Reach stacking rules

[Gray Warden]

Enlarged Aberrant Bloodrager with Lashing Shadowcraft long spear, Long Arm on and Lunge: 30ft AoO / 35ft attack radius?

Throw in Combat Patrol at lvl 20: 50ft AoO radius?

None of the reach increments have a type (for example, enhancement bonus), does it mean that they stack?

[merpius]

I have never seen anything to indicate that they don't all stack, so I believe they do.

[Fuzzy-Wuzzy]

"Stack" does not technically apply to anything not categorized as a "bonus" or "penalty"---but yes, reach increases are cumulative.

However, Combat Patrol only increases your threatened area, not your reach. That's why it's got that bit about being allowed to move to make your AoOs. You'll have a threatened area of 50' but have to move to within 30' to take each opportunity.