Memory/QMD: optimize qmd readFile for line-window reads

src/memory/qmd-manager.test.ts

@@ -789,6 +789,26 @@ describe("QmdMemoryManager", () => {
     await manager.close();
   });
 
+  it("reads only requested line ranges without loading the whole file", async () => {
+    const readFileSpy = vi.spyOn(fs, "readFile");
+    const text = Array.from({ length: 50 }, (_, index) => `line-${index + 1}`).join("\n");
+    await fs.writeFile(path.join(workspaceDir, "window.md"), text, "utf-8");
+
+    const resolved = resolveMemoryBackendConfig({ cfg, agentId });
+    const manager = await QmdMemoryManager.create({ cfg, agentId, resolved });
+    expect(manager).toBeTruthy();
+    if (!manager) {
+      throw new Error("manager missing");
+    }
+
+    const result = await manager.readFile({ relPath: "window.md", from: 10, lines: 3 });
+    expect(result.text).toBe("line-10\nline-11\nline-12");
+    expect(readFileSpy).not.toHaveBeenCalled();
+
+    await manager.close();
+    readFileSpy.mockRestore();
+  });
+
   it("throws when sqlite index is busy", async () => {
     const resolved = resolveMemoryBackendConfig({ cfg, agentId });
     const manager = await QmdMemoryManager.create({ cfg, agentId, resolved });

src/memory/qmd-manager.ts

@@ -2,6 +2,7 @@ import { spawn } from "node:child_process";
 import fs from "node:fs/promises";
 import os from "node:os";
 import path from "node:path";
+import readline from "node:readline";
 import type { OpenClawConfig } from "../config/config.js";
 import type {
   MemoryEmbeddingProbeResult,
@@ -353,6 +354,10 @@ export class QmdMemoryManager implements MemorySearchManager {
     if (stat.isSymbolicLink() || !stat.isFile()) {
       throw new Error("path required");
     }
+    if (params.from !== undefined || params.lines !== undefined) {
+      const text = await this.readPartialText(absPath, params.from, params.lines);
+      return { text, path: relPath };
+    }
     const content = await fs.readFile(absPath, "utf-8");
     if (!params.from && !params.lines) {
       return { text: content, path: relPath };
@@ -609,6 +614,35 @@ export class QmdMemoryManager implements MemorySearchManager {
     });
   }
 
+  private async readPartialText(absPath: string, from?: number, lines?: number): Promise<string> {
+    const start = Math.max(1, from ?? 1);
+    const count = Math.max(1, lines ?? Number.POSITIVE_INFINITY);
+    const handle = await fs.open(absPath);
+    const stream = handle.createReadStream({ encoding: "utf-8" });
+    const rl = readline.createInterface({
+      input: stream,
+      crlfDelay: Infinity,
+    });
+    const selected: string[] = [];
+    let index = 0;
+    try {
+      for await (const line of rl) {
+        index += 1;
+        if (index < start) {
+          continue;
+        }
+        if (selected.length >= count) {
+          break;
+        }
+        selected.push(line);
+      }
+    } finally {
+      rl.close();
+      await handle.close();
+    }
+    return selected.slice(0, count).join("\n");
+  }
+
   private ensureDb(): SqliteDatabase {
     if (this.db) {
       return this.db;