diff --git a/src/state/session.ts b/src/state/session.ts
new file mode 100644
index 0000000..28ec4bd
--- /dev/null
+++ b/src/state/session.ts
@@ -0,0 +1,26 @@
+import { mkdirSync, writeFileSync } from "node:fs";
+import { join } from "node:path";
+import type { Message } from "../types";
+
+const SESSION_DIR = join(process.env.HOME ?? "~", ".paikea", "sessions");
+
+export interface Session {
+  id: string;
+  date: string;
+  model: string;
+  messages: Message[];
+}
+
+function ensureSessionDir() {
+  mkdirSync(SESSION_DIR, { recursive: true });
+}
+
+export function saveSession(session: Session) {
+  ensureSessionDir();
+  const filePath = join(SESSION_DIR, `${session.id}.json`);
+  writeFileSync(filePath, JSON.stringify(session, null, 2));
+}
+
+export function createSessionId(): string {
+  return new Date().toISOString().replace(/[:.]/g, "-");
+}
diff --git a/src/state/store.ts b/src/state/store.ts
new file mode 100644
index 0000000..fe596bb
--- /dev/null
+++ b/src/state/store.ts
@@ -0,0 +1,98 @@
+import type {
+  AgentStep,
+  AppState,
+  Message,
+  Step,
+  ThinkingState,
+} from "../types";
+
+type Listener = () => void;
+
+class Store {
+  private state: AppState = {
+    model: null,
+    models: [],
+    messages: [],
+    steps: [],
+    thinking: { active: false, content: "", tokens: 0 },
+    result: "",
+    prompt: "",
+    scrollOffset: 0,
+    thinkingVisible: true,
+    streaming: false,
+    agentSteps: [],
+    toolCallsStreaming: new Map(),
+    uiMode: "normal",
+    toolbarIndex: 0,
+    paletteIndex: 0,
+    suggestions: [],
+    suggestionIndex: -1,
+  };
+
+  private listeners: Listener[] = [];
+
+  get(): AppState {
+    return this.state;
+  }
+
+  set(partial: Partial<AppState>) {
+    this.state = { ...this.state, ...partial };
+    this.notify();
+  }
+
+  subscribe(fn: Listener): () => void {
+    this.listeners.push(fn);
+    return () => {
+      this.listeners = this.listeners.filter((l) => l !== fn);
+    };
+  }
+
+  private notify() {
+    for (const fn of this.listeners) fn();
+  }
+
+  addMessage(msg: Message) {
+    this.state.messages.push(msg);
+    this.notify();
+  }
+
+  setThinking(thinking: Partial<ThinkingState>) {
+    this.state.thinking = { ...this.state.thinking, ...thinking };
+    this.notify();
+  }
+
+  appendResult(text: string) {
+    this.state.result += text;
+    this.notify();
+  }
+
+  clearResult() {
+    this.state.result = "";
+    this.notify();
+  }
+
+  setSteps(steps: Step[]) {
+    this.state.steps = steps;
+    this.notify();
+  }
+
+  addAgentStep(step: AgentStep) {
+    this.state.agentSteps.push(step);
+    this.notify();
+  }
+
+  updateAgentStep(id: string, update: Partial<AgentStep>) {
+    const step = this.state.agentSteps.find((s) => s.id === id);
+    if (step) {
+      Object.assign(step, update);
+      this.notify();
+    }
+  }
+
+  clearAgentSteps() {
+    this.state.agentSteps = [];
+    this.notify();
+  }
+}
+
+export const store = new Store();