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Assortment of various flakiness conditions found running tests in a loop
locally:
This PR introduces a comprehensive set of hermetic retry layers and
aggressive
timeout handlers across the test suite to insulate it from random
Chromium
startup hangs, CDP deadlocks, and Puppeteer lifecycle flakes. It
guarantees that
temporary browser infrastructure failures are automatically retried
without
failing the CI, while actual code assertion failures still fail fast.
### Test Harness & Retry Improvements
• tests/utils.ts: Rewrote withBrowser to include a 30-second internal
timeout and
a 3-attempt retry loop. If Chromium locks up or disconnects (Target
closed /
socket hang up), the browser is forcibly evicted (via SIGKILL if
browser.close()
hangs) and the test setup is cleanly retried.
• tests/index.test.ts: Wrapped withClient (used by E2E tests) in a
3-attempt
retry loop to handle the daemon/Chromium hanging during launch and
triggering the
60-second MCP client timeout.
• tests/browser.test.ts: Added a safeClose helper that imposes a
2-second timeout
before SIGKILLing browsers, and wrapped raw Puppeteer tests in
runWithRetry to
handle startup hangs.
• tests/shutdown.test.ts: Added a setupServerWithRetry helper to prevent
random
60s RPC timeouts when the server's Chrome instance hangs during boot.
### Flaky Operations & Navigation Fixes
• src/tools/performance.ts & tests/tools/performance.test.ts: Replaced
the
notoriously flaky waitUntil: ['networkidle0'] with 'load' when
navigating to
about:blank in performance_start_trace. This prevents random 10-second
Navigation
timeout exceeded errors. Also stubbed goto in the associated unit tests
for
better hermeticity.
• src/McpContext.ts: Wrapped browser.installExtension() with a 15-second
timeout
to prevent deadlocks when an extension fails to load.
• tests/tools/extensions.test.ts: Removed flaky headless UI navigations
to
chrome://extensions in favor of using the context.listExtensions() API.
• tests/tools/pages.test.js.snapshot: Synced test snapshots to reflect
updated
environment baselines.
## Support for Network Blocklists and Allowlists
(`--blocked-url-pattern` & `--allowed-url-pattern` arguments)
This PR adds support for CLI options to restrict network access in the
browser session via URL patterns.
### Key Features & How It Works
- **Pattern Matching:** Utilizes the [URLPattern
Standard](https://urlpattern.spec.whatwg.org/) for pattern matching.
- **Target Detachment:** Silently detaches from targets (pages/tabs)
whose URLs match blocked patterns (or do not match allowed patterns)
upon connection.
- **Runtime Blocking:** Prevents navigations and blocks runtime requests
(such as fetch/XHR and subresources) if they violate the pattern rules.
- **Mutual Exclusivity:** `--blocked-url-pattern` and
`--allowed-url-pattern` conflict with each other and cannot be
configured simultaneously.
- **Browser Requirements:**
- **`--allowed-url-pattern`**: Requires **Chrome 149+**.
- **`--blocked-url-pattern`**: Works on Chrome versions older than 149,
but **Chrome 149+ is highly recommended**.
### Important Limitations & Side Effects
- **Network Emulation/Throttling Conflict:** Network throttling is
disabled when a network blocklist/allowlist is configured, to avoid
conflicting with Puppeteer's underlying blocking mechanisms.
- Using the `emulate` tool to modify `networkConditions` (e.g. setting
to `Offline`) will throw an error: *`Network throttling is not supported
when network blocking (allowlist/blocklist) is configured.`*
- Other emulation settings (e.g., `cpuThrottlingRate`, `geolocation`,
`viewport`) are unaffected and remain fully functional.
---
### Configuration Examples
#### 1. Blocking specific domains or endpoints (Blocklist)
Add the `--blocked-url-pattern` options to the `args` list in your MCP
settings file:
```json
{
"mcpServers": {
"chrome-devtools": {
"command": "npx",
"args": [
"chrome-devtools-mcp@latest",
"--blocked-url-pattern=*://*.blocked-example.com/*",
"--blocked-url-pattern=*://*.another-blocked-example.com/*"
]
}
}
}
```
#### 2. Restricting access to authorized domains (Allowlist)
Add the `--allowed-url-pattern` options to restrict the browser to
permitted hosts (requires Chrome 149+):
```json
{
"mcpServers": {
"chrome-devtools": {
"command": "npx",
"args": [
"chrome-devtools-mcp@latest",
"--allowed-url-pattern=https://*.allowed-example.com/*",
"--allowed-url-pattern=https://*.another-allowed-example.com/*"
]
}
}
}
```
---------
Co-authored-by: Natallia Harshunova <nharshunova@chromium.org>
Co-authored-by: Alex Rudenko <alexrudenko@chromium.org>
Related Issue -
https://github.com/ChromeDevTools/chrome-devtools-mcp/issues/430
### Description
When Chrome is launched via Puppeteer, it automatically adds a set of
default flags like `--enable-automation --disable-extensions
--disable-component-extensions-with-background-pages.`
Currently, there is no way to opt out of these defaults, which makes
certain use cases difficult or impossible to support. this PR adds a way
to selectively ignore specific default Chrome launch flags applied by
Puppeteer using its
[ignoreDefaultArgs](https://pptr.dev/api/puppeteer.launchoptions#ignoredefaultargs)
property.
```json
{
"name": "chrome-devtools-mcp",
"version": "latest",
"mcpServers": {
"chrome-devtools": {
"command": "npx",
"args": [
"chrome-devtools-mcp@latest",
"--ignore-default-chrome-arg='--enable-automation'",
"--ignore-default-chrome-arg='--disable-extensions'"
]
}
}
}
```
**Feedback appreciated** @OrKoN
This PR integrates `--user-data-dir` with the `--auto-connect` feature.
If `--user-data-dir` is provided as well `--auto-connect`, the specified
dir is used to locate a running browser server.
This PR prevents license notices being dropped when creating package for
publication.
This can happen when first import in the file is type-only import that
gets removed during build. When there is no empty line between the
license block comment and such import, the comment is treated as related
to the import and gets removed alongside it.
Adding an empty line between copyright notice and the import fixes the
issue.
Co-authored-by: Piotr Paulski <piotrpaulski@chromium.org>
Alex Rudenko