Hearts of Iron IV: Open Beta SE™ Update 3.03

Greetings, Commanders!

I am Zwirbaum, Game Designer for Hearts of Iron IV, welcoming you to another provisional update in our ongoing Open Beta series. This week, we are deploying a fresh batch of experimental features, balance adjustments, and mechanical tweaks. Please bear in mind that these additions are actively being evaluated and may or may not transition into the official release branch. Your gameplay impressions and constructive feedback are vital in helping us calibrate these systems moving forward.

As per tradition, you will find contextual developer insights interspersed throughout the patch notes below. Enjoy testing the new changes, and stay tuned for further developments on the horizon!

— Zwirbaum

A Quick Note from Core Tech:

Alongside the gameplay tweaks, we have introduced a low-level engine revision resolving computational discrepancies for extreme numeric values when calculating exponents, logarithms, and power functions. In standard, unmodded playthroughs, this change should remain practically invisible—unless you happen to deploy convoy escort or raiding operations across 33+ operational regions under a single admiral with only a single zone covered, in which case efficiency calculations have now been rectified.

Mod developers utilizing extreme numerical ranges or advanced mathematical functions are encouraged to verify their scripts against this build to ensure seamless compatibility with the improved floating-point precision.

— Pdxen

How to Access the Open Beta

Current Beta Build: Operation Postern v1.19.2.0.3eb1 (85f4)

To participate in this testing phase, please follow these steps:

1. Right-click Hearts of Iron IV in your Steam Library.
2. Navigate to Properties… from the context menu.
3. Select the Betas tab.
4. From the Beta Participation dropdown, select open_beta.

If you are already enrolled in the Open Beta branch, Steam will download the update automatically. Should you encounter any issues or anomalies, please submit a detailed report via the official Paradox Bug Report Forum, ensuring you cite the exact build version in your submission.

Patch Notes: Operation Postern v1.19.2.0.3eb1

Experimental Mechanics

Chassis Stat Multipliers

Equipment chassis can now dynamically apply specific multipliers to both additive and multiplicative module statistics. These modifiers can target isolated attributes (such as Soft Attack) or encompass a hull’s entire combat profile with designated potency. (Note: This is an experimental feature currently localized exclusively in English and remains subject to adjustment or reversal.)

• Interwar Chassis (Light, Medium, Heavy): Incurs a -5% penalty to Soft Attack, Hard Attack, and Air Attack on module additive values.
• Improved Chassis (Light, Medium, Heavy): Grants a +5% bonus to Soft Attack, Hard Attack, and Air Attack on module additive values.
• Advanced Chassis (Light, Medium, Heavy): Grants a +10% bonus to Soft Attack, Hard Attack, and Air Attack on module additive values.
• Modern Tank Chassis: Receives a +12.5% bonus to Soft Attack, Hard Attack, and Air Attack on module additive values.

Developer Commentary: Following previous efforts to diminish the performance disparity between specialized armor variants, our current focus is addressing the general sentiment that dedicated armored formations lack competitive punch. By introducing chassis-tier scaling, we aim to provide meaningful incentives for players to commit industrial and scientific resources toward researching and deploying higher-tier hulls rather than perpetually relying on foundational interwar designs. This also elongates the operational viability window of light armor early on.

Reliability-Scaled Survivability (HP Scaling)

Equipment statistics can now scale dynamically with the overall Reliability rating. The effect scales linearly between 0 and 1 (where 0% Reliability delivers 0% of the allocated stat block, and 100% Reliability unlocks the full 100%). Excluded parameters: Base Reliability, Reliability Factor, Carrier Deck Size, and Production Cost (IC). (Experimental, localized in English only).

• Standard Tank Chassis (Excluding Super-Heavy/Land Cruisers): Gain +0.5 base HP that scales with Reliability. At 100%+ Reliability, this elevates unit HP across Light, Medium, Heavy, Amphibious, and Super-Heavy armor from 2.0 to 3.5 HP.
• Line Combat Variants (TD, SPAA, SPART): Base HP adjusted from 0.6 to 0.5. Reaching 100%+ Reliability increases effective HP up to 1.25 (previously 0.6).
• Regimental Support Variants (Support TD, Support SPAA): Base HP adjusted from 0.2 to 0.1. Reaching 100%+ Reliability increases effective HP up to 0.65 (previously 0.2).

Developer Commentary: This mechanic reinforces the strategic value of Reliability while bolstering late-game armor durability. Balancing armor designs to avoid critical reliability penalties now directly correlates with operational longevity and field sustainment. Units designed with high reliability thresholds will experience considerably lower attrition and combat losses over extended engagements.

Armor & Combat Role Standardization

• Line Tank Destroyers, Self-Propelled Anti-Air & Self-Propelled Artillery: Breakthrough modifier standardized across all weight classes to a fixed -75%.
• Regimental Tank Destroyers & Regimental Self-Propelled Anti-Air: Breakthrough modifier standardized across all weight classes to a fixed -90%.
• Tank Destroyers & Self-Propelled Artillery: Now receive a standardized +25% Defense bonus across all weight classes.
• Regimental Tank Destroyers: Defense penalty softened to a standardized -33% across all weight classes.

Developer Commentary: Specialized combat vehicles had increasingly begun substituting for frontline battle tanks. By sharply limiting their breakthrough capabilities while reinforcing their defensive efficacy, we are re-anchoring these variants into dedicated tactical support and defensive anti-tank/fire-support roles.

Doctrines & Projects

Land Doctrines

• Large Unit Tactics (Adoption Bonus): Supply reduction modifier now applies strictly to Leg Infantry (previously affected all Infantry, Motorized, and Mechanized battalions).
• Large Unit Tactics (Reward 4): Bonus profile shifted to benefit Leg Infantry exclusively.
• Mobile Infantry (Reward 2): Added a +10% Soft Attack bonus across all Infantry, Motorized, and Mechanized forces.
• Mobile Infantry (Reward 4): Soft Attack bonus replaced with a +10% Breakthrough increase for Motorized and Mechanized Infantry.
• Mobile Warfare (Armor Milestone): Now grants an additional +15% Breakthrough modifier army-wide.
• Mass Assault (Operations Milestone): Minimum Training Level reduction boosted from -5% to -10%.
• Mass Assault (Artillery & Combat Support Milestone): Replaced the -5% Minimum Training Level with a +2% Reinforce Rate.

Developer Commentary: Large Unit Tactics previously stood as an undisputed dominant choice among infantry sub-doctrines. Restricting its key logistics bonuses to Leg Infantry preserves the core theme of massive infantry mobilizations without disproportionately empowering mechanized mobile forces.

Air Doctrines & Special Projects

• Strategic Destruction (Fighter Milestone): Interception Mission Efficiency bonus reduced to +15%.
• Proximity Fuzes: Naval Anti-Air combat modifier reduced to +15%.

Tank Modules

• Rocket Launcher: Breakthrough adjusted from -2 to +4; added +4 Defense; Hard Attack increased to 4.
• Improved Rocket Launcher: Breakthrough adjusted from -2 to +8; added +8 Defense; Hard Attack increased to 6.
• Anti-Air 2: Air Attack reduced from 32 to 30.
• Anti-Air 3: Air Attack reduced from 46 to 42.
• Easy Maintenance: Production cost (IC) discount reduced from -7.5% to -5%; XP unlock cost lowered from 30 to 20; Reliability bonus adjusted to +7.5%.
• Cast Armor: Now grants an additional +10% HP.
• Sloped Armor: Now grants an additional +5% HP.
• Welded Armor: Now grants an additional +5% HP.
• Auto-Loader: Added +2% Soft Attack and +2% Air Attack.
• Stabilizer: Added +4% Hard Attack.
• Smoke Launchers: Breakthrough increased from 1 to 2.
• Extra Ammunition Storage: Defense increased to 5; Breakthrough increased to 3.

Developer Commentary: Easy Maintenance had become a near-mandatory selection across vehicle designs due to the compounding benefits of stacking cost-reduction modifiers. Moderating this module prevents excessive industrial compounding and keeps alternative utility modules viable.

Land Units & Technologies

• Bicycle Infantry: Support Equipment requirement halved from 10 to 5.
• Motorized Infantry: Hit Points increased to 27.5.
• Mechanized Infantry: Removed the baseline +10% Soft Attack bonus.
• Amphibious Mechanized Infantry: Removed the baseline +10% Soft Attack bonus.
• Cavalry: Now features a +20% Breakthrough bonus.
• Subunit Durability: Line Artillery, Motorized Artillery, Rocket/Motorized/Truck-Drawn Rocket Artillery, Anti-Tank, Anti-Air, Motorized Anti-Tank, and Motorized Anti-Air unit HP increased to 1.6.
• Technologies: Improved Infantry Equipment I & II now grant a +10% Soft Attack bonus to Motorized and Mechanized Infantry (up from +5%).

Bug Fixes & Technical Improvements

• Rollback: Reverted the restriction preventing Amphibious Tanks from fitting upsized main armaments via Fixed Superstructures due to secondary technical issues. This restriction will return once thoroughly stabilized.
• Trade Interdiction: Submarine Milestone flat attack bonus (+0.1) correctly converted to Submarine Torpedo Attack +10%.
• Marine Commando (Reward 5): Fixed an issue to ensure Pioneers accurately supply the intended +15% Armor bonus to Amphibious Armor.
• Out-of-Sync (OOS): Resolved an issue where mods using exceptionally high numerical values could trigger multiplayer synchronization drops.
• Modding Precision: Enhanced algorithmic precision across the core exp, log, and pow engine functions.

Source