short circuit getCandles if a negative cache exists

src/service.zig

@@ -826,6 +826,17 @@ pub const DataService = struct {
     /// `opts.force_refresh = true` -> treats cache as stale and fetches.
     pub fn getCandles(self: *DataService, symbol: []const u8, opts: FetchOptions) DataError!FetchResult(Candle) {
         var s = self.store();
+
+        // Negative cache: this symbol is known to have no candle data on
+        // any provider (e.g. crypto like DOGE-USD that Tiingo can't
+        // serve). The marker lives in candles_daily.srf - written by the
+        // permanent-NotFound path below, or synced verbatim from a
+        // ZFIN_SERVER. Bail before any server sync or provider fetch so
+        // repeated calls don't re-hit the network every invocation.
+        // --refresh-data=force (force_refresh) bypasses this to retry.
+        if (!opts.force_refresh and s.isNegative(symbol, .candles_daily))
+            return DataError.FetchFailed;
+
         const today = fmt.todayDate(self.io);
 
         // wall-clock required: candle-meta freshness uses a market-aware
@@ -3340,6 +3351,32 @@ test "loadLiveQuotes: empty symbol list returns empty without touching the netwo
     try std.testing.expectEqual(@as(usize, 0), prices.count());
 }
 
+test "getCandles: negative candle cache short-circuits without touching the network" {
+    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, .{ .cache_dir = dir_path });
+    defer svc.deinit();
+
+    // Seed a negative candle entry: this symbol has no candle data on
+    // any provider (the crypto / defunct-ticker case). The marker lives
+    // in candles_daily.srf; candles_meta.srf is never created.
+    var s = svc.store();
+    try s.ensureSymbolDir("DOGE-USD");
+    s.writeNegative("DOGE-USD", .candles_daily);
+
+    // Any server sync or provider fetch would trip this panic guard.
+    svc.panic_on_network_attempt = true;
+
+    // getCandles must recognize the negative entry and fail fast, with
+    // no network round-trip (no panic).
+    try std.testing.expectError(DataError.FetchFailed, svc.getCandles("DOGE-USD", .{}));
+}
+
 test "DataService store helper creates valid store" {
     const allocator = std.testing.allocator;
     const config = Config{