diff --git a/src/lib/base/index.ts b/src/lib/base/index.ts
new file mode 100644
index 0000000..6f93534
--- /dev/null
+++ b/src/lib/base/index.ts
@@ -0,0 +1,11 @@
+export { upgradeStructure } from "./upgrade";
+export { assertStaffHiringEnabled, fireStaff, hireStaff, setLaborHeadcount } from "./staffing";
+export { processBaseTick } from "./tick";
+export type {
+  BaseTickResult,
+  HireStaffInput,
+  LaborClassificationOption,
+  SetLaborHeadcountInput,
+  StaffingPositionType,
+  StructureStaffingOption,
+} from "./types";
diff --git a/src/lib/base/staffing.ts b/src/lib/base/staffing.ts
new file mode 100644
index 0000000..735650c
--- /dev/null
+++ b/src/lib/base/staffing.ts
@@ -0,0 +1,337 @@
+import type { Payload } from "payload";
+import type { NpcStaffing } from "@/payload-types";
+import { emitGameEvent } from "@/utils/event-log/emit";
+import { EventTypes } from "@/utils/event-log/eventTypes";
+import { relationshipId } from "./storage";
+import type { HireStaffInput, SetLaborHeadcountInput } from "./types";
+
+export async function assertStaffHiringEnabled(payload: Payload): Promise<void> {
+  const rules = await payload.findGlobal({
+    slug: "game-rules",
+    depth: 0,
+    overrideAccess: true,
+  });
+  if (!rules.staffHiringEnabled) {
+    throw new Error(
+      rules.staffHiringDisabledMessage?.trim() || "Staff hiring is currently disabled.",
+    );
+  }
+}
+
+function staffingPositionType(value: string): "administrative" | "technical" | "other" {
+  switch (value) {
+    case "administrative":
+    case "technical":
+    case "other":
+      return value;
+    default:
+      throw new Error("Invalid staff position type.");
+  }
+}
+
+export async function hireStaff(
+  payload: Payload,
+  input: HireStaffInput,
+  actorUserId?: number,
+): Promise<NpcStaffing> {
+  await assertStaffHiringEnabled(payload);
+  if (input.positionType === "labor") {
+    throw new Error("Basic labor is tracked by headcount — use the labor count control instead.");
+  }
+  const positionType = staffingPositionType(input.positionType);
+  const npc = await payload
+    .findByID({ collection: "game-npcs", id: input.npcId, depth: 0, overrideAccess: true })
+    .catch(() => null);
+  if (!npc) throw new Error("NPC not found.");
+  const structure = await payload
+    .findByID({
+      collection: "game-structures",
+      id: input.structureId,
+      depth: 0,
+      overrideAccess: true,
+    })
+    .catch(() => null);
+  if (!structure) throw new Error("Structure not found.");
+
+  const positionRule = structure.staffPositions?.find(
+    (position) => position.positionType === positionType,
+  );
+  if (!positionRule) {
+    throw new Error(`This structure does not accept ${positionType} staff.`);
+  }
+
+  if (positionRule.max !== null && positionRule.max !== undefined) {
+    const activeAtStructure = await payload.find({
+      collection: "npc-staffing",
+      where: {
+        and: [
+          { structure: { equals: structure.id } },
+          { positionType: { equals: positionType } },
+          { npc: { exists: true } },
+          { status: { equals: "active" } },
+        ],
+      },
+      limit: 0,
+      depth: 0,
+      overrideAccess: true,
+    });
+    if (activeAtStructure.totalDocs >= positionRule.max) {
+      throw new Error(`This structure has reached its ${positionType} staff limit.`);
+    }
+  }
+
+  const existing = await payload.find({
+    collection: "npc-staffing",
+    where: { and: [{ npc: { equals: npc.id } }, { status: { equals: "active" } }] },
+    limit: 1,
+    depth: 1,
+    overrideAccess: true,
+  });
+  if (existing.docs[0]) {
+    const assignment = existing.docs[0];
+    const assignedStructure = assignment.structure;
+    const structureName =
+      typeof assignedStructure === "object"
+        ? assignedStructure.name
+        : `structure #${assignedStructure}`;
+    throw new Error(
+      `${npc.name} is already employed as ${assignment.positionTitle} at ${structureName}.`,
+    );
+  }
+
+  const staffing = await payload.create({
+    collection: "npc-staffing",
+    data: {
+      npc: npc.id,
+      structure: structure.id,
+      positionType,
+      positionTitle: input.positionTitle,
+      salary: positionRule.enforcedSalary ?? input.salary,
+      headcount: 1,
+      status: "active",
+      hiredAt: new Date().toISOString(),
+    },
+    overrideAccess: true,
+  });
+  await payload.update({
+    collection: "game-npcs",
+    id: npc.id,
+    data: { location: structure.id, isInGame: true },
+    overrideAccess: true,
+  });
+  await emitGameEvent(payload, {
+    type: EventTypes.StaffHired,
+    message: `${npc.name} hired as ${staffing.positionTitle} at ${structure.name}`,
+    actor: actorUserId,
+    structure: structure.id,
+    targetCollection: "npc-staffing",
+    targetId: staffing.id,
+    data: { salary: staffing.salary ?? 0, npcId: npc.id },
+  });
+  return staffing;
+}
+
+export async function setLaborHeadcount(
+  payload: Payload,
+  input: SetLaborHeadcountInput,
+): Promise<{ readonly id: number | null }> {
+  await assertStaffHiringEnabled(payload);
+  if (!Number.isInteger(input.headcount) || input.headcount < 0) {
+    throw new Error("Headcount must be a whole number of 0 or more.");
+  }
+  if (!Number.isFinite(input.unitSalary) || input.unitSalary < 0) {
+    throw new Error("Wage cannot be negative.");
+  }
+  const classification = await payload
+    .findByID({
+      collection: "labor-classifications",
+      id: input.classificationId,
+      depth: 0,
+      overrideAccess: true,
+    })
+    .catch(() => null);
+  if (!classification) throw new Error("Unknown labor classification.");
+  const structure = await payload
+    .findByID({
+      collection: "game-structures",
+      id: input.structureId,
+      depth: 0,
+      overrideAccess: true,
+    })
+    .catch(() => null);
+  if (!structure) throw new Error("Structure not found.");
+
+  const requirement = structure.laborRequirements?.find(
+    (entry) => relationshipId(entry.classification) === classification.id,
+  );
+  if (!requirement) {
+    throw new Error(`This structure does not accept ${classification.name} crews.`);
+  }
+
+  const existing = await payload.find({
+    collection: "npc-staffing",
+    where: {
+      and: [
+        { structure: { equals: structure.id } },
+        { positionType: { equals: "labor" } },
+        { laborClassification: { equals: classification.id } },
+        { status: { equals: "active" } },
+      ],
+    },
+    limit: 1,
+    depth: 0,
+    overrideAccess: true,
+  });
+  const staffing = existing.docs[0];
+  const classificationLabel = classification.name;
+  const currentHeadcount = staffing?.headcount ?? 0;
+  const maxHeadcount = requirement.maxHeadcount ?? 0;
+  const unitSalary = requirement.enforcedSalary ?? input.unitSalary;
+
+  if (input.headcount > maxHeadcount) {
+    throw new Error(
+      `${classificationLabel} crews are capped at ${maxHeadcount} for this structure.`,
+    );
+  }
+
+  const headcountDelta = input.headcount - currentHeadcount;
+  const availableHeadcount = classification.availableHeadcount ?? 0;
+  const marketRate = classification.defaultUnitSalary ?? 0;
+  const wageFactor = marketRate > 0 ? Math.min(1, unitSalary / marketRate) : 1;
+  const effectiveAvailable = Math.floor(availableHeadcount * wageFactor);
+  if (headcountDelta > effectiveAvailable) {
+    throw new Error(
+      `Only ${effectiveAvailable} ${classificationLabel} workers are available at this wage.`,
+    );
+  }
+
+  if (input.headcount <= 0) {
+    if (staffing) {
+      await payload.update({
+        collection: "npc-staffing",
+        id: staffing.id,
+        data: { status: "terminated", terminatedAt: new Date().toISOString() },
+        overrideAccess: true,
+      });
+      await payload.update({
+        collection: "labor-classifications",
+        id: classification.id,
+        data: { availableHeadcount: availableHeadcount + currentHeadcount },
+        overrideAccess: true,
+      });
+      await emitGameEvent(payload, {
+        type: EventTypes.StaffTerminated,
+        message: `${classificationLabel} crew released at ${structure.name}`,
+        structure: structure.id,
+        targetCollection: "npc-staffing",
+        targetId: staffing.id,
+      });
+    }
+    return { id: null };
+  }
+
+  const data = {
+    npc: null,
+    structure: structure.id,
+    positionType: "labor" as const,
+    laborClassification: classification.id,
+    positionTitle: `${classificationLabel} Labor`,
+    salary: unitSalary,
+    headcount: input.headcount,
+    status: "active" as const,
+  };
+  const updated = staffing
+    ? await payload.update({
+        collection: "npc-staffing",
+        id: staffing.id,
+        data,
+        overrideAccess: true,
+      })
+    : await payload.create({
+        collection: "npc-staffing",
+        data: { ...data, hiredAt: new Date().toISOString() },
+        overrideAccess: true,
+      });
+  if (headcountDelta !== 0) {
+    await payload.update({
+      collection: "labor-classifications",
+      id: classification.id,
+      data: { availableHeadcount: availableHeadcount - headcountDelta },
+      overrideAccess: true,
+    });
+  }
+  await emitGameEvent(payload, {
+    type: EventTypes.StaffHeadcountSet,
+    message: `${classificationLabel} crew set to ${input.headcount} at ${structure.name} ($${unitSalary}/worker per tick)`,
+    structure: structure.id,
+    targetCollection: "npc-staffing",
+    targetId: updated.id,
+    data: {
+      classification: classification.key,
+      headcount: input.headcount,
+      unitSalary,
+    },
+  });
+  return { id: updated.id };
+}
+
+export async function fireStaff(
+  payload: Payload,
+  staffingId: number,
+  actorUserId?: number,
+): Promise<NpcStaffing> {
+  const staffing = await payload
+    .findByID({ collection: "npc-staffing", id: staffingId, depth: 1, overrideAccess: true })
+    .catch(() => null);
+  if (!staffing) throw new Error("Staff assignment not found.");
+  if (staffing.status !== "active") {
+    throw new Error("This staff assignment is already terminated.");
+  }
+
+  const npcId = relationshipId(staffing.npc);
+  const structureId = relationshipId(staffing.structure);
+  const laborClassificationId = relationshipId(staffing.laborClassification);
+  const npcName =
+    typeof staffing.npc === "object" && staffing.npc !== null
+      ? staffing.npc.name
+      : staffing.positionTitle;
+  const updated = await payload.update({
+    collection: "npc-staffing",
+    id: staffing.id,
+    data: { status: "terminated", terminatedAt: new Date().toISOString() },
+    overrideAccess: true,
+  });
+  if (npcId !== null) {
+    await payload.update({
+      collection: "game-npcs",
+      id: npcId,
+      data: { location: null, isInGame: false },
+      overrideAccess: true,
+    });
+  }
+  if (npcId === null && laborClassificationId !== null) {
+    const classification = await payload.findByID({
+      collection: "labor-classifications",
+      id: laborClassificationId,
+      depth: 0,
+      overrideAccess: true,
+    });
+    await payload.update({
+      collection: "labor-classifications",
+      id: classification.id,
+      data: {
+        availableHeadcount: (classification.availableHeadcount ?? 0) + (staffing.headcount ?? 1),
+      },
+      overrideAccess: true,
+    });
+  }
+  await emitGameEvent(payload, {
+    type: EventTypes.StaffTerminated,
+    message: `${npcName}'s assignment as ${staffing.positionTitle} was terminated`,
+    actor: actorUserId,
+    structure: structureId ?? undefined,
+    targetCollection: "npc-staffing",
+    targetId: staffing.id,
+  });
+  return updated;
+}
diff --git a/src/lib/base/storage.ts b/src/lib/base/storage.ts
new file mode 100644
index 0000000..46d8e19
--- /dev/null
+++ b/src/lib/base/storage.ts
@@ -0,0 +1,42 @@
+import type { Payload } from "payload";
+import type { GameStructure, Resource } from "@/payload-types";
+
+type StorageEntry = NonNullable<GameStructure["storedResources"]>[number];
+
+export function relationshipId(
+  value: number | { id: number } | null | undefined,
+): number | null {
+  if (typeof value === "number") return value;
+  return value?.id ?? null;
+}
+
+export function storedAmount(entries: readonly StorageEntry[], resourceId: number): number {
+  return entries.reduce((total, entry) => {
+    return total + (relationshipId(entry.resource) === resourceId ? entry.amount : 0);
+  }, 0);
+}
+
+export function consumeStorage(
+  entries: readonly StorageEntry[],
+  resourceId: number,
+  requested: number,
+): { readonly entries: StorageEntry[]; readonly remaining: number } {
+  let remaining = requested;
+  const updated = entries
+    .map((entry) => {
+      if (remaining <= 0 || relationshipId(entry.resource) !== resourceId) return entry;
+      const consumed = Math.min(entry.amount, remaining);
+      remaining -= consumed;
+      return { ...entry, amount: entry.amount - consumed };
+    })
+    .filter((entry) => entry.amount > 0);
+  return { entries: updated, remaining };
+}
+
+export async function resourceName(payload: Payload, resource: number | Resource): Promise<string> {
+  if (typeof resource === "object") return resource.name;
+  const document = await payload
+    .findByID({ collection: "resources", id: resource, depth: 0, overrideAccess: true })
+    .catch(() => null);
+  return document?.name ?? `Resource #${resource}`;
+}
diff --git a/src/lib/base/types.ts b/src/lib/base/types.ts
new file mode 100644
index 0000000..1eab60f
--- /dev/null
+++ b/src/lib/base/types.ts
@@ -0,0 +1,51 @@
+export type HireStaffInput = {
+  readonly npcId: number;
+  readonly structureId: number;
+  readonly positionType: string;
+  readonly positionTitle: string;
+  readonly salary: number;
+};
+
+export type LaborClassificationOption = {
+  readonly id: number;
+  readonly name: string;
+  readonly key: string;
+  readonly defaultUnitSalary: number | null;
+  readonly availableHeadcount: number;
+};
+
+export type StaffingPositionType = "administrative" | "technical" | "other";
+
+export type StructureStaffingOption = {
+  readonly id: number;
+  readonly name: string;
+  readonly maintenanceCost: number;
+  readonly laborRequirements: readonly {
+    readonly classificationId: number;
+    readonly requiredHeadcount: number;
+    readonly maxHeadcount: number;
+    readonly enforcedSalary: number | null;
+    readonly currentHeadcount: number;
+  }[];
+  readonly staffPositions: readonly {
+    readonly positionType: StaffingPositionType;
+    readonly max: number | null;
+    readonly enforcedSalary: number | null;
+    readonly currentHeadcount: number;
+  }[];
+};
+
+export type SetLaborHeadcountInput = {
+  readonly structureId: number;
+  readonly classificationId: number;
+  readonly headcount: number;
+  readonly unitSalary: number;
+};
+
+export type BaseTickResult = {
+  readonly salariesPaid: number;
+  readonly salariesUnpaid: number;
+  readonly maintenancePaid: number;
+  readonly maintenanceUnpaid: number;
+  readonly upkeepShortages: number;
+};
diff --git a/src/lib/base/upgrade.ts b/src/lib/base/upgrade.ts
new file mode 100644
index 0000000..5346300
--- /dev/null
+++ b/src/lib/base/upgrade.ts
@@ -0,0 +1,91 @@
+import type { Payload } from "payload";
+import type { GameStructure, Structure } from "@/payload-types";
+import { emitGameEvent } from "@/utils/event-log/emit";
+import { EventTypes } from "@/utils/event-log/eventTypes";
+import { staffingDefaultsFromBlueprint } from "./staffingDefaults";
+import { consumeStorage, relationshipId, resourceName, storedAmount } from "./storage";
+
+async function structureBlueprint(payload: Payload, source: GameStructure): Promise<Structure> {
+  if (typeof source.type === "object") return source.type;
+  return payload.findByID({
+    collection: "structures",
+    id: source.type,
+    depth: 2,
+    overrideAccess: true,
+  });
+}
+
+export async function upgradeStructure(
+  payload: Payload,
+  gameStructureId: number,
+): Promise<GameStructure> {
+  const gameStructure = await payload.findByID({
+    collection: "game-structures",
+    id: gameStructureId,
+    depth: 2,
+    overrideAccess: true,
+  });
+  const source = await structureBlueprint(payload, gameStructure);
+  const targetReference = source.upgradesInto;
+  if (!targetReference) throw new Error("This structure has no upgrade path.");
+
+  const target =
+    typeof targetReference === "object"
+      ? targetReference
+      : await payload.findByID({
+          collection: "structures",
+          id: targetReference,
+          depth: 2,
+          overrideAccess: true,
+        });
+  const multiplier = source.upgradeCostMultiplier ?? 1;
+  const requirements = new Map<number, { needed: number; name: string }>();
+
+  for (const material of target.materials) {
+    const resourceId = relationshipId(material.resource);
+    if (resourceId === null) continue;
+    const current = requirements.get(resourceId);
+    requirements.set(resourceId, {
+      needed: (current?.needed ?? 0) + Math.ceil((material.amount ?? 0) * multiplier),
+      name: current?.name ?? (await resourceName(payload, material.resource)),
+    });
+  }
+
+  let storedResources = [...(gameStructure.storedResources ?? [])];
+  let voidStorage = [...(gameStructure.voidStorage ?? [])];
+  const shortages: string[] = [];
+  for (const [resourceId, requirement] of requirements) {
+    const available =
+      storedAmount(storedResources, resourceId) + storedAmount(voidStorage, resourceId);
+    if (available < requirement.needed) {
+      shortages.push(`${requirement.name} (have ${available}, need ${requirement.needed})`);
+    }
+  }
+  if (shortages.length > 0) throw new Error(`Missing materials: ${shortages.join(", ")}`);
+
+  for (const [resourceId, requirement] of requirements) {
+    const storedResult = consumeStorage(storedResources, resourceId, requirement.needed);
+    storedResources = storedResult.entries;
+    voidStorage = consumeStorage(voidStorage, resourceId, storedResult.remaining).entries;
+  }
+
+  const updated = await payload.update({
+    collection: "game-structures",
+    id: gameStructure.id,
+    data: {
+      type: target.id,
+      storedResources,
+      voidStorage,
+      ...staffingDefaultsFromBlueprint(target),
+    },
+    overrideAccess: true,
+  });
+  await emitGameEvent(payload, {
+    type: EventTypes.StructureUpgraded,
+    message: `Structure "${gameStructure.name}" upgraded to ${target.name}`,
+    structure: gameStructure.id,
+    targetCollection: "game-structures",
+    targetId: gameStructure.id,
+  });
+  return updated;
+}