diff --git a/admin/src/api/history.ts b/admin/src/api/history.ts
index 17cb902..eeecda8 100644
--- a/admin/src/api/history.ts
+++ b/admin/src/api/history.ts
@@ -3,7 +3,7 @@
  * append-only event log over a closed due-date range for one filter.
  */
 import { apiFetch } from "./client";
-import { readJson } from "./definitions";
+import { ApiRequestError, readJson } from "./definitions";
 
 export type HistoryFilter = "all" | "reversals" | "missed";
 
@@ -46,3 +46,40 @@ export async function fetchHistory(
   const params = new URLSearchParams({ start, end, filter });
   return readJson<HistoryResponse>(await apiFetch(`${HISTORY_PATH}?${params.toString()}`));
 }
+
+export const HISTORY_CSV_PATH = "/api/v1/admin/history.csv";
+
+export interface HistoryCsv {
+  blob: Blob;
+  filename: string;
+}
+
+/** The `filename` from a Content-Disposition header, or null. */
+export function csvFilename(disposition: string | null): string | null {
+  const match = disposition?.match(/filename="?([^";]+)"?/i);
+  return match ? match[1].trim() : null;
+}
+
+/**
+ * The CSV export of the same range and filter as `fetchHistory`. Goes through
+ * apiFetch so the admin token travels in the Authorization header.
+ */
+export async function exportHistoryCsv(
+  filter: HistoryFilter,
+  start: string,
+  end: string,
+): Promise<HistoryCsv> {
+  const params = new URLSearchParams({ start, end, filter });
+  const response = await apiFetch(`${HISTORY_CSV_PATH}?${params.toString()}`);
+  if (!response.ok) {
+    // readJson raises ApiRequestError with the API's `detail` for a non-OK response.
+    await readJson<never>(response);
+    throw new ApiRequestError(response.status, null);
+  }
+  return {
+    blob: await response.blob(),
+    filename:
+      csvFilename(response.headers.get("Content-Disposition")) ??
+      `nestquest-history-${start}-to-${end}.csv`,
+  };
+}
diff --git a/admin/src/history/HistoryTab.css b/admin/src/history/HistoryTab.css
index 5969554..d362b9b 100644
--- a/admin/src/history/HistoryTab.css
+++ b/admin/src/history/HistoryTab.css
@@ -48,6 +48,37 @@
   cursor: pointer;
 }
 
+.history-csv:disabled {
+  cursor: progress;
+  opacity: 0.6;
+}
+
+/* Non-blocking CSV export failure; the tab stays usable. */
+.history-export-error {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  gap: 10px;
+  padding: var(--nq-a-density-row-pad);
+  border-radius: var(--nq-a-density-radius);
+  background: var(--nq-a-danger-bg);
+  color: var(--nq-a-danger-strong);
+  font-size: 13px;
+  font-weight: 600;
+}
+
+.history-export-dismiss {
+  flex: none;
+  padding: 4px 8px;
+  border: none;
+  background: none;
+  color: inherit;
+  font-family: inherit;
+  font-size: 12.5px;
+  font-weight: 700;
+  cursor: pointer;
+}
+
 /* Scroll column: 14px 16px, bottom 92px (set inline, ADMIN-SPEC §1). */
 .history-scroll {
   display: flex;
diff --git a/admin/src/history/HistoryTab.test.tsx b/admin/src/history/HistoryTab.test.tsx
index 07a2344..a828e09 100644
--- a/admin/src/history/HistoryTab.test.tsx
+++ b/admin/src/history/HistoryTab.test.tsx
@@ -93,8 +93,27 @@ function jsonResponse(body: unknown, status = 200): Response {
   });
 }
 
+const CSV_BODY = "occurred_at,event_type\n2026-09-23T14:04:00Z,completed\n";
+
+function csvResponse(filter: string, start: string, end: string): Response {
+  return new Response(`${filter}\n${CSV_BODY}`, {
+    status: 200,
+    headers: {
+      "Content-Type": "text/csv; charset=utf-8",
+      "Content-Disposition": `attachment; filename="nestquest-history-${start}-to-${end}.csv"`,
+    },
+  });
+}
+
 function routeFetch(url: string): Response {
   const parsed = new URL(url, "http://x");
+  if (parsed.pathname.endsWith("/api/v1/admin/history.csv")) {
+    return csvResponse(
+      parsed.searchParams.get("filter") ?? "",
+      parsed.searchParams.get("start") ?? "",
+      parsed.searchParams.get("end") ?? "",
+    );
+  }
   if (!parsed.pathname.endsWith("/api/v1/admin/history")) {
     return jsonResponse({ detail: "unexpected" }, 500);
   }
@@ -229,15 +248,153 @@ describe("HistoryTab", () => {
     expect(screen.getAllByTestId("history-row")).toHaveLength(5);
   });
 
-  it("shows the append-only footer and an inert CSV button", async () => {
+  it("shows the append-only footer", async () => {
     await renderReady();
     expect(FOOTER_NOTE).toBe("Events are never edited or deleted. A reversal is its own row.");
     expect(screen.getByTestId("history-footer").textContent).toBe(FOOTER_NOTE);
+  });
 
-    const csv = screen.getByRole("button", { name: "CSV" });
-    const before = fetchMock.mock.calls.length;
-    fireEvent.click(csv);
-    expect(fetchMock.mock.calls.length).toBe(before);
+  describe("CSV export", () => {
+    let createObjectURL: ReturnType<typeof vi.fn>;
+    let revokeObjectURL: ReturnType<typeof vi.fn>;
+    let clicked: { href: string; download: string; attached: boolean }[];
+
+    beforeEach(() => {
+      createObjectURL = vi.fn(() => "blob:nestquest/csv-1");
+      revokeObjectURL = vi.fn();
+      // jsdom has no object URLs; install stubs and remove them afterwards.
+      Object.assign(URL, { createObjectURL, revokeObjectURL });
+      clicked = [];
+      vi.spyOn(HTMLAnchorElement.prototype, "click").mockImplementation(function (this: HTMLAnchorElement) {
+        clicked.push({
+          href: this.getAttribute("href") ?? "",
+          download: this.download,
+          attached: document.body.contains(this),
+        });
+      });
+    });
+
+    afterEach(() => {
+      vi.restoreAllMocks();
+      const stubbed = URL as unknown as Record<string, unknown>;
+      delete stubbed.createObjectURL;
+      delete stubbed.revokeObjectURL;
+    });
+
+    function csvCalls(): [URL, RequestInit][] {
+      return fetchMock.mock.calls
+        .map(([url, init]) => [new URL(String(url), "http://x"), init] as [URL, RequestInit])
+        .filter(([url]) => url.pathname === "/api/v1/admin/history.csv");
+    }
+
+    it("requests the CSV for the active filter and displayed range with the Bearer token", async () => {
+      await renderReady();
+      fireEvent.click(screen.getByRole("button", { name: "CSV" }));
+      await waitFor(() => expect(clicked).toHaveLength(1));
+
+      const calls = csvCalls();
+      expect(calls).toHaveLength(1);
+      const [url, init] = calls[0];
+      expect(url.searchParams.get("filter")).toBe("all");
+      expect(url.searchParams.get("start")).toBe("2026-09-10");
+      expect(url.searchParams.get("end")).toBe(TODAY);
+      expect((init.headers as Record<string, string>).Authorization).toBe("Bearer at-123");
+      // The token never travels in the URL.
+      expect(url.toString()).not.toContain("at-123");
+    });
+
+    it("offers the returned CSV for download, then revokes the URL and removes the anchor", async () => {
+      await renderReady();
+      fireEvent.click(screen.getByRole("button", { name: "CSV" }));
+      await waitFor(() => expect(clicked).toHaveLength(1));
+
+      expect(createObjectURL).toHaveBeenCalledTimes(1);
+      const blob = createObjectURL.mock.calls[0][0] as Blob;
+      expect(await blob.text()).toBe(`all\n${CSV_BODY}`);
+      expect(clicked[0]).toEqual({
+        href: "blob:nestquest/csv-1",
+        download: "nestquest-history-2026-09-10-to-2026-09-23.csv",
+        attached: true,
+      });
+      expect(revokeObjectURL).toHaveBeenCalledWith("blob:nestquest/csv-1");
+      expect(document.querySelector("a[download]")).toBeNull();
+      expect(screen.queryByTestId("history-export-error")).toBeNull();
+    });
+
+    it("falls back to the range filename without a Content-Disposition header", async () => {
+      fetchMock.mockImplementation((url: string) =>
+        Promise.resolve(
+          new URL(url, "http://x").pathname.endsWith(".csv")
+            ? new Response(CSV_BODY, { status: 200, headers: { "Content-Type": "text/csv" } })
+            : routeFetch(url),
+        ),
+      );
+      await renderReady();
+      fireEvent.click(screen.getByRole("button", { name: "CSV" }));
+      await waitFor(() => expect(clicked).toHaveLength(1));
+      expect(clicked[0].download).toBe("nestquest-history-2026-09-10-to-2026-09-23.csv");
+    });
+
+    it("switching the filter chip then exporting uses the new filter", async () => {
+      await renderReady();
+      fireEvent.click(screen.getByRole("button", { name: "Reversals" }));
+      await waitFor(() => expect(screen.getAllByTestId("history-row")).toHaveLength(1));
+
+      fireEvent.click(screen.getByRole("button", { name: "CSV" }));
+      await waitFor(() => expect(clicked).toHaveLength(1));
+      const calls = csvCalls();
+      expect(calls).toHaveLength(1);
+      expect(calls[0][0].searchParams.get("filter")).toBe("reversals");
+      expect(calls[0][0].searchParams.get("start")).toBe("2026-09-10");
+      expect(calls[0][0].searchParams.get("end")).toBe(TODAY);
+    });
+
+    it("a failed export shows a non-blocking error and does not download", async () => {
+      fetchMock.mockImplementation((url: string) =>
+        Promise.resolve(
+          new URL(url, "http://x").pathname.endsWith(".csv")
+            ? jsonResponse({ detail: "boom" }, 500)
+            : routeFetch(url),
+        ),
+      );
+      await renderReady();
+      fireEvent.click(screen.getByRole("button", { name: "CSV" }));
+
+      const error = await screen.findByTestId("history-export-error");
+      expect(error.textContent).toContain("The CSV export failed");
+      expect(createObjectURL).not.toHaveBeenCalled();
+      expect(clicked).toHaveLength(0);
+      // The tab stays usable: rows remain, the button is re-enabled, chips still work.
+      expect(screen.getAllByTestId("history-row")).toHaveLength(5);
+      expect((screen.getByRole("button", { name: "CSV" }) as HTMLButtonElement).disabled).toBe(false);
+      fireEvent.click(screen.getByRole("button", { name: "Reversals" }));
+      await waitFor(() => expect(screen.getAllByTestId("history-row")).toHaveLength(1));
+
+      fireEvent.click(within(error).getByRole("button", { name: "Dismiss" }));
+      expect(screen.queryByTestId("history-export-error")).toBeNull();
+    });
+
+    it("the button is disabled while the request is in flight (no double-submit)", async () => {
+      let release: (response: Response) => void = () => {};
+      fetchMock.mockImplementation((url: string) =>
+        new URL(url, "http://x").pathname.endsWith(".csv")
+          ? new Promise<Response>((resolve) => {
+              release = resolve;
+            })
+          : Promise.resolve(routeFetch(url)),
+      );
+      await renderReady();
+      const csv = screen.getByRole("button", { name: "CSV" }) as HTMLButtonElement;
+      fireEvent.click(csv);
+      await waitFor(() => expect(csv.disabled).toBe(true));
+      fireEvent.click(csv);
+      expect(csvCalls()).toHaveLength(1);
+
+      release(csvResponse("all", "2026-09-10", TODAY));
+      await waitFor(() => expect(clicked).toHaveLength(1));
+      await waitFor(() => expect(csv.disabled).toBe(false));
+      expect(csvCalls()).toHaveLength(1);
+    });
   });
 
   it("rows are read-only: no row carries a control", async () => {
diff --git a/admin/src/history/HistoryTab.tsx b/admin/src/history/HistoryTab.tsx
index 093f0bb..f929166 100644
--- a/admin/src/history/HistoryTab.tsx
+++ b/admin/src/history/HistoryTab.tsx
@@ -4,9 +4,9 @@
  * Rows are read-only: events are never edited or deleted, and a reversal is
  * its own row (D-005).
  */
-import { useEffect, useState } from "react";
+import { useEffect, useRef, useState } from "react";
 import { ApiForbiddenError } from "../api/client";
-import { fetchHistory, type HistoryFilter, type HistoryRow } from "../api/history";
+import { exportHistoryCsv, fetchHistory, type HistoryFilter, type HistoryRow } from "../api/history";
 import { localTodayIso } from "../schedule/cycle";
 import { dayLabel, groupByDay, rowMeta, rowTime, shiftIso } from "./format";
 import { DownloadGlyph, LockGlyph } from "./glyphs";
@@ -70,15 +70,37 @@ async function loadHistory(filter: HistoryFilter, start: string, end: string): P
   };
 }
 
-function ScreenHeader() {
+/** Offer a Blob as a file download without navigating the page. */
+export function offerDownload(blob: Blob, filename: string): void {
+  const url = URL.createObjectURL(blob);
+  const anchor = document.createElement("a");
+  anchor.href = url;
+  anchor.download = filename;
+  anchor.style.display = "none";
+  document.body.appendChild(anchor);
+  try {
+    anchor.click();
+  } finally {
+    anchor.remove();
+    URL.revokeObjectURL(url);
+  }
+}
+
+function ScreenHeader({ exporting, onExport }: { exporting: boolean; onExport: () => void }) {
   return (
     <header className="history-header">
       <div>
         <h2 className="history-title">History</h2>
         <p className="history-sub">Append-only event log · last {RANGE_DAYS} days</p>
       </div>
-      {/* TODO(e5133d0f): export the filtered range as CSV; inert until then. */}
-      <button type="button" className="history-csv" data-testid="history-csv">
+      <button
+        type="button"
+        className="history-csv"
+        data-testid="history-csv"
+        disabled={exporting}
+        aria-busy={exporting}
+        onClick={onExport}
+      >
         <DownloadGlyph />
         CSV
       </button>
@@ -140,8 +162,32 @@ export default function HistoryTab({ today = localTodayIso() }: { today?: string
   const [filter, setFilter] = useState<HistoryFilter>("all");
   const [state, setState] = useState<LoadState>({ kind: "loading" });
   const [attempt, setAttempt] = useState(0);
+  const [exporting, setExporting] = useState(false);
+  const [exportError, setExportError] = useState<string | null>(null);
+  const exportingRef = useRef(false);
   const start = shiftIso(today, -(RANGE_DAYS - 1));
 
+  /** Download the CSV for the active filter over the displayed range. */
+  async function exportCsv() {
+    if (exportingRef.current) return;
+    exportingRef.current = true;
+    setExporting(true);
+    setExportError(null);
+    try {
+      const { blob, filename } = await exportHistoryCsv(filter, start, today);
+      offerDownload(blob, filename);
+    } catch (error: unknown) {
+      setExportError(
+        error instanceof ApiForbiddenError
+          ? error.message
+          : "The CSV export failed. Check your connection and try again.",
+      );
+    } finally {
+      exportingRef.current = false;
+      setExporting(false);
+    }
+  }
+
   useEffect(() => {
     let cancelled = false;
     setState({ kind: "loading" });
@@ -199,12 +245,20 @@ export default function HistoryTab({ today = localTodayIso() }: { today?: string
 
   return (
     <div className="history-screen">
-      <ScreenHeader />
+      <ScreenHeader exporting={exporting} onExport={() => void exportCsv()} />
       <div
         className="history-scroll"
         data-testid="history-scroll"
         style={{ paddingBottom: SCROLL_BOTTOM_PADDING }}
       >
+        {exportError !== null ? (
+          <div className="history-export-error" role="alert" data-testid="history-export-error">
+            <span>{exportError}</span>
+            <button type="button" className="history-export-dismiss" onClick={() => setExportError(null)}>
+              Dismiss
+            </button>
+          </div>
+        ) : null}
         {state.kind === "ready" ? <StatRow stats={state.data.stats} /> : null}
         <div className="history-chips" role="group" aria-label="Filter events">
           {FILTERS.map((item) => (