HOI IV Open Beta Update V Patch Notes - May 2026

Paradox squeezed in one more update before taking a short break. Open Beta Update V for Hearts of Iron IV is live now under the open_beta branch, versioned as Case Green v1.18.1.0.9197, and the team is asking players to leave feedback while they're out.

The headline work is on the AI's naval behaviour, which has needed attention for a while. Italy's naval equipment gets an extensive rework, the AI will now train ships more consistently, and there's new logic stopping it from over-assigning patrols to naval invasion support. If you've ever watched the AI park its entire fleet on pointless patrol duty while an invasion goes unsupported, this should help. On the performance side, a fix targeting large-scale naval battles with 1,000-plus ships is in, which is the sort of thing that makes late-game multiplayer sessions actually playable rather than a slideshow.

Bugfixes cover the USA's inability to build 1940 CVs, strike forces getting stuck on invalid targets, incorrect snow modifier values, and a crash tied to carrier airplane deployment. Lend lease also defaults to max amounts now, which is a small but sensible quality-of-life change. Everything in the update is listed below.

Full Patch Notes

Generals!

Before we head out on our 4-Day LOA we wanted to give you another OB update. Give it a try, leave us a lot of feedback here, and we'll be back soon to take it all in and make potential adjustments.

How to join this Open Beta:

This beta client is Case Green v1.18.1.0.9197 (01c8)

To install Open Beta client, follow the instruction below:

Right-click the game in your library
Select Properties from the drop-down menu
Select Game Versions & Betas
Select the beta branch called open_beta

If you are already on the Open Beta client, you should get an update automatically.

Finally, to report any issues you find, in relation to this beta, please use the bug report forum and make sure to include the version you’re using. That way our Jira won’t go nuts trying to figure out what bug report belongs to what.

Open Beta Update V Notes

Gameplay

Made lend lease default to max amount for 'once' and to 100% for 'percentage' modes
Updated supply tooltip to show more careful where all supply is coming from

Stability & Performance

Fixed performance in very large scale naval battles (1000+ ships)
Fixed a dx11 rendering bug

AI

Fixed a bug where England could not build improved battleships
Extensive rework of italian naval equipment
The AI will now train their troops more often
Updated generic taskforces so they are a bit more sensible
The AI will try to train their ships a bit more opportunistic
The AI will be a bit more sensical with picking a homebase for its standby fleet
Added logic to prevent the AI from assigning too many patrols to support naval invasion

Modding

AI objectives will respect blocked naval regions now and not consider them for naval mission assignment anymore

Bugfixes

Fixed a bug where ships were partially considered for supply need
Fixed a bug where USA was unable to build 1940 CVs
Fixed a bug where a strike force sometimes gets stuck on an invalid target and stops working
Fixed a bug where wrong snow modifier values were shown + fixed a bug where the leader snow adjuster didnt work as intended
Snow attack penalty is now shown on the move-arrow tooltip
Removed legacy plane techs from BBA-enabled starts for 36 minor nations
RI Bolzano in the 1939 OOB now uses the correct ship_hull_cruiser_2 (Bolzano Class)
Convoy raiders won't join or reinforce a combat unless there are enemy convoy's to shoot at
Fixed a crash related to carrier airplanes being deployed

As you were!

(And try to leave this place in one piece while we're out!)