diff --git a/src/api/client.ts b/src/api/client.ts
index b6e59df..c1ad8d8 100644
--- a/src/api/client.ts
+++ b/src/api/client.ts
@@ -97,7 +97,7 @@ function statsRegionParams(r: StatsRegion): { iatas?: string; region?: string }
 
 export function getPackets(
   iatas: string[] | undefined,
-  params?: { cursor?: number; limit?: number; payloadTypes?: number[]; routeTypes?: number[]; scopes?: string[] },
+  params?: { cursor?: number; limit?: number; payloadTypes?: number[]; routeTypes?: number[]; scopes?: string[]; hashPrefix?: string },
 ): Promise<CursorPage<PacketSummary>> {
   if (noIatas(iatas)) return Promise.resolve(emptyPage());
   return request("/packets", {
@@ -107,6 +107,7 @@ export function getPackets(
     payloadTypes: params?.payloadTypes?.length ? params.payloadTypes.join(",") : undefined,
     routeTypes: params?.routeTypes?.length ? params.routeTypes.join(",") : undefined,
     scopes: params?.scopes?.length ? params.scopes.join(",") : undefined,
+    hashPrefix: params?.hashPrefix,
   });
 }
 
diff --git a/src/components/SearchBar.tsx b/src/components/SearchBar.tsx
index 139a9cf..7e06337 100644
--- a/src/components/SearchBar.tsx
+++ b/src/components/SearchBar.tsx
@@ -50,6 +50,12 @@ export function SearchBar({ value, onChange, fields, field, onFieldChange, hideF
   function handleChange(val: string) {
     setLocalValue(val);
     if (debounceRef.current) clearTimeout(debounceRef.current);
+    // clearing should restore the full list right away
+    if (val === "") {
+      debounceRef.current = null;
+      onChange(val);
+      return;
+    }
     debounceRef.current = setTimeout(() => {
       onChange(val);
     }, 300);
diff --git a/src/features/packets/types.ts b/src/features/packets/types.ts
index 351f9ac..47647bf 100644
--- a/src/features/packets/types.ts
+++ b/src/features/packets/types.ts
@@ -16,6 +16,7 @@ export interface PacketServerFilter {
   payloadTypes?: number[];
   routeTypes?: number[];
   scopes?: string[];
+  hashPrefix?: string;
 }
 
 export const EMPTY_FILTERS: PacketFilterState = {
diff --git a/src/features/packets/usePacketFilters.ts b/src/features/packets/usePacketFilters.ts
index 9cc46c7..a968818 100644
--- a/src/features/packets/usePacketFilters.ts
+++ b/src/features/packets/usePacketFilters.ts
@@ -118,11 +118,18 @@ export function usePacketFilters() {
 // The /packets endpoint accepts comma-separated payloadTypes/routeTypes/scopes, so any selected
 // dimension goes server-side and pagination pulls the correctly-filtered set from the full history.
 // (observers has no server param, so it stays client-side in matchesFilters, as does the live buffer.)
+// A 4-16 char hex hash search also goes server-side so older packets can be found.
+const HASH_PREFIX_RE = /^[0-9a-f]{4,16}$/i;
+
 export function toServerFilter(filters: PacketFilterState): PacketServerFilter | null {
   const serverFilter: PacketServerFilter = {};
   if (filters.payloadTypes.length > 0) serverFilter.payloadTypes = filters.payloadTypes;
   if (filters.routeTypes.length > 0) serverFilter.routeTypes = filters.routeTypes;
   if (filters.scopes.length > 0) serverFilter.scopes = filters.scopes;
+  const hashSearch = filters.search.trim();
+  if (filters.searchField === "hash" && HASH_PREFIX_RE.test(hashSearch)) {
+    serverFilter.hashPrefix = hashSearch.toLowerCase();
+  }
   return Object.keys(serverFilter).length > 0 ? serverFilter : null;
 }
 
@@ -151,7 +158,7 @@ export function matchesFilters(
     return false;
   }
   if (filters.search && filters.searchField === "hash") {
-    const q = filters.search.toLowerCase();
+    const q = filters.search.trim().toLowerCase();
     if (!packet.packetHash.toLowerCase().includes(q)) {
       return false;
     }
diff --git a/tests/api/client.test.ts b/tests/api/client.test.ts
index a637077..c92cbe5 100644
--- a/tests/api/client.test.ts
+++ b/tests/api/client.test.ts
@@ -51,6 +51,15 @@ describe("getPackets", () => {
     expect(url.searchParams.has("scopes")).toBe(false);
     expect(url.searchParams.get("cursor")).toBe("100");
     expect(url.searchParams.get("limit")).toBe("50");
+    expect(url.searchParams.has("hashPrefix")).toBe(false);
+  });
+
+  it("forwards hashPrefix", async () => {
+    const getUrl = mockFetchOnce({ items: [], nextCursor: null, hasMore: false });
+
+    await getPackets(["YOW"], { hashPrefix: "6ddf62" });
+
+    expect(new URL(getUrl()).searchParams.get("hashPrefix")).toBe("6ddf62");
   });
 });
 
diff --git a/tests/components/SearchBar.compact.test.tsx b/tests/components/SearchBar.compact.test.tsx
index 2d56d21..21e6e4f 100644
--- a/tests/components/SearchBar.compact.test.tsx
+++ b/tests/components/SearchBar.compact.test.tsx
@@ -18,3 +18,17 @@ describe("compact observer search", () => {
     } finally { vi.useRealTimers(); }
   });
 });
+
+describe("clearing the search", () => {
+  it("reports an emptied box immediately instead of waiting out the debounce", () => {
+    vi.useFakeTimers();
+    try {
+      const change = vi.fn();
+      render(<SearchBar value="abcd" onChange={change} fields={[{ value: "hash", label: "Hash" }]} field="hash" onFieldChange={() => {}} hideField inputLabel="Search" />);
+      fireEvent.change(screen.getByRole("textbox", { name: "Search" }), { target: { value: "" } });
+      expect(change).toHaveBeenCalledExactlyOnceWith("");
+      act(() => vi.advanceTimersByTime(300));
+      expect(change).toHaveBeenCalledOnce();
+    } finally { vi.useRealTimers(); }
+  });
+});
diff --git a/tests/features/packets/PacketList.test.tsx b/tests/features/packets/PacketList.test.tsx
index 6601562..06f1405 100644
--- a/tests/features/packets/PacketList.test.tsx
+++ b/tests/features/packets/PacketList.test.tsx
@@ -1,5 +1,5 @@
 import { describe, it, expect, vi, afterEach } from "vitest";
-import { render, screen, fireEvent, within } from "@testing-library/react";
+import { render, screen, fireEvent, within, act } from "@testing-library/react";
 import { MemoryRouter } from "react-router-dom";
 import { QueryClient, QueryClientProvider } from "@tanstack/react-query";
 import { PacketList } from "../../../src/features/packets/PacketList";
@@ -367,6 +367,34 @@ describe("PacketList selected packet outside the loaded results", () => {
   });
 });
 
+describe("PacketList hash search", () => {
+  afterEach(() => {
+    vi.useRealTimers();
+    usePackets.mockImplementation(basePackets);
+  });
+
+  it("sends a typed hex hash search server-side once the search box settles", () => {
+    vi.useFakeTimers();
+    renderList();
+    fireEvent.change(screen.getByPlaceholderText("Search by hash..."), { target: { value: "6DDF" } });
+    expect(usePackets).toHaveBeenLastCalledWith(false, null);
+    act(() => { vi.runOnlyPendingTimers(); });
+    expect(usePackets).toHaveBeenLastCalledWith(false, { hashPrefix: "6ddf" });
+  });
+
+  it("starts with the URL's hash search already server-side", () => {
+    renderList("/?q=6ddf62");
+    expect(usePackets).toHaveBeenLastCalledWith(false, { hashPrefix: "6ddf62" });
+  });
+
+  it("still filters live packets client-side while a hash search is active", () => {
+    usePackets.mockImplementation(() => ({ ...basePackets(), allPackets: [packet("6ddf0001"), packet("aa110002")] }));
+    renderList("/?q=6ddf");
+    expect(screen.getByRole("button", { name: "6ddf0001" })).toBeInTheDocument();
+    expect(screen.queryByRole("button", { name: "aa110002" })).toBeNull();
+  });
+});
+
 describe("PacketList in French", () => {
   it("translates the banners and the selected-packet card", async () => {
     await i18n.changeLanguage("fr");
diff --git a/tests/features/packets/usePacketFilters.test.ts b/tests/features/packets/usePacketFilters.test.ts
index d6de664..3dca1d1 100644
--- a/tests/features/packets/usePacketFilters.test.ts
+++ b/tests/features/packets/usePacketFilters.test.ts
@@ -21,6 +21,13 @@ function pkt(over: Partial<PacketSummary>): PacketSummary {
   };
 }
 
+describe("matchesFilters — hash search", () => {
+  it("matches a trimmed, case-insensitive substring of the hash", () => {
+    expect(matchesFilters(pkt({ packetHash: "abcd1234" }), { ...EMPTY_FILTERS, search: " CD12 " })).toBe(true);
+    expect(matchesFilters(pkt({ packetHash: "abcd1234" }), { ...EMPTY_FILTERS, search: "ffff" })).toBe(false);
+  });
+});
+
 describe("matchesFilters — scope", () => {
   it("ignores scope when no scope filter is set", () => {
     expect(matchesFilters(pkt({ scope: "#bc" }), EMPTY_FILTERS)).toBe(true);
@@ -83,6 +90,23 @@ describe("toServerFilter", () => {
     expect(toServerFilter({ ...EMPTY_FILTERS, observers: ["o1"] })).toBeNull();
     expect(toServerFilter({ ...EMPTY_FILTERS, search: "ab" })).toBeNull();
   });
+
+  it.each(["abcd", "ABCDE", "6ddf62fb5b9a969e", " abcd "])("sends a %j hash search server-side as a trimmed lowercase hashPrefix", (search) => {
+    expect(toServerFilter({ ...EMPTY_FILTERS, search })).toEqual({ hashPrefix: search.trim().toLowerCase() });
+  });
+
+  it.each(["abc", "6ddf62fb5b9a969e0", "abcg", "ab cd"])("keeps the %j hash search client-side only", (search) => {
+    expect(toServerFilter({ ...EMPTY_FILTERS, search })).toBeNull();
+  });
+
+  it("never sends a path search as a hashPrefix", () => {
+    expect(toServerFilter({ ...EMPTY_FILTERS, search: "abcd", searchField: "path" })).toBeNull();
+  });
+
+  it("combines hashPrefix with the other server filters", () => {
+    expect(toServerFilter({ ...EMPTY_FILTERS, payloadTypes: [4] as PayloadTypeValue[], search: "abcd" }))
+      .toEqual({ payloadTypes: [4], hashPrefix: "abcd" });
+  });
 });
 
 function routerAt(url: string) {