3 Insane Harlowe Builds in Borderlands 4: Infinite Rockets, Cryo Slam, and Radiation Nukes

Harlowe in Borderlands 4 is the tech-focused Vault Hunter whose gadgets change how you fight. Below you’ll find clear, concrete builds that use each of her three skill trees and their Action skills, plus direct links to the creators who demonstrated them.

1. Harlowe’s skill tree and playstyle, explained
2. Infinite rocket build
3. Cryo slam build
4. Radiation Chroma Accelerator build

Harlowe’s skill tree and playstyle, explained

Harlowe’s kit centers on gadgets and Action skills. Her three trees each grant a unique device: the red tree gives the Chroma Accelerator, which launches an energy bomb; the green tree provides the Flux Generator, which projects an energy field that damages enemies and can protect allies; and the blue tree uses the Halo Accelerator, which places enemies in stasis so you can move or set up combos. Each tree plays differently, so pick one based on whether you prefer nukes, sustained area effects, or stasis-based crowd control.

Community creators have tested specific builds for each tree. For example, Termx demonstrates two green/blue-tree approaches, and NickTew has a red-tree guide focused on Chroma Accelerator damage.

https://www.youtube.com/@ItzTermx

https://www.youtube.com/@NickTew

Infinite rocket build

The infinite rocket build uses Harlowe’s green tree and the area created by the Flux Generator to convert shots into Action-skill damage. Specifically, you run the Nuclear Winter augment and remain inside its area so that every shot counts as Action-skill damage. Consequently, you trigger the passive Excited State, which guarantees a critical hit after Action-skill damage.

Since every shot becomes a critical, the build leverages the passive Critical Funding to get magazine refills on critical hits. In addition, the build stacks passives like Gamma Ray Burst, which buffs your next shot after re-triggering the Action skill via shield drain, to boost single-shot impact. Together, these mechanics let you fire sustained rockets and keep pressure on bosses or groups.

Cryo slam build

The cryo slam build comes from Termx’s blue-tree experimentation. It treats Harlowe’s Halo Accelerator (Action skill Zero-Point) as a continuous source of stasis and cryo damage. To keep the stasis bubble active, you run the Inertia augment; when a stasised enemy dies, Inertia places another enemy in stasis and resets the Action skill duration.

With a permanent stasis target, you repeatedly perform the slam attack produced by the bubble and scale damage with the capstone Cold Plunge. Cold Plunge creates a singularity that pulls enemies together and follows with a cryo explosion. This method clears mobs quickly and reliably. However, it is less effective on single big targets, so expect trade-offs when facing bosses.

Radiation Chroma Accelerator build

The red-tree build focuses on the Chroma Accelerator Action skill and augments that convert Action-skill damage into weapon damage. The key augment is Neutron Capture, which transfers part of the Action-skill damage to your gun as bonus radiation damage. This effectively buffs weapons after each Chroma detonation.

To increase nuke potency, the build stacks passives such as Field-Ready Prototype, Elementary, and Enriched, which all raise the Action-skill’s base damage or its downstream effects. The build is straightforward to use against single targets, and it does not require highly specific gear—though guns like the Cyclotron Anaretic Katagawa’s Revenge can improve clear speed and boss damage.

Where to start and additional resources

If you’re new to Kairos, start with a basic familiarity of Harlowe’s three gadgets and choose a tree that matches whether you like area-control, stasis play, or big single-hit nukes. Furthermore, watch the linked videos to see exact skill point distribution and recommended augments. Finally, for endgame play you may want to tune weapons and shield interactions to match the build’s mechanics.