diff --git a/frontend/src/api/rulebooks.ts b/frontend/src/api/rulebooks.ts
new file mode 100644
index 0000000..77685a6
--- /dev/null
+++ b/frontend/src/api/rulebooks.ts
@@ -0,0 +1,135 @@
+import { apiGet, apiPost, apiPatch, apiDelete } from "@/api/client";
+
+export interface Rulebook {
+  id: number;
+  owner_user_id: number;
+  title: string;
+  description: string;
+  created_at: string | null;
+  updated_at: string | null;
+}
+
+export interface RulebookTopic {
+  id: number;
+  rulebook_id: number;
+  title: string;
+  description: string;
+  order_index: number;
+  created_at: string | null;
+  updated_at: string | null;
+}
+
+export interface Rule {
+  id: number;
+  topic_id: number;
+  title: string;
+  statement: string;
+  why: string;
+  how_to_apply: string;
+  order_index: number;
+  created_at: string | null;
+  updated_at: string | null;
+}
+
+export interface RuleHeader {
+  id: number;
+  title: string;
+  statement: string;
+  topic_id: number;
+}
+
+export interface ApplicableRules {
+  rules: {
+    id: number;
+    title: string;
+    statement: string;
+    topic_title: string;
+    rulebook_title: string;
+  }[];
+  truncated: boolean;
+  subscribed_rulebooks: { id: number; title: string }[];
+}
+
+// ── Rulebooks ───────────────────────────────────────────────────────
+
+export async function listRulebooks(): Promise<Rulebook[]> {
+  const data = await apiGet<{ rulebooks: Rulebook[] }>("/api/rulebooks");
+  return data.rulebooks;
+}
+
+export async function getRulebook(id: number): Promise<Rulebook & { topics: RulebookTopic[] }> {
+  return apiGet(`/api/rulebooks/${id}`);
+}
+
+export async function createRulebook(data: { title: string; description?: string }): Promise<Rulebook> {
+  return apiPost("/api/rulebooks", data);
+}
+
+export async function updateRulebook(id: number, data: Partial<{ title: string; description: string }>): Promise<Rulebook> {
+  return apiPatch(`/api/rulebooks/${id}`, data);
+}
+
+export async function deleteRulebook(id: number): Promise<void> {
+  return apiDelete(`/api/rulebooks/${id}`);
+}
+
+// ── Topics ─────────────────────────────────────────────────────────
+
+export async function listTopics(rulebookId: number): Promise<RulebookTopic[]> {
+  const data = await apiGet<{ topics: RulebookTopic[] }>(`/api/rulebooks/${rulebookId}/topics`);
+  return data.topics;
+}
+
+export async function createTopic(rulebookId: number, data: { title: string; description?: string; order_index?: number }): Promise<RulebookTopic> {
+  return apiPost(`/api/rulebooks/${rulebookId}/topics`, data);
+}
+
+export async function updateTopic(id: number, data: Partial<{ title: string; description: string; order_index: number }>): Promise<RulebookTopic> {
+  return apiPatch(`/api/rulebook-topics/${id}`, data);
+}
+
+export async function deleteTopic(id: number): Promise<void> {
+  return apiDelete(`/api/rulebook-topics/${id}`);
+}
+
+// ── Rules ──────────────────────────────────────────────────────────
+
+export async function listRules(filters: { rulebook_id?: number; topic_id?: number; project_id?: number } = {}): Promise<Rule[]> {
+  const params = new URLSearchParams();
+  if (filters.rulebook_id) params.set("rulebook_id", String(filters.rulebook_id));
+  if (filters.topic_id) params.set("topic_id", String(filters.topic_id));
+  if (filters.project_id) params.set("project_id", String(filters.project_id));
+  const qs = params.toString();
+  const data = await apiGet<{ rules: Rule[] }>(`/api/rules${qs ? `?${qs}` : ""}`);
+  return data.rules;
+}
+
+export async function getRule(id: number): Promise<Rule> {
+  return apiGet(`/api/rules/${id}`);
+}
+
+export async function createRule(topicId: number, data: { title: string; statement: string; why?: string; how_to_apply?: string; order_index?: number }): Promise<Rule> {
+  return apiPost(`/api/rulebook-topics/${topicId}/rules`, data);
+}
+
+export async function updateRule(id: number, data: Partial<{ title: string; statement: string; why: string; how_to_apply: string; order_index: number }>): Promise<Rule> {
+  return apiPatch(`/api/rules/${id}`, data);
+}
+
+export async function deleteRule(id: number): Promise<void> {
+  return apiDelete(`/api/rules/${id}`);
+}
+
+// ── Subscriptions ──────────────────────────────────────────────────
+
+export async function subscribeProject(projectId: number, rulebookId: number): Promise<void> {
+  await apiPost(`/api/projects/${projectId}/rulebook-subscriptions`, { rulebook_id: rulebookId });
+}
+
+export async function unsubscribeProject(projectId: number, rulebookId: number): Promise<void> {
+  return apiDelete(`/api/projects/${projectId}/rulebook-subscriptions/${rulebookId}`);
+}
+
+export async function getProjectApplicableRules(projectId: number): Promise<ApplicableRules> {
+  return apiGet(`/api/projects/${projectId}/rules`);
+}
diff --git a/frontend/src/stores/rulebooks.ts b/frontend/src/stores/rulebooks.ts
new file mode 100644
index 0000000..61d2b88
--- /dev/null
+++ b/frontend/src/stores/rulebooks.ts
@@ -0,0 +1,128 @@
+import { ref } from "vue";
+import { defineStore } from "pinia";
+import * as api from "@/api/rulebooks";
+import type { Rulebook, RulebookTopic, Rule, RuleHeader } from "@/api/rulebooks";
+import { useToastStore } from "@/stores/toast";
+
+export const useRulebooksStore = defineStore("rulebooks", () => {
+  const rulebooks = ref<Rulebook[]>([]);
+  const topicsByRulebook = ref<Record<number, RulebookTopic[]>>({});
+  const rulesByTopic = ref<Record<number, RuleHeader[]>>({});
+  const currentRule = ref<Rule | null>(null);
+  const loading = ref(false);
+
+  async function fetchRulebooks() {
+    loading.value = true;
+    try {
+      rulebooks.value = await api.listRulebooks();
+    } catch (e) {
+      useToastStore().show("Failed to load rulebooks", "error");
+      throw e;
+    } finally {
+      loading.value = false;
+    }
+  }
+
+  async function fetchTopics(rulebookId: number) {
+    try {
+      topicsByRulebook.value[rulebookId] = await api.listTopics(rulebookId);
+    } catch (e) {
+      useToastStore().show("Failed to load topics", "error");
+      throw e;
+    }
+  }
+
+  async function fetchRules(topicId: number) {
+    try {
+      const rules = await api.listRules({ topic_id: topicId });
+      rulesByTopic.value[topicId] = rules.map((r) => ({
+        id: r.id, title: r.title, statement: r.statement, topic_id: r.topic_id,
+      }));
+    } catch (e) {
+      useToastStore().show("Failed to load rules", "error");
+      throw e;
+    }
+  }
+
+  async function fetchRule(id: number) {
+    currentRule.value = await api.getRule(id);
+  }
+
+  async function createRulebook(data: { title: string; description?: string }) {
+    const rb = await api.createRulebook(data);
+    rulebooks.value.push(rb);
+    return rb;
+  }
+
+  async function updateRulebook(id: number, data: Partial<Pick<Rulebook, "title" | "description">>) {
+    const rb = await api.updateRulebook(id, data);
+    const idx = rulebooks.value.findIndex((r) => r.id === id);
+    if (idx >= 0) rulebooks.value[idx] = rb;
+    return rb;
+  }
+
+  async function deleteRulebook(id: number) {
+    await api.deleteRulebook(id);
+    rulebooks.value = rulebooks.value.filter((r) => r.id !== id);
+    delete topicsByRulebook.value[id];
+  }
+
+  async function createTopic(rulebookId: number, data: { title: string; description?: string }) {
+    const topic = await api.createTopic(rulebookId, data);
+    if (!topicsByRulebook.value[rulebookId]) topicsByRulebook.value[rulebookId] = [];
+    topicsByRulebook.value[rulebookId].push(topic);
+    return topic;
+  }
+
+  async function updateTopic(id: number, data: Partial<Pick<RulebookTopic, "title" | "description" | "order_index">>) {
+    const topic = await api.updateTopic(id, data);
+    for (const rbId of Object.keys(topicsByRulebook.value)) {
+      const list = topicsByRulebook.value[Number(rbId)];
+      const idx = list.findIndex((t) => t.id === id);
+      if (idx >= 0) list[idx] = topic;
+    }
+    return topic;
+  }
+
+  async function deleteTopic(id: number) {
+    await api.deleteTopic(id);
+    for (const rbId of Object.keys(topicsByRulebook.value)) {
+      topicsByRulebook.value[Number(rbId)] = topicsByRulebook.value[Number(rbId)].filter((t) => t.id !== id);
+    }
+    delete rulesByTopic.value[id];
+  }
+
+  async function createRule(topicId: number, data: { title: string; statement: string; why?: string; how_to_apply?: string }) {
+    const rule = await api.createRule(topicId, data);
+    if (!rulesByTopic.value[topicId]) rulesByTopic.value[topicId] = [];
+    rulesByTopic.value[topicId].push({ id: rule.id, title: rule.title, statement: rule.statement, topic_id: rule.topic_id });
+    return rule;
+  }
+
+  async function updateRule(id: number, data: Partial<Pick<Rule, "title" | "statement" | "why" | "how_to_apply" | "order_index">>) {
+    const rule = await api.updateRule(id, data);
+    if (currentRule.value?.id === id) currentRule.value = rule;
+    for (const tid of Object.keys(rulesByTopic.value)) {
+      const list = rulesByTopic.value[Number(tid)];
+      const idx = list.findIndex((r) => r.id === id);
+      if (idx >= 0) list[idx] = { id: rule.id, title: rule.title, statement: rule.statement, topic_id: rule.topic_id };
+    }
+    return rule;
+  }
+
+  async function deleteRule(id: number) {
+    await api.deleteRule(id);
+    if (currentRule.value?.id === id) currentRule.value = null;
+    for (const tid of Object.keys(rulesByTopic.value)) {
+      rulesByTopic.value[Number(tid)] = rulesByTopic.value[Number(tid)].filter((r) => r.id !== id);
+    }
+  }
+
+  return {
+    rulebooks, topicsByRulebook, rulesByTopic, currentRule, loading,
+    fetchRulebooks, fetchTopics, fetchRules, fetchRule,
+    createRulebook, updateRulebook, deleteRulebook,
+    createTopic, updateTopic, deleteTopic,
+    createRule, updateRule, deleteRule,
+  };
+});