaveLength(1);
 
     await act(async () => buttonNamed("Increase Water").click());
+    await settleDeferred();
     expect(container.querySelector(".ds-welcome-progress")?.textContent).toContain("1 / 3");
     expect(container.querySelectorAll(".ds-goal-graph .ds-calendar")).toHaveLength(3);
     expect(countGoal.querySelector(".ds-goal-status")?.textContent).toBe("Complete");
     expect(container.querySelector(`#history-${water.id} .ds-date-inspector`)?.textContent).toContain("8 of 8 glasses");
     expect(container.textContent).not.toContain("Sunday walk");
     await act(async () => buttonNamed("All habits · 4").click());
+    await settleDeferred();
     const checkbox = (name: string) => [...container.querySelectorAll<HTMLInputElement>('input[type="checkbox"]')].find(input => (input.getAttribute("aria-label") || input.closest("label")?.textContent) === name)!;
     expect(checkbox("Sunday walk done").disabled).toBe(true);
     await act(async () => checkbox("Reading done").click());
@@ -323,9 +354,81 @@ describe("homepage", () => {
     expect(container.querySelector(".ds-welcome-progress")?.textContent).toContain("3 / 3");
     expect((await f.json("/today")).completed).toBe(3);
     await act(async () => buttonNamed("Decrease Water").click());
+    await settleDeferred();
     expect((await f.json("/today")).completed).toBe(2);
   });
 
+  test("focus retains unchanged calendars, detects remote historical edits and loads expanded history on demand", async () => {
+    const f = connectAccount();
+    f.setTime("2026-09-03T12:00:00Z");
+    const reading = await f.json("/habits", "POST", { name: "Reading", method: "manual" }, 201);
+    await f.json("/habits", "POST", { name: "Walking", method: "manual" }, 201);
+    f.setTime("2026-09-04T12:00:00Z");
+    await render("/");
+    const calendarRequests = () => fetchMock.mock.calls.map(([url]) => String(url)).filter(url => url.includes("/calendar?"));
+    expect(calendarRequests()).toHaveLength(2);
+    expect(calendarRequests()[0]).toContain("from=2026-07-01");
+    expect(calendarRequests()[0]).toContain("compact=true");
+    const parse = spyOn(Date, "parse");
+    await act(async () => buttonNamed("All habits · 2").click());
+    await settleDeferred();
+    expect(parse).not.toHaveBeenCalled();
+    parse.mockRestore();
+    fetchMock.mockClear();
+    await act(async () => dom.dispatchEvent(new dom.Event("focus")));
+    expect(calendarRequests()).toHaveLength(0);
+    await f.json(`/habits/${reading.id}/days/2026-09-03/progress`, "PUT", { done: true });
+    await act(async () => dom.dispatchEvent(new dom.Event("focus")));
+    expect(calendarRequests()).toHaveLength(1);
+    expect(calendarRequests()[0]).toContain(reading.id);
+    const history = container.querySelector(`#history-${reading.id}`)!;
+    fetchMock.mockClear();
+    await act(async () => history.querySelector<HTMLButtonElement>('[aria-label="12 months"]')!.click());
+    expect(calendarRequests()).toHaveLength(1);
+    expect(calendarRequests()[0]).toContain("from=2025-10-01");
+    expect(history.querySelectorAll(".ds-day")).toHaveLength(365);
+    fetchMock.mockClear();
+    await act(async () => history.querySelector<HTMLButtonElement>('[aria-label="3 months"]')!.click());
+    expect(calendarRequests()).toHaveLength(0);
+    expect(history.querySelectorAll(".ds-day")).toHaveLength(92);
+    expect(history.querySelector('[aria-label="2026-09-03: 1 of 1 completion · Complete"]')).not.toBeNull();
+    fetchMock.mockClear();
+    f.setTime("2026-09-05T12:00:00Z");
+    await act(async () => dom.dispatchEvent(new dom.Event("focus")));
+    expect(calendarRequests()).toHaveLength(2);
+  });
+
+  test("month rollover preserves a twelve-month preset and an explicit custom window", async () => {
+    const f = connectAccount();
+    f.setTime("2026-09-30T12:00:00Z");
+    const annual = await f.json("/habits", "POST", { name: "Annual", method: "manual" }, 201);
+    const custom = await f.json("/habits", "POST", { name: "Custom", method: "manual" }, 201);
+    await render("/");
+    const annualHistory = container.querySelector(`#history-${annual.id}`)!;
+    const customHistory = container.querySelector(`#history-${custom.id}`)!;
+    await act(async () => annualHistory.querySelector<HTMLButtonElement>('[aria-label="12 months"]')!.click());
+    await act(async () => [...customHistory.querySelectorAll<HTMLButtonElement>("button")].find(button => button.textContent === "Custom")!.click());
+    await act(async () => {
+      for (const [name, value] of [["from", "2026-08-05"], ["to", "2026-09-10"]]) {
+        const input = customHistory.querySelector<HTMLInputElement>(`input[name="${name}"]`)!;
+        Object.getOwnPropertyDescriptor(dom.HTMLInputElement.prototype, "value")!.set!.call(input, value);
+        input.dispatchEvent(new dom.Event("change", { bubbles: true }) as unknown as Event);
+      }
+      customHistory.querySelector("form")!.dispatchEvent(new dom.Event("submit", { bubbles: true, cancelable: true }) as unknown as Event);
+    });
+    fetchMock.mockClear();
+    f.setTime("2026-10-01T12:00:00Z");
+    await act(async () => dom.dispatchEvent(new dom.Event("focus")));
+    const requests = fetchMock.mock.calls.map(([url]) => String(url)).filter(url => url.includes("/calendar?"));
+    expect(requests).toHaveLength(2);
+    expect(requests.find(url => url.includes(annual.id))).toContain("from=2025-11-01&to=2026-10-31");
+    expect(requests.find(url => url.includes(custom.id))).toContain("from=2026-08-05&to=2026-09-10");
+    expect(annualHistory.querySelector(".ds-calendar")?.getAttribute("data-months")).toBe("12");
+    expect(annualHistory.querySelectorAll(".ds-day")).toHaveLength(365);
+    expect(customHistory.querySelector(".ds-calendar")?.getAttribute("data-months")).toBe("custom");
+    expect(customHistory.querySelectorAll(".ds-day")).toHaveLength(37);
+  });
+
   test("a pending counter save leaves other habits usable and refreshes only its history", async () => {
     const f = connectAccount();
     const water = await f.json("/habits", "POST", { name: "Water", method: "count", target: 8, unit: "glasses" }, 201);
@@ -341,6 +444,7 @@ describe("homepage", () => {
     }, { preconnect: fetch.preconnect }));
     fetchMock.mockClear();
     await act(async () => buttonNamed("Increase Water").click());
+    await settleDeferred();
     expect(buttonNamed("Increase Water").disabled).toBe(true);
     const check = container.querySelector<HTMLInputElement>('[aria-label="Reading done"]')!;
     expect(check.disabled).toBe(false);
@@ -367,6 +471,7 @@ describe("homepage", () => {
     f.setTime("2026-09-04T12:00:00Z");
     await render("/");
     await act(async () => buttonNamed("Edit habit Water").click());
+    await settleDeferred();
     const form = container.querySelector<HTMLFormElement>('form[aria-label="Edit habit Water"]')!;
     expect(document.activeElement).toBe(form.querySelector("input"));
     await act(async () => {
@@ -384,11 +489,15 @@ describe("homepage", () => {
     expect(container.querySelector("form")).toBeNull();
     expect(container.querySelector("h3")?.textContent).toContain("Daily water");
     await act(async () => buttonNamed("Archive habit Daily water").click());
+    await settleDeferred();
     expect((await f.json("/habits")).habits).toHaveLength(1);
     await act(async () => buttonNamed("Cancel").click());
+    await settleDeferred();
     expect((await f.json("/habits")).habits).toHaveLength(1);
     await act(async () => buttonNamed("Archive habit Daily water").click());
+    await settleDeferred();
     await act(async () => buttonNamed("Archive habit").click());
+    await settleDeferred();
     expect((await f.json("/habits")).habits).toHaveLength(0);
     expect(container.querySelector(".ds-habit-chart")).toBeNull();
     const previous = await f.json(`/habits/${habit.id}/days/2026-09-03`);
@@ -407,6 +516,7 @@ describe("homepage", () => {
     await f.json(`/habits/${habit.id}/days/2026-09-04/tasks/${task.id}`, "PUT", { done: true });
     await render("/");
     await act(async () => buttonNamed("Edit task Stretch").click());
+    await settleDeferred();
     const form = container.querySelector<HTMLFormElement>('form[aria-label="Edit task Stretch"]')!;
     await act(async () => {
       const input = form.querySelector("input")!;
@@ -419,7 +529,9 @@ describe("homepage", () => {
     expect(saved.schedule).toEqual({ type: "weekdays", days: [4, 5] });
     expect((await f.json("/today")).habits[0].value).toBe(1);
     await act(async () => buttonNamed("Delete task Stretch gently").click());
+    await settleDeferred();
     await act(async () => buttonNamed("Delete task").click());
+    await settleDeferred();
     const today = (await f.json("/today")).habits[0];
     expect(today.target).toBe(1);
     expect(today.value).toBe(0);
@@ -435,9 +547,11 @@ describe("homepage", () => {
     await render("/");
     expect(container.querySelector(".ds-habit-chart")).toBeNull();
     await act(async () => buttonNamed("All habits · 1").click());
+    await settleDeferred();
     expect(container.textContent).toContain("Not scheduled today");
     expect(container.querySelector<HTMLInputElement>('.ds-editable-task input[type="checkbox"]')?.disabled).toBe(true);
     await act(async () => buttonNamed("Edit task Walk").click());
+    await settleDeferred();
     const form = container.querySelector<HTMLFormElement>('form[aria-label="Edit task Walk"]')!;
     await act(async () => {
       const input = form.querySelector("input")!;
@@ -477,6 +591,7 @@ describe("homepage", () => {
       { type: "daily" },
     ] as const) {
       await act(async () => buttonNamed("Edit task Walk").click());
+    await settleDeferred();
       const form = container.querySelector<HTMLFormElement>('form[aria-label="Edit task Walk"]')!;
       await selectValue(form.querySelector("select")!, schedule.type);
       if (schedule.type === "interval" || schedule.type === "weekly") {
@@ -489,6 +604,7 @@ describe("homepage", () => {
       if (schedule.type === "interval") expect(buttonNamed("All habits · 1").getAttribute("aria-pressed")).toBe("true");
       expect(container.querySelector("form")).toBeNull();
       await act(async () => buttonNamed("Edit task Walk").click());
+    await settleDeferred();
       const reopened = container.querySelector<HTMLFormElement>('form[aria-label="Edit task Walk"]')!;
       expect(reopened.querySelector("select")?.value).toBe(schedule.type);
       if (schedule.type === "interval" || schedule.type === "weekly") {
@@ -496,6 +612,7 @@ describe("homepage", () => {
         expect(reopened.querySelector<HTMLInputElement>('input[type="date"]')?.value).toBe(schedule.anchor);
       }
       await act(async () => buttonNamed("Cancel").click());
+    await settleDeferred();
     }
     const previous = await f.json(`/habits/${habit.id}/days/2026-09-03`);
     expect(previous.tasks[0].done).toBe(true);
@@ -515,17 +632,20 @@ describe("homepage", () => {
     };
     const submit = async () => act(async () => container.querySelector("form")!.dispatchEvent(new dom.Event("submit", { bubbles: true, cancelable: true }) as unknown as Event));
     await act(async () => buttonNamed("Edit habit Reading").click());
+    await settleDeferred();
     await selectMethod("count");
     await act(async () => container.querySelector<HTMLInputElement>('form input[type="checkbox"]')!.click());
     await submit();
     expect((await f.json(`/habits/${habit.id}`)).method).toBe("count");
     expect((await f.json(`/habits/${habit.id}`)).carryPartialProgress).toBe(true);
     await act(async () => buttonNamed("Edit habit Reading").click());
+    await settleDeferred();
     expect(container.querySelector<HTMLInputElement>('form input[type="checkbox"]')?.checked).toBe(true);
     await selectMethod("tasks");
     await submit();
     expect((await f.json(`/habits/${habit.id}`)).method).toBe("tasks");
     await act(async () => buttonNamed("Add task").click());
+    await settleDeferred();
     const form = container.querySelector<HTMLFormElement>('form[aria-label="Add task"]')!;
     await act(async () => {
       const input = form.querySelector("input")!;
@@ -545,16 +665,19 @@ describe("homepage", () => {
     const habit = await f.json("/habits", "POST", { name: "Reading", method: "manual" }, 201);
     await render("/");
     await act(async () => buttonNamed("Archive habit Reading").click());
+    await settleDeferred();
     fetchMock.mockImplementationOnce((async (input, init) => {
       return f.request(String(input).replace("/api", ""), init?.method);
     }) as typeof fetch);
     fetchMock.mockResolvedValueOnce(new Response(null, { status: 500 }));
     await act(async () => buttonNamed("Archive habit").click());
+    await settleDeferred();
     expect(container.querySelector("form")).toBeNull();
     expect(container.textContent).toContain("Your change was saved, but the dashboard could not refresh");
     expect(buttonNamed("Archive habit Reading").disabled).toBe(true);
     expect((await f.json(`/habits/${habit.id}`)).archived).toBe(true);
     await act(async () => buttonNamed("Try again").click());
+    await settleDeferred();
     expect(container.querySelector(".ds-habit-chart")).toBeNull();
     expect(fetchMock.mock.calls.filter(call => call[1]?.method === "DELETE")).toHaveLength(1);
   });
@@ -565,10 +688,12 @@ describe("homepage", () => {
     await render("/");
     fetchMock.mockResolvedValueOnce(Response.json({ error: "Save unavailable" }, { status: 500 }));
     await act(async () => buttonNamed("Increase Water").click());
+    await settleDeferred();
     expect(container.querySelector('[role="alert"]')?.textContent).toContain("Save unavailable");
     expect(container.querySelector<HTMLInputElement>('[aria-label="Total Water"]')?.value).toBe("0");
     expect(buttonNamed("Increase Water").disabled).toBe(false);
     await act(async () => buttonNamed("Increase Water").click());
+    await settleDeferred();
     expect(container.querySelector<HTMLInputElement>('[aria-label="Total Water"]')?.value).toBe("1");
     expect((await f.json("/today")).habits[0].value).toBe(1);
   });
diff --git a/src/App.tsx b/src/App.tsx
index 54c8998..d271b7f 100644
--- a/src/App.tsx
+++ b/src/App.tsx
@@ -1,5 +1,6 @@
 import { Navigate, Route, Routes } from "react-router";
-import { DesignSystem } from "./pages/DesignSystem";
+import { deferred } from "./components/design-system/deferred";
+const DesignSystem = deferred(() => import("./pages/DesignSystem").then(module => module.DesignSystem));
 import { Home } from "./pages/Home";
 import { AuthProvider } from "./components/AuthProvider";
 
diff --git a/src/assets/fonts/InstrumentSerif-Italic.woff2 b/src/assets/fonts/InstrumentSerif-Italic.woff2
new file mode 100644
index 0000000..444b688
Binary files /dev/null and b/src/assets/fonts/InstrumentSerif-Italic.woff2 differ
diff --git a/src/assets/fonts/InstrumentSerif-Regular.woff2 b/src/assets/fonts/InstrumentSerif-Regular.woff2
new file mode 100644
index 0000000..6580bf1
Binary files /dev/null and b/src/assets/fonts/InstrumentSerif-Regular.woff2 differ
diff --git a/src/assets/fonts/NotoSans-Medium.woff2 b/src/assets/fonts/NotoSans-Medium.woff2
new file mode 100644
index 0000000..c66dc4a
Binary files /dev/null and b/src/assets/fonts/NotoSans-Medium.woff2 differ
diff --git a/src/assets/fonts/NotoSans-Regular.woff2 b/src/assets/fonts/NotoSans-Regular.woff2
new file mode 100644
index 0000000..9465704
Binary files /dev/null and b/src/assets/fonts/NotoSans-Regular.woff2 differ
diff --git a/src/assets/fonts/NotoSans-SemiBold.woff2 b/src/assets/fonts/NotoSans-SemiBold.woff2
new file mode 100644
index 0000000..6a9e444
Binary files /dev/null and b/src/assets/fonts/NotoSans-SemiBold.woff2 differ
diff --git a/src/assets/fonts/README.md b/src/assets/fonts/README.md
index b1890d9..d9012fe 100644
--- a/src/assets/fonts/README.md
+++ b/src/assets/fonts/README.md
@@ -12,3 +12,24 @@ Downloaded September 7, 2026. The files are versioned in this repository and cop
 into the production image. Browser and native canvas renderers use the alias
 `Mina Sans`; no system sans-serif font is selected for card text. The native font
 loader fails startup if a required font cannot be registered.
+
+Browser WOFF2 copies are lossless conversions of these exact TTF files using
+FontTools with Brotli; no subsetting is applied. All glyphs and Unicode mappings
+are retained (3,748 glyphs for each Noto Sans weight, 377 for each Instrument
+Serif style). Native canvas keeps using the original TTFs. CSS uses separately
+cacheable `/fonts/browser/*.woff2` URLs so font bytes do not block CSS parsing.
+
+Regenerate with `uv run --with fonttools --with brotli python`:
+
+```python
+from pathlib import Path
+from fontTools.ttLib import TTFont
+for path in Path("src/assets/fonts").glob("*.ttf"):
+    font = TTFont(path)
+    cmap, glyphs = font.getBestCmap(), font.getGlyphOrder()
+    font.flavor = "woff2"
+    font.save(path.with_suffix(".woff2"))
+    restored = TTFont(path.with_suffix(".woff2"))
+    assert restored.getBestCmap() == cmap
+    assert restored.getGlyphOrder() == glyphs
+```
diff --git a/src/browser-fonts.test.ts b/src/browser-fonts.test.ts
new file mode 100644
index 0000000..e90bed8
--- /dev/null
+++ b/src/browser-fonts.test.ts
@@ -0,0 +1,14 @@
+import { expect, test } from "bun:test";
+import { browserFont } from "./browser-fonts";
+test("browser fonts are external WOFF2 files with conditional caching and a fixed allowlist", async () => {
+  const url = "http://localhost/fonts/browser/InstrumentSerif-Regular.woff2";
+  const response = browserFont(new Request(url));
+  expect(response.status).toBe(200);
+  expect(response.headers.get("Content-Type")).toBe("font/woff2");
+  const bytes = new Uint8Array(await response.arrayBuffer());
+  expect(new TextDecoder().decode(bytes.slice(0, 4))).toBe("wOF2");
+  expect(browserFont(new Request(url, { headers: { "If-None-Match": response.headers.get("ETag")! } })).status).toBe(304);
+  expect(browserFont(new Request("http://localhost/fonts/browser/.env")).status).toBe(404);
+  expect(browserFont(new Request("http://localhost/fonts/browser/%2e%2e%2f.env")).status).toBe(404);
+  expect(await browserFont(new Request(url, { method: "HEAD" })).text()).toBe("");
+});
diff --git a/src/browser-fonts.ts b/src/browser-fonts.ts
new file mode 100644
index 0000000..b720907
--- /dev/null
+++ b/src/browser-fonts.ts
@@ -0,0 +1,18 @@
+import path from "node:path";
+
+const names = ["InstrumentSerif-Regular", "InstrumentSerif-Italic", "NotoSans-Regular", "NotoSans-Medium", "NotoSans-SemiBold"];
+const directory = process.env.NODE_ENV === "production" ? "fonts/browser" : "src/assets/fonts";
+const fonts: Map<string, { file: ReturnType<typeof Bun.file>; etag: string }> = new Map(names.map(name => {
+  const file = Bun.file(path.resolve(directory, `${name}.woff2`));
+  return [`${name}.woff2`, { file, etag: `"${file.size.toString(16)}-${file.lastModified.toString(16)}"` }] as const;
+}));
+
+/** Explicit allowlist: font URLs never grant access to other filesystem paths. */
+export function browserFont(request: Request): Response {
+  const name = new URL(request.url).pathname.slice("/fonts/browser/".length);
+  const font = fonts.get(name);
+  if (!font || !["GET", "HEAD"].includes(request.method)) return new Response(null, { status: 404 });
+  const headers = { "Content-Type": "font/woff2", "Cache-Control": "public, max-age=3600", ETag: font.etag };
+  if (request.headers.get("If-None-Match") === font.etag) return new Response(null, { status: 304, headers });
+  return new Response(request.method === "HEAD" ? null : font.file, { headers });
+}
diff --git a/src/components/ArchivedHabits.tsx b/src/components/ArchivedHabits.tsx
index 0952382..4cd0db1 100644
--- a/src/components/ArchivedHabits.tsx
+++ b/src/components/ArchivedHabits.tsx
@@ -71,7 +71,7 @@ export function ArchivedHabits({ date, revision, onChanged, onExpired, onClose }
             <Button variant="text" disabled={busy || loading} aria-label={`Delete permanently ${habit.name}`} aria-haspopup="dialog" onClick={() => { setDeleteError(""); setDeleting(habit); }}><Trash2 size={16} aria-hidden="true" />Delete permanently</Button>
           </div>
         </header>
-        {selected === habit.habitId && <div className="ds-record-detail" id={`archive-history-${habit.habitId}`}><HabitHistory calendarOnly habit={habit} date={date} revision={revision + attempt} disabled={busy || loading} onExpired={onExpired} onHistorySaved={() => setAttempt(value => value + 1)} /></div>}
+        {selected === habit.habitId && <div className="ds-record-detail" id={`archive-history-${habit.habitId}`}><HabitHistory calendarOnly habit={habit} date={date} revision={habit.calendarRevision ?? revision + attempt} disabled={busy || loading} onExpired={onExpired} onHistorySaved={() => setAttempt(value => value + 1)} /></div>}
       </article>)}
     </div>
     {deleting && <Modal id="delete-archived-habit" size="compact" eyebrow="PERMANENT DELETION" title="Delete this habit?" description={`“${deleting.name ?? "Habit"}” and all its check-ins, tasks, and progress history will be permanently deleted. It will be removed from combined charts; charts with no remaining habits will also be deleted. This cannot be undone.`} busy={busy} initialFocus="[data-cancel-delete]" returnFocus={() => archiveFocus.current} onClose={() => setDeleting(null)}>
diff --git a/src/components/CalendarCache.test.ts b/src/components/CalendarCache.test.ts
new file mode 100644
index 0000000..1065574
--- /dev/null
+++ b/src/components/CalendarCache.test.ts
@@ -0,0 +1,27 @@
+import { afterAll, afterEach, expect, spyOn, test } from "bun:test";
+import { CalendarCache } from "./CalendarCache";
+const fetchSpy = spyOn(globalThis, "fetch");
+afterEach(() => fetchSpy.mockReset());
+afterAll(() => fetchSpy.mockRestore());
+const range = { from: "2026-07-01", to: "2026-09-30" };
+test("calendar cache shares in-flight reads, retains wider history and invalidates changed versions", async () => {
+  fetchSpy.mockImplementation(Object.assign(async () => Response.json({ from: range.from, to: range.to, days: [{ date: "2026-07-01" }, { date: "2026-09-01" }] }), { preconnect: fetch.preconnect }));
+  const cache = new CalendarCache();
+  await Promise.all([cache.load("habit", "v1", range), cache.load("habit", "v1", range)]);
+  expect(fetchSpy).toHaveBeenCalledTimes(1);
+  expect(String(fetchSpy.mock.calls[0]![0])).toContain("compact=true");
+  const subset = await cache.load("habit", "v1", { from: "2026-09-01", to: range.to });
+  expect(subset.days).toHaveLength(1);
+  expect(fetchSpy).toHaveBeenCalledTimes(1);
+  await cache.load("habit", "v2", range);
+  expect(fetchSpy).toHaveBeenCalledTimes(2);
+  await new CalendarCache().load("habit", "v2", range);
+  expect(fetchSpy).toHaveBeenCalledTimes(3);
+});
+test("a failed history request can be retried without retaining a rejected cache entry", async () => {
+  fetchSpy.mockRejectedValueOnce(new Error("offline")).mockResolvedValue(Response.json({ ...range, days: [] }));
+  const cache = new CalendarCache();
+  await expect(cache.load("habit", "v1", range)).rejects.toThrow("offline");
+  await expect(cache.load("habit", "v1", range)).resolves.toMatchObject({ days: [] });
+  expect(fetchSpy).toHaveBeenCalledTimes(2);
+});
diff --git a/src/components/CalendarCache.tsx b/src/components/CalendarCache.tsx
new file mode 100644
index 0000000..2b38572
--- /dev/null
+++ b/src/components/CalendarCache.tsx
@@ -0,0 +1,34 @@
+import { createContext, useContext, useRef, type ReactNode } from "react";
+import type { CalendarResponse } from "../shared/calendar";
+import { habitRequest } from "../lib/dashboard";
+
+type Range = { from: string; to: string };
+type Entry = Range & { version: string; value: Promise<CalendarResponse> };
+/** Account-scoped, bounded cache; never survives signing out or changing accounts. */
+export class CalendarCache {
+  private entries = new Map<string, Entry[]>();
+  load(habitId: string, version: string, range: Range) {
+    const entries = (this.entries.get(habitId) ?? []).filter(entry => entry.version === version);
+    const cached = entries.find(entry => entry.from <= range.from && entry.to >= range.to);
+    if (cached) return cached.value.then(value => ({ ...value, ...range, days: value.days.filter(day => day.date >= range.from && day.date <= range.to) }));
+    const entry: Entry = { ...range, version, value: habitRequest<CalendarResponse>(`/habits/${habitId}/calendar?${new URLSearchParams({ ...range, compact: "true" })}`) };
+    entries.push(entry);
+    this.entries.delete(habitId);
+    this.entries.set(habitId, entries.slice(-8));
+    if (this.entries.size > 100) this.entries.delete(this.entries.keys().next().value!);
+    entry.value.catch(() => { const current = this.entries.get(habitId); if (current) this.entries.set(habitId, current.filter(item => item !== entry)); });
+    return entry.value;
+  }
+}
+const Context = createContext<CalendarCache | null>(null);
+export function CalendarCacheProvider({ children }: { children: ReactNode }) {
+  const cache = useRef<CalendarCache | null>(null);
+  cache.current ??= new CalendarCache();
+  return <Context.Provider value={cache.current}>{children}</Context.Provider>;
+}
+export function useCalendarCache() {
+  const shared = useContext(Context);
+  const local = useRef<CalendarCache | null>(null);
+  local.current ??= new CalendarCache();
+  return shared ?? local.current;
+}
diff --git a/src/components/HabitHistory.tsx b/src/components/HabitHistory.tsx
index 93bd5f2..d3b0138 100644
--- a/src/components/HabitHistory.tsx
+++ b/src/components/HabitHistory.tsx
@@ -1,15 +1,17 @@
+import { useCalendarCache } from "./CalendarCache";
 import { Modal } from "./design-system/Modal";
 import { Pencil } from "lucide-react";
-import { useEffect, useRef, useState, type ReactNode } from "react";
+import { useEffect, useMemo, useRef, useState, type ReactNode } from "react";
 import type { CalendarResponse } from "../shared/calendar";
 import { habitRequest, scheduleLabel, type TodayHabit } from "../lib/dashboard";
 import { CalendarHeatmap } from "./design-system/CalendarHeatmap";
-import { monthWindow } from "./design-system/calendar-model";
+import { monthWindow, type MonthView } from "./design-system/calendar-model";
 import { Button } from "./design-system/primitives";
 import { HabitChart } from "./design-system/HabitChart";
 import { CalendarLegend } from "./design-system/CalendarLegend";
 import { shade } from "../habits/calendar";
-import { CheckInEditor } from "./CheckInEditor";
+import { deferred } from "./design-system/deferred";
+const CheckInEditor = deferred(() => import("./CheckInEditor").then(module => module.CheckInEditor));
 import { Field } from "./design-system/Field";
 import { ItemActions } from "./design-system/ItemActions";
 
@@ -40,7 +42,29 @@ export function HabitHistory({
   onHistorySaved?: () => void;
   calendarOnly?: boolean;
 }) {
+  const cache = useCalendarCache();
+  const [rangeSelection, setRangeSelection] = useState(() => ({ date, months: 3 as MonthView | "custom", range: monthWindow(date, 3) }));
+  const range = useMemo(() => {
+    if (rangeSelection.date === date || rangeSelection.months === "custom") return rangeSelection.range;
+    // A preset follows the current month across midnight; an explicitly inspected
+    // older window and custom dates retain the user's chosen historical period.
+    const previousCurrent = monthWindow(rangeSelection.date, rangeSelection.months);
+    const anchor = rangeSelection.range.to < previousCurrent.to ? rangeSelection.range.to : date;
+    return monthWindow(anchor, rangeSelection.months);
+  }, [date, rangeSelection]);
+  function requestRange(next: { from: string; to: string }, months: MonthView | "custom" = rangeSelection.months) {
+    setRangeSelection({ date, months, range: next });
+  }
+  const [historyLoading, setHistoryLoading] = useState(false);
   const [selectedDate, setSelectedDate] = useState<string>();
+  function selectDate(selected: string) {
+    setSelectedDate(selected);
+    const available = monthWindow(date, 12);
+    if (rangeSelection.months !== "custom" && selected >= available.from && selected <= available.to && (selected < range.from || selected > range.to)) {
+      const requested = monthWindow(selected, rangeSelection.months);
+      requestRange({ from: requested.from < available.from ? available.from : requested.from, to: requested.to });
+    }
+  }
   const [editingDay, setEditingDay] = useState(false);
   const [savingDay, setSavingDay] = useState(false);
   const [calendar, setCalendar] = useState<CalendarResponse | null>(null);
@@ -49,26 +73,20 @@ export function HabitHistory({
   const expired = useRef(onExpired);
   expired.current = onExpired;
   useEffect(() => {
-    const controller = new AbortController();
+    let active = true;
     setError("");
-    const range = monthWindow(date, 12);
-    habitRequest<CalendarResponse>(
-      `/habits/${habit.habitId}/calendar?${new URLSearchParams(range)}`,
-      { signal: controller.signal },
-    )
-      .then((result) => {
-        if (!controller.signal.aborted) setCalendar(result);
-      })
-      .catch((error) => {
-        if (controller.signal.aborted) return;
-        if (error.message.includes("session has expired") && expired.current)
-          expired.current();
+    setHistoryLoading(true);
+    cache.load(habit.habitId, `${date}:${revision}:${attempt}`, range)
+      .then(result => { if (active) setCalendar(result); })
+      .catch(error => {
+        if (!active) return;
+        if (error.message.includes("session has expired") && expired.current) expired.current();
         else setError(error.message);
-      });
-    return () => controller.abort();
-  }, [habit.habitId, date, revision, attempt]);
+      }).finally(() => { if (active) setHistoryLoading(false); });
+    return () => { active = false; };
+  }, [cache, habit.habitId, date, revision, attempt, range.from, range.to]);
 
-  const days =
+  const days = useMemo(() =>
     calendar?.days.map((day) => ({
       date: day.date,
       color: day.color,
@@ -80,14 +98,14 @@ export function HabitHistory({
         : day.due
           ? ("due" as const)
           : ("not-due" as const),
-    })) ?? [];
+    })) ?? [], [calendar]);
   const steps = Math.max(
     1,
     calendar?.days.find((day) => day.date === date)?.shadeCount ??
       habit.target ??
       1,
   );
-  const shades = calendar
+  const shades = useMemo(() => calendar
     ? [
         calendar.settings.emptyColor,
         ...Array.from(
@@ -101,7 +119,7 @@ export function HabitHistory({
             ).color,
         ),
       ]
-    : [];
+    : [], [calendar, steps]);
   const chart = error ? (
     <div className="ds-form-feedback">
       <p role="alert">{error}</p>
@@ -119,17 +137,20 @@ export function HabitHistory({
   ) : (
     <>
     <CalendarHeatmap
-      onSelectDate={setSelectedDate}
+      onSelectDate={selectDate}
       selectedDate={selectedDate}
       compact
       initialMonths={3}
+      availableRange={monthWindow(date, 12)}
+      onRangeChange={requestRange}
+      loading={historyLoading}
       historyLabel="Your recorded progress"
       label={`${habit.name} progress calendar`}
       unit={habit.unit}
       color={calendar.settings.mainColor}
       emptyColor={calendar.settings.emptyColor}
       days={days}
-      selectedDayAction={selected => <Button variant="secondary" disabled={disabled} aria-label="Edit selected check-in" aria-haspopup="dialog" onClick={() => { setSelectedDate(selected); setEditingDay(true); }}><Pencil size={16} aria-hidden="true" />Edit check-in</Button>}
+      selectedDayAction={selected => <Button variant="secondary" disabled={disabled} aria-label="Edit selected check-in" aria-haspopup="dialog" onClick={() => { selectDate(selected); setEditingDay(true); }}><Pencil size={16} aria-hidden="true" />Edit check-in</Button>}
       legend={
         <CalendarLegend
           label={`${habit.name} progress calendar`}
@@ -141,7 +162,7 @@ export function HabitHistory({
     />
     {editingDay && <Modal id={`check-in-${habit.habitId}`} title="Edit check-in" description={habit.name ?? "Habit"} closeLabel="Close check-in editor" onClose={() => setEditingDay(false)} busy={savingDay}>
     <div className="ds-history-editor">
-      <div className="ds-form-stack"><Field label="Check-in date">{id => <input id={id} type="date" disabled={savingDay} max={date} value={selectedDate ?? date} onChange={event => { if (event.target.value) setSelectedDate(event.target.value); }} />}</Field></div>
+      <div className="ds-form-stack"><Field label="Check-in date">{id => <input id={id} type="date" disabled={savingDay} max={date} value={selectedDate ?? date} onChange={event => { if (event.target.value) selectDate(event.target.value); }} />}</Field></div>
       <CheckInEditor key={`${habit.habitId}:${selectedDate ?? date}`} habitId={habit.habitId} date={selectedDate ?? date} disabled={disabled} onExpired={onExpired}
         onBusyChange={setSavingDay} onSaved={() => { setAttempt(value => value + 1); onHistorySaved?.(); }} />
     </div></Modal>}
diff --git a/src/components/design-system/CalendarHeatmap.tsx b/src/components/design-system/CalendarHeatmap.tsx
index 400fd4c..998897e 100644
--- a/src/components/design-system/CalendarHeatmap.tsx
+++ b/src/components/design-system/CalendarHeatmap.tsx
@@ -1,6 +1,6 @@
 import { useTheme } from "../ThemeProvider";
 import { habitProgressColor, themedHabitShade } from "../../lib/habit-palette";
-import { useId, useLayoutEffect, useRef, useState, type CSSProperties, type ReactNode } from "react";
+import { useId, useMemo, useLayoutEffect, useRef, useState, type CSSProperties, type ReactNode } from "react";
 import { CalendarLegend } from "./CalendarLegend";
 import { Field } from "./Field";
 import { Button } from "./primitives";
@@ -10,6 +10,7 @@ import {
   calendarTimeline,
   MONTH_VIEWS,
   visibleCalendarDays,
+  monthWindow,
   type CalendarDay,
   type MonthView,
 } from "./calendar-model";
@@ -26,7 +27,13 @@ export function CalendarHeatmap({
   historyLabel,
   legend,
   selectedDayAction,
+  availableRange,
+  onRangeChange,
+  loading = false,
 }: {
+  availableRange?: { from: string; to: string };
+  onRangeChange?: (range: { from: string; to: string }, months: MonthView | "custom") => void;
+  loading?: boolean;
   days: CalendarDay[];
   unit: string;
   label: string;
@@ -65,15 +72,15 @@ export function CalendarHeatmap({
     if (onSelectDate) onSelectDate(date);
     else setLocalSelectedDate(date);
   }
-  const days = months === "custom" && customRange
+  const days = useMemo(() => months === "custom" && customRange
     ? allDays.filter((day) => day.date >= customRange.from && day.date <= customRange.to)
-    : anchor ? visibleCalendarDays(allDays, months === "custom" ? 12 : months, anchor) : [];
+    : anchor ? visibleCalendarDays(allDays, months === "custom" ? 12 : months, anchor) : [], [allDays, months, customRange, anchor]);
   const selected =
     days.find((day) => day.date === selectedDate) ??
     days.find((day) => day.date === anchor) ??
     days[0];
   // Date keys and the shared timeline remain stable when the chart resizes.
-  const timeline = calendarTimeline(days);
+  const timeline = useMemo(() => calendarTimeline(days), [days]);
   const buttons = useRef<(HTMLButtonElement | null)[]>([]);
   const inspectorId = useId();
   const instructionsId = useId();
@@ -100,6 +107,7 @@ export function CalendarHeatmap({
     <div
       className={`ds-calendar${compact ? " ds-calendar--compact" : ""}`}
       data-months={months}
+      aria-busy={loading}
       style={{ "--calendar-weeks": timeline.weeks, "--calendar-color": color } as CSSProperties}
     >
       <div className="ds-calendar-range-toolbar">
@@ -130,7 +138,7 @@ export function CalendarHeatmap({
               type="button"
               aria-label={`${value} ${value === 1 ? "month" : "months"}`}
               aria-pressed={months === value}
-              onClick={() => setMonths(value)}
+              onClick={() => { setMonths(value); if (anchor) onRangeChange?.(monthWindow(anchor, value), value); }}
             >
               {value}m
             </button>
@@ -142,6 +150,7 @@ export function CalendarHeatmap({
               if (!customRange) setCustomRange({ from: days[0]!.date, to: days.at(-1)!.date });
               setRangeError("");
               setMonths("custom");
+              onRangeChange?.(customRange ?? { from: days[0]!.date, to: days.at(-1)!.date }, "custom");
             }}
           >
             Custom
@@ -160,7 +169,7 @@ export function CalendarHeatmap({
             const end = form.elements.namedItem("to") as HTMLInputElement;
             const isAvailable = (input: HTMLInputElement) =>
               input.validity.valid && input.value !== "" &&
-              input.value >= allDays[0]!.date && input.value <= allDays.at(-1)!.date;
+              input.value >= (availableRange?.from ?? allDays[0]!.date) && input.value <= (availableRange?.to ?? allDays.at(-1)!.date);
             if (!isAvailable(start) || !isAvailable(end)) {
               setRangeError("Choose both dates within the available history.");
               (!isAvailable(start) ? start : end).focus();
@@ -171,11 +180,12 @@ export function CalendarHeatmap({
               end.focus();
               return;
             }
-            if (!allDays.some((day) => day.date >= start.value && day.date <= end.value)) {
+            if (!availableRange && !allDays.some((day) => day.date >= start.value && day.date <= end.value)) {
               setRangeError("There are no calendar dates in this range.");
               return;
             }
             setCustomRange({ from: start.value, to: end.value });
+            onRangeChange?.({ from: start.value, to: end.value }, "custom");
             setRangeError("");
           }}
         >
@@ -187,8 +197,8 @@ export function CalendarHeatmap({
                   name={name}
                   type="date"
                   required
-                  min={allDays[0]!.date}
-                  max={allDays.at(-1)!.date}
+                  min={availableRange?.from ?? allDays[0]!.date}
+                  max={availableRange?.to ?? allDays.at(-1)!.date}
                   defaultValue={customRange[name]}
                   aria-invalid={rangeError ? true : undefined}
                   aria-describedby={rangeError ? rangeErrorId : undefined}
@@ -201,6 +211,7 @@ export function CalendarHeatmap({
           {rangeError && <p id={rangeErrorId} className="ds-calendar-range-error" role="alert">{rangeError}</p>}
         </form>
       )}
+      {loading && <p role="status" className="ds-supporting-copy">Loading history…</p>}
       <div
         className="ds-calendar-viewport"
         role="group"
diff --git a/src/components/design-system/deferred.tsx b/src/components/design-system/deferred.tsx
new file mode 100644
index 0000000..d5df3a7
--- /dev/null
+++ b/src/components/design-system/deferred.tsx
@@ -0,0 +1,9 @@
+import { lazy, Suspense, type ComponentProps, type ComponentType } from "react";
+
+/** Keep the surrounding workspace usable while an optional surface loads. */
+export function deferred<Component extends ComponentType<any>>(load: () => Promise<Component>) {
+  const Surface = lazy(async () => ({ default: await load() })) as ComponentType<ComponentProps<Component>>;
+  return function Deferred(props: ComponentProps<Component>) {
+    return <Suspense fallback={<p className="ds-supporting-copy" role="status">Loading…</p>}><Surface {...props} /></Suspense>;
+  };
+}
diff --git a/src/index.ts b/src/index.ts
index 1eca478..1950e14 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,3 +1,4 @@
+import { browserFont } from "./browser-fonts";
 import { startReminders } from "./reminders/worker";
 import { backupConfig, startBackups } from "./ops/backups";
 import { databasePath } from "./db/config";
@@ -29,6 +30,7 @@ const server = Bun.serve({
   hostname: process.env.HOST ?? "127.0.0.1",
   port: Number(process.env.PORT ?? 3000),
   routes: {
+    "/fonts/browser/*": browserFont,
     "/api": req => app.fetch(req),
     "/api/*": req => app.fetch(req),
     "/*": index,
diff --git a/src/lib/dashboard.ts b/src/lib/dashboard.ts
index 40c8002..2090659 100644
--- a/src/lib/dashboard.ts
+++ b/src/lib/dashboard.ts
@@ -46,3 +46,15 @@ export function formatTrackingDate(date: string) {
     timeZone: "UTC",
   });
 }
+
+/** Preserve unchanged row references when a background refresh returns new JSON objects. */
+export function reconcileToday(current: TodayResponse | null, next: TodayResponse): TodayResponse {
+  if (!current || current.date !== next.date || current.timezone !== next.timezone) return next;
+  const previous = new Map(current.habits.map(habit => [habit.habitId, habit]));
+  const habits = next.habits.map(habit => {
+    const old = previous.get(habit.habitId);
+    return old && JSON.stringify(old) === JSON.stringify(habit) ? old : habit;
+  });
+  if (current.due === next.due && current.completed === next.completed && habits.length === current.habits.length && habits.every((habit, index) => habit === current.habits[index])) return current;
+  return { ...next, habits };
+}
diff --git a/src/pages/Home.tsx b/src/pages/Home.tsx
index d1e62e7..3c05aa9 100644
--- a/src/pages/Home.tsx
+++ b/src/pages/Home.tsx
@@ -1,7 +1,9 @@
+import { deferred } from "../components/design-system/deferred";
+import { CalendarCacheProvider } from "../components/CalendarCache";
 import { Archive, Plus, Settings2 } from "lucide-react";
-import { ArchivedHabits } from "../components/ArchivedHabits";
-import { AccountSettings } from "../components/AccountSettings";
-import { useCallback, useEffect, useRef, useState } from "react";
+const ArchivedHabits = deferred(() => import("../components/ArchivedHabits").then(module => module.ArchivedHabits));
+const AccountSettings = deferred(() => import("../components/AccountSettings").then(module => module.AccountSettings));
+import { memo, useCallback, useEffect, useRef, useState } from "react";
 import { useAuth } from "../components/AuthProvider";
 import { DiscordSignInButton } from "../components/DiscordSignInButton";
 import { PageLayout } from "../components/design-system/PageLayout";
@@ -15,17 +17,17 @@ import {
 import { Card, CardGrid } from "../components/design-system/Card";
 import { HabitChart } from "../components/design-system/HabitChart";
 import { HABIT_COLORS } from "../components/design-system/calendar-model";
-import { HabitForm } from "../components/HabitForm";
-import { habitRequest, scheduleLabel, type TodayHabit, type TodayResponse } from "../lib/dashboard";
+const HabitForm = deferred(() => import("../components/HabitForm").then(module => module.HabitForm));
+import { habitRequest, reconcileToday, scheduleLabel, type TodayHabit, type TodayResponse } from "../lib/dashboard";
 import { HabitHistory } from "../components/HabitHistory";
 import { WelcomePanel } from "../components/design-system/WelcomePanel";
 import type { PublicUser } from "../shared/user";
 import { ItemActions } from "../components/design-system/ItemActions";
 import { type ItemMode } from "../components/InlineItemForm";
-import { InlineHabitEditor } from "../components/InlineHabitEditor";
-import { InlineTaskEditor } from "../components/InlineTaskEditor";
+const InlineHabitEditor = deferred(() => import("../components/InlineHabitEditor").then(module => module.InlineHabitEditor));
+const InlineTaskEditor = deferred(() => import("../components/InlineTaskEditor").then(module => module.InlineTaskEditor));
 import type { Schedule } from "../habits/contracts";
-import { ShareProgress } from "../components/ShareProgress";
+const ShareProgress = deferred(() => import("../components/ShareProgress").then(module => module.ShareProgress));
 
 export function Home() {
   const { user, loading, busy, error, accountError, signIn, signOut, retry } = useAuth();
@@ -63,7 +65,7 @@ export function Home() {
           </Card>
         </section>
       ) : user ? (
-        <Dashboard key={user.id} user={user} onExpired={retry} />
+        <CalendarCacheProvider key={`${user.id}:${user.timezone}`}><Dashboard user={user} onExpired={retry} /></CalendarCacheProvider>
       ) : (
         <Welcome onSignIn={signIn} />
       )}
@@ -161,9 +163,10 @@ function Welcome({ onSignIn }: { onSignIn: () => void }) {
 
 function Dashboard({ user, onExpired }: { user: PublicUser; onExpired: () => void }) {
   const [today, setToday] = useState<TodayResponse | null>(null);
+  const todaySnapshot = useRef(today);
+  todaySnapshot.current = today;
   const [error, setError] = useState("");
   const [revision, setRevision] = useState(0);
-  const [calendarRevision, setCalendarRevision] = useState(0);
   const [habitRevisions, setHabitRevisions] = useState<Record<string, number>>({});
   const [pendingHabits, setPendingHabits] = useState<Set<string>>(new Set());
   const progressSaves = useRef(new Set<string>());
@@ -203,10 +206,10 @@ function Dashboard({ user, onExpired }: { user: PublicUser; onExpired: () => voi
     habitRequest<TodayResponse>("/today", { signal: controller.signal })
       .then((data) => {
         if (!controller.signal.aborted) {
-          setToday(data);
+          const next = reconcileToday(todaySnapshot.current, data);
+          setToday(next);
           setNeedsRefresh(false);
-          setRevision((value) => value + 1);
-          setCalendarRevision((value) => value + 1);
+          if (next !== todaySnapshot.current) setRevision((value) => value + 1);
         }
       })
       .catch((error) => {
@@ -302,7 +305,7 @@ function Dashboard({ user, onExpired }: { user: PublicUser; onExpired: () => voi
       try {
         const refreshed = await habitRequest<TodayResponse>("/today");
         if (mounted.current) {
-          setToday(refreshed);
+          setToday(current => reconcileToday(current, refreshed));
           // Keep a habit reachable when an edit makes it unscheduled (including an empty routine).
           if (refreshed.habits.some(item => item.habitId === habit.habitId && !item.due)) setHabitView("all");
           setNeedsRefresh(false);
@@ -337,6 +340,13 @@ function Dashboard({ user, onExpired }: { user: PublicUser; onExpired: () => voi
     }
   }
 
+  const actions = useRef({ update, manage });
+  actions.current = { update, manage };
+  const updateHabit = useCallback((...args: Parameters<typeof update>) => actions.current.update(...args), []);
+  const manageHabit = useCallback((...args: Parameters<typeof manage>) => actions.current.manage(...args), []);
+  const refreshHistory = useCallback(() => setAttempt(value => value + 1), []);
+  const expire = useCallback(() => expired.current(), []);
+
   return (
     <>
       <WelcomePanel
@@ -457,12 +467,12 @@ function Dashboard({ user, onExpired }: { user: PublicUser; onExpired: () => voi
                     key={habit.habitId}
                     habit={habit}
                     date={today.date}
-                    revision={calendarRevision + (habitRevisions[habit.habitId] ?? 0)}
+                    revision={habit.calendarRevision ?? habitRevisions[habit.habitId] ?? 0}
                     disabled={busy || pendingHabits.has(habit.habitId) || loading || needsRefresh}
-                    onHistorySaved={() => setAttempt(value => value + 1)}
-                    onUpdate={update}
-                    onManage={manage}
-                    onExpired={() => expired.current()}
+                    onHistorySaved={refreshHistory}
+                    onUpdate={updateHabit}
+                    onManage={manageHabit}
+                    onExpired={expire}
                   />
                 ))}
               </div>
@@ -474,7 +484,7 @@ function Dashboard({ user, onExpired }: { user: PublicUser; onExpired: () => voi
   );
 }
 
-function SavedHabit({
+const SavedHabit = memo(function SavedHabit({
   habit,
   date,
   revision,
@@ -604,7 +614,7 @@ function SavedHabit({
       ) : undefined}
     </HabitHistory>
   );
-}
+});
 
 function SavedTask({
   task,
diff --git a/styles/design-system.css b/styles/design-system.css
index c77d15b..ac3aed5 100644
--- a/styles/design-system.css
+++ b/styles/design-system.css
@@ -1,34 +1,34 @@
 @font-face {
   font-family: "Mina Sans";
-  src: url("../src/assets/fonts/NotoSans-Regular.ttf") format("truetype");
+  src: url("/fonts/browser/NotoSans-Regular.woff2") format("woff2");
   font-style: normal;
   font-weight: 400;
   font-display: swap;
 }
 @font-face {
   font-family: "Mina Sans";
-  src: url("../src/assets/fonts/NotoSans-Medium.ttf") format("truetype");
+  src: url("/fonts/browser/NotoSans-Medium.woff2") format("woff2");
   font-style: normal;
   font-weight: 500;
   font-display: swap;
 }
 @font-face {
   font-family: "Mina Sans";
-  src: url("../src/assets/fonts/NotoSans-SemiBold.ttf") format("truetype");
+  src: url("/fonts/browser/NotoSans-SemiBold.woff2") format("woff2");
   font-style: normal;
   font-weight: 600;
   font-display: swap;
 }
 @font-face {
   font-family: "Instrument Serif";
-  src: url("../src/assets/fonts/InstrumentSerif-Regular.ttf") format("truetype");
+  src: url("/fonts/browser/InstrumentSerif-Regular.woff2") format("woff2");
   font-weight: 400;
   font-style: normal;
   font-display: swap;
 }
 @font-face {
   font-family: "Instrument Serif";
-  src: url("../src/assets/fonts/InstrumentSerif-Italic.ttf") format("truetype");
+  src: url("/fonts/browser/InstrumentSerif-Italic.woff2") format("woff2");
   font-weight: 400;
   font-style: italic;
   font-display: swap;