Competitive bidding

The 2NT is supposed to be too strong to overcall, so this is the only entry for competitive auctions beginning with strong notrump openings.

Opponents have many defenses against 1NT. Although Wbridge5’s strategies vary according to the overcall, there are 2 principles across all overcalls.

• System off: There is no more Stayman nor transfers.
• Catchall structure: Artificiality may introduce conventions but seldom changes bidding structure.

Responses over (Dbl)

Wbridge5 has no conventional runout because 1NTx is often good enough. Opponents are worried about the double, too. Opener only runs to a suit with 5+ cards.

Responses over (2 of a suit)

The cooperative double is not changed for artificial overcalls. This may be counterintuitive, but Lebensohl already takes care of the overcalled suit, so the double still serves to find a 4-4 fit.

Lebensohl is the only alertable convention here. Conventions at 4-level (4♦!, 4♠!) are cancelled because these 2-suiters can be expressed at 3-level first.

Cuebids

An adverse suit is a suit known to be held by opponents, aka an anchor suit. An overcall introduces 0–2 adverse suits. For example, Cappelletti 2♣ introduces no adverse suit, natural 2♣ one (♣), Landy 2♣ two (♠, ♥). A takeout is deemed suitless as a takeout double.

Cuebidding is to bid an adverse suit. Cuebids show game-forcing values but unsuitable to bid 3NT. Detailed meanings are introduced in the following subsections.

With 1 adverse suit

If the overcall is nonforcing, a pass may end the auction. Therefore, hands with more game aspect deserve a direct cuebid. The delayed cuebid denies stopper in the adverse suit, making it tolerable to pass out.

If the overcall is transfer, there may be 2 available cuebids below 3NT. The direct cuebid is mapped at 3-level, the delayed at 2-level, to achieve the same safety without passing out.

• Direct 3-level cuebid: Takeout with game-forcing values, 4+ cards in every nonadverse suit.
• Delayed or 2-level cuebid: Game-forcing values, adverse suit unstopped. The cuebid after the Lebensohl 2NT - 3♣ is not this one: it is invitational with a 6-card minor (Lebensohl).

Probing Wbridge5 5.12 shows the delayed cuebid over (2♥) and (2♠). Responder passed (2♥) on 9 of 300 boards with 10–16 HCP, three cards without a stopper in the adverse suit and no 5-card suit. For example, ♠AKQ10 ♥972 ♦Q2 ♣K1087 passes (2♥). Over (2♥) P (P), opener reopens on 46 of 236 boards. It doubles only with a doubleton heart (13 boards). After the double, responder cuebids or converts the double to penalty.

The cuebid came on 18 of 28 boards over (2♥) and on 14 of 29 over (2♠). Over (2♠), a 4–5 card club suit at 9–10 HCP bid 3♣ instead.

By default, Wbridge5 reads (2♥) as Multi-Landy, i.e. hearts and a minor. After an advancer’s 2NT asks and the overcaller shows the minor, responder doubles with 4 cards in that minor. It cuebids 3♥ with a doubleton: 12 of 28 boards over (3♣) and 5 of 28 over (3♦). When E-W play SEF, where (2♥) is natural, responder made the same direct call on 294 of 300 boards. The other 6 chose a different game or slam level. After the reopening double, it cuebid 3♥ on 20 of 28 boards.

With 2 adverse suits

Because there are 4 possible stopper combinations, 3 cuebid patterns are needed to seek 3NT. The 2 direct cuebids shows the only stopped adverse suit. The delayed cuebid denies any stopped adverse suit, where passing out is tolerable.

• Cuebid: Game-forcing values, stopper, the other adverse suit unstopped.
• Pass then cuebid: Game-forcing values, both adverse suits unstopped.

Probing Wbridge5 5.12 shows no notrump slam tries over Landy 2♣. Responder bids 3NT even with 18–21 HCP.

Probing Wbridge5 5.12 shows the pass then cuebid over Landy 2♣ at 9–13 HCP, with 2–3 cards in each major and a 4-4 minor holding. Most hands with 10+ HCP cuebid at once, but a few pass with weak majors, even at 16 HCP. The second call depends on which major the advancer chose (M below), with OM being the other major.

• ♠Q3 ♥1075 ♦Q653 ♣AKQ2: Pass over 2♣, then 2♠ over (2♥) and 3♥ over (2♠).
• ♠854 ♥97 ♦AK94 ♣KJ42: Pass over 2♣, then 2♠ over (2♥) but X over (2♠).

Natural (2♣♦)

Wbridge5 reads the opponents’ (2♣) as Landy and (2♦) as Multi unless told otherwise. Opponents playing SAYC overcall a natural 2♣ and 2♦. Opponents playing SEF keep Landy 2♣ but overcall a natural 2♦. Probing Wbridge5 5.12 shows that a natural overcall follows the table above, with the overcalled minor as the only adverse suit. Against SEF’s Landy, the same 300 hands drew the same 300 calls as against the default.

With 5 hearts, responder signs off in 2♥ up to 9 points, goes through Lebensohl 2NT with 9–11 points and jumps to 3♥ with more. With 6 hearts, it bids 2♥ or 4♥.

The same 300 hands were dealt against both meanings of 2♣. Only 116 drew the same call. The main differences:

• Majors: 2♥ and 2♠ are signoffs, not cuebids. Of 300 weak hands with 5+ hearts, 150 passed Landy and bid 2♥ over a natural 2♣. Hands with game values and a 5-card major jump to 3♥♠ instead of bidding 3NT.
• Slam tries: 4NT and 6NT come back. With 16–20 HCP, 10 of the 300 hands bid 6NT over a natural 2♣. Over Landy, those same hands bid 3NT.
• Stoppers: The double and 3NT trade places by the club stopper.

For example:

• ♠AK ♥AK3 ♦K76 ♣Q10432: 6NT, but 3NT over Landy.
• ♠AKQ1093 ♥J10 ♦Q53 ♣104: 3♠, but a 2♠ cuebid over Landy.
• ♠86 ♥A10653 ♦K965 ♣103: 2♥, but Pass over Landy.
• ♠KQ4 ♥842 ♦1093 ♣AJ72: 3NT, but X over Landy.
• ♠10876 ♥AJ3 ♦Q1094 ♣Q5: X, but 3NT over Landy.
• ♠KQJ9 ♥KQ32 ♦A982 ♣4: 3♣.

Over a natural (2♦), the double is again cooperative (8–16 HCP, 3–4 in each major) and 3NT promises a diamond stopper (99 of 104 hands). 3♦ is the cuebid, with 4-4 in the majors and a diamond singleton (3 boards). Diamond suits bid 3NT instead. SAYC and SEF drew the same 300 calls. Against the default Multi, 81 of the same 300 hands called differently. The most common change, 29 hands, was a double instead of 3NT. For example, ♠KQ4 ♥842 ♦1093 ♣AJ72 doubles a natural 2♦ but bids 3NT over Multi. Over Multi, the double holds only 8–9 HCP (16 boards), and 3NT holds 8–17 HCP without promising a diamond stopper (54 of 86 hands held one).

A natural (2♥) draws almost the same calls as the default 2♥, which shows 5 hearts and a minor. 290 of 300 hands with 8–15 HCP called the same. The rest were mostly 8–9 HCP hands that bid 3NT instead of 2NT. A natural (2♠) behaves the same: 290 of 300 hands called as over the default 2♠. Six of the rest were 8–9 HCP hands trading 2NT and 3NT both ways, and two 14–15 HCP hands bid 4NT instead of 3NT, e.g. ♠AQ102 ♥852 ♦KJ83 ♣A6.

Responses over (2NT)

The 2NT overcall is a cuebid and notrump contracts are hard to play, so this call is innately forcing. The force gives responder a second chance to bid, which makes up the loss of the Lebensohl 2NT.

The 2NT overcall usually shows both minors, which is not only practical but also logical. A convention skipping majors is usually minor-oriented, and 1-suited hands can be shown at 3-level.

The double seems useless. It dissuades opener from bidding, letting responder penalize opponents in the next round.

In the next round

Unless vulnerability is unfavorable, penalty is often better than 3NT if responder has strength but no biddable suit. If 3NT makes, their 3-level contract often goes −3 or more.

Responses over (3 of a suit)

The bidding structure is the same as competition on 2-level, but tactics are slightly changed. After a cooperative double, opener is reluctant to bid over 3NT. Therefore, doubling 3♠ is more penal and off shape. Responder usually doubles 3♠ instead of signing off at 3NT. Probing Wbridge5 5.12 shows that a double of 3♥ is still cooperative and denies a ♥ stopper, so 3NT remains the usual call with a stopper.

Not probed

• Pass, then cuebid over Multi (2♦): responder’s passes there hold only 1–8 HCP.
• Transfer overcalls: Wbridge5 has no option to make the opponents play them.