diff --git a/src/commands/lookup.zig b/src/commands/lookup.zig
index 22af36b..f248639 100644
--- a/src/commands/lookup.zig
+++ b/src/commands/lookup.zig
@@ -53,6 +53,23 @@ pub fn run(ctx: *framework.RunCtx, parsed: ParsedArgs) !void {
         try cli.printFg(out, color, cli.CLR_MUTED, "Note: '{s}' doesn't look like a CUSIP (expected 9 alphanumeric chars with digits)\n", .{parsed.cusip});
     }
 
+    // L1: check the local cache before any network call. Hits are
+    // permanent (CUSIP->ticker mappings don't change), so a cached
+    // answer is authoritative and skips OpenFIGI entirely.
+    var cache_map = svc.loadCusipTickerMap(allocator);
+    defer cache_map.deinit();
+    if (cache_map.get(parsed.cusip)) |ticker| {
+        const cached: zfin.CusipResult = .{
+            .ticker = ticker,
+            .name = null,
+            .security_type = null,
+            .found = true,
+        };
+        try display(cached, parsed.cusip, color, out);
+        try cli.printFg(out, color, cli.CLR_MUTED, "  (from local cache)\n", .{});
+        return;
+    }
+
     cli.stderrPrint(ctx.io, "Looking up via OpenFIGI...\n");
 
     // Try full batch lookup for richer output
diff --git a/src/service.zig b/src/service.zig
index cfa2c0b..927f5b5 100644
--- a/src/service.zig
+++ b/src/service.zig
@@ -2398,13 +2398,104 @@ pub const DataService = struct {
         ticker: []const u8 = "",
     };
 
+    /// CUSIP->ticker lookup table loaded from `cusip_tickers.srf`.
+    ///
+    /// Zero-copy: keys and values are slices into `backing` (the raw
+    /// file bytes parsed with `parse_allocator = .none`). Nothing is
+    /// duped per entry — the whole-file buffer IS the storage, and it
+    /// stays alive for the table's lifetime, released together with
+    /// the map table in `deinit`.
+    ///
+    /// This is the L1 tier of CUSIP resolution: callers consult it
+    /// before reaching for the server or OpenFIGI.
+    pub const CusipTickerMap = struct {
+        map: std.StringHashMap([]const u8),
+        /// Raw bytes of `cusip_tickers.srf`; every map key and value
+        /// points into this buffer. `&.{}` when the file was missing
+        /// or unreadable (freeing a zero-length slice is a no-op).
+        backing: []const u8,
+
+        pub fn get(self: CusipTickerMap, cusip: []const u8) ?[]const u8 {
+            return self.map.get(cusip);
+        }
+
+        pub fn contains(self: CusipTickerMap, cusip: []const u8) bool {
+            return self.map.contains(cusip);
+        }
+
+        pub fn count(self: CusipTickerMap) u32 {
+            return self.map.count();
+        }
+
+        /// Release the map table and the backing buffer. Both were
+        /// allocated with the map's allocator at load time, so we
+        /// reuse it here — the two lifetimes are bound together by
+        /// construction, which is the whole point of the wrapper.
+        pub fn deinit(self: *CusipTickerMap) void {
+            const allocator = self.map.allocator;
+            self.map.deinit();
+            allocator.free(self.backing);
+        }
+    };
+
+    /// Load the CUSIP->ticker cache file into a `CusipTickerMap`. The
+    /// returned table owns the file bytes; release it with
+    /// `CusipTickerMap.deinit`.
+    ///
+    /// Missing file → empty table (the common first-run case). First
+    /// occurrence wins on duplicate CUSIPs, which tolerates the
+    /// historical double-append bug in cache files written before
+    /// `cacheCusipTicker` learned to dedup.
+    ///
+    /// The on-disk format is CUSIP-keyed (`cusip::X,ticker::Y`); the
+    /// returned map is keyed the same way for O(1) forward lookup.
+    pub fn loadCusipTickerMap(self: *DataService, allocator: std.mem.Allocator) CusipTickerMap {
+        const map = std.StringHashMap([]const u8).init(allocator);
+        const path = std.fs.path.join(allocator, &.{ self.config.cache_dir, "cusip_tickers.srf" }) catch
+            return .{ .map = map, .backing = &.{} };
+        defer allocator.free(path);
+
+        const data = std.Io.Dir.cwd().readFileAlloc(self.io, path, allocator, .limited(4 * 1024 * 1024)) catch
+            return .{ .map = map, .backing = &.{} };
+        // From here `data` is the table's backing store: keys and
+        // values are slices into it (parse_allocator = .none, so the
+        // parser borrows rather than copies). Freed by
+        // `CusipTickerMap.deinit`, never here — that's the lifetime
+        // contract that lets us skip per-entry dupes entirely.
+        var result: CusipTickerMap = .{ .map = map, .backing = data };
+
+        var reader = std.Io.Reader.fixed(data);
+        var it = srf.iterator(&reader, allocator, .{ .parse_allocator = .none }) catch return result;
+        defer it.deinit();
+
+        while (it.next() catch return result) |fields| {
+            const entry = fields.to(CusipEntry, .{}) catch continue;
+            if (entry.cusip.len == 0 or entry.ticker.len == 0) continue;
+            // First occurrence wins; getOrPut stores the borrowed
+            // slices directly — they live in `backing`, no dupe.
+            const gop = result.map.getOrPut(entry.cusip) catch continue;
+            if (!gop.found_existing) gop.value_ptr.* = entry.ticker;
+        }
+        return result;
+    }
+
     /// Append a CUSIP->ticker mapping to the cache file.
     ///
     /// Implemented as read-append-atomic-write (rather than a direct
     /// open-for-append) so a concurrent reader never sees a file with a
     /// valid header plus partial trailing record. See `cache/store.zig
     /// appendRaw` for the same pattern and rationale.
+    ///
+    /// Dedups: if the CUSIP is already cached, this is a no-op. That
+    /// keeps the file from accumulating duplicate rows when the same
+    /// CUSIP is looked up repeatedly (the historical bug — the writer
+    /// never checked the file before appending).
     pub fn cacheCusipTicker(self: *DataService, cusip: []const u8, ticker: []const u8) void {
+        // Dedup against what's already cached.
+        var existing_map = self.loadCusipTickerMap(self.allocator);
+        defer existing_map.deinit();
+        if (existing_map.contains(cusip)) return;
+
         const path = std.fs.path.join(self.allocator, &.{ self.config.cache_dir, "cusip_tickers.srf" }) catch return;
         defer self.allocator.free(path);
 
@@ -3778,3 +3869,106 @@ test "freeEdgarLookup: handles all three union variants without leak" {
     // testing.allocator panics on leak — passing this test means
     // the title was freed.
 }
+
+// ── CUSIP->ticker cache (loadCusipTickerMap / cacheCusipTicker) ──
+
+test "loadCusipTickerMap: missing file returns empty map" {
+    const allocator = std.testing.allocator;
+    const io = std.testing.io;
+    var tmp = std.testing.tmpDir(.{});
+    defer tmp.cleanup();
+    const dir_path = try tmp.dir.realPathFileAlloc(io, ".", allocator);
+    defer allocator.free(dir_path);
+
+    var svc = DataService.init(io, allocator, Config{ .cache_dir = dir_path });
+    defer svc.deinit();
+
+    var map = svc.loadCusipTickerMap(allocator);
+    defer map.deinit();
+    try std.testing.expectEqual(@as(usize, 0), map.count());
+}
+
+test "cacheCusipTicker + loadCusipTickerMap: write/read round-trip" {
+    const allocator = std.testing.allocator;
+    const io = std.testing.io;
+    var tmp = std.testing.tmpDir(.{});
+    defer tmp.cleanup();
+    const dir_path = try tmp.dir.realPathFileAlloc(io, ".", allocator);
+    defer allocator.free(dir_path);
+
+    var svc = DataService.init(io, allocator, Config{ .cache_dir = dir_path });
+    defer svc.deinit();
+
+    // Placeholder CUSIPs/tickers — never real PII.
+    svc.cacheCusipTicker("111111111", "AAA");
+    svc.cacheCusipTicker("222222222", "BBB");
+
+    var map = svc.loadCusipTickerMap(allocator);
+    defer map.deinit();
+    try std.testing.expectEqual(@as(usize, 2), map.count());
+    try std.testing.expectEqualStrings("AAA", map.get("111111111").?);
+    try std.testing.expectEqualStrings("BBB", map.get("222222222").?);
+}
+
+test "cacheCusipTicker: dedups repeated CUSIP (the historical bug)" {
+    const allocator = std.testing.allocator;
+    const io = std.testing.io;
+    var tmp = std.testing.tmpDir(.{});
+    defer tmp.cleanup();
+    const dir_path = try tmp.dir.realPathFileAlloc(io, ".", allocator);
+    defer allocator.free(dir_path);
+
+    var svc = DataService.init(io, allocator, Config{ .cache_dir = dir_path });
+    defer svc.deinit();
+
+    // Write the same CUSIP three times — must collapse to one row.
+    svc.cacheCusipTicker("111111111", "AAA");
+    svc.cacheCusipTicker("111111111", "AAA");
+    svc.cacheCusipTicker("111111111", "AAA");
+
+    var map = svc.loadCusipTickerMap(allocator);
+    defer map.deinit();
+    try std.testing.expectEqual(@as(usize, 1), map.count());
+    try std.testing.expectEqualStrings("AAA", map.get("111111111").?);
+
+    // The on-disk file should physically contain exactly one data
+    // row (plus the directive header), proving dedup at the writer.
+    const path = try std.fs.path.join(allocator, &.{ dir_path, "cusip_tickers.srf" });
+    defer allocator.free(path);
+    const data = try std.Io.Dir.cwd().readFileAlloc(io, path, allocator, .limited(64 * 1024));
+    defer allocator.free(data);
+    var row_count: usize = 0;
+    var lines = std.mem.splitScalar(u8, data, '\n');
+    while (lines.next()) |line| {
+        if (std.mem.indexOf(u8, line, "cusip::") != null) row_count += 1;
+    }
+    try std.testing.expectEqual(@as(usize, 1), row_count);
+}
+
+test "loadCusipTickerMap: first occurrence wins on duplicate rows" {
+    // Tolerate a pre-existing file written by the buggy appender
+    // (duplicate rows). The reader must not crash and must keep the
+    // first mapping.
+    const allocator = std.testing.allocator;
+    const io = std.testing.io;
+    var tmp = std.testing.tmpDir(.{});
+    defer tmp.cleanup();
+    const dir_path = try tmp.dir.realPathFileAlloc(io, ".", allocator);
+    defer allocator.free(dir_path);
+
+    // Hand-write a file with a duplicate row (as the old bug did).
+    const path = try std.fs.path.join(allocator, &.{ dir_path, "cusip_tickers.srf" });
+    defer allocator.free(path);
+    try std.Io.Dir.cwd().writeFile(io, .{
+        .sub_path = path,
+        .data = "#!srfv1\ncusip::111111111,ticker::AAA\ncusip::111111111,ticker::AAA\n",
+    });
+
+    var svc = DataService.init(io, allocator, Config{ .cache_dir = dir_path });
+    defer svc.deinit();
+
+    var map = svc.loadCusipTickerMap(allocator);
+    defer map.deinit();
+    try std.testing.expectEqual(@as(usize, 1), map.count());
+    try std.testing.expectEqualStrings("AAA", map.get("111111111").?);
+}