How do I get a happy ending in Bandersnatch?

Lifehacker.com has provided a "road map" of sort which, if I read it correctly, does have some "non-bad" options but that's a subjective issue.

Encouraged by a comment, I thought I'd try to turn my comment into an answer. The answer to the question is:

Black Mirror doesn't make happy endings.

I'd argue that is one of their calling cards, and one of the strong points of the series. The shows are heavy in terms of topics, and the overall theme of the show (technology isn't necessarily making things better) is emphasized in nearly every ending of the show.

Even the rare episode that ends on a 'less sad' ending (such as San Junipero) is seen as an anomaly as Variety critic Sonia Saraiya points out (emphasis added):

Variety critic Sonia Saraiya pointed out that technology is portrayed as good in "San Junipero", a rarity in the show.

Bottom line? Black Mirror is usually about unhappy endings. Enjoy the ride for what it is.

Although I don't believe these are all the possible endings, as I have come across other people who claim to get even more mash-ups than this and because sometimes it makes you go back and then gives you new options, the following video does discuss many scenarios, citing that there really aren't any happy endings.

However, my experience, which I wrote all my choices down and plan to go back through just to reconfirm, allowed for Stefan to time travel back as a boy and take the train with his mother, but instead of cutting to black and implying that Stefan died with mother on the train as others have expressed in their versions, mine cuts back to a therapy session, in which Stefan was found dead!

It appears my ending could be interpreted as bittersweet if we believe that Stefan died in one time line ultimately to live the way he wanted in another, but it also could be interpreted that Stefan dreamed this, while dying. This ending reminds me though of two other time travel films such as Donnie Darko or The Jacket in which main characters do sacrifice themselves for a different alternate reality.

Bandersnatch is working in the archetype of the addictive meme, similar to “The Parrot” (feel free to google the image, it is safe, hard Sapir-whorf doesn’t exist). These stories are stories where a compelling text or meta-text compels the focus character and threatens to compel the reader. They often involve recursive infection and infection “unto the seventh generation.”

As observed Black mirror don’t do happy endings. Well, they don’t do happy endings inside the text, usually. But Bandersnatch cues us early on about the infective meme. You can read this as early as the “do you understand how choose your own adventures work” screen where you are compelled to respond in a preprogrammed manner. The text offers us a solid clue (cue) here about how to read a happy ending: cease permutation and reject the text. A similar situation occurs when you pour coffee on the computer before anyone has started dying. This is another clue to reject the text.

Consider, as a relevant equivalent text, how Undertale deals with the reader recursively reading the text. Even if a spoiler switch isn’t set to 1 and the game is completed, the ending will indicate that the player will probably attempt to reread the text with the spoiler switch set to 1. Each ending is necessarily as horrific as the worst end because the reader will reread the text for the plurality of endings (or at least be made aware of this in Bandersnatch through the rerouting ending system).

Thus, the only winning move is not to play. The only happy ending is to stop the media file early, hard, and never return to it. In this case Black mirror have made a happy ending possible. It is Black mirrors’ viewers who make the unhappy endings inevitable.

The happiest ending is when Stefan reaches the maximum score for Bandersnatch. I mean, that was what he always wanted, not just the maximum score, but to put the same idea of the Bandersnatch book in his game.

Only after he killed his father he can work with calm, bring the game on time... etc. And the principal idea of the movie is revelated to us again when his therapist congratulates Stefan for finishing the game and asks him about the finale. "What the gamer doesn't know is I always control his destiny... yes, it has a happy ending" more or less said Stefan.

That's the way it is in the game, which Stefan creates; in the novel, where Pax is controling the destiny of the characters; and in the movie, which is made by Netflix. In the end, who decides how it ends is them, not us.

To make it, in the game you have to kill Stefan's father and butcher him. For a more detailed explanation please refer to the scheme above.