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Some general advice that might apply anywhere, except that in general a suit is "fail safe" and I think for the bay area you should aim for something less formal:
Upvote:1
I mainly agree with @pnuts answer but feel that points 2 (dress casual) and 6 (jacket, white shirt, and chinos/black jeans) are in conflict. So some things to think about
Because you are not going there for training only, but to meet other software engineers and foster a stronger relationship between the two companies, I believe you should dress in business casual. Another way to look at this--if you were representing the company in a booth at a conference, what would you wear? Probably not jeans and a t-shirt that advertises your favorite band. Chinos/dockers, not jeans, a polo (at minimum) or button-down shirt, not a t-shirt.
If you feel comfortable with one or more of the other software engineers already, ask what their boss wears--not what they wear.
Upvote:3
Although I'm not living there now, I spent 25 years in the Bay Area. Although in a number of companies like Google and Facebook, I am sure there are lots of programmers wearing T-shirts and jeans, I think it would be safer to wear chinos/khakis and either a polo shirt or a buttoned shirt, but probably not white. With latter, I would think a sweater would be too formal.
No suits. Not even a sport coat.
For shoes, you can either wear traditional leather loafers (certainly not wingtips) or non-athletic sneakers (sort of a contradiction in terms, but I'm sure you know what I mean).