Adding stairs to a in-ground pool spa, AFTER it's already been shotcrete

I was wondering how they can add it?
How does it fully attach to the existing spa wall? Would there be any weakness 10-15 years down the road, things I can look for when the contractor adds the stair step.

The step would be like maybe 3ft wide and 1.5ft tall

It can be done . . . badly, or well.

But if the spa structure is not tied to the rebar in the pool or spa shell, separation cracking is fairly likely. But if I were you, I'd worry about the piping and circulation design as well. It's unpopular for me to say this (even among PoolForum users), but it's not possible to sanitize an in-use spa: the ratio of 'people goo' (spit, snot, sweat, pee, poop) is TOO HIGH for the amount of chlorine (or other sanitizer) present in the small volume of pool water.

Lemme say that again, so it's clear: It is not possible to sanitizer an in-use spa.

What's more, it's not possible -- for most pool owners -- to maintain sanitary water on a spa that is separate from the pool. There ARE ways it can be done, but they are too troublesome and to labor intensive for 90+% of pool owners.

The result?

Attached spas are

EITHER part of the pool water, with an added booster, jet, or aeration pump
OR they separate systems that create plumbing, circulation and maintenance nightmares.

This is one of the 'dirty secrets' of the pool biz: they will sell you spas all day long, but they will NEVER get in one you have used, or that they have not -- JUST NOW -- re-sanitized. Spas can -- and do -- transmit disease from person to person. Spas can -- and do -- become breeding grounds for pathogenic organisms, like "Pseudomonas aerugionosa" (usually mild, but irritating) or "Legionella pneumophila" (can kill you) or harbor organisms like "Giardia lamblia" (can make you pretty sick).

If you get a decent piping system, are meticulous in your pre-use spa sanitation routine, and use the spa ONLY with family members (you've ALREADY got THEIR 'germs'), spas with separate circulation can be reasonably safe.

Otherwise, not so much.

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https://en.wikipedia.org/wiki/Pseudomonas_aeruginosa
https://en.wikipedia.org/wiki/Legionella_pneumophila
https://en.wikipedia.org/wiki/Giardia_lamblia

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Here is the picture of what I'm talking about.

https://i.imgur.com/QZ8IZYw.jpg

A single small step like that, can probably be bonded to the existing spa . . . if the prep work is done correctly.

But, that's up to your contractor to do.