Slayer/Vivisectionist sneak attack

[Gnaeus]

So, Hybrid Classes say:
Parent Classes: Each one of the following classes lists two classes that it draws upon to form the basis of its theme. While a character can multiclass with these parent classes, this usually results in redundant abilities. Such abilities don't stack unless specified.
Vivisectionist says:

At 1st level, a vivisectionist gains the sneak attack ability as a rogue of the same level. If a character already has sneak attack from another class, the levels from the classes that grant sneak attack stack to determine the effective rogue level for the sneak attack’s extra damage dice (so an alchemist 1/rogue 1 has a +1d6 sneak attack like a 2nd-level rogue, an alchemist 2/rogue 1 has a +2d6 sneak attack like a 3rd-level rogue, and so on).

So, has it ever been decided whether Slayer 3/Alchemist (vivisectionist) 4 gets:
2d6 sneak (from alchemist, they don't stack)
3d6 sneak, (2d6 from alchemist, 1d6 from delayed progression Slayer, cant find any rules to support it, but seems like it should work this way.)
or 4d6 sneak (Alchemist text specifies how rule stacks, so slayer 3 alchemist 4=rogue 7)

Looking for RAW as much as possible here. I didn't want to post in rules Q&A because when I searched I saw a lot of old arguments from 2012, so I wasn't sure there would be a simple answer, but everything I found was really before Slayer anyway.

[Gallowglass]

At 1st level, a vivisectionist gains the sneak attack ability as a rogue of the same level. If a character already has sneak attack from another class, the levels from the classes that grant sneak attack stack to determine the effective rogue level for the sneak attack’s extra damage dice

To me the interpretation of this is, the levels from the class that grant sneak attack stack. Meaning In your example of Slayer 3/Alchemist (vivisectionist) 4 stacks the following levels

Slayer lvl 3
Vivisectionist lvl 1
Vivisectionist lvl 3

so the sneak attack is 3d6.

To me, that's the clear RAW interpretation, but I can see how you could parse the language to a different interpretation. But that's the best RAW explanation I can give you.

[Geddy2112]

To me the interpretation of this is, the levels from the class that grant sneak attack stack. Meaning In your example of Slayer 3/Alchemist (vivisectionist) 4 stacks the following levels

Slayer lvl 3
Vivisectionist lvl 1
Vivisectionist lvl 3

so the sneak attack is 3d6.

To me, that's the clear RAW interpretation, but I can see how you could parse the language to a different interpretation. But that's the best RAW explanation I can give you.
I second 3d6, that each level that grants sneak attack stacks up. Even though the slayer is on a different progression than the rogue or vivisectionist.

[Psyren]

Thirding 3d6. You could make a case for 4d6 though as it's not totally clear.

I'd say 2d6 is out - Alchemist is not a "parent class" of Slayer so there will be some form of stacking.

[Starbuck_II]

I support: #2, Vivi says it stacks delayed level not actual sneak attack.

The better sneak attack is Snackbite Brawler (actual sneak attack stacking: http://www.d20pfsrd.com/classes/hybrid-classes/brawler/archetypes/paizo---brawler-archetypes/snakebite-striker ), Cult Leader (http://www.d20pfsrd.com/classes/hybrid-classes/warpriest/archetypes/paizo---warpriest-archetypes/cult-leader ), or even Greensting Slayer Magus ( http://www.d20pfsrd.com/classes/base-classes/magus/archetypes/paizo---magus-archetypes/greensting-slayer ),

All these use text that they stack damage. Sadly Vivi doesn't stack damage, it stacks effective level.

[Gallowglass]

I bet the Hamburgler took levels in Snackbite brawler.

[Gnaeus]

The better sneak attack is Snackbite Brawler
All these use text that they stack damage.

Stacking the sneak is a byproduct. What I am really doing is adding limbs to a lantern archon. Slayer gives aspect of the beast for claws. Alchemist is providing tentacles. Whether his lasers do 4d6 or 5d6 isn't critical. But I do need to figure it out.