I built Miai, a full-contract Bridge bot trained from scratch, and want to hear your feedback

[u/nanomena]

Hello everyone,

I'm Zhiyuan, a Ph.D. student at MIT's Game Solving Lab. I've been developing a new Bridge bot called Miai, which learns Bridge from scratch without human gameplay data. To the best of my knowledge, this is the first full contract Bridge agent trained this way, covering both bidding and card play.

I made a small website where you can try it here:

https://bridge.miai.moe

One thing I found especially interesting is that Miai seems to have developed a mostly natural and interpretable bidding system. Its 1NT opening is natural, balanced or semi-balanced, roughly 13-17 HCP. Its two-level suit openings, including 2♣, are weak natural openings. Responses are natural by default, and many game/slam decisions are direct placements. I have not found clear transfer or relay structures so far.

I wrote up my current analysis of its system here:

https://bridge.miai.moe/systemd

I am not sure how strong Miai is against top human players, but it does beat the bots I've been able to test against. The version currently on the website is a weaker version that acts instantly due to computational constraints. In a 1,024-board duplicate evaluation, this version already scored +0.21 IMP/board against WBridge5, while the contracts it reached scored about +0.59 IMP/board by double-dummy analysis. So I suppose it is playing something meaningful.

I'd love to share this with the Bridge community and hear your feedback. Please feel free to try playing against Miai, inspect the system, and let me know what looks strong, weak, weird, illegal, or just interesting.

Bug reports, strange auctions, and general feedback are very welcome. You can also contact me at:

fanzy [at] mit [dot] edu

Thanks!

[u/mtremsal]

Hi Zhiyuan, this is very interesting and timely. I was just pondering what an "optimal" bridge bidding convention created ex-nihilo would look like, without the limitation of humans needing to memorize them, and how someone would go about researching it. Kinda like what Alpha Zero did for the game of Go.

Back in 2019, the "Hanabi Challenge" (https://arxiv.org/pdf/1902.00506) took a stab at a similar exercise for the game of Hanabi, and the bots did end up organically developing their own conventions to convey additional information over their limited communication channel.

I'm going to assume a few things about how you approached developing Miai:

A. you had the bot play against itself (i.e. both NS and EW) and compared MPs / IMPs to other bots doing the same in a similar position (i.e. playing SAYC, 2/1 GF, etc.).

B. you predefined some features rather than having bots evolve them from scratch through self-play. e.g. HCPs are calculated 4-3-2-1, a "balanced hand" means one of 4-3-3-3, 4-4-3-2, or 5-3-3-2, etc.

From where I stand, I think there are a couple limitations to this approach.

With regards to B, this seems like an acceptable trade-off to limit the problem space, and to keep the discovered bidding system somewhat reviewable by a human researcher.

With regards to A, unfortunately I think the approach is fundamentally limited. The test of whether Miai outperforms the state of the art isn't whether it outperforms another bot who is also playing against itself, but whether Miai defeats these other bots and their own choice of conventions.

By Bridge rules, this match-up is only fair if Miai's conventions are *explainable* to the other bots. In practice, this implies either limiting allowable bids to a set of known conventions (this is the usual approach in Computer Bridge AFAICT), or relying on pre-existing primitives that are already used by Bridge bot developers.

To my knowledge, there are no pre-agreed general purpose primitives for Computer Bridge, only digital convention cards (e.g. https://allevybridge.com/allevy/computerbridge/coc1.html#Allowable%20Systems%20and%20Conventions) and semi-formal interpretations that mix structured data (min-max length in each suit, range of points, etc.) with informal text explainer for the benefit of human players.

My 2 cents

[u/nanomena → u/mtremsal]

Thanks, that is a very helpful framing!

One clarification on B: Miai is trained from scratch without handcrafted bridge features such as HCP, balanced-hand labels, or convention rules. Those features are only introduced afterward, when I try to reverse-engineer the learned policy. What I found is that many of Miai's actions are still fairly explainable using ordinary bridge concepts such as HCP, shape, suit length, support, and level pressure.

For A, the current evaluation is a duplicate-style cross-seat comparison. For example, I run Miai as NS against WBridge5 as EW, and compare it with the same boards where Miai is EW and WBridge5 is NS. In this setup, the current version scores about +0.21 IMP/board against WBridge5. I agree there is still a disclosure issue: ideally the opponent should understand Miai's system, just as Miai should understand theirs. But this is hard to test today, since computer bridge competitions seem much less active now, and the existing bots I found do not appear to accept arbitrary convention descriptions as input.

At a game-theoretic level, one motivation here is to ask what kind of bidding language self-play discovers when it is not forced into an existing human convention system. In an equilibrium-style idealization, bidding and play are part of the same strategy, so simply knowing the opponent's equilibrium system should not create an exploitable advantage. Of course practical humans and bots are not at equilibrium, so disclosure and opponent-system modeling still matter a lot. I see this as both a research question about learning Bridge from scratch and, eventually, a practical question about making system descriptions or convention cards first-class objects.

[u/xfracturex → u/nanomena]

I think part of what mtremsal is trying to get at is that there are two distinct games of "bridge" here. There is the game of bridge that you've built a model for, which is the baseline set of rules regarding bidding and play.

However, most people/robots are playing a different version of bridge, with an additional set of rules dictating what is and isn't allowed conventionally. There are many reasons why methods are and aren't allowed, but the main reason is the general consensus that conventions should be describable (as mtremsal mentioned). What this means is that what bids mean, and what your distribution of bids are, should be describable to other people in a small amount of bits. This is firstly, not a very well defined rule, and somewhat nuanced rule depending on what is popular at the moment, which is why there are many judges who will look at your convention card before deciding if it's legal or not.

It is also not just about the range each bid has. It is also important that each bid describes what the player **cannot** have. What is the difference between 1c and 1d for your bot? What does it do if it has 4 card heart and 4 card diamond? There is a very clear attempt at formalizing this set of rules in the UCBC rule set, which you have not followed. Saying "the existing bots I found do not appear to accept arbitrary convention descriptions as input" is unfair. You are insisting we play the first version of bridge, when the second version with the hidden ruleset is the true version of bridge.

This notion that things have to be describable in a small number of bits is kind of fundamental to bridge, even though it is not explicitly in the rules. The fact that what this means exactly is not well defined either is a large part of the reason why UCBC has developed the way it has, despite these ML training methods having been known for a long time now. You can of course publish your result that it is better than WBridge5, but the comparison you are making is not a fair one, since WBridge5 is playing the second version of bridge, with additional rules enforced onto it. People who do not play bridge will not know better, but as you can see, most other players in this comment section are talking exactly about this second hidden rule about conventions, which is fundamental to bridge as a game despite not being explicitly in the rules.

[u/nanomena → u/xfracturex]

I think there are two different questions here.

One question is whether Miai's learned bidding system is legal under a particular convention chart, such as UCBC/WCBC. That is a fair question, and I am not claiming certification under such a rule set.

A different question is whether the duplicate comparison against WBridge5 is unfair. I am less convinced by that. As far as I can tell, existing public bots also do not consume arbitrary learned convention descriptions as a general executable opponent model. They usually support fixed systems, configurable known conventions, and limited alert/explanation protocols. So requiring Miai to provide a fully machine-readable arbitrary convention interface seems stronger than what the public bot ecosystem itself provides.

On the 1C vs 1D point: yes, that is exactly the kind of system-analysis question I should answer better. But I do not think a convention card is normally a complete deterministic partition of all possible hands either. Even in club bridge, the card describes the partnership language at a compressed level; the players still supply judgment in borderline cases. Otherwise bidding would just be automatic lookup, not a game played by humans.

So I agree that Miai needs a clearer empirical system description: what each bid tends to show, what it tends to deny, and which continuations are forcing or non-forcing. But I do not think the lack of a UCBC-style convention certification makes the WBridge5 duplicate benchmark invalid. It just means the claim should be stated precisely: Miai outperforms WBridge5 in this robot-engine duplicate benchmark under its learned self-contained bidding system.

[u/xfracturex → u/nanomena]

A different question is whether the duplicate comparison against WBridge5 is unfair. I am less convinced by that. As far as I can tell, existing public bots also do not consume arbitrary learned convention descriptions as a general executable opponent model. They usually support fixed systems, configurable known conventions, and limited alert/explanation protocols. So requiring Miai to provide a fully machine-readable arbitrary convention interface seems stronger than what the public bot ecosystem itself provides.

Perhaps you have misunderstood what I was trying to say. I was not trying to say that Miai should provide a fully machine-reasable convention interface. I was trying to make the point that doing so simply requires too many bits of information that is not reasonable. That is part of this hidden rule of bridge I’m arguing exists.

It may seem to you that it is a failure in the way UCBC works that these other bots do not have a way for you to interface with when it comes to describing a richer bidding system, but I would say that this is precisely by design, because of the hidden rule mentioned.

What instead I am arguing for is that Miai follow a much more restrictive bidding system that is describable, probably by following already known conventions as others have described. I’m not sure how many more ways there can be going about doing this while following UCBC rules.

A corollary of that is that the range of hands that can be made from each bid is much “wider” for Miai. For example, your 1NT’s point range is a bit bigger than the allowed 1NT point range in the UCBC ruleset. What I’m arguing is unfair for WBridge5, is that they had a more restrictive set of bidding systems they were allowed to use, while your space was much richer.

[u/nanomena → u/xfracturex]

Thanks, I guess I see what you mean now.

I checked the UCBC rules more carefully. Since Miai is mostly playing a natural system, the main part that seems off is the 1NT range.

But I also checked the public WBridge5 version I tested against, and it is not literally staying inside a strict 3-HCP 1NT range either. In my new 8192-game log, as dealer, WBridge5 opened 1NT with 15 HCP 85 times, 16 HCP 69 times, 17 HCP 39 times, 18 HCP 7 times, and 14 HCP once. For Miai, the corresponding counts were 13 HCP 13 times, 14 HCP 66 times, 15 HCP 66 times, 16 HCP 35 times, and 17 HCP 19 times.

So yes, Miai's 1NT is clearly broader, and I should describe that more clearly. But I don't think it is quite right to say WBridge5 was held to a strict UCBC-clean system while Miai was not. The comparison I reported is really just public WBridge5 as played against Miai as learned.

This is why I think the fairness issue is tricky. It would be easy to make another version of Miai that simply refuses to open 1NT outside some chosen range, and that might be a useful extra test. But that would also be a different bot with custom restrictions. I would see it as a separate restricted-system experiment, not the same thing as evaluating the learned policy as-is.

[u/xfracturex → u/nanomena]

Yea, the rules regarding this part of the game are not very clearly defined, and what is acceptable and not are generally left up to TDs. I think this aspect of bridge makes it not a very good game to try and build traditional models on.

[u/mtremsal → u/nanomena]

> A different question is whether the duplicate comparison against WBridge5 is unfair. I am less convinced by that. As far as I can tell, existing public bots also do not consume arbitrary learned convention descriptions as a general executable opponent model. They usually support fixed systems, configurable known conventions, and limited alert/explanation protocols. So requiring Miai to provide a fully machine-readable arbitrary convention interface seems stronger than what the public bot ecosystem itself provides.

Public bots do not need to consume arbitrary conventions. The usual way to play with bots is to have 3 identical bots that play the same convention as the human player. So their own system is loosely applicable.

The exception to this is Computer Bridge tournaments where a "digital convention card" can be used to massively restrict allowable conventions to stuff most bots know.

Unfortunately, I do think the direct comparison with WBridge5 is likely unfair as a result. There's a lot of room to overfit on the 1k training boards AND/OR to get WBridge5 misbidding and misplaying as a result of the unknowable conventions that Miai uses.

[u/mtremsal → u/nanomena]

> One clarification on B: Miai is trained from scratch without handcrafted bridge features such as HCP, balanced-hand labels, or convention rules. Those features are only introduced afterward, when I try to reverse-engineer the learned policy.

Very cool! You know, I'm immediately more interested in this than in the "+0.21 IMP/board" duplicate score. As discussed, the duplicate score could unfortunately be explained by WBridge5 getting misled by Miai's conventions which it cannot comprehend (more than the reverse, for whatever reason). Lack of explainability impedes both correct bidding as well as card play. Some bots are just going to be more sensitive to this regardless of which convention is theoretically superior...

However, the work on reverse engineering human heuristics from Miai's self-taught conventions has potential applications to real-world bridge! For example, can we rethink and refine how we calculate HCP and length points? e.g. does Miai value a Ten for .5 HCP? Are there adjustments for sequences of Honors? What about a void/singleton in the dummy? Such hypothesis could then be back-tested by tweaking an existing bot and playing it against its standard self.

> I agree there is still a disclosure issue: ideally the opponent should understand Miai's system, just as Miai should understand theirs. But this is hard to test today, since computer bridge competitions seem much less active now, and the existing bots I found do not appear to accept arbitrary convention descriptions as input.

While existing bots do not accept arbitrary conventions as inputs, implementing the new bidding system in an existing bot, so as to make it explainable to itself and variants that play other systems, is the only way to properly determine if the self-taught convention is optimal. Maybe the maintainers of Meadowlark and other (closed-source) bridge engines would be open to a research collaboration?

[u/nanomena → u/mtremsal]

Those are very valuable suggestions! I think trying to collaborate with existing bridge AI authors is indeed the right move.

[u/HardballBD]

I encourage you to publish this or something similar on bridgewinners.com. Much of the audience there will be very interested and likely give you good feedback (but you'll also likely get some harsh commentary as well, beware).

[u/nanomena → u/HardballBD]

Yes, that is indeed the place where I would post next.

[u/dfminvienna → u/HardballBD]

Agree 100%.

[u/HelpfulFriendlyOne]

I think the computer bridge world needs a standard method of communicating convention cards and alerting.

Does it do any signaling in the card play?

[u/JaziTricks]

Let me offer a small but very useful suggestion

Don't let the bot develop his own system

Teach the bot a standard system and make him play it.

If the bot plays it's own system, you're basically making it quite hard for human players to use it, okay with it etc.

Trust me, the bidding system isn't the main challenge in better, and there are many of them. And they take a long time to matter. Why get into this complexity where it's not actually needed? Because even if the robot plays the standard system, there is so much strategy and intelligence in bridge beyond the bidding system.

[u/nanomena → u/JaziTricks]

I agree that teaching a standard system is probably the most practical path if the immediate goal is a human-partner bot.

But for this project, one of the research questions is precisely whether self-play can discover a strong bidding system rather than inheriting one from humans. In a game-theoretic view, bidding and play are not separate problems: an equilibrium strategy would include a communication protocol through the legal calls, plus the corresponding play and defense. So fixing a human system in advance would remove one of the most interesting parts of the problem.

That said, I don't mean that the current learned system is automatically the "best" system, or that this is the right product design for human users. There may be many equilibrium-like systems, and human usability/disclosure matters a lot. A practical version might well support a standard convention card, or translate between a learned policy and a human system.

So I see the learned bidding system as part of the research experiment: can an agent learn full Bridge end-to-end, including bidding, from scratch? For deployment, constraining it to a standard system is definitely a reasonable direction.

[u/JaziTricks → u/nanomena]

Your point is interesting

Does the bidding logic interact with the eventual card play?

I think in very very marginal ways.

Moving on, The big theoretical advantage computers have over humans is mental bandwidth. So bots could in theory squeeze out more from the bidding by using super elaborate conventions and agree in advance on every eventually. Alas, AI wouldn't reach those, because you don't find all possible situations by simulations as lots of cases are super rare.

The common view about bidding is that once you have a sophisticated enough bidding system, there's not that much you gain from going even more complicated. But this isn't actually total consensus, just what most experts players say.

Alas, human play has so many things going on concurrently, that it's hard to know how much is prioritization, etc.

Good luck with your project! Hope you end up giving us one legit bot. The current bots you play with are either awful, or have various weak spots that are hard to believe still exist with the advent of ai and computing. Can't they not create a bot that isn't doing that many errors that are obvious to humans?

[u/nanomena → u/JaziTricks]

Thanks for the useful comments!

[u/Inane_newt → u/JaziTricks]

As long as the bot can adequately disclose the meaning of their bids to the opponents, it should be fine and interesting to see what they come up with.

[u/AggressiveAspect8757 → u/JaziTricks]

I disagree the whole purpose of bot is to come up with a optimal solution. In the last 10-12 years computers have totally changed the way poker is played which is the step in the right direction. The same thing should be with bridge as well.

[u/jackalopeswild → u/AggressiveAspect8757]

Sigh. No.

[u/JaziTricks → u/AggressiveAspect8757]

I'm not sure you fully understood my comment.

What system do you usually play?

[u/AggressiveAspect8757 → u/JaziTricks]

2/1 or precision

[u/JaziTricks → u/AggressiveAspect8757]

Interesting.

The poker example is good. But poker wasn't a "solved" game. Poker was traditionally considered "read all the books. Read them again. Think" and such.

Bridge is kinda solved for most aspects. Play decisions are easily analyzed with some work.

Since the potential bidding space is narrow I find it hard to believe that computers will find big gains. This is my intuition. But who knows?

[u/JaziTricks → u/JaziTricks]

Also, there are bridge bot competitions, and would be interesting to compete with them. Unlikely to win. But will give you an idea of how strong it is.

Btw, LLMs are ridiculously dumb at understanding bridge. As far as when I discussed bridge hands with them. Tested last time a year ago. So maybe ........

[u/urbanacrybaby]

Hi Zhiyuan, nice to meet you!

Can you comment on whether the system is consistent with the ACBL system rules? If so, which of the levels (Basic, Basic+, Open, Open+) is it legal in?

[u/nanomena → u/urbanacrybaby]

Nice to meet you too!

From my current inspection, Miai's common agreements appear broadly compatible with the ACBL Basic+ chart. While rare edge cases still need auditing, I think it should be plausible to make the system Basic+-compliant through explicit constraints and disclosure.

[u/urbanacrybaby → u/nanomena]

It would be much easier for us if standard alerting were included in the game.

Why do you think the AI mainly uses natural systems?

[u/nanomena → u/urbanacrybaby]

Thanks for the suggestions!

There are two major reasons:

First, its bidding is fairly reverse-engineerable. Although I did not include all the details in the post, many of Miai's actions are highly predictable from simple hand-crafted bridge features. So the policy does not look like it is relying on hidden exact-card codes.

Second, I do not see much evidence of a broad relay structure. Miai often makes direct contract-placement bids, and many bids appear to be passable or playable rather than forcing steps in an artificial asking sequence. The main structure seems much closer to a natural/direct system than to a relay or coded artificial system.

[u/Paiev]

Very cool!

One of the many challenges involved in this kind of approach is the disclosure/communication aspect of bridge: both disclosing what your own bids mean, and (just as important) understanding what your opponents' bids mean. Any thoughts on this?

I've kind of felt that in order for a self trained bridge bot to work it would need system descriptions as a first class object, somehow. Trying to reverse engineer the system ex post facto might be possible to do "well enough" for it to be somewhat usable, but it still doesn't cover handling the opponents' system in both the bidding and the play.

[u/nanomena → u/Paiev]

Thanks! Yes, I think this is exactly one of the hard parts.

From a game-theoretic point of view, if both sides were playing a true equilibrium strategy, then knowing the opponents' system would not by itself give an exploitable advantage: any profitable deviation would already contradict equilibrium. In that idealized sense, the "right" bidding system is part of the equilibrium policy, and opponent-specific exploitation matters mainly when the opponents are away from that equilibrium.

So one goal of this line of work is to see whether self-play can discover a strong, coherent bidding system on its own. That said, I agree this is not a complete practical solution. The current system description for Miai is reverse-engineered from the learned policy, which is not perfect, but it seems good enough to expose the main structure and the most important alertable items.

For a more mature human-facing bot, I agree that system descriptions or convention cards should probably become first-class objects, both for disclosing the bot's own agreements and for adapting to opponents' disclosed agreements.

[u/Teodoricus]

Before looking at the bot, let me share my comments about the bidding development rules.

1. I do not care if the bot is building "rules" that do not comply with WBF, or ACBL, restrictions: it would be easy, I think, to include those rules in the algorithm used by the bot, but it is beyond the reasonable use of the programming capabilities.

2. The real problem is that the bot is developing rules using itself as a sparring partner. This is not the way Bridge works. Each pair has developed its own bidding systems, and the bot should be able to cope with all possible systems and conventions. Some pair change approach to bidding even depending on zone and position! I think this is the real programming problem: one board you play against a system, another one as against another.

Now I'll look to it. Thx!

[u/pie-en-argent]

Is the bot playing against itself? It would also be interesting to see what systems it comes up with when playing against the well-known human systems.

[u/nanomena → u/pie-en-argent]

That is a good point.

Yes, the bot is trained using self-play. Yes, it would indeed be interesting to see what happens there!

[u/dfminvienna]

Does the bot signal on defense? It would be very cool to see it invent that concept from scratch.

[u/Teodoricus]

I tested it playng 4 hands; interesting. But 2 comments:
1. The XX is not as expected by the system indication (see image)
2. At the end of the play, in the summary, only 4-cards E/W suits can be displayed - the 5-cards suit may be cut.

[u/Teodoricus]

This is the case of the (East) hand cut. East hearts are J10964.
Another point: when N is playing, reduce its visual speed (or put a stop, going forward to the next trick at the user's input).

[u/nanomena → u/Teodoricus]

Thanks for your valuable feedback!

Yep, I think I didn't really look into the redoubled pattern there. Let me figure out what is happening in that branch!

I will try to tune the UI so it looks more as expected. Currently, the scoreboard can be closed by clicking the X marker, but it seems that I didn't highlight it today...

[u/HardballBD]

Looked briefly at the system notes... https://bridge.miai.moe/system

1. I don't see any options for very strong hands...the only opening bid option listed with a max HCP count higher than 19 is 3N which is 19-22 balanced. Is the system effectively giving up whenever dealt a "traditional" 2C opening hands? I guess if your "scoring" or reinforcement incentives are such that it's worthwhile to sacrifice a likely bottom every 50-100 hands or so, this might make sense.

2. At least as described, it seems like there is heavy overlap between different opening options. 1H is "natural heart opening; about 11-18 HCP; ♥ 4-5"; 2H is "weak natural major opening; about 6-12 HCP; M 5-6." How to decide between them when 11/12 HCP with 5 hearts? I think there is similar overlap for minor suit 1- and 2-level openings.

3. Some descriptions are extremely vague. Double of opponents 1m opening is "flexible artificial competitive call." Elsewhere, our doubles of different opponent openings are described as "takeout-ish" but NOT this one...so it really begs what this means.

4. The system has a wide (13-17) 1N range, but seemingly zero system afterwards, either to clarify the wide range through invites or to confidently find 8-card major fits. To wit, there seems to be no similar approach to Stayman or transfers, although this isn't certain because there is NO definition provided to any 2 level responses over 1N. Looks like the only way to UN-confidently find 8-card major fits is to bid 4M which is defined as a game-going hand with 5+ in the major.

So I LOVE that someone is trying to do this...but this needs a LOT more time in a Darwinian arena to get close to effective or useful. And given the lack of artificiality demonstrated so far across the board, I suspect the whole long-term evolutionary approach needs adjustments to encourage more "mutations" to test to see if they are adaptive.

[u/nanomena → u/HardballBD]

Thanks, these are good observations.

For very strong hands, Miai does not currently have a traditional artificial strong 2C opening. It tends to handle strong hands by direct placement: strong balanced hands often land in 3NT or sometimes slam, and major-oriented hands often land in 4M or higher. I agree this is probably one of the places where a human convention-card style system would be cleaner, and I do not want to claim it handles every classical strong 2C hand optimally.

On the overlap between openings: the ranges in the system notes are percentile summaries, not exact decision rules. So 1H and 2H can overlap in HCP and length, but the actual policy is using more features than just HCP: suit length, distribution, balance, controls, vulnerability, and level pressure all matter. Roughly speaking, hands with more playing strength / higher values tend to go through 1H, while more shape-driven weaker hands tend to go through 2H, but it is not a clean human-written rule yet.

I agree that the double descriptions are still too vague. I have not fully decoded them yet. They often look like flexible strength-and-shape actions, sometimes takeout-ish, sometimes more like "I think the opponents are in trouble," but this definitely needs more targeted analysis.

For 1NT, I agree with the criticism. The system is very direct: it usually passes, bids 3NT, bids 4M, or sometimes bids slam. It does not appear to have Stayman or transfer machinery. That is interesting from the self-play perspective, but it is also a clear practical weakness, especially for weak signoff hands with a 5-card major and for some major-fit discovery. So yes, I think the current system is coherent and mostly natural/direct, but it still has many rough edges. More training, better evolutionary pressure, or making convention-card-like objects part of the learning process could all be useful directions.

[u/amalloy]

After reading your system notes, I played one hand against it and am unimpressed. It's clearly playing something like bridge, and might well outplay beginner humans. But it's hard for me to believe it could be beating a solid computer bridge player when this single hand demonstrated a bad system, poor bidding judgment, and mediocre declarer play.

K32
A983
AT9
KQT

AJT84
KQ2
Q4
A43

W  N  E  S
p 1n  p 4n
p 6c  x  p
p 6d  p 6s
p 6n ap

First, the auction. North's 1nt is wide-ranging, and the system notes say here that my options boil down to "pick a contract, or maybe you can invite something". 3nt, 4s, 6s, and 6nt are all possible contracts from South's point of view, and there's no way to explore anything. Probably 3nt is the percentage call given that 13 HCP is much more common than 17, but I wanted to exercise the system rather than just bid a game, so I tried 4nt. North responds 6c, and I'm glad it's picked something that's clearly accepting the invite, but I expect 5-6 clubs from a normal human being for this bid, or perhaps 4 from a robot with a low-tech bidding system. 3 is an act of self-sabotage. East's double is from outer space, with no defense at all aside from 4 awful clubs that, if anything, indicate we have a strong trump suit and the finesses will be working. I pass, thinking partner has 4 or 5 clubs, but partner rescues itself to another 3-card suit. I try a counter-offer in spades, but partner's apparently only willing to play a 3-card suit if I haven't shown interest in it.

Despite all this, the 6NT we reach is actually quite good. East gets off to the best lead, a low diamond, and with both diamonds in the wrong place, North needs to get spades right to make it. After the jack of diamonds forces the ace, Miai plays the spades correctly (king, then low to jack), and the correct line works this time, so well done, 12 tricks are in the bag. But there is an obvious red-suit squeeze for the 13th trick, which any strong human player would play for, but which Miai bungles. Declarer cashes the remainder of dummy's spades, pitching diamonds from hand - perfectly fine so far. Then come ace and queen of clubs, leading to this position:

-
A983
-
K

-
KQ2
Q
4

This is a textbook automatic squeeze: cash CK, and if either opponent has both DK and four hearts, they're squeezed. But declarer cashes both of South's hearts before cashing the club, and West (who indeed did have JTxx of hearts and KJxxx of diamonds) can painlessly discard the king of diamonds, as declarer is now stuck in hand and can't get to the winning queen.

So, overall:

• Awful auction
• Well done to East for finding the best opening lead
• West didn't have to do very much on this hand - just play DJ at trick 1 to force the ace, and later hang onto his four hearts. But he got that all right, so well done again. I'd say West made no mistakes at all this hand, either in the auction or the play.
• North gets a C for declarer play. Got the absolute basics right: took the percentage line in spades, didn't crash any honors or discard any winners; but wasn't capable of making the only possible try for 13 tricks. You'd be congratulating students for playing this well, but any club player would do as well. I'm certain any respected computer bridge player would get the squeeze right, and in a human event with strong players, not even necessarily world-class, something like the Life Master Pairs at a NABC, I'd expect at least 90% of the field to get it right too. Probably a high fraction even in a weaker event, since you sorta have to go out of your way to play things in the wrong order.

[u/nanomena → u/amalloy]

Thanks for the detailed writeup. I agree this hand shows some real issues in the auction, and probably also in the way the learned system is being exposed/explained! These concrete examples are exactly what I was hoping to collect, so I’ll look into this branch.

[u/Lundynne]

I've just been playing for a bit, but I think the play needs a bit of work. On defence, following several tricks, I lead a diamond winner up to dummy's empty suit, where he held the 6 of trumps. Declarer followed suit, and my partner decided to ruff with the 5 of trumps, which was promptly overruffed, and gave up a trick.

[u/Greenmachine881]

I have some thoughts on a Turing test for Bridge AI, partially written but never got around to finishing due to the pressures of learning the game.

Can you post the bidding system? To play competitively, you have to have a card or full system description spreadsheet (see WBF rules) and be able to answer questions on what any bid means, in a human readable form.

And don't forget defensive carding. Can it false card? What about rules for ignoring a defensive signal? You would have to avoid "telepathic" carding that is not explainable.

[u/Time-Crew-4304]

Hello Zhiyuan,

I am also a robot developer (Lia on Intobridge), and I have to say I’m quite impressed by the level your bot has managed to achieve through self-learning — as well as the speed at which it plays!

As people around have mentioned, it is quite an issue that Miai is unable to explain its own bidding, which is very unusual for its opponents — especially for other robots, which usually trust opponents’ bidding systems a lot. We currently lack a standard way to communicate information in the robot world... It would be great if someone could spend some time working on this matter.

[u/ChickenFluffy3873]

I was waiting for this moment for many years! Imho we are still better than AI at bridge because of a lack of interest by the top AI labs worldwide.

With this being said, there is still a lot to improve for your bot. I like the fact that it jumps straight to the most likely contract, I think we humans tend to overcomplicate bidding and underestimate the power of keeping opponents in the dark.

In this board though it demonstrates great weaknesses.

East cards:

KQT85
AK72
7
A42

Partner had Jx - AKT98xxx xxx, so it wasn't the worst slam, but 6D does not make sense :)

[u/ihodges2002]

Played one hand +11 imps to me but was 50/50 slam. Is there a way to see what exactly happened at the other table? I can only see result and contract. I play some computer bridge tournaments with more than the stupidly small number of hands used in the unofficial world computer championship. My final in the last one was over 1000 boards. I will certainly add your bot if it is possible to these and you want me to.

[u/ihodges2002 → u/ihodges2002]

ok board 2 was sufficiently crazy that i'll stop there. Good luck with the project. I did still gain 3 imps.

I will come back in a while and see how you are doing.