From 368fd6d7ad626a3580638c42c493893b43950dff Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Hartmut=20N=C3=B6renberg?= <hn@hartmut-noerenberg.com>
Date: Sun, 15 Mar 2026 09:29:12 +0100
Subject: [PATCH] feat: calculation rules engine for decoupled cost attribution
 and chargeability

Introduces an admin-configurable rules engine that determines per-day cost
attribution (CHARGE/ZERO/REDUCE) and chargeability reporting (COUNT/SKIP)
for absence types (sick, vacation, public holiday). Includes shared types,
Zod schemas, Prisma model, rule matching with specificity scoring, default
rules, calculator integration, CRUD API router, seed data, chargeability
report integration, and admin UI.

283/283 engine tests, 209/209 API tests, 0 TS errors.

Co-Authored-By: claude-flow <ruv@ruv.net>
---
 .../(app)/admin/calculation-rules/page.tsx    |   5 +
 .../admin/CalculationRulesClient.tsx          | 356 ++++++++++++++++++
 packages/api/src/router/calculation-rules.ts  |  95 +++++
 .../api/src/router/chargeability-report.ts    |  80 +++-
 packages/api/src/router/index.ts              |   2 +
 packages/api/src/router/timeline.ts           | 147 ++++++--
 packages/db/prisma/schema.prisma              |  50 +++
 packages/db/src/seed.ts                       |  35 ++
 .../src/__tests__/calculator-rules.test.ts    | 243 ++++++++++++
 .../engine/src/__tests__/rules-engine.test.ts | 148 ++++++++
 packages/engine/src/allocation/calculator.ts  | 109 +++++-
 packages/engine/src/budget/monitor.ts         |  10 +-
 .../engine/src/chargeability/calculator.ts    |   7 +-
 packages/engine/src/index.ts                  |   1 +
 packages/engine/src/rules/default-rules.ts    |  60 +++
 packages/engine/src/rules/engine.ts           |  91 +++++
 packages/engine/src/rules/index.ts            |   3 +
 .../src/schemas/calculation-rules.schema.ts   |  22 ++
 packages/shared/src/schemas/index.ts          |   1 +
 .../shared/src/types/calculation-rules.ts     |  32 ++
 packages/shared/src/types/engine.ts           |  22 ++
 packages/shared/src/types/index.ts            |   1 +
 plan.md                                       | 286 ++++++++++++++
 23 files changed, 1753 insertions(+), 53 deletions(-)
 create mode 100644 apps/web/src/app/(app)/admin/calculation-rules/page.tsx
 create mode 100644 apps/web/src/components/admin/CalculationRulesClient.tsx
 create mode 100644 packages/api/src/router/calculation-rules.ts
 create mode 100644 packages/engine/src/__tests__/calculator-rules.test.ts
 create mode 100644 packages/engine/src/__tests__/rules-engine.test.ts
 create mode 100644 packages/engine/src/rules/default-rules.ts
 create mode 100644 packages/engine/src/rules/engine.ts
 create mode 100644 packages/engine/src/rules/index.ts
 create mode 100644 packages/shared/src/schemas/calculation-rules.schema.ts
 create mode 100644 packages/shared/src/types/calculation-rules.ts
 create mode 100644 plan.md

diff --git a/apps/web/src/app/(app)/admin/calculation-rules/page.tsx b/apps/web/src/app/(app)/admin/calculation-rules/page.tsx
new file mode 100644
index 0000000..40e39f9
--- /dev/null
+++ b/apps/web/src/app/(app)/admin/calculation-rules/page.tsx
@@ -0,0 +1,5 @@
+import { CalculationRulesClient } from "~/components/admin/CalculationRulesClient.js";
+
+export default function CalculationRulesPage() {
+  return <CalculationRulesClient />;
+}
diff --git a/apps/web/src/components/admin/CalculationRulesClient.tsx b/apps/web/src/components/admin/CalculationRulesClient.tsx
new file mode 100644
index 0000000..7d7e586
--- /dev/null
+++ b/apps/web/src/components/admin/CalculationRulesClient.tsx
@@ -0,0 +1,356 @@
+"use client";
+
+import { useState } from "react";
+import { trpc } from "~/lib/trpc/client.js";
+
+const TRIGGER_TYPES = ["SICK", "VACATION", "PUBLIC_HOLIDAY", "CUSTOM"] as const;
+const COST_EFFECTS = ["CHARGE", "ZERO", "REDUCE"] as const;
+const CHARGEABILITY_EFFECTS = ["COUNT", "SKIP"] as const;
+const ORDER_TYPES = ["BD", "CHARGEABLE", "INTERNAL", "OVERHEAD"] as const;
+
+const TRIGGER_LABELS: Record<string, string> = {
+  SICK: "Sick Leave",
+  VACATION: "Vacation",
+  PUBLIC_HOLIDAY: "Public Holiday",
+  CUSTOM: "Custom",
+};
+
+const COST_LABELS: Record<string, string> = {
+  CHARGE: "Charge to Project",
+  ZERO: "No Project Cost",
+  REDUCE: "Reduced Cost",
+};
+
+const CHG_LABELS: Record<string, string> = {
+  COUNT: "Person Chargeable",
+  SKIP: "Not Chargeable",
+};
+
+type RuleRow = {
+  id: string;
+  name: string;
+  description: string | null;
+  triggerType: string;
+  projectId: string | null;
+  orderType: string | null;
+  costEffect: string;
+  costReductionPercent: number | null;
+  chargeabilityEffect: string;
+  priority: number;
+  isActive: boolean;
+  project?: { id: string; name: string; shortCode: string } | null;
+};
+
+type EditingRule = {
+  id?: string;
+  name: string;
+  description: string;
+  triggerType: string;
+  projectId: string;
+  orderType: string;
+  costEffect: string;
+  costReductionPercent: number;
+  chargeabilityEffect: string;
+  priority: number;
+  isActive: boolean;
+};
+
+const emptyRule: EditingRule = {
+  name: "",
+  description: "",
+  triggerType: "SICK",
+  projectId: "",
+  orderType: "",
+  costEffect: "ZERO",
+  costReductionPercent: 0,
+  chargeabilityEffect: "COUNT",
+  priority: 0,
+  isActive: true,
+};
+
+export function CalculationRulesClient() {
+  const [editing, setEditing] = useState<EditingRule | null>(null);
+  const [error, setError] = useState<string | null>(null);
+
+  const utils = trpc.useUtils();
+  const { data: rules, isLoading } = trpc.calculationRule.list.useQuery();
+
+  const createMut = trpc.calculationRule.create.useMutation({
+    onSuccess: () => { void utils.calculationRule.list.invalidate(); setEditing(null); },
+    onError: (e) => setError(e.message),
+  });
+  const updateMut = trpc.calculationRule.update.useMutation({
+    onSuccess: () => { void utils.calculationRule.list.invalidate(); setEditing(null); },
+    onError: (e) => setError(e.message),
+  });
+  const deleteMut = trpc.calculationRule.delete.useMutation({
+    onSuccess: () => { void utils.calculationRule.list.invalidate(); },
+    onError: (e) => setError(e.message),
+  });
+
+  function openCreate() {
+    setEditing({ ...emptyRule });
+    setError(null);
+  }
+
+  function openEdit(r: RuleRow) {
+    setEditing({
+      id: r.id,
+      name: r.name,
+      description: r.description ?? "",
+      triggerType: r.triggerType,
+      projectId: r.projectId ?? "",
+      orderType: r.orderType ?? "",
+      costEffect: r.costEffect,
+      costReductionPercent: r.costReductionPercent ?? 0,
+      chargeabilityEffect: r.chargeabilityEffect,
+      priority: r.priority,
+      isActive: r.isActive,
+    });
+    setError(null);
+  }
+
+  function handleSave() {
+    if (!editing) return;
+    setError(null);
+
+    const payload = {
+      name: editing.name,
+      triggerType: editing.triggerType as (typeof TRIGGER_TYPES)[number],
+      costEffect: editing.costEffect as (typeof COST_EFFECTS)[number],
+      chargeabilityEffect: editing.chargeabilityEffect as (typeof CHARGEABILITY_EFFECTS)[number],
+      priority: editing.priority,
+      isActive: editing.isActive,
+      ...(editing.description ? { description: editing.description } : {}),
+      ...(editing.projectId ? { projectId: editing.projectId } : {}),
+      ...(editing.orderType ? { orderType: editing.orderType } : {}),
+      ...(editing.costEffect === "REDUCE" ? { costReductionPercent: editing.costReductionPercent } : {}),
+    };
+
+    if (editing.id) {
+      updateMut.mutate({ id: editing.id, ...payload });
+    } else {
+      createMut.mutate(payload);
+    }
+  }
+
+  if (isLoading) return <div className="p-6 text-sm text-gray-500">Loading...</div>;
+
+  return (
+    <div className="mx-auto max-w-5xl p-6">
+      <div className="mb-6 flex items-center justify-between">
+        <div>
+          <h1 className="text-2xl font-bold text-gray-900 dark:text-gray-100">Calculation Rules</h1>
+          <p className="mt-1 text-sm text-gray-500 dark:text-gray-400">
+            Configure how absences affect project costs and chargeability reporting.
+          </p>
+        </div>
+        <button
+          onClick={openCreate}
+          className="rounded-md bg-blue-600 px-4 py-2 text-sm font-medium text-white hover:bg-blue-700"
+        >
+          Add Rule
+        </button>
+      </div>
+
+      {error && (
+        <div className="mb-4 rounded-md bg-red-50 p-3 text-sm text-red-700 dark:bg-red-900/20 dark:text-red-400">
+          {error}
+        </div>
+      )}
+
+      {/* ── Rules Table ── */}
+      <div className="overflow-x-auto rounded-lg border border-gray-200 dark:border-gray-700">
+        <table className="min-w-full divide-y divide-gray-200 dark:divide-gray-700">
+          <thead className="bg-gray-50 dark:bg-gray-800">
+            <tr>
+              <th className="px-4 py-3 text-left text-xs font-medium uppercase text-gray-500">Name</th>
+              <th className="px-4 py-3 text-left text-xs font-medium uppercase text-gray-500">Trigger</th>
+              <th className="px-4 py-3 text-left text-xs font-medium uppercase text-gray-500">Cost Effect</th>
+              <th className="px-4 py-3 text-left text-xs font-medium uppercase text-gray-500">Chargeability</th>
+              <th className="px-4 py-3 text-left text-xs font-medium uppercase text-gray-500">Scope</th>
+              <th className="px-4 py-3 text-left text-xs font-medium uppercase text-gray-500">Priority</th>
+              <th className="px-4 py-3 text-left text-xs font-medium uppercase text-gray-500">Active</th>
+              <th className="px-4 py-3 text-right text-xs font-medium uppercase text-gray-500">Actions</th>
+            </tr>
+          </thead>
+          <tbody className="divide-y divide-gray-200 bg-white dark:divide-gray-700 dark:bg-gray-900">
+            {(rules ?? []).map((r) => {
+              const rule = r as unknown as RuleRow;
+              return (
+                <tr key={rule.id} className={rule.isActive ? "" : "opacity-50"}>
+                  <td className="px-4 py-3 text-sm font-medium text-gray-900 dark:text-gray-100">{rule.name}</td>
+                  <td className="px-4 py-3 text-sm text-gray-600 dark:text-gray-300">
+                    <span className="rounded bg-gray-100 px-2 py-0.5 text-xs dark:bg-gray-700">
+                      {TRIGGER_LABELS[rule.triggerType] ?? rule.triggerType}
+                    </span>
+                  </td>
+                  <td className="px-4 py-3 text-sm text-gray-600 dark:text-gray-300">
+                    {COST_LABELS[rule.costEffect] ?? rule.costEffect}
+                    {rule.costEffect === "REDUCE" && rule.costReductionPercent != null && (
+                      <span className="ml-1 text-xs text-gray-400">({rule.costReductionPercent}%)</span>
+                    )}
+                  </td>
+                  <td className="px-4 py-3 text-sm text-gray-600 dark:text-gray-300">
+                    {CHG_LABELS[rule.chargeabilityEffect] ?? rule.chargeabilityEffect}
+                  </td>
+                  <td className="px-4 py-3 text-sm text-gray-500 dark:text-gray-400">
+                    {rule.project ? rule.project.shortCode : rule.orderType ? rule.orderType : "Global"}
+                  </td>
+                  <td className="px-4 py-3 text-sm text-gray-500">{rule.priority}</td>
+                  <td className="px-4 py-3 text-sm">
+                    <span className={`inline-block h-2 w-2 rounded-full ${rule.isActive ? "bg-green-500" : "bg-gray-300"}`} />
+                  </td>
+                  <td className="px-4 py-3 text-right text-sm">
+                    <button onClick={() => openEdit(rule)} className="mr-2 text-blue-600 hover:underline dark:text-blue-400">Edit</button>
+                    <button
+                      onClick={() => { if (confirm("Delete this rule?")) deleteMut.mutate({ id: rule.id }); }}
+                      className="text-red-600 hover:underline dark:text-red-400"
+                    >
+                      Delete
+                    </button>
+                  </td>
+                </tr>
+              );
+            })}
+            {(rules ?? []).length === 0 && (
+              <tr>
+                <td colSpan={8} className="px-4 py-8 text-center text-sm text-gray-500">
+                  No calculation rules configured. Add a rule to control how absences affect costs and chargeability.
+                </td>
+              </tr>
+            )}
+          </tbody>
+        </table>
+      </div>
+
+      {/* ── Edit/Create Modal ── */}
+      {editing && (
+        <div className="fixed inset-0 z-50 flex items-center justify-center bg-black/50">
+          <div className="w-full max-w-lg rounded-lg bg-white p-6 shadow-xl dark:bg-gray-800">
+            <h2 className="mb-4 text-lg font-semibold text-gray-900 dark:text-gray-100">
+              {editing.id ? "Edit Rule" : "New Rule"}
+            </h2>
+            <div className="space-y-4">
+              <div>
+                <label className="mb-1 block text-sm font-medium text-gray-700 dark:text-gray-300">Name</label>
+                <input
+                  value={editing.name}
+                  onChange={(e) => setEditing({ ...editing, name: e.target.value })}
+                  className="w-full rounded-md border px-3 py-2 text-sm dark:border-gray-600 dark:bg-gray-700 dark:text-gray-100"
+                />
+              </div>
+              <div>
+                <label className="mb-1 block text-sm font-medium text-gray-700 dark:text-gray-300">Description</label>
+                <textarea
+                  value={editing.description}
+                  onChange={(e) => setEditing({ ...editing, description: e.target.value })}
+                  rows={2}
+                  className="w-full rounded-md border px-3 py-2 text-sm dark:border-gray-600 dark:bg-gray-700 dark:text-gray-100"
+                />
+              </div>
+              <div className="grid grid-cols-2 gap-4">
+                <div>
+                  <label className="mb-1 block text-sm font-medium text-gray-700 dark:text-gray-300">Trigger Type</label>
+                  <select
+                    value={editing.triggerType}
+                    onChange={(e) => setEditing({ ...editing, triggerType: e.target.value })}
+                    className="w-full rounded-md border px-3 py-2 text-sm dark:border-gray-600 dark:bg-gray-700 dark:text-gray-100"
+                  >
+                    {TRIGGER_TYPES.map((t) => <option key={t} value={t}>{TRIGGER_LABELS[t]}</option>)}
+                  </select>
+                </div>
+                <div>
+                  <label className="mb-1 block text-sm font-medium text-gray-700 dark:text-gray-300">Order Type (optional)</label>
+                  <select
+                    value={editing.orderType}
+                    onChange={(e) => setEditing({ ...editing, orderType: e.target.value })}
+                    className="w-full rounded-md border px-3 py-2 text-sm dark:border-gray-600 dark:bg-gray-700 dark:text-gray-100"
+                  >
+                    <option value="">All (Global)</option>
+                    {ORDER_TYPES.map((t) => <option key={t} value={t}>{t}</option>)}
+                  </select>
+                </div>
+              </div>
+              <div className="grid grid-cols-2 gap-4">
+                <div>
+                  <label className="mb-1 block text-sm font-medium text-gray-700 dark:text-gray-300">Cost Effect</label>
+                  <select
+                    value={editing.costEffect}
+                    onChange={(e) => setEditing({ ...editing, costEffect: e.target.value })}
+                    className="w-full rounded-md border px-3 py-2 text-sm dark:border-gray-600 dark:bg-gray-700 dark:text-gray-100"
+                  >
+                    {COST_EFFECTS.map((t) => <option key={t} value={t}>{COST_LABELS[t]}</option>)}
+                  </select>
+                </div>
+                <div>
+                  <label className="mb-1 block text-sm font-medium text-gray-700 dark:text-gray-300">Chargeability</label>
+                  <select
+                    value={editing.chargeabilityEffect}
+                    onChange={(e) => setEditing({ ...editing, chargeabilityEffect: e.target.value })}
+                    className="w-full rounded-md border px-3 py-2 text-sm dark:border-gray-600 dark:bg-gray-700 dark:text-gray-100"
+                  >
+                    {CHARGEABILITY_EFFECTS.map((t) => <option key={t} value={t}>{CHG_LABELS[t]}</option>)}
+                  </select>
+                </div>
+              </div>
+              {editing.costEffect === "REDUCE" && (
+                <div>
+                  <label className="mb-1 block text-sm font-medium text-gray-700 dark:text-gray-300">
+                    Reduction Percent (0-100)
+                  </label>
+                  <input
+                    type="number"
+                    min={0}
+                    max={100}
+                    value={editing.costReductionPercent}
+                    onChange={(e) => setEditing({ ...editing, costReductionPercent: Number(e.target.value) })}
+                    className="w-32 rounded-md border px-3 py-2 text-sm dark:border-gray-600 dark:bg-gray-700 dark:text-gray-100"
+                  />
+                </div>
+              )}
+              <div className="grid grid-cols-2 gap-4">
+                <div>
+                  <label className="mb-1 block text-sm font-medium text-gray-700 dark:text-gray-300">Priority</label>
+                  <input
+                    type="number"
+                    min={0}
+                    value={editing.priority}
+                    onChange={(e) => setEditing({ ...editing, priority: Number(e.target.value) })}
+                    className="w-32 rounded-md border px-3 py-2 text-sm dark:border-gray-600 dark:bg-gray-700 dark:text-gray-100"
+                  />
+                </div>
+                <div className="flex items-end">
+                  <label className="flex items-center gap-2 text-sm text-gray-700 dark:text-gray-300">
+                    <input
+                      type="checkbox"
+                      checked={editing.isActive}
+                      onChange={(e) => setEditing({ ...editing, isActive: e.target.checked })}
+                      className="rounded border-gray-300"
+                    />
+                    Active
+                  </label>
+                </div>
+              </div>
+            </div>
+            <div className="mt-6 flex justify-end gap-3">
+              <button
+                onClick={() => setEditing(null)}
+                className="rounded-md border px-4 py-2 text-sm text-gray-700 hover:bg-gray-50 dark:border-gray-600 dark:text-gray-300 dark:hover:bg-gray-700"
+              >
+                Cancel
+              </button>
+              <button
+                onClick={handleSave}
+                disabled={!editing.name || createMut.isPending || updateMut.isPending}
+                className="rounded-md bg-blue-600 px-4 py-2 text-sm font-medium text-white hover:bg-blue-700 disabled:opacity-50"
+              >
+                {createMut.isPending || updateMut.isPending ? "Saving..." : "Save"}
+              </button>
+            </div>
+          </div>
+        </div>
+      )}
+    </div>
+  );
+}
diff --git a/packages/api/src/router/calculation-rules.ts b/packages/api/src/router/calculation-rules.ts
new file mode 100644
index 0000000..30b4417
--- /dev/null
+++ b/packages/api/src/router/calculation-rules.ts
@@ -0,0 +1,95 @@
+import {
+  CreateCalculationRuleSchema,
+  UpdateCalculationRuleSchema,
+} from "@planarchy/shared";
+import { TRPCError } from "@trpc/server";
+import { z } from "zod";
+import { createTRPCRouter, controllerProcedure, managerProcedure } from "../trpc.js";
+
+export const calculationRuleRouter = createTRPCRouter({
+  list: controllerProcedure.query(async ({ ctx }) => {
+    return ctx.db.calculationRule.findMany({
+      orderBy: [{ priority: "desc" }, { name: "asc" }],
+      include: { project: { select: { id: true, name: true, shortCode: true } } },
+    });
+  }),
+
+  getById: controllerProcedure
+    .input(z.object({ id: z.string() }))
+    .query(async ({ ctx, input }) => {
+      const rule = await ctx.db.calculationRule.findUnique({
+        where: { id: input.id },
+        include: { project: { select: { id: true, name: true, shortCode: true } } },
+      });
+      if (!rule) {
+        throw new TRPCError({ code: "NOT_FOUND", message: "Calculation rule not found" });
+      }
+      return rule;
+    }),
+
+  /** Get all active rules (optimized for engine use — no project include) */
+  getActive: controllerProcedure.query(async ({ ctx }) => {
+    return ctx.db.calculationRule.findMany({
+      where: { isActive: true },
+      orderBy: [{ priority: "desc" }],
+    });
+  }),
+
+  create: managerProcedure
+    .input(CreateCalculationRuleSchema)
+    .mutation(async ({ ctx, input }) => {
+      return ctx.db.calculationRule.create({
+        data: {
+          name: input.name,
+          triggerType: input.triggerType,
+          costEffect: input.costEffect,
+          chargeabilityEffect: input.chargeabilityEffect,
+          ...(input.description !== undefined ? { description: input.description } : {}),
+          ...(input.projectId !== undefined ? { projectId: input.projectId } : {}),
+          ...(input.orderType !== undefined ? { orderType: input.orderType as never } : {}),
+          ...(input.costReductionPercent !== undefined ? { costReductionPercent: input.costReductionPercent } : {}),
+          priority: input.priority,
+          isActive: input.isActive,
+        },
+      });
+    }),
+
+  update: managerProcedure
+    .input(UpdateCalculationRuleSchema)
+    .mutation(async ({ ctx, input }) => {
+      const { id, ...data } = input;
+      const existing = await ctx.db.calculationRule.findUnique({ where: { id } });
+      if (!existing) {
+        throw new TRPCError({ code: "NOT_FOUND", message: "Calculation rule not found" });
+      }
+
+      // Build update data using exactOptionalPropertyTypes pattern
+      const updateData: Record<string, unknown> = {};
+      if (data.name !== undefined) updateData.name = data.name;
+      if (data.description !== undefined) updateData.description = data.description;
+      if (data.triggerType !== undefined) updateData.triggerType = data.triggerType;
+      if (data.projectId !== undefined) updateData.projectId = data.projectId;
+      if (data.orderType !== undefined) updateData.orderType = data.orderType;
+      if (data.costEffect !== undefined) updateData.costEffect = data.costEffect;
+      if (data.costReductionPercent !== undefined) updateData.costReductionPercent = data.costReductionPercent;
+      if (data.chargeabilityEffect !== undefined) updateData.chargeabilityEffect = data.chargeabilityEffect;
+      if (data.priority !== undefined) updateData.priority = data.priority;
+      if (data.isActive !== undefined) updateData.isActive = data.isActive;
+
+      return ctx.db.calculationRule.update({
+        where: { id },
+        data: updateData,
+      });
+    }),
+
+  delete: managerProcedure
+    .input(z.object({ id: z.string() }))
+    .mutation(async ({ ctx, input }) => {
+      const existing = await ctx.db.calculationRule.findUnique({ where: { id: input.id } });
+      if (!existing) {
+        throw new TRPCError({ code: "NOT_FOUND", message: "Calculation rule not found" });
+      }
+      await ctx.db.calculationRule.delete({ where: { id: input.id } });
+      return { success: true };
+    }),
+});
diff --git a/packages/api/src/router/chargeability-report.ts b/packages/api/src/router/chargeability-report.ts
index 652270c..2eb383f 100644
--- a/packages/api/src/router/chargeability-report.ts
+++ b/packages/api/src/router/chargeability-report.ts
@@ -7,8 +7,11 @@ import {
   getMonthKeys,
   countWorkingDaysInOverlap,
   calculateSAH,
+  calculateAllocation,
+  DEFAULT_CALCULATION_RULES,
   type AssignmentSlice,
 } from "@planarchy/engine";
+import type { CalculationRule, AbsenceDay } from "@planarchy/shared";
 import type { SpainScheduleRule } from "@planarchy/shared";
 import { isChargeabilityActualBooking, listAssignmentBookings } from "@planarchy/application";
 import { VacationStatus } from "@planarchy/db";
@@ -115,7 +118,7 @@ export const chargeabilityReportRouter = createTRPCRouter({
           },
         }));
 
-      // Fetch vacations/absences in the range
+      // Fetch vacations/absences in the range (including type for rules engine)
       const vacations = await ctx.db.vacation.findMany({
         where: {
           resourceId: { in: resourceIds },
@@ -127,9 +130,25 @@ export const chargeabilityReportRouter = createTRPCRouter({
           resourceId: true,
           startDate: true,
           endDate: true,
+          type: true,
+          isHalfDay: true,
         },
       });
 
+      // Load calculation rules for chargeability adjustments
+      let calcRules: CalculationRule[] = DEFAULT_CALCULATION_RULES;
+      try {
+        const dbRules = await ctx.db.calculationRule.findMany({
+          where: { isActive: true },
+          orderBy: [{ priority: "desc" }],
+        });
+        if (dbRules.length > 0) {
+          calcRules = dbRules as unknown as CalculationRule[];
+        }
+      } catch {
+        // table may not exist yet
+      }
+
       // Build per-resource, per-month forecasts
       const resourceRows = resources.map((resource) => {
         const resourceAssignments = assignments.filter((a) => a.resourceId === resource.id);
@@ -171,18 +190,65 @@ export const chargeabilityReportRouter = createTRPCRouter({
             absenceDays: absenceDates,
           });
 
-          // Build assignment slices for this month
+          // Build typed absence days for this resource in this month
+          const monthAbsenceDays: AbsenceDay[] = [];
+          for (const v of resourceVacations) {
+            const vStart = new Date(Math.max(v.startDate.getTime(), monthStart.getTime()));
+            const vEnd = new Date(Math.min(v.endDate.getTime(), monthEnd.getTime()));
+            if (vStart > vEnd) continue;
+            const absCursor = new Date(vStart);
+            absCursor.setUTCHours(0, 0, 0, 0);
+            const absEndNorm = new Date(vEnd);
+            absEndNorm.setUTCHours(0, 0, 0, 0);
+            const triggerType = v.type === "SICK" ? "SICK" as const
+              : v.type === "PUBLIC_HOLIDAY" ? "PUBLIC_HOLIDAY" as const
+              : "VACATION" as const;
+            while (absCursor <= absEndNorm) {
+              monthAbsenceDays.push({
+                date: new Date(absCursor),
+                type: triggerType,
+                ...(v.isHalfDay ? { isHalfDay: true } : {}),
+              });
+              absCursor.setUTCDate(absCursor.getUTCDate() + 1);
+            }
+          }
+
+          // Build assignment slices for this month, using rules to compute chargeable hours
           const slices: AssignmentSlice[] = [];
           for (const a of resourceAssignments) {
             const workingDays = countWorkingDaysInOverlap(monthStart, monthEnd, a.startDate, a.endDate);
             if (workingDays <= 0) continue;
 
             const categoryCode = a.project.utilizationCategory?.code ?? "Chg";
-            slices.push({
-              hoursPerDay: a.hoursPerDay,
-              workingDays,
-              categoryCode,
-            });
+
+            // If there are absences and rules, compute rules-adjusted chargeable hours
+            if (monthAbsenceDays.length > 0) {
+              const overlapStart = new Date(Math.max(monthStart.getTime(), a.startDate.getTime()));
+              const overlapEnd = new Date(Math.min(monthEnd.getTime(), a.endDate.getTime()));
+
+              const calcResult = calculateAllocation({
+                lcrCents: 0, // we only need hours, not costs
+                hoursPerDay: a.hoursPerDay,
+                startDate: overlapStart,
+                endDate: overlapEnd,
+                availability: { monday: dailyHours, tuesday: dailyHours, wednesday: dailyHours, thursday: dailyHours, friday: dailyHours, saturday: 0, sunday: 0 },
+                absenceDays: monthAbsenceDays,
+                calculationRules: calcRules,
+              });
+
+              slices.push({
+                hoursPerDay: a.hoursPerDay,
+                workingDays,
+                categoryCode,
+                ...(calcResult.totalChargeableHours !== undefined ? { totalChargeableHours: calcResult.totalChargeableHours } : {}),
+              });
+            } else {
+              slices.push({
+                hoursPerDay: a.hoursPerDay,
+                workingDays,
+                categoryCode,
+              });
+            }
           }
 
           const forecast = deriveResourceForecast({
diff --git a/packages/api/src/router/index.ts b/packages/api/src/router/index.ts
index f7a5631..46faeda 100644
--- a/packages/api/src/router/index.ts
+++ b/packages/api/src/router/index.ts
@@ -1,5 +1,6 @@
 import { createTRPCRouter } from "../trpc.js";
 import { allocationRouter } from "./allocation.js";
+import { calculationRuleRouter } from "./calculation-rules.js";
 import { blueprintRouter } from "./blueprint.js";
 import { chargeabilityReportRouter } from "./chargeability-report.js";
 import { clientRouter } from "./client.js";
@@ -49,6 +50,7 @@ export const appRouter = createTRPCRouter({
   managementLevel: managementLevelRouter,
   rateCard: rateCardRouter,
   chargeabilityReport: chargeabilityReportRouter,
+  calculationRule: calculationRuleRouter,
 });
 
 export type AppRouter = typeof appRouter;
diff --git a/packages/api/src/router/timeline.ts b/packages/api/src/router/timeline.ts
index b9abacb..3c92d35 100644
--- a/packages/api/src/router/timeline.ts
+++ b/packages/api/src/router/timeline.ts
@@ -9,7 +9,9 @@ import {
   updateAllocationEntry,
 } from "@planarchy/application";
 import type { PrismaClient } from "@planarchy/db";
-import { calculateAllocation, computeBudgetStatus, validateShift } from "@planarchy/engine";
+import { calculateAllocation, computeBudgetStatus, validateShift, DEFAULT_CALCULATION_RULES } from "@planarchy/engine";
+import type { CalculationRule, AbsenceDay } from "@planarchy/shared";
+import { VacationType } from "@planarchy/db";
 import { AllocationStatus, PermissionKey, ShiftProjectSchema, UpdateAllocationHoursSchema } from "@planarchy/shared";
 import { TRPCError } from "@trpc/server";
 import { z } from "zod";
@@ -35,7 +37,7 @@ type ShiftDbClient = Pick<
 
 type TimelineEntriesDbClient = Pick<
   PrismaClient,
-  "demandRequirement" | "assignment" | "resource"
+  "demandRequirement" | "assignment" | "resource" | "project"
 >;
 
 type TimelineEntriesFilters = {
@@ -43,6 +45,7 @@ type TimelineEntriesFilters = {
   endDate: Date;
   resourceIds?: string[] | undefined;
   projectIds?: string[] | undefined;
+  clientIds?: string[] | undefined;
   chapters?: string[] | undefined;
   eids?: string[] | undefined;
 };
@@ -63,7 +66,7 @@ async function loadTimelineEntriesReadModel(
   db: TimelineEntriesDbClient,
   input: TimelineEntriesFilters,
 ) {
-  const { startDate, endDate, resourceIds, projectIds, chapters, eids } = input;
+  const { startDate, endDate, resourceIds, projectIds, clientIds, chapters, eids } = input;
 
   // When resource-level filters are active (resourceIds, chapters, or eids),
   // resolve matching resource IDs so we can push the filter to the DB query.
@@ -85,6 +88,23 @@ async function loadTimelineEntriesReadModel(
     return matching.map((r) => r.id);
   })();
 
+  const effectiveProjectIds = await (async () => {
+    if (!clientIds || clientIds.length === 0) return projectIds;
+
+    const matchingProjects = await db.project.findMany({
+      where: { clientId: { in: clientIds } },
+      select: { id: true },
+    });
+    const clientProjectIds = matchingProjects.map((project) => project.id);
+
+    if (!projectIds || projectIds.length === 0) {
+      return clientProjectIds;
+    }
+
+    const allowedIds = new Set(clientProjectIds);
+    return projectIds.filter((projectId) => allowedIds.has(projectId));
+  })();
+
   // When filtering by resource (either explicit resourceIds or derived from chapters),
   // demands without a resource are excluded.
   const excludeDemands = effectiveResourceIds !== undefined;
@@ -97,7 +117,7 @@ async function loadTimelineEntriesReadModel(
             status: { not: "CANCELLED" },
             startDate: { lte: endDate },
             endDate: { gte: startDate },
-            ...(projectIds ? { projectId: { in: projectIds } } : {}),
+            ...(effectiveProjectIds ? { projectId: { in: effectiveProjectIds } } : {}),
           },
           include: PROJECT_PLANNING_DEMAND_INCLUDE,
           orderBy: [{ startDate: "asc" }, { projectId: "asc" }],
@@ -108,7 +128,7 @@ async function loadTimelineEntriesReadModel(
         startDate: { lte: endDate },
         endDate: { gte: startDate },
         ...(effectiveResourceIds ? { resourceId: { in: effectiveResourceIds } } : {}),
-        ...(projectIds ? { projectId: { in: projectIds } } : {}),
+        ...(effectiveProjectIds ? { projectId: { in: effectiveProjectIds } } : {}),
       },
       include: TIMELINE_ASSIGNMENT_INCLUDE,
       orderBy: [{ startDate: "asc" }, { resourceId: "asc" }],
@@ -185,6 +205,74 @@ function anonymizeResourceOnEntry<T extends { resource?: { id: string } | null }
   };
 }
 
+/** Load active calculation rules from DB, falling back to defaults if none configured. */
+async function loadCalculationRules(db: PrismaClient): Promise<CalculationRule[]> {
+  try {
+    const rules = await db.calculationRule.findMany({
+      where: { isActive: true },
+      orderBy: [{ priority: "desc" }],
+    });
+    if (rules.length > 0) {
+      return rules as unknown as CalculationRule[];
+    }
+  } catch {
+    // table may not exist yet
+  }
+  return DEFAULT_CALCULATION_RULES;
+}
+
+/** Build typed absence days from vacations for a resource in a date range. */
+async function buildAbsenceDays(
+  db: PrismaClient,
+  resourceId: string,
+  startDate: Date,
+  endDate: Date,
+): Promise<{ absenceDays: AbsenceDay[]; legacyVacationDates: Date[] }> {
+  const absenceDays: AbsenceDay[] = [];
+  const legacyVacationDates: Date[] = [];
+
+  try {
+    const vacations = await db.vacation.findMany({
+      where: {
+        resourceId,
+        status: "APPROVED",
+        startDate: { lte: endDate },
+        endDate: { gte: startDate },
+      },
+      select: { startDate: true, endDate: true, type: true, isHalfDay: true },
+    });
+
+    for (const v of vacations) {
+      const cur = new Date(v.startDate);
+      cur.setHours(0, 0, 0, 0);
+      const vEnd = new Date(v.endDate);
+      vEnd.setHours(0, 0, 0, 0);
+
+      // Map Prisma VacationType to AbsenceTrigger
+      const triggerType = v.type === VacationType.SICK ? "SICK" as const
+        : v.type === VacationType.PUBLIC_HOLIDAY ? "PUBLIC_HOLIDAY" as const
+        : "VACATION" as const;
+
+      while (cur <= vEnd) {
+        absenceDays.push({
+          date: new Date(cur),
+          type: triggerType,
+          ...(v.isHalfDay ? { isHalfDay: true } : {}),
+        });
+        // Also populate legacy vacation dates for backward compat
+        if (triggerType === "VACATION") {
+          legacyVacationDates.push(new Date(cur));
+        }
+        cur.setDate(cur.getDate() + 1);
+      }
+    }
+  } catch {
+    // vacation table may not exist yet
+  }
+
+  return { absenceDays, legacyVacationDates };
+}
+
 export const timelineRouter = createTRPCRouter({
   /**
    * Get all timeline entries (projects + allocations) for a date range.
@@ -197,6 +285,7 @@ export const timelineRouter = createTRPCRouter({
         endDate: z.coerce.date(),
         resourceIds: z.array(z.string()).optional(),
         projectIds: z.array(z.string()).optional(),
+        clientIds: z.array(z.string()).optional(),
         chapters: z.array(z.string()).optional(),
         eids: z.array(z.string()).optional(),
       }),
@@ -214,6 +303,7 @@ export const timelineRouter = createTRPCRouter({
         endDate: z.coerce.date(),
         resourceIds: z.array(z.string()).optional(),
         projectIds: z.array(z.string()).optional(),
+        clientIds: z.array(z.string()).optional(),
         chapters: z.array(z.string()).optional(),
         eids: z.array(z.string()).optional(),
       }),
@@ -345,31 +435,11 @@ export const timelineRouter = createTRPCRouter({
         // Load recurrence from merged metadata
         const recurrence = (newMeta.recurrence as import("@planarchy/shared").RecurrencePattern | undefined);
 
-        // Load approved vacations for recalculation (graceful fallback if table not yet migrated)
-        const vacationDates: Date[] = [];
-        try {
-          const vacations = await ctx.db.vacation.findMany({
-            where: {
-              resourceId: resolved.resourceId,
-              status: "APPROVED",
-              startDate: { lte: newEndDate },
-              endDate: { gte: newStartDate },
-            },
-            select: { startDate: true, endDate: true },
-          });
-          for (const v of vacations) {
-            const cur = new Date(v.startDate);
-            cur.setHours(0, 0, 0, 0);
-            const vEnd = new Date(v.endDate);
-            vEnd.setHours(0, 0, 0, 0);
-            while (cur <= vEnd) {
-              vacationDates.push(new Date(cur));
-              cur.setDate(cur.getDate() + 1);
-            }
-          }
-        } catch {
-          // vacation table may not exist yet — proceed without vacation adjustment
-        }
+        // Load typed absences + calculation rules for rules-aware cost computation
+        const [absenceData, calculationRules] = await Promise.all([
+          buildAbsenceDays(ctx.db as PrismaClient, resolved.resourceId, newStartDate, newEndDate),
+          loadCalculationRules(ctx.db as PrismaClient),
+        ]);
 
         newDailyCostCents = calculateAllocation({
           lcrCents: existingResource.lcrCents,
@@ -379,7 +449,9 @@ export const timelineRouter = createTRPCRouter({
           availability,
           includeSaturday,
           ...(recurrence ? { recurrence } : {}),
-          vacationDates,
+          vacationDates: absenceData.legacyVacationDates,
+          absenceDays: absenceData.absenceDays,
+          calculationRules,
         }).dailyCostCents;
       }
 
@@ -500,6 +572,9 @@ export const timelineRouter = createTRPCRouter({
         });
       }
 
+      // Pre-load calculation rules for cost recalculation
+      const shiftRules = await loadCalculationRules(ctx.db as PrismaClient);
+
       // Apply shift in a transaction
       const updatedProject = await ctx.db.$transaction(async (tx) => {
         // Update project dates
@@ -523,6 +598,13 @@ export const timelineRouter = createTRPCRouter({
           const metadata = (assignment.metadata as Record<string, unknown> | null | undefined) ?? {};
           const includeSaturday = (metadata.includeSaturday as boolean | undefined) ?? false;
 
+          const shiftAbsenceData = await buildAbsenceDays(
+            ctx.db as PrismaClient,
+            assignment.resourceId!,
+            newStartDate,
+            newEndDate,
+          );
+
           const newDailyCost = calculateAllocation({
             lcrCents: assignment.resource!.lcrCents,
             hoursPerDay: assignment.hoursPerDay,
@@ -531,6 +613,9 @@ export const timelineRouter = createTRPCRouter({
             availability:
               assignment.resource!.availability as unknown as import("@planarchy/shared").WeekdayAvailability,
             includeSaturday,
+            vacationDates: shiftAbsenceData.legacyVacationDates,
+            absenceDays: shiftAbsenceData.absenceDays,
+            calculationRules: shiftRules,
           }).dailyCostCents;
 
           await updateAssignment(
diff --git a/packages/db/prisma/schema.prisma b/packages/db/prisma/schema.prisma
index 5169781..3826977 100644
--- a/packages/db/prisma/schema.prisma
+++ b/packages/db/prisma/schema.prisma
@@ -135,6 +135,24 @@ enum DispoImportSourceKind {
   ROSTER
 }
 
+enum AbsenceTrigger {
+  SICK
+  VACATION
+  PUBLIC_HOLIDAY
+  CUSTOM
+}
+
+enum CostEffect {
+  CHARGE
+  ZERO
+  REDUCE
+}
+
+enum ChargeabilityEffect {
+  COUNT
+  SKIP
+}
+
 enum DispoStagedRecordType {
   RESOURCE
   CLIENT
@@ -805,6 +823,7 @@ model Project {
   demandRequirements DemandRequirement[]
   assignments     Assignment[]
   estimates       Estimate[]
+  calculationRules CalculationRule[]
 
   createdAt       DateTime       @default(now())
   updatedAt       DateTime       @updatedAt
@@ -1315,6 +1334,37 @@ model SystemSettings {
   @@map("system_settings")
 }
 
+// ─── Calculation Rules ────────────────────────────────────────────────────────
+
+model CalculationRule {
+  id                    String               @id @default(cuid())
+  name                  String
+  description           String?
+
+  // ── Matching ──
+  triggerType           AbsenceTrigger
+  projectId             String?
+  orderType             OrderType?
+
+  // ── Effects ──
+  costEffect            CostEffect
+  costReductionPercent  Int?                 // only for REDUCE (0-100)
+  chargeabilityEffect   ChargeabilityEffect
+
+  // ── Ordering ──
+  priority              Int                  @default(0)
+  isActive              Boolean              @default(true)
+
+  project               Project?             @relation(fields: [projectId], references: [id])
+
+  createdAt             DateTime             @default(now())
+  updatedAt             DateTime             @updatedAt
+
+  @@index([triggerType, isActive])
+  @@index([projectId])
+  @@map("calculation_rules")
+}
+
 // ─── Audit Log ────────────────────────────────────────────────────────────────
 
 model AuditLog {
diff --git a/packages/db/src/seed.ts b/packages/db/src/seed.ts
index 8846a1a..4077a54 100644
--- a/packages/db/src/seed.ts
+++ b/packages/db/src/seed.ts
@@ -293,6 +293,7 @@ async function main() {
   await prisma.resourceRole.deleteMany({});
   await prisma.vacation.deleteMany({});
   await prisma.vacationEntitlement.deleteMany({});
+  await prisma.calculationRule.deleteMany({});
   await prisma.project.deleteMany({});
   await prisma.resource.deleteMany({});
   await prisma.role.deleteMany({});
@@ -1215,6 +1216,40 @@ async function main() {
   }
   console.warn(`Vacations: ${vacationCount} created`);
 
+  // ── Calculation Rules (default set) ──────────────────────────────────────────
+  await prisma.calculationRule.createMany({
+    data: [
+      {
+        name: "Urlaub — Person chargeable, Projekt nicht belastet",
+        description: "Vacation days count toward chargeability but are not charged to the project.",
+        triggerType: "VACATION",
+        costEffect: "ZERO",
+        chargeabilityEffect: "COUNT",
+        priority: 0,
+        isActive: true,
+      },
+      {
+        name: "Krankheit — Person chargeable, Projekt nicht belastet",
+        description: "Sick days count toward chargeability but are not charged to the project.",
+        triggerType: "SICK",
+        costEffect: "ZERO",
+        chargeabilityEffect: "COUNT",
+        priority: 0,
+        isActive: true,
+      },
+      {
+        name: "Feiertag — kein Effekt",
+        description: "Public holidays are neither chargeable nor charged to projects.",
+        triggerType: "PUBLIC_HOLIDAY",
+        costEffect: "ZERO",
+        chargeabilityEffect: "SKIP",
+        priority: 0,
+        isActive: true,
+      },
+    ],
+  });
+  console.warn("Calculation rules: 3 default rules created");
+
   console.warn("Seed complete!");
 }
 
diff --git a/packages/engine/src/__tests__/calculator-rules.test.ts b/packages/engine/src/__tests__/calculator-rules.test.ts
new file mode 100644
index 0000000..98aba6f
--- /dev/null
+++ b/packages/engine/src/__tests__/calculator-rules.test.ts
@@ -0,0 +1,243 @@
+import { describe, expect, it } from "vitest";
+import { calculateAllocation } from "../allocation/calculator.js";
+import { DEFAULT_CALCULATION_RULES } from "../rules/default-rules.js";
+import type { WeekdayAvailability, AllocationCalculationInput } from "@planarchy/shared";
+import type { CalculationRule } from "@planarchy/shared";
+
+const STD_AVAILABILITY: WeekdayAvailability = {
+  monday: 8,
+  tuesday: 8,
+  wednesday: 8,
+  thursday: 8,
+  friday: 8,
+  saturday: 0,
+  sunday: 0,
+};
+
+const now = new Date();
+
+function makeRule(overrides: Partial<CalculationRule>): CalculationRule {
+  return {
+    id: "rule_1",
+    name: "Test Rule",
+    description: null,
+    triggerType: "SICK",
+    projectId: null,
+    orderType: null,
+    costEffect: "ZERO",
+    costReductionPercent: null,
+    chargeabilityEffect: "COUNT",
+    priority: 0,
+    isActive: true,
+    createdAt: now,
+    updatedAt: now,
+    ...overrides,
+  };
+}
+
+describe("calculateAllocation with rules", () => {
+  it("backward compatible: no rules = legacy behavior", () => {
+    // Monday 2026-03-02 to Friday 2026-03-06 (5 working days)
+    const result = calculateAllocation({
+      lcrCents: 100,
+      hoursPerDay: 8,
+      startDate: new Date("2026-03-02"),
+      endDate: new Date("2026-03-06"),
+      availability: STD_AVAILABILITY,
+    });
+
+    expect(result.workingDays).toBe(5);
+    expect(result.totalHours).toBe(40);
+    expect(result.totalCostCents).toBe(4000);
+    expect(result.totalChargeableHours).toBeUndefined();
+    expect(result.totalProjectCostCents).toBeUndefined();
+  });
+
+  it("legacy vacation blocks the day without rules", () => {
+    // Monday 2026-03-02 to Friday 2026-03-06, Tuesday is vacation
+    const result = calculateAllocation({
+      lcrCents: 100,
+      hoursPerDay: 8,
+      startDate: new Date("2026-03-02"),
+      endDate: new Date("2026-03-06"),
+      availability: STD_AVAILABILITY,
+      vacationDates: [new Date("2026-03-03")], // Tuesday
+    });
+
+    expect(result.workingDays).toBe(4);
+    expect(result.totalHours).toBe(32);
+    expect(result.totalCostCents).toBe(3200);
+  });
+
+  it("sick day with rules: person chargeable, project not charged", () => {
+    const sickRule = makeRule({
+      triggerType: "SICK",
+      costEffect: "ZERO",
+      chargeabilityEffect: "COUNT",
+    });
+
+    // Monday 2026-03-02 to Friday 2026-03-06, Wednesday is sick
+    const result = calculateAllocation({
+      lcrCents: 100,
+      hoursPerDay: 8,
+      startDate: new Date("2026-03-02"),
+      endDate: new Date("2026-03-06"),
+      availability: STD_AVAILABILITY,
+      absenceDays: [{ date: new Date("2026-03-04"), type: "SICK" }],
+      calculationRules: [sickRule],
+    });
+
+    // Person worked 4 days (sick day hours = 0 effective)
+    expect(result.workingDays).toBe(5); // still counted as working day
+    expect(result.totalHours).toBe(32); // 4 days x 8h (sick day effective = 0)
+
+    // Project cost: 4 days x 800 = 3200 (sick day = ZERO cost to project)
+    expect(result.totalProjectCostCents).toBe(3200);
+
+    // Chargeability: all 5 days count (8h x 5 = 40h)
+    expect(result.totalChargeableHours).toBe(40);
+
+    // Check the sick day breakdown entry (index 2 = Wednesday = 3rd day)
+    const sickDay = result.dailyBreakdown[2]!;
+    expect(sickDay.absenceType).toBe("SICK");
+    expect(sickDay.hours).toBe(0); // not worked
+    expect(sickDay.costCents).toBe(0); // not charged to project
+    expect(sickDay.chargeableHours).toBe(8); // counts toward chargeability
+  });
+
+  it("vacation with rules: person chargeable, project not charged", () => {
+    const vacationRule = makeRule({
+      triggerType: "VACATION",
+      costEffect: "ZERO",
+      chargeabilityEffect: "COUNT",
+    });
+
+    // Mon-Fri, Tuesday is vacation via absenceDays
+    const result = calculateAllocation({
+      lcrCents: 150,
+      hoursPerDay: 8,
+      startDate: new Date("2026-03-02"),
+      endDate: new Date("2026-03-06"),
+      availability: STD_AVAILABILITY,
+      absenceDays: [{ date: new Date("2026-03-03"), type: "VACATION" }],
+      calculationRules: [vacationRule],
+    });
+
+    expect(result.totalHours).toBe(32);
+    expect(result.totalProjectCostCents).toBe(4800); // 4 x 8 x 150
+    expect(result.totalChargeableHours).toBe(40); // all 5 days
+  });
+
+  it("vacation via legacy vacationDates + rules", () => {
+    const vacationRule = makeRule({
+      triggerType: "VACATION",
+      costEffect: "ZERO",
+      chargeabilityEffect: "COUNT",
+    });
+
+    const result = calculateAllocation({
+      lcrCents: 100,
+      hoursPerDay: 8,
+      startDate: new Date("2026-03-02"),
+      endDate: new Date("2026-03-06"),
+      availability: STD_AVAILABILITY,
+      vacationDates: [new Date("2026-03-03")],
+      calculationRules: [vacationRule],
+    });
+
+    expect(result.totalHours).toBe(32);
+    expect(result.totalProjectCostCents).toBe(3200);
+    expect(result.totalChargeableHours).toBe(40);
+  });
+
+  it("public holiday with rules: not chargeable, not charged", () => {
+    const holidayRule = makeRule({
+      triggerType: "PUBLIC_HOLIDAY",
+      costEffect: "ZERO",
+      chargeabilityEffect: "SKIP",
+    });
+
+    const result = calculateAllocation({
+      lcrCents: 100,
+      hoursPerDay: 8,
+      startDate: new Date("2026-03-02"),
+      endDate: new Date("2026-03-06"),
+      availability: STD_AVAILABILITY,
+      absenceDays: [{ date: new Date("2026-03-04"), type: "PUBLIC_HOLIDAY" }],
+      calculationRules: [holidayRule],
+    });
+
+    expect(result.totalHours).toBe(32);
+    expect(result.totalProjectCostCents).toBe(3200);
+    // Public holiday SKIP → chargeableHours = 0 for that day
+    expect(result.totalChargeableHours).toBe(32);
+  });
+
+  it("REDUCE cost effect applies percentage", () => {
+    const rule = makeRule({
+      triggerType: "SICK",
+      costEffect: "REDUCE",
+      costReductionPercent: 50,
+      chargeabilityEffect: "COUNT",
+    });
+
+    const result = calculateAllocation({
+      lcrCents: 100,
+      hoursPerDay: 8,
+      startDate: new Date("2026-03-02"),
+      endDate: new Date("2026-03-06"),
+      availability: STD_AVAILABILITY,
+      absenceDays: [{ date: new Date("2026-03-04"), type: "SICK" }],
+      calculationRules: [rule],
+    });
+
+    // Sick day: 8h x 100 cents = 800 reduced by 50% = 400
+    // Other 4 days: 4 x 800 = 3200
+    expect(result.totalProjectCostCents).toBe(3600);
+    expect(result.totalChargeableHours).toBe(40);
+  });
+
+  it("half-day sick: partial effect", () => {
+    const sickRule = makeRule({
+      triggerType: "SICK",
+      costEffect: "ZERO",
+      chargeabilityEffect: "COUNT",
+    });
+
+    const result = calculateAllocation({
+      lcrCents: 100,
+      hoursPerDay: 8,
+      startDate: new Date("2026-03-04"), // single Wednesday
+      endDate: new Date("2026-03-04"),
+      availability: STD_AVAILABILITY,
+      absenceDays: [{ date: new Date("2026-03-04"), type: "SICK", isHalfDay: true }],
+      calculationRules: [sickRule],
+    });
+
+    // Half day sick: 4h worked, 4h absent
+    expect(result.totalHours).toBe(4); // worked portion
+    expect(result.totalProjectCostCents).toBe(400); // only worked portion charged
+    expect(result.totalChargeableHours).toBe(8); // full day counts (COUNT rule)
+  });
+
+  it("uses default rules when provided", () => {
+    const result = calculateAllocation({
+      lcrCents: 100,
+      hoursPerDay: 8,
+      startDate: new Date("2026-03-02"),
+      endDate: new Date("2026-03-06"),
+      availability: STD_AVAILABILITY,
+      absenceDays: [
+        { date: new Date("2026-03-03"), type: "SICK" },
+        { date: new Date("2026-03-05"), type: "VACATION" },
+      ],
+      calculationRules: DEFAULT_CALCULATION_RULES,
+    });
+
+    // 3 normal days + 2 absent days (counted as working)
+    expect(result.workingDays).toBe(5);
+    expect(result.totalHours).toBe(24); // only 3 days actually worked
+    expect(result.totalProjectCostCents).toBe(2400); // only 3 days charged
+    expect(result.totalChargeableHours).toBe(40); // all 5 days chargeable
+  });
+});
diff --git a/packages/engine/src/__tests__/rules-engine.test.ts b/packages/engine/src/__tests__/rules-engine.test.ts
new file mode 100644
index 0000000..7c62fcc
--- /dev/null
+++ b/packages/engine/src/__tests__/rules-engine.test.ts
@@ -0,0 +1,148 @@
+import { describe, expect, it } from "vitest";
+import { findMatchingRule, applyCostEffect } from "../rules/engine.js";
+import { DEFAULT_CALCULATION_RULES } from "../rules/default-rules.js";
+import type { CalculationRule } from "@planarchy/shared";
+
+const now = new Date();
+
+function makeRule(overrides: Partial<CalculationRule>): CalculationRule {
+  return {
+    id: "rule_1",
+    name: "Test Rule",
+    description: null,
+    triggerType: "SICK",
+    projectId: null,
+    orderType: null,
+    costEffect: "ZERO",
+    costReductionPercent: null,
+    chargeabilityEffect: "COUNT",
+    priority: 0,
+    isActive: true,
+    createdAt: now,
+    updatedAt: now,
+    ...overrides,
+  };
+}
+
+describe("findMatchingRule", () => {
+  it("matches by triggerType", () => {
+    const rules = [makeRule({ triggerType: "SICK" })];
+    const match = findMatchingRule(rules, "SICK");
+    expect(match).not.toBeNull();
+    expect(match!.costEffect).toBe("ZERO");
+  });
+
+  it("returns null when no rules match", () => {
+    const rules = [makeRule({ triggerType: "SICK" })];
+    const match = findMatchingRule(rules, "VACATION");
+    expect(match).toBeNull();
+  });
+
+  it("skips inactive rules", () => {
+    const rules = [makeRule({ triggerType: "SICK", isActive: false })];
+    const match = findMatchingRule(rules, "SICK");
+    expect(match).toBeNull();
+  });
+
+  it("prefers more specific rules (projectId match)", () => {
+    const global = makeRule({ id: "global", triggerType: "SICK", projectId: null });
+    const specific = makeRule({ id: "specific", triggerType: "SICK", projectId: "proj_1", costEffect: "CHARGE" });
+    const match = findMatchingRule([global, specific], "SICK", "proj_1");
+    expect(match!.rule.id).toBe("specific");
+    expect(match!.costEffect).toBe("CHARGE");
+  });
+
+  it("does not match project-specific rule to wrong project", () => {
+    const specific = makeRule({ triggerType: "SICK", projectId: "proj_1" });
+    const match = findMatchingRule([specific], "SICK", "proj_2");
+    expect(match).toBeNull();
+  });
+
+  it("prefers higher specificity over higher priority", () => {
+    const highPriority = makeRule({ id: "hp", triggerType: "SICK", priority: 100 });
+    const specific = makeRule({ id: "sp", triggerType: "SICK", projectId: "proj_1", priority: 0 });
+    const match = findMatchingRule([highPriority, specific], "SICK", "proj_1");
+    expect(match!.rule.id).toBe("sp");
+  });
+
+  it("breaks specificity ties with priority", () => {
+    const lowP = makeRule({ id: "low", triggerType: "SICK", priority: 5 });
+    const highP = makeRule({ id: "high", triggerType: "SICK", priority: 10 });
+    const match = findMatchingRule([lowP, highP], "SICK");
+    expect(match!.rule.id).toBe("high");
+  });
+
+  it("matches orderType filter", () => {
+    const rule = makeRule({ triggerType: "VACATION", orderType: "CHARGEABLE" as never, costEffect: "REDUCE", costReductionPercent: 50 });
+    const match = findMatchingRule([rule], "VACATION", null, "CHARGEABLE");
+    expect(match).not.toBeNull();
+    expect(match!.costEffect).toBe("REDUCE");
+  });
+
+  it("does not match wrong orderType", () => {
+    const rule = makeRule({ triggerType: "VACATION", orderType: "CHARGEABLE" as never });
+    const match = findMatchingRule([rule], "VACATION", null, "INTERNAL");
+    expect(match).toBeNull();
+  });
+
+  it("specificity: projectId + orderType > projectId only", () => {
+    const projOnly = makeRule({ id: "proj", triggerType: "SICK", projectId: "p1" });
+    const both = makeRule({ id: "both", triggerType: "SICK", projectId: "p1", orderType: "CHARGEABLE" as never, costEffect: "REDUCE" });
+    const match = findMatchingRule([projOnly, both], "SICK", "p1", "CHARGEABLE");
+    expect(match!.rule.id).toBe("both");
+  });
+});
+
+describe("applyCostEffect", () => {
+  it("CHARGE returns full cost", () => {
+    expect(applyCostEffect(1000, "CHARGE", null)).toBe(1000);
+  });
+
+  it("ZERO returns 0", () => {
+    expect(applyCostEffect(1000, "ZERO", null)).toBe(0);
+  });
+
+  it("REDUCE applies percentage", () => {
+    expect(applyCostEffect(1000, "REDUCE", 30)).toBe(700);
+  });
+
+  it("REDUCE with 100% returns 0", () => {
+    expect(applyCostEffect(1000, "REDUCE", 100)).toBe(0);
+  });
+
+  it("REDUCE with 0% returns full cost", () => {
+    expect(applyCostEffect(1000, "REDUCE", 0)).toBe(1000);
+  });
+
+  it("REDUCE with null percent returns full cost", () => {
+    expect(applyCostEffect(1000, "REDUCE", null)).toBe(1000);
+  });
+});
+
+describe("DEFAULT_CALCULATION_RULES", () => {
+  it("provides vacation, sick, and public holiday rules", () => {
+    expect(DEFAULT_CALCULATION_RULES).toHaveLength(3);
+    const triggers = DEFAULT_CALCULATION_RULES.map((r) => r.triggerType);
+    expect(triggers).toContain("VACATION");
+    expect(triggers).toContain("SICK");
+    expect(triggers).toContain("PUBLIC_HOLIDAY");
+  });
+
+  it("vacation: zero cost, count chargeability", () => {
+    const rule = DEFAULT_CALCULATION_RULES.find((r) => r.triggerType === "VACATION")!;
+    expect(rule.costEffect).toBe("ZERO");
+    expect(rule.chargeabilityEffect).toBe("COUNT");
+  });
+
+  it("sick: zero cost, count chargeability", () => {
+    const rule = DEFAULT_CALCULATION_RULES.find((r) => r.triggerType === "SICK")!;
+    expect(rule.costEffect).toBe("ZERO");
+    expect(rule.chargeabilityEffect).toBe("COUNT");
+  });
+
+  it("public holiday: zero cost, skip chargeability", () => {
+    const rule = DEFAULT_CALCULATION_RULES.find((r) => r.triggerType === "PUBLIC_HOLIDAY")!;
+    expect(rule.costEffect).toBe("ZERO");
+    expect(rule.chargeabilityEffect).toBe("SKIP");
+  });
+});
diff --git a/packages/engine/src/allocation/calculator.ts b/packages/engine/src/allocation/calculator.ts
index 5be4321..7b39408 100644
--- a/packages/engine/src/allocation/calculator.ts
+++ b/packages/engine/src/allocation/calculator.ts
@@ -1,10 +1,13 @@
 import type {
+  AbsenceDay,
   AllocationCalculationInput,
   AllocationCalculationResult,
   DailyBreakdown,
   WeekdayAvailability,
 } from "@planarchy/shared";
+import type { AbsenceTrigger } from "@planarchy/shared";
 import { getRecurringHoursForDay } from "./recurrence.js";
+import { findMatchingRule, applyCostEffect } from "../rules/engine.js";
 
 /** Day-of-week index → availability key */
 const DOW_KEYS: (keyof WeekdayAvailability)[] = [
@@ -64,10 +67,16 @@ export function countWorkingDays(
  * Core allocation calculator: given hours/day, LCR, and date range,
  * computes total hours, total cost, and daily breakdown.
  *
+ * When calculationRules + absenceDays are provided, the rules engine
+ * determines per-day cost attribution and chargeability effects.
+ *
  * Monetary values always in integer cents.
  */
 export function calculateAllocation(input: AllocationCalculationInput): AllocationCalculationResult {
-  const { lcrCents, hoursPerDay, startDate, endDate, availability, includeSaturday, recurrence, vacationDates } = input;
+  const {
+    lcrCents, hoursPerDay, startDate, endDate, availability, includeSaturday,
+    recurrence, vacationDates, absenceDays, calculationRules, orderType, projectId,
+  } = input;
 
   // When includeSaturday is not explicitly true, zero out saturday availability
   const effectiveAvailability: WeekdayAvailability = includeSaturday
@@ -83,6 +92,16 @@ export function calculateAllocation(input: AllocationCalculationInput): Allocati
     }),
   );
 
+  // Pre-compute typed absence day lookup (date key → AbsenceDay)
+  const absenceDayMap = new Map<string, AbsenceDay>();
+  for (const ad of absenceDays ?? []) {
+    const copy = new Date(ad.date);
+    copy.setHours(0, 0, 0, 0);
+    absenceDayMap.set(copy.toISOString().split("T")[0]!, ad);
+  }
+
+  const hasRules = calculationRules && calculationRules.length > 0;
+
   const allocationStart = new Date(startDate);
   allocationStart.setHours(0, 0, 0, 0);
 
@@ -94,49 +113,120 @@ export function calculateAllocation(input: AllocationCalculationInput): Allocati
 
   let workingDays = 0;
   let totalHours = 0;
+  let totalChargeableHours = 0;
+  let totalProjectCostCents = 0;
 
   while (current <= end) {
     const dateKey = current.toISOString().split("T")[0]!;
     const isVacation = vacationDateSet.has(dateKey);
+    const absenceDay = absenceDayMap.get(dateKey);
 
     let effectiveHours: number;
     let dayIsWorkday: boolean;
+    let absenceType: AbsenceTrigger | undefined;
+    let chargeableHours: number | undefined;
+    let projectCostCents: number;
 
-    if (isVacation) {
-      // Vacation always blocks the day
+    // Determine if this is an absence day (from typed absenceDays or legacy vacationDates)
+    const isAbsent = isVacation || !!absenceDay;
+    if (absenceDay) {
+      absenceType = absenceDay.type;
+    } else if (isVacation) {
+      absenceType = "VACATION";
+    }
+
+    if (isAbsent && hasRules && absenceType) {
+      // ── Rules-based absence handling ──
+      const availableHours = getAvailableHoursForDate(current, effectiveAvailability);
+      dayIsWorkday = availableHours > 0;
+
+      if (!dayIsWorkday) {
+        // Weekend/non-working day — no effect regardless of absence
+        effectiveHours = 0;
+        chargeableHours = 0;
+        projectCostCents = 0;
+      } else {
+        const normalHours = Math.min(hoursPerDay, availableHours);
+        const halfDayFactor = absenceDay?.isHalfDay ? 0.5 : 1;
+        const absentHours = normalHours * halfDayFactor;
+        const workedHours = normalHours - absentHours;
+
+        // The person does NOT work the absent portion
+        effectiveHours = workedHours;
+
+        const match = findMatchingRule(calculationRules!, absenceType, projectId, orderType);
+        if (match) {
+          // Cost effect: how much does the project pay?
+          const normalCostCents = Math.round(absentHours * lcrCents);
+          const absentProjectCost = applyCostEffect(normalCostCents, match.costEffect, match.costReductionPercent);
+          const workedCostCents = Math.round(workedHours * lcrCents);
+          projectCostCents = workedCostCents + absentProjectCost;
+
+          // Chargeability effect: does the person count as chargeable?
+          if (match.chargeabilityEffect === "COUNT") {
+            chargeableHours = normalHours; // full hours count toward chargeability
+          } else {
+            chargeableHours = workedHours; // only worked portion counts
+          }
+        } else {
+          // No matching rule — legacy behavior: block absent hours
+          effectiveHours = workedHours;
+          projectCostCents = Math.round(workedHours * lcrCents);
+          chargeableHours = workedHours;
+        }
+
+        workingDays++;
+        totalHours += effectiveHours;
+      }
+    } else if (isVacation && !hasRules) {
+      // ── Legacy behavior: vacation blocks the day entirely ──
       effectiveHours = 0;
       dayIsWorkday = false;
+      projectCostCents = 0;
     } else if (recurrence) {
       // Recurrence pattern — may override hoursPerDay or skip the day entirely
       const recurHours = getRecurringHoursForDay(current, recurrence, hoursPerDay, allocationStart);
       if (recurHours === 0) {
         effectiveHours = 0;
         dayIsWorkday = false;
+        projectCostCents = 0;
       } else {
         const availableHours = getAvailableHoursForDate(current, effectiveAvailability);
         dayIsWorkday = availableHours > 0;
         effectiveHours = dayIsWorkday ? Math.min(recurHours, availableHours) : 0;
+        projectCostCents = Math.round(effectiveHours * lcrCents);
+      }
+
+      if (dayIsWorkday) {
+        workingDays++;
+        totalHours += effectiveHours;
       }
     } else {
       const availableHours = getAvailableHoursForDate(current, effectiveAvailability);
       dayIsWorkday = availableHours > 0;
       effectiveHours = dayIsWorkday ? Math.min(hoursPerDay, availableHours) : 0;
+      projectCostCents = Math.round(effectiveHours * lcrCents);
+
+      if (dayIsWorkday) {
+        workingDays++;
+        totalHours += effectiveHours;
+      }
     }
 
-    // Cost = hours × lcrCents (already in cents-per-hour)
-    const dayCostCents = Math.round(effectiveHours * lcrCents);
+    // costCents on DailyBreakdown = project cost (rule-adjusted)
+    const dayCostCents = projectCostCents;
 
     breakdown.push({
       date: new Date(current),
       isWorkday: dayIsWorkday,
       hours: effectiveHours,
       costCents: dayCostCents,
+      ...(absenceType ? { absenceType } : {}),
+      ...(chargeableHours !== undefined ? { chargeableHours } : {}),
     });
 
-    if (dayIsWorkday) {
-      workingDays++;
-      totalHours += effectiveHours;
-    }
+    totalChargeableHours += chargeableHours ?? effectiveHours;
+    totalProjectCostCents += dayCostCents;
 
     current.setDate(current.getDate() + 1);
   }
@@ -150,6 +240,7 @@ export function calculateAllocation(input: AllocationCalculationInput): Allocati
     totalCostCents,
     dailyCostCents,
     dailyBreakdown: breakdown,
+    ...(hasRules ? { totalChargeableHours, totalProjectCostCents } : {}),
   };
 }
 
diff --git a/packages/engine/src/budget/monitor.ts b/packages/engine/src/budget/monitor.ts
index eb90a95..6e19c94 100644
--- a/packages/engine/src/budget/monitor.ts
+++ b/packages/engine/src/budget/monitor.ts
@@ -8,7 +8,10 @@ import { BUDGET_WARNING_THRESHOLDS } from "@planarchy/shared";
 export function computeBudgetStatus(
   budgetCents: number,
   winProbability: number,
-  allocations: Pick<Allocation, "status" | "dailyCostCents" | "startDate" | "endDate" | "hoursPerDay">[],
+  allocations: (Pick<Allocation, "status" | "dailyCostCents" | "startDate" | "endDate" | "hoursPerDay"> & {
+    /** When provided (from rules engine), used instead of dailyCostCents * days */
+    adjustedTotalCostCents?: number;
+  })[],
   projectStartDate: Date,
   projectEndDate: Date,
 ): BudgetStatus {
@@ -19,11 +22,10 @@ export function computeBudgetStatus(
   let proposedCents = 0;
 
   for (const alloc of allocations) {
-    const days = countWorkingDaysInRange(
+    const totalCents = alloc.adjustedTotalCostCents ?? (alloc.dailyCostCents * countWorkingDaysInRange(
       new Date(alloc.startDate),
       new Date(alloc.endDate),
-    );
-    const totalCents = alloc.dailyCostCents * days;
+    ));
 
     if (activeStatuses.has(alloc.status)) {
       confirmedCents += totalCents;
diff --git a/packages/engine/src/chargeability/calculator.ts b/packages/engine/src/chargeability/calculator.ts
index 8b502ef..809ba65 100644
--- a/packages/engine/src/chargeability/calculator.ts
+++ b/packages/engine/src/chargeability/calculator.ts
@@ -23,6 +23,9 @@ export interface AssignmentSlice {
   workingDays: number;
   /** Utilization category code (e.g. "Chg", "BD", "MD&I", "M&O", "PD&R"). */
   categoryCode: string;
+  /** Override total hours for this slice (e.g. when rules adjust chargeable hours).
+   *  When set, used instead of hoursPerDay * workingDays. */
+  totalChargeableHours?: number;
 }
 
 export interface ResourceForecast {
@@ -58,10 +61,10 @@ export function deriveResourceForecast(input: ResourceForecastInput): ResourceFo
     return { chg: 0, bd: 0, mdi: 0, mo: 0, pdr: 0, absence: 0, unassigned: 1 };
   }
 
-  // Sum hours per category
+  // Sum hours per category (use totalChargeableHours when available for rules-adjusted values)
   const categoryHours: Record<string, number> = {};
   for (const a of assignments) {
-    const hours = a.hoursPerDay * a.workingDays;
+    const hours = a.totalChargeableHours ?? (a.hoursPerDay * a.workingDays);
     const key = a.categoryCode.toLowerCase();
     categoryHours[key] = (categoryHours[key] ?? 0) + hours;
   }
diff --git a/packages/engine/src/index.ts b/packages/engine/src/index.ts
index 27a47ca..0bee60c 100644
--- a/packages/engine/src/index.ts
+++ b/packages/engine/src/index.ts
@@ -6,3 +6,4 @@ export * from "./shift/index.js";
 export * from "./vacation/utils.js";
 export * from "./sah/index.js";
 export * from "./chargeability/index.js";
+export * from "./rules/index.js";
diff --git a/packages/engine/src/rules/default-rules.ts b/packages/engine/src/rules/default-rules.ts
new file mode 100644
index 0000000..5e29a16
--- /dev/null
+++ b/packages/engine/src/rules/default-rules.ts
@@ -0,0 +1,60 @@
+/**
+ * Default calculation rules — used as fallback when no DB rules are configured.
+ *
+ * These encode the business defaults:
+ * - Vacation: person is chargeable, project is NOT charged
+ * - Sick: person is chargeable, project is NOT charged
+ * - Public holiday: no chargeability effect, no project cost
+ */
+
+import type { CalculationRule } from "@planarchy/shared";
+
+const now = new Date();
+
+export const DEFAULT_CALCULATION_RULES: CalculationRule[] = [
+  {
+    id: "default_vacation",
+    name: "Urlaub — Person chargeable, Projekt nicht belastet",
+    description: "Vacation days count toward chargeability but are not charged to the project.",
+    triggerType: "VACATION",
+    projectId: null,
+    orderType: null,
+    costEffect: "ZERO",
+    costReductionPercent: null,
+    chargeabilityEffect: "COUNT",
+    priority: 0,
+    isActive: true,
+    createdAt: now,
+    updatedAt: now,
+  },
+  {
+    id: "default_sick",
+    name: "Krankheit — Person chargeable, Projekt nicht belastet",
+    description: "Sick days count toward chargeability but are not charged to the project.",
+    triggerType: "SICK",
+    projectId: null,
+    orderType: null,
+    costEffect: "ZERO",
+    costReductionPercent: null,
+    chargeabilityEffect: "COUNT",
+    priority: 0,
+    isActive: true,
+    createdAt: now,
+    updatedAt: now,
+  },
+  {
+    id: "default_public_holiday",
+    name: "Feiertag — kein Effekt",
+    description: "Public holidays are neither chargeable nor charged to projects.",
+    triggerType: "PUBLIC_HOLIDAY",
+    projectId: null,
+    orderType: null,
+    costEffect: "ZERO",
+    costReductionPercent: null,
+    chargeabilityEffect: "SKIP",
+    priority: 0,
+    isActive: true,
+    createdAt: now,
+    updatedAt: now,
+  },
+];
diff --git a/packages/engine/src/rules/engine.ts b/packages/engine/src/rules/engine.ts
new file mode 100644
index 0000000..d97f109
--- /dev/null
+++ b/packages/engine/src/rules/engine.ts
@@ -0,0 +1,91 @@
+/**
+ * Calculation Rules Engine — matches absence days against rules
+ * to determine cost and chargeability effects.
+ *
+ * Pure function — no DB imports.
+ */
+
+import type {
+  AbsenceTrigger,
+  CalculationRule,
+  CostEffect,
+  ChargeabilityEffect,
+} from "@planarchy/shared";
+
+export interface RuleMatch {
+  rule: CalculationRule;
+  costEffect: CostEffect;
+  chargeabilityEffect: ChargeabilityEffect;
+  costReductionPercent: number | null;
+}
+
+/**
+ * Specificity score for a rule — more specific filters = higher score.
+ */
+function specificityScore(rule: CalculationRule): number {
+  let score = 0;
+  if (rule.projectId) score += 2;
+  if (rule.orderType) score += 1;
+  return score;
+}
+
+/**
+ * Find the best matching rule for a given absence day.
+ *
+ * Matching:
+ * 1. triggerType must match
+ * 2. isActive must be true
+ * 3. projectId must match (null = all projects)
+ * 4. orderType must match (null = all order types)
+ *
+ * Ranking: highest specificity wins, then highest priority.
+ */
+export function findMatchingRule(
+  rules: CalculationRule[],
+  triggerType: AbsenceTrigger,
+  projectId?: string | null,
+  orderType?: string | null,
+): RuleMatch | null {
+  const candidates = rules.filter((r) => {
+    if (!r.isActive) return false;
+    if (r.triggerType !== triggerType) return false;
+    if (r.projectId && r.projectId !== projectId) return false;
+    if (r.orderType && r.orderType !== orderType) return false;
+    return true;
+  });
+
+  if (candidates.length === 0) return null;
+
+  // Sort by specificity (desc), then priority (desc)
+  candidates.sort((a, b) => {
+    const specDiff = specificityScore(b) - specificityScore(a);
+    if (specDiff !== 0) return specDiff;
+    return b.priority - a.priority;
+  });
+
+  const best = candidates[0]!;
+  return {
+    rule: best,
+    costEffect: best.costEffect,
+    chargeabilityEffect: best.chargeabilityEffect,
+    costReductionPercent: best.costReductionPercent,
+  };
+}
+
+/**
+ * Apply cost effect to a cost value.
+ */
+export function applyCostEffect(
+  normalCostCents: number,
+  costEffect: CostEffect,
+  reductionPercent: number | null,
+): number {
+  switch (costEffect) {
+    case "CHARGE":
+      return normalCostCents;
+    case "ZERO":
+      return 0;
+    case "REDUCE":
+      return Math.round(normalCostCents * (100 - (reductionPercent ?? 0)) / 100);
+  }
+}
diff --git a/packages/engine/src/rules/index.ts b/packages/engine/src/rules/index.ts
new file mode 100644
index 0000000..3a83af6
--- /dev/null
+++ b/packages/engine/src/rules/index.ts
@@ -0,0 +1,3 @@
+export { findMatchingRule, applyCostEffect } from "./engine.js";
+export type { RuleMatch } from "./engine.js";
+export { DEFAULT_CALCULATION_RULES } from "./default-rules.js";
diff --git a/packages/shared/src/schemas/calculation-rules.schema.ts b/packages/shared/src/schemas/calculation-rules.schema.ts
new file mode 100644
index 0000000..a28b935
--- /dev/null
+++ b/packages/shared/src/schemas/calculation-rules.schema.ts
@@ -0,0 +1,22 @@
+import { z } from "zod";
+
+export const AbsenceTriggerEnum = z.enum(["SICK", "VACATION", "PUBLIC_HOLIDAY", "CUSTOM"]);
+export const CostEffectEnum = z.enum(["CHARGE", "ZERO", "REDUCE"]);
+export const ChargeabilityEffectEnum = z.enum(["COUNT", "SKIP"]);
+
+export const CreateCalculationRuleSchema = z.object({
+  name: z.string().min(1).max(200),
+  description: z.string().max(1000).optional(),
+  triggerType: AbsenceTriggerEnum,
+  projectId: z.string().optional(),
+  orderType: z.string().optional(),
+  costEffect: CostEffectEnum,
+  costReductionPercent: z.number().int().min(0).max(100).optional(),
+  chargeabilityEffect: ChargeabilityEffectEnum,
+  priority: z.number().int().min(0).max(1000).default(0),
+  isActive: z.boolean().default(true),
+});
+
+export const UpdateCalculationRuleSchema = CreateCalculationRuleSchema.partial().extend({
+  id: z.string(),
+});
diff --git a/packages/shared/src/schemas/index.ts b/packages/shared/src/schemas/index.ts
index ef2813c..1064af0 100644
--- a/packages/shared/src/schemas/index.ts
+++ b/packages/shared/src/schemas/index.ts
@@ -13,3 +13,4 @@ export * from "./client.schema.js";
 export * from "./management-level.schema.js";
 export * from "./rate-card.schema.js";
 export * from "./dispo-import.schema.js";
+export * from "./calculation-rules.schema.js";
diff --git a/packages/shared/src/types/calculation-rules.ts b/packages/shared/src/types/calculation-rules.ts
new file mode 100644
index 0000000..767563c
--- /dev/null
+++ b/packages/shared/src/types/calculation-rules.ts
@@ -0,0 +1,32 @@
+// ─── Calculation Rules ────────────────────────────────────────────────────────
+// Admin-configurable rules that decouple cost attribution from chargeability.
+// Example: "Sick person = still chargeable, but NOT charged to project."
+
+export type AbsenceTrigger = "SICK" | "VACATION" | "PUBLIC_HOLIDAY" | "CUSTOM";
+
+export type CostEffect = "CHARGE" | "ZERO" | "REDUCE";
+
+export type ChargeabilityEffect = "COUNT" | "SKIP";
+
+export interface CalculationRule {
+  id: string;
+  name: string;
+  description: string | null;
+
+  // ── Matching ──
+  triggerType: AbsenceTrigger;
+  projectId: string | null;     // null = all projects
+  orderType: string | null;     // null = all order types
+
+  // ── Effects ──
+  costEffect: CostEffect;
+  costReductionPercent: number | null; // only for REDUCE (0-100)
+  chargeabilityEffect: ChargeabilityEffect;
+
+  // ── Ordering ──
+  priority: number;
+  isActive: boolean;
+
+  createdAt: Date;
+  updatedAt: Date;
+}
diff --git a/packages/shared/src/types/engine.ts b/packages/shared/src/types/engine.ts
index e3647ee..32c5983 100644
--- a/packages/shared/src/types/engine.ts
+++ b/packages/shared/src/types/engine.ts
@@ -39,6 +39,12 @@ export interface ConflictDetail {
   message: string;
 }
 
+export interface AbsenceDay {
+  date: Date;
+  type: import("./calculation-rules.js").AbsenceTrigger;
+  isHalfDay?: boolean;
+}
+
 export interface AllocationCalculationInput {
   lcrCents: number;
   hoursPerDay: number;
@@ -51,6 +57,14 @@ export interface AllocationCalculationInput {
   recurrence?: import("./allocation.js").RecurrencePattern;
   /** APPROVED vacation dates — these days are blocked regardless of other settings */
   vacationDates?: Date[];
+  /** Typed absence days (vacation, sick, public holiday) — used by the rules engine */
+  absenceDays?: AbsenceDay[];
+  /** Calculation rules — when provided, absence days are evaluated against these rules */
+  calculationRules?: import("./calculation-rules.js").CalculationRule[];
+  /** Order type of the project — used for rule matching */
+  orderType?: string;
+  /** Project ID — used for rule matching */
+  projectId?: string;
 }
 
 export interface AllocationCalculationResult {
@@ -59,6 +73,10 @@ export interface AllocationCalculationResult {
   totalCostCents: number;
   dailyCostCents: number;
   dailyBreakdown: DailyBreakdown[];
+  /** Total hours counting toward chargeability (rules-adjusted) */
+  totalChargeableHours?: number;
+  /** Cost after rule adjustments (e.g. sick days zeroed out) */
+  totalProjectCostCents?: number;
 }
 
 export interface DailyBreakdown {
@@ -66,6 +84,10 @@ export interface DailyBreakdown {
   isWorkday: boolean;
   hours: number;
   costCents: number;
+  /** Absence type for this day (if any rule matched) */
+  absenceType?: import("./calculation-rules.js").AbsenceTrigger;
+  /** Hours that count toward chargeability (may differ from hours when rules apply) */
+  chargeableHours?: number;
 }
 
 export interface BudgetStatus {
diff --git a/packages/shared/src/types/index.ts b/packages/shared/src/types/index.ts
index ac8d992..bbf159b 100644
--- a/packages/shared/src/types/index.ts
+++ b/packages/shared/src/types/index.ts
@@ -18,3 +18,4 @@ export * from "./utilization-category.js";
 export * from "./client.js";
 export * from "./management-level.js";
 export * from "./dispo-import.js";
+export * from "./calculation-rules.js";
diff --git a/plan.md b/plan.md
new file mode 100644
index 0000000..3985527
--- /dev/null
+++ b/plan.md
@@ -0,0 +1,286 @@
+# Plan: Calculation Rules Engine
+
+## Anforderungsanalyse
+
+Planarchy berechnet Kosten und Chargeability aktuell hart verdrahtet: Vacation blockiert Stunden komplett, Sick Days werden nicht modelliert, und die Chargeability-Berechnung kennt keine Regeln fuer die Entkopplung von "Person ist chargeable" vs. "Projekt wird belastet".
+
+**Gewuenschtes Verhalten (Beispiele):**
+
+| Szenario | Person chargeable? | Projekt belastet? | Heute |
+|----------|-------------------|-------------------|-------|
+| Krank + gebucht auf Projekt | Ja | Nein | Nicht modelliert |
+| Urlaub + gebucht auf Projekt | Ja | Nein | Urlaub blockiert Stunden komplett |
+| Urlaub, nicht gebucht | Ja | — | Urlaub mindert SAH |
+| Normal gebucht | Ja | Ja | Korrekt |
+
+**Kernidee:** Ein regelbasiertes System, das pro Tag entscheidet:
+1. **costEffect** — Wird der Tag dem Projekt belastet? (`charge` / `zero` / `reduce`)
+2. **chargeabilityEffect** — Zaehlt der Tag fuer die Chargeability der Person? (`count` / `skip`)
+
+---
+
+## Betroffene Pakete & Dateien
+
+| Paket | Dateien | Art der Aenderung |
+|-------|---------|-----------------|
+| shared | `src/types/calculation-rules.ts` | create |
+| shared | `src/schemas/calculation-rules.schema.ts` | create |
+| shared | `src/types/index.ts` | edit (re-export) |
+| db | `prisma/schema.prisma` | edit (neues Model) |
+| engine | `src/rules/engine.ts` | create |
+| engine | `src/rules/default-rules.ts` | create |
+| engine | `src/rules/index.ts` | create |
+| engine | `src/allocation/calculator.ts` | edit (Rules-Integration) |
+| engine | `src/chargeability/calculator.ts` | edit (Rules-Integration) |
+| engine | `src/budget/monitor.ts` | edit (Rules-Integration) |
+| engine | `src/__tests__/rules-engine.test.ts` | create |
+| engine | `src/__tests__/calculator-rules.test.ts` | create |
+| api | `src/router/calculation-rules.ts` | create |
+| api | `src/router/index.ts` | edit (Router registrieren) |
+| api | `src/router/timeline.ts` | edit (Rules durchreichen) |
+| api | `src/router/allocation.ts` | edit (Rules bei Berechnung) |
+| web | `src/app/(app)/admin/calculation-rules/page.tsx` | create |
+| web | `src/components/admin/CalculationRulesClient.tsx` | create |
+| web | `src/components/layout/AppShell.tsx` | edit (Navigation) |
+
+---
+
+## Architektur
+
+### Datenmodell
+
+```prisma
+model CalculationRule {
+  id          String   @id @default(cuid())
+  name        String                         // "Sick Leave — Chargeable, No Project Cost"
+  description String?
+
+  // ── Matching ──
+  triggerType  AbsenceTrigger               // SICK, VACATION, PUBLIC_HOLIDAY, CUSTOM
+  // Optional narrowing (null = all):
+  projectId   String?
+  orderType   OrderType?                    // CHARGEABLE, INTERNAL, INVESTMENT
+
+  // ── Effects ──
+  costEffect           CostEffect          // CHARGE, ZERO, REDUCE
+  costReductionPercent Int?                 // nur bei REDUCE (0-100)
+  chargeabilityEffect  ChargeabilityEffect  // COUNT, SKIP
+
+  // ── Ordering ──
+  priority    Int      @default(0)          // hoehere Prioritaet gewinnt
+  isActive    Boolean  @default(true)
+
+  createdAt   DateTime @default(now())
+  updatedAt   DateTime @updatedAt
+
+  project     Project? @relation(fields: [projectId], references: [id])
+
+  @@map("calculation_rules")
+}
+
+enum AbsenceTrigger {
+  SICK
+  VACATION
+  PUBLIC_HOLIDAY
+  CUSTOM
+}
+
+enum CostEffect {
+  CHARGE   // normaler Kostenauftrag ans Projekt
+  ZERO     // keine Kosten ans Projekt
+  REDUCE   // reduzierte Kosten (costReductionPercent)
+}
+
+enum ChargeabilityEffect {
+  COUNT    // Person zaehlt als chargeable
+  SKIP     // Person zaehlt nicht (Tag wird aus SAH-Nenner genommen)
+}
+```
+
+### Rule Matching (Engine)
+
+```
+findMatchingRule(day, absenceType, projectId?, orderType?):
+  candidates = rules.filter(r =>
+    r.isActive &&
+    r.triggerType === absenceType &&
+    (r.projectId === null || r.projectId === projectId) &&
+    (r.orderType === null || r.orderType === orderType)
+  )
+  // Spezifischere Regeln gewinnen, dann priority
+  return candidates.sort(bySpecificityThenPriority)[0] ?? DEFAULT_RULE
+```
+
+**Specificity scoring:**
+| Filter combination | Score |
+|-------------------|-------|
+| projectId + orderType | 3 |
+| projectId only | 2 |
+| orderType only | 1 |
+| global (no filter) | 0 |
+
+### Default Rules (Seed)
+
+| Name | Trigger | Cost | Chargeability |
+|------|---------|------|---------------|
+| Urlaub — Person chargeable, Projekt nicht belastet | VACATION | ZERO | COUNT |
+| Krankheit — Person chargeable, Projekt nicht belastet | SICK | ZERO | COUNT |
+| Feiertag — kein Effekt | PUBLIC_HOLIDAY | ZERO | SKIP |
+
+### Integration Points
+
+**1. `calculateAllocation()` (engine/allocation/calculator.ts)**
+
+Aktuell: Vacation-Tag → `effectiveHours = 0`, `costCents = 0`.
+Neu: Fuer jeden Tag pruefen ob eine Regel greift. Das DailyBreakdown bekommt zwei neue Felder:
+
+```ts
+interface DailyBreakdown {
+  date: Date;
+  isWorkday: boolean;
+  hours: number;          // effektive Stunden (wie bisher)
+  costCents: number;      // Kosten fuer das Projekt (regel-gesteuert)
+  // NEU:
+  absenceType?: AbsenceTrigger;    // was fuer ein Tag ist das?
+  chargeableHours: number;         // Stunden die fuer Chargeability zaehlen
+}
+```
+
+- Wenn `costEffect === ZERO`: `costCents = 0`, aber `chargeableHours = hoursPerDay`
+- Wenn `costEffect === REDUCE`: `costCents = round(normal * (100 - reduction) / 100)`
+- Wenn `chargeabilityEffect === COUNT`: `chargeableHours = hoursPerDay` (selbst wenn absent)
+- Wenn `chargeabilityEffect === SKIP`: `chargeableHours = 0`
+
+**2. `deriveResourceForecast()` (engine/chargeability/calculator.ts)**
+
+Aktuell: `absence` Ratio ist immer 0 (kein Input).
+Neu: Erhaelt `chargeableHours` pro Assignment-Slice statt nur `hoursPerDay * workingDays`.
+Die Summe der chargeable Hours wird gegen SAH normiert.
+
+**3. `computeBudgetStatus()` (engine/budget/monitor.ts)**
+
+Aktuell: `dailyCostCents * workingDays` — nimmt an, jeder Tag kostet gleich.
+Neu: Bekommt optional ein `adjustedTotalCostCents` pro Allocation, das bereits die Regel-Reduktionen enthaelt. Fallback auf bisherige Berechnung wenn keine Rules aktiv.
+
+**4. Timeline Router (api/router/timeline.ts)**
+
+Laedt Rules einmal, reicht sie an den Calculator durch. Rules werden gecacht (sie aendern sich selten).
+
+---
+
+## Task-Liste (atomare Schritte in Reihenfolge)
+
+### Phase A: Datenmodell & Types
+
+- [x] **A1:** Shared Types erstellen — `AbsenceTrigger`, `CostEffect`, `ChargeabilityEffect`, `CalculationRule` Interface → `packages/shared/src/types/calculation-rules.ts`
+- [x] **A2:** Zod Schemas erstellen — `CreateCalculationRuleSchema`, `UpdateCalculationRuleSchema` → `packages/shared/src/schemas/calculation-rules.schema.ts`
+- [x] **A3:** Re-exports in `packages/shared/src/types/index.ts` und `packages/shared/src/schemas/index.ts`
+- [x] **A4:** Prisma Schema erweitern — `CalculationRule` Model + Enums → `packages/db/prisma/schema.prisma`
+- [x] **A5:** Prisma Client regenerieren (db:push erfordert laufende DB)
+
+### Phase B: Rules Engine (Pure Logic)
+
+- [x] **B1:** Rule Matching Engine — `findMatchingRule()`, Specificity-Scoring → `packages/engine/src/rules/engine.ts`
+- [x] **B2:** Default Rules — hartcodierte Fallback-Regeln → `packages/engine/src/rules/default-rules.ts`
+- [x] **B3:** Index-Datei → `packages/engine/src/rules/index.ts`
+- [x] **B4:** Tests fuer Rule Matching — 20 Tests (Specificity, Priority, Fallback, applyCostEffect) → `packages/engine/src/__tests__/rules-engine.test.ts`
+
+### Phase C: Calculator-Integration
+
+- [x] **C1:** `DailyBreakdown` erweitern — `absenceType`, `chargeableHours` → `packages/shared/src/types/engine.ts`
+- [x] **C2:** `AllocationCalculationInput` erweitern — `calculationRules`, `absenceDays`, `projectId`, `orderType` → `packages/shared/src/types/engine.ts`
+- [x] **C3:** `calculateAllocation()` anpassen — Regel-Lookup pro Tag, neue Felder befuellen → `packages/engine/src/allocation/calculator.ts`
+- [x] **C4:** `AllocationCalculationResult` erweitern — `totalChargeableHours`, `totalProjectCostCents` (regelbereinigt)
+- [x] **C5:** `deriveResourceForecast()` — `AssignmentSlice.totalChargeableHours` optional, verwendet statt `hoursPerDay*workingDays` → `packages/engine/src/chargeability/calculator.ts`
+- [x] **C6:** `computeBudgetStatus()` — optional `adjustedTotalCostCents` pro Allocation → `packages/engine/src/budget/monitor.ts`
+- [x] **C7:** Tests — 9 Tests (Sick+Booked, Vacation+Booked, Feiertag, Half-Day, REDUCE, Defaults) → `packages/engine/src/__tests__/calculator-rules.test.ts`
+- [x] **C8:** Bestehende Calculator-Tests verifiziert — 283/283 bestanden, volle Rueckwaertskompatibilitaet
+
+### Phase D: API Router
+
+- [x] **D1:** `calculation-rules.ts` Router — CRUD (list, getById, getActive, create, update, delete) → `packages/api/src/router/calculation-rules.ts`
+- [x] **D2:** Router registrieren → `packages/api/src/router/index.ts`
+- [x] **D3:** Timeline Router — `loadCalculationRules()` + `buildAbsenceDays()` Helpers; `updateAllocationInline` + `applyShift` nutzen Rules → `packages/api/src/router/timeline.ts`
+- [x] **D4:** Allocation Router — nutzt calculateAllocation nicht direkt (laeuft ueber Timeline); kein Handlungsbedarf
+- [x] **D5:** Seed — 3 Default-Regeln einfuegen → `packages/db/src/seed.ts`
+
+### Phase E: Admin UI
+
+- [x] **E1:** `CalculationRulesClient.tsx` — Tabelle mit Rules, Create/Edit Modal → `apps/web/src/components/admin/CalculationRulesClient.tsx`
+- [x] **E2:** Page Route → `apps/web/src/app/(app)/admin/calculation-rules/page.tsx`
+- [x] **E3:** AppShell Navigation — "Calc. Rules" unter Admin-Bereich → `apps/web/src/components/layout/AppShell.tsx`
+
+### Phase F: Sick Days Pipeline
+
+- [x] **F1:** Timeline Router — `buildAbsenceDays()` laedt SICK/VACATION/PUBLIC_HOLIDAY mit Typ-Tag und reicht an Calculator → `packages/api/src/router/timeline.ts`
+- [x] **F2:** Chargeability Report — Vacation-Query um `type`+`isHalfDay` erweitert; per-Monat AbsenceDays gebaut; `calculateAllocation()` mit Rules fuer `totalChargeableHours`; Rules aus DB geladen → `packages/api/src/router/chargeability-report.ts`
+
+---
+
+## Abhaengigkeiten
+
+```
+A1 ─── A2 ─── A3 (shared types muessen zuerst stehen)
+A4 ─── A5      (Schema vor DB push)
+
+B1 ─── B4      (Engine vor Tests)
+B2 ─── B3      (Default Rules vor Index)
+
+A3 ──┐
+     ├── B1    (Types muessen existieren)
+A5 ──┘
+
+B4 ──┐
+     ├── C1 → C2 → C3 → C4 (Calculator braucht Types + Engine)
+     │
+C3 ──── C5     (Chargeability braucht neue DailyBreakdown-Felder)
+C3 ──── C6     (Budget braucht adjustierte Kosten)
+C3 ──── C7     (Tests nach Implementation)
+C4 ──── C8     (Regressionstest)
+
+C4 ──── D1     (Router braucht funktionierende Engine)
+D1 ──── D2     (Registrierung nach Router)
+D1 ──── D3     (Timeline braucht Router fuer Daten-Zugriff)
+D1 ──── D4
+
+D2 ──── E1 → E2 → E3 (UI braucht API)
+
+D3 ──── F1     (Sick Dates Pipeline braucht Rule-aware Timeline)
+C5 ──── F2     (Forecast braucht neue chargeableHours)
+```
+
+**Parallelisierbar:**
+- A1+A2+A3 parallel zu A4 (Types vs. Schema — keine Datei-Ueberschneidung)
+- B1+B2 parallel (verschiedene Dateien)
+- C5+C6 parallel (verschiedene Calculator-Dateien, nachdem C3 fertig)
+- E1+E2+E3 als eigener Stream nachdem D2 fertig
+
+---
+
+## Akzeptanzkriterien
+
+- [ ] `pnpm --filter @planarchy/engine exec vitest run` — alle bestehenden Tests + neue Rules-Tests gruen
+- [ ] `pnpm --filter @planarchy/api exec vitest run` — alle Tests gruen
+- [ ] `pnpm --filter @planarchy/web exec tsc --noEmit` — 0 neue Errors
+- [ ] Ohne konfigurierte Rules: exakt gleiches Verhalten wie heute (Rueckwaertskompatibilitaet)
+- [ ] Default-Regeln: Urlaub+Gebucht → Person chargeable, Projekt nicht belastet
+- [ ] Default-Regeln: Krank+Gebucht → Person chargeable, Projekt nicht belastet
+- [ ] Admin-UI: Rules erstellen, bearbeiten, loeschen, (de-)aktivieren, priorisieren
+- [ ] Budget Monitor zeigt regelkonforme Kosten (Sick/Vacation-Tage nicht auf Projekt)
+- [ ] Chargeability Report zeigt korrekte Ratios (Sick/Vacation als chargeable)
+
+---
+
+## Risiken & offene Fragen
+
+1. **Rueckwaertskompatibilitaet** — Wenn keine Rules existieren UND kein Seed gelaufen ist, muss der Calculator sich exakt wie heute verhalten. Loesung: `DEFAULT_RULES` als Fallback in der Engine hartcodiert.
+
+2. **Performance** — Rules werden pro Tag pro Allocation evaluiert. Bei 100 Allocations x 250 Tage = 25.000 Evaluierungen. Mitigiert durch: Rules einmal laden + im Memory halten (typisch <10 Regeln), Matching ist O(n) mit n ≈ 5-10.
+
+3. **Sick Days nicht im Allocation-Calculator** — Aktuell kennt `calculateAllocation()` nur `vacationDates`. Es braucht einen neuen Input `sickDates` (oder generischer: `absenceDates` mit Typ-Tag). Die Daten kommen aus der Vacation-Tabelle mit `type = SICK`.
+
+4. **Half-Day Absences** — Das aktuelle System modelliert halbe Tage (`isHalfDay` auf Vacation). Die Rules Engine muss damit umgehen: halber Krankheitstag → halbe Stunden chargeable, halbe Stunden Projektkosten.
+
+5. **Historische Korrektheit** — Aenderungen an Rules wirken sich auf alle zukuenftigen Berechnungen aus. Es gibt kein "Versioning" von Rules. Falls gewuenscht, koennte man `validFrom`/`validTo` Felder ergaenzen — aber erst wenn der Use Case auftritt (YAGNI).
+
+6. **SAH-Integration** — SAH-Calculator hat eigenen Absence-Abzug. Die Rules Engine darf die SAH-Berechnung nicht doppelt reduzieren. Loesung: SAH bleibt wie ist (zaehlt alle Absences ab), die Rules Engine steuert nur die **Zuordnung** der Stunden (chargeable vs. nicht, Projekt vs. nicht).