Field of Glory: Kingdoms - Companion patch out now

UI/UX, Map

Building Browser (MAJOR): Check all possible game buildings through this powerful new interface, accessible from any already built structure in the region panel.
Search functionality now supports partial match and switch to extended (full map) search if no result is found within your nation.
Changed draggable thickness to 50 px in several UIs.
Edict panel supports cultural variations for buildings.
Fix to a labeling issue with provincial mercenaries in the recruitment interface.
Fix to some missing links between eastern regions.
Extra column in the ledger for legacy.
A few unit scale fixes.
Clicking on a leader in the ledger, leader tab, will systematically move the camera to him/her.
Icons showing bonus XP levels and flat XP in the region panel.
In Region/Military (ledger), the tooltip indicates XP and XP level bonuses for produced units.
Added options to disable rumored sites.
50+ new sounds for buildings and impediments.
Fixed a few non-working achievements.
Improved trade filter.
Help panel can be closed with ESC.

Warfare

You can now recruit siege units with the "Recruit Non-standard Unit" RGD.
Complete overhaul of mercenary recruitments; actual units from neighboring nations are now used.
If you lose a sortie but still have units inside, the city is not lost.
Cultural militias.
Battle: Unit positioning refined further and more contextual.
Fix to newly split army within a city being considered outside.
Archers and crossbowmen levies don't require a bowyer.
Removed some discount bonuses on transport ships, not relevant (usually replaced by galleys).
Fix to some armies being repulsed wrongly when two opposing armies march against each other.
Units you have lent (e.g., to Crusaders) can provide vision one-third of the time.
No militia should be allowed to fly anymore (broom broom…).
Siege values in nation shield tooltip on unit panel.
Authority loss from lost SAUs did not work properly (beware!).
Fleets crossing each other's path (in opposite directions) can sometimes halt and engage in battle, with the rest of their movement being cancelled. This is subject to a dice roll, with a higher chance earlier in the turn.
High combat power garrisons (300+ CP) will never surrender at once, but first suffer attrition (until they fall under the threshold).

Buildings, Regions, Trade

Some buildings are dynamically replaced in setup if using a missing resource.
Master Herbalist and Master Ratcatcher had a bug preventing them from being built.
Flax Fields and Legume Fields can now be built in arid lands.
Made tribal/nomad ritual descriptions clearer.
Some structures changed their goods; notably, Prestige Clothier uses Dyes and a new building, Illuminator Atelier, uses Indigo.
New building: Underground Fortress, which is an extension to existing castles.
AI improves Tier I to Tier II much better and more frequently.
In some cases, populations were created without a culture.
Army Camp now adds +1 Effectiveness recovery at a cost of 5 XP.
Village Green is not removed at 20 population.
Chief's House provides a decent chance to trigger the Bonus Authority Event (overall limit of +3 Authority).
Fix to negative-production buildings being affected by productivity-reducing modifiers.
Fix to Master Herbalist and a few other buildings missing modifiers.
Secret Cult added as an “improved” Cult Site—you’ll like it.
Fix to buggy rituals.
Gypsy event building.
The first two fortifications for many tribals and nomads appear spontaneously only.
Fix to Dungeon Prison not working.
Fix to some units with malformed modifiers.

Religion

Fix to First Muslim not properly removed from previous bearer.
Improved religious distribution in the DLC campaign and Manzikert scenario.
Only ROTB religions get a penalty from other religion piety-producing buildings.

Dynasty, Nation-Level Features, Diplomacy

More mercenary impacts on coups for Byzance.
Spy networks can lift FOW in the nation they are deployed in (you get a message about this).
Parties don't deploy as leaders.
Max demesne size for progress increased from 2 to 3 for mini nations.
You can always DOW a vassal, even if already at war with their liege.
HRE: New members can join and existing ones can be expelled.
Newly formed vassals will always start at war with their liege opponent, as diplomacy is not an option.
Scandinavian people (except SWE) get the "To the Green Lands" perk; see the nation panel and new RGD (MAJOR).

Byzantine Civil Wars change:

The delay is longer the more civil wars have already occurred.
Intensity increases with the number of previous civil wars.
Each rebel comes from a disloyal character, if possible.
The AI will totally crumble if three or more civil wars have taken place, subject to an increased dice roll chance.
If the Seljuqs are at war and adjacent to the rebel, the rebel will become their vassal (automatically if the Byzantines are AI-controlled, 1/3 chance if human-controlled).

Don't cancel systematically both proposals when two “collide”; the human player has priority over the AI here.
You can now DOW anyone except allies. Sneak attack works the same.
Setup

Scotland has a more credible initial army in the main campaign.
Scottish burghs are rarer.
Extra traits given to some leaders for some nations (e.g., Seljuqs) could be duplicated—fixed.
Manifest Destiny rebalanced; Seljuqs have a bonus against Byzantines.
Nations starting as Khanates now start as Grand Hordes.
Seljuqs are not restricted anymore to some provinces.
Hungary can still recruit Hungarian Noble Lancers in the late-tier army list.
Alans are Orthodox.
Smaller scenarios always feature a boost for AI at higher difficulty levels.

Decisions

Some regional decisions can't have their odds tweaked: Sneak Attack, Mercenary Company, and [Reacted].
Develop Region RGD always provides bonus food and infrastructure.

Various
New seasonal turns possibility (modding, extra scenarios).