Arknights Endfield Base Expansion Unlock Guide and Increasing Build Space

What to know

• Base expansion unlocks at Authority Level 15 through main story progression.
• You must complete the AIC Steward mission to enable upgrades.
• A new owl-like support bot at your base handles expansion options.
• Expanding increases space for production, crafting, and late-game infrastructure.

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Expanding your base in Arknights Endfield is one of the most important milestones for long-term progression. As your operations scale, your initial buildable area quickly becomes restrictive. Increasing your base size unlocks more room for advanced facilities, automation setups, depot logistics, and higher-tier production chains. If you are aiming to optimize resource output or prepare for late-game challenges, expanding your base is not optional; it is essential.

Arknights Endfield base expansion requirements

Requirement	Details	Why It Matters
Story Progression	Advance main campaign	Unlocks Authority progression
Authority Level	Reach Level 15	Advance the main campaign
Special Mission	Complete AIC Steward	Enables base upgrade system
NPC Interaction	Speak to owl support bot	Access “Expand Base Area” option
Upgrade Currency	In-game credits	Used to purchase expansion tiers

Reaching Authority Level 15 is the core gating requirement. Authority increases naturally as you complete story objectives, side tasks, and structured missions. You cannot shortcut this requirement; it is directly tied to narrative progression and system unlocks. Once you hit Level 15, the game introduces the AIC Steward mission, which functions as the activation key for base upgrades.

After completing the AIC Steward mission, you will notice a new support unit near your base — an owl-like robotic assistant. This unit serves as your base expansion interface. Interacting with it reveals new upgrade options, including the critical “Expand Base Area” selection. Choosing this option increases your buildable boundaries, allowing additional infrastructure placement.

How base area expansion works mechanically

Base expansion increases the white-dotted build perimeter visible around your headquarters. This enlarged perimeter directly translates into more construction slots for crafting stations, production modules, depot systems, and automation layouts. Without expansion, your base quickly becomes inefficient due to cramped placement and limited logistical flow.

Each expansion tier requires credits. The first tier is relatively affordable, while later tiers demand significant investment. Planning your resource economy before purchasing higher tiers ensures you do not stall other upgrades.

Current upgrade tiers and costs

Upgrade Category	Tier	Cost (Credits)	Status
Core AIC Area Size	Area Expansion I	20,000	Available after unlock
Core AIC Area Size	Area Expansion II	160,000	Higher-tier unlock
Depot Bus Construction	Depot Bus I	5,000	Locked initially
Depot Bus Construction	Depot Bus II	20,000	Progressive unlock
Depot Bus Construction	Depot Bus III	40,000	Progressive unlock
Depot Bus Construction	Depot Bus IV	80,000	Progressive unlock
Depot Bus Construction	Depot Bus V	160,000	Late-game tier

The Core AIC Area Size upgrades directly increase your buildable territory. Meanwhile, the Depot Bus Construction upgrades expand logistical throughput and automation efficiency within your base. These systems work together. A larger base without proper depot routing results in inefficiency, while advanced depot systems require sufficient physical space to operate effectively.

Why expanding your base matters for late-game progression

In early stages, you can operate with minimal facilities. However, as you unlock higher-tier crafting recipes and automation systems, your base must support parallel production chains. Expansion enables better layout optimization, reduces congestion, and allows separation between resource processing, storage, and advanced fabrication.

Larger base areas also improve defensive planning. More room means better turret placement, clearer traffic lanes, and improved reaction time against threats. If you plan to focus on high-efficiency production builds, expansion becomes even more critical because compact builds limit conveyor routing and storage buffering.

Economic considerations before upgrading

Before purchasing Area Expansion II, evaluate your current production output. The 160,000 credit investment is substantial. Ideally, your base should already have optimized crafting loops and steady income generation. If you upgrade prematurely without production support, you may struggle to capitalize on the added space.

A practical approach is to first stabilize automation through Depot Bus upgrades, then expand area size once your throughput demands more space. This ensures the expansion translates into real efficiency gains rather than unused territory.

What changes visually after expansion

When you complete an area upgrade, the white boundary lines marking your construction zone extend outward. The change is immediate and permanent. You gain additional build tiles, allowing more structured layouts. The terrain inside the expanded area becomes fully usable for construction, provided it is not obstructed by permanent environmental features.

Common issues players encounter

Some players reach Authority Level 15 but do not see expansion options. This typically occurs because the AIC Steward mission has not been completed. Without finishing this mission, the owl support bot and expansion interface remain inaccessible. Always verify mission completion before troubleshooting further.

Another issue involves insufficient credits. Expansion costs scale quickly, so maintaining steady resource inflow is crucial. Optimizing crafting loops and completing side contracts can significantly improve your financial stability.