Horne's availability comes as a significant lift after fears he could miss the last-four clash following a bruised hand suffered in last weekend's quarter-final win over Connacht. The influential scrum-half was forced off during that match and missed training on Monday before returning on Tuesday.
Dobie's comeback gives Glasgow strong cover at scrum-half, but Smith has admitted Adam Hastings' inclusion among the replacements is partly down to concerns over Horne's fitness.
Hastings gets the nod on the bench ahead of Ollie Smith, with his goal-kicking ability viewed as an important asset given Horne's status as Glasgow's primary kicker.
"Every match has specific ingredients that you have to look at," said Smith on Hastings' inclusion. "Ollie has been brilliant for us and I think last week we were always going to go after every try-scoring opportunity that was going to present. With George's hand, to have another specialised kicker on the bench is maybe an important ingredient.
"Again, like I said, I'm treating every match on merit and what the position brings and what we're going to face. Obviously, Adam is a world-class player and I think he will contribute when he gets a chance."
Smith revealed Horne's hand had been a genuine worry at the start of the week.
"George's hand was a real concern at the start of the week and I'm just thankful that he's progressed so well. He's an important ingredient but I don't want to add any pressure on him.
"He's an important ingredient but Jamie has got his skill set and Ben Afshar has brought it and even Jack [Oliver] when it was his turn.
"I think George is unique and he's a brilliant competitor and he gets the best out of everybody around him. Therefore, his contribution is massive and he's so influential from that aspect. I hope that the fact that he's available is a very important ingredient for us."
The only change to Glasgow's starting XV from the victory over Connacht is Gregor Hiddleston replacing Johnny Matthews at hooker, with Seb Stephen coming onto the bench.
"Johnny's been carrying a little quad strain," he said. "It is obviously a concern, but I mean, Seb has been playing really, really well the whole season. He's done an important European Cup game, he's played some good rugby. Johnny was in form in the last two weeks, therefore Seb wasn't picked.
"But I think Seb is more than ready to take the battle on, especially I think Seb's set-piece is good and we expect obviously the Bulls to come in that part of the game hard."
More than 17,000 tickets have been sold for the semi-final at Murrayfield, with Glasgow moving from Scotstoun for the showpiece occasion.
Despite Scotstoun's formidable record under Smith, the Warriors head coach does not believe the change of venue will make a significant difference.
He said: "No, I think for finals week, it won't make much difference. I think the fact that we've I think the fact that we're going to a place like Murrayfield in Scotland is important.
"It's an important ingredient to go and play at the home of rugby in Scotland and that is more of an injection of energy. It was never a consideration, it wasn't even mentioned, the fact that we are not going to play at Scotstoun. It was always from the start about being excited to go and play at the home of Scottish rugby."
A fierce rivalry has developed between Glasgow and the Bulls since Smith's side won the URC title in Pretoria in 2024. With the South Africans arriving in excellent form, the Warriors coach is under no illusions about the challenge awaiting his team.
"Yeah, they're a top team," he admitted. "Again, we've played them in the round of 16 [in Europe], which was a couple of months ago. It's not like it's too long ago and we've seen what they've brought.
"Since then they've played the Scarlets this side and then they've had a nice time at home where they've played at high altitude regularly and obviously they then managed to put a good streak of games together. They've grown confidence. Like I said from the start, they are a good outfit.
"Already before Johan Akerman started coaching them, they were playing in three finals consecutively. They've got good players there. They've got a huge squad depth. They've got the best junior rugby players in the country in their environment. They've been winning a lot of games in the URC since the URC started in the past five years. They always were competitive, I think.
"Now with Johan there and he had some coaching experience. So, yeah, it's on the course. They are one of the best teams, if not the best stocked team in the competition."