fix(logging): cap file logs with configurable maxFileBytes

Co-authored-by: Xinhua Gu <562450+xinhuagu@users.noreply.github.com>

src/logging/log-file-size-cap.test.ts

@@ -0,0 +1,68 @@
+import crypto from "node:crypto";
+import fs from "node:fs";
+import os from "node:os";
+import path from "node:path";
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+import {
+  getLogger,
+  getResolvedLoggerSettings,
+  resetLogger,
+  setLoggerOverride,
+} from "../logging.js";
+
+const DEFAULT_MAX_FILE_BYTES = 500 * 1024 * 1024;
+
+describe("log file size cap", () => {
+  let logPath = "";
+
+  beforeEach(() => {
+    logPath = path.join(os.tmpdir(), `openclaw-log-cap-${crypto.randomUUID()}.log`);
+    resetLogger();
+    setLoggerOverride(null);
+  });
+
+  afterEach(() => {
+    resetLogger();
+    setLoggerOverride(null);
+    vi.restoreAllMocks();
+    try {
+      fs.rmSync(logPath, { force: true });
+    } catch {
+      // ignore cleanup errors
+    }
+  });
+
+  it("defaults maxFileBytes to 500 MB when unset", () => {
+    setLoggerOverride({ level: "info", file: logPath });
+    expect(getResolvedLoggerSettings().maxFileBytes).toBe(DEFAULT_MAX_FILE_BYTES);
+  });
+
+  it("uses configured maxFileBytes", () => {
+    setLoggerOverride({ level: "info", file: logPath, maxFileBytes: 2048 });
+    expect(getResolvedLoggerSettings().maxFileBytes).toBe(2048);
+  });
+
+  it("suppresses file writes after cap is reached and warns once", () => {
+    const stderrSpy = vi.spyOn(process.stderr, "write").mockImplementation(
+      () => true as unknown as ReturnType<typeof process.stderr.write>, // preserve stream contract in test spy
+    );
+    setLoggerOverride({ level: "info", file: logPath, maxFileBytes: 1024 });
+    const logger = getLogger();
+
+    for (let i = 0; i < 200; i++) {
+      logger.error(`network-failure-${i}-${"x".repeat(80)}`);
+    }
+    const sizeAfterCap = fs.statSync(logPath).size;
+    for (let i = 0; i < 20; i++) {
+      logger.error(`post-cap-${i}-${"y".repeat(80)}`);
+    }
+    const sizeAfterExtraLogs = fs.statSync(logPath).size;
+
+    expect(sizeAfterExtraLogs).toBe(sizeAfterCap);
+    expect(sizeAfterCap).toBeLessThanOrEqual(1024 + 512);
+    const capWarnings = stderrSpy.mock.calls
+      .map(([firstArg]) => String(firstArg))
+      .filter((line) => line.includes("log file size cap reached"));
+    expect(capWarnings).toHaveLength(1);
+  });
+});