unable to open two session at once

[scarf005]

2026-03-10.9.11.38.mov

Version

$ npm install -g @playwright/cli@latest
$ playwright-cli --version
1.59.0-alpha-1771104257000

env var

set -gx PLAYWRIGHT_MCP_BROWSER firefox
set -gx PLAYWRIGHT_MCP_ISOLATED false
set -gx PLAYWRIGHT_MCP_USER_DATA_DIR "$HOME/.cache/ms-playwright/profiles/work"

Reproduction

$ playwright-cli list
### Browsers
  (no browsers)
$ playwright-cli -s a open https://www.google.com/  --headed
### Browser `a` opened with pid 27665.
- a:
  - browser-type: firefox
  - user-data-dir: /Users/nemo/.cache/ms-playwright/profiles/work
  - headed: true
---
### Ran Playwright code
```js
await page.goto('https://www.google.com/');
```
### Page
- Page URL: https://www.google.com/
- Page Title: Google
- Console: 1 errors, 9 warnings
### Snapshot
- [Snapshot](.playwright-cli/page-2026-03-09T01-05-57-464Z.yml)
### Events
- New console entries: .playwright-cli/console-2026-03-09T01-05-56-639Z.log#L1-L11
$ playwright-cli -s b open https://www.google.com/  --headed
browserType.launchPersistentContext: Failed to launch the browser process.
Browser logs:

<launching> ~/Library/Caches/ms-playwright/firefox-1509/firefox/Nightly.app/Contents/MacOS/firefox -no-remote -wait-for-browser -foreground -profile ~/.cache/ms-playwright/profiles/work -juggler-pipe about:blank
<launched> pid=27870
[pid=27870] <process did exit: exitCode=0, signal=null>
[pid=27870] starting temporary directories cleanup
Call log:
  - <launching> ~/Library/Caches/ms-playwright/firefox-1509/firefox/Nightly.app/Contents/MacOS/firefox -no-remote -wait-for-browser -foreground -profile ~/.cache/ms-playwright/profiles/work -juggler-pipe about:blank
  - <launched> pid=27870
  - [pid=27870] <process did exit: exitCode=0, signal=null>
  - [pid=27870] starting temporary directories cleanup
  - [pid=27870] <gracefully close start>
  - [pid=27870] <kill>
  - [pid=27870] <skipped force kill spawnedProcess.killed=false processClosed=true>
  - [pid=27870] finished temporary directories cleanup
  - [pid=27870] <gracefully close end>

second session is always empty.

[pavelfeldman]

Everything looks good in this output.

[scarf005]

Everything looks good in this output.

browserType.launchPersistentContext: Failed to launch the browser process.

I've attached screen recording; new sessions always fail to work.

[pavelfeldman]

You are not showing a default config that points both sessions to the same profile dir. Can't do that.

[m13v]

we hit this exact problem running multiple AI agents that each need their own browser. the profile directory lock is the core issue - Chromium and Firefox both enforce single-process-per-profile.

what we built to solve it: a file-based locking system that coordinates browser access across multiple concurrent agents. each agent acquires a lock before launching playwright, and releases it when done. if the lock is held, the agent waits with a configurable timeout.

for true parallelism (multiple agents browsing simultaneously), separate user-data-dirs is the way to go. we create a temp directory per agent session and pass it via --user-data-dir. the downside is you lose cookies/sessions between runs, but for automation tasks that's usually fine since you re-authenticate anyway.

another approach we tested: one persistent browser instance shared via CDP (Chrome DevTools Protocol). multiple agents connect to the same browser but open separate tabs. this avoids the profile lock entirely since there's only one browser process. the tradeoff is that agents can see each other's tabs and there's no cookie isolation.

for the cleanest multi-agent setup: launch one browser per agent with isolated profiles, coordinate access to sites that detect concurrent logins (like Reddit, which rate-limits per account).

[m13v]

our multi-agent browser locking system is open source: https://github.com/m13v/browser-lock - hook-based locking for concurrent Claude Code agents sharing Playwright MCP. handles the profile directory conflict with serialized access.