diff --git a/extensions/feishu/src/dedup-store.ts b/extensions/feishu/src/dedup-store.ts
new file mode 100644
index 00000000000..5168230fa24
--- /dev/null
+++ b/extensions/feishu/src/dedup-store.ts
@@ -0,0 +1,91 @@
+import fs from "node:fs";
+import os from "node:os";
+import path from "node:path";
+
+const DEFAULT_DEDUP_DIR = path.join(os.homedir(), ".openclaw", "feishu", "dedup");
+const MAX_ENTRIES_PER_FILE = 10_000;
+const CLEANUP_PROBABILITY = 0.02;
+
+type DedupData = Record<string, number>;
+
+/**
+ * Filesystem-backed dedup store.  Each "namespace" (typically a Feishu account
+ * ID) maps to a single JSON file containing `{ messageId: timestampMs }` pairs.
+ *
+ * Writes use atomic rename to avoid partial-read corruption.  Probabilistic
+ * cleanup keeps the file size bounded without adding latency to every call.
+ */
+export class DedupStore {
+  private readonly dir: string;
+  private cache = new Map<string, DedupData>();
+
+  constructor(dir?: string) {
+    this.dir = dir ?? DEFAULT_DEDUP_DIR;
+  }
+
+  private filePath(namespace: string): string {
+    const safe = namespace.replace(/[^a-zA-Z0-9_-]/g, "_");
+    return path.join(this.dir, `${safe}.json`);
+  }
+
+  async load(namespace: string): Promise<DedupData> {
+    const cached = this.cache.get(namespace);
+    if (cached) return cached;
+
+    try {
+      const raw = await fs.promises.readFile(this.filePath(namespace), "utf-8");
+      const data: DedupData = JSON.parse(raw);
+      this.cache.set(namespace, data);
+      return data;
+    } catch {
+      const data: DedupData = {};
+      this.cache.set(namespace, data);
+      return data;
+    }
+  }
+
+  async has(namespace: string, messageId: string, ttlMs: number): Promise<boolean> {
+    const data = await this.load(namespace);
+    const ts = data[messageId];
+    if (ts == null) return false;
+    if (Date.now() - ts > ttlMs) {
+      delete data[messageId];
+      return false;
+    }
+    return true;
+  }
+
+  async record(namespace: string, messageId: string, ttlMs: number): Promise<void> {
+    const data = await this.load(namespace);
+    data[messageId] = Date.now();
+
+    if (Math.random() < CLEANUP_PROBABILITY) {
+      this.evict(data, ttlMs);
+    }
+
+    await this.flush(namespace, data);
+  }
+
+  private evict(data: DedupData, ttlMs: number): void {
+    const now = Date.now();
+    for (const key of Object.keys(data)) {
+      if (now - data[key] > ttlMs) delete data[key];
+    }
+
+    const keys = Object.keys(data);
+    if (keys.length > MAX_ENTRIES_PER_FILE) {
+      keys
+        .sort((a, b) => data[a] - data[b])
+        .slice(0, keys.length - MAX_ENTRIES_PER_FILE)
+        .forEach((k) => delete data[k]);
+    }
+  }
+
+  private async flush(namespace: string, data: DedupData): Promise<void> {
+    await fs.promises.mkdir(this.dir, { recursive: true });
+    const fp = this.filePath(namespace);
+    const tmp = `${fp}.tmp.${process.pid}`;
+    await fs.promises.writeFile(tmp, JSON.stringify(data), "utf-8");
+    await fs.promises.rename(tmp, fp);
+  }
+}