diff --git a/bun.lock b/bun.lock
index cec214a..8b774c4 100644
--- a/bun.lock
+++ b/bun.lock
@@ -18,6 +18,14 @@
         "xxhash-wasm": "^1.1.0",
       },
     },
+    "packages/json-cas-fs": {
+      "name": "@uncaged/json-cas-fs",
+      "version": "0.1.0",
+      "dependencies": {
+        "@uncaged/json-cas": "workspace:^",
+        "cborg": "^4.2.3",
+      },
+    },
   },
   "packages": {
     "@biomejs/biome": ["@biomejs/biome@2.4.15", "", { "optionalDependencies": { "@biomejs/cli-darwin-arm64": "2.4.15", "@biomejs/cli-darwin-x64": "2.4.15", "@biomejs/cli-linux-arm64": "2.4.15", "@biomejs/cli-linux-arm64-musl": "2.4.15", "@biomejs/cli-linux-x64": "2.4.15", "@biomejs/cli-linux-x64-musl": "2.4.15", "@biomejs/cli-win32-arm64": "2.4.15", "@biomejs/cli-win32-x64": "2.4.15" }, "bin": { "biome": "bin/biome" } }, "sha512-j5VH3a/h/HXTKBM50MDMxRCzkeLv9S2XJcW2WgnZT1+xyisi+0bISrXR82gCX+8S9lvK0skEvHJRN+3Ktr2hlw=="],
@@ -40,6 +48,8 @@
 
     "@uncaged/json-cas": ["@uncaged/json-cas@workspace:packages/json-cas"],
 
+    "@uncaged/json-cas-fs": ["@uncaged/json-cas-fs@workspace:packages/json-cas-fs"],
+
     "ajv": ["ajv@8.20.0", "", { "dependencies": { "fast-deep-equal": "^3.1.3", "fast-uri": "^3.0.1", "json-schema-traverse": "^1.0.0", "require-from-string": "^2.0.2" } }, "sha512-Thbli+OlOj+iMPYFBVBfJ3OmCAnaSyNn4M1vz9T6Gka5Jt9ba/HIR56joy65tY6kx/FCF5VXNB819Y7/GUrBGA=="],
 
     "cborg": ["cborg@4.5.8", "", { "bin": { "cborg": "lib/bin.js" } }, "sha512-6/viltD51JklRhq4L7jC3zgy6gryuG5xfZ3kzpE+PravtyeQLeQmCYLREhQH7pWENg5pY4Yu/XCd6a7dKScVlw=="],
diff --git a/packages/json-cas-fs/package.json b/packages/json-cas-fs/package.json
new file mode 100644
index 0000000..6e1171c
--- /dev/null
+++ b/packages/json-cas-fs/package.json
@@ -0,0 +1,16 @@
+{
+  "name": "@uncaged/json-cas-fs",
+  "version": "0.1.0",
+  "type": "module",
+  "main": "./src/index.ts",
+  "exports": {
+    ".": "./src/index.ts"
+  },
+  "scripts": {
+    "test": "bun test"
+  },
+  "dependencies": {
+    "@uncaged/json-cas": "workspace:^",
+    "cborg": "^4.2.3"
+  }
+}
diff --git a/packages/json-cas-fs/src/index.ts b/packages/json-cas-fs/src/index.ts
new file mode 100644
index 0000000..e226ff3
--- /dev/null
+++ b/packages/json-cas-fs/src/index.ts
@@ -0,0 +1 @@
+export { createFsStore } from "./store.js";
diff --git a/packages/json-cas-fs/src/store.test.ts b/packages/json-cas-fs/src/store.test.ts
new file mode 100644
index 0000000..00e6da5
--- /dev/null
+++ b/packages/json-cas-fs/src/store.test.ts
@@ -0,0 +1,229 @@
+import { afterEach, beforeEach, describe, expect, test } from "bun:test";
+import { mkdtempSync, rmSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import type { CasNode } from "@uncaged/json-cas";
+import {
+  bootstrap,
+  computeHash,
+  computeSelfHash,
+  verify,
+} from "@uncaged/json-cas";
+
+import { createFsStore } from "./store.js";
+
+function makeTmpDir(): string {
+  return mkdtempSync(join(tmpdir(), "json-cas-fs-test-"));
+}
+
+// ──────────────────────────────────────────────────────────────────────────────
+// init and bootstrap
+// ──────────────────────────────────────────────────────────────────────────────
+describe("createFsStore – init and bootstrap", () => {
+  let dir: string;
+  beforeEach(() => {
+    dir = makeTmpDir();
+  });
+  afterEach(() => {
+    rmSync(dir, { recursive: true, force: true });
+  });
+
+  test("store opens against an existing empty dir", () => {
+    const store = createFsStore(dir);
+    expect(store.list()).toEqual([]);
+  });
+
+  test("store creates the directory on first put", async () => {
+    const nested = join(dir, "sub", "store");
+    const store = createFsStore(nested);
+    const typeHash = await computeSelfHash({ name: "t" });
+    await store.put(typeHash, { x: 1 });
+    expect(store.list()).toHaveLength(1);
+  });
+
+  test("bootstrap returns a valid 13-char self-referencing hash", async () => {
+    const store = createFsStore(dir);
+    const hash = await bootstrap(store);
+
+    expect(hash).toHaveLength(13);
+    expect(hash).toMatch(/^[0-9A-HJKMNP-TV-Z]{13}$/);
+
+    const node = store.get(hash) as CasNode;
+    expect(node.type).toBe(hash);
+  });
+
+  test("bootstrap is idempotent across calls", async () => {
+    const store = createFsStore(dir);
+    const h1 = await bootstrap(store);
+    const h2 = await bootstrap(store);
+
+    expect(h1).toBe(h2);
+    expect(store.list()).toHaveLength(1);
+  });
+});
+
+// ──────────────────────────────────────────────────────────────────────────────
+// persistence round-trip
+// ──────────────────────────────────────────────────────────────────────────────
+describe("createFsStore – persistence round-trip", () => {
+  let dir: string;
+  beforeEach(() => {
+    dir = makeTmpDir();
+  });
+  afterEach(() => {
+    rmSync(dir, { recursive: true, force: true });
+  });
+
+  test("second store instance reads nodes written by first", async () => {
+    const typeHash = await computeSelfHash({ name: "my-type" });
+
+    const store1 = createFsStore(dir);
+    const h1 = await store1.put(typeHash, { msg: "hello" });
+    const h2 = await store1.put(typeHash, { msg: "world" });
+
+    const store2 = createFsStore(dir);
+    expect(store2.has(h1)).toBe(true);
+    expect(store2.has(h2)).toBe(true);
+    expect(store2.list()).toHaveLength(2);
+  });
+
+  test("round-trip preserves type, payload, and timestamp", async () => {
+    const typeHash = await computeSelfHash({ name: "round-trip" });
+
+    const store1 = createFsStore(dir);
+    const hash = await store1.put(typeHash, { value: 42 });
+    const original = store1.get(hash) as CasNode;
+
+    const store2 = createFsStore(dir);
+    const loaded = store2.get(hash) as CasNode;
+
+    expect(loaded.type).toBe(original.type);
+    expect(loaded.payload).toEqual(original.payload);
+    expect(loaded.timestamp).toBe(original.timestamp);
+  });
+
+  test("bootstrap survives round-trip: self-referencing node reloads correctly", async () => {
+    const store1 = createFsStore(dir);
+    const hash = await bootstrap(store1);
+
+    const store2 = createFsStore(dir);
+    const node = store2.get(hash) as CasNode;
+    expect(node.type).toBe(hash);
+  });
+
+  test("put is idempotent across instances: timestamp unchanged on second put", async () => {
+    const typeHash = await computeSelfHash({ name: "idempotent" });
+
+    const store1 = createFsStore(dir);
+    const hash = await store1.put(typeHash, { n: 7 });
+    const ts1 = store1.get(hash)?.timestamp;
+
+    await new Promise((r) => setTimeout(r, 5));
+
+    const store2 = createFsStore(dir);
+    await store2.put(typeHash, { n: 7 });
+    const ts2 = store2.get(hash)?.timestamp;
+
+    expect(ts1).toBe(ts2);
+    expect(store2.list()).toHaveLength(1);
+  });
+});
+
+// ──────────────────────────────────────────────────────────────────────────────
+// has and list
+// ──────────────────────────────────────────────────────────────────────────────
+describe("createFsStore – has and list", () => {
+  let dir: string;
+  beforeEach(() => {
+    dir = makeTmpDir();
+  });
+  afterEach(() => {
+    rmSync(dir, { recursive: true, force: true });
+  });
+
+  test("has returns false before put, true after", async () => {
+    const store = createFsStore(dir);
+    const typeHash = await computeSelfHash({ name: "t" });
+    const hash = await computeHash(typeHash, { x: 1 });
+
+    expect(store.has(hash)).toBe(false);
+    await store.put(typeHash, { x: 1 });
+    expect(store.has(hash)).toBe(true);
+  });
+
+  test("list returns all stored hashes", async () => {
+    const store = createFsStore(dir);
+    const typeHash = await computeSelfHash({ name: "t" });
+
+    const h1 = await store.put(typeHash, { a: 1 });
+    const h2 = await store.put(typeHash, { a: 2 });
+    const h3 = await store.put(typeHash, { a: 3 });
+
+    const all = store.list();
+    expect(all).toHaveLength(3);
+    expect(all).toContain(h1);
+    expect(all).toContain(h2);
+    expect(all).toContain(h3);
+  });
+
+  test("list returns empty array on fresh store", () => {
+    const store = createFsStore(dir);
+    expect(store.list()).toEqual([]);
+  });
+
+  test("get returns null for unknown hash", () => {
+    const store = createFsStore(dir);
+    expect(store.get("0000000000000")).toBeNull();
+  });
+});
+
+// ──────────────────────────────────────────────────────────────────────────────
+// verify on disk-loaded nodes
+// ──────────────────────────────────────────────────────────────────────────────
+describe("createFsStore – verify on disk-loaded nodes", () => {
+  let dir: string;
+  beforeEach(() => {
+    dir = makeTmpDir();
+  });
+  afterEach(() => {
+    rmSync(dir, { recursive: true, force: true });
+  });
+
+  test("verify passes on a normal disk-loaded node", async () => {
+    const typeHash = await computeSelfHash({ name: "verifiable" });
+
+    const store1 = createFsStore(dir);
+    const hash = await store1.put(typeHash, { data: 123 });
+
+    const store2 = createFsStore(dir);
+    const node = store2.get(hash) as CasNode;
+
+    expect(await verify(hash, node)).toBe(true);
+  });
+
+  test("verify passes on a disk-loaded bootstrap node", async () => {
+    const store1 = createFsStore(dir);
+    const hash = await bootstrap(store1);
+
+    const store2 = createFsStore(dir);
+    const node = store2.get(hash) as CasNode;
+
+    expect(await verify(hash, node)).toBe(true);
+  });
+
+  test("verify passes for multiple disk-loaded nodes", async () => {
+    const typeHash = await computeSelfHash({ name: "multi" });
+
+    const store1 = createFsStore(dir);
+    const hashes: string[] = [];
+    for (let i = 0; i < 5; i++) {
+      hashes.push(await store1.put(typeHash, { i }));
+    }
+
+    const store2 = createFsStore(dir);
+    for (const hash of hashes) {
+      const node = store2.get(hash) as CasNode;
+      expect(await verify(hash, node)).toBe(true);
+    }
+  });
+});
diff --git a/packages/json-cas-fs/src/store.ts b/packages/json-cas-fs/src/store.ts
new file mode 100644
index 0000000..2f20ea1
--- /dev/null
+++ b/packages/json-cas-fs/src/store.ts
@@ -0,0 +1,75 @@
+import {
+  mkdirSync,
+  readdirSync,
+  readFileSync,
+  renameSync,
+  writeFileSync,
+} from "node:fs";
+import { join } from "node:path";
+import type { CasNode, Hash, Store } from "@uncaged/json-cas";
+
+import { cborEncode, computeHash, computeSelfHash } from "@uncaged/json-cas";
+import { decode } from "cborg";
+
+function loadDir(dir: string, data: Map<Hash, CasNode>): void {
+  let entries: string[];
+  try {
+    entries = readdirSync(dir);
+  } catch {
+    return;
+  }
+  for (const name of entries) {
+    if (!name.endsWith(".bin")) continue;
+    const hash = name.slice(0, -4) as Hash;
+    try {
+      const buf = readFileSync(join(dir, name));
+      const node = decode(new Uint8Array(buf)) as CasNode;
+      data.set(hash, node);
+    } catch {
+      // skip corrupted files
+    }
+  }
+}
+
+export function createFsStore(dir: string): Store {
+  const data = new Map<Hash, CasNode>();
+  loadDir(dir, data);
+
+  return {
+    async put(typeHash: Hash | null, payload: unknown): Promise<Hash> {
+      const hash =
+        typeHash === null
+          ? await computeSelfHash(payload)
+          : await computeHash(typeHash, payload);
+
+      if (!data.has(hash)) {
+        const type = typeHash === null ? hash : typeHash;
+        const node: CasNode = { type, payload, timestamp: Date.now() };
+        data.set(hash, node);
+
+        mkdirSync(dir, { recursive: true });
+        const tmp = join(dir, `${hash}.tmp`);
+        const dest = join(dir, `${hash}.bin`);
+        writeFileSync(
+          tmp,
+          cborEncode({ type, payload, timestamp: node.timestamp }),
+        );
+        renameSync(tmp, dest);
+      }
+
+      return hash;
+    },
+
+    get(hash: Hash): CasNode | null {
+      return data.get(hash) ?? null;
+    },
+
+    has(hash: Hash): boolean {
+      return data.has(hash);
+    },
+
+    list(): Hash[] {
+      return [...data.keys()];
+    },
+  };
+}
diff --git a/packages/json-cas-fs/tsconfig.json b/packages/json-cas-fs/tsconfig.json
new file mode 100644
index 0000000..75eba9f
--- /dev/null
+++ b/packages/json-cas-fs/tsconfig.json
@@ -0,0 +1,8 @@
+{
+  "extends": "../../tsconfig.json",
+  "compilerOptions": {
+    "rootDir": "src",
+    "outDir": "dist"
+  },
+  "include": ["src"]
+}