Batch orders

Send one order to several accounts at once (at most 20 legs).

Every leg inherits defaults and may override any of it, including with a falsy value (slippage: 0 means zero). Fields are snake_case: symbol, operation (buy, sell, buyLimit, sellLimit, buyStop, sellStop, buyStopLimit, sellStopLimit), volume, price, slippage, stop_loss, take_profit, stop_limit_price, expiration, comment, expert_id and, on the leg, account_id. results mirrors orders one for one.

Leg status: filled (the broker accepted), rejected (the broker refused; retcode says why), invalid (the terminal refused the request), unavailable (terminal up but not trading), unreachable (no terminal), timeout (unknown: it may have executed, including when the broker's reply was lost; reconcile or replay with the same Idempotency-Key, never blind-retry).

Validation is all-or-nothing, execution is not. Errors: 400 invalid_batch / unknown_account / unreachable_account (with require_reachable), 401, 403 (read-only key), 409 idempotency_in_flight, 422 idempotency_key_reused, 429 rate_limited (60 batches a minute per organisation, with Retry-After), 503 idempotency_unavailable. Idempotency-Key (at most 128 characters) replays the stored response for 15 minutes with idempotent_replay: true; each leg also carries its own derived key, so a retry never double-fills a leg that already executed. Every leg is in its account's audit trail.