Open tanyao: fast hands that still have a yaku

Two things go wrong with an open tanyao hand. You chi and end up waiting on a 23s, and the 1s that finishes it takes away your only yaku. Or you call a good closed hand down to 1,000 points and fewer safe tiles. You fix both before you press the button.

Open tanyao is cheap until the dora join in

Tanyao (all simples), from Pinfu and tanyao, needs every tile in the hand to be a 2 to 8, the called sets, the pair, and the winning tile included. It's 1 han closed or open, and the open version has its own name, kuitan (喰いタン). Mahjong Soul and the EMA 2016 rules allow it. On Tenhou it's a lobby setting, on in the main ranked lobbies. Some clubs play without it (kuitan nashi), so ask at a new table. The tanyao page has the rule and the glossary card the short form.

A bare open tanyao usually counts 30 fu (Fu without counting) and pays 1,000. Each dora or red five about doubles it, until the hand reaches 4 han (7,700).

Dora and red fives	Non-dealer	Dealer
None	1,000	1,500
One	2,000	2,900
Two	3,900	5,800
Three	7,700	11,600

Closed, riichi, pinfu, and tanyao with no dora pay 3,900 by ron, the same as open tanyao with two dora.

Every winning tile has to be a 2 to 8

The winning tile (What is a yaku?) is where open tanyao hands lose wins.

You called chi on the 6m with your 78m, and the hand is tenpai.

It waits on and , 8 tiles, and only the four 4s win. A 1s finishes four sets and a pair, but the 123s holds a 1, so the hand loses tanyao, its only yaku. This is kata-agari (片上がり): a wait that wins on one side only. The back call in the yakuhai lesson can end on one too, a pair wait where only the dragon wins.

Furiten, the rule that blocks ron, makes it worse. It counts every tile that completes your shape, yaku or not (the furiten guide). A tanyao plan cuts its ones and nines early, so a 1s in your own discards is likely. Then the whole wait is furiten, and you can't ron the 4s either. If another player throws a 1s, letting it pass puts you in temporary furiten until your next turn (Tenpai, riichi and furiten). A 4s you draw yourself still wins in both cases. A 1s doesn't, even by tsumo, unless it's the last tile of the wall (haitei).

So in an open tanyao hand, a ryanmen or a ryanmen is worth what a kanchan (middle shape) is worth: one tile kind that helps, 4 tiles, with a furiten trap on top. The shapes that keep every winning tile inside are two-sided shapes from 34 to 67, kanchan from 24 to 68, and pairs from 22 to 88. A penchan (edge shape) or a pair of ones or nines can't stay at all.

Fix the wait before you call:

• Use the 23 or the 78 for the call. Say your last two partial sets are ryanmen and ryanmen. Chi a 4s with the 23s, and the 56p waits on 4p or 7p: 8 tiles, every one a winner. Chi a 4p or a 7p with the 56p, and you're tenpai on the 23s with 4 winning tiles.
• With a partial set to spare, cut the 23 or the 78 before an inside two-sided shape. A closed hand headed for riichi still wins on the 1 or 9, so the shape keeps all 8 tiles. On a tie it still goes first when the rest of the hand is all simples, because that win loses tanyao (Pinfu and tanyao).

Call when the hand is worth it

A call costs you riichi, pinfu, and menzen tsumo, as When to call chi and pon showed. For open tanyao, four situations make the speed worth that price.

• Two dora or red fives. Open tanyao already pays 3,900, so speed comes first: make the calls you'd pass on with a cheap hand, as Playing the dora advised. With one, it pays 2,000. Call when the chi or pon takes you a step closer and leaves good shapes, unless the closed hand is already good (below).
• You're the dealer. A bare open tanyao pays you 1,500, and a win keeps the deal for another hand at dealer prices (How a game works). My rule of thumb: treat a bare tanyao like a one-dora hand.
• Any win will do. A fast 1,000 that ends another player's deal, or settles your place near the end of the game, is worth more than its points. The AI engines call for these cheap hands (When to call chi and pon), and Play for placement comes back to them.
• The last turns. Tenpai when the wall runs out moves your score by 2,500 to 3,000 points at a four-player table (A draw pays the tenpai players). A late call that makes tenpai earns that, and with tanyao in place the hand can still win.

Let it pass when the closed hand is better

A good closed hand with one dora or none. Two two-sided shapes and a pair of simples are headed for riichi, pinfu, and tanyao: 3,900 by ron, 7,700 with a dora. Early in the hand, a chi cuts that to about a quarter to save one step, the trade When to call chi and pon warned against.

A ragged hand. If the call still leaves you two steps from tenpai on one-sided shapes, you've made a cheap, slow hand. Stay closed, and fold if a riichi comes.

Every call also costs defense, and in a tanyao hand the tiles left are all simples, the tiles most likely to deal in because they finish the most waits. As a sequence, a 5 completes a 34, a 46, or a 67, while a 1 completes only a 23. After two calls you hold seven of them, and that's what you'd fold with if someone declares riichi. Call for 1,000 only when the rest of the hand is good enough to finish.

Pick the call and the discard before you press

A chi on a two-sided shape opens fastest, but only by a few points. In the site's data from Tenhou's top room (Houou), 27.6% of one-call hands with no yakuhai or honitsu, mostly tanyao, that opened with a chi from a two-sided shape were tenpai at turn 8. A plain pon made 25.6%, and a chi from a kanchan or edge shape 23.5%. That data counts turns from zero, so turn 8 is the ninth discard (Is the open hand tenpai?). Once the hand is worth calling, take the call it gets.

Kuikae, the swap-calling rule from How a hand is played, still limits what you can throw after the call. And the tile you throw decides the wait you end on.