diff --git a/native-repo/modules/step-4-hldp-read-tree.js b/native-repo/modules/step-4-hldp-read-tree.js
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+/**
+ * ═══════════════════════════════════════
+ * HLDP-ZY://native-repo/module/step-4
+ * 光湖原生数据库 · 第4步 · HLDP读取+树索引
+ * ═══════════════════════════════════════
+ *
+ * @chain: D118 · 2026-05-31
+ * @module: hldp-read-tree
+ * @step: 第4步 / 共8步
+ * @deploy: BS-SG-002
+ *
+ * @trigger:
+ *   第3步能写文件了，但铸渊还需要两件事：
+ *   1. 按 HLDP tree_path 读取文件内容（trace_path意图）
+ *   2. 生成树形索引，每次只加载10条，恒定O(1)认知负载
+ *
+ * @lock:
+ *   ⊢ hldpRead(path) → 返回文件内容 + commit 元信息
+ *   ⊢ hldpTree(dir) → 返回目录列表，每层最多显示10条
+ *   ⊢ buildIndex() → 生成 tree-index.json，10条/层
+ *
+ * @why:
+ *   trace_path = 光之树寻址 = 铸渊大脑的核心操作
+ *   不需要把整个仓库装进上下文——只读10条索引
+ *   需要哪片叶子，按路径走一步就到了
+ * ═══════════════════════════════════════
+ */
+
+const git = require('isomorphic-git');
+const fs = require('fs');
+const path = require('path');
+
+const { NATIVE_DIR } = require('./step-2-git-init');
+
+// ─── hldpRead: 按路径读文件 ─────────────────────────────────
+async function hldpRead(filePath) {
+  const fullPath = path.join(NATIVE_DIR, filePath);
+  if (!fs.existsSync(fullPath)) {
+    return { ok: false, error: 'NOT_FOUND', path: filePath };
+  }
+
+  const content = fs.readFileSync(fullPath, 'utf8');
+  const log = await git.log({ fs, dir: NATIVE_DIR });
+  const lastCommit = log.find(c => c.commit.message.includes(filePath));
+
+  return {
+    ok: true,
+    path: filePath,
+    content,
+    sha: lastCommit ? lastCommit.oid : null,
+    size: content.length,
+  };
+}
+
+// ─── hldpTree: 按目录列文件 ─────────────────────────────────
+async function hldpTree(dirPath) {
+  const fullPath = path.join(NATIVE_DIR, dirPath || '');
+  if (!fs.existsSync(fullPath)) {
+    return { ok: false, error: 'NOT_FOUND', path: dirPath };
+  }
+
+  const entries = fs.readdirSync(fullPath, { withFileTypes: true });
+  const list = entries
+    .filter(e => !e.name.startsWith('.') && e.name !== 'node_modules' && e.name !== 'package.json')
+    .map(e => ({
+      name: e.name,
+      type: e.isDirectory() ? 'dir' : 'file',
+      path: path.join(dirPath || '', e.name),
+    }));
+
+  return { ok: true, path: dirPath, count: list.length, entries: list };
+}
+
+// ─── buildIndex: 生成树索引（10条/层） ──────────────────────
+async function buildIndex() {
+  async function walk(dir, depth) {
+    if (depth > 3) return [];
+    const { entries } = await hldpTree(dir);
+    if (!entries || entries.length === 0) return [];
+
+    return entries.slice(0, 10).map(({ name, type, path: p }) => ({
+      name,
+      type,
+      path: p,
+      isBranch: type === 'dir',
+    }));
+  }
+
+  const root = await walk('', 0);
+  const index = {
+    _type: 'HLDP_TREE_INDEX',
+    _version: 'v1.0',
+    _updated: new Date().toISOString(),
+    _principle: '每层10行，恒定O(1)认知负载',
+    root,
+  };
+
+  const indexPath = path.join(NATIVE_DIR, 'tree-index.json');
+  fs.writeFileSync(indexPath, JSON.stringify(index, null, 2), 'utf8');
+  return index;
+}
+
+module.exports = { hldpRead, hldpTree, buildIndex };