Wire a card into a strategy slot so the engine evaluates it during backtests. Call after building a card with builder_add_condition or builder_compose. Every strategy needs at least one entry attachment to trade.

Roles

• entry — open a position when the card fires (requires direction="long" or "short")
• exit — close the position when the card fires (size_frac controls partial exits). Set direction="long" or "short" to scope it; omit direction to apply it to BOTH sides.
• gate — block all entries when the card is false (evaluated first)

builder_attach(strategy_id, card_id, role="entry", direction="long")
builder_attach(strategy_id, stop_id, role="exit", direction="long") # long only
builder_attach(strategy_id, time_exit_id, role="exit")                  # BOTH

Directional entry groups

• Entry cards with the same direction are ANDed: all must fire on the same bar.
• Long and short groups are alternatives. If both fire on one bar, the signal conflicts and no order is placed.
• Bidirectional strategies enter only while flat.
• No same-bar reversal: an opposite signal while invested is diagnostic only. Even if an exit fills on that bar, it does not enter the other side; the complete opposite entry group must fire again on a later bar while flat.
• Sizing and exits whose direction is omitted are shared by both directions.

To express OR / NOT / sequence within one direction or for gates, combine conditions into one card with builder_compose. Gate cards are ANDed; exit cards remain independent and any firing closes.

Exit precedence — when multiple exits could fire on the same bar, the engine evaluates them in descending priority and exits on the first match. Default order: fixed_targets > trailing_stop > custom-condition exits; attachment order breaks ties within a tier.

Returns attachment_id and card_id. Use card_id (not attachment_id) for builder_detach.