feat(market): parse is_block_trade on public trades

CHANGELOG.md

@@ -6,6 +6,24 @@ uses [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
 
+### Added
+
+- **REST**: `PublicTrade::is_block_trade` — parsed from `GET /markets/trades`
+  (Kalshi changelog 2026-05-29: public trade responses now flag block
+  trades and support filtering by block status). Block trades are large
+  negotiated prints routed off the central order book; exposing the flag
+  lets trade-flow / microstructure consumers exclude them. The field is
+  absent on older payloads and defaults to `false` (forward/backward
+  compatible — no behavioural change for existing consumers).
+
+### Changed
+
+- **Internal**: extracted the inline `GET /markets/trades` body parser out
+  of `KalshiClient::get_trades` into a testable
+  `api_detail::parse_trades_response`, matching the existing
+  `parse_deposits_response` / `parse_withdrawals_response` convention. Adds
+  unit coverage for trade parsing (incl. the new `is_block_trade` flag).
+
 ## [0.4.8] - 2026-05-19
 
 ### Fixed

include/kalshi/api.hpp

@@ -165,6 +165,10 @@ struct PublicTrade {
 	std::int32_t count{0};
 	Side taker_side{Side::Yes};
 	std::int64_t created_time{0};
+	/// True when the trade was executed as a block trade (large negotiated
+	/// print routed off the central order book). Kalshi added this field on
+	/// 2026-05-29; absent on older payloads → defaults to false.
+	bool is_block_trade{false};
 };
 
 // ===== Phase 1: Exchange API Models =====

src/api/client.cpp

@@ -921,6 +921,26 @@ std::vector<Withdrawal> parse_withdrawals_response(std::string_view body) {
 	return parse_portfolio_movements<Withdrawal>(body, "withdrawals");
 }
 
+std::vector<PublicTrade> parse_trades_response(std::string_view body) {
+	const std::string buf{body};
+	const std::vector<std::string> trade_objects = extract_array_objects(buf, "trades");
+	std::vector<PublicTrade> trades;
+	trades.reserve(trade_objects.size());
+	for (const std::string& obj : trade_objects) {
+		PublicTrade t;
+		t.trade_id = extract_string(obj, "trade_id");
+		t.market_ticker = extract_string(obj, "ticker");
+		t.yes_price = static_cast<std::int32_t>(extract_int(obj, "yes_price"));
+		t.no_price = static_cast<std::int32_t>(extract_int(obj, "no_price"));
+		t.count = static_cast<std::int32_t>(extract_int(obj, "count"));
+		t.taker_side = parse_side(extract_string(obj, "taker_side"));
+		t.created_time = extract_int(obj, "created_time");
+		t.is_block_trade = extract_bool(obj, "is_block_trade");
+		trades.push_back(t);
+	}
+	return trades;
+}
+
 OrderCancelResult parse_order_cancel_result_response(std::string_view body) {
 	const std::string obj{body};
 	OrderCancelResult result;
@@ -1276,23 +1296,8 @@ Result<PaginatedResponse<PublicTrade>> KalshiClient::get_trades(const GetTradesP
 				  response->status_code});
 	}
 
-	std::vector<PublicTrade> trades;
-	std::vector<std::string> trade_objects = extract_array_objects(response->body, "trades");
-
-	for (const std::string& obj : trade_objects) {
-		PublicTrade t;
-		t.trade_id = extract_string(obj, "trade_id");
-		t.market_ticker = extract_string(obj, "ticker");
-		t.yes_price = static_cast<std::int32_t>(extract_int(obj, "yes_price"));
-		t.no_price = static_cast<std::int32_t>(extract_int(obj, "no_price"));
-		t.count = static_cast<std::int32_t>(extract_int(obj, "count"));
-		t.taker_side = parse_side(extract_string(obj, "taker_side"));
-		t.created_time = extract_int(obj, "created_time");
-		trades.push_back(t);
-	}
-
 	PaginatedResponse<PublicTrade> result;
-	result.items = std::move(trades);
+	result.items = api_detail::parse_trades_response(response->body);
 
 	std::string cursor = extract_cursor(response->body);
 	if (!cursor.empty()) {

src/api/response_parsers.hpp

@@ -24,6 +24,11 @@ namespace kalshi::api_detail {
 /// Parses the ``orderbooks`` array returned by ``GET /markets/orderbooks``.
 [[nodiscard]] std::vector<OrderBook> parse_orderbooks_response(std::string_view body);
 
+/// Parses the ``trades`` array from ``GET /markets/trades``. Returns an empty
+/// vector when the array is missing or empty. The cursor field is read
+/// separately by the client method.
+[[nodiscard]] std::vector<PublicTrade> parse_trades_response(std::string_view body);
+
 /// Parses the ``deposits`` array from ``GET /portfolio/deposits``. Returns
 /// an empty vector when the array is missing or empty. The cursor field
 /// is read separately by the client method.

tests/test_response_parsers.cpp

@@ -243,6 +243,33 @@ TEST(ResponseParsers, MarketsParseUnopenedArray) {
 	EXPECT_EQ(markets[1].status, kalshi::MarketStatus::Open);
 }
 
+TEST(ResponseParsers, TradesParseBlockTradeFlag) {
+	// Kalshi 2026-05-29: public trade responses flag block trades via the
+	// new boolean ``is_block_trade``. First row carries it true; second row
+	// omits it (older/non-block print) and must default to false.
+	const std::string body = R"json({
+		"trades": [
+			{"trade_id": "t1", "ticker": "KXHIGHDEN-26JUN03-B80", "yes_price": 42,
+			 "no_price": 58, "count": 10, "taker_side": "yes",
+			 "created_time": 1780000000, "is_block_trade": true},
+			{"trade_id": "t2", "ticker": "KXHIGHDEN-26JUN03-B80", "yes_price": 40,
+			 "no_price": 60, "count": 5, "taker_side": "no",
+			 "created_time": 1780000100}
+		],
+		"cursor": ""
+	})json";
+
+	const std::vector<kalshi::PublicTrade> trades = kalshi::api_detail::parse_trades_response(body);
+
+	ASSERT_EQ(trades.size(), 2U);
+	EXPECT_EQ(trades[0].trade_id, "t1");
+	EXPECT_EQ(trades[0].count, 10);
+	EXPECT_EQ(trades[0].taker_side, kalshi::Side::Yes);
+	EXPECT_TRUE(trades[0].is_block_trade);
+	EXPECT_EQ(trades[1].trade_id, "t2");
+	EXPECT_FALSE(trades[1].is_block_trade);
+}
+
 TEST(ResponseParsers, DepositsParseFinalizedAndPending) {
 	const std::string body = R"json({
 		"deposits": [