Short answer: no
Long answer:
You don't need suprise spells to do sneak attack spells. A bunch of spells (basically anything that requires an attack roll) can already sneak attack. You also don't need spellstrike: you could just hold the charge and make a natural attack.
However, the spell is a rider effect on the the attack, and you never apply sneak attack twice for a single effect.
How does Surprise Spells class feature of the Arcane Trickster prestige class work with spellstrike of the magus? Does both the weapon and delivered spell both get sneak attack damage?
No. You only get sneak attack once per attack. Since the spell is coming through his weapon he does not need surpise spell to get sneak attack. Surprise spell is made to get sneak attack when you could not otherwise get it.
How does Surprise Spells class feature of the Arcane Trickster prestige class work with spellstrike of the magus? Does both the weapon and delivered spell both get sneak attack damage?No. You only get sneak attack once per attack. Since the spell is coming through his weapon he does not need surpise spell to get sneak attack. Surprise spell is made to get sneak attack when you could not otherwise get it.So basically surprise spell only benefits damage spells that are not touch attacks or ranged touch attacks already as those would get sneak attack normally.
Thanks for taking the time to clarify.
That is correct.
How does Surprise Spells class feature of the Arcane Trickster prestige class work with spellstrike of the magus? Does both the weapon and delivered spell both get sneak attack damage?No. You only get sneak attack once per attack. Since the spell is coming through his weapon he does not need surpise spell to get sneak attack. Surprise spell is made to get sneak attack when you could not otherwise get it.Ok, so if understand correctly, spell strike essentially gives me surprise spell for free, by combining the weapon with the free touch attack in this circumstance only. Because the touch attack by itself wouldn't be eligible for the sneak attack damage but the weapon is? I keep forgetting spell strike is an additional attack beyond your normal weapon attacks, basically twf.
Thanks for taking the time to help clarify.
Just to be clear, you can get sneak attack on some spells without surprise spells. Most things with an attack roll (Inflict Light Wounds or Shocking Grasp for example) get sneak attack damage if you're flanking or surprising someone. Surprise Spells allows you to apply sneak attack damage to any spell if the enemy is flat-footed (or denied DEX to AC somehow). With Surprise Spells you could cast a Fireball in the surprise round and apply sneak attack damage if the enemies hadn't acted yet.
Spellstrike doesn't really interact or change anything about sneak attack in this situation (other than maybe changing the damage type of your sneak attack).
Note that sneak attack only applies to HP damage. It can be fire, unholy, force damage, or other types. BUT, you can't turn your sneak attack dice into ability damage or negative levels. That's too bad though, 1d4+4d6 negative levels from Enervation would be awesome :P