Bug : v3Logger fallback bypasses verbose level filtering, causing debug logs even with verbose: 0

[sashank-zluri]

Bug Description

When using Stagehand V3 with verbose: 0, debug-level logs like DEBUG: xpath main-world are still printed to the console. The v3Logger function has a fallback path that bypasses verbose level filtering.

Steps to Reproduce

import { Stagehand } from "@browserbasehq/stagehand";

const stagehand = new Stagehand({
  env: "LOCAL",
  verbose: 0,  // Errors only
  disablePino: true,
});

await stagehand.init();
const page = stagehand.context.pages()[0];
await page.goto("https://example.com");
// Use any locator/xpath operation
await page.locator("//div").first();

Expected Behavior

With verbose: 0, only error-level logs should be printed. Debug logs should be suppressed.

Actual Behavior

Debug logs are printed:

[2026-01-02T13:16:37.661Z] DEBUG: xpath main-world
    frameId: F6611B8D017F9801E6E83A956066C58D
    xp: /html/body[1]/div[1]/div[3]/main[1]/div[1]/div[2]/form[1]/div[1]/input[2]
    ctxId: 3

Root Cause Analysis

In lib/v3/logger.ts, the v3Logger function has two code paths:

1. Instance logger path (lines ~500-510): Calls the registered instance logger which respects verbose level
2. Fallback path (lines ~514-540): Directly logs to console without checking verbose level

The fallback path logs to console regardless of configured verbosity:

if (lvl === 2) {
  (console.debug ?? console.log)(output);  // No verbose check!
}

Meanwhile, StagehandLogger.log() correctly checks: if (logLine.level > this.verbose) return;

Suggested Fix

The fallback path in v3Logger should either:

1. Not log at all when no instance logger is registered (let it be silent)
2. Or check against a global/default verbose level before logging

Environment

• Stagehand version: latest (V3)
• Node.js version: 22
• OS: Alpine Linux (Docker) / macOS